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Author name code: lamy
ADS astronomy entries on 2022-09-14
author:Lamy, P.L.
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Title: Linking Small-scale Solar Wind Properties with Large-scale
Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar
Orbiter Observations
Authors: Telloni, Daniele; Zank, Gary P.; Sorriso-Valvo, Luca;
D'Amicis, Raffaella; Panasenco, Olga; Susino, Roberto; Bruno, Roberto;
Perrone, Denise; Adhikari, Laxman; Liang, Haoming; Nakanotani, Masaru;
Zhao, Lingling; Hadid, Lina Z.; Sánchez-Cano, Beatriz; Verscharen,
Daniel; Velli, Marco; Grimani, Catia; Marino, Raffaele; Carbone,
Francesco; Mancuso, Salvatore; Biondo, Ruggero; Pagano, Paolo; Reale,
Fabio; Bale, Stuart D.; Kasper, Justin C.; Case, Anthony W.; de Wit,
Thierry Dudok; Goetz, Keith; Harvey, Peter R.; Korreck, Kelly E.;
Larson, Davin; Livi, Roberto; MacDowall, Robert J.; Malaspina, David
M.; Pulupa, Marc; Stevens, Michael L.; Whittlesey, Phyllis; Romoli,
Marco; Andretta, Vincenzo; Deppo, Vania Da; Fineschi, Silvano; Heinzel,
Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo;
Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca; Capobianco,
Gerardo; Capuano, Giuseppe E.; Casini, Chiara; Casti, Marta; Chioetto,
Paolo; Corso, Alain J.; Leo, Yara De; Fabi, Michele; Frassati,
Federica; Frassetto, Fabio; Giordano, Silvio; Guglielmino, Salvo L.;
Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli,
Enrico; Massone, Giuseppe; Messerotti, Mauro; Pancrazzi, Maurizio;
Pelizzo, Maria G.; Romano, Paolo; Sasso, Clementina; Schühle, Udo;
Slemer, Alessandra; Straus, Thomas; Uslenghi, Michela; Volpicelli,
Cosimo A.; Zangrilli, Luca; Zuppella, Paola; Abbo, Lucia; Auchère,
Frédéric; Cuadrado, Regina Aznar; Berlicki, Arkadiusz; Ciaravella,
Angela; Lamy, Philippe; Lanzafame, Alessandro; Malvezzi, Marco;
Nicolosi, Piergiorgio; Nisticò, Giuseppe; Peter, Hardi; Solanki,
Sami K.; Strachan, Leonard; Tsinganos, Kanaris; Ventura, Rita; Vial,
Jean-Claude; Woch, Joachim; Zimbardo, Gaetano
2022ApJ...935..112T Altcode:
The solar wind measured in situ by Parker Solar Probe in the very
inner heliosphere is studied in combination with the remote-sensing
observation of the coronal source region provided by the METIS
coronagraph aboard Solar Orbiter. The coronal outflows observed near
the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and
6.3 R <SUB>⊙</SUB> above the eastern solar limb, can be associated
with the streams sampled by PSP at 0.11 and 0.26 au from the Sun,
in two time intervals almost 5 days apart. The two plasma flows
come from two distinct source regions, characterized by different
magnetic field polarity and intensity at the coronal base. It follows
that both the global and local properties of the two streams are
different. Specifically, the solar wind emanating from the stronger
magnetic field region has a lower bulk flux density, as expected,
and is in a state of well-developed Alfvénic turbulence, with low
intermittency. This is interpreted in terms of slab turbulence in the
context of nearly incompressible magnetohydrodynamics. Conversely,
the highly intermittent and poorly developed turbulent behavior of the
solar wind from the weaker magnetic field region is presumably due to
large magnetic deflections most likely attributed to the presence of
switchbacks of interchange reconnection origin.
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Title: Science with the ASPIICS coronagraph onboard PROBA-3
Authors: Gunár, Stanislav; Fineschi, Silvano; Inhester, Bernd;
Zhukov, Andrei; Mierla, Marilena; Tsinganos, Kanaris; Lamy, Philippe;
Rudawy, Pawel
2022cosp...44.1326G Altcode:
The giant distributed coronagraph ASPIICS onboard the formation-flying
mission PROBA-3 of ESA will investigate hitherto practically
unexplored inner depths of the solar corona. This region lies above
the reach of disk imagers such as SDO and below the inner limit of
other coronagraphs. Although difficult to observe, the inner corona
is a place of great interest. This is where the fast solar wind gets
accelerated to supersonic velocities and where CMEs also reach their
maximum accelerations. It is also the place where the transition between
the regions of the closed and open magnetic field often happens and
the slow solar wind originates. Thanks to its field of view (2048 x
2048 pixels) reaching from 1.098 to 3 Rsun, good spatial resolution
(2.8 arcsec per pixel) and minimized straylight, ASPIICS will be able
to follow the connectivity of magnetic structures in corona down to the
solar surface. When coupled with regular (every week) long duration
(up to 6 hours) observations, it will allow us to comprehensively
compare and validate the MHD models of the large-scale coronal magnetic
field configuration and its evolution. The inner field-of-view limit
reaching very close to the solar surface will also enable us to study
the onset and early evolution of CMEs or to follow erupting prominences
beyond the reaches of the disk imagers. Thanks to the high cadence
(up to 2 seconds) we can start to investigate the manifestation of
small-scale solar dynamic processes within the inner corona. Moreover,
together with the DARA instrument measuring the total solar irradiance
onboard the occulting spacecraft of PROBA-3, ASPIICS will help us to
understand the partition of the magnetic free energy into the radiative
energy and the kinetic energy during solar eruptions. The pursuit of
these science goals will happen in coordination with Solar Orbiter,
Parker Solar Probe, Aditya-L1, and ASO-S. The synergies stemming from
these collaborations are promising to lead us into a golden age of
space coronagraphy.
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Title: Polarimetric Studies of a Fast Coronal Mass Ejection
Authors: Mierla, Marilena; Inhester, Bernd; Zhukov, Andrei N.; Shestov,
Sergei V.; Bemporad, Alessandro; Lamy, Philippe; Koutchmy, Serge
2022SoPh..297...78M Altcode: 2022arXiv220604411M
In this work we performed a polarimetric study of a fast and wide
coronal mass ejection (CME) observed on 12 July 2012 by the COR1 and
COR2 instruments onboard the Solar TErrestrial RElations Observatory
(STEREO) mission. The CME source region was an X1.4 flare located at
approximately S15W01 on the solar disk, as observed from the Earth's
perspective. The position of the CME as derived from the 3D Graduated
Cylindrical Shell (GCS) reconstruction method was at around S18W00
at 2.5 solar radii and S07W00 at 5.7 solar radii, meaning that the
CME was deflected towards the Equator while propagating outward in
the corona. The projected speed of the leading edge of the CME also
evolved from around 200 km s<SUP>−1</SUP> in the lower corona to
around 1000 km s<SUP>−1</SUP> in the COR2 field of view. The degree
of polarisation of the CME is around 65% but it can go as high as 80%
in some CME regions. The CME showed deviation of the polarisation
angle from the tangential in the range of 10 - 15<SUP>∘</SUP> (or
more). Our analysis showed that this is mostly due to the fact that the
sequence of three polarised images from where the polarised parameters
are derived is not taken simultaneously, but at a difference of a few
seconds in time. In this interval of time, the CME moves by at least
two pixels in the FOV of the instruments and this displacement results
in uncertainties in the polarisation parameters (degree of polarisation,
polarisation angle, etc.). We propose some steps forward to improve the
derivation of the polarisation. This study is important for analysing
the future data from instruments with polarisation capabilities.
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Title: Three-Dimensional Structure of the Corona During WHPI Campaign
Rotations CR-2219 and CR-2223
Authors: Lloveras, D. G.; Vásquez, A. M.; Nuevo, F. A.; Frazin, R. A.;
Manchester, W.; Sachdeva, N.; Van der Holst, B.; Lamy, P.; Gilardy, H.
2022JGRA..12730406L Altcode:
Differential emission measure tomography (DEMT) and white light
(WL) tomography were applied to study the three-dimensional (3D)
structure of the global solar corona for two Whole Heliosphere
and Planetary Interactions campaign periods, Carrington rotations
2219 and 2223. With DEMT, Solar Dynamics Observatory/Atmospheric
Imaging Assembly images were used to reconstruct the 3D coronal
electron density and temperature in the range of heliocentric
distance 1.02-1.25 R<SUB>⊙</SUB>. With WL tomography, Solar and
Heliospheric Observatory/Large Angle and Spectrometric COronagraph-C2
images were used to reconstruct the 3D electron density in the range
of heliocentric distance 2.5-6.0 R<SUB>⊙</SUB>. The two periods
were also simulated with the 3D-magneto-hydrodynamic Alfvén Wave
Solar Model (AWSoM), and its results compared in detail with the
reconstructions. The DEMT analysis reveals a 20% less dense and 20%
hotter corona than for rotations corresponding to the solar cycle
23/24 deep minimum. The electron density and temperature of the AWSoM
model agree with DEMT results within 10% and 20%, respectively, while
its electron density overestimates results of WL tomography up to
75%. The slow (fast) component of the terminal wind speed of the model
is found to be associated with field lines characterized by larger
(smaller) values of the tomographic density and temperature at the
coronal base. DEMT reconstructions reveal the coronal plasma to be
ubiquitously characterized by temperature variability of up to ≈45%
over spatial scales of order ∼10<SUP>4</SUP> km. Taking into account
this level of fine-structure by global models may be consequential
for their predictions on wave propagation in the corona.
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Title: M-type (22) Kalliope: A tiny Mercury
Authors: Ferrais, M.; Jorda, L.; Vernazza, P.; Carry, B.; Brož, M.;
Rambaux, N.; Hanuš, J.; Dudziński, G.; Bartczak, P.; Vachier, F.;
Aristidi, E.; Beck, P.; Marchis, F.; Marsset, M.; Viikinkoski, M.;
Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.;
Burbine, T. H.; Dyar, M. D.; Bendjoya, P.; Benkhaldoun, Z.; Berthier,
J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Ďurech,
J.; Fauvaud, S.; Grice, J.; Jehin, E.; Kaasalainen, M.; Kryszczynska,
A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel,
P.; Prieur, J. -L.; Reddy, V.; Rivet, J. -P.; Santana-Ros, T.; Scardia,
M.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B.
2022A&A...662A..71F Altcode:
Context. Asteroid (22) Kalliope is the second largest M-type asteroid
in the main belt and is orbited by a satellite, Linus. Whereas the
mass of Kalliope is already well constrained thanks to the presence of
a moon, its volume is still poorly known, leading to uncertainties on
its bulk density and internal structure. <BR /> Aims: We aim to refine
the shape of (22) Kalliope and thus its diameter and bulk density,
as well as the orbit of its moon to better constrain its mass,
hence density and internal structure. <BR /> Methods: We acquired
disk-resolved observations of (22) Kalliope using the VLT/SPHERE/ZIMPOL
instrument to reconstruct its three-dimensional (3D) shape using three
different modeling techniques. These images were also used together
with new speckle observations at the C2PU/PISCO instrument as well
as archival images from other large ground-based telescopes to refine
the orbit of Linus. <BR /> Results: The volume of (22) Kalliope given
by the shape models, corresponding to D = 150 ± 5 km, and the mass
constrained by its satellite's orbit yield a density of ρ = 4.40
± 0.46 g cm<SUP>−3</SUP>. This high density potentially makes
(22) Kalliope the densest known small body in the Solar System. A
macroporosity in the 10-25% range (as expected for this mass and
size), implies a grain density in the 4.8-5.9 g cm<SUP>−3</SUP>
range. Kalliope's high bulk density, along with its silicate-rich
surface implied by its low radar albedo, implies a differentiated
interior with metal contributing to most of the mass of the body. <BR
/> Conclusions: Kalliope's high metal content (40-60%) along with its
metal-poor mantle makes it the smallest known Mercury-like body. A
large impact at the origin of the formation of the moon Linus is
likely the cause of its high metal content and density. <P />Reduced
images are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/662/A71">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/662/A71</A>
<P />Based on observations made with ESO Telescopes at the Paranal
Observatory under program ID 199.C-0074 (PI: P. Vernazza).
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Title: The State of the White-Light Corona over the Minimum and
Ascending Phases of Solar Cycle 25 -- Comparison with Past Cycles
Authors: Lamy, Philippe; Gilardy, Hugo
2022arXiv220506462L Altcode:
We report on the state of the corona over the minimum and ascending
phases of Solar Cycle (SC) 25 on the basis of the temporal evolutions of
its radiance and of the properties of coronal mass ejections (CMEs) as
determined from white-light observations performed by the SOHO/LASCO-C2
coronagraph. These evolutions are further compared with those determined
during the past two SC. The integrated radiance of the K-corona and
the occurrence rate of CMEs closely track the indices/proxies of solar
activity, prominently the total magnetic field for the radiance and
the radio flux for the CMEs, all undergoing a steep increase during the
ascending phase of SC 25. This increase is much steeper than anticipated
on the basis of the predicted quasi similarity between SC 25 and 24,
and is confirmed by the recent evolution of the sunspot number. The
radiance reached the same base level during the minima of SC 24 and
25, but the latitudinal extent of the streamer belt differed, being
flatter during the latter minimum and in fact more similar to that of
the minimum of SC 23. Phasing the descending branches of SC 23 and 24
led to a duration of SC 24 of 11.0 years, similar to that given by the
sunspot number. In contrast, the base level of the occurrence rate of
CMEs during the minimum of SC 25 was significantly larger than during
the two previous minima. The southern hemisphere is conspicuously more
active than the northern one in agreement with several predictions
and the current evolution of the hemispheric sunspot numbers. The mean
apparent width of CMEs and the number of halo CMEs remains at relatively
large, constant levels throughout the early phase of SC 25 implying the
persistence of weak total pressure in the heliosphere. These results and
the perspective of a corona more active than anticipated are extremely
promising for the forthcoming observations by Solar Orbiter and Parker
Solar Probe.
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Title: VizieR Online Data Catalog: (22) Kalliope SPHERE images and
shape models (Ferrais+, 2022)
Authors: Ferrais, M.; Jorda, L.; Vernazza, P.; Carry, B.; Broz, M.;
Rambaux, N.; Hanus, J.; Dudzinski, G.; Bartczak, P.; Vachier, F.;
Aristidi, E.; Beck, P.; Marchis, F.; Marsset, M.; Viikinkoski, M.;
Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.;
Burbine, T. H.; Dyar, M. D.; Bendjoya, P.; Benkhaldoun, Z.; Berthier,
J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Durech,
J.; Fauvaud, S.; Grice, J.; Jehin, E.; Kaasalainen, M.; Kryszczynska,
A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel,
P.; Prieur, J. -L.; Reddy, V.; Rivet, J. -P.; Santana-Ros, T.; Scardia,
M.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B.
2022yCat..36620071F Altcode:
We obtained 35 images of Kalliope at 7 epochs in 2018 and 2019 using
VLT/SPHERE/ZIMPOL. All images were reduced following the procedure
described in Vernazza et al. (2018A&A...618A.154V). <P />objects:
-------------------------------------------------------------------
Planet Name H Diam i e a mag km deg AU
-------------------------------------------------------------------
22 Kalliope 6.53 150 13.700494 0.09838130 2.91020240
-------------------------------------------------------------------
<P />(10 data files).
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Title: Observation of the Solar F-corona from Space
Authors: Lamy, Philippe; Gilardy, Hugo; Llebaria, Antoine
2022arXiv220211533L Altcode:
We present a review of the observations of the solar F-corona from
space with a special emphasis of the 25 years of continuous monitoring
achieved by the LASCO-C2 and C3 coronagraphs. Our work includes images
obtained by the navigation cameras of the Clementine spacecraft, the
SECCHI/HI-1A heliospheric imager onboard STEREO-A, and the Wide Field
Imager for Solar Probe onboard the Parker Solar Probe. The connection
to the zodiacal light is considered based on ground- and space-based
observations, prominently from the past Helios, IRAS, COBE, and IRAKI
missions. The characteristic radiance profiles along the equatorial and
polar directions follow power laws in the 5°-50° range of elongation,
with constant power exponents of -2.33 and -2.55. Both profiles connect
extremely well to the corresponding standard profiles of the zodiacal
light. The LASCO equatorial profile exhibits a shoulder implying a 17%
decrease of the radiance within 10Rsun that may be explained by the
disappearance of organic materials within 0.3 AU. LASCO detected for
the first time a secular variation of the F-corona, an increase at
a rate of 0.46% per year of the integrated radiance in the LASCO-C3
FoV. This is likely the first observational evidence of the role
of collisions in the inner zodiacal cloud. A composite of C2 and C3
images produced the LASCO reference map of the radiance of the F-corona
from 2 to 30Rsun and, by combining with ground-based measurements, the
LASCO extended map from 1 to 6 Rsun. The plane of symmetry of the inner
zodiacal cloud is strongly warped, its inclination increasing towards
the planes of the inner planets and ultimately the solar equator. In
contrast, its longitude of ascending node is found to be constant and
equal to 87.6°. LASCO did not detect any small scale structures such
as putative rings occasionally reported during solar eclipses.
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Title: The first coronal mass ejection observed in both visible-light
and UV H I Ly-α channels of the Metis coronagraph on board Solar
Orbiter
Authors: Andretta, V.; Bemporad, A.; De Leo, Y.; Jerse, G.; Landini,
F.; Mierla, M.; Naletto, G.; Romoli, M.; Sasso, C.; Slemer, A.;
Spadaro, D.; Susino, R.; Talpeanu, D. -C.; Telloni, D.; Teriaca, L.;
Uslenghi, M.; Antonucci, E.; Auchère, F.; Berghmans, D.; Berlicki,
A.; Capobianco, G.; Capuano, G. E.; Casini, C.; Casti, M.; Chioetto,
P.; Da Deppo, V.; Fabi, M.; Fineschi, S.; Frassati, F.; Frassetto,
F.; Giordano, S.; Grimani, C.; Heinzel, P.; Liberatore, A.; Magli, E.;
Massone, G.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.;
Pelizzo, M. -G.; Romano, P.; Schühle, U.; Stangalini, M.; Straus,
Th.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Aznar
Cuadrado, R.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.;
Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter,
H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan,
L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.;
Woch, J.; Zimbardo, G.
2021A&A...656L..14A Altcode:
Context. The Metis coronagraph on board Solar Orbiter offers a new
view of coronal mass ejections (CMEs), observing them for the first
time with simultaneous images acquired with a broad-band filter in
the visible-light interval and with a narrow-band filter around the
H I Ly-α line at 121.567 nm, the so-called Metis UV channel. <BR />
Aims: We show the first Metis observations of a CME, obtained on 16
and 17 January 2021. The event was also observed by the EUI/FSI imager
on board Solar Orbiter, as well as by other space-based coronagraphs,
such as STEREO-A/COR2 and SOHO/LASCO/C2, whose images are combined here
with Metis data. <BR /> Methods: Different images are analysed here
to reconstruct the 3D orientation of the expanding CME flux rope using
the graduated cylindrical shell model. This also allows us to identify
the possible location of the source region. Measurements of the CME
kinematics allow us to quantify the expected Doppler dimming in the
Ly-α channel. <BR /> Results: Observations show that most CME features
seen in the visible-light images are also seen in the Ly-α images,
although some features in the latter channel appear more structured
than their visible-light counterparts. We estimated the expansion
velocity of this event to be below 140 km s<SUP>−1</SUP>. Hence,
these observations can be understood by assuming that Doppler dimming
effects do not strongly reduce the Ly-α emission from the CME. These
velocities are comparable with or smaller than the radial velocities
inferred from the same data in a similar coronal structure on the
east side of the Sun. <BR /> Conclusions: The first observations by
Metis of a CME demonstrate the capability of the instrument to provide
valuable and novel information on the structure and dynamics of these
coronal events. Considering also its diagnostics capabilities regarding
the conditions of the ambient corona, Metis promises to significantly
advance our knowledge of such phenomena. <P />Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202142407/olm">https://www.aanda.org</A>
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Title: First light observations of the solar wind in the outer corona
with the Metis coronagraph
Authors: Romoli, M.; Antonucci, E.; Andretta, V.; Capuano, G. E.; Da
Deppo, V.; De Leo, Y.; Downs, C.; Fineschi, S.; Heinzel, P.; Landini,
F.; Liberatore, A.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Sasso,
C.; Spadaro, D.; Susino, R.; Telloni, D.; Teriaca, L.; Uslenghi,
M.; Wang, Y. -M.; Bemporad, A.; Capobianco, G.; Casti, M.; Fabi, M.;
Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Jerse, G.;
Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Pelizzo, M. -G.;
Romano, P.; Schühle, U.; Slemer, A.; Stangalini, M.; Straus, T.;
Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Auchère,
F.; Aznar Cuadrado, R.; Berlicki, A.; Bruno, R.; Ciaravella, A.;
D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi,
P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.;
Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli,
M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G.
2021A&A...656A..32R Altcode: 2021arXiv210613344R
In this work, we present an investigation of the wind in the solar
corona that has been initiated by observations of the resonantly
scattered ultraviolet emission of the coronal plasma obtained with
UVCS-SOHO, designed to measure the wind outflow speed by applying
Doppler dimming diagnostics. Metis on Solar Orbiter complements the
UVCS spectroscopic observations that were performed during solar
activity cycle 23 by simultaneously imaging the polarized visible
light and the H I Lyman-α corona in order to obtain high spatial and
temporal resolution maps of the outward velocity of the continuously
expanding solar atmosphere. The Metis observations, taken on May 15,
2020, provide the first H I Lyman-α images of the extended corona
and the first instantaneous map of the speed of the coronal plasma
outflows during the minimum of solar activity and allow us to identify
the layer where the slow wind flow is observed. The polarized visible
light (580-640 nm) and the ultraviolet H I Lyα (121.6 nm) coronal
emissions, obtained with the two Metis channels, were combined in
order to measure the dimming of the UV emission relative to a static
corona. This effect is caused by the outward motion of the coronal
plasma along the direction of incidence of the chromospheric photons
on the coronal neutral hydrogen. The plasma outflow velocity was then
derived as a function of the measured Doppler dimming. The static
corona UV emission was simulated on the basis of the plasma electron
density inferred from the polarized visible light. This study leads
to the identification, in the velocity maps of the solar corona, of
the high-density layer about ±10° wide, centered on the extension
of a quiet equatorial streamer present at the east limb - the coronal
origin of the heliospheric current sheet - where the slowest wind
flows at about 160 ± 18 km s<SUP>−1</SUP> from 4 R<SUB>⊙</SUB>
to 6 R<SUB>⊙</SUB>. Beyond the boundaries of the high-density layer,
the wind velocity rapidly increases, marking the transition between
slow and fast wind in the corona.
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Title: Sample return of primitive matter from the outer Solar System
Authors: Vernazza, P.; Beck, P.; Ruesch, O.; Bischoff, A.; Bonal,
L.; Brennecka, G.; Brunetto, R.; Busemann, H.; Carter, J.; Carli, C.;
Cartier, C.; Ciarniello, M.; Debaille, V.; Delsanti, A.; D'Hendecourt,
L.; Füri, E.; Groussin, O.; Guilbert-Lepoutre, A.; Helbert, J.; Hoppe,
P.; Jehin, E.; Jorda, L.; King, A.; Kleine, T.; Lamy, P.; Lasue,
J.; Le Guillou, C.; Leroux, H.; Leya, I.; Magna, T.; Marrocchi, Y.;
Morlok, A.; Mousis, O.; Palomba, E.; Piani, L.; Quirico, E.; Remusat,
L.; Roskosz, M.; Rubin, M.; Russell, S.; Schönbächler, M.; Thomas,
N.; Villeneuve, J.; Vinogradoff, V.; Wurz, P.; Zanda, B.
2021ExA...tmp..128V Altcode:
The last thirty years of cosmochemistry and planetary science have shown
that one major Solar System reservoir is vastly undersampled in the
available suite of extra-terrestrial materials, namely small bodies that
formed in the outer Solar System (>10 AU). Because various dynamical
evolutionary processes have modified their initial orbits (e.g., giant
planet migration, resonances), these objects can be found today across
the entire Solar System as P/D near-Earth and main-belt asteroids,
Jupiter and Neptune Trojans, comets, Centaurs, and small (diameter
< 200 km) trans-Neptunian objects. This reservoir is of tremendous
interest, as it is recognized as the least processed since the dawn of
the Solar System and thus the closest to the starting materials from
which the Solar System formed. Some of the next major breakthroughs in
planetary science will come from studying outer Solar System samples
(volatiles and refractory constituents) in the laboratory. Yet, this
can only be achieved by an L-class mission that directly collects
and returns to Earth materials from this reservoir. It is thus not
surprising that two White Papers advocating a sample return mission of
a primitive Solar System small body (ideally a comet) were submitted to
ESA in response to its Voyage 2050 call for ideas for future L-class
missions in the 2035-2050 time frame. One of these two White Papers
is presented in this article.
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Title: VLT/SPHERE imaging survey of the largest main-belt asteroids:
Final results and synthesis
Authors: Vernazza, P.; Ferrais, M.; Jorda, L.; Hanuš, J.; Carry,
B.; Marsset, M.; Brož, M.; Fetick, R.; Viikinkoski, M.; Marchis,
F.; Vachier, F.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca,
E.; Rambaux, N.; Neveu, M.; Bartczak, P.; Dudziński, G.; Jehin, E.;
Beck, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.;
Dumas, C.; Ďurech, J.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.;
Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel,
P.; Santana-Ros, T.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B.;
Antonini, P.; Audejean, M.; Aurard, P.; Behrend, R.; Benkhaldoun,
Z.; Bosch, J. M.; Chapman, A.; Dalmon, L.; Fauvaud, S.; Hamanowa,
Hiroko; Hamanowa, Hiromi; His, J.; Jones, A.; Kim, D. -H.; Kim,
M. -J.; Krajewski, J.; Labrevoir, O.; Leroy, A.; Livet, F.; Molina,
D.; Montaigut, R.; Oey, J.; Payre, N.; Reddy, V.; Sabin, P.; Sanchez,
A. G.; Socha, L.
2021A&A...654A..56V Altcode:
Context. Until recently, the 3D shape, and therefore density (when
combining the volume estimate with available mass estimates), and
surface topography of the vast majority of the largest (D ≥ 100 km)
main-belt asteroids have remained poorly constrained. The improved
capabilities of the SPHERE/ZIMPOL instrument have opened new doors
into ground-based asteroid exploration. <BR /> Aims: To constrain the
formation and evolution of a representative sample of large asteroids,
we conducted a high-angular-resolution imaging survey of 42 large
main-belt asteroids with VLT/SPHERE/ZIMPOL. Our asteroid sample
comprises 39 bodies with D ≥ 100 km and in particular most D ≥
200 km main-belt asteroids (20/23). Furthermore, it nicely reflects
the compositional diversity present in the main belt as the sampled
bodies belong to the following taxonomic classes: A, B, C, Ch/Cgh,
E/M/X, K, P/T, S, and V. <BR /> Methods: The SPHERE/ZIMPOL images
were first used to reconstruct the 3D shape of all targets with both
the ADAM and MPCD reconstruction methods. We subsequently performed
a detailed shape analysis and constrained the density of each target
using available mass estimates including our own mass estimates in
the case of multiple systems. <BR /> Results: The analysis of the
reconstructed shapes allowed us to identify two families of objects
as a function of their diameters, namely "spherical" and "elongated"
bodies. A difference in rotation period appears to be the main origin
of this bimodality. In addition, all but one object (216 Kleopatra)
are located along the Maclaurin sequence with large volatile-rich
bodies being the closest to the latter. Our results further reveal
that the primaries of most multiple systems possess a rotation period
of shorter than 6 h and an elongated shape (c∕a ≤ 0.65). Densities
in our sample range from ~1.3 g cm<SUP>−3</SUP> (87 Sylvia) to ~4.3 g
cm<SUP>−3</SUP> (22 Kalliope). Furthermore, the density distribution
appears to be strongly bimodal with volatile-poor (ρ ≥ 2.7 g
cm<SUP>−3</SUP>) and volatile-rich (ρ ≤ 2.2 g cm<SUP>−3</SUP>)
bodies. Finally, our survey along with previous observations provides
evidence in support of the possibility that some C-complex bodies
could be intrinsically related to IDP-like P- and D-type asteroids,
representing different layers of a same body (C: core; P/D: outer
shell). We therefore propose that P/ D-types and some C-types may have
the same origin in the primordial trans-Neptunian disk. <P />Tables
A.2 and A.3 are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/654/A56">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/654/A56</A>
<P />Based on observations made with ESO Telescopes at
the Paranal Observatory under programme ID 199.C-0074
(PI: P. Vernazza). <P />The reduced and deconvolved
images as well as the 3D shape models are available at <A
href="https://observations.lam.fr/astero/">https://observations.lam.fr/astero/</A>
---------------------------------------------------------
Title: (216) Kleopatra, a low density critically rotating M-type
asteroid
Authors: Marchis, F.; Jorda, L.; Vernazza, P.; Brož, M.; Hanuš, J.;
Ferrais, M.; Vachier, F.; Rambaux, N.; Marsset, M.; Viikinkoski, M.;
Jehin, E.; Benseguane, S.; Podlewska-Gaca, E.; Carry, B.; Drouard,
A.; Fauvaud, S.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.;
Dudziński, G.; Ďurech, J.; Castillo-Rogez, J.; Cipriani, F.; Colas,
F.; Fetick, R.; Fusco, T.; Grice, J.; Kryszczynska, A.; Lamy, P.;
Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros,
T.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B.
2021A&A...653A..57M Altcode: 2021arXiv210807207M
Context. The recent estimates of the 3D shape of the M/Xe-type
triple asteroid system (216) Kleopatra indicated a density of ~5 g
cm<SUP>−3</SUP>, which is by far the highest for a small Solar System
body. Such a high density implies a high metal content as well as a low
porosity which is not easy to reconcile with its peculiar "dumbbell"
shape. <BR /> Aims: Given the unprecedented angular resolution of the
VLT/SPHERE/ZIMPOL camera, here, we aim to constrain the mass (via the
characterization of the orbits of the moons) and the shape of (216)
Kleopatra with high accuracy, hence its density. <BR /> Methods:
We combined our new VLT/SPHERE observations of (216) Kleopatra
recorded during two apparitions in 2017 and 2018 with archival data
from the W. M. Keck Observatory, as well as lightcurve, occultation,
and delay-Doppler images, to derive a model of its 3D shape using two
different algorithms (ADAM, MPCD). Furthermore, an N-body dynamical
model allowed us to retrieve the orbital elements of the two moons
as explained in the accompanying paper. <BR /> Results: The shape
of (216) Kleopatra is very close to an equilibrium dumbbell figure
with two lobes and a thick neck. Its volume equivalent diameter
(118.75 ± 1.40) km and mass (2.97 ± 0.32) × 10<SUP>18</SUP> kg
(i.e., 56% lower than previously reported) imply a bulk density
of (3.38 ± 0.50) g cm<SUP>−3</SUP>. Such a low density for a
supposedly metal-rich body indicates a substantial porosity within
the primary. This porous structure along with its near equilibrium
shape is compatible with a formation scenario including a giant impact
followed by reaccumulation. (216) Kleopatra's current rotation period
and dumbbell shape imply that it is in a critically rotating state. The
low effective gravity along the equator of the body, together with
the equatorial orbits of the moons and possibly rubble-pile structure,
opens the possibility that the moons formed via mass shedding. <BR />
Conclusions: (216) Kleopatra is a puzzling multiple system due to the
unique characteristics of the primary. This system certainly deserves
particular attention in the future, with the Extremely Large Telescopes
and possibly a dedicated space mission, to decipher its entire formation
history. <P />Reduced images are only available at the CDS via anonymous
ftp to <A href="http://cdsarc.u-strasbg.fr">cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/653/A57">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/653/A57</A>
<P />Based on observations made with ESO Telescopes at the La Silla
Paranal Observatory under program 199.C-0074 (PI: Vernazza).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Largest main belt asteroids data
(Vernazza+, 2021)
Authors: Vernazza, P.; Ferrais, M.; Jorda, L.; Hanua, J.; Carry,
B.; Marsset, M.; Broz, M.; Fetick, R.; Viikinkoski, M.; Marchis,
F.; Vachier, F.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca,
E.; Rambaux, N.; Neveu, M.; Bartczak, P.; Dudzinski, G.; Jehin, E.;
Beck, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.;
Dumas, C.; Durech, J.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.;
Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel,
P.; Santana-Ros, T.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B.;
Antonini, P.; Audejean, M.; Aurard, P.; Behrend, R.; Benkhaldoun,
Z.; Bosch, J. M.; Chapman, A.; Dalmon, L.; Fauvaud, S.; Hamanowa,
Hiroko; Hamanowa, Hiromi; His, J.; Jones, A.; Kim, D. -H.; Kim,
M. -J.; Krajewski, J.; Labrevoir, O.; Leroy, A.; Livet, F.; Molina,
D.; Montaigut, R.; Oey, J.; Payre, N.; Reddy, V.; Sabin, P.; Sanchez,
A. G.; Socha, L.
2021yCat..36540056V Altcode:
The baseline observational strategy adopted for our large programme
has been to image each target with SPHERE/ZIMPOL (i) around opposition
to ensure an optimal spatial resolution (we restricted the observing
period so that its angular diameter remained greater than at least 85%
of that at opposition), (ii) every ~60° in rotation phase in order
to obtain a satisfactory surface coverage, and (iii) with seeing
conditions of better than 0.8" and an airmass of below 1.6 in order
to ensure great observing conditions and thus high-quality data. To
fulfil these criteria and given that large programmes have the highest
priority at ESO, we performed our large programme entirely in service
mode. We would like to stress that this strategy has been key to the
success of our programme. <P />(3 data files).
---------------------------------------------------------
Title: An advanced multipole model for (216) Kleopatra triple system
Authors: Brož, M.; Marchis, F.; Jorda, L.; Hanuš, J.; Vernazza, P.;
Ferrais, M.; Vachier, F.; Rambaux, N.; Marsset, M.; Viikinkoski, M.;
Jehin, E.; Benseguane, S.; Podlewska-Gaca, E.; Carry, B.; Drouard,
A.; Fauvaud, S.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.;
Dudziński, G.; Ďurech, J.; Castillo-Rogez, J.; Cipriani, F.; Colas,
F.; Fetick, R.; Fusco, T.; Grice, J.; Kryszczynska, A.; Lamy, P.;
Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros,
T.; Tanga, P.; Vigan, A.; Vokrouhlický, D.; Witasse, O.; Yang, B.
2021A&A...653A..56B Altcode: 2021arXiv210509134B
<BR /> Aims: To interpret adaptive-optics observations of (216)
Kleopatra, we need to describe an evolution of multiple moons orbiting
an extremely irregular body and include their mutual interactions. Such
orbits are generally non-Keplerian and orbital elements are not
constants. <BR /> Methods: Consequently, we used a modified N-body
integrator, which was significantly extended to include the multipole
expansion of the gravitational field up to the order ℓ = 10. Its
convergence was verified against the `brute-force' algorithm. We
computed the coefficients C<SUB>ℓm</SUB>, S<SUB>ℓm</SUB> for
Kleopatra's shape, assuming a constant bulk density. For Solar
System applications, it was also necessary to implement a variable
distance and geometry of observations. Our χ<SUP>2</SUP> metric then
accounts for the absolute astrometry, the relative astrometry (second
moon with respect to the first), angular velocities, and silhouettes,
constraining the pole orientation. This allowed us to derive the orbital
elements of Kleopatra's two moons. <BR /> Results: Using both archival
astrometric data and new VLT/SPHERE observations (ESO LP 199.C-0074),
we were able to identify the true periods of the moons, P<SUB>1</SUB> =
(1.822359 ± 0.004156) d, P<SUB>2</SUB> = (2.745820 ± 0.004820) d. They
orbit very close to the 3:2 mean-motion resonance, but their osculating
eccentricities are too small compared to other perturbations (multipole,
mutual), meaning that regular librations of the critical argument are
not present. The resulting mass of Kleopatra, m<SUB>1</SUB> = (1.49 ±
0.16) × 10<SUP>−12</SUP> M<SUB>⊙</SUB> or 2.97 × 10<SUP>18</SUP>
kg, is significantly lower than previously thought. An implication
explained in the accompanying paper is that (216) Kleopatra is a
critically rotating body. <P />Based on observations made with ESO
Telescopes at the La Silla Paranal Observatory under program 199.C-0074
(PI Vernazza).
---------------------------------------------------------
Title: VizieR Online Data Catalog: (216) Kleopatra images (Marchis+,
2021)
Authors: Marchis, F.; Jorda, L.; Vernazza, P.; Broz, M.; Hanus, J.;
Ferrais, M.; Vachier, F.; Rambaux, N.; Marsset, M.; Viikinkoski, M.;
Jehin, E.; Benseguane, S.; Podlewska-Gaca, E.; Carry, B.; Drouard,
A.; Fauvaud, S.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.;
Dudzinski, G.; Durech, J.; Castillo-Rogez, J.; Cipriani, F.; Colas,
F.; Fetick, R.; Fusco, T.; Grice, J.; Kryszczynska, A.; Lamy, P.;
Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros,
T.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B.
2021yCat..36530057M Altcode:
Deconvolved direct imaging observations of Kleopatra using
the MISTRAL algorithm and a generated PSF. <P />Those fits
files are direct images of (216) Kleopatra system. The reduced
images were further deconvolved with the Mistral algorithm
(Fusco et al., 2003, in Proc. SPIE, Vol. 4839, Adaptive Optical
System Technologies II, ed. P. L. Wizinowich & D. Bonaccini,
1065-1075), using a parametric point-spread function (Fetick et
al., 2019A&A...623A...6F, Cat. J/A+A/623/A6). <P />object.dat :
----------------------------------------------------------------------
Planet Name H Diam e i a mag km deg AU
----------------------------------------------------------------------
216 Kleopatra 7.15 135.1 0.25126552 13.116286 2.79243307 <P />(2
data files).
---------------------------------------------------------
Title: Evidence for differentiation of the most primitive small bodies
Authors: Carry, B.; Vernazza, P.; Vachier, F.; Neveu, M.; Berthier,
J.; Hanuš, J.; Ferrais, M.; Jorda, L.; Marsset, M.; Viikinkoski,
M.; Bartczak, P.; Behrend, R.; Benkhaldoun, Z.; Birlan, M.;
Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Drouard, A.; Dudziński,
G. P.; Desmars, J.; Dumas, C.; Ďurech, J.; Fetick, R.; Fusco, T.;
Grice, J.; Jehin, E.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.;
Marchis, F.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.;
Podlewska-Gaca, E.; Rambaux, N.; Santana-Ros, T.; Storrs, A.; Tanga,
P.; Vigan, A.; Warner, B.; Wieczorek, M.; Witasse, O.; Yang, B.
2021A&A...650A.129C Altcode: 2021arXiv210306349C
Context. Dynamical models of Solar System evolution have suggested
that the so-called P- and D-type volatile-rich asteroids formed in
the outer Solar System beyond Neptune's orbit and may be genetically
related to the Jupiter Trojans, comets, and small Kuiper belt objects
(KBOs). Indeed, the spectral properties of P- and D-type asteroids
resemble that of anhydrous cometary dust. <BR /> Aims: We aim to
gain insights into the above classes of bodies by characterizing the
internal structure of a large P- and D-type asteroid. <BR /> Methods:
We report high-angular-resolution imaging observations of the P-type
asteroid (87) Sylvia with the Very Large Telescope Spectro-Polarimetric
High-contrast Exoplanet REsearch (SPHERE) instrument. These images were
used to reconstruct the 3D shape of Sylvia. Our images together with
those obtained in the past with large ground-based telescopes were
used to study the dynamics of its two satellites. We also modeled
Sylvia's thermal evolution. <BR /> Results: The shape of Sylvia
appears flattened and elongated (a/b ~1.45; a/c ~1.84). We derive a
volume-equivalent diameter of 271 ± 5 km and a low density of 1378 ±
45 kg m<SUP>−3</SUP>. The two satellites orbit Sylvia on circular,
equatorial orbits. The oblateness of Sylvia should imply a detectable
nodal precession which contrasts with the fully-Keplerian dynamics of
its two satellites. This reveals an inhomogeneous internal structure,
suggesting that Sylvia is differentiated. <BR /> Conclusions: Sylvia's
low density and differentiated interior can be explained by partial
melting and mass redistribution through water percolation. The outer
shell should be composed of material similar to interplanetary dust
particles (IDPs) and the core should be similar to aqueously altered
IDPs or carbonaceous chondrite meteorites such as the Tagish Lake
meteorite. Numerical simulations of the thermal evolution of Sylvia
show that for a body of such a size, partial melting was unavoidable
due to the decay of long-lived radionuclides. In addition, we show
that bodies as small as 130-150 km in diameter should have followed a
similar thermal evolution, while smaller objects, such as comets and the
KBO Arrokoth, must have remained pristine, which is in agreement with
in situ observations of these bodies. NASA Lucy mission target (617)
Patroclus (diameter ≈140 km) may, however, be differentiated. <P
/>Tables A.1, B.1, C.1 and C.2 and the reduced and deconvolved
SPHERE images are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/650/A129">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/650/A129</A>
<P />Based on observations made with ESO telescopes
at the La Silla Paranal Observatory under program <A
href="http://archive.eso.org/wdb/wdb/eso/sched_rep_arc/query?progid=073.C-0851">073.C-0851</A>
(PI Merline), <A
href="http://archive.eso.org/wdb/wdb/eso/sched_rep_arc/query?progid=073.C-0062">073.C-0062</A>
(PI Marchis), <A
href="http://archive.eso.org/wdb/wdb/eso/sched_rep_arc/query?progid=085.C-0480">085.C-0480</A>
(PI Nitschelm), <A
href="http://archive.eso.org/wdb/wdb/eso/sched_rep_arc/query?progid=088.C-0528">088.C-0528</A>
(PI Rojo), <A
href="http://archive.eso.org/wdb/wdb/eso/sched_rep_arc/query?progid=199.C-0074">199.C-0074</A>
(PI Vernazza).
---------------------------------------------------------
Title: Response of the interplanetary hydrogen population to global
changes of solar activity: a quantitative analysis based on SOHO/SWAN
and SOHO/LASCO-C2 data comparison.
Authors: Koutroumpa, Dimitra; Quémerais, Eric; Conan, Lucile; Lamy,
Philippe; Ferron, Stéphane; Gilardy, Hugo
2021EGUGA..23.9506K Altcode:
For more than two decades the SOHO/SWAN instrument has been monitoring
the full-sky hydrogen backscattered Lyman-α emission, and the derived
three-dimensional solar wind proton flux. We present a comparison of the
time series of the latitude-integrated hydrogen ionization rates (β)
derived from the inversion of the SWAN full-sky maps with the integrated
coronal electron density derived from the inversion of SOHO/LASCO-C2
white light images. The analysis shows a variable time lag of the SWAN
β of a few Carrington rotations, correlated with the solar cycle phase
(larger delay during solar maxima compared to minima). This is a direct
consequence of the variation of the size of the hydrogen ionization
cavity and the time it takes for hydrogen atoms to propagate in the
inner heliosphere. This effect should be taken into account in studies
of the interstellar neutral populations in interplanetary space.
---------------------------------------------------------
Title: LASCO-C3 Observations of the K- and F-Coronae over 24 Years
(1996 - 2019): Photopolarimetry and Electron Density Distribution
Authors: Lamy, Philippe; Gilardy, Hugo; Llebaria, Antoine; Quémerais,
Eric; Ernandez, Fabrice
2021SoPh..296...76L Altcode:
We present the polarimetric analysis of the white-light images of the
corona obtained with the Large-Angle Spectrometric COronagraph LASCO-C3
onboard the Solar and Heliospheric Observatory (SOHO) from 1996 to
2019, leading to the separation of the K- and F-components and the
derivation of the electron-density distribution. The analysis makes
use of polarized sequences composed of three images obtained through
three polarizers oriented at +60<SUP>∘</SUP>, 0<SUP>∘</SUP>,
and −60<SUP>∘</SUP>, complemented by a neighboring unpolarized
image. However, the degradation of the 0<SUP>∘</SUP> polarizer
noticed in 1999 compelled us to reconstruct the corresponding images
from those obtained with the two other polarizers and the unpolarized
ones thereafter. The analysis closely follows the method developed for
LASCO-C2 (Lamy et al. in Solar Phys.295, 89, 2020) and implements the
formalism of Mueller, albeit with additional difficulties notably the
presence of a non-axially symmetric component of stray light. Critical
corrections were derived from a SOHO roll sequence and from consistency
criteria (e.g. the "tangential" direction of polarization). The
quasi-uninterrupted photopolarimetric analysis of the outer corona
over two complete Solar Cycles 23 and 24 was successfully achieved and
our final results encompass the characterization of its polarization,
of its polarized radiance, of the two-dimensional electron density,
and of the K-corona. Comparison between the C3 and C2 results in
the region where their fields of view overlap shows an overall
agreement. The C3 results are further in agreement with those of
eclipses and radio-ranging measurements to an elongation of ≈10
R<SUB>⊙</SUB> but tend to diverge further out. Although the coronal
polarization out to 20 R<SUB>⊙</SUB> is still highly correlated with
the temporal variation of the total magnetic field, this divergence
probably results from the increasing polarization of the F-corona with
increasing solar elongation.
---------------------------------------------------------
Title: Restoration of the K and F Components of the Solar Corona
from LASCO-C2 Images over 24 Years [1996 - 2019]
Authors: Llebaria, Antoine; Lamy, Philippe; Gilardy, Hugo; Boclet,
Brice; Loirat, Jean
2021SoPh..296...53L Altcode: 2020arXiv201112920L
We present a photometrically accurate restoration of the K- and
F-coronae from white-light images obtained over 24 years [1996 - 2019]
by the Large-Angle Spectrometric COronagraph (LASCO-C2) onboard the
Solar and Heliospheric Observatory (SOHO). The procedure starts with
the data set of unpolarized images of 512 × 512 pixels produced by
the polarimetric analysis of the routine C2 polarization sequences
(Lamy et al., Solar Phys.295, 89, 2020) in which the F-corona, the
instrumental stray light, and possible remnants of the K-corona due to
the imperfect polarimetric separation are entangled. Disentangling these
components requires a complex procedure organized in three stages,
each composed of several steps. Stage 1 establishes the distinct
variations of the radiance of these components with the Sun-SOHO
distance, and generate a new data set of median images calculated for
each Carrington rotation. Stage 2 achieves the restoration of a set of
36 stray-light images that account for the temporal variation of the
stray-light pattern, in particular those associated with the periodic
roll maneuvers of SOHO, which started in 2003. Stage 3 achieves the
restoration of the F-corona, and a time series of daily images is
generated. Combining these images with the set of stray-light images
allowed us to process the whole set of routine LASCO-C2 images of 1024
× 1024 pixels (approximately 626,000 images) and to produce calibrated,
high-resolution images of the K-corona. The two sets of images of the
K-corona, that produced by polarimetric separation of 512 × 512 pixels
images and that presently produced by subtraction, are in excellent
photometric agreement. We extend our past conclusions that the temporal
variation of the integrated radiance of the K-corona tracks the solar
activity over Solar Cycles 23 and 24, and that it is highly correlated
with the temporal variation of the total magnetic field. The behaviors
of the integrated radiance during the last few years of the declining
phases of Solar Cycles 23 and 24 are remarkably similar, reaching the
same base level and leading to a duration of 11.0 years for the latter
cycle, in agreement with that derived from sunspots.
---------------------------------------------------------
Title: VizieR Online Data Catalog: SPHERE (87) Sylvia images
(Carry+, 2021)
Authors: Carry, B.; Vernazza, P.; Vachier, F.; Neveu, M.; Berthier,
J.; Hanus, J.; Ferrais, M.; Jorda, L.; Marsset, M.; Viikinkoski, M.;
Bartczak, P.; Behrend, R.; Benkhaldoun, Z.; Birlan, M.; Castillo-Rogez,
J.; Cipriani, F.; Colas, F.; Drouard, A.; Dudzinski, G. P.; Desmars,
J.; Dumas, J.; Durech, C.; Fetick, R.; Fusco, T.; Grice, J.; Jehin, E.;
Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Marchis, F.; Marciniak,
A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Podlewska-Gaca, E.;
Rambaux, N.; Santana-Ros, T.; Storrs, A.; Tanga, P.; Vigan, A.;
Warner, B.; Wieczorek, M.; Witasse, O.; Yang, B.
2021yCat..36500129C Altcode:
Sylvia was observed with the SPHERE instrument (ESO/VLT) around its
opposition at eleven different epochs. We used IRDIS in broad band
(Y filter; filter central wavelength 1041.4nm, width = 135.2nm)
and ZIMPOL in narrowband imaging mode (N_R filter; filter central
wavelength = 645.9nm, width = 56.7nm). <P />Each observational sequence
consisted of a series of images, where each image corresponded to
a series of detector integration times (DITs) of 10s, during which
Sylvia was used as a natural guide star for adaptive optics (AO)
corrections. Observations were performed under good seeing conditions
(<=0.8") with an airmass usually below 1.6. Standard calibrations,
which include detector flat-fields and darks, were acquired in the
morning as part of the instrument calibration plan. <P />objects:
-------------------------------------------------------------------
Planet Name H Diam i e a mag km deg AU
-------------------------------------------------------------------
87 Sylvia 6.86 261.0 10.87567 0.09351718 3.48178042
-------------------------------------------------------------------
<P />(6 data files).
---------------------------------------------------------
Title: Three-Dimensional Tomographic Reconstruction and MHD Modeling
of the Solar Corona and Wind: WHPI Campaign Rotations CR-2219
and CR-2223
Authors: Lloveras, D.; Vásquez, A. M.; Nuevo, F.; Sachdeva, N.;
Manchester, W.; van der Holst, B.; Frazin, R. A.; Lamy, P.; Wojak, J.
2020AGUFMSH021..07L Altcode:
Accurate prediction of space weather conditions requires
state-of-the-art three-dimensional (3D) magnetohydrodynamic (MHD)
models, which need to be validated with observational data. The recent
deep minimum of solar activity, between solar cycles 24 and 25, renews
the opportunity to study the Sun-Earth connection under the simplest
solar and space environmental conditions. The international Whole
Heliosphere and Planetary Interactions (WHPI) initiative aims at this
specific purpose. In this work, we study two WHPI campaign periods,
the July 2019 total solar eclipse Carrington rotation (CR)-2019, and
the Parker Solar Probe and STEREO-A closest approach CR-2223. Based
on narrowband EUV data provided by the SDO/AIA instrument we carry
out tomographic reconstruction of the coronal electron density
and temperature in the range of heliocentric heights r ≤ 1.25
R<SUB>sun</SUB>. Based on visible light coronagraph data provided by
the SoHO/LASCO-C2 instrument we carry out tomographic reconstruction of
the coronal electron density and in the range of heliocentric heights
≈ 2.5-6.0 R<SUB>sun</SUB>. Applying ADAPT-GONG synoptic magnetograms
as boundary conditions, we use the Alfven Wave Solar Model (AWSoM)
to simulate the corona and solar wind for these time periods. We
study the capability of the 3D-MHD model to reproduce the tomographic
reconstructions in both closed and open coronal magnetic structures. In
coronal holes in particular, we investigate the correlation between
the reconstructed 3D distribution of the thermodynamical properties
in the low corona and the 3D distribution of the physical parameters
of the terminal solar wind of the model, discriminating its fast and
slow components
---------------------------------------------------------
Title: Volume uncertainty of (7) Iris shape models from disc-resolved
images
Authors: Dudziński, G.; Podlewska-Gaca, E.; Bartczak, P.; Benseguane,
S.; Ferrais, M.; Jorda, L.; Hanuš, J.; Vernazza, P.; Rambaux,
N.; Carry, B.; Marchis, F.; Marsset, M.; Viikinkoski, M.; Brož,
M.; Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Jehin, E.;
Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas,
C.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.;
Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier,
F.; Vigan, A.; Witasse, O.; Yang, B.
2020MNRAS.499.4545D Altcode: 2020MNRAS.tmp.2956D
High angular resolution disc-resolved images of (7) Iris collected by
VLT/SPHERE instrument are allowed for the detailed shape modelling of
this large asteroid revealing its surface features. If (7) Iris did
not suffer any events catastrophic enough to disrupt the body (which
is very likely) by studying its topography, we might get insights
into the early Solar system's collisional history. When it comes to
internal structure and composition, thoroughly assessing the volume and
density uncertainties is necessary. In this work, we propose a method
of uncertainty calculation of asteroid shape models based on light
curve and adaptive optics (AO) images. We apply this method on four
models of (7) Iris produced from independent Shaping Asteroids using
Genetic Evolution and All-Data Asteroid Modelling inversion techniques
and multiresolution photoclinometry by deformation. Obtained diameter
uncertainties stem from both the observations from which the models were
scaled and the models themselves. We show that despite the availability
of high-resolution AO images, the volume and density of (7) Iris have
substantial error bars that were underestimated in the previous studies.
---------------------------------------------------------
Title: The Solar Orbiter Heliospheric Imager (SoloHI)
Authors: Howard, R. A.; Vourlidas, A.; Colaninno, R. C.; Korendyke,
C. M.; Plunkett, S. P.; Carter, M. T.; Wang, D.; Rich, N.; Lynch,
S.; Thurn, A.; Socker, D. G.; Thernisien, A. F.; Chua, D.; Linton,
M. G.; Koss, S.; Tun-Beltran, S.; Dennison, H.; Stenborg, G.; McMullin,
D. R.; Hunt, T.; Baugh, R.; Clifford, G.; Keller, D.; Janesick, J. R.;
Tower, J.; Grygon, M.; Farkas, R.; Hagood, R.; Eisenhauer, K.; Uhl,
A.; Yerushalmi, S.; Smith, L.; Liewer, P. C.; Velli, M. C.; Linker,
J.; Bothmer, V.; Rochus, P.; Halain, J. -P.; Lamy, P. L.; Auchère,
F.; Harrison, R. A.; Rouillard, A.; Patsourakos, S.; St. Cyr, O. C.;
Gilbert, H.; Maldonado, H.; Mariano, C.; Cerullo, J.
2020A&A...642A..13H Altcode:
<BR /> Aims: We present the design and pre-launch performance of
the Solar Orbiter Heliospheric Imager (SoloHI) which is an instrument
prepared for inclusion in the ESA/NASA Solar Orbiter mission, currently
scheduled for launch in 2020. <BR /> Methods: The goal of this paper
is to provide details of the SoloHI instrument concept, design, and
pre-flight performance to give the potential user of the data a better
understanding of how the observations are collected and the sources
that contribute to the signal. <BR /> Results: The paper discusses
the science objectives, including the SoloHI-specific aspects, before
presenting the design concepts, which include the optics, mechanical,
thermal, electrical, and ground processing. Finally, a list of planned
data products is also presented. <BR /> Conclusions: The performance
measurements of the various instrument parameters meet or exceed the
requirements derived from the mission science objectives. SoloHI is
poised to take its place as a vital contributor to the science success
of the Solar Orbiter mission.
---------------------------------------------------------
Title: Metis: the Solar Orbiter visible light and ultraviolet
coronal imager
Authors: Antonucci, Ester; Romoli, Marco; Andretta, Vincenzo; Fineschi,
Silvano; Heinzel, Petr; Moses, J. Daniel; Naletto, Giampiero; Nicolini,
Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Berlicki, Arkadiusz;
Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi,
Mauro; Frassetto, Fabio; Heerlein, Klaus; Landini, Federico; Magli,
Enrico; Marco Malvezzi, Andrea; Massone, Giuseppe; Melich, Radek;
Nicolosi, Piergiorgio; Noci, Giancarlo; Pancrazzi, Maurizio; Pelizzo,
Maria G.; Poletto, Luca; Sasso, Clementina; Schühle, Udo; Solanki,
Sami K.; Strachan, Leonard; Susino, Roberto; Tondello, Giuseppe;
Uslenghi, Michela; Woch, Joachim; Abbo, Lucia; Bemporad, Alessandro;
Casti, Marta; Dolei, Sergio; Grimani, Catia; Messerotti, Mauro;
Ricci, Marco; Straus, Thomas; Telloni, Daniele; Zuppella, Paola;
Auchère, Frederic; Bruno, Roberto; Ciaravella, Angela; Corso,
Alain J.; Alvarez Copano, Miguel; Aznar Cuadrado, Regina; D'Amicis,
Raffaella; Enge, Reiner; Gravina, Alessio; Jejčič, Sonja; Lamy,
Philippe; Lanzafame, Alessandro; Meierdierks, Thimo; Papagiannaki,
Ioanna; Peter, Hardi; Fernandez Rico, German; Giday Sertsu, Mewael;
Staub, Jan; Tsinganos, Kanaris; Velli, Marco; Ventura, Rita; Verroi,
Enrico; Vial, Jean-Claude; Vives, Sebastien; Volpicelli, Antonio;
Werner, Stephan; Zerr, Andreas; Negri, Barbara; Castronuovo, Marco;
Gabrielli, Alessandro; Bertacin, Roberto; Carpentiero, Rita; Natalucci,
Silvia; Marliani, Filippo; Cesa, Marco; Laget, Philippe; Morea, Danilo;
Pieraccini, Stefano; Radaelli, Paolo; Sandri, Paolo; Sarra, Paolo;
Cesare, Stefano; Del Forno, Felice; Massa, Ernesto; Montabone, Mauro;
Mottini, Sergio; Quattropani, Daniele; Schillaci, Tiziano; Boccardo,
Roberto; Brando, Rosario; Pandi, Arianna; Baietto, Cristian; Bertone,
Riccardo; Alvarez-Herrero, Alberto; García Parejo, Pilar; Cebollero,
María; Amoruso, Mauro; Centonze, Vito
2020A&A...642A..10A Altcode: 2019arXiv191108462A
<BR /> Aims: Metis is the first solar coronagraph designed for a
space mission and is capable of performing simultaneous imaging of the
off-limb solar corona in both visible and UV light. The observations
obtained with Metis aboard the Solar Orbiter ESA-NASA observatory
will enable us to diagnose, with unprecedented temporal coverage and
spatial resolution, the structures and dynamics of the full corona
in a square field of view (FoV) of ±2.9° in width, with an inner
circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7
R<SUB>⊙</SUB> to about 9 R<SUB>⊙</SUB>, owing to the eccentricity
of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter
mission profile, Metis will be able to observe the solar corona
from a close (0.28 AU, at the closest perihelion) vantage point,
achieving increasing out-of-ecliptic views with the increase of the
orbit inclination over time. Moreover, observations near perihelion,
during the phase of lower rotational velocity of the solar surface
relative to the spacecraft, allow longer-term studies of the off-limb
coronal features, thus finally disentangling their intrinsic evolution
from effects due to solar rotation. <BR /> Methods: Thanks to a novel
occultation design and a combination of a UV interference coating of
the mirrors and a spectral bandpass filter, Metis images the solar
corona simultaneously in the visible light band, between 580 and 640
nm, and in the UV H I Lyman-α line at 121.6 nm. The visible light
channel also includes a broadband polarimeter able to observe the
linearly polarised component of the K corona. The coronal images in
both the UV H I Lyman-α and polarised visible light are obtained at
high spatial resolution with a spatial scale down to about 2000 km
and 15 000 km at perihelion, in the cases of the visible and UV light,
respectively. A temporal resolution down to 1 s can be achieved when
observing coronal fluctuations in visible light. <BR /> Results: The
Metis measurements, obtained from different latitudes, will allow for
complete characterisation of the main physical parameters and dynamics
of the electron and neutral hydrogen/proton plasma components of the
corona in the region where the solar wind undergoes the acceleration
process and where the onset and initial propagation of coronal mass
ejections (CMEs) take place. The near-Sun multi-wavelength coronal
imaging performed with Metis, combined with the unique opportunities
offered by the Solar Orbiter mission, can effectively address crucial
issues of solar physics such as: the origin and heating/acceleration
of the fast and slow solar wind streams; the origin, acceleration,
and transport of the solar energetic particles; and the transient
ejection of coronal mass and its evolution in the inner heliosphere,
thus significantly improving our understanding of the region connecting
the Sun to the heliosphere and of the processes generating and driving
the solar wind and coronal mass ejections. <BR /> Conclusions: This
paper presents the scientific objectives and requirements, the overall
optical design of the Metis instrument, the thermo-mechanical design,
and the processing and power unit; reports on the results of the
campaigns dedicated to integration, alignment, and tests, and to
the characterisation of the instrument performance; describes the
operation concept, data handling, and software tools; and, finally,
the diagnostic techniques to be applied to the data, as well as a brief
description of the expected scientific products. The performance of the
instrument measured during calibrations ensures that the scientific
objectives of Metis can be pursued with success. <P />Metis website:
<A href="http://metis.oato.inaf.it">http://metis.oato.inaf.it</A>
---------------------------------------------------------
Title: Coronal Photopolarimetry with the LASCO-C3 Coronagraph over
24 Years [1996-2019] -- Application to the K/F Separation and to
the Determination of the Electron Density
Authors: Lamy, Philippe; Gilardy, Hugo; Llebaria, Antoine; Quemerais,
Eric; Ernandes, Fabrice
2020arXiv200904820L Altcode:
We present an in-depth characterization of the polarimetric channel of
the Large-Angle Spectrometric COronagraph/LASCO-C3 onboard SOHO. The
polarimetric analysis of the white-light images makes use of polarized
sequences composed of three images obtained through three polarizers
oriented at +60$^\circ$, 0$^\circ$, and -60$^\circ$, complemented by a
neighboring unpolarized image. However, the degradation of the 0$^\circ$
polarizer noticed in 1999 compelled us to reconstruct the corresponding
images from the other ones thereafter. The analysis closely follows the
method developed for LASCO-C2 (Lamy, et al. Solar Physics 295, 89, 2020
and arXiv:2001.05925) and implements the formalism of Mueller, albeit
with additional difficulties notably the presence of a non-axially
symmetric component of stray light. Critical corrections were derived
from a SOHO roll sequence and from consistency criteria (e.g.,
the tangential direction of polarization). The quasi-uninterrupted
photopolarimetric analysis of the outer corona over two complete
Solar Cycles 23 and 24 was successfully achieved and our final
results encompass the characterization of its polarization, of its
polarized radiance, of the two-dimensional electron density, and of the
K-corona. Comparison between the C3 and C2 results where their field of
view overlaps shows an overall agreement. The C3 results are further
in agreement with those of eclipses and radio ranging measurements
to an elongation of about 10 solar radii but tend to diverge further
out. Whereas the coronal polarization out to 20 solar radii is still
highly correlated with the temporal variation of the total magnetic
field, this divergence probably results from the increasing polarization
of the F-corona.
---------------------------------------------------------
Title: Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical
Authors: Yang, B.; Hanuš, J.; Carry, B.; Vernazza, P.; Brož, M.;
Vachier, F.; Rambaux, N.; Marsset, M.; Chrenko, O.; Ševeček, P.;
Viikinkoski, M.; Jehin, E.; Ferrais, M.; Podlewska-Gaca, E.; Drouard,
A.; Marchis, F.; Birlan, M.; Benkhaldoun, Z.; Berthier, J.; Bartczak,
P.; Dumas, C.; Dudziński, G.; Ďurech, J.; Castillo-Rogez, J.;
Cipriani, F.; Colas, F.; Fetick, R.; Fusco, T.; Grice, J.; Jorda,
L.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Marciniak, A.;
Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros, T.; Tanga,
P.; Vigan, A.; Witasse, O.
2020A&A...641A..80Y Altcode: 2020arXiv200708059Y
<BR /> Aims: Asteroid (31) Euphrosyne is one of the biggest objects in
the asteroid main belt and it is also the largest member of its namesake
family. The Euphrosyne family occupies a highly inclined region in the
outer main belt and contains a remarkably large number of members, which
is interpreted as an outcome of a disruptive cratering event. <BR />
Methods: The goals of this adaptive-optics imaging study are threefold:
to characterize the shape of Euphrosyne, to constrain its density, and
to search for the large craters that may be associated with the family
formation event. <BR /> Results: We obtained disk-resolved images of
Euphrosyne using SPHERE/ZIMPOL at the ESO 8.2 m VLT as part of our large
program (ID: 199.C-0074, PI: Vernazza). We reconstructed its 3D shape
via the ADAM shape modeling algorithm based on the SPHERE images and
the available light curves of this asteroid. We analyzed the dynamics
of the satellite with the Genoid meta-heuristic algorithm. Finally,
we studied the shape of Euphrosyne using hydrostatic equilibrium
models. <BR /> Conclusions: Our SPHERE observations show that Euphrosyne
has a nearly spherical shape with the sphericity index of 0.9888 and
its surface lacks large impact craters. Euphrosyne's diameter is 268
± 6 km, making it one of the top ten largest main belt asteroids. We
detected a satellite of Euphrosyne - S/2019 (31) 1 - that is about 4
km across, on a circular orbit. The mass determined from the orbit
of the satellite together with the volume computed from the shape
model imply a density of 1665 ± 242 kg m<SUP>-3</SUP>, suggesting
that Euphrosyne probably contains a large fraction of water ice in its
interior. We find that the spherical shape of Euphrosyne is a result of
the reaccumulation process following the impact, as in the case of (10)
Hygiea. However, our shape analysis reveals that, contrary to Hygiea,
the axis ratios of Euphrosyne significantly differ from those suggested
by fluid hydrostatic equilibrium following reaccumulation. <P />The
reduced images are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/641/A80">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/641/A80</A>
<P />Based on observations made with ESO Telescopes at the La Silla
Paranal Observatory under program 199.C-0074 (PI Vernazza).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Asteroid (31) Euphrosyne R-band
images (Yang+, 2020)
Authors: Yang, B.; Hanus, J.; Carry, B.; Vernazza, P.; Broz,
M.; Vachier, F.; Rambaux, N.; Marsset, M.; Chrenko, O.; Sevecek,
P.; Viikinkoski, M.; Jehin, E.; Ferrais, M.; Podlewska-Gaca, E.;
Drouard, A.; Marchis, F.; Birlan, M.; Benkhaldoun, Z.; Berthier, J.;
Bartczak, P.; Dumas, C.; Dudzinski, G.; Durech, J.; Castillo-Rogez,
J.; Cipriani, F.; Colas, F.; Fetick, R.; Fusco, T.; Grice, J.;
Jorda, L.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Marciniak,
A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros, T.; Tanga,
P.; Vigan, A.; Witasse, O.
2020yCat..36410080Y Altcode:
Euphrosyne was observed, between March and April 2019 (2019-03-15,
2019-03-20, 2019-03-25, 2019-03-27, 2019-04-10), using the Zurich
Imaging Polarimeter (ZIMPOL) of SPHERE in the direct imaging mode with
the narrow band filter (N_R filter; filter central wavelength=645.9nm,
width=56.7nm). <P />(2 data files).
---------------------------------------------------------
Title: Coronal Photopolarimetry with the LASCO-C2 Coronagraph over
24 Years [1996 - 2019]
Authors: Lamy, Philippe; Llebaria, Antoine; Boclet, Brice; Gilardy,
Hugo; Burtin, Michael; Floyd, Olivier
2020SoPh..295...89L Altcode: 2020arXiv200105925L
We present an in-depth characterization of the polarimetric channel of
the Large-Angle Spectrometric COronagraph/LASCO-C2 onboard the Solar
and Heliospheric Observatory (SOHO). The polarimetric analysis of the
white-light images makes use of polarized sequences composed of three
images obtained though three polarizers oriented at +60<SUP>∘</SUP>,
0<SUP>∘</SUP>, and −60<SUP>∘</SUP>, complemented by a neighboring
unpolarized image, and relies on the formalism of Mueller. The
Mueller matrix characterizing the C2 instrument was obtained through
extensive ground-based calibrations of the optical components and
global laboratory tests. Additional critical corrections were derived
from in-flight tests relying prominently on roll sequences of SOHO, on
the basis of consistency criteria (e.g. the "tangential" direction of
polarization), and from several applications, notably the time-dependent
tomographic reconstruction of the coronal electron density. This
took several years of effort, but resulted in the quasi-uninterrupted
photopolarimetric analysis of the corona over two complete Solar Cycles
23 and 24, and the comparison with a variety of eclipse data obtained
at different phases of these cycles. Our final results encompass
the characterization of the polarization of the white-light corona,
of its polarized radiance, of the two-dimensional electron density,
and of the K-corona. The agreement with the eclipse data is excellent
except for slight discrepancies affecting the innermost part of the C2
field of view. The present work leaves the two unpolarized components,
F-corona and stray light, entangled and their complex separation will
be dealt with in a follow-on article.
---------------------------------------------------------
Title: VizieR Online Data Catalog: (16) Psyche. VLT/SPHERE images
and shape models (Ferrais+, 2020)
Authors: Ferrais, M.; Vernazza, P.; Jorda, L.; Rambaux, N.; Hanu,
J.; Carry, B.; Marchis, F.; Marsset, M.; Viikinkoski, M.; Broz, M.;
Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.;
Jehin, E.; Bartczak, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani,
F.; Colas, F.; Dudzinski, G.; Dumas, C.; Durech, J.; Kaasalainen,
M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.;
Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier,
F.; Vigan, A.; Witasse, O.; Yang, B.
2020yCat..36389015F Altcode:
We obtained 35 images of Psyche at 7 epochs in July and August 2019
using VLT/SPHERE/ZIMPOL. This data set complements the first 25 images
taken within our ESO large program that was already presented in
Viikinkoski et al. (2018A&A...619L...3V), for a total of 60 images
taken at 12 epochs. All images were reduced following the procedure
described in Vernazza et al. (2018A&A...618A.154V). <P />object:
-------------------------------------------------------------------
Planet Name H Diam i e a mag km deg AU
-------------------------------------------------------------------
16 Psyche 5.90 222.0 3.096560 0.13353119 2.92277557
------------------------------------------------------------------
<P />(8 data files).
---------------------------------------------------------
Title: Asteroid (16) Psyche's primordial shape: A possible Jacobi
ellipsoid
Authors: Ferrais, M.; Vernazza, P.; Jorda, L.; Rambaux, N.; Hanuš,
J.; Carry, B.; Marchis, F.; Marsset, M.; Viikinkoski, M.; Brož, M.;
Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.;
Jehin, E.; Bartczak, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani,
F.; Colas, F.; Dudziński, G.; Dumas, C.; Ďurech, J.; Kaasalainen,
M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.;
Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier,
F.; Vigan, A.; Witasse, O.; Yang, B.
2020A&A...638L..15F Altcode:
Context. Asteroid (16) Psyche is the largest M-type asteroid in the
main belt and the target of the NASA Psyche mission. It is also the only
asteroid of this size (D > 200 km) known to be metal rich. Although
various hypotheses have been proposed to explain the rather unique
physical properties of this asteroid, a perfect understanding of
its formation and bulk composition is still missing. <BR /> Aims:
We aim to refine the shape and bulk density of (16) Psyche and to
perform a thorough analysis of its shape to better constrain possible
formation scenarios and the structure of its interior. <BR /> Methods:
We obtained disk-resolved VLT/SPHERE/ZIMPOL images acquired within
our ESO large program (ID 199.C-0074), which complement similar
data obtained in 2018. Both data sets offer a complete coverage
of Psyche's surface. These images were used to reconstruct the
three-dimensional (3D) shape of Psyche with two independent shape
modeling algorithms (MPCD and ADAM). A shape analysis was subsequently
performed, including a comparison with equilibrium figures and the
identification of mass deficit regions. <BR /> Results: Our 3D shape
along with existing mass estimates imply a density of 4.20 ± 0.60
g cm<SUP>-3</SUP>, which is so far the highest for a solar system
object following the four telluric planets. Furthermore, the shape
of Psyche presents small deviations from an ellipsoid, that is,
prominently three large depressions along its equator. The flatness
and density of Psyche are compatible with a formation at hydrostatic
equilibrium as a Jacobi ellipsoid with a shorter rotation period of
∼3h. Later impacts may have slowed down Psyche's rotation, which is
currently ∼4.2 h, while also creating the imaged depressions. <BR />
Conclusions: Our results open the possibility that Psyche acquired
its primordial shape either after a giant impact while its interior
was already frozen or while its interior was still molten owing to
the decay of the short-lived radionuclide <SUP>26</SUP>Al. <P />The
reduced images are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/638/L15">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/638/L15</A>
<P />Based on observations made with ESO Telescopes at the Paranal
Observatory under programme ID 199.C-0074 (PI: P. Vernazza).
---------------------------------------------------------
Title: The violent collisional history of aqueously evolved (2) Pallas
Authors: Marsset, Michaël; Brož, Miroslav; Vernazza, Pierre; Drouard,
Alexis; Castillo-Rogez, Julie; Hanuš, Josef; Viikinkoski, Matti;
Rambaux, Nicolas; Carry, Benoît; Jorda, Laurent; Ševeček, Pavel;
Birlan, Mirel; Marchis, Franck; Podlewska-Gaca, Edyta; Asphaug, Erik;
Bartczak, Przemyslaw; Berthier, Jérôme; Cipriani, Fabrice; Colas,
François; Dudziński, Grzegorz; Dumas, Christophe; Durech, Josef;
Ferrais, Marin; Fétick, Romain; Fusco, Thierry; Jehin, Emmanuel;
Kaasalainen, Mikko; Kryszczynska, Agnieszka; Lamy, Philippe; Le
Coroller, Hervé; Marciniak, Anna; Michalowski, Tadeusz; Michel,
Patrick; Richardson, Derek C.; Santana-Ros, Toni; Tanga, Paolo;
Vachier, Frédéric; Vigan, Arthur; Witasse, Olivier; Yang, Bin
2020NatAs...4..569M Altcode: 2020NatAs.tmp...24M
Asteroid (2) Pallas is the largest main-belt object not yet visited by
a spacecraft, making its surface geology largely unknown and limiting
our understanding of its origin and collisional evolution. Previous
ground-based observational campaigns returned different estimates
of its bulk density that are inconsistent with one another, one
measurement<SUP>1</SUP> being compatible within error bars with
the icy Ceres (2.16 ± 0.01 g cm<SUP>-3</SUP>)<SUP>2</SUP> and
the other<SUP>3</SUP> compatible within error bars with the rocky
Vesta (3.46 ± 0.03 g cm<SUP>-3</SUP>)<SUP>4</SUP>. Here we report
high-angular-resolution observations of Pallas performed with the
extreme adaptive optics-fed SPHERE imager<SUP>5</SUP> on the Very
Large Telescope. Pallas records a violent collisional history, with
numerous craters larger than 30 km in diameter populating its surface
and two large impact basins that could be related to a family-forming
impact. Monte Carlo simulations of the collisional evolution of the
main belt correlate this cratering record to the high average impact
velocity of ~11.5 km s<SUP>-1</SUP> on Pallas—compared with an
average of ~5.8 km s<SUP>-1</SUP> for the asteroid belt—induced by
Pallas's high orbital inclination (i = 34.8°) and orbital eccentricity
(e = 0.23). Compositionally, Pallas's derived bulk density of 2.89 ±
0.08 g cm<SUP>-3</SUP> (1σ uncertainty) is fully compatible with a CM
chondrite-like body, as suggested by its spectral reflectance in the 3
μm wavelength region<SUP>6</SUP>. A bright spot observed on its surface
may indicate an enrichment in salts during an early phase of aqueous
alteration, compatible with Pallas's relatively high albedo of 12-17%
(refs. <SUP>7,8</SUP>), although alternative origins are conceivable.
---------------------------------------------------------
Title: A basin-free spherical shape as an outcome of a giant impact
on asteroid Hygiea
Authors: Vernazza, P.; Jorda, L.; Ševeček, P.; Brož, M.;
Viikinkoski, M.; Hanuš, J.; Carry, B.; Drouard, A.; Ferrais, M.;
Marsset, M.; Marchis, F.; Birlan, M.; Podlewska-Gaca, E.; Jehin,
E.; Bartczak, P.; Dudzinski, G.; Berthier, J.; Castillo-Rogez, J.;
Cipriani, F.; Colas, F.; DeMeo, F.; Dumas, C.; Durech, J.; Fetick,
R.; Fusco, T.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy,
P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.;
Rambaux, N.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.;
Witasse, O.; Yang, B.; Gillon, M.; Benkhaldoun, Z.; Szakats, R.;
Hirsch, R.; Duffard, R.; Chapman, A.; Maestre, J. L.
2020NatAs...4..136V Altcode: 2019NatAs.tmp..477V
(10) Hygiea is the fourth largest main belt asteroid and the only
known asteroid whose surface composition appears similar to that of
the dwarf planet (1) Ceres<SUP>1,2</SUP>, suggesting a similar origin
for these two objects. Hygiea suffered a giant impact more than 2 Gyr
ago<SUP>3</SUP> that is at the origin of one of the largest asteroid
families. However, Hygeia has never been observed with sufficiently
high resolution to resolve the details of its surface or to constrain
its size and shape. Here, we report high-angular-resolution imaging
observations of Hygiea with the VLT/SPHERE instrument (~20 mas
at 600 nm) that reveal a basin-free nearly spherical shape with
a volume-equivalent radius of 217 ± 7 km, implying a density of
1,944 ± 250 kg m<SUP>-</SUP><SUP>3</SUP> to 1σ. In addition, we
have determined a new rotation period for Hygiea of ~13.8 h, which
is half the currently accepted value. Numerical simulations of the
family-forming event show that Hygiea's spherical shape and family can
be explained by a collision with a large projectile (diameter ~75-150
km). By comparing Hygiea's sphericity with that of other Solar System
objects, it appears that Hygiea is nearly as spherical as Ceres, opening
up the possibility for this object to be reclassified as a dwarf planet.
---------------------------------------------------------
Title: (704) Interamnia: a transitional object between a dwarf planet
and a typical irregular-shaped minor body
Authors: Hanuš, J.; Vernazza, P.; Viikinkoski, M.; Ferrais, M.;
Rambaux, N.; Podlewska-Gaca, E.; Drouard, A.; Jorda, L.; Jehin,
E.; Carry, B.; Marsset, M.; Marchis, F.; Warner, B.; Behrend, R.;
Asenjo, V.; Berger, N.; Bronikowska, M.; Brothers, T.; Charbonnel,
S.; Colazo, C.; Coliac, J. -F.; Duffard, R.; Jones, A.; Leroy, A.;
Marciniak, A.; Melia, R.; Molina, D.; Nadolny, J.; Person, M.; Pejcha,
O.; Riemis, H.; Shappee, B.; Sobkowiak, K.; Soldán, F.; Suys, D.;
Szakats, R.; Vantomme, J.; Birlan, M.; Berthier, J.; Bartczak, P.;
Dumas, C.; Dudziński, G.; Ďurech, J.; Castillo-Rogez, J.; Cipriani,
F.; Fetick, R.; Fusco, T.; Grice, J.; Kaasalainen, M.; Kryszczynska,
A.; Lamy, P.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga,
P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B.
2020A&A...633A..65H Altcode: 2019arXiv191113049H
Context. With an estimated diameter in the 320-350 km range, (704)
Interamnia is the fifth largest main belt asteroid and one of the
few bodies that fills the gap in size between the four largest bodies
with D > 400 km (Ceres, Vesta, Pallas and Hygiea) and the numerous
smaller bodies with diameter ≤200 km. However, despite its large
size, little is known about the shape and spin state of Interamnia
and, therefore, about its bulk composition and past collisional
evolution. <BR /> Aims: We aimed to test at what size and mass the
shape of a small body departs from a nearly ellipsoidal equilibrium
shape (as observed in the case of the four largest asteroids) to
an irregular shape as routinely observed in the case of smaller (D
≤ 200 km) bodies. <BR /> Methods: We observed Interamnia as part
of our ESO VLT/SPHERE large program (ID: 199.C-0074) at thirteen
different epochs. In addition, several new optical lightcurves were
recorded. These data, along with stellar occultation data from the
literature, were fed to the All-Data Asteroid Modeling algorithm to
reconstruct the 3D-shape model of Interamnia and to determine its spin
state. <BR /> Results: Interamnia's volume-equivalent diameter of 332
± 6 km implies a bulk density of ρ = 1.98 ± 0.68 g cm<SUP>-3</SUP>,
which suggests that Interamnia - like Ceres and Hygiea - contains a
high fraction of water ice, consistent with the paucity of apparent
craters. Our observations reveal a shape that can be well approximated
by an ellipsoid, and that is compatible with a fluid hydrostatic
equilibrium at the 2σ level. <BR /> Conclusions: The rather regular
shape of Interamnia implies that the size and mass limit, under which
the shapes of minor bodies with a high amount of water ice in the
subsurface become irregular, has to be searched among smaller (D ≤
300 km) less massive (m ≤ 3 × 10<SUP>19</SUP> kg) bodies. <P />The
reduced images are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/633/A65">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/633/A65</A>
<P />Based on observations made with ESO Telescopes at the La Silla
Paranal Observatory under program 199.C-0074 (PI: Vernazza).
---------------------------------------------------------
Title: Imaging the Solar Corona From Within
Authors: Hess, P.; Howard, R.; Vourlidas, A.; Bothmer, V.; Colaninno,
R.; DeForest, C.; Gallagher, B.; Hall, J. R.; Higginson, A.; Korendyke,
C.; Kouloumvakos, A.; Lamy, P.; Liewer, P.; Linker, J.; Linton, M.;
Penteado, P.; Plunkett, S.; Poirer, N.; Raouafi, N.; Rich, N.; Rochus,
P.; Rouillard, A.; Socker, D.; Stenborg, G.; Thernisien, A.; Viall, N.
2020AAS...23514907H Altcode:
Parker Solar Probe (PSP), launched, in August 2018 is humanity's
first probe of a stellar atmosphere. It will make measurements of
the near-Sun plasma from 'within' the outer corona with gradually
reduced perihelia from its first perihelia of 35 Rs in 2018-19 to 9.8
Rs in 2025. Here we report the results from the imaging observations
of the electron and dust corona, whe PSP was 35-54 Rs from the solar
surface, taken by the Wide-field Imager for Solar Probe (WISPR). The
spacecraft was near-corotating with the solar corona throughout the
observing window, which is an unprecedented situation for any type of
coronal imaging. Our initial analysis uncovers a long-hypothesized
depletion of the primordial dust orbiting near the Sun, reveals the
plasma structure of small-scale ejections, and provides a strict test
for validating model predictions of the large-scale configuration of
the coronal plasma. Thus, WISPR imaging allows the study of near-Sun
dust dynamics as the mission progresses. The high-resolution images
of small transients, largely unresolved from 1 AU orbits, unravel
the sub-structures of small magnetic flux ropes and show that the
Sun continually releases helical magnetic fields in the background
wind. Finally, WISPR's observations of the coronal streamer evolution
confirm the large-scale topology of the solar corona but they also
reveal that, as recently predicted, streamers are composed of yet
smaller sub-streamers channeling continual density fluctuations at
all visible scales.
---------------------------------------------------------
Title: Imaging the Solar Corona from Within: First Results from the
Parker Solar Probe Telescope
Authors: Howard, R. A.; Vourlidas, A.; Bothmer, V.; Colaninno, R. C.;
DeForest, C.; Gallagher, B.; Hall, J. R.; Hess, P.; Higginson, A. K.;
Korendyke, C.; Kouloumvakos, A.; Lamy, P.; Liewer, P. C.; Linker, J.;
Linton, M.; Penteado, P. F.; Plunkett, S. P.; Poirier, N.; Raouafi,
N.; Rich, N.; Rochus, P. L.; Rouillard, A. P.; Socker, D. G.; Stenborg,
G.; Thernisien, A.; Viall, N. M.
2019AGUFMSH11A..04H Altcode:
Parker Solar Probe (PSP) launched in August 2018 is humanity's
first probe of a stellar atmosphere. It will make measurements of
the near-Sun plasma from 'within' the outer corona with gradually
reduced perihelia from its first perihelia of 35 Rs in 2018-19 to 9.8
Rs in 2025. Here we report the results from the imaging observations
of the electron and dust corona, whe PSP was 35-54 Rs from the solar
surface, taken by the Wide-field Imager for Solar Probe (WISPR). The
spacecraft was near-corotating with the solar corona throughout the
observing window, which is an unprecedented situation for any type of
coronal imaging. Our initial analysis uncovers a long-hypothesized
depletion of the primordial dust orbiting near the Sun, reveals the
plasma structure of small-scale ejections, and provides a strict test
for validating model predictions of the large-scale configuration of
the coronal plasma. Thus, WISPR imaging allows the study of near-Sun
dust dynamics as the mission progresses. The high-resolution images
of small transients, largely unresolved from 1 AU orbits, unravel
the sub-structures of small magnetic flux ropes and show that the
Sun continually releases helical magnetic fields in the background
wind. Finally, WISPR's observations of the coronal streamer evolution
confirm the large-scale topology of the solar corona but they also
reveal that, as recently predicted, streamers are composed of yet
smaller sub-streamers channeling continual density fluctuations at
all visible scales.
---------------------------------------------------------
Title: Polarimetric Reconstruction of Coronal Mass Ejections from
LASCO-C2 Observations
Authors: Floyd, Olivier; Lamy, Philippe
2019SoPh..294..168F Altcode:
The three-dimensional morphology and direction of propagation of coronal
mass ejections (CMEs) are essential information for identifying their
source on the solar disk, for understanding the processes of their
ejection and propagation in the corona, and for forecasting their
possible impact with the Earth or any other objects in the solar
system. The polarization of the Thomson scattering by an electron
is known to provide information on its position with respect to
the plane of the sky. This polarimetric technique is applied to
reconstruct 15 CMEs on the basis of white-light polarized images
obtained with the Large Angle Spectrometric Coronagraph (LASCO) C2,
which have been extensively corrected for instrumental effects. It
does provide valuable results in spite of the time delays between
the three observations required to build the polarization maps. Most
of these CMEs exhibit complex structures making a classification in
terms of simple shapes such as arcade of loops or flux rope difficult
or even questionable. Three of these CMEs benefited from multiple
observations allowing us to follow their three-dimensional development
as they propagated outward. All CMEs are tracked back to the solar
surface and in several instances, active regions are identified as
the probable sources. Finally, the projected speeds and masses derived
from white-light unpolarized observations have been corrected for the
projection angle to produce unbiased values.
---------------------------------------------------------
Title: The Solar Orbiter Heliospheric Imager (SoloHI) for the Solar
Orbiter Mission: Science and Instrument Status
Authors: Vourlidas, A.; Howard, R. A.; Colaninno, R. C.; Korendyke,
C.; Thernisien, A.; Linton, M.; Tun Beltran, S.; Liewer, P. C.; Velli,
M.; Linker, J.; Bothmer, V.; Rochus, P. L.; Lamy, P. L.
2019AGUFMSH24A..08V Altcode:
The SoloHI instrument has completed its development effort and has been
integrated onto the Solar Orbiter spacecraft. The mission, scheduled
for launch in February 2020, will undergo gravity assist maneuvers
around Venus to change both the perihelion distance as well as the
plane of the orbit to ultimately achieve a minimum perihelion of 0.28
AU and an orbital inclination of about 35° relative to the ecliptic
plane. The remote sensing instruments will operate for three 10-day
periods out of the nominal 6-month orbit. SoloHI detects sunlight
scattered by free electrons in the corona and solar wind from 5° to
45° elongation in visible wavelengths, providing linkage between solar
and solar wind observations. The science investigation focuses mainly on
the solar wind, including streamers, small-scale intensity and density
fluctuations, jets, and Coronal Mass Ejections (CMEs). SoloHI is very
similar to the HI-1 instrument on STEREO/SECCHI but with double the FOV
of HI-1. In this paper, we present our preparations for the mission
including the instrument status, our science planning strategy, our
observing plans for cruise phase, calibrations, early science and our
low-latency and science data products <P />This work has been supported
by NASA.
---------------------------------------------------------
Title: Near-Sun observations of an F-corona decrease and K-corona
fine structure
Authors: Howard, R. A.; Vourlidas, A.; Bothmer, V.; Colaninno, R. C.;
DeForest, C. E.; Gallagher, B.; Hall, J. R.; Hess, P.; Higginson,
A. K.; Korendyke, C. M.; Kouloumvakos, A.; Lamy, P. L.; Liewer, P. C.;
Linker, J.; Linton, M.; Penteado, P.; Plunkett, S. P.; Poirier, N.;
Raouafi, N. E.; Rich, N.; Rochus, P.; Rouillard, A. P.; Socker, D. G.;
Stenborg, G.; Thernisien, A. F.; Viall, N. M.
2019Natur.576..232H Altcode:
Remote observations of the solar photospheric light scattered by
electrons (the K-corona) and dust (the F-corona or zodiacal light)
have been made from the ground during eclipses<SUP>1</SUP> and from
space at distances as small as 0.3 astronomical units<SUP>2-5</SUP> to
the Sun. Previous observations<SUP>6-8</SUP> of dust scattering have
not confirmed the existence of the theoretically predicted dust-free
zone near the Sun<SUP>9-11</SUP>. The transient nature of the corona
has been well characterized for large events, but questions still
remain (for example, about the initiation of the corona<SUP>12</SUP>
and the production of solar energetic particles<SUP>13</SUP>) and
for small events even its structure is uncertain<SUP>14</SUP>. Here
we report imaging of the solar corona<SUP>15</SUP> during the first
two perihelion passes (0.16-0.25 astronomical units) of the Parker
Solar Probe spacecraft<SUP>13</SUP>, each lasting ten days. The view
from these distances is qualitatively similar to the historical views
from ground and space, but there are some notable differences. At
short elongations, we observe a decrease in the intensity of the
F-coronal intensity, which is suggestive of the long-sought dust
free zone<SUP>9-11</SUP>. We also resolve the fine-scale plasma
structure of very small eruptions, which are frequently ejected from
the Sun. These take two forms: the frequently observed magnetic flux
ropes<SUP>12,16</SUP> and the predicted, but not yet observed, magnetic
islands<SUP>17,18</SUP> arising from the tearing-mode instability in
the current sheet. Our observations of the coronal streamer evolution
confirm the large-scale topology of the solar corona, but also reveal
that, as recently predicted<SUP>19</SUP>, streamers are composed of
yet smaller substreamers channelling continual density fluctuations
at all visible scales.
---------------------------------------------------------
Title: Spitzer Space Telescope observations of bilobate comet
8P/Tuttle
Authors: Groussin, O.; Lamy, P. L.; Kelley, M. S. P.; Toth, I.; Jorda,
L.; Fernández, Y. R.; Weaver, H. A.
2019A&A...632A.104G Altcode: 2019arXiv191104897G
Context. Comet 8P/Tuttle is a nearly isotropic comet whose physical
properties are poorly known and might be different from those of
ecliptic comets owing to their different origin. Two independent
observations have shown that 8P/Tuttle has a bilobate nucleus. <BR />
Aims: Our goal is to determine the physical properties of the nucleus
(size, shape, thermal inertia, and albedo) and coma (water and dust) of
8P/Tuttle. <BR /> Methods: We observed the inner coma of 8P/Tuttle with
the infrared spectrograph and the infrared camera of the Spitzer Space
Telescope. We obtained one spectrum (5-40 μm) on 2 November 2007 and a
set of 19 images at 24 μm on 22-23 June 2008 sampling the rotational
period of the nucleus. The data were interpreted using thermal models
for the nucleus and the dust coma, and we considered two possible shape
models of the nucleus derived from Hubble Space Telescope visible and
Arecibo radar observations. <BR /> Results: We favor a model for the
nucleus shape that is composed of two contact spheres with respective
radii of 2.7 ± 0.1 km and 1.1 ± 0.1 km and a pole orientation with RA
= 285 ± 12° and Dec = +20 ± 5°. The thermal inertia of the nucleus
lies in the range 0-100 J K<SUP>-1</SUP> m<SUP>-2</SUP> s<SUP>-1/2</SUP>
and the R-band geometric albedo is 0.042 ± 0.008. The water production
rate amounts to 1.1 ± 0.2 × 10<SUP>28</SUP> molecules s<SUP>-1</SUP>
at 1.6 AU from the Sun pre-perihelion, which corresponds to an active
fraction of ≈9%. At the same distance, the ɛfρ quantity amounts to
310 ± 34 cm, and it reaches 325 ± 36 cm at 2.2 AU post-perihelion. The
dust grain temperature is estimated to be 258 ± 10 K, which is 37
K higher than the thermal equilibrium temperature at 1.6 AU. This
indicates that the dust grains that contribute to the thermal infrared
flux have a typical size of ≈10 μm. The dust spectrum exhibits
broad emission around 10 μm (1.5σ confidence level) and 18 μm
(5σ confidence level) that we attribute to amorphous pyroxene.
---------------------------------------------------------
Title: Validation of the Alfvén Wave Solar Atmosphere Model (AWSoM)
with Observations from the Low Corona to 1 au
Authors: Sachdeva, Nishtha; van der Holst, Bart; Manchester, Ward B.;
Tóth, Gabor; Chen, Yuxi; Lloveras, Diego G.; Vásquez, Alberto M.;
Lamy, Philippe; Wojak, Julien; Jackson, Bernard V.; Yu, Hsiu-Shan;
Henney, Carl J.
2019ApJ...887...83S Altcode: 2019arXiv191008110S
We perform a validation study of the latest version of the Alfvén
Wave Solar atmosphere Model (AWSoM) within the Space Weather Modeling
Framework. To do so, we compare the simulation results of the model
with a comprehensive suite of observations for Carrington rotations
representative of the solar minimum conditions extending from the
solar corona to the heliosphere up to the Earth. In the low corona
(r < 1.25 {\text{}}{R}<SUB>⊙ </SUB>), we compare with EUV
images from both Solar-Terrestrial Relations Observatory-A/EUVI
and Solar Dynamics Observatory/Atmospheric Imaging Assembly and to
three-dimensional (3D) tomographic reconstructions of the electron
temperature and density based on these same data. We also compare the
model to tomographic reconstructions of the electron density from
Solar and Heliospheric Observatory/Large Angle and Spectrometric
Coronagraph observations (2.55 < r < 6.0{\text{}}{R}<SUB>⊙
</SUB>). In the heliosphere, we compare model predictions of solar wind
speed with velocity reconstructions from InterPlanetary Scintillation
observations. For comparison with observations near the Earth, we use
OMNI data. Our results show that the improved AWSoM model performs
well in quantitative agreement with the observations between the inner
corona and 1 au. The model now reproduces the fast solar wind speed
in the polar regions. Near the Earth, our model shows good agreement
with observations of solar wind velocity, proton temperature, and
density. AWSoM offers an extensive application to study the solar
corona and larger heliosphere in concert with current and future solar
missions as well as being well suited for space weather predictions.
---------------------------------------------------------
Title: The Rocky-Like Behavior of Cometary Landslides on
67P/Churyumov-Gerasimenko
Authors: Lucchetti, Alice; Penasa, Luca; Pajola, Maurizio; Massironi,
Matteo; Brunetti, Maria Teresa; Cremonese, Gabriele; Oklay, Nilda;
Vincent, Jean-Baptiste; Mottola, Stefano; Fornasier, Sonia; Sierks,
Holger; Naletto, Giampiero; Lamy, Philippe L.; Rodrigo, Rafael;
Koschny, Detlef; Davidsson, Bjorn; Barbieri, Cesare; Barucci,
Maria Antonietta; Bertaux, Jean-Loup; Bertini, Ivano; Bodewits,
Dennis; Cambianica, Pamela; Da Deppo, Vania; Debei, Stefano; De
Cecco, Mariolino; Deller, Jacob; Ferrari, Sabrina; Ferri, Francesca;
Franceschi, Marco; Fulle, Marco; Gutiérrez, Pedro; Güttler, Carsten;
Ip, Wing-H.; Keller, Uwe; Lara, Luisa; Lazzarin, Monica; Moreno,
Jose Lopez; Marzari, Francesco; Tubiana, Cecilia
2019GeoRL..4614336L Altcode:
Landslides have been identified on several solar system bodies,
and different mechanisms have been proposed to explain their runout
length. We analyze images from the Rosetta mission and report the global
characterization of such features on comet 67P/Churyumov-Gerasimenko's
surface. By assuming the height to runout length as an approximation for
the friction coefficient of landslide material, we find that on comet
67P, this ratio falls between 0.50 and 0.97. Such unexpected high values
reveal a rocky-type mechanical behavior that is much more akin to Earth
dry landslides than to icy satellites' mass movements. This behavior
indicates that 67P and likely comets in general are characterized by
consolidated materials possibly rejecting the idea that they are fluffy
aggregates. The variability of the runout length among 67P landslides
can be attributed to the different volatile content located in the
top few meters of the cometary crust, which can drive the mass movement.
---------------------------------------------------------
Title: Validating the Alfven Wave Solar Atmosphere (AWSoM) Model
from the Low Corona to 1 AU
Authors: Sachdeva, N.; van der Holst, B.; Manchester, W.; Toth, G.;
Lloveras, D. G.; Vásquez, A. M.; Lamy, P.; Jackson, B. V.; Henney,
C. J.
2019AGUFMSH51A..04S Altcode:
The coronal/solar wind model, the Alfven Wave Solar atmosphere Model
(AWSoM) a component within the Space Weather Modeling Framework (SWMF)
follows a self-consistent physics-based global description of coronal
heating and solar wind acceleration. AWSoM includes a description
of low-frequency forward and counter-propagating Alfven waves that
non-linearly interact resulting in a turbulent cascade and dissipative
heating. In addition, there are separate temperatures for electrons and
protons with collisional and collisionless heat conduction applied only
to electrons and radiative losses based on the Chianti model. AWSoM
extends from the base of the transition region where the strong
density gradient necessitates self-consistent treatment of Alfven wave
reflection and balanced turbulence. It includes a stochastic heating
model as well as a description of proton parallel and perpendicular
temperatures and kinetic instabilities based on temperature anisotropy
and plasma beta.To validate AWSoM, we model Carrington rotations
representative of solar minimum conditions and compare the simulation
results with a comprehensive suite of observations. In the low corona
(r < 1.25 Rs), we compare with EUV images from both STEREOA/EUVI
and SDO/AIA and to three-dimensional tomographic reconstructions of
the electron temperature and density based on these same data. We
also compare the model to tomographic reconstructions of the electron
density from SOHO/LASCO observations (2.55 < r < 6 Rs). In
the heliosphere, we compare model predictions of solar wind speed
with velocity reconstructions from Interplanetary Scintillation
observations. For comparison with observations near the Earth, we
use OMNI data. Our results show that the AWSoM model performs well
in quantitative agreement with the observations between the inner
corona and 1 AU. In the lower corona, the model and the tomographic
reconstructions agree within 20%-30% on average. The model also
reproduces the fast solar wind speed in the polar regions. Near the
Earth, our model shows good agreement with observations of solar wind
velocity, electron temperature and density. The AWSoM model provides
a comprehensive tool to study the solar corona and larger heliosphere
with current and future solar missions as well as being well suited
for space weather predictions.
---------------------------------------------------------
Title: VizieR Online Data Catalog: (704) Interamnia images (Hanus+,
2020)
Authors: Hanus, J.; Vernazza, P.; Viikinkoski, M.; Ferrais, M.;
Rambaux, N.; Podlewska-Gaca, E.; Drouard, A.; Jorda, L.; Jehin, E.;
Carry, B.; Marsset, M.; Marchis, F.; Warner, B.; Behrend, R.; Asenjo,
V.; Berger, N.; Bronikowska, M.; Brothers, T.; Charbonnel, S.; Colazo,
C.; Coliac, J. -F.; Duard, R.; Jones, A.; Leroy, A.; Marciniak, A.;
Melia, R.; Molina, D.; Nadolny, J.; Person, M.; Pejcha, O.; Riemis,
H.; Shappee, B.; Sobkowiak, K.; Sold'An, F.; Suys, D.; Szakats, R.;
Vantomme, J.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.;
Dudzin'ski, G.; Durech, J.; Castillo-Rogez, J.; Cipriani, F.; Fetick,
R.; Fusco, T.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy,
P.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier,
F.; Vigan, A.; Witasse, O.; Yang, B.
2019yCat..36330065H Altcode:
Deconvolved disk-resolved images of asteroid (704) Interamnia from
VLT/SPHERE/Zimpol instrument listed in Table A1. <P />(2 data files).
---------------------------------------------------------
Title: Validation of MHD Model Predictions of the Corona with LASCO-C2
Polarized Brightness Images
Authors: Lamy, Philippe; Floyd, Olivier; Mikić, Zoran; Riley, Pete
2019SoPh..294..162L Altcode:
Progress in our understanding of the solar corona requires that the
results of advanced magnetohydrodynamic models driven by measured
magnetic fields, and particularly the underlying heating models, be
thoroughly compared with coronal observations. The comparison has so far
mainly concerned the global morphology of the corona, synthetic images
calculated from the models being compared with observed images. We go
one step further by performing detailed quantitative comparisons between
the calculated polarized radiance p B using the three-dimensional
electron density produced by MHD models and well calibrated polarized
images obtained by the Large Angle Spectrometric Coronagraph LASCO-C2
coronagraph complemented by ground-based images when available from
the Mauna Loa Solar Observatory Mark IV and K-Cor instruments to extend
the comparison to the inner coronal region 1.0 - 2.5 <SUB>R⊙</SUB>,
which is inaccessible to C2. We take advantage of the high-resolution
and high-quality MHD predictions performed for several solar eclipses
(1 August 2008, 11 July 2010, 13 November 2012, and 21 August 2017) and
for the first perihelion passage of the Parker Solar Probe (5 November
2018) using two different three-dimensional MHD models relying on either
a thermodynamic or a wave-turbulence-driven methodologies to heat the
corona. Both models are generally able to match the observed structure
and photometry of the corona albeit with various degrees of fidelity for
which there is no obvious explanation. However, two limitations emerge,
the complexity of coronae of the maximum type and the time lapse between
the completion of the magnetograph measurements and the prediction.
---------------------------------------------------------
Title: Diurnal variation of dust and gas production in comet
67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS
and VIRTIS-M on board Rosetta
Authors: Tubiana, C.; Rinaldi, G.; Güttler, C.; Snodgrass, C.; Shi,
X.; Hu, X.; Marschall, R.; Fulle, M.; Bockelée-Morvan, D.; Naletto,
G.; Capaccioni, F.; Sierks, H.; Arnold, G.; Barucci, M. A.; Bertaux,
J. -L.; Bertini, I.; Bodewits, D.; Capria, M. T.; Ciarniello, M.;
Cremonese, G.; Crovisier, J.; Da Deppo, V.; Debei, S.; De Cecco, M.;
Deller, J.; De Sanctis, M. C.; Davidsson, B.; Doose, L.; Erard, S.;
Filacchione, G.; Fink, U.; Formisano, M.; Fornasier, S.; Gutiérrez,
P. J.; Ip, W. -H.; Ivanovski, S.; Kappel, D.; Keller, H. U.;
Kolokolova, L.; Koschny, D.; Krueger, H.; La Forgia, F.; Lamy, P. L.;
Lara, L. M.; Lazzarin, M.; Levasseur-Regourd, A. C.; Lin, Z. -Y.;
Longobardo, A.; López-Moreno, J. J.; Marzari, F.; Migliorini, A.;
Mottola, S.; Rodrigo, R.; Taylor, F.; Toth, I.; Zakharov, V.
2019A&A...630A..23T Altcode: 2019arXiv190503022T
Context. On 27 April 2015, when comet 67P/Churyumov-Gerasimenko was
at 1.76 au from the Sun and moving toward perihelion, the OSIRIS and
VIRTIS-M instruments on board the Rosetta spacecraft simultaneously
observed the evolving dust and gas coma during a complete rotation of
the comet. <BR /> Aims: We aim to characterize the spatial distribution
of dust, H<SUB>2</SUB>O, and CO<SUB>2</SUB> gas in the inner coma. To
do this, we performed a quantitative analysis of the release of dust
and gas and compared the observed H<SUB>2</SUB>O production rate with
the rate we calculated using a thermophysical model. <BR /> Methods:
For this study we selected OSIRIS WAC images at 612 nm (dust) and
VIRTIS-M image cubes at 612 nm, 2700 nm (H<SUB>2</SUB>O emission
band), and 4200 nm (CO<SUB>2</SUB> emission band). We measured the
average signal in a circular annulus to study the spatial variation
around the comet, and in a sector of the annulus to study temporal
variation in the sunward direction with comet rotation, both at a fixed
distance of 3.1 km from the comet center. <BR /> Results: The spatial
correlation between dust and water, both coming from the sunlit side
of the comet, shows that water is the main driver of dust activity in
this time period. The spatial distribution of CO<SUB>2</SUB> is not
correlated with water and dust. There is no strong temporal correlation
between the dust brightness and water production rate as the comet
rotates. The dust brightness shows a peak at 0° subsolar longitude,
which is not pronounced in the water production. At the same epoch,
there is also a maximum in CO<SUB>2</SUB> production. An excess of
measured water production with respect to the value calculated using
a simple thermophysical model is observed when the head lobe and
regions of the southern hemisphere with strong seasonal variations
are illuminated (subsolar longitude 270°-50°). A drastic decrease in
dust production when the water production (both measured and from the
model) displays a maximum occurs when typical northern consolidated
regions are illuminated and the southern hemisphere regions with
strong seasonal variations are instead in shadow (subsolar longitude
50°-90°). Possible explanations of these observations are presented
and discussed.
---------------------------------------------------------
Title: Rosetta/OSIRIS observations of the 67P nucleus during the
April 2016 flyby: high-resolution spectrophotometry
Authors: Feller, C.; Fornasier, S.; Ferrari, S.; Hasselmann,
P. H.; Barucci, A.; Massironi, M.; Deshapriya, J. D. P.; Sierks,
H.; Naletto, G.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson,
B. J. R.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.;
Da Deppo, V.; Debei, S.; De Cecco, M.; Fulle, M.; Gutiérrez, P. J.;
Güttler, C.; Ip, W. -H.; Keller, H. U.; Lara, L. M.; Lazzarin, M.;
López-Moreno, J. J.; Marzari, F.; Shi, X.; Tubiana, C.; Gaskell, B.;
La Forgia, F.; Lucchetti, A.; Mottola, S.; Pajola, M.; Preusker, F.;
Scholten, F.
2019A&A...630A...9F Altcode: 2018arXiv181209415F
Context. From August 2014 to September 2016, the Rosetta spacecraft
followed comet 67P/Churyumov-Gerasimenko along its orbit. After the
comet passed perihelion, Rosetta performed a flyby manoeuvre over the
Imhotep-Khepry transition in April 2016. The OSIRIS/Narrow-Angle-Camera
(NAC) acquired 112 observations with mainly three broadband filters
(centered at 480, 649, and 743 nm) at a resolution of up to 0.53
m/px and for phase angles between 0.095° and 62°. <BR /> Aims:
We have investigated the morphological and spectrophotometrical
properties of this area using the OSIRIS/NAC high-resolution
observations. <BR /> Methods: We assembled the observations into
coregistered color cubes. Using a 3D shape model, we produced the
illumination conditions and georeference for each observation. We
mapped the observations of the transition to investigate its
geomorphology. Observations were photometrically corrected using the
Lommel-Seeliger disk law. Spectrophotometric analyses were performed
on the coregistered color cubes. These data were used to estimate the
local phase reddening. <BR /> Results: The Imhotep-Khepry transition
hosts numerous and varied types of terrains and features. We observe
an association between a feature's nature, its reflectance, and its
spectral slopes. Fine material deposits exhibit an average reflectance
and spectral slope, while terrains with diamictons, consolidated
material, degraded outcrops, or features such as somber boulders present
a lower-than-average reflectance and higher-than-average spectral
slope. Bright surfaces present here a spectral behavior consistent
with terrains enriched in water-ice. We find a phase-reddening slope
of 0.064 ± 0.001%/100 nm/° at 2.7 au outbound, similar to the one
obtained at 2.3 au inbound during the February 2015 flyby. <BR />
Conclusions: Identified as the source region of multiple jets and a
host of water-ice material, the Imhotep-Khepry transition appeared in
April 2016, close to the frost line, to further harbor several potential
locations with exposed water-ice material among its numerous different
morphological terrain units.
---------------------------------------------------------
Title: Surface evolution of the Anhur region on comet
67P/Churyumov-Gerasimenko from high-resolution OSIRIS images
Authors: Fornasier, S.; Feller, C.; Hasselmann, P. H.; Barucci,
M. A.; Sunshine, J.; Vincent, J. -B.; Shi, X.; Sierks, H.; Naletto,
G.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Bertaux,
J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei,
S.; De Cecco, M.; Deller, J.; Ferrari, S.; Fulle, M.; Gutierrez,
P. J.; Güttler, C.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Lara,
M. L.; Lazzarin, M.; Lopez Moreno, J. J.; Lucchetti, A.; Marzari,
F.; Mottola, S.; Pajola, M.; Toth, I.; Tubiana, C.
2019A&A...630A..13F Altcode: 2019arXiv190309017F
Context. The southern hemisphere of comet 67P/Churyumov-Gerasimenko
(67P) became observable by the Rosetta mission in March 2015,
a few months before cometary southern vernal equinox. The Anhur
region in the southern part of the comet's larger lobe was found
to be highly eroded, enriched in volatiles, and highly active. <BR
/> Aims: We analyze high-resolution images of the Anhur region
pre- and post-perihelion acquired by the OSIRIS imaging system on
board the Rosetta mission. The Narrow Angle Camera is particularly
useful for studying the evolution in Anhur in terms of morphological
changes and color variations. <BR /> Methods: Radiance factor images
processed by the OSIRIS pipeline were coregistered, reprojected onto
the 3D shape model of the comet, and corrected for the illumination
conditions. <BR /> Results: We find a number of morphological changes
in the Anhur region that are related to formation of new scarps;
removal of dust coatings; localized resurfacing in some areas,
including boulders displacements; and vanishing structures, which
implies localized mass loss that we estimate to be higher than 50
million kg. The strongest changes took place in and nearby the Anhur
canyon-like structure, where significant dust cover was removed,
an entire structure vanished, and many boulders were rearranged. All
such changes are potentially associated with one of the most intense
outbursts registered by Rosetta during its observations, which occurred
one day before perihelion passage. Moreover, in the niche at the foot
of a new observed scarp, we also see evidence of water ice exposure
that persisted for at least six months. The abundance of water ice,
evaluated from a linear mixing model, is relatively high (>20%). Our
results confirm that the Anhur region is volatile-rich and probably is
the area on 67P with the most pristine exposures near perihelion. <P
/>The movies associated to Figs. 2, 7, 8, and 10 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/201834824/olm">https://www.aanda.org</A>
---------------------------------------------------------
Title: Linking surface morphology, composition, and activity on the
nucleus of 67P/Churyumov-Gerasimenko
Authors: Fornasier, S.; Hoang, V. H.; Hasselmann, P. H.; Feller,
C.; Barucci, M. A.; Deshapriya, J. D. P.; Sierks, H.; Naletto, G.;
Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Agarwal, J.;
Barbieri, C.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese,
G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Ferrari, S.;
Fulle, M.; Gutierrez, P. J.; Güttler, C.; Ip, W. -H.; Keller, H. U.;
Küppers, M.; La Forgia, F.; Lara, M. L.; Lazzarin, M.; Lin, Z. -Y.;
Lopez Moreno, J. J.; Marzari, F.; Mottola, S.; Pajola, M.; Shi, X.;
Toth, I.; Tubiana, C.
2019A&A...630A...7F Altcode: 2018arXiv180903997F
<BR /> Aims: The Rosetta space probe accompanied comet
67P/Churyumov-Gerasimenko for more than two years, obtaining an
unprecedented amount of unique data of the comet nucleus and inner
coma. This has enabled us to study its activity almost continuously
from 4 au inbound to 3.6 au outbound, including the perihelion passage
at 1.24 au. This work focuses identifying the source regions of faint
jets and outbursts and on studying the spectrophotometric properties of
some outbursts. We use observations acquired with the OSIRIS/NAC camera
during July-October 2015, that is, close to perihelion. <BR /> Methods:
We analyzed more than 2000 images from NAC color sequences acquired
with 7-11 filters covering the 250-1000 nm wavelength range. The
OSIRIS images were processed with the OSIRIS standard pipeline up to
level 3, that is, converted in radiance factor, then corrected for
the illumination conditions. For each color sequence, color cubes
were produced by stacking registered and illumination-corrected
images. <BR /> Results: More than 200 jets of different intensities
were identified directly on the nucleus. Some of the more intense
outbursts appear spectrally bluer than the comet dark terrain in the
visible-to-near-infrared region. We attribute this spectral behavior
to icy grains mixed with the ejected dust. Some of the jets have an
extremely short lifetime. They appear on the cometary surface during
the color sequence observations, and vanish in less than some few
minutes after reaching their peak. We also report a resolved dust plume
observed in May 2016 at a resolution of 55 cm pixel<SUP>-1</SUP>, which
allowed us to estimate an optical depth of ~0.65 and an ejected mass of
~2200 kg, assuming a grain bulk density of ~800 kg m<SUP>-3</SUP>. We
present the results on the location, duration, and colors of active
sources on the nucleus of 67P from the medium-resolution (i.e., 6-10
m pixel<SUP>-1</SUP>) images acquired close to perihelion passage. The
observed jets are mainly located close to boundaries between different
morphological regions. Some of these active areas were observed and
investigated at higher resolution (up to a few decimeter per pixel)
during the last months of operations of the Rosetta mission. <BR />
Conclusions: These observations allow us to investigate the link between
morphology, composition, and activity of cometary nuclei. Jets depart
not only from cliffs, but also from smooth and dust-covered areas,
from fractures, pits, or cavities that cast shadows and favor the
recondensation of volatiles. This study shows that faint jets or
outbursts continuously contribute to the cometary activity close to
perihelion passage, and that these events are triggered byillumination
conditions. Faint jets or outbursts are not associated with a particular
terrain type or morphology.
---------------------------------------------------------
Title: Seasonal variations in source regions of the dust jets on
comet 67P/Churyumov-Gerasimenko
Authors: Lai, I. -L.; Ip, W. -H.; Lee, J. -C.; Lin, Z. -Y.; Vincent,
J. -B.; Oklay, N.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.;
Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Barucci, M. A.;
Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese,
G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.;
Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler,
C.; Hofmann, M.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs,
G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin,
M.; López-Moreno, J. J.; Marzari, F.; Naletto, G.; Shi, X.; Tubiana,
C.; Thomas, N.
2019A&A...630A..17L Altcode:
<BR /> Aims: We investigate the surface distribution of the source
regions of dust jets on comet 67P/Churyumov-Gerasimenko as a
function of time. <BR /> Methods: The dust jet source regions were
traced by the comprehensive imaging data set provided by the OSIRIS
scientific camera. <BR /> Results: We show in detail how the projected
footpoints of the dust jets and hence the outgassing zone would move
in consonance with the sunlit belt. Furthermore, a number of source
regions characterized by repeated jet activity might be the result of
local topographical variations or compositional heterogeneities. <BR />
Conclusions: The spatial and temporal variations in source regions of
the dust jets are influenced significantly by the seasonal effect. The
strong dependence on the solar zenith angle and local time could be
related to the gas sublimation process driven by solar insolation on
a surface layer of low thermal inertia.
---------------------------------------------------------
Title: Pronounced morphological changes in a southern active zone
on comet 67P/Churyumov-Gerasimenko
Authors: Hasselmann, P. H.; Barucci, M. A.; Fornasier, S.;
Bockelée-Morvan, D.; Deshapriya, J. D. P.; Feller, C.; Sunshine,
J.; Hoang, V.; Sierks, H.; Naletto, G.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Davidsson, B.; Bertaux, J. -L.; Bertini, I.; Bodewits,
D.; Cremonese, G.; Da Deppo, V.; Debei, S.; Fulle, M.; Gutierrez,
P. J.; Güttler, C.; Deller, J.; Ip, W. -H.; Keller, H. U.; Lara,
L. M.; De Cecco, M.; Lazzarin, M.; López-Moreno, J. J. L.; Marzari,
F.; Shi, X.; Tubiana, C.
2019A&A...630A...8H Altcode:
A smooth deposit in the southern Khonsu region has been seen in
ESA/Rosetta observations as active during the second half of 2015,
when the southern summer coincided with the perihelion passage of
67P/Churyumov-Gerasimenko (67P). Image color sequences acquired by the
OSIRIS instrument in the period of January 2015 to July 2016, pre-
and post-perihelion, show the occurrence of several small transient
events as well as three massive outbursts ( 10 to 1500 tons). High
spatial resolution images taken one year and a half apart allowed
us to track a variety of sources: the formation of cavities that are
1.3-14 m deep, ice-enriched patches, scarp retraction, and a second
50 m-wide boulder. We then estimated their masses and the dust mass of
their corresponding plumes and outbursts. In particular, the deformation
left by that boulder and its lack of talus may provide evidence for the
lifting and subsequent falling back to the surface of large blocks. We
calculate that a minimum vapor production rate of 1.4 × 10<SUP>24</SUP>
m<SUP>-2</SUP> s<SUP>-1</SUP> is required to lift such an object. The
comparison of the masses that are lost in the new cavities to the
dust mass of outbursts gives indirect evidence of highly volatile
ice pockets underneath. The spectrophotometric analysis and boulder
counting also provides evidence for cavities that formed only 30 m
apart with different spectral slopes, two long-standing ice patches,
and local variations in the boulder-size frequency distribution. All
this points to sub-surface ice pockets with different degrees of
depth. Finally, the total mass of the morphological changes compared
to most recent calculations of the total released mass by activity on
67P is estimated to be between 1.5 and 4.2%. This means that as many
as about 25 similar active zones across the nucleus would be enough
to sustain the entire cometary activity.
---------------------------------------------------------
Title: Quantitative analysis of isolated boulder fields on comet
67P/Churyumov-Gerasimenko
Authors: Cambianica, P.; Cremonese, G.; Naletto, G.; Lucchetti, A.;
Pajola, M.; Penasa, L.; Simioni, E.; Massironi, M.; Ferrari, S.;
Bodewits, D.; La Forgia, F.; Sierks, H.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Davidsson, B.; Barucci, M. A.; Bertaux, J. -L.; Bertini,
I.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier,
S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Ip, W. -H.; Keller,
H. U.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.; López-Moreno, J. J.;
Marzari, F.; Mottola, S.; Shi, X.; Scholten, F.; Toth, I.; Tubiana,
C.; Vincent, J. -B.
2019A&A...630A..15C Altcode:
<BR /> Aims: We provide a detailed quantitative analysis of
isolated boulder fields situated in three different regions of comet
67P/Churyumov-Gerasimenko: Imhotep, Hapi, and Hatmehit. This is done
to supply a useful method for analyzing the morphology of the boulders
and to characterize the regions themselves. <BR /> Methods: We used
OSIRIS Narrow Angle Camera images with a spatial scale smaller than
2 m px<SUP>-1</SUP> and analyzed the size-frequency distribution and
the cumulative fractional area per boulder population. In addition,
we correlated shape parameters, such as circularity and solidity,
with both the spatial and the size-frequency distribution of the
three populations. <BR /> Results: We identified 11 811 boulders in
the Imhotep, Hapi, and Hatmehit regions. We found that the Hatmehit
and Imhotep areas show power indices in the range of -2.3/-2.7. These
values could represent a transition between gravitational events
caused by thermal weathering and sublimation, and material formed
during collapses that has undergone sublimation. The Hapi area is
characterized by a lower power index (-1.2/-1.7), suggesting that those
boulders have a different origin. They can be the result of material
formed during gravitational events and collapses that has undergone
continuous fragmentation. We calculated the cumulative fractional area
(CFA) in order to investigate how the area is covered by boulders as a
function of their sizes. The Hatmehit and Imhotep regions show a CFA
that is well fit by a power law. In contrast, the Hapi area does not
show the same trend. We analyzed the fractal distributions, finding that
the populations seem to be fractal at all dimensions, except for the
Hapi distribution, which shows a possible fractal behavior for small
dimensions only. Finally, the average values of the shape parameters
reveal solid and roundish boulders in all populations we studied.
---------------------------------------------------------
Title: Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at
small phase angles
Authors: Masoumzadeh, N.; Kolokolova, L.; Tubiana, C.; El-Maarry,
M. R.; Mottola, S.; Güttler, C.; Snodgrass, C.; Sierks, H.; Naletto,
G.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Barucci,
M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.;
Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.;
Fulle, M.; Gutiérrez, P. J.; Hasselmann, P. H.; Ip, W. -H.; Keller,
H. U.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.;
Shi, X.; Toth, I.
2019A&A...630A..11M Altcode:
<BR /> Aims: The Rosetta-OSIRIS images acquired at small phase angles
in three wavelengths during the fly-by of the spacecraft on 9-10
April 2016 provided a unique opportunity to study the opposition
effect on the surface of comet 67P/Churyumov-Gerasimenko (67P). Our
goal is to study phase curves of the nucleus at small phase angles
for a variety of surface structures to show the differences in their
opposition effect and to determine which surface properties cause the
differences. <BR /> Methods: We used OSIRIS NAC images that cover the
Ash-Khepry-Imhotep region to extract the phase curve, that is, the
reflectance of the surface as a function of phase angle. We selected
six regions of interest (ROIs) and derived the phase curves for each
ROI. We fit a linear-exponential function to the phase curves. The
resulting model parameters were then interpreted by spectrophotometric,
geomorphological, and phase-ratio analyses, and by investigating the
influence of structural and textural properties of the surface. <BR />
Results: We find evidence for the opposition effect (deviation of the
phase curve from linear behavior) in phase curves for all areas. We
found an anticorrelation between the phase ratio and reflectance in a
small phase angle range. This provides evidence for the shadow-hiding
effect. We conclude that the decrease in the slope of the phase ratio
versus reflectance indicates a decrease in the proportion of shadowed
regions and reduces the contribution of the shadow-hiding effect. Large
uncertainties in the determination of the opposition effect parameters
with respect to wavelength do not allow us to conclusively claim
coherent backscattering in the opposition effect phenomenon. Based on
the two analyses, we conclude that the opposition effect of comet 67P
in the Ash-Khepry-Imhotep region is mainly affected by shadow-hiding.
---------------------------------------------------------
Title: Spectrophotometric variegation of the layering in comet
67P/Churyumov-Gerasimenko as seen by OSIRIS
Authors: Tognon, G.; Ferrari, S.; Penasa, L.; La Forgia, F.; Massironi,
M.; Naletto, G.; Lazzarin, M.; Cambianica, P.; Lucchetti, A.; Pajola,
M.; Ferri, F.; Güttler, C.; Davidsson, B.; Deshapriya, P.; Fornasier,
S.; Mottola, S.; Tóth, I.; Sierks, H.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Bertini,
I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco,
M.; Deller, J.; Franceschi, M.; Frattin, E.; Fulle, M.; Gutiérrez,
P. J.; Ip, W. -H.; Keller, H. U.; Lara, L. M.; López-Moreno, J. J.;
Marzari, F.; Petropoulou, V.; Shi, X.; Tubiana, C.
2019A&A...630A..16T Altcode:
Context. Between August 2014 and September 2016, the ESA space
mission Rosetta escorted comet 67P/Churyumov-Gerasimenko (67P)
during its perihelion passage. The onboard OSIRIS Narrow Angle
Camera (NAC) acquired high-resolution multispectral images of the
cometary surface. These datasets allowed a characterization of
the spectrophotometric variegation of the layering of the large
lobe, correlated with the layer structural elevation. <BR /> Aims:
We perform a spectrophotometric characterization of the outcropping
stratification of the small lobe of 67P as a function of its structural
elevation, and consequently, a spectrophotometric comparison of the
layered outcrops of the two lobes. <BR /> Methods: We selected two
sequences of post-perihelion OSIRIS NAC images ( 2.4 au outbound
tothe Sun), from which we built up two multispectral images, framing
an extended geological section of the onion-like stratification of
the small lobe. Then we classified the consolidated areas of the
outcropping and the relative coarse deposits that were identified
in the multispectral data with a two-class maximum likelihood
method. For this, we defined the classes as a function of the
structural elevation of the surface. <BR /> Results: As a result,
we identified a brightness variegation of the surface reflectance
that is correlated with the structural elevation. The outer class,
which is located at higher elevations, appears darker than the
inner class. This fits previously obtained results for the large
lobe. The reflectance values of the nucleus of 67P tend to decrease
with increasing structural elevation. <BR /> Conclusions: The observed
spectrophotometric variegation can be due to a different texture as well
as to a different content of volatiles and refractories. We suggest
that the outer outcrops appear darker because they have been exposed
longer, and the inner outcrops appear brighter because the surface
has been more effectively rejuvenated. We interpret this variegation
as the result of an evolutionary process.
---------------------------------------------------------
Title: A catalog of stereo anaglyphs of comet
67P/Churyumov-Gerasimenko - Application to the detection of deep
ice pits
Authors: Lamy, Philippe; Faury, Guillaume; Romeuf, David; Groussin,
Olivier; Durand, Joelle
2019EPSC...13..719L Altcode:
The OSIRIS/NAC camera aboard the Rosetta spacecraft has acquired
approximately 27000 images of comet 67P/Churyumov-Gerasimenko at spatial
scales down to a few centimeters. We exploit the numerous sequences of
images separated by a few minutes suitable for stereo reconstructions
to produce anaglyphs offering three-dimensional views of the comet,
complementary to other technics, as a tool to understand the topography
of the nucleus. Each anaglyph is documented by a set of 17 parameters
which provide the contextual information. Over 1400 anaglyphs have
been produced and cataloged so far; they are available on a dedicated
website and can be searched using the associated parameters. As
a first application, we present direct evidences of sub-surface
ice at the bottom of deep pits, so-called "ice pits" identified on
high-resolution anaglyphs. Their geometry and size are obtained from
stereographic reconstruction. Both their high reflectivity and their
blue color substantiate the presence of ice.
---------------------------------------------------------
Title: Coronal Mass Ejections over Solar Cycles 23 and 24
Authors: Lamy, P. L.; Floyd, O.; Boclet, B.; Wojak, J.; Gilardy, H.;
Barlyaeva, T.
2019SSRv..215...39L Altcode:
We present a statistical analysis of solar coronal mass ejections
(CMEs) based on 23 years of quasi-continuous observations with the
LASCO coronagraph, thus covering two complete Solar Cycles (23 and
24). We make use of five catalogs, one manual (CDAW) and four automated
(ARTEMIS, CACTus, SEEDS, and CORIMP), to characterize the temporal
evolutions and distributions of their properties: occurrence and mass
rates, waiting times, periodicities, angular width, latitude, speed,
acceleration and kinetic energy. Our analysis points to inevitable
discrepancies between catalogs due to the complex nature of CMEs and to
the different techniques implemented to detect them, but also to large
areas of convergence that are critically important to ascertain the
reliability of the results. The temporal variations of these properties
are compared to four indices/proxies of solar activity: the radio
flux at 10.7 cm (F10.7), the international sunspot number (SSN), the
sunspot area (SSA), and the total magnetic field (TMF), either globally
or separately in the northern and southern hemispheres in the case of
the last three. We investigate the association of CMEs with flares,
erupting prominences, active regions and streamers. We find that the
CME occurrence and mass rates globally track the indices/proxies of
solar activity with no time lag, prominently the radio flux F10.7, but
the linear relationships were different during the two solar cycles,
implying that the CME rates were relatively larger during SC 24 than
during SC 23. However, there exists a pronounced divergence of the
CME rates in the northern hemisphere during SC 24 as these rates were
substantially larger than predicted by the temporal variation of the
sunspot number. The distribution of kinetic energy follows a log-normal
law and that of angular width follows an exponential law implying that
they are random and independent. The distribution of waiting time
(WTD) has a long power-law tail extending from 3 to 100 hr with a
power-law index which varies with the solar cycle, thus reflecting
the temporal variability of the process of CME formation. There is
very limited evidence for periodicities in the occurrence and mass
rates of CMEs, a striking feature being the dichotomy between the two
hemispheres. Rather weak correlations are present among the various CME
parameters and particularly none between speed and acceleration. The
association of CMEs with flares and erupting prominences involves only
a few percents of the overall population of CMEs but the associated
CMEs have distinctly larger mass, speed, kinetic energy and angular
width. A more pronounced association is found with active regions
but the overwhelming one is with streamers further confirmed by the
similarity between the heliolatitudinal distribution of CMEs and that
of the electron density reconstructed from time-dependent tomographic
inversion. We find no evidence of bimodality in the distributions of
physical parameters that would support the existence of two classes,
particularly that based on speed and acceleration, the distributions
thus favoring a continuum of properties. There exists an excess of
narrows CMEs which however does not define a special class. These
narrow CMEs are likely associated with the ubiquitous mini-filaments
eruptions and with mini flux ropes originating from small magnetic
bipoles, the disruption mechanisms being similar to those launching
larger CMEs. This supports the concept that CMEs at large arise from
closed-field coronal regions at both large and small scales.
---------------------------------------------------------
Title: Tomography of the Solar Corona with the Wide-Field Imager
for the Parker Solar Probe
Authors: Vásquez, Alberto M.; Frazin, Richard A.; Vourlidas, Angelos;
Manchester, Ward B.; van der Holst, Bart; Howard, Russell A.; Lamy,
Philippe
2019SoPh..294...81V Altcode:
The Wide-field Imager for the Parker Solar Probe (PSP/WISPR) comprises
two telescopes that record white-light total brightness [B ] images of
the solar corona. Their fields of view cover a widely changing range
of heliocentric heights over the 24 highly eccentric orbits planned for
the mission. In this work, the capability of PSP/WISPR data to carry out
tomographic reconstructions of the three-dimensional (3D) distribution
of the coronal electron density is investigated. Based on the precise
orbital information of the mission, B -images for Orbits 1, 12, and 24
are synthesized from a 3D magnetohydrodynamic model of the corona. For
each orbit, the time series of synthetic images is used to carry out a
tomographic reconstruction of the coronal electron density and results
are compared with the model. As the PSP perihelion decreases, the range
of heights that can be tomographically reconstructed progressively
shifts to lower values, and the period required to gather the data
decreases. For Orbit 1 tomographic reconstruction is not possible. For
Orbit 12, tomographic reconstruction is possible in the heliocentric
height range ≈5 -15 R<SUB>⊙</SUB>, over a region spanning up to
≈160<SUP>∘</SUP> in Carrington longitude, with data gathered over
a ≈3.4 day-long period. For Orbit 24, tomographic reconstruction is
possible in the heliocentric height range ≈3 -10 R<SUB>⊙</SUB>, over
a region spanning up to ≈170<SUP>∘</SUP> in Carrington longitude,
with data gathered over a ≈2.8 day-long period.
---------------------------------------------------------
Title: Multidisciplinary analysis of the Hapi region located on
Comet 67P/Churyumov-Gerasimenko
Authors: Pajola, M.; Lee, J. -C.; Oklay, N.; Hviid, S. F.; Penasa, L.;
Mottola, S.; Shi, X.; Fornasier, S.; Davidsson, B.; Giacomini, L.;
Lucchetti, A.; Massironi, M.; Vincent, J. B.; Bertini, I.; Naletto,
G.; Ip, W. H.; Sierks, H.; Lamy, P. L.; Rodrigo, R.; Koschny, D.;
Keller, H. U.; Agarwal, J.; Barucci, M. A.; Bertaux, J. L.; Bodewits,
D.; Cambianica, P.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco,
M.; Deller, J.; El Maarry, M. R.; Feller, C.; Ferrari, S.; Fulle, M.;
Gutierrez, P. J.; Güttler, C.; Lara, L. M.; La Forgia, F.; Lazzarin,
M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Marzari, F.; Preusker, F.;
Scholten, F.; Toth, I.; Tubiana, C.
2019MNRAS.485.2139P Altcode:
By using the Rosetta/OSIRIS-NAC data set taken in 2014 August, we focus
on the neck region, called Hapi, located on 67P Churyumov-Gerasimenko's
Northern hemisphere. The gravitational potential and slopes of Hapi,
coupled with the geological unit identification and the boulder
size-frequency distributions, support the interpretation that both
taluses and gravitational accumulation deposits observable on Hapi
are the result of multiple cliff collapses that occurred at different
times. By contrast, the fine-particle deposits observable in the
central part of the study area are made of aggregates coming from the
Southern hemisphere and deposited during each perihelion passage. Both
the consolidated terrains on the western part of Hapi, as well as the
centrally aligned ridge made of boulder-like features, suggest that
Hapi is in structural continuity with the onion-like structure of
the main lobe of 67P. Despite the dusty blanket observable on Hapi,
its terrains are characterized by water-ice-rich components that,
once repeatedly and rapidly illuminated, sublimate, hence resulting
in the strong jet activity observed in 2014 August.
---------------------------------------------------------
Title: The shape of (7) Iris as evidence of an ancient large impact?
Authors: Hanuš, J.; Marsset, M.; Vernazza, P.; Viikinkoski, M.;
Drouard, A.; Brož, M.; Carry, B.; Fetick, R.; Marchis, F.; Jorda, L.;
Fusco, T.; Birlan, M.; Santana-Ros, T.; Podlewska-Gaca, E.; Jehin, E.;
Ferrais, M.; Grice, J.; Bartczak, P.; Berthier, J.; Castillo-Rogez,
J.; Cipriani, F.; Colas, F.; Dudziński, G.; Dumas, C.; Ďurech,
J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.;
Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.;
Vachier, F.; Vigan, A.; Witasse, O.; Yang, B.
2019A&A...624A.121H Altcode: 2019arXiv190209242H
Context. Asteroid (7) Iris is an ideal target for disk-resolved imaging
owing to its brightness (V 7-8) and large angular size of 0.33”
during its apparitions. Iris is believed to belong to the category of
large unfragmented asteroids that avoided internal differentiation,
implying that its current shape and topography may record the first
few 100 Myr of the solar system's collisional evolution. <BR /> Aims:
We recovered information about the shape and surface topography of
Iris from disk-resolved VLT/SPHERE/ZIMPOL images acquired in the
frame of our ESO large program. <BR /> Methods: We used the All-Data
Asteroid Modeling (ADAM) shape reconstruction algorithm to model the
3D shape of Iris, using optical disk-integrated data and disk-resolved
images from SPHERE and earlier AO systems as inputs. We analyzed the
SPHERE images and our model to infer the asteroid's global shape and
the morphology of its main craters. <BR /> Results: We present the
3D shape, volume-equivalent diameter D<SUB>eq</SUB> = 214 ± 5 km,
and bulk density ρ = 2.7 ± 0.3 g cm<SUP>-3</SUP> of Iris. Its shape
appears to be consistent with that of an oblate spheroid with a large
equatorial excavation. We identified eight putative surface features
20-40 km in diameter detected at several epochs, which we interpret
as impact craters, and several additional crater candidates. Craters
on Iris have depth-to-diameter ratios that are similar to those of
analogous 10 km craters on Vesta. <BR /> Conclusions: The bulk density
of Iris is consistent with that of its meteoritic analog based on
spectroscopic observations, namely LL ordinary chondrites. Considering
the absence of a collisional family related to Iris and the number of
large craters on its surface, we suggest that its equatorial depression
may be the remnant of an ancient (at least 3 Gyr) impact. Iris's shape
further opens the possibility that large planetesimals formed as almost
perfect oblate spheroids. Finally, we attribute the difference in crater
morphology between Iris and Vesta to their different surface gravities,
and the absence of a substantial impact-induced regolith on Iris. <P
/>The reduced images are only available at the CDS via anonymous ftp to
<A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A121">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A121</A>Based
on observations made with ESO Telescopes at the Paranal Observatory
under programme ID 199.C-0074 (PI: P. Vernazza) and 086.C-0785 (PI:
B. Carry).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Asteroid (7) Iris Deconvolved
disk-resolved images (Hanus+, 2019)
Authors: Hanus, J.; Marsset, M.; Vernazza, P.; Viikinkoski, M.;
Drouard, A.; Broz, M.; Carry, B.; Fetick, R.; Marchis, F.; Jorda, L.;
Fusco, T.; Birlan, M.; Santana-Ros, T.; Podlewska-Gaca, E.; Jehin, E.;
Ferrais, M.; Grice, J.; Bartczak, P.; Berthier, J.; Castillo-Rogez,
J.; Cipriani, F.; Colas, F.; Dudzinski, G.; Dumas, C.; Durech,
J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.;
Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.;
Vachier, F.; Vigan, A.; Witasse, O.; Yang, B.
2019yCat..36240121H Altcode:
Deconvolved disk-resolved images of asteroid (7) Iris from Keck/Nirc2,
VLT/NaCo and VLT/SPHERE/Zimpol instruments listed in Table C.2. The
final shape model is based on the VLT/SPHERE/Zimpol data and a subset of
the Keck/Nirc2 and VLT.NaCo data. The remaining data of a poor quality,
often affected by deconvolution artifact, were used for consistency
check only. The ordering of the data corresponds to the ordering in
Table C2. <P />(2 data files).
---------------------------------------------------------
Title: VizieR Online Data Catalog: SPHERE/ZIMPOL (41) Daphne images
(Carry+, 2019)
Authors: Carry, B.; Vachier, F.; Berthier, J.; Marsset, M.; Vernazza,
P.; Grice, J.; Merline, W. J.; Lagadec, E.; Fienga, A.; Conrad, A.;
Podlewska-Gaca, E.; Santana-Ros, T.; Viikinkoski, M.; Hanus, J.;
Dumas, C.; Drummond, J. D.; Tamblyn, P. M.; Chapman, C. R.; Behrend,
R.; Bernasconi, L.; Bartczak, P.; Benkhaldoun, Z.; Birlan, M.;
Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Drouard, A.; Durech, J.;
Enke, B. L.; Fauvaud, S.; Ferrais, M.; Fetick, R.; Fusco, T.; Gillon,
M.; Jehin, E.; Jorda, L.; Kaasalainen, M.; Keppler, M.; Kryszczynska,
A.; Lamy, P.; Marchis, F.; Marciniak, A.; Michalowski, T.; Michel,
P.; Pajuelo, M.; Tanga, P.; Vigan, A.; Warner, B.; Witasse, O.; Yang,
B.; Zurlo, A.
2019yCat..36230132C Altcode:
Daphne was observed with the SPHERE instrument (ESO/VLT) around its
opposition at eight different epochs. We used ZIMPOL in narrowband
imaging mode (N_R filter; filter central wavelength = 645.9nm, width
= 56.7nm). Each observational sequence consisted of a series of
five images, where each image corresponded to a series of detector
integration times (DITs) of 10s, during which Julia was used as a
natural guide star for adaptive optics (AO) corrections. Observations
were performed under good seeing conditions (<=0.8") with an airmass
usually below 1.6. After every asteroid observation, we observed a
nearby star for deconvolution purposes to estimate the instrument point
spread function (PSF). Finally, standard calibrations, which include
detector flat-fields and darks, were acquired in the morning as part
of the instrument calibration plan. <P />For a full description of the
parameters, see: https://astro.troja.mff.cuni.cz/projects/asteroids3D/\
web.php?page=db_description and Durech
et al. (2010A&A...513A..46D) <P />object:
-------------------------------------------------------------------
Planet Name H Diam i e a mag km deg AU
-------------------------------------------------------------------
41 Daphne 7.12 187.0 15.792100 0.27541753 2.76043870
-------------------------------------------------------------------
<P />(5 data files).
---------------------------------------------------------
Title: Closing the gap between Earth-based and interplanetary mission
observations: Vesta seen by VLT/SPHERE
Authors: Fétick, R. JL.; Jorda, L.; Vernazza, P.; Marsset,
M.; Drouard, A.; Fusco, T.; Carry, B.; Marchis, F.; Hanuš,
J.; Viikinkoski, M.; Birlan, M.; Bartczak, P.; Berthier, J.;
Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dudziński, G.; Dumas, C.;
Ferrais, M.; Jehin, E.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.;
Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Mugnier,
L. M.; Neichel, B.; Pajuelo, M.; Podlewska-Gaca, E.; Santana-Ros,
T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B.
2019A&A...623A...6F Altcode: 2019arXiv190201287F
Context. Over the past decades, several interplanetary missions
have studied small bodies in situ, leading to major advances in our
understanding of their geological and geophysical properties. These
missions, however, have had a limited number of targets. Among them,
the NASA Dawn mission has characterised in detail the topography and
albedo variegation across the surface of asteroid (4) Vesta down
to a spatial resolution of ~20 m pixel<SUP>-1</SUP> scale. <BR />
Aims: Here our aim was to determine how much topographic and albedo
information can be retrieved from the ground with VLT/SPHERE in the
case of Vesta, having a former space mission (Dawn) providing us with
the ground truth that can be used as a benchmark. <BR /> Methods:
We observed Vesta with VLT/SPHERE/ZIMPOL as part of our ESO large
programme (ID 199.C-0074) at six different epochs, and deconvolved
the collected images with a parametric point spread function (PSF). We
then compared our images with synthetic views of Vesta generated from
the 3D shape model of the Dawn mission, on which we projected Vesta's
albedo information. <BR /> Results: We show that the deconvolution of
the VLT/SPHERE images with a parametric PSF allows the retrieval of
the main topographic and albedo features present across the surface of
Vesta down to a spatial resolution of ~20-30 km. Contour extraction
shows an accuracy of ~1 pixel (3.6 mas). The present study provides
the very first quantitative estimate of the accuracy of ground-based
adaptive-optics imaging observations of asteroid surfaces. <BR />
Conclusions: In the case of Vesta, the upcoming generation of
30-40 m telescopes (ELT, TMT, GMT) should in principle be able
to resolve all of the main features present across its surface,
including the troughs and the north-south crater dichotomy, provided
that they operate at the diffraction limit. <P />Reduced images of
Table A.1 are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A6">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A6</A>
<P />Based on observations made with ESO Telescopes at the Paranal
Observatory under programme ID 199.C-0074 (PI: P. Vernazza).
---------------------------------------------------------
Title: Homogeneous internal structure of CM-like asteroid (41) Daphne
Authors: Carry, B.; Vachier, F.; Berthier, J.; Marsset, M.; Vernazza,
P.; Grice, J.; Merline, W. J.; Lagadec, E.; Fienga, A.; Conrad, A.;
Podlewska-Gaca, E.; Santana-Ros, T.; Viikinkoski, M.; Hanuš, J.;
Dumas, C.; Drummond, J. D.; Tamblyn, P. M.; Chapman, C. R.; Behrend,
R.; Bernasconi, L.; Bartczak, P.; Benkhaldoun, Z.; Birlan, M.;
Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Drouard, A.; Ďurech, J.;
Enke, B. L.; Fauvaud, S.; Ferrais, M.; Fetick, R.; Fusco, T.; Gillon,
M.; Jehin, E.; Jorda, L.; Kaasalainen, M.; Keppler, M.; Kryszczynska,
A.; Lamy, P.; Marchis, F.; Marciniak, A.; Michalowski, T.; Michel,
P.; Pajuelo, M.; Tanga, P.; Vigan, A.; Warner, B.; Witasse, O.; Yang,
B.; Zurlo, A.
2019A&A...623A.132C Altcode: 2019arXiv190101890C
Context. CM-like asteroids (Ch and Cgh classes) are a major population
within the broader C-complex, encompassing about 10% of the mass of
the main asteroid belt. Their internal structure has been predicted to
be homogeneous, based on their compositional similarity as inferred
from spectroscopy and numerical modeling of their early thermal
evolution. <BR /> Aims: Here we aim to test this hypothesis by deriving
the density of the CM-like asteroid (41) Daphne from detailed modeling
of its shape and the orbit of its small satellite. <BR /> Methods:
We observed Daphne and its satellite within our imaging survey with
the Very Large Telescope extreme adaptive-optics SPHERE/ZIMPOL camera
and complemented this data set with earlier Keck/NIRC2 and VLT/NACO
observations. We analyzed the dynamics of the satellite with our
Genoid meta-heuristic algorithm. Combining our high-angular resolution
images with optical lightcurves and stellar occultations, we determine
the spin period, orientation, and 3D shape, using our ADAM shape
modeling algorithm. <BR /> Results: The satellite orbits Daphne on an
equatorial, quasi-circular, prograde orbit, like the satellites of many
other large main-belt asteroids. The shape model of Daphne reveals
several large flat areas that could be large impact craters. The
mass determined from this orbit combined with the volume computed
from the shape model implies a density for Daphne of 1.77 ± 0.26 g
cm<SUP>-3</SUP> (3 σ). This densityis consistent with a primordial
CM-like homogeneous internal structure with some level of macroporosity
(≈ 17%). <BR /> Conclusions: Based on our analysis of the density
of Daphne and 75 other Ch/Cgh-type asteroids gathered from the
literature, we conclude that the primordial internal structure of the
CM parent bodies was homogeneous. <P />Based on observations made with
(1) ESO Telescopes at the La Silla Paranal Observatory under programs <A
href="http://archive.eso.org/wdb/wdb/eso/sched_rep_arc/query?progid=281.C-5011(A)">http://281.C-5011</A>
(PI Dumas), <A
href="http://archive.eso.org/wdb/wdb/eso/sched_rep_arc/query?progid=099.D-0098(A)">http://099.D-0098</A>
(SPHERE GTO), and <A
href="http://archive.eso.org/wdb/wdb/eso/abstract/query?progid=199.C-0074(A)">http://199.C-0074(A)</A>
(PI Vernazza); and (2) the W. M. Keck Observatory, which is
operated as a scientific partnership among the California
Institute of Technology, the University of California
and the National Aeronautics and Space Administration. The
Observatory was made possible by the generous financial support
of the W. M. Keck Foundation.The reduced and deconvolved
AO images and the 3D shape model are publicly available at <A
href="http://observations.lam.fr/astero/">http://observations.lam.fr/astero/</A>
and at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A132">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A132</A>
---------------------------------------------------------
Title: A catalog of stereo anaglyphs of the nucleus of comet
67P/Churyumov-Gerasimenko
Authors: Lamy, Philippe; Faury, Guillaume; Romeuf, David; Groussin,
Olivier; Durand, Joelle; Beigbeder, Laurent; Khum, Kea
2019arXiv190302324L Altcode:
The OSIRIS/NAC camera onboard the Rosetta spacecraft acquired
approximately 27000 images of comet 67PChuryumov-Gerasimenko at spatial
scales down to a few centimeters. Numerous sequences of images separated
by a few minutes suitable to stereo reconstruction allowed producing
anaglyphs. They offer three-dimensional views complementary to other
technics as a tool to understand the topography of the nucleus. Each
one is documented by a set of 17 parameters. Over 1820 anaglyphs are
available on a dedicated website at https://rosetta-3dcomet.cnes.fr
---------------------------------------------------------
Title: VizieR Online Data Catalog: VLT/SPHERE/ZIMPOL images of Vesta
(Fetick+, 2019)
Authors: Fetick, R. J.; Jorda, L.; Vernazza, P.; Marsset, M.; Drouard,
A.; Fusco, T.; Carry, B.; Marchis, F.; Hanus, J.; Viikinkoski,
M.; Birlan, M.; Bartczak, P.; Berthier, J.; Castillo-Rogez, J.;
Cipriani, F.; Colas, F.; Dudzinski, G.; Dumas, C.; Ferrais, M.; Jehin,
E.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.;
Marciniak, A.; Michalowski, T.; Michel, P.; Mugnier, L. M.; Neichel,
B.; Pajuelo, M.; Podlewska-Gaca, E.; Santana-Ros, T.; Tanga, P.;
Vachier, F.; Vigan, A.; Witasse, O.; Yang, B.
2019yCat..36230006F Altcode:
Vesta observations with VLT/SPHERE/ZIMPOL as part of the ESO
large programme (ID 199.C-0074, PI: P.Vernazza) at six different
epochs. The provided data is a set of images in FITS format,
whose names correspond to the SPHERE observation times. Each image
is of size 1024x1024 pixels. ESO header for each FITS provides
information about the observation. Note that many observations
are available for each of the six epochs. <P />object.dat :
--------------------------------------------------------------------
Planet Name H Diam i e a mag km deg AU
--------------------------------------------------------------------
4 Vesta 3.20 468.3 7.141840 0.08874248 2.36126876 <P />(2 data files).
---------------------------------------------------------
Title: The backscattering ratio of comet 67P/Churyumov-Gerasimenko
dust coma as seen by OSIRIS onboard Rosetta
Authors: Bertini, I.; La Forgia, F.; Fulle, M.; Tubiana, C.; Güttler,
C.; Moreno, F.; Agarwal, J.; Munoz, O.; Mottola, S.; Ivanovsky, S.;
Pajola, M.; Lucchetti, A.; Petropoulou, V.; Lazzarin, M.; Rotundi,
A.; Bodewits, D.; Frattin, E.; Toth, I.; Masoumzadeh, N.; Kovacs,
G.; Rinaldi, G.; Guirado, D.; Sierks, H.; Naletto, G.; Lamy, P.;
Rodrigo, R.; Koschny, D.; Davidsson, B.; Barbieri, C.; Barucci, M. A.;
Bertaux, J. -L.; Cambianica, P.; Cremonese, G.; Da Deppo, V.; Debei,
S.; De Cecco, M.; Deller, J.; Ferrari, S.; Ferri, F.; Fornasier, S.;
Gutierrez, P. J.; Hasselmann, P. H.; Ip, W. -H.; Keller, H. U.; Lara,
L. M.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Penasa, L.;
Shi, X.
2019MNRAS.482.2924B Altcode: 2018MNRAS.tmp.2714B
Remote sensing observations of dust particles ejected from comets
provide important hints on the intimate nature of the materials
composing these primitive objects. The measurement of dust coma
backscattering ratio, BSR, defined as the ratio of the reflectance at
phase angle 0° and 30°, helps tuning theoretical models aimed at
solving the inverse scattering problem deriving information on the
nature of the ejected particles. The Rosetta/OSIRIS camera sampled
the coma phase function of comet 67P, with four series acquired at low
phase angles from 2015 January to 2016 May. We also added previously
published data to our analysis to increase the temporal resolution of
our findings. We measured a BSR in the range ∼ [1.7-3.6], broader
than the range found in literature from ground-based observations of
other comets. We found that during the post-perihelion phase, the BSR
is systematically larger than the classical cometary dust values only
for nucleocentric distances smaller than ∼100 km. We explain this
trend in terms of a cloud of chunks orbiting the nucleus at distances
<100 km ejected during perihelion and slowly collapsing on the
nucleus over a few months because of the coma gas drag. This also
implies that the threshold particle size for the dust phase function
to become similar to the nucleus phase function is between 2.5 mm and
0.1 m, taking into account previous Rosetta findings.
---------------------------------------------------------
Title: Three-Dimensional Views of the Nucleus of Comet
67P/Churyumov-Gerasimenko - Application to the Characterization of
Active Pits
Authors: Lamy, P.; Faury, G.; Romeuf, D.; Groussin, O.; Nebouy, D.
2018AGUFM.P23G3522L Altcode:
The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard
ESA's Rosetta spacecraft has acquired approximately 25000 images of the
surface of the nucleus of comet 67P/Churyumov-Gerasimenko at various
spatial scales down to centimeters per pixel. The bulk of these images
have been obtained in sequences and the combined displacement of the
Rosetta orbiter along its trajectory and the rotation of the nucleus
allow associating many pairs of images appropriate to stereoscopic
viewing. This is achieved by constructing anaglyphs after rotating
the images so that the relative shift appears horizontal. The shift
is set to limit the parallax to approximately 2° (with a maximum
value of 4°) for the foreground so as to avoid image deformation. A
time of writing, approximately 1100 anaglyphs have been produced. In
addition to offering spectacular stereoscopic views of the nucleus,
these anaglyphs allow studying the topography of the nucleus at spatial
scales unachievable by DTMs. Further coupling with spectral images,
we have been able to locate ice patches at the bottom of several narrow
pits which indicate the presence of sub-surface ice at depths of a few
meters. These narrow pits are most likely the sources of collimated
jets widely seen in the coma of 67PC-G.
---------------------------------------------------------
Title: Regional unit definition for the nucleus of comet
67P/Churyumov-Gerasimenko on the SHAP7 model
Authors: Thomas, N.; El Maarry, M. R.; Theologou, P.; Preusker,
F.; Scholten, F.; Jorda, L.; Hviid, S. F.; Marschall, R.; Kührt,
E.; Naletto, G.; Sierks, H.; Lamy, P. L.; Rodrigo, R.; Koschny, D.;
Davidsson, B.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Bodewits,
D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier,
S.; Fulle, M.; Groussin, O.; Gutièrrez, P. J.; Güttler, C.; Ip,
W. H.; Keller, H. U.; Knollenberg, J.; Lara, L. M.; Lazzarin, M.;
Lòpez-Moreno, J. J.; Marzari, F.; Tubiana, C.; Vincent, J. B.
2018P&SS..164...19T Altcode:
The previously defined regions on the nucleus of comet
67P/Churyumov-Gerasimenko have been mapped back onto the 3D SHAP7
model of the nucleus (Preusker et al., 2017). The resulting regional
definition is therefore self-consistent with boundaries that are well
defined in 3 dimensions. The facets belonging to each region are
provided as supplementary material. The shape model has then been
used to assess inhomogeneity of nucleus surface morphology within
individual regions. Several regions show diverse morphology. We
propose sub-division of these regions into clearly identifiable units
(sub-regions) and a comprehensive table is provided. The surface
areas of each sub-region have been computed and statistics based on
grouping of unit types are provided. The roughness of each region is
also provided in a quantitative manner using a technique derived from
computer graphics applications. The quantitative method supports the
sub-region definition by showing that differences between sub-regions
can be numerically justified.
---------------------------------------------------------
Title: (16) Psyche: A mesosiderite-like asteroid?
Authors: Viikinkoski, M.; Vernazza, P.; Hanuš, J.; Le Coroller,
H.; Tazhenova, K.; Carry, B.; Marsset, M.; Drouard, A.; Marchis,
F.; Fetick, R.; Fusco, T.; Ďurech, J.; Birlan, M.; Berthier, J.;
Bartczak, P.; Dumas, C.; Castillo-Rogez, J.; Cipriani, F.; Colas,
F.; Ferrais, M.; Grice, J.; Jehin, E.; Jorda, L.; Kaasalainen, M.;
Kryszczynska, A.; Lamy, P.; Marciniak, A.; Michalowski, T.; Michel,
P.; Pajuelo, M.; Podlewska-Gaca, E.; Santana-Ros, T.; Tanga, P.;
Vachier, F.; Vigan, A.; Warner, B.; Witasse, O.; Yang, B.
2018A&A...619L...3V Altcode: 2018arXiv181002771V
Context. Asteroid (16) Psyche is the target of the NASA Psyche
mission. It is considered one of the few main-belt bodies that
could be an exposed proto-planetary metallic core and that would
thus be related to iron meteorites. Such an association is however
challenged by both its near- and mid-infrared spectral properties and
the reported estimates of its density. <BR /> Aims: Here, we aim to
refine the density of (16) Psyche to set further constraints on its
bulk composition and determine its potential meteoritic analog. <BR />
Methods: We observed (16) Psyche with ESO VLT/SPHERE/ZIMPOL as part of
our large program (ID 199.C-0074). We used the high angular resolution
of these observations to refine Psyche's three-dimensional (3D) shape
model and subsequently its density when combined with the most recent
mass estimates. In addition, we searched for potential companions around
the asteroid. <BR /> Results: We derived a bulk density of 3.99 ± 0.26
g cm<SUP>-3</SUP> for Psyche. While such density is incompatible at
the 3-sigma level with any iron meteorites (∼7.8 g cm<SUP>-3</SUP>),
it appears fully consistent with that of stony-iron meteorites such as
mesosiderites (density ∼4.25 g cm<SUP>-3</SUP>). In addition, we found
no satellite in our images and set an upper limit on the diameter of
any non-detected satellite of 1460 ± 200 m at 150 km from Psyche (0.2%
× R<SUB>Hill</SUB>, the Hill radius) and 800 ± 200 m at 2000 km (3% ×
R<SUB>Hill</SUB>). <BR /> Conclusions: Considering that the visible and
near-infrared spectral properties of mesosiderites are similar to those
of Psyche, there is merit to a long-published initial hypothesis that
Psyche could be a plausible candidate parent body for mesosiderites. <P
/>Based on observations made with 1) ESO Telescopes at the La Silla
Paranal Observatory under programs 086.C-0785 (PI Carry) and 199.C-0074
(PI Vernazza); and 2) the W. M. Keck Observatory, which is operated as
a scientific partnership among the California Institute of Technology,
the University of California and the National Aeronautics and Space
Administration. The Observatory was made possible by the generous
financial support of the W. M. Keck Foundation.Tables A1 and A2 and
reduced images are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/619/L3">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/L3</A>
---------------------------------------------------------
Title: Models of Rosetta/OSIRIS 67P Dust Coma Phase Function
Authors: Moreno, F.; Guirado, D.; Muñoz, O.; Bertini, I.; Tubiana,
C.; Güttler, C.; Fulle, M.; Rotundi, A.; Della Corte, V.; Ivanovski,
S. L.; Rinaldi, G.; Bockelée-Morvan, D.; Zakharov, V. V.; Agarwal,
J.; Mottola, S.; Toth, I.; Frattin, E.; Lara, L. M.; Gutiérrez,
P. J.; Lin, Z. Y.; Kolokolova, L.; Sierks, H.; Naletto, G.; Lamy,
P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Barucci, M. A.;
Bertaux, J. -L.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei,
S.; De Cecco, M.; Deller, J.; Fornasier, S.; Ip, W. -H.; Keller,
H. U.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Shi, X.
2018AJ....156..237M Altcode: 2018arXiv180910424M
The phase function of the dust coma of comet 67P has been determined
from Rosetta/OSIRIS images. This function shows a deep minimum at phase
angles near 100°, and a strong backscattering enhancement. These
two properties cannot be reproduced by regular models of cometary
dust, most of them based on wavelength-sized and randomly oriented
aggregate particles. We show, however, that an ensemble of oriented
elongated particles of a wide variety of aspect ratios, with radii
r ≳ 10 μm, and whose long axes are perpendicular to the direction
of the solar radiation, are capable of reproducing the observed phase
function. These particles must be absorbing, with an imaginary part
of the refractive index of about 0.1 to match the expected geometric
albedo, and with porosity in the 60%-70% range.
---------------------------------------------------------
Title: VizieR Online Data Catalog: (16) Psyche images (Viikinkoski+,
2018)
Authors: Viikinkoski, M.; Vernazza, P.; Hanus, J.; Le Coroller,
H.; Tazhenova, K.; Carry, B.; Marsset, M.; Drouard, A.; Marchis, F.;
Fetick, R.; Fusco, T.; Durech, J.; Birlan, M.; Berthier, J.; Bartczak,
P.; Dumas, C.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Ferrais,
M.; Grice, J.; Jehin, E.; Jorda, L.; Kaasalainen, M.; Kryszczynska,
A.; Lamy, P.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo,
M.; Podlewska-Gaca, E.; Santana-Ros, T.; Tanga, P.; Vachier, F.;
Vigan, A.; Warner, B.; Witasse, O.; Yang, B.
2018yCat..36199003V Altcode:
We observed Psyche with VLT/SPHERE/ZIMPOL at five different epochs,
close to its opposition. The data reduction was performed as described
in Vernazza et al. (2018, A&A, in press.). <P />(4 data files).
---------------------------------------------------------
Title: Periodic behaviour of coronal mass ejections, eruptive events,
and solar activity proxies during solar cycles 23 and 24
Authors: Barlyaeva, Tatiana; Wojak, Julien; Lamy, Philippe; Boclet,
Brice; Toth, Imre
2018JASTP.177...12B Altcode: 2017arXiv170402336B
We report on the parallel analysis of the periodic behaviour of coronal
mass ejections (CMEs) based on 21 years [1996-2016] of observations
with the SOHO/LASCO-C2 coronagraph, solar flares, prominences, and
several proxies of solar activity. We consider values of the rates
globally and whenever possible, distinguish solar hemispheres and solar
cycles 23 and 24. Periodicities are investigated using both frequency
(periodogram) and time-frequency (wavelet) analysis. We find that these
different processes, in addition to following the ≈11-year Solar
Cycle, exhibit diverse statistically significant oscillations with
properties common to all solar, coronal, and heliospheric processes:
variable periodicity, intermittence, asymmetric development in the
northern and southern solar hemispheres, and largest amplitudes during
the maximum phase of solar cycles, being more pronounced during solar
cycle 23 than the weaker cycle 24. However, our analysis reveals an
extremely complex and diverse situation. For instance, there exists
very limited commonality for periods of less than one year. The few
exceptions are the periods of 3.1-3.2 months found in the global
occurrence rates of CMEs and in the sunspot area (SSA) and those of
5.9-6.1 months found in the northern hemisphere. Mid-range periods of
≈1 and ≈2 years are more wide spread among the studied processes,
but exhibit a very distinct behaviour with the first one being present
only in the northern hemisphere and the second one only in the southern
hemisphere. These periodic behaviours likely results from the complexity
of the underlying physical processes, prominently the emergence of
magnetic flux.
---------------------------------------------------------
Title: The impact crater at the origin of the Julia family detected
with VLT/SPHERE?
Authors: Vernazza, P.; Brož, M.; Drouard, A.; Hanuš, J.;
Viikinkoski, M.; Marsset, M.; Jorda, L.; Fetick, R.; Carry, B.;
Marchis, F.; Birlan, M.; Fusco, T.; Santana-Ros, T.; Podlewska-Gaca,
E.; Jehin, E.; Ferrais, M.; Bartczak, P.; Dudziński, G.; Berthier,
J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Ďurech,
J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.;
Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.;
Vachier, F.; Vigan, A.; Warner, B.; Witasse, O.; Yang, B.; Asphaug,
E.; Richardson, D. C.; Ševeček, P.; Gillon, M.; Benkhaldoun, Z.
2018A&A...618A.154V Altcode:
Context. The vast majority of the geophysical and geological constraints
(e.g., internal structure, cratering history) for main-belt asteroids
have so far been obtained via dedicated interplanetary missions (e.g.,
ESA Rosetta, NASA Dawn). The high angular resolution of SPHERE/ZIMPOL,
the new-generation visible adaptive-optics camera at ESO VLT, implies
that these science objectives can now be investigated from the ground
for a large fraction of D ≥ 100 km main-belt asteroids. The sharp
images acquired by this instrument can be used to accurately constrain
the shape and thus volume of these bodies (hence density when combined
with mass estimates) and to characterize the distribution and topography
of D ≥ 30 km craters across their surfaces. <BR /> Aims: Here, via
several complementary approaches, we evaluated the recently proposed
hypothesis that the S-type asteroid (89) Julia is the parent body of a
small compact asteroid family that formed via a cratering collisional
event. <BR /> Methods: We observed (89) Julia with VLT/SPHERE/ZIMPOL
throughout its rotation, derived its 3D shape, and performed a
reconnaissance and characterization of the largest craters. We also
performed numerical simulations to first confirm the existence of
the Julia family and to determine its age and the size of the impact
crater at its origin. Finally, we utilized the images/3D shape in
an attempt to identify the origin location of the small collisional
family. <BR /> Results: On the one hand, our VLT/SPHERE observations
reveal the presence of a large crater (D ~ 75 km) in Julia's southern
hemisphere. On the other hand, our numerical simulations suggest that
(89) Julia was impacted 30-120 Myrs ago by a D ~ 8 km asteroid, thereby
creating a D ≥ 60 km impact crater at the surface of Julia. Given the
small size of the impactor, the obliquity of Julia and the particular
orientation of the family in the (a,i) space, the imaged impact
crater is likely to be the origin of the family. <BR /> Conclusions:
New doors into ground-based asteroid exploration, namely, geophysics
and geology, are being opened thanks to the unique capabilities of
VLT/SPHERE. Also, the present work may represent the beginning of a new
era of asteroid-family studies. In the fields of geophysics, geology,
and asteroid family studies, the future will only get brighter with
the forthcoming arrival of 30-40 m class telescopes like ELT, TMT, and
GMT. <P />Based on observations made with ESO Telescopes at the Paranal
Observatory under program ID 199.C-0074 (PI: P. Vernazza). <P />The
reduced images are only available available at the CDS via anonymous ftp
to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(<A href="http://cdsarc.u-strasbg.fr">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/A154">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/A154</A>
---------------------------------------------------------
Title: On deviations from free-radial outflow in the inner coma of
comet 67P/Churyumov-Gerasimenko
Authors: Gerig, S. -B.; Marschall, R.; Thomas, N.; Bertini, I.;
Bodewits, D.; Davidsson, B.; Fulle, M.; Ip, W. -H.; Keller, H. U.;
Küppers, M.; Preusker, F.; Scholten, F.; Su, C. C.; Toth, I.; Tubiana,
C.; Wu, J. -S.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Rickman, H.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.;
Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.;
Fornasier, S.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hviid,
S. F.; Jorda, L.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Lara,
L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Mottola, S.;
Naletto, G.; Oklay, N.; Vincent, J. -B.
2018Icar..311....1G Altcode:
The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS)
onboard the European Space Agency's Rosetta spacecraft acquired images
of comet 67P/Churyumov-Gerasimenko (67P) and its surrounding dust coma
starting from May 2014 until September 2016. In this paper we present
methods and results from analysis of OSIRIS images regarding the dust
outflow in the innermost coma of 67P. The aim is to determine the global
dust outflow behaviour and place constraints on physical processes
affecting particles in the inner coma. We study the coma region right
above the nucleus surface, spanning from the nucleus centre out to
a distance of about 50 km comet centric distance (approximately 25
average comet radii). We primarily adopt an approach used by Thomas
and Keller (1990) to study the dust outflow. We present the effects
on azimuthally-averaged values of the dust reflectance of non-radial
flow and non-point-source geometry, acceleration of dust particles,
sublimation of icy dust particles after ejection from the surface,
dust particle fragmentation, optical depth effects and the influence
of gravitationally bound particles. All of these physical processes
could modify the observed distribution of light scattered by the dust
coma. <P />In the image analysis, profiles of azimuthally averaged dust
brightness as a function of impact parameter b (azimuthal average,
"Ā-curve") were fitted with a simple function that best fits the
shape of our profile curves (f(b ; u , v , w , z) = u /b<SUP>v</SUP>
+ wb + z). The analytical fit parameters (u, v, w, z), which hold
the key information about the dust outflow behaviour, were saved in
a comprehensive database. <P />Through statistical analysis of these
information, we show that the spatial distribution of dust follows
free-radial outflow behaviour (i.e. force-free radial outflow with
constant velocity) beyond distances larger than ∼11.9 km from the
comet centre, which corresponds to a relative distance of about 6
average comet radii from the comet centre. Hence, we conclude that
beyond this distance, and on average, fragmentation and gravitationally
bound particles are negligible processes in determining the optically
scattered light distribution in the innermost coma. Closer to the
nucleus we observe dust outflow behaviour that deviates from free-radial
outflow. <P />A comparison of our result profiles with numerical models
using a Direct Simulation Monte Carlo (DSMC) approach with dust particle
distributions calculated using a test particle approach has been used to
demonstrate the influence of a complex shape and particle acceleration
on the azimuthal average profiles. We demonstrate that, while other
effects such as fragmentation or sublimation of dust particles cannot
be ruled out, acceleration of the dust particles and effects arising
from the shape of the irregular nucleus (non-point source geometry) are
sufficient to explain the observed dust outflow behaviour from image
data analysis. <P />As a by-product of this work, we have calculated
"Afρ" values for the 1/r regime. We found a peak in the coma activity
in terms of Afρ (normalised to a phase angle of 90°) of ∼210 cm
20 days after perihelion. Furthermore, based on simplified models of
particle motion within bound orbits, it is shown that limits on the
total cross-sectional area of bound particles might be derived through
further analysis. An example is given.
---------------------------------------------------------
Title: The big lobe of 67P/Churyumov-Gerasimenko comet: morphological
and spectrophotometric evidences of layering as from OSIRIS data
Authors: Ferrari, Sabrina; Penasa, L.; La Forgia, F.; Massironi, M.;
Naletto, G.; Lazzarin, M.; Fornasier, S.; Hasselmann, P. H.; Lucchetti,
A.; Pajola, M.; Ferri, F.; Cambianica, P.; Oklay, N.; Tubiana, C.;
Sierks, H.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.;
Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese,
G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Franceschi, M.;
Frattin, E.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.;
Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.;
Kührt, E.; Küppers, M.; Lara, L. M.; López-Moreno, J. J.; Marzari,
F.; Shi, X.; Simioni, E.; Thomas, N.; Vincent, J. -B.
2018MNRAS.479.1555F Altcode: 2018MNRAS.tmp.1575F
Between 2014 and 2016, ESA's Rosetta OSIRIS cameras acquired
multiple-filters images of the layered nucleus of comet
67P/Churyumov-Gerasimenko, ranging from ultraviolet to near-infrared
wavelengths. No correlation between layers disposition and surface
spectral variegation has been observed so far. This paper investigates
possible spectral differences among decametre-thickness outcropping
layers of the biggest lobe of the comet by means of OSIRIS image
dataset. A two-classes maximum likelihood classification was
applied on consolidated outcrops and relative deposits identified on
post-perihelion multispectral images of the big lobe. We distinguished
multispectral data on the basis of the structural elevation of the
onion-shell Ellipsoidal Model of 67P. The spatial distribution of the
two classes displays a clear dependence on the structural elevation,
with the innermost class resulting over 50 per cent brighter than the
outermost one. Consolidated cometary materials located at different
structural levels are characterized by different brightness and revealed
due to the selective removal of large volumes. This variegation can
be attributed to a different texture of the outcrop surface and/or to
a different content of refractory materials.
---------------------------------------------------------
Title: Evidence of cool prominence material embedded in CMEs from
polarization measurements
Authors: Lamy, Philippe; Floyd, Olivier; Koutchmy, Serge
2018cosp...42E1930L Altcode:
In white-light coronagraph images, cool prominence material is
sometimes observed as bright substructures or plasmoids in coronal mass
ejections (CMEs). Based on observations of a CME with the SECCHI/STEREO
coronagraphs on 31 August 2007, Mierla et al. (2011) have shown that
the emission from such bright patches is characterized by very low
polarization and was due to H-alpha radiation from cool prominence
material. We have examined several polarization images of CMEs obtained
with the LASCO-C2 coronagraph with its orange filter. This filter is
approximately centered on the HeI D3 line. This low excitation line
emission is superior to the H-alpha emission of HI because its FIP
is much higher. In several cases, we observe very low-polarization
components embedded in CMEs characterized by a much larger polarization
resulting from the Thomson scattering. They most likely present evidence
of cool prominence material carried by the CMEs.
---------------------------------------------------------
Title: VizieR Online Data Catalog: SPHERE/ZIMPOL (89) Julia images
(Vernazza+, 2018)
Authors: Vernazza, P.; Brozv, M.; Drouard, A.; Hanusv, J.;
Viikinkoski, M.; Marsset, M.; Jorda, L.; Fetick, R.; Carry, B.;
Marchis, F.; Birlan, M.; Fusco, T.; Santana-Ros, T.; Podlewska-Gaca,
E.; Jehin, E.; Ferrais, M.; Bartczak, P.; Dudzinski, G.; Berthier,
J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Durech,
J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.;
Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.;
Vachier, F.; Vigan, A.; Warner, B.; Witasse, O.; Yang, B.; Asphaug,
E.; Richardson, D. C.; Svevevek, P.; Gillon, M.; Benkhaldoun, Z.
2018yCat..36180154V Altcode:
Julia was observed with the SPHERE instrument (ESO/VLT) around its
opposition at eight different epochs. We used ZIMPOL in narrowband
imaging mode (N_R filter; filter central wavelength = 645.9nm, width
= 56.7nm). Each observational sequence consisted of a series of
five images, where each image corresponded to a series of detector
integration times (DITs) of 10s, during which Julia was used as a
natural guide star for adaptive optics (AO) corrections. Observations
were performed under good seeing conditions (<=0.8") with an
airmass usually below 1.6. After every asteroid observation, we
observed a nearby star for deconvolution purposes to estimate the
instrument point spread function (PSF). Finally, standard calibrations,
which include detector flat-fields and darks, were acquired in the
morning as part of the instrument calibration plan. <P />objects:
-------------------------------------------------------------------
Planet Name H Diam i e a mag km deg AU
-------------------------------------------------------------------
89 Julia 6.60 151.5 16.127006 0.18459430 2.55051892
-------------------------------------------------------------------
<P />(2 data files).
---------------------------------------------------------
Title: Three-Dimensional Views of the Nucleus of Comet
67P/Churyumov-Gerasimenko - Application to the Characterization of
Active Pits
Authors: Lamy, Philippe; Groussin, Olivier; Faury, Guillaume; Romeuf,
David; Nebouy, David
2018cosp...42E1928L Altcode:
The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard
ESA's Rosetta spacecraft has acquired approximately 25000 images of the
surface of the nucleus of comet 67P/Churyumov-Gerasimenko at various
spatial scales down to centimeters per pixel. The bulk of these images
have been obtained in sequences and the combined displacement of the
Rosetta orbiter along its trajectory and the rotation of the nucleus
allow associating many pairs of images appropriate to stereoscopic
viewing. This is achieved by constructing anaglyphs after rotating
the images so that the relative shift appears horizontal. The shift
is set to limit the parallax to approximately 2° (with a maximum
value of 4°) for the foreground so as to avoid image deformation. A
time of writing, approximately 1000 anaglyphs have been produced. In
addition to offering spectacular stereoscopic views of the nucleus,
these anaglyphs allow studying the topography of the nucleus at spatial
scales unachievable by DTMs. Further coupling with spectral images,
we have been able to locate ice patches at the bottom of several narrow
pits which indicate the presence of sub-surface ice at depths of a few
meters. These narrow pits are most likely the sources of collimated
jets widely seen in the coma of 67PC-G.
---------------------------------------------------------
Title: Three-Dimensional Shape Reconstruction and Propagation of
the CME of 22 October 2003 from LASCO Images
Authors: Lamy, Philippe
2018cosp...42E1929L Altcode:
The determination of the three-dimensional morphology and propagation
of coronal mass ejections (CMEs) in coronagraphic white-light images
has been a major question of coronal physics, and a challenge to the
observers. The STEREO mission has so far provided the required two view
points for stereoscopic reconstruction but that capability has ended
with the loss of one of the S/C. Two-dimensional images as provided by
the LASCO-C2 and C3 coronagraphs are generally insufficientto provide
anything more than an idea of the global and internal structures
of a CME. There are however favorable cases where the relatively
simple morphology of a CME and the geometry of the observations allow
perceiving its global shape. In those cases, forward modeling based on
an a-priori shape model can be attempted, and the resulting synthetic
images are compared and fitted to the observations. We present the
case of the CME detected and tracked by LASCO on 22 October 2003 which
is amenable to such an approach. The global shape of this CME on the
images however requires the introduction of an elaborated shape model,
an asymmetric plasma cloud. The images are first processed in order
to remove most of the background or foreground coronal structures
(essentially streamers) which are superimposed on the CME. Using
the cloud model, we generate synthetic images that are fitted to
the observed images. The resulting parameters allow a detailed
characterization of the 3D shape and propagation of the CME.
---------------------------------------------------------
Title: Tensile strength of 67P/Churyumov-Gerasimenko nucleus material
from overhangs (Corrigendum)
Authors: Attree, N.; Groussin, O.; Jorda, L.; Nébouy, D.; Thomas,
N.; Brouet, Y.; Kührt, E.; Preusker, F.; Scholten, F.; Knollenberg,
J.; Hartogh, P.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.;
Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Auger,
A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.;
Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.;
De Cecco, M.; Deller, J.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.;
Gutiérrez, P. J.; Güttler, C.; Hviid, S.; Ip, W. -H.; Kovacs, G.;
Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno,
J. J.; Lowry, S.; Marchi, S.; Marzari, F.; Mottola, S.; Naletto, G.;
Oklay, N.; Pajola, M.; Toth, I.; Tubiana, C.; Vincent, J. -B.; Shi, X.
2018A&A...614C...2A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Coma morphology of comet 67P controlled by insolation over
irregular nucleus
Authors: Shi, X.; Hu, X.; Mottola, S.; Sierks, H.; Keller, H. U.; Rose,
M.; Güttler, C.; Fulle, M.; Fornasier, S.; Agarwal, J.; Pajola, M.;
Tubiana, C.; Bodewits, D.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Boudreault,
S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco,
M.; Deller, J.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Ip,
W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt,
E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.;
Marzari, F.; Naletto, G.; Oklay, N.; Toth, I.; Vincent, J. -B.
2018NatAs...2..562S Altcode: 2018NatAs.tmp...59S
While the structural complexity of cometary comae is already
recognizable from telescopic observations<SUP>1</SUP>, the innermost
region, within a few radii of the nucleus, was not resolved until
spacecraft exploration became a reality<SUP>2,3</SUP>. The dust coma
displays jet-like features of enhanced brightness superposed on a
diffuse background<SUP>1,4,5</SUP>. Some features can be traced to
specific areas on the nucleus, and result conceivably from locally
enhanced outgassing and/or dust emission<SUP>6-8</SUP>. However,
diffuse or even uniform activity over topographic concavity can
converge to produce jet-like features<SUP>9,10</SUP>. Therefore,
linking observed coma morphology to the distribution of activity on
the nucleus is difficult<SUP>11,12</SUP>. Here, we study the emergence
of dust activity at sunrise on comet 67P/Churyumov-Gerasimenko using
high-resolution, stereo images from the OSIRIS camera onboard the
Rosetta spacecraft, where the sources and formation of the jet-like
features are resolved. We perform numerical simulations to show that
the ambient dust coma is driven by pervasive but non-uniform water
outgassing from the homogeneous surface layer. Physical collimations
of gas and dust flows occur at local maxima of insolation and also
via topographic focusing. Coma structures are projected to exhibit
jet-like features that vary with the perspective of the observer. For
an irregular comet such as 67P/Churyumov-Gerasimenko, near-nucleus
coma structures can be concealed in the shadow of the nucleus, which
further complicates the picture.
---------------------------------------------------------
Title: The phase function and density of the dust observed at comet
67P/Churyumov-Gerasimenko
Authors: Fulle, Marco; Bertini, I.; Della Corte, V.; Güttler, C.;
Ivanovski, S.; La Forgia, F.; Lasue, J.; Levasseur-Regourd, A. C.;
Marzari, F.; Moreno, F.; Mottola, S.; Naletto, G.; Palumbo, P.;
Rinaldi, G.; Rotundi, A.; Sierks, H.; Barbieri, C.; Lamy, P. L.;
Rodrigo, R.; Koschny, D.; Rickman, H.; Barucci, M. A.; Bertaux,
J. -L.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.;
Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Groussin, O.;
Gutiérrez, P. J.; Hviid, H. S.; Ip, W. H.; Jorda, L.; Keller, H. U.;
Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, M. L.;
Lazzarin, M.; López-Moreno, J. J.; Shi, X.; Thomas, N.; Tubiana, C.
2018MNRAS.476.2835F Altcode: 2018MNRAS.tmp..454F
The OSIRIS camera onboard Rosetta measured the phase function of both
the coma dust and the nucleus. The two functions have a very different
slope versus the phase angle. Here, we show that the nucleus phase
function should be adopted to convert the brightness to the size of dust
particles larger than 2.5 mm only. This makes the dust bursts observed
close to Rosetta by OSIRIS, occurring about every hour, consistent
with the fragmentation on impact with Rosetta of parent particles,
whose flux agrees with the dust flux observed by GIADA. OSIRIS also
measured the antisunward acceleration of the fragments, thus providing
the first direct measurement of the solar radiation force acting
on the dust fragments and thus of their bulk density, excluding any
measurable rocket effect by the ice sublimation from the dust. The
obtained particle density distribution has a peak matching the bulk
density of most COSIMA particles, and represents a subset of the density
distribution measured by GIADA. This implies a bias in the elemental
abundances measured by COSIMA, which thus are consistent with the 67P
dust mass fractions inferred by GIADA, i.e. (38 ± 8) {per cent} of
hydrocarbons versus the (62 ± 8) {per cent} of sulphides and silicates.
---------------------------------------------------------
Title: Exposed bright features on the comet 67P/Churyumov-Gerasimenko:
distribution and evolution
Authors: Deshapriya, J. D. P.; Barucci, M. A.; Fornasier, S.;
Hasselmann, P. H.; Feller, C.; Sierks, H.; Lucchetti, A.; Pajola,
M.; Oklay, N.; Mottola, S.; Masoumzadeh, N.; Tubiana, C.; Güttler,
C.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.;
Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese,
G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; De Cecco, M.; Deller,
J.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hoang, H. V.; Hviid,
S. F.; Ip, W.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm,
R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno,
J. J.; Marzari, F.; Naletto, G.; Preusker, F.; Shi, X.; Thomas, N.;
Vincent, J. -B.
2018A&A...613A..36D Altcode:
Context. Since its arrival at the comet 67P/Churyumov-Gerasimenko
in August 2014, the Rosetta spacecraft followed the comet as it went
past the perihelion and beyond until September 2016. During this time
there were many scientific instruments operating on board Rosetta
to study the comet and its evolution in unprecedented detail. In
this context, our study focusses on the distribution and evolution
of exposed bright features that have been observed by OSIRIS, which
is the scientific imaging instrument aboard Rosetta. <BR /> Aims:
We envisage investigating various morphologies of exposed bright
features and the mechanisms that triggered their appearance. <BR />
Methods: We co-registered multi-filter observations of OSIRIS images
that are available in reflectance. The Lommel-Seeliger disk function
was used to correct for the illumination conditions and the resulting
colour cubes were used to perform spectrophotometric analyses on
regions of interest. <BR /> Results: We present a catalogue of 57
exposed bright features observed on the nucleus of the comet, all
of which are attributed to the presence of H<SUB>2</SUB>O ice on the
comet. Furthermore, we categorise these patches under four different
morphologies and present geometric albedos for each category. <BR />
Conclusions: Although the nucleus of 67P/Churyumov-Gerasimenko appears
to be dark in general, there are localised H<SUB>2</SUB>O ice sources
on the comet. Cometary activity escalates towards the perihelion passage
and reveals such volatile ices. We propose that isolated H<SUB>2</SUB>O
ice patches found in smooth terrains in regions, such as Imhotep, Bes,
and Hapi, result from frost as an aftermath of the cessation of the
diurnal water cycle on the comet as it recedes from perihelion. Upon
the comet's return to perihelion, such patches are revealed when
sublimation-driven erosion removes the thin dust layers that got
deposited earlier. More powerful activity sources such as cometary
outbursts are capable of revealing much fresher, less contaminated
H<SUB>2</SUB>O ice that is preserved with consolidated cometary
material, as observed on exposed patches resting on boulders. This is
corroborated by our albedo calculations that attribute higher albedos
for bright features with formations related to outbursts.
---------------------------------------------------------
Title: Tensile strength of 67P/Churyumov-Gerasimenko nucleus material
from overhangs
Authors: Attree, N.; Groussin, O.; Jorda, L.; Nébouy, D.; Thomas,
N.; Brouet, Y.; Kührt, E.; Preusker, F.; Scholten, F.; Knollenberg,
J.; Hartogh, P.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.;
Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Auger,
A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.;
Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.;
De Cecco, M.; Deller, J.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.;
Gutiérrez, P. J.; Güttler, C.; Hviid, S.; Ip, W. -H.; Kovacs, G.;
Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno,
J. J.; Lowry, S.; Marchi, S.; Marzari, F.; Mottola, S.; Naletto, G.;
Oklay, N.; Pajola, M.; Toth, I.; Tubiana, C.; Vincent, J. -B.; Shi, X.
2018A&A...611A..33A Altcode: 2017arXiv171207508A
We directly measured twenty overhanging cliffs on the surface of comet
67P/Churyumov-Gerasimenko extracted from the latest shape model and
estimated the minimum tensile strengths needed to support them against
collapse under the comet's gravity. We find extremely low strengths
of around 1 Pa or less (1 to 5 Pa, when scaled to a metre length). The
presence of eroded material at the base of most overhangs, as well as
the observed collapse of two features andthe implied previous collapse
of another, suggests that they are prone to failure and that the true
material strengths are close to these lower limits (although we only
consider static stresses and not dynamic stress from, for example,
cometary activity). Thus, a tensile strength of a few pascals is a good
approximation for the tensile strength of the 67P nucleus material,
which is in agreement with previous work. We find no particular trends
in overhang properties either with size over the 10-100 m range studied
here or location on the nucleus. There are no obvious differences,
in terms of strength, height or evidence of collapse, between the
populations of overhangs on the two cometary lobes, suggesting that
67P is relatively homogenous in terms of tensile strength. Low material
strengths are supportive of cometary formation as a primordial rubble
pile or by collisional fragmentation of a small body (tens of km).
---------------------------------------------------------
Title: Meter-scale thermal contraction crack polygons on the nucleus
of comet 67P/Churyumov-Gerasimenko
Authors: Auger, A. -T.; Groussin, O.; Jorda, L.; El-Maarry, M. R.;
Bouley, S.; Séjourné, A.; Gaskell, R.; Capanna, C.; Davidsson,
B.; Marchi, S.; Höfner, S.; Lamy, P. L.; Sierks, H.; Barbieri,
C.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal,
J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.;
Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.;
Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Hviid, S.; Ip, W. -H.;
Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara,
L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Massironi,
M.; Michalik, H.; Naletto, G.; Oklay, N.; Pommerol, A.; Sabau, L.;
Thomas, N.; Tubiana, C.; Vincent, J. -B.; Wenzel, K. -P.
2018Icar..301..173A Altcode:
We report on the detection and characterization of more
than 6300 polygons on the surface of the nucleus of comet
67P/Churyumov-Gerasimenko, using images acquired by the OSIRIS camera
onboard Rosetta between August 2014 and March 2015. They are found
in consolidated terrains and grouped in localized networks. They are
present at all latitudes (from North to South) and longitudes (head,
neck, and body), sometimes on pit walls or following lineaments. About
1.5% of the observed surface is covered by polygons. Polygons have
an homogeneous size across the nucleus, with 90% of them in the size
range 1 - 5 m and a mean size of 3.0 ± 1.4 m. They show different
morphologies, depending on the width and depth of their trough. They are
found in networks with 3- or 4-crack intersection nodes. The polygons
observed on 67P are consistent with thermal contraction crack polygons
formed by the diurnal or seasonal temperature variations in a hard
(MPa) and consolidated sintered layer of water ice, located a few
centimeters below the surface. Our thermal analysis shows an evolution
of thermal contraction crack polygons according to the local thermal
environment, with more evolved polygons (i.e. deeper and larger troughs)
where the temperature and the diurnal and seasonal temperature range
are the highest. Thermal contraction crack polygons are young surface
morphologies that probably formed after the injection of 67P in the
inner solar system, typically 100,000 years ago, and could be as young
as a few orbital periods, following the decreasing of its perihelion
distance in 1959 from 2.7 to 1.3 a.u. Meter scale thermal contraction
crack polygons should be common features on the nucleus of Jupiter
family comets.
---------------------------------------------------------
Title: Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko
Authors: Höfner, S.; Vincent, J. -B.; Blum, J.; Davidsson, B. J. R.;
Sierks, H.; El-Maarry, M. R.; Deller, J.; Hofmann, M.; Hu, X.; Pajola,
M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman,
H.; Keller, H. U.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.;
Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo,
V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Gicquel, A.;
Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marqués, P.; Güttler,
C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.;
Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin,
M.; Lopez-Moreno, J. J.; Marzari, F.; Michalik, H.; Moissl-Fraund,
R.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Preusker, F.;
Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.; Zitzmann, S.
2017A&A...608A.121H Altcode:
Context. The camera OSIRIS on board Rosetta obtained high-resolution
images of the nucleus of comet 67P/Churyumov-Gerasimenko (67P). Great
parts of the nucleus surface are composed of fractured terrain. <BR
/> Aims: Fracture formation, evolution, and their potential
relationship to physical processes that drive activity are not yet
fully understood. Observed temperatures and gas production rates can
be explained or interpreted with the presence of fractures by applying
appropriate modelling methods. <BR /> Methods: We followed a transient
thermophysical model approach that includes radiative, conductive, and
water-ice sublimation fluxes by considering a variety of heliocentric
distances, illumination conditions, and thermophysical properties
for a set of characteristic fracture geometries on the nucleus of
67P. We computed diurnal temperatures, heat fluxes, and outgassing
behaviour in order to derive and distinguish the influence of the
mentioned parameters on fractured terrain. <BR /> Results: Our analysis
confirms that fractures, as already indicated by former studies about
concavities, deviate from flat-terrain topographies with equivalent
properties, mostly through the effect of self-heating. Compared to
flat terrain, illuminated cometary fractures are generally warmer,
with smaller diurnal temperature fluctuations. Maximum sublimation
rates reach higher peaks, and dust mantle quenching effects on
sublimation rates are weaker. Consequently, the rough structure
of the fractured terrain leads to significantly higher inferred
surface thermal inertia values than for flat areas with identical
physical properties, which might explain the range of measured thermal
inertia on 67P. <BR /> Conclusions: At 3.5 AU heliocentric distance,
sublimation heat sinks in fractures converge to maximum values >50
W / m<SUP>2</SUP> and trigger dust activity that can be related mainly
to H<SUB>2</SUB>O. Fractures are likely to grow through the erosive
interplay of alternating sublimation and thermal fatigue.
---------------------------------------------------------
Title: Anomalous Surge of the White-Light Corona at the Onset of
the Declining Phase of Solar Cycle 24
Authors: Lamy, P.
2017AGUFMSH13A2465L Altcode:
In late 2014, when the current solar cycle 24 was initiating its
declining phase, the white-light corona as observed by the LASCO-C2
coronagraph underwent an unexpected surge that increased its global
radiance by 60%, reaching a peak value comparable to those of the
more active solar cycle 23. The daily variations point to a localized
enhancement or bulge in the electron density that persisted during
several months. Carrington maps of the radiance and of the HMI
photospheric field allow connecting this bulge to the emergence
of the large sunspot complex AR 12192 in October 2014, the largest
since AR 6368 observed in November 1990. The resulting unusually large
increase of the magnetic field and the distortion of the neutral sheet
in a characteristic inverse S-shape caused the coronal plasma to be
trapped along a similar pattern. Three-dimensional reconstruction
of the electron density based on time-dependent solar rotational
tomography supplemented by 2D inversion of the coronal radiance
confirms the morphology of the bulge and reveals that its level
was well above the standard models of a corona of the maximum type,
by typically a factor of 3. A rather satisfactory agreement is found
with the results of the thermodynamic MHD model produced by Predictive
Sciences although discrepancies are noted. The specific configuration
of the magnetic field that led to the coronal surge resulted from the
interplay of various factors prevailing at the onset of the declining
phase of the solar cycles which was particularly efficient in the case
of solar cycle 24.
---------------------------------------------------------
Title: ASPIICS: a giant, white light and emission line coronagraph
for the ESA proba-3 formation flight mission
Authors: Lamy, P. L.; Vivès, S.; Curdt, W.; Damé, L.; Davila, J.;
Defise, J. -M.; Fineschi, S.; Heinzel, P.; Howard, Russel; Kuzin,
S.; Schmutz, W.; Tsinganos, K.; Zhukov, A.
2017SPIE10565E..0TL Altcode:
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observations of the white light corona inside typically 2-2.5
solar radii (Rsun). Formation flying offers and elegant solution to
these limitations and allows conceiving giant, externally-occulted
coronagraphs using a two-component space system with the external
occulter on one spacecraft and the optical instrument on the
other spacecraft at a distance of hundred meters [1, 2]. Such
an instrument ASPIICS (Association de Satellites Pour l'Imagerie
et l'Interférométrie de la Couronne Solaire) has been selected
by the European Space Agency (ESA) to fly on its PROBA-3 mission
of formation flying demonstration which is presently in phase B
(Fig. 1). The classical design of an externally-occulted coronagraph is
adapted to the formation flying configuration allowing the detection
of the very inner corona as close as 0.04 solar radii from the solar
limb. By tuning the position of the occulter spacecraft, it may even be
possible to reach the chromosphere and the upper part of the spicules
[3]. ASPIICS will perform (i) high spatial resolution imaging of the
continuum K+F corona in photometric and polarimetric modes, (ii) high
spatial resolution imaging of the E-corona in two coronal emission lines
(CEL): Fe XIV and He I D3, and (iii) two-dimensional spectrophotometry
of the Fe XIV emission line. ASPIICS will address the question of the
coronal heating and the role of waves by characterizing propagating
fluctuations (waves and turbulence) in the solar wind acceleration
region and by looking for oscillations in the intensity and Doppler
shift of spectral lines. The combined imaging and spectral diagnostics
capabilities available with ASPIICS will allow mapping the velocity
field of the corona both in the sky plane (directly on the images)
and along the line-of-sight by measuring the Doppler shifts of
emission lines in an effort to determine how the different components
of the solar wind, slow and fast are accelerated. With a possible
launch in 2014, ASPIICS will observe the corona during the maximum of
solar activity, insuring the detection of many Coronal Mass Ejections
(CMEs). By rapidly alternating high-resolution imaging and spectroscopy,
CMEs will be thoroughly characterized.
---------------------------------------------------------
Title: ASPIICS/PROBA-3 formation flying solar coronagraph: Stray
light analysis and optimization of the occulter
Authors: Landini, F.; Mazzoli, A.; Venet, M.; Vivès, S.; Romoli,
M.; Lamy, P.; Massone, G.
2017SPIE10565E..1RL Altcode:
The "Association de Satellites Pour l'Imagerie et l'Interferometrie
de la Couronne Solaire", ASPIICS, selected by ESA for the PROBA-3
mission, heralds the next generation of coronagraph for solar research,
exploiting formation flying to gain access to the inner corona under
eclipse-like conditions for long periods of time. A detailed description
of the ASPIICS instrument and of its scientific objectives can be
found in [1]. ASPIICS is distributed on the two PROBA 3 spacecrafts
(S/C) separated by 150 m. The coronagraph optical assembly is hosted
by the "coronagraph S/C" protected from direct solar disk light by
the occulting disk on the "occulter S/C". The most critical issue
in the design of a solar coronagraph is the reduction of the stray
light due to the diffraction and scattering of the solar disk light
by the occulter, the aperture and the optics. In the present article,
we deal with two of these issues: - The analysis of the stray light
inside the telescope. - The optimization of the external occulter
edge, in order to eliminate the Poisson spot behind the occulter and
to lower the stray light level going through the entrance pupil of
the telescope. This work was performed in the framework of the ESA
STARTIGER program which took place at the Laboratoire d'Astrophysique
de Marseille (LAM) during a 6-month period from September 2009 to March
2010. In general, it is a very complicated task to combine the above
two stray light issues together in the simulation and design phase
as it requires to consider the propagation inside the telescope of
the light diffracted by the external occulter. Actually, the present
literature only reports diffraction calculations performed for simple
occulting systems (i.e., two disks and serrated disk). A more pragmatic
approach, also driven by the tight schedule of the STARTIGER program, is
to separate the two contributions, and perform two different stray light
analyses. This paper is dedicated to the description of both analyses:
in particular, the first part is dedicated to the evaluation of the
stray light inside the telescope, assuming a simple disk as occulter,
and a preliminary baffle design is presented; the second part describes
the investigation on the geometry of the external occulter, with a
detailed description of the laboratory setup that has been designed
and implemented to compare together several types of occulting systems.
---------------------------------------------------------
Title: METIS, the Multi Element Telescope for Imaging and
Spectroscopy: an instrument proposed for the solar orbiter mission
Authors: Antonucci, E.; Andretta, V.; Cesare, S.; Ciaravella, A.;
Doschek, G.; Fineschi, S.; Giordano, S.; Lamy, P.; Moses, D.; Naletto,
G.; Newmark, J.; Poletto, L.; Romoli, M.; Solanki, S.; Spadaro, D.;
Teriaca, L.; Zangrilli, L.
2017SPIE10566E..0LA Altcode:
METIS, the Multi Element Telescope for Imaging and Spectroscopy,
is an instrument proposed to the European Space Agency to be part of
the payload of the Solar Orbiter mission. The instrument design has
been conceived for performing extreme ultraviolet (EUV) spectroscopy
both on the solar disk and off-limb, and near-Sun coronagraphy
and spectroscopy. The proposed instrument suite consists of three
different interconnected elements, COR, EUS and SOCS, sharing the
same optical bench, electronics, and S/C heat shield aperture. COR is
a visible-EUV multiband coronagraph based on a classical externally
occulted design. EUS is the component of the METIS EUV disk spectrometer
which includes the telescope and all the related mechanisms. Finally,
SOCS is the METIS spectroscopic component including the dispersive
system and the detectors. The capability of inserting a small telescope
collecting coronal light has been added to perform also EUV coronal
spectroscopy. METIS can simultaneously image the visible and ultraviolet
emission of the solar corona and diagnose, with unprecedented temporal
coverage and space resolution the structure and dynamics of the full
corona in the range from 1.2 to 3.0 (1.6 to 4.1) solar radii (R⊙,
measured from Sun centre) at minimum (maximum) perihelion during the
nominal mission. It can also perform spectroscopic observations of the
solar disk and out to 1.4 R⊙ within the 50-150 nm spectral region,
and of the geo-effective coronal region 1.7-2.7 R⊙ within the 30-125
nm spectral band.
---------------------------------------------------------
Title: Preliminary calibration results of the wide angle camera of
the imaging instrument OSIRIS for the Rosetta mission
Authors: Da Deppo, V.; Naletto, G.; Nicolosi, P.; Zambolin, P.; De
Cecco, M.; Debei, S.; Parzianello, G.; Ramous, P.; Zaccariotto, M.;
Fornasier, S.; Verani, S.; Thomas, N.; Barthol, P.; Hviid, S. F.;
Sebastian, I.; Meller, R.; Sierks, H.; Keller, H. U.; Barbieri, C.;
Angrilli, F.; Lamy, P.; Rodrigo, R.; Rickman, H.; Wenzel, K. P.
2017SPIE10568E..0ND Altcode:
Rosetta is one of the cornerstone missions of the European Space Agency
for having a rendezvous with the comet 67P/Churyumov-Gerasimenko in
2014. The imaging instrument on board the satellite is OSIRIS (Optical,
Spectroscopic and Infrared Remote Imaging System), a cooperation
among several European institutes, which consists of two cameras:
a Narrow (NAC) and a Wide Angle Camera (WAC). The WAC optical design
is an innovative one: it adopts an all reflecting, unvignetted and
unobstructed two mirror configuration which allows to cover a 12° ×
12° field of view with an F/5.6 aperture and gives a nominal contrast
ratio of about 10<SUP>-4</SUP>. The flight model of this camera has
been successfully integrated and tested in our laboratories, and
finally has been integrated on the satellite which is now waiting to
be launched in February 2004. In this paper we are going to describe
the optical characteristics of the camera, and to summarize the results
so far obtained with the preliminary calibration data. The analysis of
the optical performance of this model shows a good agreement between
theoretical performance and experimental results.
---------------------------------------------------------
Title: Preliminary optical design of the coronagraph for the ASPIICS
formation flying mission
Authors: Vivès, S.; Lamy, P.; Saisse, M.; Boit, J. -L.; Koutchmy, S.
2017SPIE10567E..1WV Altcode:
Formation flyers open new perspectives and allow to conceive
giant, externally-occulted coronagraphs using a two-component space
system with the external occulter on one spacecraft and the optical
instrument on the other spacecraft at approximately 100-150 m from
the first one. ASPIICS (Association de Satellites Pour l'Imagerie
et l'Interfromtrie de la Couronne Solaire) is a mission proposed
to ESA in the framework of the PROBA-3 program of formation flying
which is presently in phase A to exploit this technique for coronal
observations. ASPIICS is composed of a single coronagraph which performs
high spatial resolution imaging of the corona as well as 2-dimensional
spectroscopy of several emission lines from the coronal base out to
3 R. The selected lines allow to address different coronal regions:
the forbidden line of Fe XIV at 530.285 nm (coronal matter), Fe IX/X at
637.4 nm (coronal holes), HeI at 587.6 nm (cold matter). An additional
broad spectral channel will image the white light corona so as to derive
electron densities. The classical design of an externally occulted
coronagraph is adapted to the detection of the very inner corona as
close as 1.01 R and the addition of a Fabry-Perot interferometer using
a so-called "etalon". This paper is dedicated to the description of
the optical design and its critical components: the entrance optics
and the FabryPerot interferometer.
---------------------------------------------------------
Title: Stray light rejection in giant externally-occulted solar
coronagraphs: experimental developments
Authors: Venet, M.; Bazin, C.; Koutchmy, S.; Lamy, P.
2017SPIE10565E..1WV Altcode:
The advent of giant, formation-flight, externally-occulted solar
coronagraphs such as ASPIICS (Association de Satellites Pour l'Imagerie
et l'Interférométrie de la Couronne Solaire [1,2,3,4]) selected
by the European Space Agency (ESA) for its third PROBA (Project for
On-Board Autonomy) mission of formation flying demonstration (presently
in phase B) and Hi-RISE proposed in the framework of ESA Cosmic Vision
program, presents formidable challenges for the study and calibration of
instrumental stray light. With distances between the external occulter
(EO) and the optical pupil (OP) exceeding hundred meters and occulter
sizes larger than a meter, it becomes impossible to perform tests at
the real scale. The requirement to limit the over-occultation to less
than 1.05 Rsun, orders of magnitude to what has been achieved so far in
past coronagraphs, further adds to the challenge. We are approaching
the problem experimentally using reduced scale simulators and present
below a progress report of our work.
---------------------------------------------------------
Title: The global meter-level shape model of comet
67P/Churyumov-Gerasimenko
Authors: Preusker, F.; Scholten, F.; Matz, K. -D.; Roatsch, T.;
Hviid, S. F.; Mottola, S.; Knollenberg, J.; Kührt, E.; Pajola, M.;
Oklay, N.; Vincent, J. -B.; Davidsson, B.; A'Hearn, M. F.; Agarwal,
J.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.;
Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.;
Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Ip, W. -H.;
Jorda, L.; Keller, H. U.; Koschny, D.; Kramm, J. R.; Küppers, M.;
Lamy, P.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari,
F.; Massironi, M.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sierks,
H.; Thomas, N.; Tubiana, C.
2017A&A...607L...1P Altcode:
We performed a stereo-photogrammetric (SPG) analysis of more than
1500 Rosetta/OSIRIS NAC images of comet 67P/Churyumov-Gerasimenko
(67P). The images with pixel scales in the range 0.2-3.0 m/pixel were
acquired between August 2014 and February 2016. We finally derived
a global high-resolution 3D description of 67P's surface, the SPG
SHAP7 shape model. It consists of about 44 million facets (1-1.5 m
horizontal sampling) and a typical vertical accuracy at the decimeter
scale. Although some images were taken after perihelion, the SPG SHAP7
shape model can be considered a pre-periheliondescription and replaces
the previous SPG SHAP4S shape model. From the new shape model, some
measures for 67P with very low 3σ uncertainties can be retrieved:
18.56 km<SUP>3</SUP> ± 0.02 km<SUP>3</SUP> for the volume and 537.8
kg/m<SUP>3</SUP> ± 0.7 kg/m<SUP>3</SUP> for the mean density assuming
a mass value of 9.982 × 10<SUP>12</SUP> kg.
---------------------------------------------------------
Title: Three-dimensional views of the nucleus of Comet
67P/Churyumov-Gerasimenko: an atlas of stereo anaglyphs from
OSIRIS-NAC images
Authors: Lamy, Philippe L.; Romeuf, David; Faury, Guillaume; Durand,
Joelle; Beigbeder, Laurent; Groussin, Olivier
2017DPS....4941504L Altcode:
The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard
ESA’s Rosetta spacecraft has acquired approximately 25000 images of
the surface of the nucleus of comet 67P/Churyumov-Gerasimenko at various
spatial scales down to centimeters per pixel. The bulk of these images
have been obtained in sequences and the combined displacement of the
Rosetta orbiter along its trajectory and the rotation of the nucleus
allow associating many pairs of images appropriate to stereoscopic
viewing. This is achieved by constructing anaglyphs after rotating the
images so that the relative shift appears horizontal. The shift is set
to limit the parallax to approximately 2° (with a maximum value of
4°) for the foreground (to avoid image deformation) and the scene is
placed behind the screen for optimal visual comfort. The rotation of the
nucleus may have the adverse effect of introducing temporal incoherence,
prominently from the variation of the cast shadows. Various solutions
are implemented to circumvent this problem, usually by cropping the
maximum extent of the shadows. A time of writing, approximately 900
anaglyphs have been produced and we expect to reach several thousand
once the systematic search of suitable pairs will be completed. We
will present examples of anaglyphs. They will be searchable thanks
to a dedicated data base that will document each one including its
location on a 3D numerical model of the nucleus. Many possibilities of
querying the parameters will be offered. It is anticipated that this
atlas available online in the near future will be a valuable tool for
fostering our understanding of the complex morphology of the cometary
surface and of the processes at work , as well as offering spectacular
stereoscopic views of the nucleus enjoyable by a general public.
---------------------------------------------------------
Title: Large scale morphological changes in the Hapi region on comet
67P/Churyumov-Gerasimenko
Authors: Davidsson, Bjorn; Lee, Seungwon; von Allmen, Paul; Schloerb,
Peter; Hofstadter, Mark; Sierks, Holger; Barbieri, Cesare; Gulkis,
Samuel; Keller, Horst Uwe; Koschny, Detlef; Lamy, Philippe; Rickman,
Hans; Rodrigo, Rafa; MIRO Team; OSIRIS Team
2017DPS....4941502D Altcode:
The Hapi region is located on the northern hemisphere of comet 67P/C-G
at the neck that joins the two lobes of the nucleus. It primarily
consists of granular material that is unresolved at 0.35 m/pixel
resolution and that forms a smooth surface with small slopes with
respect to local gravity. The OSIRIS cameras on the ESA spacecraft
Rosetta observed Hapi regularly since its rendezvous with the comet
in August 2014. No changes were seen during the first five months
in orbit but on December 30, 2014, two spots appeared in Hapi. Over
the course of two months they grew gradually into a 110 by 70 meter
shallow depression with a depth of about 0.5 meters. We use OSIRIS
observations to characterize the morphology and spectrophotometry of
the region. We use measurements of the thermal emission of the comet by
the MIRO millimeter and submillimeter radiometer in combination with
thermophysical modeling to characterize the surface temperature, near
surface temperature gradient, and thermal inertia of the region. The
formation mechanism of the depression is discussed in view of these
empirical data.
---------------------------------------------------------
Title: Evidences of Shear Deformations on Comet
67P/Churyumov-Gerasimenko: probing the internal structure of the
nucleus
Authors: Matonti, C.; Attree, N.; Groussin, O.; Jorda, L.; Viseur,
S.; Nebouy, D.; Auger, A. T.; Lamy, P.
2017EPSC...11..777M Altcode:
In this work we emphasize the occurrence of structures that can
be explained by shear deformation on the nucleus of comet 67P. We
first show that the majority of the lineaments in the neck regions
correspond to fractures arranged in a network characteristic of shear
deformation. These deformations are preferentially located in or near
the neck regions. They have likely participated in the mechanical
breakdown and the erosion of the nucleus. These results may have
implication for deciphering the nucleus internal structural down to
hundreds of meters and for inferring the nucleus material mechanical
properties.
---------------------------------------------------------
Title: Characterization of the Abydos landing site of Philae on
comet 67P/Churyumov-Gerasimenko
Authors: Lamy, P.; Faury, G.; Jorda, L.; Romeuf, D.; Capanna, C.;
El-Maarry, M. R.; Gaskell, R.; Groussin, O.; Nebouy, D.
2017EPSC...11..560L Altcode:
Characterization of the final Abydos landing site of Philae on the
nucleus of comet 67P/Churyumov-Gerasimenko based on twelve campaigns
of imaging with the OSIRIS-NAC camera. The characterization is based
on anaglyphs, a digital terrain model at a spatial scale of 40 cm
and color maps. We present the regional setting of Abydos and define
geological units. Abydos is essentially an alcove at the foot of a
scarp composed of heavily fractured consolidated materials.
---------------------------------------------------------
Title: Seasonal erosion and restoration of the dust cover on comet
67P/Churyumov-Gerasimenko as observed by OSIRIS onboard Rosetta
Authors: Hu, X.; Shi, X.; Sierks, H.; Fulle, M.; Blum, J.; Keller,
H. U.; Kührt, E.; Davidsson, B.; Güttler, C.; Gundlach, B.; Pajola,
M.; Bodewits, D.; Vincent, J. -B.; Oklay, N.; Massironi, M.; Fornasier,
S.; Tubiana, C.; Groussin, O.; Boudreault, S.; Höfner, S.; Mottola,
S.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.;
A'Hearn, M.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini,
I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller,
J.; El-Maarry, M. R.; Gicquel, A.; Gutierrez-Marques, P.; Gutiérrez,
P. J.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg,
J.; Kovacs, G.; Kramm, J. -R.; Küppers, M.; Lara, L. M.; Lazzarin,
M.; Lopez-Moreno, J. J.; Marzari, F.; Naletto, G.; Thomas, N.
2017A&A...604A.114H Altcode:
Context. Dust deposits or dust cover are a prevalent morphology in the
northern hemi-nucleus of comet 67P/Churyumov-Gerasimenko (67P). The
evolution of the dust deposits was captured by the OSIRIS camera system
onboard the Rosetta spacecraft having escorted the comet for over two
years. The observations shed light on the fundamental role of cometary
activity in shaping and transforming the surface morphology. <BR />
Aims: We aim to present OSIRIS observations of surface changes over
the dust deposits before and after perihelion. The distribution of
changes and a timeline of their occurrence are provided. We perform a
data analysis to quantify the surface changes and investigate their
correlation to water activity from the dust deposits. We further
discuss how the results of our investigation are related to other
findings from the Rosetta mission. <BR /> Methods: Surface changes
were detected via systematic comparison of images, and quantified using
shape-from-shading technique. Thermal models were applied to estimate
the erosion of water ice in response to the increasing insolation over
the areas where surface changes occurred. Modeling results were used
for the interpretation of the observed surface changes. <BR /> Results:
Surface changes discussed here were concentrated at mid-latitudes,
between about 20°N and 40°N, marking a global transition from the
dust-covered to rugged terrains. The changes were distributed in open
areas exposed to ample solar illumination and likely subject to enhanced
surface erosion before perihelion. The occurrence of changes followed
the southward migration of the sub-solar point across the latitudes
of their distribution. The erosion at locations of most changes was at
least about 0.5 m, but most likely did not exceed several meters. The
erosive features before perihelion had given way to a fresh, smooth
cover of dust deposits after perihelion, suggesting that the dust
deposits had been globally restored by at least about 1 m with ejecta
from the intensely illuminated southern hemi-nucleus around perihelion,
when the north was inactive during polar night. <BR /> Conclusions: The
erosion and restoration of the northern dust deposits are morphological
expressions of seasonality on 67P. Based on observations and thermal
modeling results, it is inferred that the dust deposits contained a
few percent of water ice in mass on average. Local inhomogeneity in
water abundance at spatial scales below tens of meters is likely. We
suspect that dust ejected from the deposits may not have escaped the
comet in bulk. That is, at least half of the ejected mass was afloat
in the inner-coma or/and redeposited over other areas of the nucleus.
---------------------------------------------------------
Title: Long-term monitoring of comet 67P/Churyumov-Gerasimenko's
jets with OSIRIS onboard Rosetta
Authors: Schmitt, M. I.; Tubiana, C.; Güttler, C.; Sierks, H.;
Vincent, J. -B.; El-Maarry, M. R.; Bodewits, D.; Mottola, S.;
Fornasier, S.; Hofmann, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Rickman, H.; A'Hearn, M. F.; Agarwal, J.; Barucci, M. A.;
Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson,
B.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Gicquel, A.;
Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.;
Keller, H. U.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers,
M.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.;
Naletto, G.; Oklay, N.; Pajola, M.; Prasanna, D.; Shi, X.; Scholten,
F.; Toth, I.; Thomas, N.
2017MNRAS.469S.380S Altcode:
We used the OSIRIS camera system onboard the Rosetta spacecraft to
monitor jet activity of comet 67P/Churyumov-Gerasimenko. With a monthly
cadence, we covered an epoch from 2014 December to 2015 October,
thereby including the first equinox and the perihelion passage. Jet
features were measured in individual images, which were used to perform
a statistical inversion. The study provides maps for the locations of
likeliest sources of jet activity on the comet's surface as a function
of time. The sources follow the subsolar latitude, show clustering
and a broadening of the activity band with time in the Northern
hemisphere. In the Southern hemisphere, they are not clustered but
show a broader spread over all longitudes which is either related to
the north-south dichotomy of the comet's topography or due to a higher
insolation during southern summer.
---------------------------------------------------------
Title: Post-perihelion photometry of dust grains in the coma of
67P Churyumov-Gerasimenko
Authors: Frattin, E.; Cremonese, G.; Simioni, E.; Bertini, I.;
Lazzarin, M.; Ott, T.; Drolshagen, E.; La Forgia, F.; Sierks,
H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.;
Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux,
J. -L.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller,
J.; Ferrari, S.; Ferri, F.; Fornasier, S.; Fulle, M.; Gicquel, A.;
Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid,
S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. -R.; Kührt,
E.; Küppers, M.; Lara, L. M.; Lopez Moreno, J. J.; Lucchetti, A.;
Marzari, F.; Massironi, M.; Mottola, S.; Naletto, G.; Oklay, N.;
Pajola, M.; Penasa, L.; Shi, X.; Thomas, N.; Tubiana, C.; Vincent,
J. -B.
2017MNRAS.469S.195F Altcode:
We present a photometric analysis of individual dust grains in the
coma of comet 67P/Churyumov-Gerasimenko using OSIRIS images taken from
2015 July to 2016 January. We analysed a sample of 555 taken during
18 d at heliocentric distances ranging between 1.25 and 2.04 au and at
nucleocentric distances between 80 and 437 km. An automated method to
detect the tracks was specifically developed. The images were taken
by OSIRIS NAC in four different filters: Near-IR (882 nm), Orange
(649 nm), FarOrange (649 nm) and Blue (480 nm). It was not always
possible to recognize all the grains in the four filters, hence we
measured the spectral slope in two wavelengths ranges: in the interval
[480-649] nm, for 1179 grains, and in the interval [649-882] nm, for
746 grains. We studied the evolution of the two populations' average
spectral slopes. The data result scattered around the average value in
the range [480-649] nm, while in the [649-882] nm we observe a slight
decreasing moving away from the Sun as well as a slight increasing with
the nucleocentric distance. A spectrophotometric analysis was performed
on a subsample of 339 grains. Three major groups were defined, based
on the spectral slope between [535-882] nm: (I) the steep spectra
that may be related with organic material, (II) the spectra with an
intermediate slope, likely a mixture of silicates and organics and (III)
flat spectra that may be associated with a high abundance of water ice.
---------------------------------------------------------
Title: Characterization of dust aggregates in the vicinity of the
Rosetta spacecraft
Authors: Güttler, C.; Hasselmann, P. H.; Li, Y.; Fulle, M.; Tubiana,
C.; Kovacs, G.; Agarwal, J.; Sierks, H.; Fornasier, S.; Hofmann,
M.; Gutiérrez Marqués, P.; Ott, T.; Drolshagen, E.; Bertini,
I.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman,
H.; A'Hearn, M. F.; Barucci, M. A.; Bodewits, D.; Bertaux, J. -L.;
Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.;
De Cecco, M.; Deller, J.; Geiger, B.; Groussin, O.; Gutiérrez, P. J.;
Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.;
Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.;
López-Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay,
N.; Pajola, M.; Shi, X.; Thomas, N.; Vincent, J. -B.
2017MNRAS.469S.312G Altcode:
In a Rosetta/OSIRIS imaging activity in 2015 June, we have observed the
dynamic motion of particles close to the spacecraft. Due to the focal
setting of the OSIRIS wide angle camera, these particles were blurred,
which can be used to measure their distances to the spacecraft. We
detected 109 dust aggregates over a 130 min long sequence, and find
that their sizes are around a millimetre and their distances cluster
between 2 and 40 m from the spacecraft. Their number densities are
about a factor 10 higher than expected for the overall coma and highly
fluctuating. Their velocities are small compared to the spacecraft
orbital motion and directed away from the spacecraft, towards the
comet. From this we conclude that they have interacted with the
spacecraft and assess three possible scenarios. In the likeliest
of the three scenarios, centimetre-sized aggregates collide with the
spacecraft and we would observe the fragments. Ablation of a dust layer
on the spacecraft's z panel (remote instrument viewing direction)
when rotated towards the Sun is a reasonable alternative. We could
also measure an acceleration for a subset of 18 aggregates, which
is directed away from the Sun and can be explain by a rocket effect,
which requires a minimum ice fraction of the order of 0.1 per cent.
---------------------------------------------------------
Title: Evidence of sub-surface energy storage in comet 67P from the
outburst of 2016 July 03
Authors: Agarwal, J.; Della Corte, V.; Feldman, P. D.; Geiger,
B.; Merouane, S.; Bertini, I.; Bodewits, D.; Fornasier, S.; Grün,
E.; Hasselmann, P.; Hilchenbach, M.; Höfner, S.; Ivanovski, S.;
Kolokolova, L.; Pajola, M.; Rotundi, A.; Sierks, H.; Steffl, A. J.;
Thomas, N.; A'Hearn, M. F.; Barbieri, C.; Barucci, M. A.; Bertaux,
J. -L.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson,
B.; Debei, S.; De Cecco, M.; Deller, J. F.; Feaga, L. M.; Fischer,
H.; Fulle, M.; Gicquel, A.; Groussin, O.; Güttler, C.; Gutiérrez,
P. J.; Hofmann, M.; Hornung, K.; Hviid, S. F.; Ip, W. -H.; Jorda, L.;
Keller, H. U.; Kissel, J.; Knollenberg, J.; Koch, A.; Koschny, D.;
Kramm, J. -R.; Kührt, E.; Küppers, M.; Lamy, P. L.; Langevin, Y.;
Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Lowry,
S. C.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Parker,
J. Wm.; Rodrigo, R.; Rynö, J.; Shi, X.; Stenzel, O.; Tubiana, C.;
Vincent, J. -B.; Weaver, H. A.; Zaprudin, B.
2017MNRAS.469S.606A Altcode: 2017arXiv171010235A
On 2016 July 03, several instruments onboard ESA's Rosetta spacecraft
detected signs of an outburst event on comet 67P, at a heliocentric
distance of 3.32 au from the Sun, outbound from perihelion. We here
report on the inferred properties of the ejected dust and the surface
change at the site of the outburst. The activity coincided with the
local sunrise and continued over a time interval of 14-68 min. It
left a 10-m-sized icy patch on the surface. The ejected material
comprised refractory grains of several hundred microns in size, and
sub-micron-sized water ice grains. The high dust mass production rate
is incompatible with the free sublimation of crystalline water ice
under solar illumination as the only acceleration process. Additional
energy stored near the surface must have increased the gas density. We
suggest a pressurized sub-surface gas reservoir, or the crystallization
of amorphous water ice as possible causes.
---------------------------------------------------------
Title: Seasonal mass transfer on the nucleus of comet
67P/Chuyumov-Gerasimenko
Authors: Keller, H. U.; Mottola, S.; Hviid, S. F.; Agarwal, J.;
Kührt, E.; Skorov, Y.; Otto, K.; Vincent, J. -B.; Oklay, N.;
Schröder, S. E.; Davidsson, B.; Pajola, M.; Shi, X.; Bodewits,
D.; Toth, I.; Preusker, F.; Scholten, F.; Sierks, H.; Barbieri,
C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.;
Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo,
V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.;
Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hofmann, M.; Ip, W. -H.;
Jorda, L.; Knollenberg, J.; Kramm, J. R.; Küppers, M.; Lara, L. -M.;
Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Naletto, G.; Tubiana,
C.; Thomas, N.
2017MNRAS.469S.357K Altcode: 2017arXiv170706812K
We collect observational evidence that supports the scheme of mass
transfer on the nucleus of comet 67P/Churyumov-Gerasimenko. The
obliquity of the rotation axis of 67P causes strong seasonal
variations. During perihelion the southern hemisphere is four times
more active than the north. Northern territories are widely covered
by granular material that indicates back fall originating from the
active south. Decimetre sized chunks contain water ice and their
trajectories are influenced by an antisolar force instigated by
sublimation. OSIRIS observations suggest that up to 20 per cent of
the particles directly return to the nucleus surface taking several
hours of traveltime. The back fall covered northern areas are active if
illuminated but produce mainly water vapour. The decimetre chunks from
the nucleus surface are too small to contain more volatile compounds
such as CO<SUB>2</SUB> or CO. This causes a north-south dichotomy of
the composition measurements in the coma. Active particles are trapped
in the gravitational minimum of Hapi during northern winter. They are
`shock frozen' and only re-activated when the comet approaches the
sun after its aphelion passage. The insolation of the big cavity is
enhanced by self-heating, I.e. reflection and IR radiation from the
walls. This, together with the pristinity of the active back fall,
explains the early observed activity of the Hapi region. Sobek may
be a role model for the consolidated bottom of Hapi. Mass transfer in
the case of 67P strongly influences the evolution of the nucleus and
the interpretation of coma measurements.
---------------------------------------------------------
Title: Investigating the physical properties of outbursts on comet
67P/Churyumov-Gerasimenko
Authors: Lin, Zhong-Yi; Knollenberg, J.; Vincent, J. -B.; A'Hearn,
M. F.; Ip, W. -H.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Rickman, H.; Keller, H. U.; Mottola, S.; Bodewits, D.;
Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese,
G.; Deller, J.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.;
Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler,
C.; Hofmann, M.; Hviid, S. F.; Jorda, L.; Kovacs, G.; Kramm, J. -R.;
Kührt, E.; Küppers, M.; Lai, I. -L.; Lara, L. M.; Lazzarin, M.;
Lee, J. -C.; López-Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay,
N.; Ott, T.; Drolshagen, E.; Shi, X.; Thomas, N.; Tubiana, C.
2017MNRAS.469S.731L Altcode:
Cometary outbursts on several comets have been observed
both by ground-based telescopes and by in situ instruments on
spacecraft. However, the mechanism behind these phenomena and their
physical properties are still unclear. The optical, spectrocopic
and infrared remote imaging system (OSIRIS) onboard the Rosetta
spacecraft provided first-hand information on the outbursts from comet
67P/Churyumov-Gerasimenko during its perihelion passage in 2015. The
physical properties of the outbursts can be investigated by examining
the time series of these high-resolution images. An analysis is made
of the wide- and narrow-angle images obtained during the monitoring
of the outburst sequences, which occurred between July and September
in 2015. A ring-masking technique is used to calculate the excess
brightness of the outbursts. The ejected mass and expansion velocity
of the outbursts is estimated from differences in images made with the
same filter (orange filter). The calculated excess brightness from
these outburst plumes ranges from a few per cent to 28 per cent. In
some major outbursts, the brightness contribution from the outburst
plume can be one or two times higher than that of the typical coma jet
activities. The strongest event was the perihelion outburst detected
just a few hours before perihelion. The mass ejection rate during a
generic outburst could reach a few per cent of the steady-state value of
the dust coma. Transient events are detected by studying the brightness
slope of the outburst plume with continuous streams of outflowing
gas and dust triggered by driving mechanisms, as yet not understood,
which remain active for several minutes to less than a few hours.
---------------------------------------------------------
Title: Modelling of the outburst on 2015 July 29 observed with OSIRIS
cameras in the Southern hemisphere of comet 67P/Churyumov-Gerasimenko
Authors: Gicquel, A.; Rose, M.; Vincent, J. -B.; Davidsson, B.;
Bodewits, D.; A'Hearn, M. F.; Agarwal, J.; Fougere, N.; Sierks, H.;
Bertini, I.; Lin, Z. -Y.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Rickman, H.; Keller, H. U.; Barucci, M. A.; Bertaux,
J. -L.; Besse, S.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Debei,
S.; Deller, J.; De Cecco, M.; Frattin, E.; El-Maarry, M. R.; Fornasier,
S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez,
P.; Güttler, C.; Höfner, S.; Hofmann, M.; Hu, X.; Hviid, S. F.; Ip,
W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt,
E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez;
Lowry, S.; Marzari, F.; Masoumzadeh, N.; Massironi, M.; Moreno,
F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Preusker, F.;
Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.
2017MNRAS.469S.178G Altcode: 2017arXiv170602729G
Images of the nucleus and the coma (gas and dust) of comet
67P/Churyumov- Gerasimenko have been acquired by the OSIRIS (Optical,
Spectroscopic and Infrared Remote Imaging System) cameras since 2014
March using both the wide-angle camera and the narrow-angle camera
(NAC). We use images from the NAC camera to study a bright outburst
observed in the Southern hemisphere on 2015 July 29. The high spatial
resolution of the NAC is needed to localize the source point of the
outburst on the surface of the nucleus. The heliocentric distance is
1.25 au and the spacecraft-comet distance is 186 km. Aiming to better
understand the physics that led to the outgassing, we used the Direct
Simulation Monte Carlo method to study the gas flow close to the nucleus
and the dust trajectories. The goal is to understand the mechanisms
producing the outburst. We reproduce the opening angle of the outburst
in the model and constrain the outgassing ratio between the outburst
source and the local region. The outburst is in fact a combination
of both gas and dust, in which the active surface is approximately
10 times more active than the average rate found in the surrounding
areas. We need a number of dust particles 7.83 × 10<SUP>11</SUP> to
6.90 × 10<SUP>15</SUP> (radius 1.97-185 μm), which correspond to a
mass of dust (220-21) × 10<SUP>3</SUP> kg.
---------------------------------------------------------
Title: The scattering phase function of comet
67P/Churyumov-Gerasimenko coma as seen from the Rosetta/OSIRIS
instrument
Authors: Bertini, I.; La Forgia, F.; Tubiana, C.; Güttler, C.; Fulle,
M.; Moreno, F.; Frattin, E.; Kovacs, G.; Pajola, M.; Sierks, H.;
Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller,
H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.;
Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.;
De Cecco, M.; Drolshagen, E.; Ferrari, S.; Ferri, F.; Fornasier, S.;
Gicquel, A.; Groussin, O.; Gutierrez, P. J.; Hasselmann, P. H.; Hviid,
S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Kührt,
E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.; Moreno,
J. J. Lopez; Lucchetti, A.; Marzari, F.; Massironi, M.; Mottola, S.;
Naletto, G.; Oklay, N.; Ott, T.; Penasa, L.; Thomas, N.; Vincent,
J. -B.
2017MNRAS.469S.404B Altcode:
The study of dust, the most abundant material in cometary nuclei,
is pivotal in understanding the original materials forming the
Solar system. Measuring the coma phase function provides a tool to
investigate the nature of cometary dust. Rosetta/OSIRIS sampled the
coma phase function of comet 67P/Churyumov-Gerasimenko, covering
a large phase angle range in a small amount of time. Twelve series
were acquired in the period from 2015 March to 2016 February for this
scientific purpose. These data allowed, after stray light removal,
measuring the phase function shape, its reddening, and phase reddening
while varying heliocentric and nucleocentric distances. Despite small
dissimilarities within different series, we found a constant overall
shape. The reflectance has a u-shape with minimum at intermediate
phase angles, reaching similar values at the smallest and largest
phase angle sampled. The comparison with cometary phase functions in
literature indicates OSIRIS curves being consistent with the ones
found in many other single comets. The dust has a negligible phase
reddening at α < 90°, indicating a coma dominated by single
scattering. We measured a reddening of [11-14] %/100 nm between 376
and 744 nm. No trend with heliocentric or nucleocentric distance was
found, indicating the coma doesn't change its spectrum with time. These
results are consistent with single coma grains and close-nucleus coma
photometric results. Comparison with nucleus photometry indicates a
different backscattering phase function shape and similar reddening
values only at α < 30°. At larger phase angles, the nucleus
becomes significantly redder than the coma.
---------------------------------------------------------
Title: Constraints on cometary surface evolution derived from a
statistical analysis of 67P's topography
Authors: Vincent, J. -B.; Hviid, S. F.; Mottola, S.; Kuehrt, E.;
Preusker, F.; Scholten, F.; Keller, H. U.; Oklay, N.; de Niem, D.;
Davidsson, B.; Fulle, M.; Pajola, M.; Hofmann, M.; Hu, X.; Rickman,
H.; Lin, Z. -Y.; Feller, C.; Gicquel, A.; Boudreault, S.; Sierks, H.;
Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; A'Hearn, M. F.;
Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo,
V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Groussin, O.;
Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Ip, W. -H.;
Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Küppers, M.;
Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto,
G.; Penasa, L.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.
2017MNRAS.469S.329V Altcode: 2017arXiv170700734V
We present a statistical analysis of the distribution of large-scale
topographic features on comet 67P/Churyumov-Gerasimenko. We observe that
the cumulative cliff height distribution across the surface follows a
power law with a slope equal to -1.69 ± 0.02. When this distribution
is studied independently for each region, we find a good correlation
between the slope of the power law and the orbital erosion rate of the
surface. For instance, the Northern hemisphere topography is dominated
by structures on the 100 m scale, while the Southern hemisphere
topography, illuminated at perihelion, is dominated by 10 m scale
terrain features. Our study suggests that the current size of a cliff
is controlled not only by material cohesion but also by the dominant
erosional process in each region. This observation can be generalized
to other comets, where we argue that primitive nuclei are characterized
by the presence of large cliffs with a cumulative height-power index
equal to or above -1.5, while older, eroded cometary surfaces have a
power index equal to or below -2.3. In effect, our model shows that
a measure of the topography provides a quantitative assessment of a
comet's erosional history, that is, its evolutionary age.
---------------------------------------------------------
Title: The pebbles/boulders size distributions on Sais: Rosetta's
final landing site on comet 67P/Churyumov-Gerasimenko
Authors: Pajola, M.; Lucchetti, A.; Fulle, M.; Mottola, S.; Hamm, M.;
Da Deppo, V.; Penasa, L.; Kovacs, G.; Massironi, M.; Shi, X.; Tubiana,
C.; Güttler, C.; Oklay, N.; Vincent, J. B.; Toth, I.; Davidsson,
B.; Naletto, G.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo,
R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn,
M. F.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.;
Debei, S.; De Cecco, M.; Deller, J.; El Maarry, M. R.; Fornasier, S.;
Frattin, E.; Gicquel, A.; Groussin, O.; Gutierrez, P. J.; Höfner,
S.; Hofmann, M.; Hviid, S. F.; Ip, W. H.; Jorda, L.; Knollenberg,
J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin,
M.; Moreno, J. J. Lopez; Marzari, F.; Michalik, H.; Preusker, F.;
Scholten, F.; Thomas, N.
2017MNRAS.469S.636P Altcode: 2017MNRAS.471..680P
By using the imagery acquired by the Optical, Spectroscopic, and
Infrared Remote Imaging System Wide-Angle Camera (OSIRIS WAC), we
prepare a high-resolution morphological map of the Rosetta Sais final
landing site, characterized by an outcropping consolidated terrain
unit, a coarse boulder deposit and a fine particle deposit. Thanks
to the 0.014 m resolution images, we derive the pebbles/boulders
size-frequency distribution (SFD) of the area in the size range of
0.07-0.70 m. Sais' SFD is best fitted with a two-segment differential
power law: the first segment is in the range 0.07-0.26 m, with an index
of -1.7 ± 0.1, while the second is in the range 0.26-0.50 m, with
an index of -4.2 +0.4/-0.8. The `knee' of the SFD, located at 0.26 m,
is evident both in the coarse and fine deposits. When compared to the
Agilkia Rosetta Lander Imaging System images, Sais surface is almost
entirely free of the ubiquitous, cm-sized debris blanket observed
by Philae. None the less, a similar SFD behaviour of Agilkia, with a
steeper distribution above ∼0.3 m, and a flatter trend below that,
is observed. The activity evolution of 67P along its orbit provides
a coherent scenario of how these deposits were formed. Indeed,
different lift pressure values occurring on the two locations and at
different heliocentric distances explain the presence of the cm-sized
debris blanket on Agilkia observed at 3.0 au inbound. Contrarily, Sais
activity after 2.1 au outbound has almost completely eroded the fine
deposits fallen during perihelion, resulting in an almost dust-free
surface observed at 3.8 au.
---------------------------------------------------------
Title: The opposition effect of 67P/Churyumov-Gerasimenko on
post-perihelion Rosetta images
Authors: Hasselmann, P. H.; Barucci, M. A.; Fornasier, S.; Feller, C.;
Deshapriya, J. D. P.; Fulchignoni, M.; Jost, B.; Sierks, H.; Barbieri,
C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M.;
Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson,
B.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Gaskell, R. W.;
Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid,
S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kovacs,
G.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, M. L.; Lazzarin, M.;
Lopez-Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay,
N.; Pommerol, A.; Thomas, N.; Tubiana, C.; Vincent, J. -B.
2017MNRAS.469S.550H Altcode:
High-resolution OSIRIS/Rosetta images of 67P/Churyumov-Gerasimenko
acquired on the night run of 2016 April 9-10 show, at large scale,
an opposition effect (OE) spot sweeping across Imhotep as the phase
angle ranges from 0° to 17°. In this work, we fitted the phase curve
of the whole surface imaged as well as three particular features using
both the linear-exponential and Hapke models. These features encompass
different types of spectral behaviour: a circular mesa, one venous
structure and an assemblage of bright spots, going from red to blue
colours. Both the Hapke and linear-exponential parameters indicate a
stepwise sharpening of the OE from bright spots to circular mesa. Yet
a very broad nonlinear phase curve is verified and no sign of sharp OE
associated with a coherent-backscattering mechanism is observed. We
estimate that the 67P surface is dominated by opaque, desiccated and
larger-than-wavelength irregular grains. Veins and bright spots display
photometric properties consistent with surfaces becoming slightly
brighter as they are enriched by high-albedo ice grains. We also report
the estimation of normal albedo for all cometary regions observed
throughout the image sequence. Comparison to pre-perihelion results
indicates that far better insolation of northern brighter regions,
I.e. Hapi, Hathor and Seth, is sufficient to explain mismatches on the
photometric parameters. However, metre-scale photometric analysis of
the Imhotep-Ash boundary area advocates for mild darkening (<7 per
cent) of the surface at local scale.
---------------------------------------------------------
Title: The highly active Anhur-Bes regions in the
67P/Churyumov-Gerasimenko comet: results from OSIRIS/ROSETTA
observations
Authors: Fornasier, S.; Feller, C.; Lee, J. -C.; Ferrari, S.;
Massironi, M.; Hasselmann, P. H.; Deshapriya, J. D. P.; Barucci,
M. A.; El-Maarry, M. R.; Giacomini, L.; Mottola, S.; Keller, H. U.;
Ip, W. -H.; Lin, Z. -Y.; Sierks, H.; Barbieri, C.; Lamy, P. L.;
Rodrigo, R.; Koschny, D.; Rickman, H.; Agarwal, J.; A'Hearn, M.;
Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson,
B.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Groussin, O.;
Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Jorda,
L.; Knollenberg, J.; Kovacs, G.; Kramm, R.; Kührt, E.; Küppers, M.;
Lara, M. L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto,
G.; Oklay, N.; Pajola, M.; Shi, X.; Thomas, N.; Toth, I.; Tubiana,
C.; Vincent, J. -B.
2017MNRAS.469S..93F Altcode: 2017arXiv170702945F
The Southern hemisphere of the 67P/Churyumov-Gerasimenko comet has
become visible from Rosetta only since 2015 March. It was illuminated
during the perihelion passage and therefore it contains the regions
that experienced the strongest heating and erosion rates, thus exposing
the sub-surface most pristine material. In this work we investigate,
thanks to the OSIRIS images, the geomorphology, the spectrophotometry
and some transient events of two Southern hemisphere regions: Anhur
and part of Bes. Bes is dominated by outcropping consolidated terrain
covered with fine particle deposits, while Anhur appears strongly eroded
with elongated canyon-like structures, scarp retreats, different kinds
of deposits and degraded sequences of strata indicating a pervasive
layering. We discovered a new 140 m long and 10 m high scarp formed
in the Anhur-Bes boundary during/after the perihelion passage, close
to the area where exposed CO<SUB>2</SUB> and H<SUB>2</SUB>O ices were
previously detected. Several jets have been observed originating from
these regions, including the strong perihelion outburst, an active
pit and a faint optically thick dust plume. We identify several areas
with a relatively bluer slope (i.e. a lower spectral slope value) than
their surroundings, indicating a surface composition enriched with
some water ice. These spectrally bluer areas are observed especially
in talus and gravitational accumulation deposits where freshly exposed
material had fallen from nearby scarps and cliffs. The investigated
regions become spectrally redder beyond 2 au outbound when the dust
mantle became thicker, masking the underlying ice-rich layers.
---------------------------------------------------------
Title: Long-term survival of surface water ice on comet 67P
Authors: Oklay, N.; Mottola, S.; Vincent, J. -B.; Pajola, M.;
Fornasier, S.; Hviid, S. F.; Kappel, D.; Kührt, E.; Keller, H. U.;
Barucci, M. A.; Feller, C.; Preusker, F.; Scholten, F.; Hall, I.;
Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.;
Rickman, H.; A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Bodewits,
D.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; De
Cecco, M.; Deller, J.; Deshapriya, J. D. P.; Fulle, M.; Gicquel, A.;
Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hasselmann, P. H.;
Hofmann, M.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.;
Kramm, J. -R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.;
Moreno, J. J. Lopez; Lucchetti, A.; Marzari, F.; Masoumzadeh, N.;
Naletto, G.; Pommerol, A.; Shi, X.; Thomas, N.; Tubiana, C.
2017MNRAS.469S.582O Altcode:
Numerous water-ice-rich deposits surviving more than several months
on comet 67P/Churyumov-Gerasimenko were observed during the Rosetta
mission. We announce the first-time detection of water-ice features
surviving up to 2 yr since their first observation via OSIRIS (Optical,
Spectroscopic, and Infrared Remote Imaging System) NAC (narrow angle
camera). Their existence on the nucleus of comet 67P at the arrival of
the Rosetta spacecraft suggests that they were exposed to the surface
during the comet's previous orbit. We investigated the temporal
variation of large water-ice patches to understand the long-term
sustainability of water ice on cometary nuclei on time-scales of
months and years. Large clusters are stable over typical periods
of 0.5 yr and reduce their size significantly around the comet's
perihelion passage, while small exposures disappear. We characterized
the temporal variation of their multispectral signatures. In large
clusters, dust jets were detected, whereas in large isolated ones no
associated activity was detected. Our thermal analysis shows that the
long-term sustainability of water-ice-rich features can be explained by
the scarce energy input available at their locations over the first half
year. However, the situation reverses for the period lasting several
months around perihelion passage. Our two end-member mixing analysis
estimates a pure water-ice equivalent thickness up to 15 cm within one
isolated patch, and up to 2 m for the one still observable through the
end of the mission. Our spectral modelling estimates up to 48 per cent
water-ice content for one of the large isolated feature, and up to 25
per cent water ice on the large boulders located within clusters.
---------------------------------------------------------
Title: A three-dimensional modelling of the layered structure of
comet 67P/Churyumov-Gerasimenko
Authors: Penasa, L.; Massironi, M.; Naletto, G.; Simioni, E.; Ferrari,
S.; Pajola, M.; Lucchetti, A.; Preusker, F.; Scholten, F.; Jorda,
L.; Gaskell, R.; Ferri, F.; Marzari, F.; Davidsson, B.; Mottola,
S.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny,
D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci,
M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei,
S.; De Cecco, M.; Deller, J.; Feller, C.; Fornasier, S.; Frattin, E.;
Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.;
Hviid, S. F.; Ip, W. H.; Knollenberg, J.; Kramm, J. R.; Kührt, E.;
Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; Lee, J. -C.;
Lopez Moreno, J. J.; Oklay, N.; Shi, X.; Thomas, N.; Tubiana, C.;
Vincent, J. B.
2017MNRAS.469S.741P Altcode:
We provide a three-dimensional model of the inner layered structure of
comet 67P based on the hypothesis of an extended layering independently
wrapping each lobe. A large set of terrace orientations was collected
on the latest shape model and then used as a proxy for the local
orientation of the surfaces of discontinuity which defines the
layers. We modelled the terraces as a family of concentric ellipsoidal
shells with fixed axis ratios, producing a model that is completely
defined by just eight free parameters. Each lobe of 67P has been
modelled independently, and the two sets of parameters have been
estimated by means of non-linear optimization of the measured terrace
orientations. The proposed model is able to predict the orientation of
terraces, the elongation of cliffs, the linear traces observed in the
Wosret and Hathor regions and the peculiar alignment of boulder-like
features which has been observed in the Hapi region, which appears to
be related to the inner layering of the big lobe. Our analysis allowed
us to identify a plane of junction between the two lobes, further
confirming the independent nature of the lobes. Our layering models
differ from the best-fitting topographic ellipsoids of the surface,
demonstrating that the terraces are aligned to an internal structure of
discontinuities, which is unevenly exposed on the surface, suggesting
a complex history of localized material removal from the nucleus.
---------------------------------------------------------
Title: Geomorphological and spectrophotometric analysis of Seth's
circular niches on comet 67P/Churyumov-Gerasimenko using OSIRIS images
Authors: Lucchetti, A.; Pajola, M.; Fornasier, S.; Mottola, S.; Penasa,
L.; Jorda, L.; Cremonese, G.; Feller, C.; Hasselmann, P. H.; Massironi,
M.; Ferrari, S.; Naletto, G.; Oklay, N.; Sierks, H.; Barbieri,
C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller,
H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. L.;
Bertini, I.; Boudreault, S.; Da Deppo, V.; Davidsson, B.; Debei, S.;
De Cecco, M.; Deller, J.; Fulle, M.; Groussin, O.; Gutierrez, P. J.;
Güttler, C.; Hoffman, M.; Hviid, S. F.; Ip, W. H.; Knollenberg, J.;
Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.;
La Forgia, F.; Lin, L. Z.; Lopez Moreno, J. J.; Marzari, F.; Preusker,
F.; Scholten, F.; Shi, X.; Thomas, N.; Tubiana, C.; Vincent, J. B.
2017MNRAS.469S.238L Altcode:
We provide a detailed geomorphological and spectrophotometric analysis
of the circular niches located on the Seth region of 67P using OSIRIS
images. The features can be related to landslide events that occurred
on 67P and shaped its surface, as the recent Aswan cliff collapse
detected in the same region. We therefore provide an analysis of the
area pre- and post-perihelion suggesting that no specific changes have
been observed. To assess this, after performing a geomorphological
map of the area that allows us to identify different terrain units,
we computed the boulders cumulative size frequency distribution (SFD)
of the niches, before and after the perihelion passage. The niches
SFDs are characterized by a similar trend with two different power-law
indices within the same deposit: lower power-law value (between -2.3
and -2.7) for boulders smaller than 5 m and steeper power-law value
(between -4.7 and -5.0) for boulders larger than 5 m. These trends
suggest that smaller boulders have evolved and progressively have
been depleted (lower power-law index), while bigger boulders are more
representative of the event that generated the deposit and are less
degraded. Then, we perform the spectrophotometric analysis of this
region comparing pre- and post-perihelion results. We found colour
changes within the area, in particular brighter patches related to
the presence of exposed water ice mixed to the refractory materials
have been detected in the post-perihelion images.
---------------------------------------------------------
Title: Thermal modelling of water activity on comet
67P/Churyumov-Gerasimenko with global dust mantle and plural
dust-to-ice ratio
Authors: Hu, X.; Shi, X.; Sierks, H.; Blum, J.; Oberst, J.; Fulle,
M.; Kührt, E.; Güttler, C.; Gundlach, B.; Keller, H. U.; Mottola,
S.; Pajola, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.;
Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux,
J. -L.; Bertini, I.; Boudreault, S.; Büttner, I.; Cremonese, G.;
Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.;
Fornasier, S.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marqués,
P.; Hall, I.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.;
Knollenberg, J.; Kovacs, G.; Kramm, J. R.; Küppers, M.; Lara, L. M.;
Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay,
N.; Richards, M. L.; Ripken, J.; Thomas, N.; Tubiana, C.; Vincent,
J. -B.
2017MNRAS.469S.295H Altcode:
We perform a thermo-physical analysis on water activity of comet
67P/Churyumov-Gerasimenko (67P). The sublimation of water is
assumed to occur from beneath a global, desiccated dust mantle over
the irregular-shaped nucleus. The concept of two thermal models,
the recipe of model formulation and the strategy of application to
comet 67P are described. For an accurate and efficient evaluation
of energy input by insolation and self-heating over the nucleus, a
Landscape data base is devised based on polyhedral shape models of
the nucleus. We apply the thermal models to investigate the impact
of certain parameters of nucleus properties on water production. It
is found that the measured water production of 67P can be overall
attributed to sublimation of water ice with a mass abundance of a few
to 10 per cent beneath a uniform dust mantle of several millimetres
to one centimetre in thickness. Insofar as 67P is concerned, we argue
against the necessity to invoke assumptions on localized water activity,
or on the distinction of active/dormant surface areas.
---------------------------------------------------------
Title: Anomalous Surge of the White-Light Corona at the Onset of
the Declining Phase of Solar Cycle 24
Authors: Lamy, P.; Boclet, B.; Wojak, J.; Vibert, D.
2017SoPh..292...60L Altcode:
In late 2014, when the current Solar Cycle 24 entered its declining
phase, the white-light corona as observed by the LASCO-C2 coronagraph
underwent an unexpected surge that increased its global radiance
by 60%, reaching a peak value comparable to the peak values of the
more active Solar Cycle 23. A comparison of the temporal variation
of the white-light corona with the variations of several indices and
proxies of solar activity indicate that it best matches the variation
of the total magnetic field. The daily variations point to a localized
enhancement or bulge in the electron density that persisted for several
months. Carrington maps of the radiance and of the HMI photospheric
field allow connecting this bulge to the emergence of the large
sunspot complex AR 12192 in October 2014, the largest since AR 6368
observed in November 1990. The resulting unusually high increase
of the magnetic field and the distortion of the neutral sheet in a
characteristic inverse S-shape caused the coronal plasma to be trapped
along a similar pattern. A 3D reconstruction of the electron density
based on time-dependent solar rotational tomography supplemented by
2D inversion of the coronal radiance confirms the morphology of the
bulge and reveals that its level was well above the standard models
of a corona of the maximum type, by typically a factor of 3. A rather
satisfactory agreement is found with the results of the thermodynamic
MHD model produced by Predictive Sciences, although discrepancies
are noted. The specific configuration of the magnetic field that led
to the coronal surge resulted from the interplay of various factors
prevailing at the onset of the declining phase of the solar cycles,
which was particularly efficient in the case of Solar Cycle 24.
---------------------------------------------------------
Title: Multivariate statistical analysis of OSIRIS/Rosetta
spectrophotometric data of comet 67P/Churyumov-Gerasimenko
Authors: Perna, D.; Fulchignoni, M.; Barucci, M. A.; Fornasier, S.;
Feller, C.; Deshapriya, J. D. P.; Hasselmann, P. H.; Sierks, H.;
Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.;
A'Hearn, M.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo,
V.; Davidsson, B.; Debei, S.; Deller, J.; De Cecco, M.; El-Maarry,
M. R.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.;
Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.;
Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L. M.;
Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay,
N.; Thomas, N.; Tubiana, C.; Vincent, J. -B.
2017A&A...600A.115P Altcode:
Context. The ESA Rosetta mission explored comet
67P/Churyumov-Gerasimenko in 2014-2016, following its target before
and after the perihelion passage on 13 August 2015. The NAC camera of
the OSIRIS imaging system allowed to map the nucleus surface acquiring
images with different filters in the visible wavelength range. <BR />
Aims: Here we study the spectrophotometric behaviour of the nucleus
by a multivariate statistical analysis, aiming to distinguish
homogeneous groups and to constrain the bulk composition. <BR />
Methods: We applied the G-mode clustering algorithm to 16 OSIRIS
data cubes acquired on 5-6 August 2014 (mostly covering the northern
hemisphere) and 2 May 2015 (mostly covering the southern hemisphere),
selected to have complete coverage of the comet's surface with similar
observing conditions. <BR /> Results: We found four similar homogeneous
groups for each of the analysed cubes. The first group corresponds
to the average spectrophotometric behaviour of the nucleus. The
second (spectrally redder) and the third (spectrally bluer) groups
are found in regions that were already found to deviate from the
average terrain of the comet by previous studies. A fourth group
(characterised by enhancements of the flux at 700-750 nm and 989 nm,
possibly due to H<SUB>2</SUB>O<SUP>+</SUP> and/or NH<SUB>2</SUB>
emissions) seems connected with the cometary activity rather than
with the bulk composition. <BR /> Conclusions: While our aim in this
work was to study the spectrophotometric behaviour of the nucleus
of 67P/Churyumov-Gerasimenko as a whole, we found that a follow-up
application of the G-mode to smaller regions of the surface could
be useful in particular to identify and study the temporal evolution
of ice patches, as well as to constrain the composition and physical
processes behind the emission of dust jets.
---------------------------------------------------------
Title: Opposition effect on comet 67P/Churyumov-Gerasimenko using
Rosetta-OSIRIS images
Authors: Masoumzadeh, N.; Oklay, N.; Kolokolova, L.; Sierks, H.;
Fornasier, S.; Barucci, M. A.; Vincent, J. -B.; Tubiana, C.; Güttler,
C.; Preusker, F.; Scholten, F.; Mottola, S.; Hasselmann, P. H.; Feller,
C.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.;
A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo,
V.; Davidsson, B. J. R.; Debei, S.; De Cecco, M.; Fulle, M.; Gicquel,
A.; Groussin, O.; Gutiérrez, P. J.; Hall, I.; Hofmann, M.; Hviid,
S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kovacs,
G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin,
M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Shi, X.; Thomas, N.
2017A&A...599A..11M Altcode:
<BR /> Aims: We aim to explore the behavior of the opposition effect as
an important tool in optical remote sensing on the nucleus of comet 67P/
Churyumov-Gerasimenko (67P), using Rosetta-OSIRIS images acquired in
different filters during the approach phase, July-August 2014 and the
close flyby images on 14 of February 2015, which contain the spacecraft
shadow. <BR /> Methods: We based our investigation on the global and
local brightness from the surface of 67P with respect to the phase
angle, also known as phase curve. The local phase curve corresponds to
a region that is located at the Imhotep-Ash boundary of 67P. Assuming
that the region at the Imhotep-Ash boundary and the entire nucleus
have similar albedo, we combined the global and local phase curves to
study the opposition-surge morphology and constrain the structure and
properties of 67P. The model parameters were furthermore compared with
other bodies in the solar system and existing laboratory study. <BR />
Results: We found that the morphological parameters of the opposition
surge decrease monotonically with wavelength, whereas in the case of
coherent backscattering this behavior should be the reverse. The results
from comparative analysis place 67P in the same category as the two
Mars satellites, Phobos and Deimos, which are notably different from
all airless bodies in the solar system. The similarity between the
surface phase function of 67P and a carbon soot sample at extremely
small angles is identified, introducing regolith at the boundary of
the Imhotep-Ash region of 67P as a very dark and fluffy layer.
---------------------------------------------------------
Title: Surface changes on comet 67P/Churyumov-Gerasimenko suggest
a more active past
Authors: El-Maarry, M. Ramy; Groussin, O.; Thomas, N.; Pajola, M.;
Auger, A. -T.; Davidsson, B.; Hu, X.; Hviid, S. F.; Knollenberg, J.;
Güttler, C.; Tubiana, C.; Fornasier, S.; Feller, C.; Hasselmann, P.;
Vincent, J. -B.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.;
Koschny, D.; Keller, H. U.; Rickman, H.; A'Hearn, M. F.; Barucci,
M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.;
Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.;
Deshapriya, J. D. P.; Fulle, M.; Gutierrez, P. J.; Hofmann, M.; Ip,
W. -H.; Jorda, L.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.;
Lara, L. M.; Lazzarin, M.; Lin, Z. -Yi; Lopez Moreno, J. J.; Marchi,
S.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pommerol, A.;
Preusker, F.; Scholten, F.; Shi, X.
2017Sci...355.1392E Altcode:
The Rosetta spacecraft spent ~2 years orbiting comet
67P/Churyumov-Gerasimenko, most of it at distances that allowed surface
characterization and monitoring at submeter scales. From December
2014 to June 2016, numerous localized changes were observed, which
we attribute to cometary-specific weathering, erosion, and transient
events driven by exposure to sunlight and other processes. While the
localized changes suggest compositional or physical heterogeneity,
their scale has not resulted in substantial alterations to the
comet’s landscape. This suggests that most of the major landforms were
created early in the comet’s current orbital configuration. They may
even date from earlier if the comet had a larger volatile inventory,
particularly of CO or CO<SUB>2</SUB> ices, or contained amorphous ice,
which could have triggered activity at greater distances from the Sun.
---------------------------------------------------------
Title: The pristine interior of comet 67P revealed by the combined
Aswan outburst and cliff collapse
Authors: Pajola, M.; Höfner, S.; Vincent, J. B.; Oklay, N.; Scholten,
F.; Preusker, F.; Mottola, S.; Naletto, G.; Fornasier, S.; Lowry, S.;
Feller, C.; Hasselmann, P. H.; Güttler, C.; Tubiana, C.; Sierks, H.;
Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller,
H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.;
Bertini, I.; Besse, S.; Boudreault, S.; Cremonese, G.; da Deppo,
V.; Davidsson, B.; Debei, S.; de Cecco, M.; Deller, J.; Deshapriya,
J. D. P.; El-Maarry, M. R.; Ferrari, S.; Ferri, F.; Fulle, M.;
Groussin, O.; Gutierrez, P.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.;
Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. R.; Kührt, E.;
Küppers, M.; Lara, L. M.; Lin, Z. -Y.; Lazzarin, M.; Lucchetti, A.;
Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Michalik, H.; Penasa,
L.; Pommerol, A.; Simioni, E.; Thomas, N.; Toth, I.; Baratti, E.
2017NatAs...1E..92P Altcode:
Outbursts occur commonly on comets<SUP>1</SUP> with different
frequencies and scales<SUP>2,3</SUP>. Despite multiple observations
suggesting various triggering processes<SUP>4,5</SUP>, the driving
mechanism of such outbursts is still poorly understood. Landslides have
been invoked<SUP>6</SUP> to explain some outbursts on comet 103P/Hartley
2, although the process required a pre-existing dust layer on the
verge of failure. The Rosetta mission observed several outbursts from
its target comet 67P/Churyumov-Gerasimenko, which were attributed
to dust generated by the crumbling of materials from collapsing
cliffs<SUP>7,8</SUP>. However, none of the aforementioned works included
definitive evidence that landslides occur on comets. Amongst the many
features observed by Rosetta on the nucleus of the comet, one peculiar
fracture, 70 m long and 1 m wide, was identified on images obtained
in September 2014 at the edge of a cliff named Aswan<SUP>9</SUP>. On
10 July 2015, the Rosetta Navigation Camera captured a large plume
of dust that could be traced back to an area encompassing the Aswan
escarpment<SUP>7</SUP>. Five days later, the OSIRIS camera observed
a fresh, sharp and bright edge on the Aswan cliff. Here we report
the first unambiguous link between an outburst and a cliff collapse
on a comet. We establish a new dust-plume formation mechanism that
does not necessarily require the breakup of pressurized crust or
the presence of supervolatile material, as suggested by previous
studies<SUP>7</SUP>. Moreover, the collapse revealed the fresh icy
interior of the comet, which is characterized by an albedo >0.4,
and provided the opportunity to study how the crumbling wall settled
down to form a new talus.
---------------------------------------------------------
Title: Different Origins or Different Evolutions? Decoding the
Spectral Diversity Among C-type Asteroids
Authors: Vernazza, P.; Castillo-Rogez, J.; Beck, P.; Emery, J.;
Brunetto, R.; Delbo, M.; Marsset, M.; Marchis, F.; Groussin, O.;
Zanda, B.; Lamy, P.; Jorda, L.; Mousis, O.; Delsanti, A.; Djouadi,
Z.; Dionnet, Z.; Borondics, F.; Carry, B.
2017AJ....153...72V Altcode: 2017arXiv170106603V
Anhydrous pyroxene-rich interplanetary dust particles (IDPs) have been
proposed as surface analogs for about two-thirds of all C-complex
asteroids. However, this suggestion appears to be inconsistent with
the presence of hydrated silicates on the surfaces of some of these
asteroids, including Ceres. Here, we report the presence of enstatite
(pyroxene) on the surface of two C-type asteroids (Ceres and Eugenia)
based on their spectral properties in the mid-infrared range. The
presence of this component is particularly unexpected in the case
of Ceres, because most thermal evolution models predict a surface
consisting of hydrated compounds only. The most plausible scenario is
that Ceres’ surface has been partially contaminated by exogenous
enstatite-rich material, possibly coming from the Beagle asteroid
family. This scenario questions a similar origin for Ceres and the
remaining C-types, and it possibly supports recent results obtained
by the Dawn mission (NASA) that Ceres may have formed in the very
outer solar system. Concerning the smaller D ∼ 200 km C-types such as
Eugenia, both their derived surface composition (enstatite and amorphous
silicates) and low density (<1.5 g cm<SUP>-3</SUP>) suggest that
these bodies accreted from the same building blocks, namely chondritic
porous, pyroxene-rich IDPs and volatiles (mostly water ice), and that a
significant volume fraction of these bodies has remained unaffected by
hydrothermal activity likely implying a late accretion. In addition,
their current heliocentric distance may best explain the presence
or absence of water ice at their surfaces. Finally, we raise the
possibility that CI chondrites, Tagish-Lake-like material, or hydrated
IDPs may be representative samples of the cores of these bodies.
---------------------------------------------------------
Title: Regional surface morphology of comet 67P/Churyumov-Gerasimenko
from Rosetta/OSIRIS images: The southern hemisphere (Corrigendum)
Authors: El-Maarry, M. R.; Thomas, N.; Gracia-Berná, A.; Pajola,
M.; Lee, J. -C.; Massironi, M.; Davidsson, B.; Marchi, S.; Keller,
H. U.; Hviid, S. F.; Besse, S.; Sierks, H.; Barbieri, C.; Lamy,
P. L.; Koschny, D.; Rickman, H.; Rodrigo, R.; A'Hearn, M. F.; Auger,
A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.;
Cremonese, G.; Da Deppo, V.; De Cecco, M.; Debei, S.; Güttler, C.;
Fornasier, S.; Fulle, M.; Giacomini, L.; Groussin, O.; Gutierrez,
P. J.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm,
J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez
Moreno, J. J.; Marschall, R.; Marzari, F.; Naletto, G.; Oklay, N.;
Pommerol, A.; Preusker, F.; Scholten, F.; Tubiana, C.; Vincent, J. -B.
2017A&A...598C...2E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Coronal mass ejections and solar wind mass fluxes over the
heliosphere during solar cycles 23 and 24 (1996-2014)
Authors: Lamy, P.; Floyd, O.; Quémerais, E.; Boclet, B.; Ferron, S.
2017JGRA..122...50L Altcode:
Coronal mass ejections (CMEs) play a major role in the heliosphere,
and their contribution to the solar wind mass flux, already considered
in the Skylab and Solwind eras with conflicting results, is reexamined
in the light of 19 years (1996-2014) of SOHO observations with the Large
Angle and Spectroscopic Coronagraph (LASCO-C2) for the CMEs and extended
for the first time to all latitudes thanks to the whole-heliosphere data
from the Solar Wind ANisotropies (SWAN) instrument supplemented by in
situ data aggregated in the OMNI database. First, several mass estimates
reported in the ARTEMIS (Automated Recognition of Transient Events
and Marseille Inventory from Synoptic maps) catalog of LASCO CMEs are
compared with determinations based on the combined observations with the
twin STEREO/Sun Earth Connection Coronal and Heliospheric Investigation
coronagraphs in order to ascertain their validity. A simple geometric
model of the CMEs is introduced to generate Carrington maps of their
mass flux and then to produce annualized synoptic maps. The Lyman
α SWAN data are inverted to similarly produce synoptic maps to be
compared with those of the CME flux. The ratio of the annualized CME
to solar wind mass flux is found to closely track the solar cycle over
the heliosphere. In the near-ecliptic region and at latitudes up to
∼55°, this ratio was negligibly small during the solar minima of
cycles 22/23 and 23/24 and rose to 6% and 5%, respectively, at the
maximum of solar cycles 23 and 24. These maximum ratios increased at
higher latitudes, but this result is likely biased by the inherent
limitation of determining the true latitude of CMEs.
---------------------------------------------------------
Title: A mini outburst from the nightside of comet
67P/Churyumov-Gerasimenko observed by the OSIRIS camera on Rosetta
Authors: Knollenberg, J.; Lin, Z. Y.; Hviid, S. F.; Oklay, N.; Vincent,
J. -B.; Bodewits, D.; Mottola, S.; Pajola, M.; Sierks, H.; Barbieri,
C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.;
Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; Davidsson,
B.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.;
Groussin, O.; Gutiérrez, P. J.; Ip, W. -H.; Jorda, L.; Keller, H. U.;
Kührt, E.; Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.;
Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Thomas, N.; Güttler,
C.; Preusker, F.; Scholten, F.; Tubiana, C.
2016A&A...596A..89K Altcode:
Context. On 12 March 2015 the OSIRIS WAC camera onboard the ESA
Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko observed
a small outburst originating from the Imhotep region at the foot of
the big lobe of the comet. These measurements are unique since it was
the first time that the initial phase of a transient outburst event
could be directly observed. <BR /> Aims: We investigate the evolution
of the dust jet in order to derive clues about the outburst source
mechanism and the ejected dust particles, in particular the dust
mass, dust-to-gas ratio and the particle size distribution. <BR />
Methods: Analysis of the images and of the observation geometry using
comet shape models in combination with gasdynamic modeling of the
transient dust jet were the main tools used in this study. Synthetic
images were computed for comparison with the observations. <BR />
Results: Analysis of the geometry revealed that the source region was
not illuminated until 1.5 h after the event implying true nightside
activity was observed. The outburst lasted for less than one hour and
the average dust production rate during the initial four minutes was
of the order of 1 kg/s. During this time the outburst dust production
rate was approximately constant, no sign for an initial explosion
could be detected. For dust grains between 0.01-1 mm a power law size
distribution characterized by an index of about 2.6 provides the best
fit to the observed radiance profiles. The dust-to-gas ratio of the
outburst jet is in the range 0.6-1.8.
---------------------------------------------------------
Title: Rosetta’s comet 67P/Churyumov-Gerasimenko sheds its dusty
mantle to reveal its icy nature
Authors: Fornasier, S.; Mottola, S.; Keller, H. U.; Barucci, M. A.;
Davidsson, B.; Feller, C.; Deshapriya, J. D. P.; Sierks, H.; Barbieri,
C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M.;
Agarwal, J.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Cremonese, G.;
Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; El-Maarry, M. R.;
Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann,
M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs,
G.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, M. L.; Lazzarin, M.;
Moreno, J. J. Lopez; Marzari, F.; Massironi, M.; Naletto, G.; Oklay,
N.; Pajola, M.; Pommerol, A.; Preusker, F.; Scholten, F.; Shi, X.;
Thomas, N.; Toth, I.; Tubiana, C.; Vincent, J. -B.
2016Sci...354.1566F Altcode:
The Rosetta spacecraft has investigated comet 67P/Churyumov-Gerasimenko
from large heliocentric distances to its perihelion passage and
beyond. We trace the seasonal and diurnal evolution of the colors of the
67P nucleus, finding changes driven by sublimation and recondensation of
water ice. The whole nucleus became relatively bluer near perihelion,
as increasing activity removed the surface dust, implying that water
ice is widespread underneath the surface. We identified large (1500
square meters) ice-rich patches appearing and then vanishing in about
10 days, indicating small-scale heterogeneities on the nucleus. Thin
frosts sublimating in a few minutes are observed close to receding
shadows, and rapid variations in color are seen on extended areas
close to the terminator. These cyclic processes are widespread and
lead to continuously, slightly varying surface properties.
---------------------------------------------------------
Title: Mapping of the source regions of the dust jets on comet
67P/Churyumov-Gerasimenko
Authors: Lai, I. L.; Ip, W. H.; Lee, J. C.; Lin, Z. Y.; Vincent,
J. B.; Hartogh, P.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rickman,
H.; Keller, H. U.
2016AGUFM.P43A2087L Altcode:
Because of the inclination of the rotational axis to the orbital
plane and the orbital motion around the Sun, the sunlit regions on
the nucleus surface of comet 67P/Churyumov-Gerasimenko moved from
the northern hemisphere to the sourthern hemisphere between August,
2014 and August, 2015. From the comparison of the dust jet features in
images taken at successive time series, the footpoints of these jets
can be identified by a projection method. The distributiosn of the
corresponding source regions can be compared with the geomorphology
of the nucleus surface from inbound to outbound. The correlation
of the dust jet activity with the volatile outgassing phenomenon as
monitored by different scientific instruments onboard Rosetta will
provide important information on the sublimation process.
---------------------------------------------------------
Title: Gas outflow and dust transport of comet
67P/Churyumov-Gerasimenko
Authors: Lai, Ian-Lin; Ip, Wing-Huen; Su, Cheng-Chin; Wu, Jong-Shinn;
Lee, Jui-Chi; Lin, Zhong-Yi; Liao, Ying; Thomas, Nicolas; Sierks,
Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny,
Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica; A'Hearn,
Michael F.; Barucci, Maria Antonella; Bertaux, Jean-Loup; Bertini,
Ivano; Boudreault, Steven; Cremonese, Gabriele; Da Deppo, Vania;
Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Deller, Jakob;
Fornasier, Sonia; Fulle, Marco; Groussin, Olivier; Gutiérrez, Pedro
J.; Güttler, Carsten; Hofmann, Marc; Hviid, Stubbe F.; Jorda, Laurent;
Knollenberg, Jörg; Kovacs, Gabor; Kramm, J. -Rainer; Kührt, Ekkehard;
Küppers, Michael; Lara, Luisa M.; Lazzarin, Monica; Lopez Moreno,
Josè J.; Marzari, Francesco; Naletto, Giampiero; Oklay, Nilda; Shi,
Xian; Tubiana, Cecilia; Vincent, Jean-Baptiste
2016MNRAS.462S.533L Altcode:
Because of the diurnal thermal cycle and the irregular shape of the
nucleus, gas outflow of comet 67P/Churyumov-Gerasimenko could be highly
anisotropic as indicated by the colliminated dust jet structures
on the sunlit side. Based on the OSIRIS imaging observations of
the outgassing effect, a simple model of surface sublimation can
be constructed by taking into account the dependence on the solar
insolation. With preliminary information on the time variability of
the global gas production rate, a sequence of gas coma models can be
generated at different epochs before and after perihelion. We also
investigate different patterns of dust particle dynamics under the
influences of nuclear rotation and gas drag. From these considerations,
a consistent picture of the spatial distribution of dusty materials
across the surface of comet 67P as it moves around the perihelion can be
developed. It is found that because of the redeposition of the ejected
dust from the Southern hemisphere to the Northern hemisphere during
the southern summer season the Hapi region could gain up to 0.4 m
while the Wosret region would lose up to 1.8 m of dust mantle per orbit.
---------------------------------------------------------
Title: Comparative study of water ice exposures on cometary nuclei
using multispectral imaging data
Authors: Oklay, N.; Sunshine, J. M.; Pajola, M.; Pommerol, A.;
Vincent, J. -B.; Mottola, S.; Sierks, H.; Fornasier, S.; Barucci,
M. A.; Preusker, F.; Scholten, F.; Lara, L. M.; Barbieri, C.;
Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.;
Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo,
V.; Davidsson, B. J. R.; Debei, S.; De Cecco, M.; Deller, J.; Fulle,
M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hall,
I.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.;
Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.;
Lazzarin, M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Marzari, F.; Naletto,
G.; Shi, X.; Thomas, N.; Tubiana, C.
2016MNRAS.462S.394O Altcode:
Deep Impact, EPOXI and Rosetta missions visited comets 9P/Tempel 1,
103P/Hartley 2 and 67P/Churyumov-Gerasimenko, respectively. Each of
these three missions was equipped with both multispectral imagers and
infrared spectrometers. Bright blue features containing water ice were
detected in each of these comet nuclei. We analysed multispectral
properties of enriched water ice features observed via Optical,
Spectroscopic, and Infrared Remote Imaging System narrow angle camera
on comet 67P in the wavelength range of 260-1000 nm and then compared
with multispectral data of water ice deposits observed on comets 9P and
103P. We characterize the UV/VIS properties of water-ice-rich features
observed on the nuclei of these three comets. When compared to the
average surface of each comet, our analysis shows that the water ice
deposits seen on comet 9P are similar to the clustered water-ice-rich
features seen on comet 67P, while the water ice deposit seen on comet
103P is more akin to two large isolated water-ice-rich features seen
on comet 67P. Our results indicate that the water ice deposit observed
on comet 103P contains more water ice than the water-ice-rich features
observed on comets 9P and 67P, proportionally to the average surface
of each nucleus.
---------------------------------------------------------
Title: Spectrophotometry of the Khonsu region on the comet
67P/Churyumov-Gerasimenko using OSIRIS instrument images
Authors: Deshapriya, J. D. P.; Barucci, M. A.; Fornasier, S.; Feller,
C.; Hasselmann, P. H.; Sierks, H.; El-Maarry, M. R.; Pajola, M.;
Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.;
Agarwal, J.; A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Boudreault,
S.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.;
Deller, J.; De Cecco, M.; Fulle, M.; Gicquel, A.; Groussin, O.;
Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Ip, W.;
Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, R.; Kührt, E.;
Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari,
F.; Mottola, S.; Naletto, G.; Oklay, N.; Perna, D.; Pommerol, A.;
Thomas, N.; Tubiana, C.; Vincent, J. -B.
2016MNRAS.462S.274D Altcode: 2016MNRAS.tmp.1515D
Our work focuses on the spectrophotometric analysis of selected
terrain and bright patches in the Khonsu region on the comet
67P/Churyumov-Gerasimenko. Despite the variety of geological features,
their spectrophotometric properties appear to indicate a similar
composition. It is noticeable that the smooth areas in Khonsu possess
similar spectrophotometric behaviour to some other regions of the
comet. We observed bright patches on Khonsu with an estimation of
>40 per cent of normal albedo and suggest that they are associated
with H<SUB>2</SUB>O ice. One of the studied bright patches has been
observed to exist on the surface for more than 5 months without a major
decay of its size, implying the existence of potential sub-surface icy
layers. Its location may be correlated with a cometary outburst during
the perihelion passage of the comet in 2015 August, and we interpret
it to have triggered the surface modifications necessary to unearth
the stratified icy layers beneath the surface. A boulder analysis
on Khonsu leads to a power-law index of -3.1 +0.2/-0.3 suggesting a
boulder formation, shaped by varying geological processes for different
morphological units.
---------------------------------------------------------
Title: Acceleration of individual, decimetre-sized aggregates in
the lower coma of comet 67P/Churyumov-Gerasimenko
Authors: Agarwal, Jessica; A'Hearn, M. F.; Vincent, J. -B.; Güttler,
C.; Höfner, S.; Sierks, H.; Tubiana, C.; Barbieri, C.; Lamy, P. L.;
Rodrigo, R.; Koschny, D.; Rickman, H.; Barucci, M. A.; Bertaux, J. -L.;
Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson,
B.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.;
Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Hofmann, M.; Hviid,
S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm,
J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez
Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Shi, X.; Thomas, N.
2016MNRAS.462S..78A Altcode: 2016MNRAS.tmp.1292A; 2016arXiv160807933A
We present observations of decimetre-sized, likely ice-containing
aggregates ejected from a confined region on the surface of comet
67P/Churyumov-Gerasimenko. The images were obtained with the narrow
angle camera of the Optical, Spectroscopic, and Infrared Remote
Imaging System on board the Rosetta spacecraft in 2016 January when
the comet was at 2 au from the Sun outbound from perihelion. We
measure the acceleration of individual aggregates through a 2 h image
series. Approximately 50 per cent of the aggregates are accelerated
away from the nucleus, and 50 per cent towards it, and likewise towards
either horizontal direction. The accelerations are up to one order of
magnitude stronger than local gravity, and are most simply explained by
the combined effect of gas drag accelerating all aggregates upwards,
and the recoil force from asymmetric outgassing, either from rotating
aggregates with randomly oriented spin axes and sufficient thermal
inertia to shift the temperature maximum away from an aggregate's
subsolar region, or from aggregates with variable ice content. At
least 10 per cent of the aggregates will escape the gravity field of
the nucleus and feed the comet's debris trail, while others may fall
back to the surface and contribute to the deposits covering parts
of the Northern hemisphere. The rocket force plays a crucial role in
pushing these aggregates back towards the surface. Our observations
show the future back fall material in the process of ejection, and
provide the first direct measurement of the acceleration of aggregates
in the innermost coma (<2 km) of a comet, where gas drag is still
significant.
---------------------------------------------------------
Title: Changes in the Physical Environment of the Inner Coma of
67P/Churyumov-Gerasimenko with Decreasing Heliocentric Distance
Authors: Bodewits, D.; Lara, L. M.; A'Hearn, M. F.; La Forgia, F.;
Gicquel, A.; Kovacs, G.; Knollenberg, J.; Lazzarin, M.; Lin, Z. -Y.;
Shi, X.; Snodgrass, C.; Tubiana, C.; Sierks, H.; Barbieri, C.; Lamy,
P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Barucci,
M. A.; Bertaux, J. -L.; Bertini, I.; Boudreault, S.; Cremonese, G.;
Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier,
S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hviid,
S. F.; Ip, W. -H.; Jorda, L.; Kramm, J. -R.; Kührt, E.; Küppers,
M.; López-Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Thomas,
N.; Toth, I.; Vincent, J. -B.
2016AJ....152..130B Altcode: 2016arXiv160705632B
The Wide Angle Camera of the OSIRIS instrument on board the
Rosetta spacecraft is equipped with several narrow-band filters
that are centered on the emission lines and bands of various
fragment species. These are used to determine the evolution of the
production and spatial distribution of the gas in the inner coma of
comet 67P with time and heliocentric distance, here between 2.6 and
1.3 au pre-perihelion. Our observations indicate that the emission
observed in the OH, O I, CN, NH, and NH<SUB>2</SUB> filters is mostly
produced by dissociative electron impact excitation of different parent
species. We conclude that CO<SUB>2</SUB> rather than H<SUB>2</SUB>O is
a significant source of the [O I] 630 nm emission. A strong plume-like
feature observed in the CN and O I filters is present throughout our
observations. This plume is not present in OH emission and indicates
a local enhancement of the CO<SUB>2</SUB>/H<SUB>2</SUB>O ratio by as
much as a factor of 3. We observed a sudden decrease in intensity levels
after 2015 March, which we attribute to decreased electron temperatures
in the first few kilometers above the surface of the nucleus.
---------------------------------------------------------
Title: Summer fireworks on comet 67P
Authors: Vincent, J. -B.; A'Hearn, M. F.; Lin, Z. -Y.; El-Maarry,
M. R.; Pajola, M.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Barucci, M. A.;
Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese,
G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller,
J.; Fornasier, S.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez,
P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann,
M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs,
G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin,
M.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Mottola, S.;
Naletto, G.; Oklay, N.; Preusker, F.; Scholten, F.; Shi, X.; Thomas,
N.; Toth, I.; Tubiana, C.
2016MNRAS.462S.184V Altcode: 2016arXiv160907743V
During its 2 yr mission around comet 67P/Churyumov-Gerasimenko, ESA's
Rosetta spacecraft had the unique opportunity to follow closely a comet
in the most active part of its orbit. Many studies have presented the
typical features associated with the activity of the nucleus, such as
localized dust and gas jets. Here, we report on series of more energetic
transient events observed during the 3 months surrounding the comet's
perihelion passage in 2015 August. We detected and characterized 34
outbursts with the Rosetta cameras, one every 2.4 nucleus rotations. We
identified three main dust plume morphologies associated with these
events: a narrow jet, a broad fan, and more complex plumes featuring
both previous types together. These plumes are comparable in scale
and temporal variation to what has been observed on other comets. We
present a map of the outbursts' source locations, and discuss the
associated topography. We find that the spatial distribution sources
on the nucleus correlate well with morphological region boundaries,
especially in areas marked by steep scarps or cliffs. Outbursts occur
either in the early morning or shortly after the local noon, indicating
two potential processes: morning outbursts may be triggered by thermal
stresses linked to the rapid change of temperature; afternoon events
are most likely related to the diurnal or seasonal heat wave reaching
volatiles buried under the first surface layer. In addition, we propose
that some events can be the result of a completely different mechanism,
in which most of the dust is released upon the collapse of a cliff.
---------------------------------------------------------
Title: The Agilkia boulders/pebbles size-frequency distributions:
OSIRIS and ROLIS joint observations of 67P surface
Authors: Pajola, M.; Mottola, S.; Hamm, M.; Fulle, M.; Davidsson,
B.; Güttler, C.; Sierks, H.; Naletto, G.; Arnold, G.; Grothues,
H. -G.; Jaumann, R.; Michaelis, H.; Bibring, J. P.; Barbieri,
C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller,
H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. L.;
Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Debei, S.;
De Cecco, M.; Deller, J.; El Maarry, M. R.; Feller, C.; Fornasier,
S.; Gicquel, A.; Groussin, O.; Gutierrez, P. J.; Hofmann, M.; Hviid,
S. F.; Ip, W. H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Kührt,
E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lin, Z. Y.; Lazzarin,
M.; Lopez Moreno, J. J.; Lucchetti, A.; Marzari, F.; Massironi, M.;
Michalik, H.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten, F.;
Thomas, N.; Tubiana, C.; Vincent, J. B.
2016MNRAS.462S.242P Altcode:
By using the images acquired by the OSIRIS (Optical, Spectroscopic
and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging
System) cameras, we derive the size-frequency distribution (SFD) of
cometary pebbles and boulders covering the size range 0.05-30.0 m on
the Agilkia landing site. The global SFD measured on OSIRIS images,
reflects the different properties of the multiple morphological
units present on Agilkia, combined with selection effects related to
lifting, transport and redeposition. Contrarily, the different ROLIS SFD
derived on the smooth and rough units may be related to their different
regolith thickness present on Agilkia. In the thicker, smoother layer,
ROLIS mainly measures the SFD of the airfall population which almost
completely obliterates the signature of underlying boulders up to a
size of the order of 1 m. This is well matched by the power-law index
derived analysing coma particles identified by the grain analyser
Grain Impact Analyser and Dust Accumulator. This result confirms the
important blanketing dynamism of Agilkia. The steeper SFD observed in
rough terrains from 0.4 to 2 m could point out intrinsic differences
between northern and southern dust size distributions, or it may
suggest that the underlying boulders 'peek through' the thinner airfall
layer in the rough terrain, thereby producing the observed excess
in the decimetre size range. Eventually, the OSIRIS SFD performed on
the Philae landing unit may be due to water sublimation from a static
population of boulders, affecting smaller boulders before the bigger
ones, thus shallowing the original SFD.
---------------------------------------------------------
Title: Decimetre-scaled spectrophotometric properties of the nucleus
of comet 67P/Churyumov-Gerasimenko from OSIRIS observations
Authors: Feller, C.; Fornasier, S.; Hasselmann, P. H.; Barucci, A.;
Preusker, F.; Scholten, F.; Jorda, L.; Pommerol, A.; Jost, B.; Poch,
O.; ElMaary, M. R.; Thomas, N.; Belskaya, I.; Pajola, M.; Sierks,
H.; Barbieri, C.; Lamy, P. L.; Koschny, D.; Rickman, H.; Rodrigo, R.;
Agarwal, J.; A'Hearn, M.; Bertaux, J. -L.; Bertini, I.; Boudreault,
S.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; De
Cecco, M.; Deller, J.; Fulle, M.; Giquel, A.; Groussin, O.; Gutierrez,
P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Keller, H.; Ip, W. -H.;
Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.;
Lara, M. L.; Lazzarin, M.; Leyrat, C.; Lopez Moreno, J. J.; Marzari,
F.; Masoumzadeh, N.; Mottola, S.; Naletto, G.; Perna, D.; Oklay, N.;
Shi, X.; Tubiana, C.; Vincent, J. -B.
2016MNRAS.462S.287F Altcode: 2016arXiv161100012F
We present the results of the photometric and spectrophotometric
properties of the 67P/Churyumov-Gerasimenko nucleus derived with the
Optical, Spectroscopic and Infrared Remote Imaging System instrument
during the closest fly-by over the comet, which took place on 2015
February 14 at a distance of ∼6 km from the surface. Several images
covering the 0°-33° phase angle range were acquired, and the spatial
resolution achieved was 11 cm pixel<SUP>-1</SUP>. The flown-by region
is located on the big lobe of the comet, near the borders of the Ash,
Apis and Imhotep regions. Our analysis shows that this region features
local heterogeneities at the decimetre scale. We observed difference
of reflectance up to 40 per cent between bright spots and sombre
regions, and spectral slope variations up to 50 per cent. The spectral
reddening effect observed globally on the comet surface by Fornasier
et al. (2015) is also observed locally on this region, but with a
less steep behaviour. We note that numerous metre-sized boulders,
which exhibit a smaller opposition effect, also appear spectrally
redder than their surroundings. In this region, we found no evidence
linking observed bright spots to exposed water-ice-rich material. We
fitted our data set using the Hapke 2008 photometric model. The region
overflown is globally as dark as the whole nucleus (geometric albedo of
6.8 per cent) and it has a high porosity value in the uppermost layers
(86 per cent). These results of the photometric analysis at a decimetre
scale indicate that the photometric properties of the flown-by region
are similar to those previously found for the whole nucleus.
---------------------------------------------------------
Title: Geologic mapping of the Comet 67P/Churyumov-Gerasimenko's
Northern hemisphere
Authors: Giacomini, L.; Massironi, M.; El-Maarry, M. R.; Penasa,
L.; Pajola, M.; Thomas, N.; Lowry, S. C.; Barbieri, C.; Cremonese,
G.; Ferri, F.; Naletto, G.; Bertini, I.; La Forgia, F.; Lazzarin,
M.; Marzari, F.; Sierks, H.; Lamy, P. L.; Rodrigo, R.; Rickman,
H.; Koschny, D.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Auger,
A. -T.; Barucci, M. A.; Bertaux, J. -L.; Besse, S.; Bodewits, D.;
Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Fornasier, S.;
Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hviid, S. F.;
Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.;
Kührt, E.; Küppers, M.; Lara, L. M.; Moreno, J. J. Lopez; Magrin,
S.; Michalik, H.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten,
F.; Tubiana, C.; Vincent, J. -B.
2016MNRAS.462S.352G Altcode:
The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS),
the scientific imaging system onboard the Rosetta mission, has been
acquiring images of the nucleus of the comet 67P/Churyumov-Gerasimenko
since 2014 August with a resolution which allows a detailed analysis
of its surface. Indeed, data reveal a complex surface morphology
which is likely the expression of different processes which occurred
at different times on the cometary nucleus. In order to characterize
these different morphologies and better understand their distribution,
we performed a geologic mapping of comet's 67P Northern hemisphere in
which features have been distinguished based on their morphological,
textural and stratigraphic characteristics. For this purpose, we used
narrow-angle camera images acquired in 2014 August and September with
a spatial scale ranging from 1.2 to 2.4 m pixel<SUP>-1</SUP>. Several
different geologic units have been identified on the basis of their
different surface textures, granulometry and morphology. Some of these
units are distinctive and localized, whereas others are more common
and distributed all over the Northern hemisphere. Moreover, different
types of linear features have been distinguished on the basis of their
morphology. Some of these lineaments have never been observed before
on a comet and can offer important clues on the internal structures
of the nucleus itself. The geologic mapping results presented here
will allow us to better understand the processes which affected the
nucleus' surface and thus the origin and evolutionary history of comet
67P/Churyumov-Gerasimenko.
---------------------------------------------------------
Title: The 2016 Feb 19 outburst of comet 67P/CG: an ESA Rosetta
multi-instrument study
Authors: Grün, E.; Agarwal, J.; Altobelli, N.; Altwegg, K.;
Bentley, M. S.; Biver, N.; Della Corte, V.; Edberg, N.; Feldman,
P. D.; Galand, M.; Geiger, B.; Götz, C.; Grieger, B.; Güttler, C.;
Henri, P.; Hofstadter, M.; Horanyi, M.; Jehin, E.; Krüger, H.; Lee,
S.; Mannel, T.; Morales, E.; Mousis, O.; Müller, M.; Opitom, C.;
Rotundi, A.; Schmied, R.; Schmidt, F.; Sierks, H.; Snodgrass, C.;
Soja, R. H.; Sommer, M.; Srama, R.; Tzou, C. -Y.; Vincent, J. -B.;
Yanamandra-Fisher, P.; A'Hearn, M. F.; Erikson, A. I.; Barbieri, C.;
Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Burch, J.; Colangeli,
L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco,
M.; Deller, J.; Feaga, L. M.; Ferrari, M.; Fornasier, S.; Fulle,
M.; Gicquel, A.; Gillon, M.; Green, S. F.; Groussin, O.; Gutiérrez,
P. J.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Ivanovski, S.; Jorda,
L.; Keller, H. U.; Knight, M. M.; Knollenberg, J.; Koschny, D.; Kramm,
J. -R.; Kührt, E.; Küppers, M.; Lamy, P. L.; Lara, L. M.; Lazzarin,
M.; Lòpez-Moreno, J. J.; Manfroid, J.; Epifani, E. Mazzotta; Marzari,
F.; Naletto, G.; Oklay, N.; Palumbo, P.; Parker, J. Wm.; Rickman,
H.; Rodrigo, R.; Rodrìguez, J.; Schindhelm, R.; Shi, X.; Sordini,
R.; Steffl, A. J.; Stern, S. A.; Thomas, N.; Tubiana, C.; Weaver,
H. A.; Weissman, P.; Zakharov, V. V.; Taylor, M. G. G. T.
2016MNRAS.462S.220G Altcode: 2016MNRAS.tmp.1212G
On 2016 Feb 19, nine Rosetta instruments serendipitously
observed an outburst of gas and dust from the nucleus of comet
67P/Churyumov-Gerasimenko. Among these instruments were cameras and
spectrometers ranging from UV over visible to microwave wavelengths,
in situ gas, dust and plasma instruments, and one dust collector. At
09:40 a dust cloud developed at the edge of an image in the shadowed
region of the nucleus. Over the next two hours the instruments
recorded a signature of the outburst that significantly exceeded the
background. The enhancement ranged from 50 per cent of the neutral gas
density at Rosetta to factors >100 of the brightness of the coma
near the nucleus. Dust related phenomena (dust counts or brightness
due to illuminated dust) showed the strongest enhancements (factors
>10). However, even the electron density at Rosetta increased by
a factor 3 and consequently the spacecraft potential changed from
∼-16 V to -20 V during the outburst. A clear sequence of events
was observed at the distance of Rosetta (34 km from the nucleus):
within 15 min the Star Tracker camera detected fast particles (∼25
m s<SUP>-1</SUP>) while 100 μm radius particles were detected by the
GIADA dust instrument ∼1 h later at a speed of 6 m s<SUP>-1</SUP>. The
slowest were individual mm to cm sized grains observed by the OSIRIS
cameras. Although the outburst originated just outside the FOV of the
instruments, the source region and the magnitude of the outburst could
be determined.
---------------------------------------------------------
Title: Detection of exposed H<SUB>2</SUB>O ice on the nucleus of
comet 67P/Churyumov-Gerasimenko. as observed by Rosetta OSIRIS and
VIRTIS instruments
Authors: Barucci, M. A.; Filacchione, G.; Fornasier, S.; Raponi, A.;
Deshapriya, J. D. P.; Tosi, F.; Feller, C.; Ciarniello, M.; Sierks,
H.; Capaccioni, F.; Pommerol, A.; Massironi, M.; Oklay, N.; Merlin,
F.; Vincent, J. -B.; Fulchignoni, M.; Guilbert-Lepoutre, A.; Perna,
D.; Capria, M. T.; Hasselmann, P. H.; Rousseau, B.; Barbieri, C.;
Bockelée-Morvan, D.; Lamy, P. L.; De Sanctis, C.; Rodrigo, R.; Erard,
S.; Koschny, D.; Leyrat, C.; Rickman, H.; Drossart, P.; Keller, H. U.;
A'Hearn, M. F.; Arnold, G.; Bertaux, J. -L.; Bertini, I.; Cerroni, P.;
Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; El-Maarry, M. R.;
Fonti, S.; Fulle, M.; Groussin, O.; Güttler, C.; Hviid, S. F.; Ip,
W.; Jorda, L.; Kappel, D.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.;
Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Mancarella,
F.; Marzari, F.; Mottola, S.; Naletto, G.; Pajola, M.; Palomba, E.;
Quirico, E.; Schmitt, B.; Thomas, N.; Tubiana, C.
2016A&A...595A.102B Altcode: 2016arXiv160900551B
Context. Since the orbital insertion of the Rosetta spacecraft,
comet 67P/Churyumov-Gerasimenko (67P) has been mapped by OSIRIS
camera and VIRTIS spectro-imager, producing a huge quantity of images
and spectra of the comet's nucleus. <BR /> Aims: The aim of this
work is to search for the presence of H<SUB>2</SUB>O on the nucleus
which, in general, appears very dark and rich in dehydrated organic
material. After selecting images of the bright spots which could be good
candidates to search for H<SUB>2</SUB>O ice, taken at high resolution
by OSIRIS, we check for spectral cubes of the selected coordinates to
identify these spots observed by VIRTIS. <BR /> Methods: The selected
OSIRIS images were processed with the OSIRIS standard pipeline and
corrected for the illumination conditions for each pixel using the
Lommel-Seeliger disk law. The spots with higher I/F were selected and
then analysed spectrophotometrically and compared with the surrounding
area. We selected 13 spots as good targets to be analysed by VIRTIS
to search for the 2 μm absorption band of water ice in the VIRTIS
spectral cubes. <BR /> Results: Out of the 13 selected bright spots,
eight of them present positive H<SUB>2</SUB>O ice detection on the
VIRTIS data. A spectral analysis was performed and the approximate
temperature of each spot was computed. The H<SUB>2</SUB>O ice content
was confirmed by modeling the spectra with mixing (areal and intimate)
of H<SUB>2</SUB>O ice and dark terrain, using Hapke's radiative transfer
modeling. We also present a detailed analysis of the detected spots.
---------------------------------------------------------
Title: Geomorphological mapping of comet 67P/Churyumov-Gerasimenko's
Southern hemisphere
Authors: Lee, Jui-Chi; Massironi, Matteo; Ip, Wing-Huen; Giacomini,
Lorenza; Ferrari, Sabrina; Penasa, Luca; El-Maarry, Mohamed Ramy;
Pajola, Maurizio; Lai, Ian-Lin; Lin, Zhong-Yi; Ferri, Francesca;
Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael;
Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica;
A'Hearn, Michael F.; Barucci, Maria Antonella; Bertaux, Jean-Loup;
Bertini, Ivano; Cremonese, Gabriele; Da Deppo, Vania; Davidsson,
Björn; Debei, Stefano; De Cecco, Mariolino; Deller, Jakob; Fornasier,
Sonia; Fulle, Marco; Groussin, Olivier; Gutiérrez, Pedro J.; Güttler,
Carsten; Hofmann, Marc; Hviid, Stubbe F.; Jorda, Laurent; Knollenberg,
Jörg; Kovacs, Gabor; Kramm, J. -Rainer; Kührt, Ekkehard; Küppers,
Michael; Lara, Luisa M.; Lazzarin, Monica; Marzari, Francesco; Lopez
Moreno, Josè J.; Naletto, Giampiero; Oklay, Nilda; Shi, Xian; Thomas,
Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste
2016MNRAS.462S.573L Altcode:
In 2015 May, the Southern hemisphere of comet 67P/Churyumov-Gerasimenko
became visible by the OSIRIS cameras on-board the Rosetta
spacecraft. The resolution was high enough to carry out a detailed
analysis of the surface morphology, which is quite different from the
Northern hemisphere. Previous works show that fine particle deposits
are the most extensive geological unit in the Northern hemisphere. In
contrast, the Southern hemisphere is dominated by outcropping
consolidated terrain. In this work, we provide geomorphological maps
of the Southern hemisphere with the distinction of both geological
units and linear features. The geomorphological maps described in this
study allow us to gain a better understanding of the processes shaping
the comet nucleus and the distribution of primary structures such as
fractures and strata.
---------------------------------------------------------
Title: Sublimation of icy aggregates in the coma of comet
67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on
board Rosetta
Authors: Gicquel, A.; Vincent, J. -B.; Agarwal, J.; A'Hearn, M. F.;
Bertini, I.; Bodewits, D.; Sierks, H.; Lin, Z. -Y.; Barbieri, C.;
Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.;
Barucci, M. A.; Bertaux, J. -L.; Besse, S.; Cremonese, G.; Da Deppo,
V.; Davidsson, B.; Debei, S.; Deller, J.; De Cecco, M.; Frattin, E.;
El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez,
P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann,
M.; Hu, X.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.;
Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.;
Lazzarin, M.; Moreno, J. J. Lopez; Lowry, S.; Marzari, F.; Masoumzadeh,
N.; Massironi, M.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.;
Pajola, M.; Pommerol, A.; Preusker, F.; Scholten, F.; Shi, X.; Thomas,
N.; Toth, I.; Tubiana, C.
2016MNRAS.462S..57G Altcode: 2016arXiv160808774G; 2016MNRAS.tmp.1233G
Beginning in 2014 March, the OSIRIS (Optical, Spectroscopic, and
Infrared Remote Imaging System) cameras began capturing images of the
nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko
using both the wide angle camera (WAC) and the narrow angle camera
(NAC). The many observations taken since July of 2014 have been used to
study the morphology, location, and temporal variation of the comet's
dust jets. We analysed the dust monitoring observations shortly after
the southern vernal equinox on 2015 May 30 and 31 with the WAC at the
heliocentric distance R<SUB>h</SUB> = 1.53 AU, where it is possible
to observe that the jet rotates with the nucleus. We found that the
decline of brightness as a function of the distance of the jet is
much steeper than the background coma, which is a first indication of
sublimation. We adapted a model of sublimation of icy aggregates and
studied the effect as a function of the physical properties of the
aggregates (composition and size). The major finding of this paper
was that through the sublimation of the aggregates of dirty grains
(radius a between 5 and 50 μm) we were able to completely reproduce
the radial brightness profile of a jet beyond 4 km from the nucleus. To
reproduce the data, we needed to inject a number of aggregates between
8.5 × 10<SUP>13</SUP> and 8.5 × 10<SUP>10</SUP> for a = 5 and 50 μm,
respectively, or an initial mass of H<SUB>2</SUB>O ice around 22 kg.
---------------------------------------------------------
Title: 67P/C-G inner coma dust properties from 2.2 au inbound to
2.0 au outbound to the Sun
Authors: Della Corte, V.; Rotundi, A.; Fulle, M.; Ivanovski, S.; Green,
S. F.; Rietmeijer, F. J. M.; Colangeli, L.; Palumbo, P.; Sordini, R.;
Ferrari, M.; Accolla, M.; Zakharov, V.; Mazzotta Epifani, E.; Weissman,
P.; Gruen, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Bussoletti, E.;
Crifo, J. F.; Esposito, F.; Lamy, P. L.; McDonnell, J. A. M.; Mennella,
V.; Molina, A.; Morales, R.; Moreno, F.; Palomba, E.; Perrin, J. M.;
Rodrigo, R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.;
Ortiz, J. L.; Jeronimo, J. M.; Leese, M. R.; Herranz, M.; Liuzzi,
V.; Lopez-Jimenez, A. C.
2016MNRAS.462S.210D Altcode: 2016MNRAS.tmp.1514D
GIADA (Grain Impact Analyzer and Dust Accumulator) on-board the
Rosetta space probe is designed to measure the momentum, mass and
speed of individual dust particles escaping the nucleus of comet
67P/Churyumov-Gerasimenko (hereafter 67P). From 2014 August to
2016 June, Rosetta escorted comet 67P during its journey around
the Sun. Here, we focus on GIADA data taken between 2015 January
and 2016 February which included 67P's perihelion passage. To better
understand cometary activity and more specifically the presence of dust
structures in cometary comae, we mapped the spatial distribution of dust
density in 67P's coma. In this manner, we could track the evolution of
high-density regions of coma dust and their connections with nucleus
illumination conditions, namely tracking 67P's seasons. We also studied
the link between dust particle speeds and their masses with respect to
heliocentric distance, I.e. the level of cometary activity. This allowed
us to derive a global and a local correlation of the dust particles'
speed distribution with respect to the H<SUB>2</SUB>O production rate.
---------------------------------------------------------
Title: Modelling of the outburst on July 29<SUP>th</SUP> ,
2015 observed with OSIRIS in the southern hemisphere of comet
67P/Churyumov-Gerasimenko
Authors: Gicquel, Adeline; Vincent, Jean-Baptiste; Sierks, Holger;
Rose, Martin; Agarwal, Jessica; Deller, Jakob; Guettler, Carsten;
Hoefner, Sebastian; Hofmann, Marc; Hu, Xuanyu; Kovacs, Gabor; Oklay
Vincent, Nilda; Shi, Xian; Tubiana, Cecilia; Barbieri, Cesare; Lamy,
Phylippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; OSIRIS Team
2016DPS....4811614G Altcode:
Images of the nucleus and the coma (gas and dust) of comet
67P/Churyumov- Gerasimenko have been acquired by the OSIRIS (Optical,
Spectroscopic, and Infrared Remote Imaging System) cameras system since
March 2014 using both the wide angle camera (WAC) and the narrow angle
camera (NAC). We are using the NAC camera to study the bright outburst
observed on July 29<SUP>th</SUP>, 2015 in the southern hemisphere. The
NAC camera's wavelength ranges between 250-1000 nm with a combination
of 12 filters. The high spatial resolution is needed to localize the
source point of the outburst on the surface of the nucleus. At the
time of the observations, the heliocentric distance was 1.25AU and the
distance between the spacecraft and the comet was 126 km. We aim to
understand the physics leading to such outgassing: Is the jet associated
to the outbursts controlled by the micro-topography? Or by ice suddenly
exposed? We are using the Direct Simulation Monte Carlo (DSMC) method
to study the gas flow close to the nucleus. The goal of the DSMC code is
to reproduce the opening angle of the jet, and constrain the outgassing
ratio between outburst source and local region. The results of this
model will be compared to the images obtained with the NAC camera.
---------------------------------------------------------
Title: Comet 67P as seen by Rosetta/OSIRIS
Authors: Guettler, Carsten; Sierks, Holger; Barbieri, Cesare;
Lamy, Philippe L.; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans;
OSIRIS Team
2016DPS....4820102G Altcode:
In September 2016, the ESA Rosetta mission will come to its
ending. Having escorted comet 67P for more than two years, the
scientific camera system OSIRIS onboard Rosetta witnessed all important
milestones of the mission: after the first characterization and the
Philae landing we saw the comet's activity increasing while it was
approaching the Sun. During the peak of activity around perihel in
August 2015, the spacecraft had to retreat to a safe distance but
we witnessed strong but predictable jet activity and, at the same
time, short lived eruptions, some of these being big outbursts. When
the activity declined post perihelion and allowed the spacecraft
to go back closer, comparison with the early characterization
revealed numerous morphologic changes on the surface, which can
be attributed to the strong activity during perihelion passage.The
paper will give an overview of latest OSIRIS science and discoveries
including the morphology, activity, and surface changes mentioned
above. Implications on the nature of the comet and its mechanisms
will be drawn from these. The current plan for the mission is to go to
very close distances in August and September 2016 and finally land the
spacecraft on 67P.Acknowledgements: OSIRIS was built by a consortium
led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen,
Germany, in collaboration with CISAS, University of Padova, Italy,
the Laboratoire d'Astrophysique de Marseille, France, the Instituto
de Astrofísica de Andalucia, CSIC, Granada, Spain, the Scientific
Support Office of the European Space Agency, Noordwijk, The Netherlands,
the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain, the
Universidad Politéchnica de Madrid, Spain, the Department of Physics
and Astronomy of Uppsala University, Sweden, and the Institut für
Datentechnik und Kommunikationsnetze der Technischen Universität
Braunschweig, Germany.We thank the Rosetta Science Ground Segment at
ESAC, the Rosetta Mission Operations Centre at ESOC and the Rosetta
Project at ESTEC for their outstanding work enabling the science return
of the Rosetta Mission.
---------------------------------------------------------
Title: The global shape, density and rotation of Comet
67P/Churyumov-Gerasimenko from preperihelion Rosetta/OSIRIS
observations
Authors: Jorda, L.; Gaskell, R.; Capanna, C.; Hviid, S.; Lamy, P.;
Ďurech, J.; Faury, G.; Groussin, O.; Gutiérrez, P.; Jackman, C.;
Keihm, S. J.; Keller, H. U.; Knollenberg, J.; Kührt, E.; Marchi, S.;
Mottola, S.; Palmer, E.; Schloerb, F. P.; Sierks, H.; Vincent, J. -B.;
A'Hearn, M. F.; Barbieri, C.; Rodrigo, R.; Koschny, D.; Rickman, H.;
Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; Da Deppo,
V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.;
Güttler, C.; Ip, W. -H.; Kramm, J. R.; Küppers, M.; Lara, L. M.;
Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay,
N.; Thomas, N.; Tubiana, C.; Wenzel, K. -P.
2016Icar..277..257J Altcode:
The Rosetta spacecraft reached Comet 67P/Churyumov-Gerasimenko
(hereafter 67P/C-G) in August 2014 at an heliocentric distance of 3.6
a.u. and was then put in orbit around its nucleus to perform detailed
observations. Among the collected data are the images acquired by
the OSIRIS instrument up to the perihelion passage of the comet in
August 2015, which allowed us to map the entire nucleus surface at
high-resolution in the visible. Stereophotoclinometry methods have been
used to reconstruct a global high-resolution shape model and to monitor
its rotational parameters using data collected up to perihelion. <P
/>The nucleus has a conspicuous bilobate shape with overall dimensions
along its principal axes of (4.34 ± 0.02) × (2.60 ± 0.02) × (2.12
± 0.06) km. The best-fit ellipsoid dimensions of the individual lobes
along their principal axes of inertia are found to be 4.10 × 3.52 ×
1.63 km and 2.50 × 2.14 × 1.64 km. Their volume amounts to 66% and
27% of the total volume of the nucleus. The two lobes are connected
by a "neck" whose volume has been estimated to represent ∼7% of the
total volume of the comet. Combining the derived volume of 18.8 ±
0.3 km<SUP>3</SUP> with the mass of 9.982 ± 0.003 × 10<SUP>12</SUP>
kg determined by the Rosetta/RSI experiment, we obtained a bulk
density of the nucleus of 532 ± 7 kg m<SUP>-3</SUP> . Together with
the companion value of 535 ± 35 kg m<SUP>-3</SUP> deduced from the
stereophotogrammetry shape model of the nucleus (Preusker et al. [2015]
Astron. Astrophys. 583, A33), these constitute the first reliable and
most accurate determination of the density of a cometary nucleus to
date. The calculated porosity is quite large, ranging approximately
from 70% to 75% depending upon the assumed density of the dust
grains and the dust-to-ice mass ratio. The nature of the porosity,
either micro or macro or both, remains unconstrained. The coordinates
of the center of gravity are not compatible with a uniform nucleus
density. The direction of the offset between the center of gravity and
the center of figure suggests that the big lobe has a slightly higher
bulk density compared to the small one. the center of mass position
cannot be explained by different, but homogenous densities in the two
lobes. <P />The initial rotational period of 12.4041 ± 0.0001 h of
the nucleus persisted until October 2014. It then slightly increased
to a maximum of 12.4304 h reached on 19 May 2015 and finally dropped
to 12.305 h just before perihelion on August 10, 2015. A periodogram
analysis of the (RA, Dec) direction of the Z-axis of the comet obtained
in parallel with the shape reconstruction exhibits a highly significant
minima at 11.5 ± 0.5 day clearly indicating an excited rotational
state with an amplitude of 0.15 ± 0.03°.
---------------------------------------------------------
Title: Reconstruction of the Abydos ROSETTA/Philae landing site at
very high spatial resolution
Authors: Capanna, Claire; Jorda, Laurent; Lamy, Philippe L.; Gaskell,
Robert W.; FAURY, Guillaume; DELMAS, Cédric; DURAND, Joelle; GAUDON,
Philippe; GARMIER, Romain; JURADO, Eric; OSIRIS Team
2016DPS....4811006C Altcode:
The Rosetta/Philae module landed in a very uneven area called
Abydos. The landing site has beenidentified on images of this region
acquired by the OSIRIS imaging system aboard the orbiterbefore
(Oct. 2014) and after (Dec. 2014) the landing (Lamy et al., in
prep.).Abydos exhibits a complex topography including numerous cliffs,
several overhangs and lots ofboulders (Lucchetti et al. A&A 585,
L1, 2016). This makes its reconstruction a challenging taskfor 3D
reconstruction techniques.We use a very carefully selected set of
high-resolution OSIRIS images acquired betweenMarch 2016 and August 2016
to reconstruct the detailed topography of the Abydos neighborhoodusing a
method called “multiresolution photoclinometry by deformation” (MPCD,
Capanna et al.,The Visual Computer, 29(6-8): 825-835, 2013). We also
check the compatibility of the local DTMcomparing the panoramic images
obtained by the CIVA-P instrument aboard PHILAE with syntheticimages
created with the DTM, and we compute the distances, incidence and
emission angles duringthe acquisition of these images.
---------------------------------------------------------
Title: Time-dependent tomographic reconstruction of the solar corona
Authors: Vibert, D.; Peillon, C.; Lamy, P.; Frazin, R. A.; Wojak, J.
2016A&C....17..144V Altcode: 2016arXiv160706308V
Solar rotational tomography (SRT) applied to white-light coronal
images observed at multiple aspect angles has been the preferred
approach for determining the three-dimensional (3D) electron density
structure of the solar corona. However, it is seriously hampered by
the restrictive assumption that the corona is time-invariant which
introduces significant errors in the reconstruction. We first explore
several methods to mitigate the temporal variation of the corona by
decoupling the "fast-varying" inner corona from the "slow-moving" outer
corona using multiple masking (either by juxtaposition or recursive
combination) and radial weighting. Weighting with a radial exponential
profile provides some improvement over a classical reconstruction but
only beyond ≈ 3R<SUB>⊙</SUB>. We next consider a full time-dependent
tomographic reconstruction involving spatio-temporal regularization
and further introduce a co-rotating regularization aimed at preventing
concentration of reconstructed density in the plane of the sky. Crucial
to testing our procedure and properly tuning the regularization
parameters is the introduction of a time-dependent MHD model of
the corona based on observed magnetograms to build a time-series of
synthetic images of the corona. Our procedure, which successfully
reproduces the time-varying model corona, is finally applied to a set
of 53 LASCO-C2 pB images roughly evenly spaced in time from 15 to 29
March 2009. Our procedure paves the way to a time-dependent tomographic
reconstruction of the coronal electron density to the whole set of
LASCO-C2 images presently spanning 20 years.
---------------------------------------------------------
Title: Regional surface morphology of comet 67P/Churyumov-Gerasimenko
from Rosetta/OSIRIS images: The southern hemisphere
Authors: El-Maarry, M. R.; Thomas, N.; Gracia-Berná, A.; Pajola,
M.; Lee, J. -C.; Massironi, M.; Davidsson, B.; Marchi, S.; Keller,
H. U.; Hviid, S. F.; Besse, S.; Sierks, H.; Barbieri, C.; Lamy,
P. L.; Koschny, D.; Rickman, H.; Rodrigo, R.; A'Hearn, M. F.; Auger,
A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.;
Cremonese, G.; Da Deppo, V.; De Cecco, M.; Debei, S.; Güttler, C.;
Fornasier, S.; Fulle, M.; Giacomini, L.; Groussin, O.; Gutierrez,
P. J.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm,
J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez
Moreno, J. J.; Marschall, R.; Marzari, F.; Naletto, G.; Oklay, N.;
Pommerol, A.; Preusker, F.; Scholten, F.; Tubiana, C.; Vincent, J. -B.
2016A&A...593A.110E Altcode:
<BR /> Aims: The OSIRIS camera on board the Rosetta spacecraft has
been acquiring images of the comet 67P/Churyumov-Gerasimenko (67P)'s
nucleus since August 2014. Starting in May 2015, the southern hemisphere
gradually became illuminated and was imaged for the first time. Here
we present the regional morphology of the southern hemisphere,
which serves as a companion to an earlier paper that presented the
regional morphology of the northern hemisphere. <BR /> Methods: We used
OSIRIS images that were acquired at orbits ~45-125 km from the center
of the comet (corresponding to spatial resolutions of ~0.8 to 2.3
m/pixel) coupled with the use of digital terrain models to define the
different regions on the surface, and identify structural boundaries
accurately. <BR /> Results: Seven regions have been defined in the
southern hemisphere bringing the total number of defined regions on the
surface of the nucleus to 26. These classifications are mainly based on
morphological and/or topographic boundaries. The southern hemisphere
shows a remarkable dichotomy with its northern counterpart mainly
because of the absence of wide-scale smooth terrains, dust coatings and
large unambiguous depressions. As a result, the southern hemisphere
closely resembles previously identified consolidated regions. An
assessment of the overall morphology of comet 67P suggests that the
comet's two lobes show surface heterogeneities manifested in different
physical/mechanical characteristics, possibly extending to local (I.e.,
within a single region) scales.
---------------------------------------------------------
Title: A small mission concept to the Sun-Earth Lagrangian L5 point
for innovative solar, heliospheric and space weather science
Authors: Lavraud, B.; Liu, Y.; Segura, K.; He, J.; Qin, G.; Temmer,
M.; Vial, J. -C.; Xiong, M.; Davies, J. A.; Rouillard, A. P.; Pinto,
R.; Auchère, F.; Harrison, R. A.; Eyles, C.; Gan, W.; Lamy, P.;
Xia, L.; Eastwood, J. P.; Kong, L.; Wang, J.; Wimmer-Schweingruber,
R. F.; Zhang, S.; Zong, Q.; Soucek, J.; An, J.; Prech, L.; Zhang,
A.; Rochus, P.; Bothmer, V.; Janvier, M.; Maksimovic, M.; Escoubet,
C. P.; Kilpua, E. K. J.; Tappin, J.; Vainio, R.; Poedts, S.; Dunlop,
M. W.; Savani, N.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard, T.;
DeForest, C.; Webb, D.; Lugaz, N.; Fuselier, S. A.; Dalmasse, K.;
Tallineau, J.; Vranken, D.; Fernández, J. G.
2016JASTP.146..171L Altcode:
We present a concept for a small mission to the Sun-Earth Lagrangian L5
point for innovative solar, heliospheric and space weather science. The
proposed INvestigation of Solar-Terrestrial Activity aNd Transients
(INSTANT) mission is designed to identify how solar coronal magnetic
fields drive eruptions, mass transport and particle acceleration that
impact the Earth and the heliosphere. INSTANT is the first mission
designed to (1) obtain measurements of coronal magnetic fields from
space and (2) determine coronal mass ejection (CME) kinematics with
unparalleled accuracy. Thanks to innovative instrumentation at a vantage
point that provides the most suitable perspective view of the Sun-Earth
system, INSTANT would uniquely track the whole chain of fundamental
processes driving space weather at Earth. We present the science
requirements, payload and mission profile that fulfill ambitious science
objectives within small mission programmatic boundary conditions.
---------------------------------------------------------
Title: The primordial nucleus of comet 67P/Churyumov-Gerasimenko
Authors: Davidsson, B. J. R.; Sierks, H.; Güttler, C.; Marzari, F.;
Pajola, M.; Rickman, H.; A'Hearn, M. F.; Auger, A. -T.; El-Maarry,
M. R.; Fornasier, S.; Gutiérrez, P. J.; Keller, H. U.; Massironi, M.;
Snodgrass, C.; Vincent, J. -B.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese,
G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Feller, C.; Fulle, M.;
Groussin, O.; Hviid, S. F.; Höfner, S.; Ip, W. -H.; Jorda, L.;
Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers,
M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.;
Moissl-Fraund, R.; Mottola, S.; Naletto, G.; Oklay, N.; Thomas, N.;
Tubiana, C.
2016A&A...592A..63D Altcode:
Context. We investigate the formation and evolution of comet nuclei
and other trans-Neptunian objects (TNOs) in the solar nebula and
primordial disk prior to the giant planet orbit instability foreseen
by the Nice model. <BR /> Aims: Our goal is to determine whether most
observed comet nuclei are primordial rubble-pile survivors that formed
in the solar nebula and young primordial disk or collisional rubble
piles formed later in the aftermath of catastrophic disruptions of
larger parent bodies. We also propose a concurrent comet and TNO
formation scenario that is consistent with observations. <BR />
Methods: We used observations of comet 67P/Churyumov-Gerasimenko by
the ESA Rosetta spacecraft, particularly by the OSIRIS camera system,
combined with data from the NASA Stardust sample-return mission to comet
81P/Wild 2 and from meteoritics; we also used existing observations
from ground or from spacecraft of irregular satellites of the giant
planets, Centaurs, and TNOs. We performed modeling of thermophysics,
hydrostatics, orbit evolution, and collision physics. <BR /> Results:
We find that thermal processing due to short-lived radionuclides,
combined with collisional processing during accretion in the primordial
disk, creates a population of medium-sized bodies that are comparably
dense, compacted, strong, heavily depleted in supervolatiles like CO
and CO<SUB>2</SUB>; they contain little to no amorphous water ice,
and have experienced extensive metasomatism and aqueous alteration due
to liquid water. Irregular satellites Phoebe and Himalia are potential
representatives of this population. Collisional rubble piles inherit
these properties from their parents. Contrarily, comet nuclei have low
density, high porosity, weak strength, are rich in supervolatiles, may
contain amorphous water ice, and do not display convincing evidence of
in situ metasomatism or aqueous alteration. We outline a comet formation
scenario that starts in the solar nebula and ends in the primordial
disk, that reproduces these observed properties, and additionally
explains the presence of extensive layering on 67P/Churyumov-Gerasimenko
(and on 9P/Tempel 1 observed by Deep Impact), its bi-lobed shape,
the extremely slow growth of comet nuclei as evidenced by recent
radiometric dating, and the low collision probability that allows
primordial nuclei to survive the age of the solar system. <BR />
Conclusions: We conclude that observed comet nuclei are primordial
rubble piles, and not collisional rubble piles. We argue that TNOs
formed as a result of streaming instabilities at sizes below ~400 km
and that ~350 of these grew slowly in a low-mass primordial disk to
the size of Triton, Pluto, and Eris, causing little viscous stirring
during growth. We thus propose a dynamically cold primordial disk,
which prevented medium-sized TNOs from breaking into collisional rubble
piles and allowed the survival of primordial rubble-pile comets. We
argue that comets formed by hierarchical agglomeration out of material
that remained after TNO formation, and that this slow growth was a
necessity to avoid thermal processing by short-lived radionuclides
that would lead to loss of supervolatiles, and that allowed comet
nuclei to incorporate ~3 Myr old material from the inner solar system.
---------------------------------------------------------
Title: The southern hemisphere of 67P/Churyumov-Gerasimenko: Analysis
of the preperihelion size-frequency distribution of boulders ≥7 m
Authors: Pajola, Maurizio; Lucchetti, Alice; Vincent, Jean-Baptiste;
Oklay, Nilda; El-Maarry, Mohamed R.; Bertini, Ivano; Naletto,
Giampiero; Lazzarin, Monica; Massironi, Matteo; Sierks, Holger;
Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef;
Rickman, Hans; Keller, Horst U.; Agarwal, Jessica; A'Hearn, Michael F.;
Barucci, Maria A.; Bertaux, Jean-Loup; Boudreault, Steve; Cremonese,
Gabriele; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De
Cecco, Mariolino; Deller, Jakob; Fornasier, Sonia; Fulle, Marco;
Gicquel, Adeline; Groussin, Olivier; Gutierrez, Pedro J.; Güttler,
Carsten; Hofmann, Marc; Höfner, Sebastian; Hviid, Stubbe F.; Ip,
Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kramm, J. -Rainer;
Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara,
Luisa M.; Lee, Jui-Chi; Lin, Zhong-Yi; Lopez Moreno, Jose J.;
Marzari, Francesco; Michalik, Harald; Mottola, Stefano; Preusker,
Frank; Scholten, Frank; Thomas, Nicholas; Toth, Imre; Tubiana, Cecilia
2016A&A...592L...2P Altcode:
<BR /> Aims: We calculate the size-frequency distribution of the
boulders on the southern hemisphere of comet 67P Churyumov-Gerasimenko
(67P), which was in shadow before the end of April 2015. We compare
the new results with those derived from the northern hemisphere
and equatorial regions of 67P, highlighting the possible physical
processes that lead to these boulder size distributions. <BR />
Methods: We used images acquired by the OSIRIS Narrow Angle Camera
(NAC) on 2 May 2015 at a distance of 125 km from the nucleus. The
scale of this dataset is 2.3 m/px; the high resolution of the images,
coupled with the favorable observation phase angle of 62°, provided the
possibility to unambiguously identify boulders ≥7 m on the surface
of 67P and to manually extract them with the software ArcGIS. We
derived the size-frequency distribution of the illuminated southern
hemisphere. <BR /> Results: We found a power-law index of -3.6 ± 0.2
for the boulders on the southern hemisphere with a diameter range of
7-35 m. The power-law index is equal to the one previously found on
northern and equatorial regions of 67P, suggesting that similar boulder
formation processes occur in both hemispheres. The power-law index is
related to gravitational events triggered by sublimation and/or thermal
fracturing causing regressive erosion. In addition, the presence of a
larger number of boulders per km<SUP>2</SUP> in the southern hemisphere,
which is a factor of 3 higher with respect to the northern hemisphere,
suggests that the southernmost terrains of 67P are affected by a
stronger thermal fracturing and sublimating activity, hence possibly
causing larger regressive erosion and gravitational events.
---------------------------------------------------------
Title: Aswan site on comet 67P/Churyumov-Gerasimenko: Morphology,
boulder evolution, and spectrophotometry
Authors: Pajola, Maurizio; Oklay, Nilda; La Forgia, Fiorangela;
Giacomini, Lorenza; Massironi, Matteo; Bertini, Ivano; El-Maarry,
M. R.; Marzari, Francesco; Preusker, Frank; Scholten, Frank; Höfner,
Sebastian; Lee, Jui-Chi; Vincent, Jean-Baptiste; Groussin, Olivier;
Naletto, Giampiero; Lazzarin, Monica; Barbieri, Cesare; Sierks,
Holger; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman,
Hans; Keller, Horst U.; Agarwal, Jessica; A'Hearn, Michael F.;
Barucci, Maria A.; Bertaux, Jean-Loup; Cremonese, Gabriele; Da
Deppo, Vania; Davidsson, Björn; De Cecco, Mariolino; Debei, Stefano;
Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Güttler, Carsten;
Gutierrez, Pedro J.; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda, Laurent;
Knollenberg, Jörg; Kramm, J. -Rainer; Küppers, Michael; Kürt,
Ekkehard; Lara, Luisa M.; Lin, Zhong-Yi; Lopez Moreno, Jose J.;
Magrin, Sara; Michalik, Harald; Mottola, Stefano; Thomas, Nicholas;
Tubiana, Cecilia
2016A&A...592A..69P Altcode:
<BR /> Aims: We provide a detailed morphological analysis of the
Aswan site on comet 67P/Churyumov-Gerasimenko (67P). We derive the
size-frequency distribution of boulders ≥2 m and correlate this
distribution with the gravitational slopes for the first time on a
comet. We perform the spectral analysis of this region to understand if
possible surface variegation is related to thedifferent surface textures
observable on the different units. <BR /> Methods: We used two OSIRIS
Narrow Angle Camera (NAC) image data sets acquired on September 19
and 22, 2014, with a scale of 0.5 m/px. Gravitational slopes derived
from the 3D shape model of 67P were used to identify and interpret
the different units of the site. By means of the high-resolution
NAC data sets, boulders ≥2.0 m can be unambiguously identified and
extracted using the software ArcGIS. Coregistered and photometrically
corrected color cubes were used to perform the spectral analyses,
and we retrieved the spectral properties of the Aswan units. <BR />
Results: The high-resolution morphological map of the Aswan site
(0.68 km<SUP>2</SUP>) shows that this site is characterized by
four different units: fine-particle deposits located on layered
terrains, gravitational accumulation deposits, taluses, and the
outcropping layered terrain. Multiple lineaments are identified on
the Aswan cliff, such as fractures, exposed layered outcrops, niches,
and terraces. Close to the terrace margin, several arched features
observed in plan view suggest that the margin progressively retreats
as a result of erosion. The size-frequency of boulders ≥2 m in
the entire study area has a power-law index of -3.9 +0.2/-0.3 (1499
boulders ≥2 m/km<SUP>2</SUP>), suggesting that the Aswan site is
mainly dominated by gravitational events triggered by sublimation and/or
thermal insolation weathering causing regressive erosion. The boulder
size-frequency distribution versus gravitational slopes indicates that
when higher gravitational slope terrains are considered, only boulders
≤10 m are identified, as well as steeper power-slope indices. In
addition, no boulders ≥2 m are observed on slopes ≥50°. This may
indicate that larger blocks detached from a sublimating cliff cannot
rest at these slopes and consequently fall down. The spectral analysis
performed on the site shows that despite different morphologic units, no
spectral differences appear in the multiple textures. This may confirm
a redistribution of particles across the nucleus as a consequence of
airfall, whether coming from Hapi or from the southern hemisphere when
it is active during perihelion.
---------------------------------------------------------
Title: Prominence material embedded in coronal mass ejections as
observed with the LASCO-C2 coronagraph using polarization diagnostic
Authors: Lamy, Philippe; Boclet, Brice; Koutchmy, Serge
2016cosp...41E1107L Altcode:
Prominences are believed to be caused by the formation of a flux
rope low in the magnetic structure that eventually erupts to form
the CME. Indeed, many CME onset models (e.g., flux cancellation,
mass loading) require the presence or formation of a prominence
in order for the CME to erupt. The remnants of the cool prominence
material is often seen as recognizable twisted structures inside the
CME in the lines of He II at 304 Å, of D3 HeI at 587.5 nm, and of
Hα at 656 nm, sometime up to a distance of several solar radii from
the surface in the latter lines. The orange filter of the LASCO-C2
coronagraph includes the D3 HeI line and its presence in the core of
CMEs can be unambiguously detected on polarized images as polarization
allows disentangling the contributions from the hot coronal plasma
(the polarized Thomson scattered light by electrons) and from the
unpolarised emission of cool prominence material. This has been made
possible by an in-depth calibration that removes adverse instrumental
effects. We will show several examples of CME with embedded prominence
material and we will attempt to estimate the mass of this material to
be compared with that of the CME. We will also exploit the polarization
measurements to reconstruct the 3D geometry of the observed CMEs.
---------------------------------------------------------
Title: Coronal mass ejections over solar cycle 23 and 24 from LASCO-C2
white-light images
Authors: Lamy, Philippe; Barlyaeva, Tatiana; Boclet, Brice
2016cosp...41E1108L Altcode:
It is now well established that coronal mass ejections (CMEs)
play a major role in the heliosphere, starting from the corona
to interplanetary space and interacting with planets. The almost
uninterrupted observations by the LASCO coronagraph onboard SOHO since
January 1996 have allowed an unprecedented view of CMEs over almost two
solar cycles 23 and 24. The ARTEMIS-II catalog based on their automatic
detection on high-quality calibrated synoptic maps of the corona offers
a dataset free of selection effects. It is thus possible to perform
an unbiased statistical analysis of their properties and investigate
how they evolve with solar activity. We will present an extended
comparison of their properties during the two solar cycles 23 and 24
emphasizing the differences. We will further compare them with those
of the standard indices of solar activity such as the international
sunspot number (SSN), the sunspot area (SSA) and the radio flux at 10.7
cm (F10.7) as well as those of their potential progenitors, flares
and eruptive prominences, in order to ascertain their connection,
and we will consider the two hemispheres separately whenever possible.
---------------------------------------------------------
Title: Detection of changes of the surface morphology of the nucleus
of comet 67P/Churyumov-Gerasimenko - Implications for the erosion
Authors: Lamy, Philippe; Groussin, Olivier; El-Maarry, M. R.; Faury,
Guillaume; Auger, Anne-Thérèse
2016cosp...41E1109L Altcode:
Search for morphological changes at the surface of the nucleus of comet
67P/Churyumov-Gerasimenko (67/P C-G) since its perihelion passage in
August 2015 has been a major objective of the OSIRIS team in order
to understand the erosion processes. At time of writing, the changes
detected so far at a distance of 48 km (that is a pixel scale of 90
cm for the OSIRIS Narrow Angle Camera) are subtle even in regions
which were the most exposed to solar illumination around perihelion
time: Imhotep, Khonsu and Khepry. In this presentation, we will
concentrate on the Khepry region where several changes of different
kinds have been positively detected: disappearance of several bright
spots, localized receding of a large part (roughly 40 x 130 m) of the
surface by approximately 12 m (that could result from either erosion
or localized collapse), and appearance of several new boulders. As
the Rosetta-comet distance will keep decreasing, we hope to report
further changes at the COSPAR conference. We will finally confront
quantitative estimates of the putative eroded mass with independent
evidences coming from in-situ as well as remote-sensing observations
carried over several past apparitions.
---------------------------------------------------------
Title: Physical properties and dynamical relation of the circular
depressions on comet 67P/Churyumov-Gerasimenko
Authors: Ip, W. -H.; Lai, I. -L.; Lee, J. -C.; Cheng, Y. -C.; Li,
Y.; Lin, Z. -Y.; Vincent, J. -B.; Besse, S.; Sierks, H.; Barbieri,
C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller,
H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux,
J. -L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.;
Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry,
M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.;
Güttler, C.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs, G.;
Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.;
Lazzarin, M.; López-Moreno, J. J.; Lowry, S.; Marchi, S.; Marzari,
F.; Michalik, H.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.;
Thomas, N.; Toth, E.; Tubiana, C.
2016A&A...591A.132I Altcode:
<BR /> Aims: We aim to characterize the circular depressions of
comet 67P/Churyumov-Gerasimenko and investigate whether such surface
morphology of a comet nucleus is related to the cumulative sublimation
effect since becoming a Jupiter family comet (JFC). <BR /> Methods:
The images from the Rosetta/OSIRIS science camera experiment are used
to construct size frequency distributions of the circular depression
structures on comet 67P and they are compared with those of the JFCs
81P/Wild 2, 9P/Tempel 1, and 103P/Hartley 2. The orbital evolutionary
histories of these comets over the past 100 000 yr are analyzed
statistically and compared with each other. <BR /> Results: The global
distribution of the circular depressions over the surface of 67P is
charted and classified. Descriptions are given to the characteristics
and cumulative size frequency distribution of the identified
features. Orbital statistics of the JFCs visited by spacecraft are
derived. <BR /> Conclusions: The size frequency distribution of the
circular depressions is found to have a similar power law distribution
to those of 9P/Tempel 1 and 81P/Wild 2. This might imply that they
could have been generated by the same process. Orbital integration
calculation shows that the surface erosion histories of 81P/Wild 2,
and 9P/Tempel 1 could be shorter than those of 67P, 103 P/Hartley 2 and
19P/Borrelly. From this point of view, the circular depressions could
be dated back to the pre-JFC phase or the transneptunian phase of these
comets. The north-south asymmetry in the distribution of the circular
depressions could be associated with the heterogeneous structure of
the nucleus of comet 67P and/or the solar insolation history.
---------------------------------------------------------
Title: Possible interpretation of the precession of comet
67P/Churyumov-Gerasimenko
Authors: Gutiérrez, P. J.; Jorda, L.; Gaskell, R. W.; Davidsson,
B. J. R.; Capanna, C.; Hviid, S. F.; Keller, H. U.; Maquet, L.;
Mottola, S.; Preusker, F.; Scholten, F.; Lara, L. M.; Moreno,
F.; Rodrigo, R.; Sierks, H.; Barbieri, C.; Lamy, P.; Koschny, D.;
Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Auger, A. T.; Barucci, M. A.;
Bertaux, J. L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.;
De Cecco, M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin,
O.; Gutiérrez-Marques, P.; Güttler, C.; Ip, W. H.; Knollenberg, J.;
Kramm, J. R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.;
López-Moreno, J. J.; Magrin, S.; Marchi, S.; Marzari, F.; Naletto,
G.; Oklay, N.; Pajola, M.; Pommerol, A.; Sabau, D.; Thomas, N.; Toth,
I.; Tubiana, C.; Vincent, J. B.
2016A&A...590A..46G Altcode:
Context. Data derived from the reconstruction of the nucleus shape
of comet 67P/Churyumov-Gerasimenko (67P) from images of the OSIRIS
camera onboard ROSETTA show evidence that the nucleus rotates in
complex mode. First, the orientation of the spin axis is not fixed in
an inertial reference frame, which suggests a precessing motion around
the angular momentum vector with a periodicity of approximately 257
h ± 12 h.Second, periodograms of the right ascension and declination
(RA/Dec) coordinates of the body-frame Z axis show a very significant
(higher than 99.99%) periodicity at 276 h ± 12 h, different from the
rotational period of 12.40 h as previously determined from light-curve
analysis. <BR /> Aims: The main goal is to interpret the data and
associated periodicities of the spin axis orientation in space. <BR
/> Methods: We analyzed the spin axis orientation in space and
associated periodicities and compared them with solutions of Euler
equations under the assumption that the body rotates in torque-free
conditions. Statistical tests comparing the observationally derived
spin axis orientation with the outcome from simulations were applied
to determine the most likely inertia moments, excitation level,
and periods. <BR /> Results: Under the assumption that the body is
solid-rigid and rotates in torque-free conditions, the most likely
interpretation is that 67P is spinning around the principal axis with
the highest inertia moment with a period of about 13 h. At the same
time, the comet precesses around the angular momentum vector with
a period of about 6.35 h. While the rotating period of such a body
would be about 12.4 h, RA/Dec coordinates of the spin axis would have
a periodicity of about 270 h as a result of the combination of the
two aforementioned motions. <BR /> Conclusions: The most direct and
simple interpretation of the complex rotation of 67P requires a ratio
of inertia moments significantly higher than that of a homogeneous body.
---------------------------------------------------------
Title: Subsurface Characterization of 67P/Churyumov-Gerasimenko’s
Abydos Site
Authors: Brugger, B.; Mousis, O.; Morse, A.; Marboeuf, U.; Jorda, L.;
Guilbert-Lepoutre, A.; Andrews, D.; Barber, S.; Lamy, P.; Luspay-Kuti,
A.; Mandt, K.; Morgan, G.; Sheridan, S.; Vernazza, P.; Wright, I. P.
2016ApJ...822...98B Altcode: 2016arXiv160305893B
On 2014 November 12, the ESA/Rosetta descent module Philae landed on
the Abydos site of comet 67P/Churyumov-Gerasimenko. Aboard this module,
the Ptolemy mass spectrometer measured a CO/CO<SUB>2</SUB> ratio of
0.07 ± 0.04, which differs substantially from the value obtained in
the coma by the Rosetta/ROSINA instrument, suggesting a heterogeneity
in the comet nucleus. To understand this difference, we investigated
the physicochemical properties of the Abydos subsurface, leading to
CO/CO<SUB>2</SUB> ratios close to that observed by Ptolemy at the
surface of this region. We used a comet nucleus model that takes into
account different water ice phase changes (amorphous ice, crystalline
ice, and clathrates) as well as diffusion of molecules throughout the
pores of the matrix. The input parameters of the model were optimized
for the Abydos site, and the ROSINA CO/CO<SUB>2</SUB> measured ratio is
assumed to correspond to the bulk value in the nucleus. We find that all
considered structures of water ice are able to reproduce the Ptolemy
observation with a time difference not exceeding ∼50 days, I.e.,
lower than ∼2% on 67P/Churyumov-Gerasimenko’s orbital period. The
suspected heterogeneity of 67P/Churyumov-Gerasimenko’s nucleus is also
found possible only if it is constituted of crystalline ices. If the icy
phase is made of amorphous ice or clathrates, the difference between
Ptolemy and ROSINA’s measurements would rather originate from the
spatial variations in illumination on the nucleus surface. An eventual
new measurement of the CO/CO<SUB>2</SUB> ratio at Abydos by Ptolemy
could be decisive to distinguish between the three water ice structures.
---------------------------------------------------------
Title: Extreme 3D reconstruction of the final ROSETTA/PHILAE
landing site
Authors: Capanna, Claire; Jorda, Laurent; Lamy, Philippe; Gesquiere,
Gilles; Delmas, Cédric; Durand, Joelle; Garmier, Romain; Gaudon,
Philippe; Jurado, Eric
2016EGUGA..18.4522C Altcode:
The Philae lander aboard the Rosetta spacecraft successfully landed
at the surface of comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G)
after two rebounds on November 12, 2014. The final landing site, now
known as « Abydos », has been identified on images acquired by the
OSIRIS imaging system onboard the Rosetta orbiter[1]. The available
images of Abydos are very limited in number and reveal a very extreme
topography containing cliffs and overhangs. Furthermore, the surface
is only observed under very high incidence angles of 60° on average,
which implies that the images also exhibit lots of cast shadows. This
makes it very difficult to reconstruct the 3D topography with standard
methods such as photogrammetry or standard clinometry. We apply a
new method called ”Multiresolution PhotoClinometry by Deformation”
(MPCD, [2]) to retrieve the 3D topography of the area around Abydos. The
method works in two main steps: (i) a DTM of this region is extracted
from a low resolution MPCD global shape model of comet 67P/C-G,
and (ii) the resulting triangular mesh is progressively deformed at
increasing spatial sampling down to 0.25 m in order to match a set
of 14 images of Abydos with projected pixel scales between 1 and 8
m. The method used to perform the image matching is a quasi-Newton
non-linear optimization method called L-BFGS-b[3] especially suited to
large-scale problems. Finally, we also checked the compatibility of the
final MPCD digital terrain model with a set of five panoramic images
obtained by the CIVA-P instrument aboard Philae[4]. [1] Lamy et al.,
2016, submitted. [2] Capanna et al., Three dimensional reconstruction
using multiresoluton photoclinometry by deformation, The visual
Computer, v. 29(6-8) pp. 825-835, 2013. [3] Morales et al., Remark on
"Algorithm 778: L-BFGS-B: Fortran subroutines for large-scale bound
constrained optimization", v.38(1) pp.1-4, ACM Trans. Math. Softw.,
2011 [4] Bibring et al., 67P/Churyumov-Gerasimenko surface properties
as derived from CIVA panoramic images, Science, v. 349(6247), 2015
---------------------------------------------------------
Title: 20 months at 67P/Churyumov-Gerasimenko: The view from
Rosetta/OSIRIS
Authors: Sierks, Holger; Güttler, Carsten; Barbieri, Cesare; Lamy,
Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans
2016EGUGA..1815782S Altcode:
After arrival in August 2014, the Rosetta spacecraft is now at
comet 67P/Churyumov-Gerasimenko for one and a half years. A rather
inactive body at that time was approaching the Sun, passing through
its perihelion and peak of activity in August/September 2015 and is
now moving out, away from the Sun. During the whole time, the comet
was observed by the scientific imaging system OSIRIS onboard Rosetta,
mapping the nucleus' surface and monitoring the comet's dust and gas
coma. This presentation shall summarize the results obtained so far by
the OSIRIS team and give a general picture on our current understanding
of comets in general and 67P in particular.
---------------------------------------------------------
Title: The State of the Corona During the Weak Solar Cycle 24:
the View from LASCO Images
Authors: Barlyaeva, T.; Lamy, P.; Llebaria, A.; Boclet, B.
2016ASPC..504..287B Altcode:
The LASCO-C2 coronagraph onboard SOHO continues its white-light imaging
of the corona from 1.5 to 6.0 solar radii, thus allowing investigating
the consequences of the weak Solar Cycle 24 on the corona and comparing
it to the previous cycle (23). Temporal variations of the global
radiance of the corona are presented. We pay particular attention to
the mid-term variations which are distinctly different between the
two cycles and highlight the similarities and differences. Finally,
we rely on our ARTEMIS II catalog of coronal mass ejections (CMEs)
to compare their global rates during these two cycles.
---------------------------------------------------------
Title: Observations and analysis of a curved jet in the coma of
comet 67P/Churyumov-Gerasimenko
Authors: Lin, Z. -Y.; Lai, I. -L.; Su, C. -C.; Ip, W. -H.; Lee, J. -C.;
Wu, J. -S.; Vincent, J. -B.; La Forgia, F.; Sierks, H.; Barbieri,
C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller,
H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.;
Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson,
B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.;
Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Jorda, L.; Knollenberg,
J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.;
Lazzarin, M.; López-Moreno, J. J.; Lowry, S.; Marzari, F.; Michalik,
H.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Rożek, A.;
Thomas, N.; Tubiana, C.
2016A&A...588L...3L Altcode: 2016arXiv160502095L
<BR /> Aims: We analyze the physical properties and dynamical
origin of a curved jet of comet 67P/Churyumov-Gerasimenko that was
observed repeatedly in several nucleus rotations starting on May 30
and persisting until early August, 2015. <BR /> Methods: We simulated
the motion of dust grains ejected from the nucleus surface under the
influence of the gravity and viscous drag effect of the expanding gas
flow from the rotating nucleus. <BR /> Results: The formation of the
curved jet is a combination of the size of the dust particles (~0.1-1
mm) and the location of the source region near the nucleus equator. This
enhances the spiral feature of the collimated dust stream after the dust
is accelerated to a terminal speed on the order of m s<SUP>-1</SUP>.
---------------------------------------------------------
Title: Evolution of the Dust Size Distribution of Comet
67P/Churyumov-Gerasimenko from 2.2 au to Perihelion
Authors: Fulle, M.; Marzari, F.; Della Corte, V.; Fornasier, S.;
Sierks, H.; Rotundi, A.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Rickman, H.; Keller, H. U.; López-Moreno, J. J.;
Accolla, M.; Agarwal, J.; A'Hearn, M. F.; Altobelli, N.; Barucci,
M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Bussoletti, E.;
Colangeli, L.; Cosi, M.; Cremonese, G.; Crifo, J. -F.; Da Deppo,
V.; Davidsson, B.; Debei, S.; De Cecco, M.; Esposito, F.; Ferrari,
M.; Giovane, F.; Gustafson, B.; Green, S. F.; Groussin, O.; Grün,
E.; Gutierrez, P.; Güttler, C.; Herranz, M. L.; Hviid, S. F.; Ip,
W.; Ivanovski, S. L.; Jerónimo, J. M.; Jorda, L.; Knollenberg, J.;
Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Leese,
M. R.; López-Jiménez, A. C.; Lucarelli, F.; Mazzotta Epifani, E.;
McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno,
F.; Mottola, S.; Naletto, G.; Oklay, N.; Ortiz, J. L.; Palomba, E.;
Palumbo, P.; Perrin, J. -M.; Rietmeijer, F. J. M.; Rodríguez, J.;
Sordini, R.; Thomas, N.; Tubiana, C.; Vincent, J. -B.; Weissman, P.;
Wenzel, K. -P.; Zakharov, V.; Zarnecki, J. C.
2016ApJ...821...19F Altcode:
The Rosetta probe, orbiting Jupiter-family comet
67P/Churyumov-Gerasimenko, has been detecting individual dust particles
of mass larger than 10<SUP>-10</SUP> kg by means of the GIADA dust
collector and the OSIRIS Wide Angle Camera and Narrow Angle Camera
since 2014 August and will continue until 2016 September. Detections
of single dust particles allow us to estimate the anisotropic dust flux
from 67P, infer the dust loss rate and size distribution at the surface
of the sunlit nucleus, and see whether the dust size distribution of
67P evolves in time. The velocity of the Rosetta orbiter, relative
to 67P, is much lower than the dust velocity measured by GIADA, thus
dust counts when GIADA is nadir-pointing will directly provide the
dust flux. In OSIRIS observations, the dust flux is derived from the
measurement of the dust space density close to the spacecraft. Under
the assumption of radial expansion of the dust, observations in the
nadir direction provide the distance of the particles by measuring
their trail length, with a parallax baseline determined by the motion
of the spacecraft. The dust size distribution at sizes >1 mm
observed by OSIRIS is consistent with a differential power index of
-4, which was derived from models of 67P’s trail. At sizes <1 mm,
the size distribution observed by GIADA shows a strong time evolution,
with a differential power index drifting from -2 beyond 2 au to -3.7
at perihelion, in agreement with the evolution derived from coma and
tail models based on ground-based data. The refractory-to-water mass
ratio of the nucleus is close to six during the entire inbound orbit
and at perihelion.
---------------------------------------------------------
Title: Mapping of the source regions of the dust jets on comet 67P
Authors: Ip, Wing-Huen; Lai, Ian-Lin; Lee, Jui-Chi; Lin, Zhong-Yi;
Chen, Yu; Chien, Ting-Wei; Chen, Yu-Min; Vincent, Jean-Baptiste;
Sierks, Holger; Barbieri, Cesare; Lamy, Philippe. L.; Rodrigo, Rafael;
Koschny, Detlef; Rickman, Hans; Keller, Uwe; Osiris Team
2016EGUGA..18.5347I Altcode:
Because of the inclination of the rotational axis to the orbital
plane and the orbital motion around the Sun, the sunlit regions on
the nucleus surface of comet 67P/Churyumov-Gerasimenko moved from the
northern hemisphere to the sourthern hemisphere between August, 2014
and October, 2015. From the comparison of the dust jet features in
images taken at successive time series, the footpoints of these jets
can be identified by a projection method. The distributiosn of the
corresponding source regions can be compared with the geomorphology
of the nucleus surface from inbound to outbound. The correlation
of the dust jet activity with the volatile outgassing phenomenon as
monitored by different scientific instruments onboard Rosetta will
provide important information on the sublimation process.
---------------------------------------------------------
Title: Photometry of dust grains of comet 67P and connection with
nucleus regions
Authors: Cremonese, G.; Simioni, E.; Ragazzoni, R.; Bertini, I.;
La Forgia, F.; Pajola, M.; Oklay, N.; Fornasier, S.; Lazzarin, M.;
Lucchetti, A.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.;
Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Agarwal,
J.; Barucci, M. A.; Bertaux, J. -L.; Da Deppo, V.; Davidsson, B.;
De Cecco, M.; Debei, S.; Fulle, M.; Groussin, O.; Güttler, C.;
Gutierrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg,
J.; Kramm, J. -R.; Kueppers, M.; Kürt, E.; Lara, L. M.; Magrin, S.;
Lopez Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Preusker,
F.; Scholten, F.; Thomas, N.; Tubiana, C.; Vincent, J. -B.
2016A&A...588A..59C Altcode:
<BR /> Aims: Multiple pairs of high-resolution images of the dust coma
of comet 67P/Churyumov-Gerasimenko have been collected by OSIRIS onboard
Rosetta allowing extraction and analysis of dust grain tracks. <BR
/> Methods: We developed a quasi automatic method to recognize and
to extract dust tracks in the Osiris images providing size, FWHM and
photometric data. The dust tracks characterized by a low signal-to-noise
ratio were checked manually. We performed the photometric analysis
of 70 dust grain tracks observed on two different Narrow Angle Camera
images in the two filters F24 and F28, centered at λ = 480.7 nm and
at λ = 743.7 nm, respectively, deriving the color and the reddening
of each one. We then extracted several images of the nucleus observed
with the same filters and with the same phase angle to be compared
with the dust grain reddening. <BR /> Results: Most of the dust grain
reddening is very similar to the nucleus values, confirming they come
from the surface or subsurface layer. The histogram of the dust grain
reddening has a secondary peak at negative values and shows some grains
with values higher than the nucleus, suggesting a different composition
from the surface grains. One hypothesis comes from the negative values
point at the presence of hydrated minerals in the comet.
---------------------------------------------------------
Title: The dust environment of comet 67P/Churyumov-Gerasimenko from
Rosetta OSIRIS and VLT observations in the 4.5 to 2.9 AU heliocentric
distance range inbound
Authors: Moreno, F.; Snodgrass, C.; Hainaut, O.; Tubiana, C.; Sierks,
H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.;
Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux,
J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Da Deppo,
V.; Davidsson, B.; Debei, S.; De Cecco, M.; Ferri, F.; Fornasier,
S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marques,
P.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg,
J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.;
Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto,
G.; Oklay, N.; Pajola, M.; Thomas, N.; Vincent, J. B.; Della Corte,
V.; Fitzsimmons, A.; Faggi, S.; Jehin, E.; Opitom, C.; Tozzi, G. -P.
2016A&A...587A.155M Altcode: 2016arXiv160201965M
Context. The ESA Rosetta spacecraft, currently orbiting around comet
67P/Churyumov-Gerasimenko, has already provided in situ measurements
of the dust grain properties from several instruments,particularly
OSIRIS and GIADA. We propose adding value to those measurements by
combining them with ground-based observations of the dust tail to
monitor the overall, time-dependent dust-production rate and size
distribution. <BR /> Aims: To constrain the dust grain properties,
we take Rosetta OSIRIS and GIADA results into account, and combine
OSIRIS data during the approach phase (from late April to early June
2014) with a large data set of ground-based images that were acquired
with the ESO Very Large Telescope (VLT) from February to November
2014. <BR /> Methods: A Monte Carlo dust tail code, which has already
been used to characterise the dust environments of several comets and
active asteroids, has been applied to retrieve the dust parameters. Key
properties of the grains (density, velocity, and size distribution) were
obtained from Rosetta observations: these parameters were used as input
of the code to considerably reduce the number of free parameters. In
this way, the overall dust mass-loss rate and its dependence on the
heliocentric distance could be obtained accurately. <BR /> Results:
The dust parameters derived from the inner coma measurements by OSIRIS
and GIADA and from distant imaging using VLT data are consistent,
except for the power index of the size-distribution function, which
is α = -3, instead of α = -2, for grains smaller than 1 mm. This is
possibly linked to the presence of fluffy aggregates in the coma. The
onset of cometary activity occurs at approximately 4.3 AU, with a dust
production rate of 0.5 kg/s, increasing up to 15 kg/s at 2.9 AU. This
implies a dust-to-gas mass ratio varying between 3.8 and 6.5 for the
best-fit model when combined with water-production rates from the
MIRO experiment.
---------------------------------------------------------
Title: Are fractured cliffs the source of cometary dust jets? Insights
from OSIRIS/Rosetta at 67P/Churyumov-Gerasimenko
Authors: Vincent, J. -B.; Oklay, N.; Pajola, M.; Höfner, S.;
Sierks, H.; Hu, X.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny,
D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Barucci, M. A.;
Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese,
G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry,
M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.;
Gutiérrez-Marquez, P.; Güttler, C.; Hofmann, M.; Hviid, S. F.;
Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.;
Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.;
Lopez Moreno, J. J.; Lowry, S.; Marzari, F.; Massironi, M.; Moreno,
F.; Mottola, S.; Naletto, G.; Preusker, F.; Scholten, F.; Shi, X.;
Thomas, N.; Toth, I.; Tubiana, C.
2016A&A...587A..14V Altcode: 2015arXiv151203193V
Context. Dust jets (I.e., fuzzy collimated streams of cometary material
arising from the nucleus) have been observed in situ on all comets
since the Giotto mission flew by comet 1P/Halley in 1986, and yet
their formation mechanism remains unknown. Several solutions have been
proposed involving either specific properties of the active areas or the
local topography to create and focus the gas and dust flows. While the
nucleus morphology seems to be responsible for the larger features, high
resolution imagery has shown that broad streams are composed of many
smaller jets (a few meters wide) that connect directly to the nucleus
surface. <BR /> Aims: We monitored these jets at high resolution and
over several months to understand what the physical processes are that
drive their formation and how this affects the surface. <BR /> Methods:
Using many images of the same areas with different viewing angles,
we performed a 3-dimensional reconstruction of collimated jets and
linked them precisely to their sources on the nucleus. <BR /> Results:
We show here observational evidence that the northern hemisphere
jets of comet 67P/Churyumov-Gerasimenko arise from areas with sharp
topographic changes and describe the physical processes involved. We
propose a model in which active cliffs are the main source of jet-like
features and therefore of the regions eroding the fastest on comets. We
suggest that this is a common mechanism taking place on all comets.
---------------------------------------------------------
Title: The Comparison of Total Electron Content Between Radio and
Thompson Scattering
Authors: Jensen, E. A.; Frazin, R.; Heiles, C.; Lamy, P.; Llebaria,
A.; Anderson, J. D.; Bisi, M. M.; Fallows, R. A.
2016SoPh..291..465J Altcode: 2016SoPh..tmp....2J
The total electron content (TEC) of the solar corona in June 2002
is calculated by three observational techniques and the results are
compared. The first technique is solar rotational tomography (SRT)
applied to a 14-day time series of LASCO-C2 polarized brightness images,
and the other two techniques use the Cassini spacecraft radio beacon
for Doppler tracking (phase delay) and ranging (group delay). While
the Doppler-tracking technique has an arbitrary zero-point, it is
otherwise found that the three methods produce consistent estimates of
the TEC to within established uncertainties, providing an independent
check on the calibrations. The verification of the accuracy of the
Doppler-tracking technique enables a significant improvement to the
use of spacecraft data sets in studying the heliosphere: the density
component to Faraday rotation can be separated from the magnetic-field
component as variable structures cross, such as coronal mass ejections
and magnetohydrodynamic waves. Furthermore, we show that the unique
frequency-time variable characteristics of the hydrodynamic components
of waves can be studied. Based on this work, future Faraday rotation
studies of variable solar phenomena will isolate the electron density
changes from the magnetic-field contribution. This capability will
enable advanced research into variable heliospheric magnetic fields.
---------------------------------------------------------
Title: THERMAP: a mid-infrared spectro-imager for space missions to
small bodies in the inner solar system
Authors: Groussin, O.; Licandro, J.; Helbert, J.; Reynaud, J. L.;
Levacher, P.; Reyes García-Talavera, M.; Alí-Lagoa, V.; Blanc, P. E.;
Brageot, E.; Davidsson, B.; Delbó, M.; Deleuze, M.; Delsanti, A.;
Diaz Garcia, J. J.; Dohlen, K.; Ferrand, D.; Green, S. F.; Jorda, L.;
Joven Álvarez, E.; Knollenberg, J.; Kührt, E.; Lamy, P.; Lellouch,
E.; Le Merrer, J.; Marty, B.; Mas, G.; Rossin, C.; Rozitis, B.;
Sunshine, J.; Vernazza, P.; Vives, S.
2016ExA....41...95G Altcode: 2015arXiv150902725G; 2015ExA...tmp...56G
We present THERMAP, a mid-infrared spectro-imager for space missions
to small bodies in the inner solar system, developed in the framework
of the MarcoPolo-R asteroid sample return mission. THERMAP is very well
suited to characterize the surface thermal environment of a NEO and to
map its surface composition. The instrument has two channels, one for
imaging and one for spectroscopy: it is both a thermal camera with full
2D imaging capabilities and a slit spectrometer. THERMAP takes advantage
of the recent technological developments of uncooled microbolometer
arrays, sensitive in the mid-infrared spectral range. THERMAP can
acquire thermal images (8-18 μm) of the surface and perform absolute
temperature measurements with a precision better than 3.5 K above 200
K. THERMAP can acquire mid-infrared spectra (8-16 μm) of the surface
with a spectral resolution Δλ of 0.3 μm. For surface temperatures
above 350 K, spectra have a signal-to-noise ratio >60 in the spectral
range 9-13 μm where most emission features occur.
---------------------------------------------------------
Title: Variegation of comet 67P/Churyumov-Gerasimenko in regions
showing activity
Authors: Oklay, N.; Vincent, J. -B.; Fornasier, S.; Pajola, M.;
Besse, S.; Davidsson, B. J. R.; Lara, L. M.; Mottola, S.; Naletto, G.;
Sierks, H.; Barucci, A. M.; Scholten, F.; Preusker, F.; Pommerol, A.;
Masoumzadeh, N.; Lazzarin, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.;
Koschny, D.; Rickman, H.; A'Hearn, M. F.; Bertaux, J. -L.; Bertini,
I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco,
M.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hall,
I.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.;
Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers,
M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Marzari, F.; Moreno, F.; Shi,
X.; Thomas, N.; Toth, I.; Tubiana, C.
2016A&A...586A..80O Altcode:
Aims.We carried out an investigation of the surface variegation of comet
67P/Churyumov-Gerasimenko, the detection of regions showing activity,
the determination of active and inactive surface regions of the comet
with spectral methods, and the detection of fallback material. <BR
/> Methods: We analyzed multispectral data generated with Optical,
Spectroscopic, and Infrared Remote Imaging System (OSIRIS) narrow
angle camera (NAC) observations via spectral techniques, reflectance
ratios, and spectral slopes in order to study active regions. We
applied clustering analysis to the results of the reflectance ratios,
and introduced the new technique of activity thresholds to detect
areas potentially enriched in volatiles. <BR /> Results: Local
color inhomogeneities are detected over the investigated surface
regions. Active regions, such as Hapi, the active pits of Seth and
Ma'at, the clustered and isolated bright features in Imhotep, the
alcoves in Seth and Ma'at, and the large alcove in Anuket, have bluer
spectra than the overall surface. The spectra generated with OSIRIS
NAC observations are dominated by cometary emissions of around 700
nm to 750 nm as a result of the coma between the comet's surface and
the camera. One of the two isolated bright features in the Imhotep
region displays an absorption band of around 700 nm, which probably
indicates the existence of hydrated silicates. An absorption band with
a center between 800-900 nm is tentatively observed in some regions
of the nucleus surface. This absorption band can be explained by the
crystal field absorption of Fe<SUP>2+</SUP>, which is a common spectral
feature seen in silicates.
---------------------------------------------------------
Title: First analysis of the size-frequency distribution of boulders
ge 7m on comet 67P
Authors: Pajola, M.; Vincent, J. B.; Güttler, C.; Lee, J. -C.;
Massironi, M.; Bertini, I.; Simioni, E.; Marzari, F.; Giacomini, L.;
Barbieri, C.; Cremonese, G.; Naletto, G.; Pommerol, A.; El Maarry,
M. R.; Besse, S.; Küppers, M.; La Forgia, F.; Lazzarin, M.; Thomas,
N.; Auger, A. T.; Ip, W. -H.; Lin, Z. -Y.; Sierks, H.; OSIRIS Team;
A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Da Deppo, V.;
Davidsson, B.; De Cecco, M.; Debei, S.; Ferri, F.; Fornasier, S.;
Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hviid, S. F.; Jorda, L.;
Keller, H. U.; Knollenberg, J.; Koschny, D.; Kramm, J. -R.; Kürt,
E.; Lamy, P.; Lara, L. M.; Lopez Moreno, J. J.; Magrin, S.; Michalik,
H.; Moissl, R.; Mottola, S.; Oklay, N.; Preusker, F.; Rickman, H.;
Rodrigo, R.; Scholten, F.; Tubiana, C.
2016MmSAI..87..156P Altcode:
Images of the surface of comet 67P Churyumov-Gerasimenko taken by
the OSIRIS camera on board the Rosetta spacecraft have been used to
study the statistical distribution and morphological properties of
both cluster and isolated roundish structures ('boulders') scattered
all over the surface. We used NAC images taken on Aug 5-6, 2014, at a
distance between 131.45 - 109.76 km, with a spatial resolution ranging
from 2.44 - 2.03 m/px (Fig. 1). Such data cover a full rotation of 67P,
providing the first ever full size frequency distribution coverage of
boulders ≥ 7m visible on a cometary illuminated side. Boulders are
ubiquitous on the head, neck, and body of 67P \citep{thomas15}. The
initial count of 4,976 boulders was reduced to 3,546 for statistical
purposes taking into consideration only those with a diameter larger
than 7 m \citep{pajola15}.
---------------------------------------------------------
Title: Characterization of the Abydos region through OSIRIS
high-resolution images in support of CIVA measurements
Authors: Lucchetti, A.; Cremonese, G.; Jorda, L.; Poulet, F.; Bibring,
J. -P.; Pajola, M.; La Forgia, F.; Massironi, M.; El-Maarry, M. R.;
Oklay, N.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny,
D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci,
M. A.; Bertaux, J. -L.; Bertini, I.; Da Deppo, V.; Davidsson, B.;
Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.;
Gutierrez, P. J.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Knollenberg,
J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.;
Lopez Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Preusker,
F.; Scholten, F.; Thomas, N.; Tubiana, C.; Vincent, J. -B.
2016A&A...585L...1L Altcode:
Context. On 12 November 2014, the European mission Rosetta delivered
the Philae lander on the nucleus of comet 67P/Churyumov-Gerasimenko
(67P). After the first touchdown, the lander bounced three times before
finally landing at a site named Abydos. <BR /> Aims: We provide a
morphologically detailed analysis of the Abydos landing site to support
Philae's measurements and to give context for the interpretation of
the images coming from the Comet Infrared and Visible Analyser (CIVA)
camera system onboard the lander. <BR /> Methods: We used images
acquired by the OSIRIS Narrow Angle Camera (NAC) on 6 December 2014
to perform the analysis of the Abydos landing site, which provided the
geomorphological map, the gravitational slope map, the size-frequency
distribution of the boulders. We also computed the albedo and spectral
reddening maps. <BR /> Results: The morphological analysis of the region
could suggest that Philae is located on a primordial terrain. The Abydos
site is surrounded by two layered and fractured outcrops and presents
a 0.02 km<SUP>2</SUP> talus deposit rich in boulders. The boulder size
frequency distribution gives a cumulative power-law index of -4.0 +
0.3/-0.4, which is correlated with gravitational events triggered by
sublimation and/or thermal fracturing causing regressive erosion. The
average value of the albedo is 5.8% at λ<SUB>1</SUB> = 480.7 nm and
7.4% at λ<SUB>2</SUB> = 649.2 nm, which is similar to the global
albedos derived by OSIRIS and CIVA, respectively.
---------------------------------------------------------
Title: Sample of high-priority science objectives for future
interplanetary missions towards asteroids
Authors: Vernazza, Pierre; Beck, Pierre; Lamy, Philippe;
Guilbert-Lepoutre, Aurelie
2016RoAJ...26...35V Altcode:
In this paper, we present a sample of high-priority science objectives
for future interplanetary missions towards asteroids that were submitted
to ESA as a white paper in 2013
---------------------------------------------------------
Title: Sunset jets observed on comet 67P/Churyumov-Gerasimenko
sustained by subsurface thermal lag
Authors: Shi, X.; Hu, X.; Sierks, H.; Güttler, C.; A'Hearn, M.; Blum,
J.; El-Maarry, M. R.; Kührt, E.; Mottola, S.; Pajola, M.; Oklay, N.;
Fornasier, S.; Tubiana, C.; Keller, H. U.; Vincent, J. -B.; Bodewits,
D.; Höfner, S.; Lin, Z. -Y.; Gicquel, A.; Hofmann, M.; Barbieri,
C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Barucci,
M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.;
Davidsson, B.; Debei, S.; De Cecco, M.; Fulle, M.; Groussin, O.;
Gutiérrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg,
J.; Kovacs, G.; Kramm, J. -R.; Küppers, M.; Lara, L. M.; Lazzarin,
M.; Lopez-Moreno, J. J.; Marzari, F.; Naletto, G.; Thomas, N.
2016A&A...586A...7S Altcode:
We present observations of sunset jets on comet
67P/Churyumov-Gerasimenko by Rosetta/OSIRIS camera. In late April 2015,
when the comet was at a heliocentric distance of ~1.8 AU, clusters of
dust jets that originated in the Ma'at region on the comet's small lobe
were identified from multipleimages and were apparently sustained for
about an hour beyond local sunset. Emanating from the shadowed nucleus,
these jets became visible by solar illumination at their apparent
sources up to only a few tens of meters above the nucleus surface. We
investigate the plausibility of these jets as having been triggered by
water ice sublimation and sustained by thermal lag in the subsurface
beyond sunset. A general thermo-physical model was parameterized such
that the thermal lag in the subsurface is consistent with the elapsed
time of observation after sunset. It is found that the sublimation
of water ice from a depth of 6 mm and with a low thermal inertia of
50 W m<SUP>-2</SUP> K<SUP>-1</SUP> s<SUP>1/2</SUP> could explain the
spatial pattern and evolution of the apparent sources, particularly
their disappearance due to the eventual cooling of the subsurface. Our
analysis suggests that these sunset jets were essentially day-side
dust activities that continued after sunset. Specific observational
conditions for the sunset jets constrain their possible sources to
mostly within the less abrupt, dusty terrains. The uneven distribution
of these jets is possibly related to subsurface inhomogeneities in
the dusty area.
---------------------------------------------------------
Title: Coma dust environment observed by GIADA during the Perihelion
of 67P/Churyumov-Gerasimenko.
Authors: Rotundi, A.; Della Corte, V.; Fulle, M.; Ferrari, M.;
Ivanovski, S. L.; Sordini, R.; Mazzotta Epifani, E.; Palumbo, P.;
Colangeli, L.; Lopez-Moreno, J. J.; Rodriguez, J.; Zakharov, V.;
Bussoletti, E.; Crifo, J. F.; Esposito, F.; Green, S.; Gruen, E.;
Lamy, P. L.; McDonnell, T.; Mennella, V.; Molina, A.; Moreno, F.;
Ortiz, J. L.; Palomba, E.; Perrin, J. M.; Rodrigo, R.; Weissman,
P. R.; Zarnecki, J.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz,
M.; Jeronimo, J. M.; Leese, M.; Lopez-Jimenez, A.; Morales, R.
2015AGUFM.P33E..05R Altcode:
GIADA (Grain Impact Analyzer and Dust Accumulator) is an in-situ
instrument mounted onboard Rosetta monitoring the dust environment of
comet 67P/Churyumov-Gerasimenko. GIADA is composed of 3 sub-systems: 1)
the Grain Detection System, based on particle detection through light
scattering; 2) the Impact Sensor, giving momentum measurement; 3) the
Micro-Balances System, constituted of 5 quartz crystal microbalances,
giving cumulative deposited dust. The combination of the measurements
performed by these 3 subsystems provides: the number, the mass,
the momentum and the speed distribution of dust particles emitted
from the comet nucleus. We will present the coma dust environment as
observed by GIADA during the perihelion phase of the Rosetta space
mission. Despite the large distance from the nucleus, more than 200 km,
GIADA was able to detect temporal and spatial variation of dust density
distribution. Specific high dust spatial density sectors of the coma
have been identified and their evolution during the perihelion phase
was studied. Acknowledgements. GIADA was built by a consortium led
by the Univ. Napoli "Parthenope" & INAF- Oss. Astr. Capodimonte,
IT, in collaboration with the Inst. de Astrofisica de Andalucia,
ES, Selex-ES s.p.a. and SENER. GIADA is presently managed &
operated by Ist. di Astrofisica e Planetologia Spaziali-INAF,
IT. GIADA was funded and managed by the Agenzia Spaziale Italiana,
IT, with a support of the Spanish Ministry of Education and Science
MEC, ES. GIADA was developped from a PI proposal supported by the
University of Kent; sci. & tech. contribution given by CISAS,
IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and
USA. We thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for
their outstanding work. Science support provided by NASA through the US
Rosetta Project managed by JPL/California Institute of Technology. GIADA
calibrated data will be available through the ESA's PSA web site.
---------------------------------------------------------
Title: Morphology of the nucleus of Comet 67P/Churyumov--Gerasimenko
from stereo and high spatial resolution OSIRIS-NAC images
Authors: Lamy, P. L.; Groussin, O.; Romeuf, D.; Auger, A. T.; Jorda,
L.; Capanna, C.; Faury, G.
2015AGUFM.P31E2113L Altcode:
The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA's
Rosetta spacecraft has acquired images of the surface of the nucleus
of comet 67P/Churyumov-Gerasimenko at scales down to 0.2 m/pixel. We
employ a variety of techniques to characterize its morphology. Digital
terrain modeling (DTM), indispensable for quantitative morphological
analysis is performed using stereophotoclinometry (SPC). Depending
upon the observational coverage, the resolution of the DTMs exceeds
1 m in the most favorable cases. The ultimate stereographic analysis
is performed by exploiting pairs of images able to produce anaglyphs
whose spatial resolution surpasses that of the DTMs. Digital image
filtering and contrast enhancement techniques are applied on the
original images as appropriate. We first concentrate on the dust
covered terrains possibly resulting from airfall deposits, on the
quasi circular depressions or basins possibly connected to collapses
of the underground terrain, and on large scarps that suggest extensive
mass disruption. We pay special attention to lithologies that may
give clues to the subsurface structure of the nucleus. Our ultimate
goal is to understand the processes at work on the nucleus, directly
or indirectly connected to its activity as there appears to a variety
of processes far beyond what was classically considered in the past,
for instance airfall deposits, surface dust transport, mass wasting,
and insolation weathering.
---------------------------------------------------------
Title: The Subsurface Structure and Density of Cometary Nuclei
Authors: Lamy, P. L.; Herique, A.; Toth, I.
2015SSRv..197...85L Altcode: 2015SSRv..tmp...33L
Little is known about the internal structure and density of cometary
nuclei. Indirect evidences available so far are not compelling and these
questions essentially remain a matter of speculation. It is therefore
important to fully exploit the potential sources of information and
this is particularly the case of radar observations which have the
capability to probe the first few meters of cometary nuclei when they
come sufficiently close to Earth. We review the available results
and find that proper data are available for eight nuclei yielding
their geometric radar albedo and the dielectric permittivity of
their subsurface assuming that the scattering of the radar beam is
predominantly specular. The range of permittivity is quite broad,
extending from 1.7 to 3.1 although a more realistic interval is
probably 2 to 3.1 implying pronounced diversity in the subsurface
properties of cometary nuclei. A novel interpretation of these results
is performed based on the calculation of the dielectric permittivity
of various samples of three-phase mixtures of ice, dust and vacuum
using two mixing formulas and on the introduction of ternary diagrams
where the three axes correspond to the volumetric fraction of the three
phases. The derived values of the permittivity supplemented by a general
constraint on the dust-to-ice mass ratio define restricted regions in
the ternary diagrams broadly imposing that the ice fraction lies in
the range 0.1 to 0.2, the dust fraction in the range 0.2 to 0.5, and
the porosity in the range 35 % to 75 %. The density of the subsurface
of the considered eight nuclei is only constrained to the broad range
500 to 2000 kg m<SUP>-3</SUP> due to the poorly known density of the
dust phase. However, the results unambiguously reveal considerable
variation among cometary nuclei of the structure and properties of
their subsurface layers.
---------------------------------------------------------
Title: The Activity of Comet 67P/Churyumov-Gerasimenko as Seen by
Rosetta/OSIRIS
Authors: Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Rickman,
H.; Koschny, D.
2015AGUFM.P33E..02S Altcode:
The Rosetta mission of the European Space Agency arrived on August 6,
2014, at the target comet 67P/Churyumov-Gerasimenko. OSIRIS (Optical,
Spectroscopic, and Infrared Remote Imaging System) is the scientific
imaging system onboard Rosetta. OSIRIS consists of a Narrow Angle Camera
(NAC) for the nucleus surface and dust studies and a Wide Angle Camera
(WAC) for the wide field gas and dust coma investigations. OSIRIS
observed the coma and the nucleus of comet 67P/C-G during approach,
arrival, and landing of PHILAE. OSIRIS continued comet monitoring and
mapping of surface and activity in 2015 with close fly-bys with high
resolution and remote, wide angle observations. The scientific results
reveal a nucleus with two lobes and varied morphology. Active regions
are located at steep cliffs and collapsed pits which form collimated gas
jets. Dust is accelerated by the gas, forming bright jet filaments and
the large scale, diffuse coma of the comet. We will present activity
and surface changes observed in the Northern and Southern hemisphere
and around perihelion passage.
---------------------------------------------------------
Title: Subsurface characterization of 67P/Churyumov-Gerasimenko's
Abydos Site
Authors: Brugger, B.; Mousis, O.; Morse, A.; Marboeuf, U.; Jorda, L.;
Guilbert-Lepoutre, A.; Andrews, D.; Barber, S.; Lamy, P.; Luspay-Kuti,
A.; Mandt, K.; Morgan, G.; Sheridan, S.; Vernazza, P.; Wright, I. P.
2015sf2a.conf...53B Altcode:
We investigate the subsurface structure of comet
67P/Churyumov-Gerasimenko at the landing site of Rosetta's descent
module Philae. We use a cometary nucleus model with an optimized
parametrization and assume an initial composition derived from
Rosetta/ROSINA measurements. We compare the CO and CO_2 outgassing
rates derived from our model with those measured in situ by the Ptolemy
experiment aboard the Philae module on November 12, 2014. We find
results that allow us to place two main constraints on the subsurface
structure of this region: a low CO/CO_2 molar ratio is needed in the
nucleus, and the dust/ice mass ratio is higher at Abydos than in the
rest of the nucleus. These specific constraints on Abydos support the
statement of an important heterogeneity in 67P/Churyumov-Gerasimenko's
nucleus.
---------------------------------------------------------
Title: The primordial nucleus of Comet 67P/Churyumov-Gerasimenko
Authors: Davidsson, Bjorn; Sierks, Holger; Guettler, Carsten; Marzari,
Francesco; Pajola, Maurizio; Rickman, Hans; A'Hearn, Michael; Auger,
Anne-Therese; El-Maarry, Mohamed; Fornasier, Sonia; Gutierrez, Pedro;
Keller, Horst Uwe; Massironi, Matteo; Snodgrass, Colin; Vincent,
Jean-Baptiste; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael;
Koschny, Detlef; Barucci, Antonella; Bertaux, Jean-Loup; Bertini,
Ivano; Cremonese, Gabriele; Da Deppo, Vania; Debei, Stefano; De Cecco,
Mariolino; Feller, Clement; Fulle, Marco; Groussin, Olivier; Hviid,
Stubbe; Hoefner, Sebastian; Ip, Wing-Huen; Jorda, Laurent; Knollenberg,
Joerg; Kovacs, Gabor; Kramm, Joerg-Rainer; Kuehrt, Ekkehard; Kueppers,
Michael; La Forgia, Fiorangela; Lara, Luisa; Lazzarin, Monica; Lopez
Moreno, Jose; Moissl-Fraund, Richard; Mottola, Stefano; Naletto,
Giampiero; Oklay, Nilda; Thomas, Nicolas; Tubiana, Cecilia
2015DPS....4741315D Altcode:
Observations of Comet 67P/Churyumov-Gerasimenko by Rosetta show
that the nucleus is bi-lobed, extensively layered, has a low bulk
density, a high dust-to-ice mass ratio (implying high porosity),
and weak strength except for a thin sintered surface layer. The comet
is rich in supervolatiles (CO, CO2, N2), may contain amorphous water
ice, and displays little to no signs of aqueous alteration. Lack of
phyllosilicates in Stardust samples from Comet 81P/Wild 2 provides
further support that comet nuclei did not contain liquid water.These
properties differ from those expected for 50-200 km diameter bodies
in the primordial disk. We find that thermal processing due to
Al-26, combined with collisional compaction, creates a population
of medium-sized bodies that are comparably dense, compacted,
strong, heavily depleted in supervolatiles, containing little to no
amorphous water ice, and that have experienced extensive aqueous
alteration. Irregular satellites Phoebe and Himalia are potential
representatives of this population. Collisional rubble piles inherit
these properties from their parents. We therefore conclude that observed
comet nuclei are primordial rubble piles, and not collisional rubble
piles.We propose a concurrent comet and TNO formation scenario that
is consistent with these observations. We argue that TNOs form due
to streaming instabilities at sizes of about 50-400 km and that about
350 of these grow slowly in a low-mass primordial disk to the size of
Triton, causing little viscous stirring during growth. We propose a
dynamically cold primordial disk, that prevents medium-sized TNOs from
breaking into collisional rubble piles, and allows for the survival of
primordial rubble-pile comets. We argue that comets form by hierarchical
agglomeration out of material that remains after TNO formation. This
slow growth is necessary to avoid thermal processing by Al-26, and to
allow comet nuclei to incorporate 3 Myr old material from the inner
Solar System, found in Stardust samples. Growth in the Solar Nebula
creates porous single-lobe nuclei, while continued growth in a mildly
viscously stirred primordial disk creates denser outer layers, and
allow bi-lobe nucleus formation through mergers.
---------------------------------------------------------
Title: Temporal morphological changes at the surface of comet
67P/Churyumov-Gerasimenko
Authors: Groussin, Olivier; Sierks, H.; Barbieri, C.; Lamy, P.;
Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.
2015DPS....4750005G Altcode:
A key scientific question, to understand how comets work and whether
they still contain pristine materials at or near their surface,
is to understand how the nucleus is changing with time and to which
extent activity modifies its surface. Rosetta, which has been orbiting
comet 67P/Churyumov-Gerasimenko since August 2014, offers a unique
opportunity to tackle this fundamental question. Here, we report on
temporal morphological changes detected on the surface of the nucleus
of comet 67P by the OSIRIS cameras. Changes have been detected in
several regions and in particular in the Imhotep region, where they are
visible in the form of roundish features that are growing in size from
a given location in a preferential direction. Terrains bluer than the
surroundings appear during changes, suggesting the presence of (water)
ice exposed on the surface.
---------------------------------------------------------
Title: Pits Formation from Volatile Outgassing on
67P/Churyumov-Gerasimenko
Authors: Mousis, O.; Guilbert-Lepoutre, A.; Brugger, B.; Jorda, L.;
Kargel, J. S.; Bouquet, A.; Auger, A. -T.; Lamy, P.; Vernazza, P.;
Thomas, N.; Sierks, H.
2015ApJ...814L...5M Altcode: 2015arXiv151007671M
We investigate the thermal evolution of comet
67P/Churyumov-Gerasimenko’s subsurface in the Seth_01 region,
where active pits have been observed by the ESA/Rosetta mission. Our
simulations show that clathrate destabilization and amorphous ice
crystallization can occur at depths corresponding to those of the
observed pits in a timescale shorter than 67P/Churyumov-Gerasimenko’s
lifetime in the comet’s activity zone in the inner solar
system. Sublimation of crystalline ice down to such depths is possible
only in the absence of a dust mantle, which requires the presence of
dust grains in the matrix small enough to be dragged out by gas from the
pores. Our results are consistent with both pits formation via sinkholes
or subsequent to outbursts, the dominant process depending on the status
of the subsurface porosity. A sealed dust mantle would favor episodic
and disruptive outgassing as a result of increasing gas pressure in
the pores, while high porosity should allow the formation of large
voids in the subsurface due to the continuous escape of volatiles. We
finally conclude that the subsurface of 67P/Churyumov-Gerasimenko is
not uniform at a spatial scale of ∼100-200 m.
---------------------------------------------------------
Title: Size-frequency distribution of boulders ≥7 m on comet
67P/Churyumov-Gerasimenko
Authors: Pajola, Maurizio; Vincent, Jean-Baptiste; Güttler, Carsten;
Lee, Jui-Chi; Bertini, Ivano; Massironi, Matteo; Simioni, Emanuele;
Marzari, Francesco; Giacomini, Lorenza; Lucchetti, Alice; Barbieri,
Cesare; Cremonese, Gabriele; Naletto, Giampiero; Pommerol, Antoine;
El-Maarry, Mohamed R.; Besse, Sébastien; Küppers, Michael; La
Forgia, Fiorangela; Lazzarin, Monica; Thomas, Nicholas; Auger,
Anne-Thérèse; Sierks, Holger; Lamy, Philippe; Rodrigo, Rafael;
Koschny, Detlef; Rickman, Hans; Keller, Horst U.; Agarwal, Jessica;
A'Hearn, Michael F.; Barucci, Maria A.; Bertaux, Jean-Loup; Da
Deppo, Vania; Davidsson, Björn; De Cecco, Mariolino; Debei, Stefano;
Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Groussin, Olivier;
Gutierrez, Pedro J.; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda, Laurent;
Knollenberg, Jörg; Kramm, J. -Rainer; Kürt, Ekkehard; Lara, Luisa M.;
Lin, Zhong-Yi; Lopez Moreno, Jose J.; Magrin, Sara; Marchi, Simone;
Michalik, Harald; Moissl, Richard; Mottola, Stefano; Oklay, Nilda;
Preusker, Frank; Scholten, Frank; Tubiana, Cecilia
2015A&A...583A..37P Altcode:
<BR /> Aims: We derive for the first time the size-frequency
distribution of boulders on a comet, 67P/Churyumov-Gerasimenko (67P),
computed from the images taken by the Rosetta/OSIRIS imaging system. We
highlight the possible physical processes that lead to these boulder
size distributions. <BR /> Methods: We used images acquired by the
OSIRIS Narrow Angle Camera, NAC, on 5 and 6 August 2014. The scale
of these images (2.44-2.03 m/px) is such that boulders ≥7 m can
be identified and manually extracted from the datasets with the
software ArcGIS. We derived both global and localized size-frequency
distributions. The three-pixel sampling detection, coupled with the
favorable shadowing of the surface (observation phase angle ranging
from 48° to 53°), enables unequivocally detecting boulders scattered
all over the illuminated side of 67P. <BR /> Results: We identify 3546
boulders larger than 7 m on the imaged surface (36.4 km<SUP>2</SUP>),
with a global number density of nearly 100/km<SUP>2</SUP> and a
cumulative size-frequency distribution represented by a power-law
with index of -3.6 +0.2/-0.3. The two lobes of 67P appear to have
slightly different distributions, with an index of -3.5 +0.2/-0.3
for the main lobe (body) and -4.0 +0.3/-0.2 for the small lobe
(head). The steeper distribution of the small lobe might be due to a
more pervasive fracturing. The difference of the distribution for the
connecting region (neck) is much more significant, with an index value
of -2.2 +0.2/-0.2. We propose that the boulder field located in the
neck area is the result of blocks falling from the contiguous Hathor
cliff. The lower slope of the size-frequency distribution we see today
in the neck area might be due to the concurrent processes acting on
the smallest boulders, such as i) disintegration or fragmentation and
vanishing through sublimation; ii) uplifting by gas drag and consequent
redistribution; and iii) burial beneath a debris blanket. We also
derived the cumulative size-frequency distribution per km<SUP>2</SUP>
of localized areas on 67P. By comparing the cumulative size-frequency
distributions of similar geomorphological settings, we derived similar
power-law index values. This suggests that despite the selected
locations on different and often opposite sides of the comet, similar
sublimation or activity processes, pit formation or collapses, as well
as thermal stresses or fracturing events occurred on multiple areas
of the comet, shaping its surface into the appearance we see today.
---------------------------------------------------------
Title: Regional surface morphology of comet 67P/Churyumov-Gerasimenko
from Rosetta/OSIRIS images
Authors: El-Maarry, M. R.; Thomas, N.; Giacomini, L.; Massironi, M.;
Pajola, M.; Marschall, R.; Gracia-Berná, A.; Sierks, H.; Barbieri,
C.; Lamy, P. L.; Rodrigo, R.; Rickman, H.; Koschny, D.; Keller,
H. U.; Agarwal, J.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.;
Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.;
Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Güttler, C.;
Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hviid, S. F.;
Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.;
Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.;
Lopez Moreno, J. J.; Marchi, S.; Marzari, F.; Michalik, H.; Naletto,
G.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten, F.; Tubiana,
C.; Vincent, J. -B.
2015A&A...583A..26E Altcode:
<BR /> Aims: The OSIRIS camera onboard the Rosetta spacecraft
has been acquiring images of the comet 67P/Churyumov-Gerasimenko
(67P)'s nucleus at spatial resolutions down to ~0.17 m/px ever since
Aug. 2014. These images have yielded unprecedented insight into the
morphological diversity of the comet's surface. This paper presents
an overview of the regional morphology of comet 67P. <BR /> Methods:
We used the images that were acquired at orbits ~20-30 km from the
center of the comet to distinguish different regions on the surface
and introduce the basic regional nomenclature adopted by all papers
in this Rosetta special feature that address the comet's morphology
and surface processes. We used anaglyphs to detect subtle regional and
topographical boundaries and images from close orbit (~10 km from the
comet's center) to investigate the fine texture of the surface. <BR />
Results: Nineteen regions have currently been defined on the nucleus
based on morphological and/or structural boundaries, and they can be
grouped into distinctive region types. Consolidated, fractured regions
are the most common region type. Some of these regions enclose smooth
units that appear to settle in gravitational sinks or topographically
low areas. Both comet lobes have a significant portion of their surface
covered by a dusty coating that appears to be recently placed and shows
signs of mobilization by aeolian-like processes. The dusty coatings
cover most of the regions on the surface but are notably absent from
a couple of irregular large depressions that show sharp contacts with
their surroundings and talus-like deposits in their interiors, which
suggests that short-term explosive activity may play a significant role
in shaping the comet's surface in addition to long-term sublimation
loss. Finally, the presence of layered brittle units showing signs
of mechanical failure predominantly in one of the comet's lobes
can indicate a compositional heterogeneity between the two lobes. <P
/>Tables 2 and 3 and Appendix A are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201525723/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Orbital elements of the material surrounding comet
67P/Churyumov-Gerasimenko
Authors: Davidsson, B. J. R.; Gutiérrez, P. J.; Sierks, H.; Barbieri,
C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller,
H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.;
Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.;
De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Güttler, C.;
Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.;
Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.;
Lazzarin, M.; Lopez Moreno, J. J.; Lowry, S.; Magrin, S.; Marzari,
F.; Michalik, H.; Moissl-Fraund, R.; Naletto, G.; Oklay, N.; Pajola,
M.; Snodgrass, C.; Thomas, N.; Tubiana, C.; Vincent, J. -B.
2015A&A...583A..16D Altcode:
Context. We investigate the dust coma within the Hill sphere of comet
67P/Churyumov-Gerasimenko. <BR /> Aims: We aim to determine osculating
orbital elements for individual distinguishable but unresolved
slow-moving grains in the vicinity of the nucleus. In addition,
we perform photometry and constrain grain sizes. <BR /> Methods: We
performed astrometry and photometry using images acquired by the OSIRIS
Wide Angle Camera on the European Space Agency spacecraft Rosetta. Based
on these measurements, we employed standard orbit determination
and orbit improvement techniques. <BR /> Results: Orbital elements
and effective diameters of four grains were constrained, but we were
unable to uniquely determine them. Two of the grains have light curves
that indicate grain rotation. <BR /> Conclusions: The four grains have
diameters nominally in the range 0.14-0.50 m. For three of the grains,
we found elliptic orbits, which is consistent with a cloud of bound
particles around the nucleus. However, hyperbolic escape trajectories
cannot be excluded for any of the grains, and for one grain this is
the only known option. One grain may have originated from the surface
shortly before observation. These results have possible implications
for the understanding of the dispersal of the cloud of bound debris
around comet nuclei, as well as for understanding the ejection of
large grains far from the Sun.
---------------------------------------------------------
Title: Geomorphology of the Imhotep region on comet
67P/Churyumov-Gerasimenko from OSIRIS observations
Authors: Auger, A. -T.; Groussin, O.; Jorda, L.; Bouley, S.; Gaskell,
R.; Lamy, P. L.; Capanna, C.; Thomas, N.; Pommerol, A.; Sierks, H.;
Barbieri, C.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.;
Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini,
I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco,
M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.;
Güttler, C.; Hviid, S.; Ip, W. -H.; Knollenberg, J.; Kramm, J. -R.;
Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin,
M.; Lopez Moreno, J. J.; Marchi, S.; Marzari, F.; Massironi, M.;
Michalik, H.; Naletto, G.; Oklay, N.; Pajola, M.; Sabau, L.; Tubiana,
C.; Vincent, J. -B.; Wenzel, K. -P.
2015A&A...583A..35A Altcode:
Context. Since August 2014, the OSIRIS Narrow Angle Camera (NAC) onboard
the Rosetta spacecraft has acquired high spatial resolution images of
the nucleus of comet 67P/Churyumov-Gerasimenko, down to the decimeter
scale. This paper focuses on the Imhotep region, located on the largest
lobe of the nucleus, near the equator. <BR /> Aims: We map, inventory,
and describe the geomorphology of the Imhotep region. We propose and
discuss some processes to explain the formation and ongoing evolution of
this region. <BR /> Methods: We used OSIRIS NAC images, gravitational
heights and slopes, and digital terrain models to map and measure the
morphologies of Imhotep. <BR /> Results: The Imhotep region presents a
wide variety of terrains and morphologies: smooth and rocky terrains,
bright areas, linear features, roundish features, and boulders. Gravity
processes such as mass wasting and collapse play a significant role
in the geomorphological evolution of this region. Cometary processes
initiate erosion and are responsible for the formation of degassing
conduits that are revealed by elevated roundish features on the
surface. We also propose a scenario for the formation and evolution
of the Imhotep region; this implies the presence of large primordial
voids inside the nucleus, resulting from its formation process.
---------------------------------------------------------
Title: Geomorphology and spectrophotometry of Philae's landing site
on comet 67P/Churyumov-Gerasimenko
Authors: La Forgia, F.; Giacomini, L.; Lazzarin, M.; Massironi, M.;
Oklay, N.; Scholten, F.; Pajola, M.; Bertini, I.; Cremonese, G.;
Barbieri, C.; Naletto, G.; Simioni, E.; Preusker, F.; Thomas, N.;
Sierks, H.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller,
H. U.; Agarwal, J.; Auger, A. -T.; A'Hearn, M. F.; Barucci, M. A.;
Bertaux, J. -L.; Besse, S.; Bodewits, D.; Da Deppo, V.; Davidsson, B.;
Debei, S.; De Cecco, M.; El-Maarry, M. R.; Ferri, F.; Fornasier, S.;
Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hall, I.;
Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.;
Kührt, E.; Küppers, M.; Lara, L. -M.; Lopez Moreno, J. J.; Magrin,
S.; Marzari, F.; Michalik, H.; Mottola, S.; Pommerol, A.; Tubiana,
C.; Vincent, J. -B.
2015A&A...583A..41L Altcode:
Context. On 12 November 2014 the European mission Rosetta succeeded
in delivering a lander, named Philae, on the surface of one of
the smallest, low-gravity and most primitive bodies of the solar
system, the comet 67P/Churyumov-Gerasimenko (67P). <BR /> Aims:
The aim of this paper is to provide a comprehensive geomorphological
and spectrophotometric analysis of Philae's landing site (Agilkia)
to give an essential framework for the interpretation of its in situ
measurements. <BR /> Methods: OSIRIS images, coupled with gravitational
slopes derived from the 3D shape model based on stereo-photogrammetry
were used to interpret the geomorphology of the site. We adopted the
Hapke model, using previously derived parameters, to photometrically
correct the images in orange filter (649.2 nm). The best approximation
to the Hapke model, given by the Akimov parameter-less function,
was used to correct the reflectance for the effects of viewing and
illumination conditions in the other filters. Spectral analyses on
coregistered color cubes were used to retrieve spectrophotometric
properties. <BR /> Results: The landing site shows an average normal
albedo of 6.7% in the orange filter with variations of ~15% and a global
featureless spectrum with an average red spectral slope of 15.2%/100
nm between 480.7 nm (blue filter) and 882.1 nm (near-IR filter). The
spatial analysis shows a well-established correlation between the
geomorphological units and the photometric characteristics of the
surface. In particular, smooth deposits have the highest reflectance
a bluer spectrum than the outcropping material across the area. <BR
/> Conclusions: The featureless spectrum and the redness of the
material are compatible with the results by other instruments that
have suggested an organic composition. The observed small spectral
variegation could be due to grain size effects. However, the combination
of photometric and spectral variegation suggests that a compositional
differentiation is more likely. This might be tentatively interpreted
as the effect of the efficient dust-transport processes acting on
67P. High-activity regions might be the original sources for smooth
fine-grained materials that then covered Agilkia as a consequence of
airfall of residual material. More observations performed by OSIRIS
as the comet approaches the Sun would help interpreting the processes
that work at shaping the landing site and the overall nucleus.
---------------------------------------------------------
Title: Shape model, reference system definition, and cartographic
mapping standards for comet 67P/Churyumov-Gerasimenko -
Stereo-photogrammetric analysis of Rosetta/OSIRIS image data
Authors: Preusker, F.; Scholten, F.; Matz, K. -D.; Roatsch, T.;
Willner, K.; Hviid, S. F.; Knollenberg, J.; Jorda, L.; Gutiérrez,
P. J.; Kührt, E.; Mottola, S.; A'Hearn, M. F.; Thomas, N.; Sierks,
H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.;
Keller, H. U.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini,
I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco,
M.; Fornasier, S.; Fulle, M.; Groussin, O.; Güttler, C.; Ip, W. -H.;
Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno,
J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Oklay, N.; Tubiana,
C.; Vincent, J. -B.
2015A&A...583A..33P Altcode:
We analyzed more than 200 OSIRIS NAC images with a pixel scale of
0.9-2.4 m/pixel of comet 67P/Churyumov-Gerasimenko (67P) that have been
acquired from onboard the Rosetta spacecraft in August and September
2014 using stereo-photogrammetric methods (SPG). We derived improved
spacecraft position and pointing data for the OSIRIS images and a
high-resolution shape model that consists of about 16 million facets
(2 m horizontal sampling) and a typical vertical accuracy at the
decimeter scale. From this model, we derive a volume for the northern
hemisphere of 9.35 km<SUP>3</SUP> ± 0.1 km<SUP>3</SUP>. With the
assumption of a homogeneous density distribution and taking into
account the current uncertainty of the position of the comet's
center-of-mass, we extrapolated this value to an overall volume
of18.7 km<SUP>3</SUP>± 1.2 km<SUP>3</SUP>, and, with a current best
estimate of 1.0 × 10<SUP>13</SUP> kg for the mass, we derive a bulk
density of 535 kg/m<SUP>3</SUP>± 35 kg/m<SUP>3</SUP>. Furthermore,
we used SPG methods to analyze the rotational elements of 67P. The
rotational period for August and September 2014 was determined to
be 12.4041 ± 0.0004 h. For the orientation of the rotational axis
(z-axis of the body-fixed reference frame) we derived a precession
model with a half-cone angle of 0.14°, a cone center position at
69.54°/64.11° (RA/Dec J2000 equatorial coordinates), and a precession
period of 10.7 days. For the definition of zero longitude (x-axis
orientation), we finally selected the boulder-like Cheops feature on
the big lobe of 67P and fixed its spherical coordinates to 142.35°
right-hand-rule eastern longitude and -0.28° latitude. This completes
the definition of the new Cheops reference frame for 67P. Finally,
we defined cartographic mapping standards for common use and combined
analyses of scientific results that have been obtained not only
within the OSIRIS team, but also within other groups of the Rosetta
mission. <P />Appendices are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201526349/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Insolation, erosion, and morphology of comet
67P/Churyumov-Gerasimenko
Authors: Keller, H. U.; Mottola, S.; Davidsson, B.; Schröder, S. E.;
Skorov, Y.; Kührt, E.; Groussin, O.; Pajola, M.; Hviid, S. F.;
Preusker, F.; Scholten, F.; A'Hearn, M. F.; Sierks, H.; Barbieri,
C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Barucci, M. A.;
Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei,
S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Ip,
W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Küppers, M.; Lara,
L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Michalik, H.;
Naletto, G.; Sabau, L.; Thomas, N.; Vincent, J. -B.; Wenzel, K. -P.;
Agarwal, J.; Güttler, C.; Oklay, N.; Tubiana, C.
2015A&A...583A..34K Altcode:
Context. The complex shape of comet 67P and its oblique rotation axis
cause pronounced seasonal effects. Irradiation and hence activity vary
strongly. <BR /> Aims: We investigate the insolation of the cometary
surface in order to predict the sublimation of water ice. The strongly
varying erosion levels are correlated with the topography and morphology
of the present cometary surface and its evolution. <BR /> Methods: The
insolation as a function of heliocentric distance and diurnal (spin
dependent) variation is calculated using >10<SUP>5</SUP> facets
of a detailed digital terrain model. Shading, but also illumination
and thermal radiation by facets in the field of view of a specific
facet are iteratively taken into account. We use a two-layer model of
a thin porous dust cover above an icy surface to calculate the water
sublimation, presuming steady state and a uniform surface. Our second
model, which includes the history of warming and cooling due to thermal
inertia, is restricted to a much simpler shape model but allows us to
test various distributions of active areas. <BR /> Results: Sublimation
from a dirty ice surface yields maximum erosion. A thin dust cover
of 50 μm yields similar rates at perihelion. Only about 6% of the
surface needs to be active to match the observed water production rates
at perihelion. A dust layer of 1 mm thickness suppresses the activity
by a factor of 4 to 5. Erosion on the south side can reach more than
10 m per orbit at active spots. The energy input to the concave neck
area (Hapi) during northern summer is enhanced by about 50% owing to
self-illumination. Here surface temperatures reach maximum values along
the foot of the Hathor wall. Integrated over the whole orbit this area
receives the least energy input. Based on the detailed shape model,
the simulations identify "hot spots" in depressions and larger pits in
good correlation with observed dust activity. Three-quarters of the
total sublimation is produced while the sub-solar latitude is south,
resulting in a distinct dichotomy in activity and morphology. <BR />
Conclusions: The northern areas display a much rougher morphology
than what is seen on Imhotep, an area at the equator that will be
fully illuminated when 67P is closer to the Sun. Self-illumination
in concave regions enhance the energy input and hence erosion. This
explains the early activity observed at Hapi. Cliffs are more
prone to erosion than horizontal, often dust covered, areas, which
leads to surface planation. Local activity can only persist if the
forming cliff walls are eroding. Comet 67P has two lobes and also two
distinct sides. Transport of material from the south to the north is
probable. The morphology of the Imhotep plain should be typical for
the terrains of the yet unseen southern hemisphere.
---------------------------------------------------------
Title: Morphology and dynamics of the jets of comet
67P/Churyumov-Gerasimenko: Early-phase development
Authors: Lin, Z. -Y.; Ip, W. -H.; Lai, I. -L.; Lee, J. -C.; Vincent,
J. -B.; Lara, L. M.; Bodewits, D.; Sierks, H.; Barbieri, C.; Lamy,
P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal,
J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.;
Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco,
M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.;
Güttler, C.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs, G.;
Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.;
López-Moreno, J. J.; Lowry, S.; Marzari, F.; Michalik, H.; Mottola,
S.; Naletto, G.; Oklay, N.; Pajola, M.; Rożek, A.; Thomas, N.; Liao,
Y.; Tubiana, C.
2015A&A...583A..11L Altcode:
<BR /> Aims: The OSIRIS camera onboard the Rosetta spacecraft obtained
close-up views of the dust coma of comet 67P. The jet structures can be
used to trace their source regions and to examine the possible effect
of gas-surface interaction. <BR /> Methods: We analyzed the wide-angle
images obtained in the special dust observation sequences between
August and September 2014. The jet features detected in different
images were compared to study their time variability. The locations
of the potential source regions of some of the jets are identified
by ray tracing. We used a ring-masking technique to calculate the
brightness distribution of dust jets along the projected distance. <BR
/> Results: The jets detected between August and September 2014 mostly
originated in the Hapi region. Morphological changes appeared over
a timescale of several days in September. The brightness slope of
the dust jets is much steeper than the background coma. This might
be related to the sublimation or fragmentation of the emitted dust
grains. Interaction of the expanding gas flow with the cliff walls on
both sides of Hapi could lead to erosion and material down-fall to the
nucleus surface. <P />Appendix A is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201525961/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Redistribution of particles across the nucleus of comet
67P/Churyumov-Gerasimenko
Authors: Thomas, N.; Davidsson, B.; El-Maarry, M. R.; Fornasier, S.;
Giacomini, L.; Gracia-Berná, A. G.; Hviid, S. F.; Ip, W. -H.; Jorda,
L.; Keller, H. U.; Knollenberg, J.; Kührt, E.; La Forgia, F.; Lai,
I. L.; Liao, Y.; Marschall, R.; Massironi, M.; Mottola, S.; Pajola,
M.; Poch, O.; Pommerol, A.; Preusker, F.; Scholten, F.; Su, C. C.;
Wu, J. S.; Vincent, J. -B.; Sierks, H.; Barbieri, C.; Lamy, P. L.;
Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Barucci,
M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.;
Debei, S.; de Cecco, M.; Fulle, M.; Groussin, O.; Gutierrez, P. J.;
Kramm, J. -R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno,
J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Agarwal, J.; Güttler,
C.; Oklay, N.; Tubiana, C.
2015A&A...583A..17T Altcode:
Context. We present an investigation of the surface properties of areas
on the nucleus of comet 67P/Churyumov-Gerasimenko. <BR /> Aims: We aim
to show that transport of material from one part of the cometary nucleus
to another is a significant mechanism that influences the appearance
of the nucleus and the surface thermal properties. <BR /> Methods: We
used data from the OSIRIS imaging system onboard the Rosetta spacecraft
to identify surface features on the nucleus that can be produced by
various transport mechanisms. We used simple calculations based on
previous works to establish the plausibility of dust transport from one
part of the nucleus to another. <BR /> Results: We show by observation
and modeling that "airfall" as a consequence of non-escaping large
particles emitted from the neck region of the nucleus is a plausible
explanation for the smooth thin deposits in the northern hemisphere
of the nucleus. The consequences are also discussed. We also present
observations of aeolian ripples and ventifacts. We show by numerical
modeling that a type of saltation is plausible even under the rarified
gas densities seen at the surface of the nucleus. However, interparticle
cohesive forces present difficulties for this model, and an alternative
mechanism for the initiation of reptation and creep may result from
the airfall mechanism. The requirements on gas density and other
parameters of this alternative make it a more attractive explanation
for the observations. The uncertainties and implications are discussed.
---------------------------------------------------------
Title: Comet 67P/Churyumov-Gerasimenko: Constraints on its origin
from OSIRIS observations
Authors: Rickman, H.; Marchi, S.; A'Hearn, M. F.; Barbieri, C.;
El-Maarry, M. R.; Güttler, C.; Ip, W. -H.; Keller, H. U.; Lamy,
P.; Marzari, F.; Massironi, M.; Naletto, G.; Pajola, M.; Sierks, H.;
Koschny, D.; Rodrigo, R.; Barucci, M. A.; Bertaux, J. -L.; Bertini,
I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier,
S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Jorda,
L.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara,
L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Michalik, H.; Sabau, L.;
Thomas, N.; Vincent, J. -B.; Wenzel, K. -P.
2015A&A...583A..44R Altcode: 2015arXiv150507021R
Context. One of the main aims of the ESA Rosetta mission is to study the
origin of the solar system by exploring comet 67P/Churyumov-Gerasimenko
at close range. <BR /> Aims: In this paper we discuss the origin and
evolution of comet 67P/Churyumov-Gerasimenko in relation to that of
comets in general and in the framework of current solar system formation
models. <BR /> Methods: We use data from the OSIRIS scientific cameras
as basic constraints. In particular, we discuss the overall bi-lobate
shape and the presence of key geological features, such as layers
and fractures. We also treat the problem of collisional evolution of
comet nuclei by a particle-in-a-box calculation for an estimate of the
probability of survival for 67P/Churyumov-Gerasimenko during the early
epochs of the solar system. <BR /> Results: We argue that the two lobes
of the 67P/Churyumov-Gerasimenko nucleus are derived from two distinct
objects that have formed a contact binary via a gentle merger. The
lobes are separate bodies, though sufficiently similar to have formed
in the same environment. An estimate of the collisional rate in the
primordial, trans-planetary disk shows that most comets of similar
size to 67P/Churyumov-Gerasimenko are likely collisional fragments,
although survival of primordial planetesimals cannot be excluded. <BR />
Conclusions: A collisional origin of the contact binary is suggested,
and the low bulk density of the aggregate and abundance of volatile
species show that a very gentle merger must have occurred. We thus
consider two main scenarios: the primordial accretion of planetesimals,
and the re-accretion of fragments after an energetic impact onto a
larger parent body. We point to the primordial signatures exhibited
by 67P/Churyumov-Gerasimenko and other comet nuclei as critical tests
of the collisional evolution.
---------------------------------------------------------
Title: Large-scale dust jets in the coma of 67P/Churyumov-Gerasimenko
as seen by the OSIRIS instrument onboard Rosetta
Authors: Lara, L. M.; Lowry, S.; Vincent, J. -B.; Gutiérrez, P. J.;
Rożek, A.; La Forgia, F.; Oklay, N.; Sierks, H.; Barbieri, C.; Lamy,
P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal,
J.; Auger, A. -T.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.;
Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Davidsson,
B.; Da Deppo, V.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Ferri,
F.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez-Marques, P.;
Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.;
Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lazzarin, M.;
Lin, Z. -Y.; López-Moreno, J. J.; Magrin, S.; Marzari, F.; Michalik,
H.; Moissl-Fraund, R.; Moreno, F.; Mottola, S.; Naletto, G.; Pajola,
M.; Pommerol, A.; Thomas, N.; Sabau, M. D.; Tubiana, C.
2015A&A...583A...9L Altcode:
Context. During the most recent perihelion passage in 2009 of comet
67P/Churyumov-Gerasimenko (67P), ground-based observations showed
an anisotropic dust coma where jet-like features were detected at ~
1.3 AU from the Sun. The current perihelion passage is exceptional as
the Rosetta spacecraft is monitoring the nucleus activity since March
2014, when a clear dust coma was already surrounding the nucleus at
4.3 AU from the Sun. Subsequently, the OSIRIS camera also witnessed
an outburst in activity between April 27 and 30, and since mid-July,
the dust coma at r<SUB>h</SUB> ~ 3.7-3.6 AU preperihelion is clearly
non-isotropic, pointing to the existence of dust jet-like features. <BR
/> Aims: We aim to ascertain on the nucleus surface the origin of the
dust jet-like features detected as early as in mid-July 2014. This will
help to establish how the localized comet nucleus activity compares
with that seen in previous apparitions and will also help following its
evolution as the comet approaches its perihelion, at which phase most
of the jets were detected from ground-based observations. Determining
these areas also allows locating them in regions on the nucleus with
spectroscopic or geomorphological distinct characteristics. <BR />
Methods: Three series of dust images of comet 67P obtained with the
Wide Angle Camera (WAC) of the OSIRIS instrument onboard the Rosetta
spacecraft were processed with different enhancement techniques. This
was made to clearly show the existence of jet-like features in the
dust coma, whose appearance toward the observer changed as a result
of the rotation of the comet nucleus and of the changing observing
geometry from the spacecraft. The position angles of these features
in the coma together with information on the observing geometry,
nucleus shape, and rotation, allowed us to determine the most likely
locations on the nucleus surface where the jets originate from. <BR
/> Results: Geometrical tracing of jet sources indicates that the
activity of the nucleus of 67P gave rise during July and August 2014
to large-scale jet-like features from the Hapi, Hathor, Anuket, and
Aten regions, confirming that active regions may be present on the
nucleus localized at 60° northern latitude as deduced from previous
comet apparitions. There are also hints that large-scale jets observed
from the ground are possibly composed, at their place of origin on
the nucleus surface, of numerous small-scale features.
---------------------------------------------------------
Title: Search for satellites near comet 67P/Churyumov-Gerasimenko
using Rosetta/OSIRIS images
Authors: Bertini, I.; Gutiérrez, P. J.; Lara, L. M.; Marzari, F.;
Moreno, F.; Pajola, M.; La Forgia, F.; Sierks, H.; Barbieri, C.; Lamy,
P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal,
J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Cremonese, G.;
Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Ferri, F.;
Fornasier, S.; Fulle, M.; Giacomini, L.; Groussin, O.; Güttler, C.;
Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.;
Kührt, E.; Küppers, M.; Lazzarin, M.; Lopez Moreno, J. J.; Magrin,
S.; Massironi, M.; Michalik, H.; Mottola, S.; Naletto, G.; Oklay,
N.; Thomas, N.; Tubiana, C.; Vincent, J. -B.
2015A&A...583A..19B Altcode:
Context. TheEuropean Space Agency Rosetta mission reached and
started escorting its main target, the Jupiter-family comet
67P/Churyumov-Gerasimenko, at the beginning of August 2014. Within
the context of solar system small bodies, satellite searches from
approaching spacecraft were extensively used in the past to study the
nature of the visited bodies and their collisional environment. <BR />
Aims: During the approaching phase to the comet in July 2014, the OSIRIS
instrument onboard Rosetta performed a campaign aimed at detecting
objects in the vicinity of the comet nucleus and at measuring these
objects' possible bound orbits. In addition to the scientific purpose,
the search also focused on spacecraft security to avoid hazardous
material in the comet's environment. <BR /> Methods: Images in the
red spectral domain were acquired with the OSIRIS Narrow Angle Camera,
when the spacecraft was at a distance between 5785 km and 5463 km to
the comet, following an observational strategy tailored to maximize the
scientific outcome. From the acquired images, sources were extracted
and displayed to search for plausible displacements of all sources from
image to image. After stars were identified, the remaining sources were
thoroughly analyzed. To place constraints on the expected displacements
of a potential satellite, we performed Monte Carlo simulations on the
apparent motion of potential satellites within the Hill sphere. <BR />
Results: We found no unambiguous detections of objects larger than ~6
m within ~20 km and larger than ~1 m between ~20 km and ~110 km from
the nucleus, using images with an exposure time of 0.14 s and 1.36 s,
respectively. Our conclusions are consistent with independent works on
dust grains in the comet coma and on boulders counting on the nucleus
surface. Moreover, our analysis shows that the comet outburst detected
at the end of April 2014 was not strong enough to eject large objects
and to place them into a stable orbit around the nucleus. Our findings
underline that it is highly unlikely that large objects survive for
a long time around cometary nuclei.
---------------------------------------------------------
Title: Rotating dust particles in the coma of comet
67P/Churyumov-Gerasimenko
Authors: Fulle, M.; Ivanovski, S. L.; Bertini, I.; Gutierrez, P.;
Lara, L.; Sierks, H.; Zakharov, V.; Della Corte, V.; Rotundi, A.;
Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.;
Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux,
J. -L.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.;
Debei, S.; De Cecco, M.; Fornasier, S.; Groussin, O.; Güttler, C.;
Hviid, S. F.; Ip, W.; Jorda, L.; Knollenberg, J.; Kramm, R.; Kührt,
E.; Küppers, M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.;
Michalik, H.; Naletto, G.; Oklay, N.; Sabau, L.; Thomas, N.; Tubiana,
C.; Vincent, J. -B.; Wenzel, K. -P.
2015A&A...583A..14F Altcode:
Context. During September and October 2014, the OSIRIS cameras onboard
the ESA Rosetta mission detected millions of single particles. Many of
these dust particlesappear as long tracks (due to both the dust proper
motion and the spacecraft motion during the exposure time) with a clear
brightness periodicity. <BR /> Aims: We interpret the observed periodic
features as a rotational and translational motion of aspherical dust
grains. <BR /> Methods: By counting the peaks of each track, we obtained
statistics of a rotation frequency. We compared these results with
the rotational frequency predicted by a model of aspherical dust grain
dynamics in a model gas flow. By testing many possible sets of physical
conditions and grain characteristics, we constrained the rotational
properties of dust grains. <BR /> Results: We analyzed on the motion
of rotating aspherical dust grains with different cross sections in
flow conditions corresponding to the coma of 67P/Churyumov-Gerasimenko
qualitatively and quantitatively. Based on the OSIRIS observations,
we constrain the possible physical parameters of the grains.
---------------------------------------------------------
Title: Activity and jets of comet 67P, as observed by OSIRIS since
August 2014
Authors: Vincent, Jean-Baptiste; Oklay, Nilda; Pajola, Maurizio;
Höfner, Sebastian; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe;
Rodrigo, Rafael; Rickman, Hans; Koschny, Detlef
2015DPS....4741307V Altcode:
Dust jets, i.e. fuzzy collimated streams of cometary material arising
from the nucleus, have been observed in-situ on all comets since the
Giotto mission flew by comet 1P/Halley in 1986. Yet their formation
mechanism remains unknown. Several solutions have been proposed, from
localized physical mechanisms on the surface/sub-surface to purely
dynamical processes involving the focusing of gas flows by the local
topography. While the latter seems to be responsible forthe larger
features, high resolution imagery has shown that broad streams are
composed of many smaller features (a few meters wide) that connect
directly to the nucleus surface.The OSIRIS cameras on board Rosetta are
monitoring these jets in high resolution images since August 2014. We
followed this type of activity from 3.6 AU to perihelion (1.23 AU). We
have traced the jets back to their sources on the surface and noticed
a good correlation with sub-solar latitude, surface morphologies, and
color variations. As the comet receives more insolation, we observed
different type of jets, some of them sustained beyond the local sunset,
and an increasing number of transient events with sudden release of gas
and dust.We will present here how activity changes with local seasons
and how it contributes to the erosion of the surface.Acknowledgements:
OSIRIS was built by a consortium led by the Max-Planck-Institut für
Sonnensystemforschung, Göttingen, Germany, in collaboration with
CISAS, University of Padova, Italy, the Laboratoire d'Astrophysique de
Marseille, France, the Instituto de Astrofisica de Andalucia, CSIC,
Granada, Spain, the Scientific Support Office of the European Space
Agency, Noordwijk, The Netherlands, the Instituto Nacional de Tecnica
Aeroespacial, Madrid, Spain, the Universidad Politechnica de Madrid,
Spain, the Department of Physics and Astronomy of Uppsala University,
Sweden, and the Institut für Datentechnik und Kommunikationsnetze der
Technischen Universität Braunschweig, Germany. We thank the Rosetta
Science Ground Segment at ESAC, the Rosetta Mission Operations Centre
at ESOC and the Rosetta Project at ESTEC for their outstanding work
enabling the science return of the Rosetta Mission.
---------------------------------------------------------
Title: Temporal morphological changes in the Imhotep region of comet
67P/Churyumov-Gerasimenko
Authors: Groussin, O.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo,
R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Auger,
A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.;
Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco,
M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.;
Güttler, C.; Hviid, S.; Ip, W. -H.; Jorda, L.; Knollenberg, J.;
Kovacs, G.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.;
Lazzarin, M.; Lopez Moreno, J. J.; Lowry, S.; Marchi, S.; Marzari,
F.; Massironi, M.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.;
Pommerol, A.; Thomas, N.; Toth, I.; Tubiana, C.; Vincent, J. -B.
2015A&A...583A..36G Altcode: 2015arXiv150902794G
<BR /> Aims: We report on the first major temporal morphological
changes observed on the surface of the nucleus of comet
67P/Churyumov-Gerasimenko in the smooth terrains of the Imhotep
region. <BR /> Methods: We used images of the OSIRIS cameras onboard
Rosetta to follow the temporal changes from 24 May 2015 to 11 July
2015. <BR /> Results: The morphological changes observed on the
surface are visible in the form of roundish features that are growing
in size from a given location in a preferential direction at a rate of
5.6-8.1 × 10<SUP>-5</SUP> m s<SUP>-1</SUP> during the observational
period. The location where the changes started and the contours of the
expanding features are bluer than the surroundings, which suggests
that ices (H<SUB>2</SUB>O and/or CO<SUB>2</SUB>) are exposed on the
surface. However, sublimation of ices alone is not sufficient to explain
the observed expanding features. No significant variations in the dust
activity pattern are observed during the period of changes.
---------------------------------------------------------
Title: GIADA: shining a light on the monitoring of the comet dust
production from the nucleus of 67P/Churyumov-Gerasimenko
Authors: Della Corte, V.; Rotundi, A.; Fulle, M.; Gruen, E.;
Weissman, P.; Sordini, R.; Ferrari, M.; Ivanovski, S.; Lucarelli,
F.; Accolla, M.; Zakharov, V.; Mazzotta Epifani, E.; Lopez-Moreno,
J. J.; Rodriguez, J.; Colangeli, L.; Palumbo, P.; Bussoletti, E.;
Crifo, J. F.; Esposito, F.; Green, S. F.; Lamy, P. L.; McDonnell,
J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz,
J. L.; Palomba, E.; Perrin, J. M.; Rietmeijer, F. J. M.; Rodrigo, R.;
Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.;
Jeronimo, J. M.; Leese, M. R.; Lopez-Jimenez, A. C.; Altobelli, N.
2015A&A...583A..13D Altcode:
Context. During the period between 15 September 2014 and 4 February
2015, the Rosetta spacecraft accomplished the circular orbit phase
around the nucleus of comet 67P/Churyumov-Gerasimenko (67P). The Grain
Impact Analyzer and Dust Accumulator (GIADA) onboard Rosetta monitored
the 67P coma dust environment for the entire period. <BR /> Aims: We
aim to describe the dust spatial distribution in the coma of comet 67P
by means of in situ measurements. We determine dynamical and physical
properties of cometary dust particles to support the study of the
production process and dust environment modification. <BR /> Methods:
We analyzed GIADA data with respect to the observation geometry and
heliocentric distance to describe the coma dust spatial distribution
of 67P, to monitor its activity, and to retrieve information on active
areas present on its nucleus. We combined GIADA detection information
with calibration activity to distinguish different types of particles
that populate the coma of 67P: compact particles and fluffy porous
aggregates. By means of particle dynamical parameters measured by
GIADA, we studied the dust acceleration region. <BR /> Results: GIADA
was able to distinguish different types of particles populating the
coma of 67P: compact particles and fluffy porous aggregates. Most of
the compact particle detections occurred at latitudes and longitudes
where the spacecraft was in view of the comet's neck region of the
nucleus, the so-called Hapi region. This resulted in an oscillation
of the compact particle abundance with respect to the spacecraft
position and a global increase as the comet moved from 3.36 to 2.43
AU heliocentric distance. The speed of these particles, having masses
from 10<SUP>-10</SUP> to 10<SUP>-7</SUP> kg, ranged from 0.3 to 12.2 m
s<SUP>-1</SUP>. The variation of particle mass and speed distribution
with respect to the distance from the nucleus gave indications of the
dust acceleration region. The influence of solar radiation pressure on
micron and submicron particles was studied. The integrated dust mass
flux collected from the Sun direction, that is, particles reflected by
solar radiation pressure, was three times higher than the flux coming
directly from the comet nucleus. The awakening 67P comet shows a strong
dust flux anisotropy, confirming what was suggested by on-ground dust
coma observations performed in 2008.
---------------------------------------------------------
Title: Scientific assessment of the quality of OSIRIS images
Authors: Tubiana, C.; Güttler, C.; Kovacs, G.; Bertini, I.; Bodewits,
D.; Fornasier, S.; Lara, L.; La Forgia, F.; Magrin, S.; Pajola, M.;
Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.;
Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci,
M. A.; Bertaux, J. -L.; Besse, S.; Boudreault, S.; Cremonese, G.;
Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry,
M. R.; Fulle, M.; Groussin, O.; Gutiérrez-Marques, P.; Gutiérrez,
P. J.; Hoekzema, N.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.;
Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lazzarin,
M.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Michalik, H.;
Moissl, R.; Naletto, G.; Oklay, N.; Scholten, F.; Shi, X.; Thomas,
N.; Vincent, J. -B.
2015A&A...583A..46T Altcode:
Context. OSIRIS, the scientific imaging system onboard the
ESA Rosetta spacecraft, has been imaging the nucleus of comet
67P/Churyumov-Gerasimenko and its dust and gas environment since March
2014. The images serve different scientific goals, from morphology
and composition studies of the nucleus surface, to the motion and
trajectories of dust grains, the general structure of the dust coma,
the morphology and intensity of jets, gas distribution, mass loss, and
dust and gas production rates. <BR /> Aims: We present the calibration
of the raw images taken by OSIRIS and address the accuracy that we
can expect in our scientific results based on the accuracy of the
calibration steps that we have performed. <BR /> Methods: We describe
the pipeline that has been developed to automatically calibrate the
OSIRIS images. Through a series of steps, radiometrically calibrated and
distortion corrected images are produced and can be used for scientific
studies. Calibration campaigns were run on the ground before launch
and throughout the years in flight to determine the parameters that
are used to calibrate the images and to verify their evolution with
time. We describe how these parameters were determined and we address
their accuracy. <BR /> Results: We provide a guideline to the level of
trust that can be put into the various studies performed with OSIRIS
images, based on the accuracy of the image calibration.
---------------------------------------------------------
Title: Photometric properties of the nucleus of
67P/Churyumov-Gerasimenko from OSIRIS/Rosetta, space telescope,
and ground-based observations
Authors: Lamy, Philippe L.; Faury, Guillaume; Toth, Imre; Jorda,
Laurent; Gaskell, Robert; Groussin, Olivier; Capanna, Claire
2015DPS....4741303L Altcode:
In-situ imaging of the nucleus of comet 67P/Churyumov-Gerasimenko by the
OSIRIS Narrow Angle Camera (NAC) allows an in depth characterization of
its photometric properties that can be compared with remote observations
thus helping in the interpretation of other nuclei. We performed
a photometric analysis of both unresolved and resolved NAC images
of the nucleus obtained during twenty five observational campaigns
spreading from 23 March to 6 August 2014 with up to twelve filters whose
spectral coverage extended from 271 to 986 nm. An accurate photometric
calibration was obtained from the observations of a solar analog star,
16 Cyg B. We further combined this analysis with previous observations
obtained with the Hubble and Spitzer space telescopes and ground-based
telescopes. The analysis further incorporates the shape model and the
rotational state the nucleus of \67P independently determined from the
NAC images. We will present results on the geometric albedo, phase
function, color and thermal properties and put them in the broader
context of properties of cometary nuclei.
---------------------------------------------------------
Title: Gravitational slopes, geomorphology, and material strengths
of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS
observations
Authors: Groussin, O.; Jorda, L.; Auger, A. -T.; Kührt, E.; Gaskell,
R.; Capanna, C.; Scholten, F.; Preusker, F.; Lamy, P.; Hviid, S.;
Knollenberg, J.; Keller, U.; Huettig, C.; Sierks, H.; Barbieri,
C.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Agarwal,
J.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Boudreault, S.;
Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco,
M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.;
Güttler, C.; Ip, W. -H.; Kramm, J. -R.; Küppers, M.; Lazzarin, M.;
Lara, L. M.; Lopez Moreno, J. J.; Marchi, S.; Marzari, F.; Massironi,
M.; Michalik, H.; Naletto, G.; Oklay, N.; Pommerol, A.; Pajola, M.;
Thomas, N.; Toth, I.; Tubiana, C.; Vincent, J. -B.
2015A&A...583A..32G Altcode: 2015arXiv150902707G
<BR /> Aims: We study the link between gravitational slopes and the
surface morphology on the nucleus of comet 67P/Churyumov-Gerasimenko
and provide constraints on the mechanical properties of the cometary
material (tensile, shear, and compressive strengths). <BR /> Methods:
We computed the gravitational slopes for five regions on the nucleus
that are representative of the different morphologies observed on the
surface (Imhotep, Ash, Seth, Hathor, and Agilkia), using two shape
models computed from OSIRIS images by the stereo-photoclinometry (SPC)
and stereo-photogrammetry (SPG) techniques. We estimated the tensile,
shear, and compressive strengths using different surface morphologies
(overhangs, collapsed structures, boulders, cliffs, and Philae's
footprint) and mechanical considerations. <BR /> Results: The different
regions show a similar general pattern in terms of the relation between
gravitational slopes and terrain morphology: i) low-slope terrains
(0-20°) are covered by a fine material and contain a few large (>10
m) and isolated boulders; ii) intermediate-slope terrains (20-45°) are
mainly fallen consolidated materials and debris fields, with numerous
intermediate-size boulders from <1 m to 10 m for the majority of
them; and iii) high-slope terrains (45-90°) are cliffs that expose a
consolidated material and do not show boulders or fine materials. The
best range for the tensile strength of overhangs is 3-15 Pa (upper limit
of 150 Pa), 4-30 Pa for the shear strength of fine surface materials and
boulders, and 30-150 Pa for the compressive strength of overhangs (upper
limit of 1500 Pa). The strength-to-gravity ratio is similar for 67P
and weak rocks on Earth. As a result of the low compressive strength,
the interior of the nucleus may have been compressed sufficiently to
initiate diagenesis, which could have contributed to the formation of
layers. Our value for the tensile strength is comparable to that of
dust aggregates formed by gravitational instability and tends to favor
a formation of comets by the accrection of pebbles at low velocities.
---------------------------------------------------------
Title: OSIRIS observations of meter-sized exposures of H<SUB>2</SUB>O
ice at the surface of 67P/Churyumov-Gerasimenko and interpretation
using laboratory experiments
Authors: Pommerol, A.; Thomas, N.; El-Maarry, M. R.; Pajola, M.;
Groussin, O.; Auger, A. -T.; Oklay, N.; Fornasier, S.; Feller, C.;
Davidsson, B.; Gracia-Berná, A.; Jost, B.; Marschall, R.; Poch,
O.; Barucci, M. A.; Bertaux, J. -L.; La Forgia, F.; Keller, H. U.;
Kührt, E.; Lowry, S. C.; Mottola, S.; Naletto, G.; Sierks, H.;
Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.;
Agarwal, J.; A'Hearn, M. F.; Bertini, I.; Boudreault, S.; Cremonese,
G.; Da Deppo, V.; De Cecco, M.; Debei, S.; Güttler, C.; Fulle, M.;
Gutierrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg,
J.; Kovacs, G.; Kramm, J. -R.; Küppers, E.; Lara, L.; Lazzarin,
M.; Lopez Moreno, J. L.; Marzari, F.; Michalik, H.; Preusker, F.;
Scholten, F.; Tubiana, C.; Vincent, J. -B.
2015A&A...583A..25P Altcode:
Since OSIRIS started acquiring high-resolution observations of the
surface of the nucleus of comet 67P/Churyumov-Gerasimenko, over one
hundred meter-sized bright spots have been identified in numerous types
of geomorphologic regions, but mostly located in areas receiving low
insolation. The bright spots are either clustered, in debris fields
close to decameter-high cliffs, or isolated without structural relation
to the surrounding terrain. They can be up to ten times brighter than
the average surface of the comet at visible wavelengths and display a
significantly bluer spectrum. They do not exhibit significant changes
over a period of a few weeks. All these observations are consistent
with exposure of water ice at the surface of boulders produced by
dislocation of the weakly consolidated layers that cover large areas
of the nucleus. Laboratory experiments show that under simulated comet
surface conditions, analog samples acquire a vertical stratification
with an uppermost porous mantle of refractory dust overlaying a layer
of hard ice formed by recondensation or sintering under the insulating
dust mantle. The evolution of the visible spectrophotometric properties
of samples during sublimation is consistent with the contrasts of
brightness and color seen at the surface of the nucleus. Clustered
bright spots are formed by the collapse of overhangs that is triggered
by mass wasting of deeper layers. Isolated spots might be the result
of the emission of boulders at low velocity that are redepositioned
in other regions.
---------------------------------------------------------
Title: Spectrophotometric properties of the nucleus of comet
67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the
ROSETTA spacecraft
Authors: Fornasier, S.; Hasselmann, P. H.; Barucci, M. A.; Feller,
C.; Besse, S.; Leyrat, C.; Lara, L.; Gutierrez, P. J.; Oklay, N.;
Tubiana, C.; Scholten, F.; Sierks, H.; Barbieri, C.; Lamy, P. L.;
Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.;
A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo,
V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fulle, M.; Groussin, O.;
Güttler, C.; Hviid, S. F.; Ip, W.; Jorda, L.; Knollenberg, J.; Kovacs,
G.; Kramm, R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.;
Lopez Moreno, J. J.; Marzari, F.; Matz, K. -D.; Michalik, H.; Moreno,
F.; Mottola, S.; Naletto, G.; Pajola, M.; Pommerol, A.; Preusker,
F.; Shi, X.; Snodgrass, C.; Thomas, N.; Vincent, J. -B.
2015A&A...583A..30F Altcode: 2015arXiv150506888F
Context. The Rosetta mission of the European Space Agency has been
orbiting the comet 67P/Churyumov-Gerasimenko (67P) since August 2014
and is now in its escort phase. A large complement of scientific
experiments designed to complete the most detailed study of a comet
ever attempted are onboard Rosetta. <BR /> Aims: We present results for
the photometric and spectrophotometric properties of the nucleus of
67P derived from the OSIRIS imaging system, which consists of a Wide
Angle Camera (WAC) and a Narrow Angle Camera (NAC). The observations
presented here were performed during July and the beginning of
August 2014, during the approach phase, when OSIRIS was mapping the
surface of the comet with several filters at different phase angles
(1.3°-54°). The resolution reached up to 2.1 m/px. <BR /> Methods:
The OSIRIS images were processed with the OSIRIS standard pipeline,
then converted into I/F radiance factors and corrected for the
illumination conditions at each pixel using the Lommel-Seeliger disk
law. Color cubes of the surface were produced by stacking registered and
illumination-corrected images. Furthermore, photometric analysis was
performed both on disk-averaged photometry in several filters and on
disk-resolved images acquired with the NAC orange filter, centered at
649 nm, using Hapke modeling. <BR /> Results: The disk-averaged phase
function of the nucleus of 67P shows a strong opposition surge with
a G parameter value of -0.13 ± 0.01 in the HG system formalism and
an absolute magnitude H<SUB>v</SUB>(1,1,0) = 15.74 ± 0.02 mag. The
integrated spectrophotometry in 20 filters covering the 250-1000 nm
wavelength range shows a red spectral behavior, without clear absorption
bands except for a potential absorption centered at ~290 nm that is
possibly due to SO<SUB>2</SUB> ice. The nucleus shows strong phase
reddening, with disk-averaged spectral slopes increasing from 11%/(100
nm) to 16%/(100 nm) in the 1.3°-54° phase angle range. The geometric
albedo of the comet is 6.5 ± 0.2% at 649 nm, with local variations of
up to ~16% in the Hapi region. From the disk-resolved images we computed
the spectral slope together with local spectrophotometry and identified
three distinct groups of regions (blue, moderately red, and red). The
Hapi region is the brightest, the bluest in term of spectral slope,
and the most active surface on the comet. Local spectrophotometry shows
an enhancement of the flux in the 700-750 nm that is associated with
coma emissions. <P />Table 1 is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201525901/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: 3D reconstruction of the final PHILAE landing site: Abydos
Authors: Capanna, Claire; Jorda, Laurent; Lamy, Philippe; Gesquière,
Gilles; Delmas, Cédric; Durand, Joëlle; Gaudon, Philippe; Jurado,
Eric
2015DPS....4741311C Altcode:
The Abydos region is the region of the final landing site of the PHILAE
lander. The landing site has been potentially identified on images of
this region acquired by the OSIRIS imaging system aboard the orbiter
before (Oct 22, 2014) and after (Dec 6-13, 2014) the landing of PHILAE
(Lamy et al., in prep.). Assuming that this identification is correct,
we reconstructed the topography of Abydos in 3D using a method called
“multiresolution photoclinometry by deformation” (MPCD, Capanna et
al., The Visual Computer, 29(6-8): 825-835, 2013). The method works
in two steps: (a) a DTM of this region is extracted from the global
MPCD shape model, (b) the resulting triangular mesh is progressively
deformed at increasing spatial resolution in order to match a set
of 14 images of Abydos at pixel resolutions between 1 and 8 m. The
method used to perform the image matching is the L-BFGS-b non-linear
optimization (Morales et al., ACM Trans. Math. Softw., 38(1): 1-4,
2011).In spite of the very unfavourable illumination conditions, we
achieve a vertical accuracy of about 3 m, while the horizontal sampling
is 0.5 m. The accuracy is limited by high incidence angles on the images
(about 60 deg on average) combined with a complex topography including
numerous cliffs and a few overhangs. We also check the compatibility of
the local DTM with the images obtained by the CIVA-P instrument aboard
PHILAE. If the Lamy et al. identification is correct, our DTM shows that
PHILAE landed in a cavity at the bottom of a small cliff of 8 m height.
---------------------------------------------------------
Title: The nucleus of comet 67P through the eyes of the OSIRIS cameras
Authors: Guettler, Carsten; Sierks, Holger; Barbieri, Cesare; Lamy,
Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; OSIRIS Team;
Capaccioni, Fabrizio; Filacchione, Gianrico; Ciarniello, Mauro; Erard,
Stephane; Rinaldi, Giovanna; Tosi, Federico
2015DPS....4741301G Altcode:
The Rosetta spacecraft is studying comet 67P/Churyumov-Gerasimenko
from a close distance since August 2014. Onboard the spacecraft, the
two scientific cameras, the OSIRIS narrow- and the wide-angle camera,
are observing the cometary nucleus, its activity, as well as the dust
and gas environment.This overview paper will cover OSIRIS science from
the early arrival and mapping phase, the PHILAE landing, and the escort
phase including the two close fly-bys. With a first characterization
of global physical parameters of the nucleus, the OSIRIS cameras also
provided the data to reconstruct a 3D shape model of the comet and a
division into morphologic sub-units. From observations of near-surface
activity, jet-like features can be projected onto the surface and active
sources can be correlated with surface features like cliffs, pits,
or flat planes. The increase of activity during and after perihelion
in August 2015 showed several outbursts, which were seen as strong,
collimated jets originating from the southern hemisphere.A comparison
of results between different Rosetta instruments will give further
inside into the physics of the comet's nucleus and its coma. The OSIRIS
and VIRTIS instruments are particularly well suited to support and
complement each other. With an overlap in spectral range, one instrument
can provide the best spatial resolution while the other is strong in the
spectral resolution. A summary on collaborative efforts will be given.
---------------------------------------------------------
Title: Characterization of OSIRIS NAC filters for the interpretation
of multispectral data of comet 67P/Churyumov-Gerasimenko
Authors: Oklay, N.; Vincent, J. -B.; Sierks, H.; Besse, S.; Pajola, M.;
Bertini, I.; Rickman, H.; La Forgia, F.; Barucci, A. M.; Fornasier,
S.; Barbieri, C.; Koschny, D.; Lamy, P. L.; Rodrigo, R.; Agarwal,
J.; A'Hearn, M. F.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.;
Davidsson, B.; Debei, S.; De Cecco, M.; Fulle, M.; Groussin, O.;
Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.;
Keller, H. U.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers,
M.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.;
Michalik, H.; Naletto, G.; Thomas, N.; Tubiana, C.
2015A&A...583A..45O Altcode:
Context. We interpret multicolor data from OSIRISNAC for the
remote-sensing exploration of comet 67P/Churyumov-Gerasimenko. <BR />
Aims: We determine the most meaningful definition of color maps for
the characterization of surface variegation with filters available on
OSIRIS NAC. <BR /> Methods: We analyzed laboratory spectra of selected
minerals and olivine-pyroxene mixtures seen through OSIRIS NAC filters,
with spectral methods existing in the literature: reflectance ratios,
minimum band wavelength, spectral slopes, band tilt, band curvature,
and visible tilt. <BR /> Results: We emphasize the importance of
reflectance ratios and particularly the relation of visible tilt
vs. band tilt. This technique provides a reliable diagnostic of the
presence of silicates. Color maps constructed by red-green-blue colors
defined with the green, orange, red, IR, and Fe<SUB>2</SUB>O<SUB>3</SUB>
filters let us define regions that may significantly differ in
composition. <P />Appendices are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201525994/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: The use of 3D shape models of Rosetta targets for morphological
studies
Authors: Capanna, C.; Jorda, L.; Auger, A. -T.; Groussin, O.; Gaskell,
R.; Hviid, S.; Lamy, P.
2015EPSC...10..180C Altcode:
New 3D reconstruction techniques have been developed during the
last decade to retrieve the global and/or local topography of small
solar system bodies from visible images. These techniques can be
separated into two categories: the so-called "photoclinometric"
and the so-called "photogrammetric" techniques. Two implementations
of the photoclinometric technique are available: the SPC technique
(StereoPhotoClinometry) which combines sparse stereo with a classical
clinometry algorithm[1] and a more recent method called MSPCD (Multi-
Resolution Stereo-PhotoClinometry by Deformation) which proceeds
by iterative deformation of a triangular mesh in a multi-resolution
scheme[2], using stereo points as a guide during the deformation[3]. Our
study is based on the 3D shape models of the asteroid Lutetia and of
the comet 67P/Churyumov- Gerasimenko retrieved by the SPC and MSPCD
methods. More specifically, we describe how the models produced by
these two techniques can contribute to detailed and quantitative
studies of the morphological properties of small bodies through three
test cases shortly described below.• Measurement of crater depth
and depth-to-diameter distribution. We show that the reconstruction
techniques can lead to systematic differences in the measurement
of crater depth. This will be illustrated by a set of craters[4]
identified in the Achaia region at the surface of the asteroid
21 Lutetia. • Calculation of the volume of large boulders at the
surface of comet 67P/C-G. We show how the reconstruction technique
affects significantly the volume determination of a large boulder
named Cheops in the Imhotep region. • Measurement of gravitational
slopes. We discuss the differences between the gravitational slope
distributions in Seth obtained with the SPC and MSPCD models[5]. Since
no ground control points are available on small bodies, we use the
comparison of high-resolution images with the corresponding synthetic
images generated with the models[6] to assess their ability to retrieve
detailed topographic features at the surface of 67P/C-G and Lutetia.
---------------------------------------------------------
Title: Two independent and primitive envelopes of the bilobate
nucleus of comet 67P
Authors: Massironi, Matteo; Simioni, Emanuele; Marzari, Francesco;
Cremonese, Gabriele; Giacomini, Lorenza; Pajola, Maurizio; Jorda,
Laurent; Naletto, Giampiero; Lowry, Stephen; El-Maarry, Mohamed Ramy;
Preusker, Frank; Scholten, Frank; Sierks, Holger; Barbieri, Cesare;
Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans;
Keller, Horst Uwe; A'Hearn, Michael F.; Agarwal, Jessica; Auger,
Anne-Thérèse; Barucci, M. Antonella; Bertaux, Jean-Loup; Bertini,
Ivano; Besse, Sebastien; Bodewits, Dennis; Capanna, Claire; da Deppo,
Vania; Davidsson, Björn; Debei, Stefano; de Cecco, Mariolino; Ferri,
Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Groussin,
Olivier; Gutiérrez, Pedro J.; Güttler, Carsten; Hviid, Stubbe F.; Ip,
Wing-Huen; Knollenberg, Jörg; Kovacs, Gabor; Kramm, Rainer; Kührt,
Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M.;
Lazzarin, Monica; Lin, Zhong-Yi; Lopez Moreno, Josè J.; Magrin, Sara;
Michalik, Harald; Mottola, Stefano; Oklay, Nilda; Pommerol, Antoine;
Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste
2015Natur.526..402M Altcode:
The factors shaping cometary nuclei are still largely unknown, but
could be the result of concurrent effects of evolutionary and primordial
processes. The peculiar bilobed shape of comet 67P/Churyumov-Gerasimenko
may be the result of the fusion of two objects that were once separate
or the result of a localized excavation by outgassing at the interface
between the two lobes. Here we report that the comet's major lobe is
enveloped by a nearly continuous set of strata, up to 650 metres thick,
which are independent of an analogous stratified envelope on the minor
lobe. Gravity vectors computed for the two lobes separately are closer
to perpendicular to the strata than those calculated for the entire
nucleus and adjacent to the neck separating the two lobes. Therefore
comet 67P/Churyumov-Gerasimenko is an accreted body of two distinct
objects with `onion-like' stratification, which formed before they
merged. We conclude that gentle, low-velocity collisions occurred
between two fully formed kilometre-sized cometesimals in the early
stages of the Solar System. The notable structural similarities between
the two lobes of comet 67P/Churyumov-Gerasimenko indicate that the
early-forming cometesimals experienced similar primordial stratified
accretion, even though they formed independently.
---------------------------------------------------------
Title: Identification and Characterization of the landing site of
Philae from OSIRIS-NAC Images
Authors: Lamy, P.; Faury, G.; Jorda, L.; Romeuf, D.; Gaskell, R.;
Jurado, E.; Garmier, R.; Llebaria, A.; Auger, A. -T.; Capanna, C.
2015EPSC...10..783L Altcode:
On 12 November 2014, Philae rebounded from its first touchdown
at the selected Agilka "J" site on the nucleus of Comet
67P/Churyumov-Gerasimenko, an event captured by the Rosetta's OSIRIS
narrowangle camera (NAC [1]). Following two additional bounces,
Philae finally landed at the "K" site later named Abydos. Finding its
exact location has been a major challenge and could only be indirectly
constrained. Thanks to CONSERT measurements, it was finally possible to
bound it by an ellipse of approximately 16 x 160 meters. Complementary
analyses were performed at CNES-SONC allowing narrowing down the
location of Philae to an area of approximately 10 m radius based on
illumination conditions and times of contact between Orbiter and Lander
during operations. A more precise localization is however hampered by
the uncertainties affecting the present 3-dimensional reconstruction
(DTM) of the area, presently at the limit of the illuminated part of
the nucleus (Figure 1). Spotting Philae on the images of the nucleus
has been even more challenging. The highest resolution images of
the region of interest after Philae's landing were obtained by the
OSIRIS-NAC in mid-December 2014 at a distance of approximately 20 km,
the image scale implying that Philae would at best appear as a few
bright pixels. Bright "spots" are however ubiquitous on the surface of
the nucleus, from glittering rocks or from local icy patches [2]. After
meticulously scanning the region of interest, several candidates were
spotted but the ambiguity could only be removed when a pre-landing
image of the OSIRIS- NAC collection was identified whose geometric
conditions (illumination and viewing) were very similar to one of the
post-landing images of 12 December 2014. Although taken at different
spatial resolutions, all topographic details match, except for one
bright spot present on the post-landing image as shown in Figure 2. A
false detection or an artefact have been ruled out as this candidate
was successfully identified on other images taken in mid-December
(Figure 2). A local change in the surface is highly unlikely as no
activity has been detected on this presently poorly illuminated part
of the nucleus. The determined location is remarkably close to that
resulting from the indirect constraints, within approximately 10 m,
a further validation of the probable detection of Philae. In fact,
this solution satisfies all known constraints, taking into account
the present uncertainties affecting the DTM. The Abydos area appears
extremely rough with numerous rocks and boulders scattered around,
possibly resulting from the local degradation of the rim of the
Hatmehit depression. The roughness is confirmed by the large values
of the local slopes determined on the present DTM although they are
probably underestimated. It is further dramatically illustrated by
several anaglyphs constructed from all suitable NAC images of the
landing area, thus allowing a stereo view of the local relief.
---------------------------------------------------------
Title: The low strength of 67P: evidence for a primordial nucleus?
Authors: Groussin, O.; Jorda, L.; Auger, A. -T.; Kührt, E.; Gaskell,
R.; Capanna, C.; Scholten, F.; Preusker, F.; Lamy, P.; Hviid, S.;
Knollenberg, J.; Keller, U.; Huettig, C.; Romeuf, D.; Sierks, H.;
Osiris Team
2015EPSC...10...39G Altcode:
Rosetta is orbiting comet 67P/Churyumov- Gerasimenko since August
2014. The OSIRIS camera [1] onboard this spacecraft has acquired
hundreds of images of the nucleus surface, with a spatial resolution
down to the decimeter scale [2]. The images reveal a complex nucleus
surface made of smooth and hummocky terrains, covered partially or
entirely by dust or exposing a consolidated material, pits, cliffs and
fractures from the hundred meter scale to the decimeter scale [3]. The
nature and origin of these terrains and geomorphological features are
far from being understood but remain of paramount importance to better
constrain the formation and evolution scenario of the nucleus of 67P and
comets in general. This study focuses on the link between the nucleus
gravitational slopes and surface morphology, to provide constraints
on the nature of the cometary material and its mechanical properties
in particular (tensile strength, shear strength and compressive
strength). The derived strengths can also be used to constrain the
origin of the nucleus of 67P. We derive a low tensile strength for
the nucleus, typically from a few tens to a few hundreds Pa [4]. Our
results tend to favour a formation of comets by pebble accretion in a
region of higher concentration of particles like a vortice [5, 6, 7],
which implies a gentle formation process by accretion at low velocity on
the order of 1ms-1 or less. On the contrary, the hierarchical accretion
model with velocities up to 50ms-1 for particles larger than 1m [8],
or the collisional scenario between two large bodies of tens of km
or more with an internal compression by gravity larger than 10 kPa
[9], although not excluded, are less favored. This points towards a
primordial nucleus, which might have not been strongly affected by
collisions since its formation.
---------------------------------------------------------
Title: Meter-scale polygons on 67P/Churyumov-Gerasimenko as evidences
of near subsurface water ice
Authors: Auger, A. -T.; El-Maarry, M. R.; Groussin, O.; Capanna,
C.; Jorda, L.; Bouley, S.; Davidsson, B.; Deller, J.; Güttler, C.;
Hofmann, M.; Höfner, S.; Lamy, P. L.; Lazzarin, M.; Marchi, S.;
Thomas, N.; Vincent, J. -B.; Sierks, H.
2015EPSC...10..516A Altcode:
Since August 2014, high spatial resolution images of the nucleus of
67P/Churyumov-Gerasimenko have been acquired by the OSIRIS camera on
board the Rosetta spacecraft, enabling to identify meter-scale features
on the surface. Among them, we identify polygons with a size from 2
to 20 meters. We define the polygons on 67P as high-centered thermal
contraction polygons, which further evolve through preferential
sublimation along the cracks. This kind of polygons are known on
Earth and Mars as evidences of permanent water ice table in the near
subsurface [1,2,3].
---------------------------------------------------------
Title: Characterization of the Subsurface of
67P/Churyumov-Gerasimenko's Abydos Site
Authors: Brugger, B.; Mousis, O.; Morse, A.; Marboeuf, U.; Jorda, L.;
Andrews, D.; Barber, S.; Guilbert-Lepoutre, A.; Lamy, P.; Luspay-Kuti,
A.; Mandt, K.; Morgan, G.; Sheridan, S.; Vernazza, P.; Wright, I. P.
2015EPSC...10..206B Altcode:
We investigate the structure of the subsurface of the Abydos site
using a cometary nucleus model with parameters adapted to comet
67P/Churyumov- Gerasimenko and the Abydos landing site. We aim to
compare the production rates derived from our model with those of the
main molecules measured by Ptolemy. This will allow us to retrieve
the depths at which the different molecules still exist in solid form.
---------------------------------------------------------
Title: A Novel Technique for Measuring the Solar Radius from Eclipse
Light Curves - Results for 2010, 2012, 2013, and 2015
Authors: Lamy, Philippe; Prado, Jean-Yves; Floyd, Olivier; Rocher,
Patrick; Faury, Guillaume; Koutchmy, Serge
2015SoPh..290.2617L Altcode: 2015SoPh..tmp..170L
We report on a novel technique for measuring the solar radius during
total solar eclipses that exploits light curves recorded just before
and after second and third contacts. The measurements are performed by
pre-programmed photometers that are deployed over the eclipse paths and
are operated without supervision. The recorded light curves are compared
to synthetic light curves calculated from high-accuracy ephemerides
and lunar-limb profiles constructed from the topographic model of the
Moon provided by the Kaguya lunar space mission. A minimization process
between the two sets of curves yields the solar radius. Altogether,
seventeen determinations have been obtained during the past four total
eclipses with the following averages (at a wavelength of 540 nm and
scaled to 1 AU): 959.94 ±0.02 arcsec on 11 July 2010, 960.02 ±0.04
arcsec on 13 November 2012, 959.99 ±0.09 arcsec on 3 November 2013, and
960.01 ±0.09 arcsec on 20 March 2015. Part of the differences between
these four values may be attributed to weather conditions. Averaging
the whole set of measurements yields a radius of 959.99 ±0.06 arcsec
(696 ,246 ±45 km), which agrees excellently well with the most recent
data and supports an upward revision of the standard IAU value, as
previously suggested.
---------------------------------------------------------
Title: Design and modelisation of ASPIICS optics
Authors: Galy, C.; Fineschi, S.; Galano, D.; Howard, R. A.; Kintziger,
C.; Kirschner, V.; Koutchmy, S.; Lamy, P.; Mazzoli, A.; Melich, R.;
Mestreau-Garreau, A.; Renotte, E.; Servaye, J. S.; Stockman, Y.;
Thizy, C.; Zhukov, A.
2015SPIE.9604E..0BG Altcode:
In the framework of development of ASPIICS (Association of Spacecraft
for Polarimetric and Imaging Investigation of the Corona of the Sun),
the Centre Spatial de Liege is responsible of the optical design of
the coronagraph and the optics will be manufactured by TOPTEC. The
particularity of this coronagraph is to have an external occulter
located 150 m ahead of the first imaging lens. This external occulter
is re-imaged on an internal occulter which function is - as in a
classical externally occulted Lyot coronagraph - to block the sun
light diffracted by the external occulter and to reduce the straylight
on the detector. The selection of this configuration is driven by the
requirement to observe the corona as close as possible to the solar limb
(i.e. 1 R<SUB>Sun</SUB>) without imaging the limb itself. A requirement
of 1.08 R<SUB>Sun</SUB> is specified at optical design level to grant
1.2 R<SUB>sun</SUB> at instrument level. The coronograph instrument is
designed to have a field of view of 1.6° x 1.6° with a resolution of
less than 6 arcsec. Its performances are limited by diffraction in a
530 - 590 nm wavelength range. This paper presents the optical design
and demonstrates that by design the requirements are fulfilled within
the misalignment, manufacturing and thermo-elastic error contributions.
---------------------------------------------------------
Title: Design status of ASPIICS, an externally occulted coronagraph
for PROBA-3
Authors: Renotte, Etienne; Alia, Andres; Bemporad, Alessandro;
Bernier, Joseph; Bramanti, Cristina; Buckley, Steve; Capobianco,
Gerardo; Cernica, Ileana; Dániel, Vladimir; Darakchiev, Radoslav;
Darmetko, Marcin; Debaize, Arnaud; Denis, François; Desselle,
Richard; de Vos, Lieve; Dinescu, Adrian; Fineschi, Silvano;
Fleury-Frenette, Karl; Focardi, Mauro; Fumel, Aurélie; Galano,
Damien; Galy, Camille; Gillis, Jean-Marie; Górski, Tomasz; Graas,
Estelle; Graczyk, Rafał; Grochowski, Konrad; Halain, Jean-Philippe
A.; Hermans, Aline; Howard, Russ; Jackson, Carl; Janssen, Emmanuel;
Kasprzyk, Hubert; Kosiec, Jacek; Koutchmy, Serge; Kovačičinová,
Jana; Kranitis, Nektarios; Kurowski, Michał; Ładno, Michał; Lamy,
Philippe; Landini, Federico; Lapáček, Radek; Lédl, Vít.; Liebecq,
Sylvie; Loreggia, Davide; McGarvey, Brian; Massone, Giuseppe; Melich,
Radek; Mestreau-Garreau, Agnes; Mollet, Dominique; Mosdorf, Łukasz;
Mosdorf, Michał; Mroczkowski, Mateusz; Muller, Raluca; Nicolini,
Gianalfredo; Nicula, Bogdan; O'Neill, Kevin; Orleański, Piotr;
Palau, Marie-Catherine; Pancrazzi, Maurizio; Paschalis, Antonios;
Patočka, Karel; Peresty, Radek; Popescu, Irina; Psota, Pavel; Rataj,
Miroslaw; Rautakoski, Jan; Romoli, Marco; Rybecký, Roman; Salvador,
Lucas; Servaye, Jean-Sébastien; Solomon, Cornel; Stockman, Yvan;
Swat, Arkadiusz; Thizy, Cédric; Thomé, Michel; Tsinganos, Kanaris;
Van der Meulen, Jim; Van Vooren, Nico; Vit, Tomáš; Walczak, Tomasz;
Zarzycka, Alicja; Zender, Joe; Zhukov, Andrei
2015SPIE.9604E..0AR Altcode:
The "sonic region" of the Sun corona remains extremely difficult to
observe with spatial resolution and sensitivity sufficient to understand
the fine scale phenomena that govern the quiescent solar corona,
as well as phenomena that lead to coronal mass ejections (CMEs),
which influence space weather. Improvement on this front requires
eclipse-like conditions over long observation times. The space-borne
coronagraphs flown so far provided a continuous coverage of the external
parts of the corona but their over-occulting system did not permit to
analyse the part of the white-light corona where the main coronal mass
is concentrated. The proposed PROBA-3 Coronagraph System, also known
as ASPIICS (Association of Spacecraft for Polarimetric and Imaging
Investigation of the Corona of the Sun), with its novel design, will
be the first space coronagraph to cover the range of radial distances
between ~1.08 and 3 solar radii where the magnetic field plays a crucial
role in the coronal dynamics, thus providing continuous observational
conditions very close to those during a total solar eclipse. PROBA-3
is first a mission devoted to the in-orbit demonstration of precise
formation flying techniques and technologies for future European
missions, which will fly ASPIICS as primary payload. The instrument
is distributed over two satellites flying in formation (approx. 150m
apart) to form a giant coronagraph capable of producing a nearly perfect
eclipse allowing observing the sun corona closer to the rim than ever
before. The coronagraph instrument is developed by a large European
consortium including about 20 partners from 7 countries under the
auspices of the European Space Agency. This paper is reviewing the
recent improvements and design updates of the ASPIICS instrument as
it is stepping into the detailed design phase.
---------------------------------------------------------
Title: Mid-Term Quasi-Periodicities and Solar Cycle Variation of
the White-Light Corona from 18.5 Years (1996.0 - 2014.5) of LASCO
Observations
Authors: Barlyaeva, T.; Lamy, P.; Llebaria, A.
2015SoPh..290.2117B Altcode: 2015SoPh..tmp..106B
We report on the analysis of the temporal evolution of the solar corona
based on 18.5 years (1996.0 - 2014.5) of white-light observations
with the SOHO/LASCO-C2 coronagraph. This evolution is quantified by
generating spatially integrated values of the K-corona radiance, first
globally, then in latitudinal sectors. The analysis considers time
series of monthly values and 13-month running means of the radiance
as well as several indices and proxies of solar activity. We study
correlation, wavelet time-frequency spectra, and cross-coherence and
phase spectra between these quantities. Our results give a detailed
insight on how the corona responds to solar activity over timescales
ranging from mid-term quasi-periodicities (also known as quasi-biennial
oscillations or QBOs) to the long-term 11 year solar cycle. The
amplitude of the variation between successive solar maxima and minima
(modulation factor) very much depends upon the strength of the cycle
and upon the heliographic latitude. An asymmetry is observed during the
ascending phase of Solar Cycle 24, prominently in the royal and polar
sectors, with north leading. Most prominent QBOs are a quasi-annual
period during the maximum phase of Solar Cycle 23 and a shorter period,
seven to eight months, in the ascending and maximum phases of Solar
Cycle 24. They share the same properties as the solar QBOs: variable
periodicity, intermittency, asymmetric development in the northern and
southern solar hemispheres, and largest amplitudes during the maximum
phase of solar cycles. The strongest correlation of the temporal
variations of the coronal radiance - and consequently the coronal
electron density - is found with the total magnetic flux. Considering
that the morphology of the solar corona is also directly controlled by
the topology of the magnetic field, this correlation reinforces the
view that they are intimately connected, including their variability
at all timescales.
---------------------------------------------------------
Title: Large heterogeneities in comet 67P as revealed by active pits
from sinkhole collapse
Authors: Vincent, Jean-Baptiste; Bodewits, Dennis; Besse, Sébastien;
Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael;
Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica;
A'Hearn, Michael F.; Auger, Anne-Thérèse; Barucci, M. Antonella;
Bertaux, Jean-Loup; Bertini, Ivano; Capanna, Claire; Cremonese,
Gabriele; da Deppo, Vania; Davidsson, Björn; Debei, Stefano; de Cecco,
Mariolino; El-Maarry, Mohamed Ramy; Ferri, Francesca; Fornasier, Sonia;
Fulle, Marco; Gaskell, Robert; Giacomini, Lorenza; Groussin, Olivier;
Guilbert-Lepoutre, Aurélie; Gutierrez-Marques, P.; Gutiérrez, Pedro
J.; Güttler, Carsten; Hoekzema, Nick; Höfner, Sebastian; Hviid,
Stubbe F.; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kovacs,
Gabor; Kramm, Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia,
Fiorangela; Lara, Luisa M.; Lazzarin, Monica; Lee, Vicky; Leyrat,
Cédric; Lin, Zhong-Yi; Lopez Moreno, Josè J.; Lowry, Stephen; Magrin,
Sara; Maquet, Lucie; Marchi, Simone; Marzari, Francesco; Massironi,
Matteo; Michalik, Harald; Moissl, Richard; Mottola, Stefano; Naletto,
Giampiero; Oklay, Nilda; Pajola, Maurizio; Preusker, Frank; Scholten,
Frank; Thomas, Nicolas; Toth, Imre; Tubiana, Cecilia
2015Natur.523...63V Altcode:
Pits have been observed on many cometary nuclei mapped by
spacecraft. It has been argued that cometary pits are a signature
of endogenic activity, rather than impact craters such as those
on planetary and asteroid surfaces. Impact experiments and models
cannot reproduce the shapes of most of the observed cometary pits,
and the predicted collision rates imply that few of the pits are
related to impacts. Alternative mechanisms like explosive activity
have been suggested, but the driving process remains unknown. Here
we report that pits on comet 67P/Churyumov-Gerasimenko are active,
and probably created by a sinkhole process, possibly accompanied
by outbursts. We argue that after formation, pits expand slowly in
diameter, owing to sublimation-driven retreat of the walls. Therefore,
pits characterize how eroded the surface is: a fresh cometary surface
will have a ragged structure with many pits, while an evolved surface
will look smoother. The size and spatial distribution of pits imply
that large heterogeneities exist in the physical, structural or
compositional properties of the first few hundred metres below the
current nucleus surface.
---------------------------------------------------------
Title: Fractures on comet 67P/Churyumov-Gerasimenko observed by
Rosetta/OSIRIS
Authors: El-Maarry, M. R.; Thomas, N.; Gracia-Berná, A.; Marschall,
R.; Auger, A. -T.; Groussin, O.; Mottola, S.; Pajola, M.; Massironi,
M.; Marchi, S.; Höfner, S.; Preusker, F.; Scholten, F.; Jorda, L.;
Kührt, E.; Keller, H. U.; Sierks, H.; A'Hearn, M. F.; Barbieri, C.;
Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo,
V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Güttler, C.;
Fornasier, S.; Fulle, M.; Gutierrez, P. J.; Hofmann, M.; Hviid, S. F.;
Ip, W. -H.; Knollenberg, J.; Koschny, D.; Kovacs, G.; Kramm, J. -R.;
Küppers, M.; Lamy, P. L.; Lara, L. M.; Lazzarin, M.; Lopez Moreno,
J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Oklay, N.; Pommerol,
A.; Rickman, H.; Rodrigo, R.; Tubiana, C.; Vincent, J. -B.
2015GeoRL..42.5170E Altcode:
The Optical, Spectroscopic, and Infrared Remote Imaging System
(OSIRIS) experiment onboard the Rosetta spacecraft currently orbiting
comet 67P/Churyumov-Gerasimenko has yielded unprecedented views
of a comet's nucleus. We present here the first ever observations
of meter-scale fractures on the surface of a comet. Some of these
fractures form polygonal networks. We present an initial assessment of
their morphology, topology, and regional distribution. Fractures are
ubiquitous on the surface of the comet's nucleus. Furthermore, they
occur in various settings and show different topologies suggesting
numerous formation mechanisms, which include thermal insulation
weathering, orbital-induced stresses, and possibly seasonal thermal
contraction. However, we conclude that thermal insolation weathering
is responsible for creating most of the observed fractures based on
their morphology and setting in addition to thermal models that indicate
diurnal temperature ranges exceeding 200 K and thermal gradients of ~15
K/min at perihelion are possible. Finally, we suggest that fractures
could be a facilitator in surface evolution and long-term erosion.
---------------------------------------------------------
Title: GIADA on-board Rosetta: comet 67P/C-G dust coma
characterization
Authors: Rotundi, Alessandra; Della Corte, Vincenzo; Fulle, Marco;
Sordini, Roberto; Ivanovski, Stavro; Accolla, Mario; Ferrari, Marco;
Lucarelli, Francesca; Zakharov, Vladimir; Mazzotta Epifani, Elena;
López-Moreno, José J.; Rodríguez, Julio; Colangeli, Luigi; Palumbo,
Pasquale; Bussoletti, Ezio; Crifo, Jean-Francois; Esposito, Francesca;
Green, Simon F.; Grün, Eberhard; Lamy, Philippe L.
2015EGUGA..1713156R Altcode:
21ESA-ESAC, Camino Bajo del Castillo, s/n., Urb. Villafranca del
Castillo, 28692 Villanueva de la Cañada, Madrid, Spagna GIADA
consists of three subsystems: 1) the Grain Detection System (GDS)
to detect dust grains as they pass through a laser curtain, 2)
the Impact Sensor (IS) to measure grain momentum derived from the
impact on a plate connected to five piezoelectric sensors, and 3)
the MicroBalances System (MBS); five quartz crystal microbalances in
roughly orthogonal directions providing the cumulative dust flux of
grains smaller than 10 microns. GDS provides data on grain speed and its
optical cross section. The IS grain momentum measurement, when combined
with the GDS detection time, provides a direct measurement of grain
speed and mass. These combined measurements characterize single grain
dust dynamics in the coma of 67P/CG. No prior in situ dust dynamical
measurements at these close distances from the nucleus and starting from
such high heliocentric distances are available up to date. We present
here the results obtained by GIADA, which began operating in continuous
mode on 18 July 2014 when the comet was at a heliocentric distance of
3.7 AU. The first grain detection occurred when the spacecraft was
814 km from the nucleus on 1 August 2014. From August the 1st up to
December the 11th, GIADA detected more than 800 grains, for which the
3D spatial distribution was determined. About 700 out of 800 are GDS
only detections: "dust clouds", i.e. slow dust grains (≈ 0.5 m/s)
crossing the laser curtain very close in time (e.g. 129 grains in 11
s), probably fluffy grains. IS only detections are about 70, i.e. ≈
1/10 of the GDS only. This ratio is quite different from what we got
for the early detections (August - September) when the ration was ≈
3, suggesting the presence of different types of particle (bigger,
brighter, less dense).The combined GDS+IS detections, i.e. measured by
both the GDS and IS detectors, are about 70 and allowed us to extract
the complete set of dust grain parameters, i.e., mass, speed, and
geometrical cross-section. These detections allowed us to constraint the
grain density. The GIADA detections type was studied as a function of
the observational geometrical configuration. Acknowledgments: GIADA was
built by a consortium led by the Univ. Napoli "Parthenope" & INAF-
Oss. Astr. Capodimonte, in collaboration with the Inst. de Astrofisica
de Andalucia, Selex-ES, FI and SENER. GIADA is presently managed
& operated by Ist. di Astrofisica e Planetologia Spaziali-INAF,
IT. GIADA was funded and managed by the Agenzia Spaziale Italiana,
IT, with the support of the Spanish Ministry of Education and Science
MEC, ES. GIADA was developed from a PI proposal from the University
of Kent; sci. & tech. contribution were provided by CISAS, IT,
Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We
thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their
outstanding work. Science support provided was by NASA through the US
Rosetta Project managed by the Jet Propulsion Laboratory/California
Institute of Technology. GIADA calibrated data will be available through
ESA's PSA web site (www.rssd.esa.int/index.php?project=PSA&page=in
dex). We would like to thank Angioletta Coradini for her contribution
as a GIADA Co-I.
---------------------------------------------------------
Title: Rosetta/OSIRIS - Nucleus morphology and activity of comet
67P/Churyumov-Gerasimenko
Authors: Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rickman,
Hans; Rodrigo, Rafael; Koschny, Detlef
2015EGUGA..1712760S Altcode:
ESA's Rosetta mission arrived on August 6, 2014, at target comet
67P/Churyumov-Gerasimenko after 10 years of cruise. OSIRIS (Optical,
Spectroscopic, and Infrared Remote Imaging System) is the scientific
imaging system onboard Rosetta. It comprises a Narrow Angle Camera
(NAC) for nucleus surface and dust studies and a Wide Angle Camera
(WAC) for the wide field coma investigations. OSIRIS imaged the nucleus
and coma of the comet from the arrival throughout the mapping phase,
PHILAE landing, early escort phase and close fly-by. The overview paper
will discuss the surface morpholo-gy and activity of the nucleus as
seen in gas, dust, and local jets as well as small scale structures
in the local topography.
---------------------------------------------------------
Title: Morphology of the nucleus of Comet 67P/Churyumov-Gerasimenko
from stereo and high spatial resolution OSIRIS-NAC images
Authors: Lamy, Philippe; Groussin, Olivier; Romeuf, David; Thomas,
Nicolas; Auger, Anne-Thérèse; Jorda, Laurent; Gaskell, Robert;
Capanna, Claire; Llebaria, Antoine
2015EGUGA..17.8338L Altcode:
The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA's
Rosetta spacecraft has acquired images of the surface of the nucleus
of comet 67P/Churyumov-Gerasimenko at scales down to 0.2 m/pixel. We
employ a variety of techniques to characterize its morphology. Digital
terrain modeling (DTM), indispensable for quantitative morphological
analysis is performed using stereophotoclinometry (SPC). Depending upon
the observational coverage, the resolution of the DTMs exceed 1 m in the
most favorable cases. The ultimate stereographic analysis is performed
by exploiting pairs of images able to produce anaglyphs whose spatial
resolution surpasses that of the DTMs. Digital image filtering and
contrast enhancement techniques are applied on the original images as
appropriate. We first concentrate on the dust covered terrains possibly
resulting from airfall deposits, on the quasi-circular depressions or
basins possibly connected to collapses of the underground terrain,
and on large scarps that suggest extensive mass disruption. We pay
special attention to lithologies that may give clues to the subsurface
structure of the nucleus. Our ultimate goal is to understand the
processes at work on the nucleus, directly or indirectly connected to
its activity as there appears to a variety of processes far beyond what
was classicaly considered in the past, for instance airfall deposits,
surface dust transport, mass wasting, and insolation weathering.
---------------------------------------------------------
Title: A New 3D Shape Reconstruction Method for celestial bodies:
Multi-Resolution Stereophotoclinometry by Deformation
Authors: Capanna, Claire; Jorda, Laurent; Gesquière, Gilles; Groussin,
Olivier; Gutiérrez, Pedro; Hviid, Stubbe; Lamy, Philippe; Rodionov,
Sergey; Vibert, Didier
2015EGUGA..17.5343C Altcode:
In astrophysics, direct measures on celestial bodies are not always
feasible. 3D shape models allow to overcome this kind of problem. We
thus developed a new 3D shape reconstruction method which combines
stereo, photoclinometry and the deformation of a triangular mesh
describing the surface of the object. The method deforms the mesh -
initially a sphere - until the set of synthetic images, created from the
mesh (Jorda et al., SPIE 2010) match the observed one. Stereo control
points can be used as a constraint in the deformation of the mesh,
but it is not required at low resolutions. This new technique has been
applied to images of the nucleus of comet 67P/Churyumov-Gerasimenko
acquired by the OSIRIS instrument aboard the Rosetta spacecraft. It
allowed to reconstruct the shape of the nucleus and to retrieve its
rotational parameters from low-resolution images obtained with the
narrow-angle camera of OSIRIS in mid-July 2014, when stereo-based
techniques were still inapplicable. The technique has also been applied
to higher-resolution images of the nucleus later on, using the stereo
information as a constraint.
---------------------------------------------------------
Title: Monitoring Comet 67P/C-G Micrometer Dust Flux: GIADA onboard
Rosetta.
Authors: Della Corte, Vincenzo; Rotundi, Alessandra; Ivanovski,
Stavro; Accolla, Mario; Ferrari, Marco; Sordini, Roberto; Lucarelli,
Francesca; Zakharov, Vladimir; Fulle, Marco; Mazzotta Epifani, Elena;
López-Moreno, José J.; Rodríguez, Julio; Colangeli, Luigi; Palumbo,
Pasquale; Bussoletti, Ezio; Crifo, Jean-Francois; Esposito, Francesca;
Green, Simon F.; Grün, Eberhard; Lamy, Philippe L.
2015EGUGA..17.6559D Altcode:
(21)ESA-ESAC, Camino Bajo del Castillo, s/n., Urb. Villafranca
del Castillo, 28692 Villanueva de la Cañada, Madrid, Spagna The
MicroBalance System (MBS) is one of the three measurement subsystems
of GIADA, the Grain Impact Analyzer and Dust Accumulator on board
the Rosetta/ESA spacecraft (S/C). It consists of five Quartz Crystal
Microbalances (QCMs) in roughly orthogonal directions providing
the cumulative dust flux of grains smaller than 10 microns. The MBS
is continuously monitoring comet 67P/CG since the beginning of May
2014. During the first 4 months of measurements, before the insertion
of the S/C in the bound orbit phase, there were no evidences of dust
accumulation on the QCMs. Starting from the beginning of October,
three out of five QCMs measured an increase of the deposited dust. The
measured fluxes show, as expected, a strong anisotropy. In particular,
the dust flux appears to be much higher from the Sun direction with
respect to the comet direction. Acknowledgment: GIADA was built
by a consortum led by the Univ. Napoli "Parthenope" & INAF-
Oss. Astr. Capodimonte, in collaboration with the Inst. de Astrofisica
de Andalucia, Selex-ES, FI and SENER. GIADA is presently managed
& operated by Ist. di Astrofisica e Planetologia Spaziali-INAF,
IT. GIADA was funded and managed by the Agenzia Spaziale Italiana,
IT, with the support of the Spanish Ministry of Education and Science
MEC, ES. GIADA was developed from a PI proposal from the University
of Kent; sci. & tech. contribution were provided by CISAS, IT,
Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We
thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their
out-standing work. Science support provided was by NASA through the US
Rosetta Project managed by the Jet Propulsion Laboratory/ California
Institute of Technology. GIADA calibrated data will be available through
ESA's PSA web site (www.rssd.esa.int/index.php? project=PSA&page=in
dex). We would like to thank Angioletta Coradini for her contribution
as a GIADA Co-I.
---------------------------------------------------------
Title: Dust Measurements in the Coma of Comet
67P/Churyumov-Gerasimenko Inbound to the Sun Between 3.7 and 3.4 AU
Authors: Rotundi, Alessandra; Della Corte, Vincenzo; Fulle, Marco;
Ferrari, Marco; Sordini, Roberto; Ivanovski, Stavro; Accolla, Mario;
Lucarelli, Francesca; Zakharov, Vladimir; Mazzotta Epifani, Elena;
López-Moreno, José J.; Rodríguez, Julio; Colangeli, Luigi; Palumbo,
Pasquale; Bussoletti, Ezio; Crifo, Jean-Francois; Esposito, Francesca;
Green, Simon F.; Grün, Eberhard; Lamy, Philippe L.
2015EGUGA..1712907R Altcode:
(21) ESA-ESAC, Camino Bajo del Castillo, s/n., Urb. Villafranca del
Castillo, 28692 Villanueva de la Cañada, Madrid, Spagna, (22) Max
Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3,
37077 Göttingen, Germany, (23) Center of Studies and Activities
for Space (CISAS), University of Padova, I-35131 Padova, Italy,
(24) Department of Physics and Astronomy, University of Padova,
I-35131 Padova, Italy Comets are the most primitive bodies in the
solar system. They retain a cosmo-chemical record of conditions in
the solar nebula when the planets were forming, 4.5 billion years
ago. While accurate measurements of the gas loss rate from comets are
possible under favorable conditions even from Earth, estimates of the
dust loss rate so far have been much more uncertain. Multi-parametric
models are needed to extract global dust parameters from the dust
features of comets (e.g. coma, tails and trails) observed from
ground and Earth orbiting telescopes, and it is often difficult to
establish the uniqueness of these model results. Critical measurements
for understanding the process of accretion and the refractory to
volatiles ratio in the solar nebula are being obtained by the Grain
Impact Analyzer and Dust Accumulator (GIADA) experiment onboard ESA's
Rosetta spacecraft, now orbiting comet 67P/Churyumov-Gerasimenko
(67P/CG). GIADA measures the mass, momentum and velocity of individual
grains, providing the dust loss rate over three orders of magnitude in
mass for grains from tens to hundreds of microns in diameter. GIADA
consists of three subsystems: 1) the Grain Detection System (GDS) to
detect dust grains as they pass through a laser curtain, 2) the Impact
Sensor (IS) to measure grain momentum derived from the impact on a
plate connected to five piezoelectric sensors, and 3) the Mi-croBalances
System (MBS); five quartz crystal microbalances in roughly orthogonal
directions providing the cumu-lative dust flux of grains smaller
than 10 microns. GDS provides data on grain speed and its optical
cross section. The IS grain momentum measurement, when combined with
the GDS detection time, provides a direct measurement of grain speed
and mass. These combined measurements characterize single grain dust
dynamics in the coma of 67P/CG. The first grain was detected on 1 August
2014 at 814 km from the comet nucleus. Between then and 13 Septem-ber
2014 GIADA detected 35 grains ranging in mass from ~ 5 x 10-10 to 8
x 10-8 kg. Including complementary data from the OSIRIS narrow angle
camera, the dust mass loss was calculated over an additional three
orders of magni-tude in mass, extending the ejected dust grain sizes up
to 2 cm. Combined with data from the MIRO and the ROSINA instruments
onboard Rosetta we find a dust/gas mass ratio of 4 +/- 2 averaged
over the sunlit nucleus sur-face. The dust to gas ratio may change
as the comet approaches closer to the Sun. Acknowledgments: GIADA was
built by a consortium led by the Univ. Napoli "Parthenope" & INAF-
Oss. Astr. Capodimonte, in collabo-ration with the Inst. de Astrofisica
de Andalucia, Selex-ES, FI and SENER. GIADA is presently managed
& operated by Ist. di Astrofisica e Planetologia Spaziali-INAF,
IT. GIADA was funded and managed by the Agenzia Spaziale Italiana,
IT, with the support of the Spanish Ministry of Education and Science
MEC, ES. GIADA was developed from a PI proposal from the University
of Kent; sci. & tech. contribution were pro-vided by CISAS, IT,
Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We
thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their
outstanding work. Science support provided was by NASA through the US
Rosetta Project managed by the Jet Propulsion Laboratory/California
Institute of Technology. GIADA calibrated data will be available through
ESA's PSA web site(www.rssd.esa.int/index.php?project=PSA&page=in
dex). We would like to thank Angioletta Coradini for her contribution
as a GIADA Co-I. We thank the MIRO, OSIRIS and ROSINA teams for sharing
their early results with us.
---------------------------------------------------------
Title: Low and High Albedo Jovian Trojans and Hildas: A Similar or
Different Origin?
Authors: Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan,
M.; Lamy, P.; Binzel, R. P.
2015LPI....46.1860M Altcode: 2015LPICo1832.1860M
We report the first spectroscopic characterization of a sample of high
albedo Trojans and Hildas.
---------------------------------------------------------
Title: Dust Measurements in the Coma of Comet
67P/Churyumov-Gerasimenko Inbound to the Sun Between 3.7 and 3.4 AU
Authors: Fulle, M.; Della Corte, V.; Rotundi, A.; Accolla, M.;
Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Sordini, R.; Zakharov, V.;
Mazzotta Epifani, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Colangeli,
L.; Palumbo, P.; Bussoletti, E.; Crifo, J.; Esposito, F.; Green,
S. F.; Gruen, E.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.;
Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.;
Perrin, J.; Rodrigo, R.; Weissman, P.; Zarnecki, J. C.; Cosi, M.;
Giovane, F.; Gustafson, B.; Herranz, M. L.; Jeronimo, J. M.; Leese,
M. R.; Lopez-Jimenez, A. C.; Altobelli, N.; Sierks, H.; Agarwal, J.;
Bertini, I.; Fornasier, S.; Gutierrez, P. J.; Lara, L.; Guettler, C.;
Marzari, F.; Oaklay, N.; Snodgrass, C.; Tubiana, C.; Vincenzo, J. B.
2015LPI....46.2420F Altcode: 2015LPICo1832.2420F
GIADA and OSIRIS dust data, combined with data from MIRO and ROSINA
instruments onboard Rosetta, from 3.7 to 3.4 AU inbound provide a
dust/gas ratio of 4 ± 2.
---------------------------------------------------------
Title: The Geomorphology of Comet 67P: Implications for the Past
Collisional Evolution and Formation
Authors: Marchi, S.; Rickman, H.; Massironi, M.; Marzari, F.; El-Maari,
M. R.; Besse, S.; Thomas, N.; Barbieri, C.; Barucci, M. A.; Fornasier,
S.; Giacomini, L.; Keller, H. U.; Kuehrt, E.; Lamy, P.; Lazzarin,
M.; Mottola, S.; Naletto, G.; Pajola, M.; Sierks, H.
2015LPI....46.1532M Altcode: 2015LPICo1832.1532M
OSIRIS camera onboard Rosetta showed Comet 67P complex surface,
characterized by fractures and layering. We discuss their implications
for 67P formation.
---------------------------------------------------------
Title: Density and Charge of Pristine Fluffy Particles from Comet
67P/Churyumov-Gerasimenko
Authors: Fulle, M.; Della Corte, V.; Rotundi, A.; Weissman, P.; Juhasz,
A.; Szego, K.; Sordini, R.; Ferrari, M.; Ivanovski, S.; Lucarelli,
F.; Accolla, M.; Merouane, S.; Zakharov, V.; Mazzotta Epifani, E.;
López-Moreno, J. J.; Rodríguez, J.; Colangeli, L.; Palumbo, P.;
Grün, E.; Hilchenbach, M.; Bussoletti, E.; Esposito, F.; Green,
S. F.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.;
Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Rodrigo, R.;
Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.;
Jerónimo, J. M.; Leese, M. R.; López-Jiménez, A. C.; Altobelli, N.
2015ApJ...802L..12F Altcode:
The Grain Impact Analyzer and Dust Accumulator (GIADA) instrument on
board ESA’s Rosetta mission is constraining the origin of the dust
particles detected within the coma of comet 67 P/Churyumov-Gerasimenko
(67P). The collected particles belong to two families: (i) compact
particles (ranging in size from 0.03 to 1 mm), witnessing the presence
of materials that underwent processing within the solar nebula and (ii)
fluffy aggregates (ranging in size from 0.2 to 2.5 mm) of sub-micron
grains that may be a record of a primitive component, probably linked to
interstellar dust. The dynamics of the fluffy aggregates constrain their
equivalent bulk density to \lt 1 kg m<SUP>-3</SUP>. These aggregates
are charged, fragmented, and decelerated by the spacecraft negative
potential and enter GIADA in showers of fragments at speeds \lt 1
m s<SUP>-1</SUP>. The density of such optically thick aggregates
is consistent with the low bulk density of the nucleus. The mass
contribution of the fluffy aggregates to the refractory component of
the nucleus is negligible and their coma brightness contribution is
less than 15%.
---------------------------------------------------------
Title: Properties of craters on the Achaia region of Asteroid
(21) Lutetia
Authors: Auger, A. -T.; Bouley, S.; Jorda, L.; Groussin, O.; Lamy,
P. L.; Baratoux, D.
2015Icar..247..137A Altcode:
We report on the physical properties of the craters of Achaia region
of the main-belt Asteroid (21) Lutetia, based on images obtained with
the OSIRIS instrument during the Rosetta flyby that took place on 10
July 2010. Images of the surface were acquired with its Narrow Angle
Camera, from which Digital Terrain Models (DTM) of the surface were
constructed. These DTMs give access to the geometrical properties of
the craters of the asteroid. On a complex asteroid shape, slopes and
depth-to-diameter ratios (d/D) of craters should be carefully measured
taking into account the local topography to obtain a value that is
physically related to the work of forces resisting to mass displacement
(associated with gravity and/or material strength) occurring in either
excavation or degradation processes. We present new measurements
of d/D and internal slopes of impact craters of the Achaia region,
which offers optimal conditions of observations and a large population
of craters. We find that d/D values for Achaia craters differ from
previous works on Lutetia and are consistent with the values found on
other asteroids such as (243) Ida or (951) Gaspra. The Achaia region
may be divided into three units based on geomorphological analysis. The
mean d/D values of the three units are different, revealing differences
in resurfacing history by impact-related ejecta blanketing and seismic
shaking. Some of these geological events may be recent compared to the
age of the region since several lineaments intersect most craters of
one of the three units. Independent evidence for ejecta blanket have
been given for the unit associated with low d/D values confirming
the contribution of this process to crater modification. Moreover, we
suggest that displacements along faults identified as surface lineaments
may have been responsible for the erasure of small craters. Our results
are finally integrated into a chronology sequence of events explaining
the present characteristics of the Achaia region.
---------------------------------------------------------
Title: 67P/Churyumov-Gerasimenko: Activity between March and June
2014 as observed from Rosetta/OSIRIS
Authors: Tubiana, C.; Snodgrass, C.; Bertini, I.; Mottola, S.; Vincent,
J. -B.; Lara, L.; Fornasier, S.; Knollenberg, J.; Thomas, N.; Fulle,
M.; Agarwal, J.; Bodewits, D.; Ferri, F.; Güttler, C.; Gutierrez,
P. J.; La Forgia, F.; Lowry, S.; Magrin, S.; Oklay, N.; Pajola, M.;
Rodrigo, R.; Sierks, H.; A'Hearn, M. F.; Angrilli, F.; Barbieri,
C.; Barucci, M. A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.;
Davidsson, B.; De Cecco, M.; Debei, S.; Groussin, O.; Hviid, S. F.;
Ip, W.; Jorda, L.; Keller, H. U.; Koschny, D.; Kramm, R.; Kührt, E.;
Küppers, M.; Lazzarin, M.; Lamy, P. L.; Lopez Moreno, J. J.; Marzari,
F.; Michalik, H.; Naletto, G.; Rickman, H.; Sabau, L.; Wenzel, K. -P.
2015A&A...573A..62T Altcode:
<BR /> Aims: 67P/Churyumov-Gerasimenko is the target comet of the
ESA's Rosetta mission. After commissioning at the end of March 2014,
the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS)
onboard Rosetta, started imaging the comet and its dust environment to
investigate how they change and evolve while approaching the Sun. <BR />
Methods: We focused our work on Narrow Angle Camera (NAC) orange images
and Wide Angle Camera (WAC) red and visible-610 images acquired between
2014 March 23 and June 24 when the nucleus of 67P was unresolved and
moving from approximately 4.3 AU to 3.8 AU inbound. During this period
the 67P - Rosetta distance decreased from 5 million to 120 thousand
km. <BR /> Results: Through aperture photometry, we investigated
how the comet brightness varies with heliocentric distance. 67P was
likely already weakly active at the end of March 2014, with excess
flux above that expected for the nucleus. The comet's brightness was
mostly constant during the three months of approach observations,
apart from one outburst that occurred around April 30 and a second
increase in flux after June 20. Coma was resolved in the profiles from
mid-April. Analysis of the coma morphology suggests that most of the
activity comes from a source towards the celestial north pole of the
comet, but the outburst that occurred on April 30 released material
in a different direction.
---------------------------------------------------------
Title: The morphological diversity of comet 67P/Churyumov-Gerasimenko
Authors: Thomas, Nicolas; Sierks, Holger; Barbieri, Cesare; Lamy,
Philippe L.; Rodrigo, Rafael; Rickman, Hans; Koschny, Detlef; Keller,
Horst Uwe; Agarwal, Jessica; A'Hearn, Michael F.; Angrilli, Francesco;
Auger, Anne-Therese; Barucci, M. Antonella; Bertaux, Jean-Loup;
Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis; Cremonese,
Gabriele; Da Deppo, Vania; Davidsson, Björn; De Cecco, Mariolino;
Debei, Stefano; El-Maarry, Mohamed Ramy; Ferri, Francesca; Fornasier,
Sonia; Fulle, Marco; Giacomini, Lorenza; Groussin, Olivier; Gutierrez,
Pedro J.; Güttler, Carsten; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda,
Laurent; Knollenberg, Jörg; Kramm, J. -Rainer; Kührt, Ekkehard;
Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M.; Lazzarin,
Monica; Moreno, Josè J. Lopez; Magrin, Sara; Marchi, Simone;
Marzari, Francesco; Massironi, Matteo; Michalik, Harald; Moissl,
Richard; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Pajola,
Maurizio; Pommerol, Antoine; Preusker, Frank; Sabau, Lola; Scholten,
Frank; Snodgrass, Colin; Tubiana, Cecilia; Vincent, Jean-Baptiste;
Wenzel, Klaus-Peter
2015Sci...347a0440T Altcode: 2015Sci...347.0440T
Images of comet 67P/Churyumov-Gerasimenko acquired by the OSIRIS
(Optical, Spectroscopic and Infrared Remote Imaging System) imaging
system onboard the European Space Agency’s Rosetta spacecraft at
scales of better than 0.8 meter per pixel show a wide variety of
different structures and textures. The data show the importance
of airfall, surface dust transport, mass wasting, and insolation
weathering for cometary surface evolution, and they offer some support
for subsurface fluidization models and mass loss through the ejection
of large chunks of material.
---------------------------------------------------------
Title: Dust measurements in the coma of comet
67P/Churyumov-Gerasimenko inbound to the Sun
Authors: Rotundi, Alessandra; Sierks, Holger; Della Corte, Vincenzo;
Fulle, Marco; Gutierrez, Pedro J.; Lara, Luisa; Barbieri, Cesare;
Lamy, Philippe L.; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans;
Keller, Horst Uwe; López-Moreno, José J.; Accolla, Mario; Agarwal,
Jessica; A'Hearn, Michael F.; Altobelli, Nicolas; Angrilli, Francesco;
Barucci, M. Antonietta; Bertaux, Jean-Loup; Bertini, Ivano; Bodewits,
Dennis; Bussoletti, Ezio; Colangeli, Luigi; Cosi, Massimo; Cremonese,
Gabriele; Crifo, Jean-Francois; Da Deppo, Vania; Davidsson, Björn;
Debei, Stefano; De Cecco, Mariolino; Esposito, Francesca; Ferrari,
Marco; Fornasier, Sonia; Giovane, Frank; Gustafson, Bo; Green,
Simon F.; Groussin, Olivier; Grün, Eberhard; Güttler, Carsten;
Herranz, Miguel L.; Hviid, Stubbe F.; Ip, Wing; Ivanovski, Stavro;
Jerónimo, José M.; Jorda, Laurent; Knollenberg, Joerg; Kramm, Rainer;
Kührt, Ekkehard; Küppers, Michael; Lazzarin, Monica; Leese, Mark R.;
López-Jiménez, Antonio C.; Lucarelli, Francesca; Lowry, Stephen C.;
Marzari, Francesco; Epifani, Elena Mazzotta; McDonnell, J. Anthony M.;
Mennella, Vito; Michalik, Harald; Molina, Antonio; Morales, Rafael;
Moreno, Fernando; Mottola, Stefano; Naletto, Giampiero; Oklay,
Nilda; Ortiz, José L.; Palomba, Ernesto; Palumbo, Pasquale; Perrin,
Jean-Marie; Rodríguez, Julio; Sabau, Lola; Snodgrass, Colin; Sordini,
Roberto; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste;
Weissman, Paul; Wenzel, Klaus-Peter; Zakharov, Vladimir; Zarnecki,
John C.
2015Sci...347a3905R Altcode: 2015Sci...347.3905R
Critical measurements for understanding accretion and the dust/gas
ratio in the solar nebula, where planets were forming 4.5 billion
years ago, are being obtained by the GIADA (Grain Impact Analyser
and Dust Accumulator) experiment on the European Space Agency’s
Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between
3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical,
Spectroscopic, and Infrared Remote Imaging System) detected 35
outflowing grains of mass 10<SUP>-10</SUP> to 10<SUP>-7</SUP> kilograms,
and 48 grains of mass 10<SUP>-5</SUP> to 10<SUP>-2</SUP> kilograms,
respectively. Combined with gas data from the MIRO (Microwave Instrument
for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for
Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio
of 4 ± 2 averaged over the sunlit nucleus surface. A cloud of larger
grains also encircles the nucleus in bound orbits from the previous
perihelion. The largest orbiting clumps are meter-sized, confirming
the dust/gas ratio of 3 inferred at perihelion from models of dust
comae and trails.
---------------------------------------------------------
Title: Probing the Solar Wind Acceleration Region with the Sun-grazing
Comet C/2002 S2
Authors: Giordano, S.; Raymond, J. C.; Lamy, P.; Uzzo, M.; Dobrzycka,
D.
2015ApJ...798...47G Altcode: 2014arXiv1411.1300G
Comet C/2002 S2, a member of the Kreutz family of sungrazing comets, was
discovered in white-light images of the Large Angle and Spectromeric
Coronagraph Experiment coronagraph on the Solar and Heliospheric
Observatory (SOHO) on 2002 September 18 and observed in H I Lyα
emission by the SOHO Ultraviolet Coronagraph Spectrometer (UVCS)
instrument at four different heights as it approached the Sun. The H
I Lyα line profiles detected by UVCS are analyzed to determine the
spectral parameters: line intensity, width, and Doppler shift with
respect to the coronal background. Two-dimensional comet images of
these parameters are reconstructed at the different heights. A novel
aspect of the observations of this sungrazing comet data is that,
whereas the emission from most of the tail is blueshifted, that along
one edge of the tail is redshifted. We attribute these shifts to a
combination of solar wind speed and interaction with the magnetic
field. In order to use the comet to probe the density, temperature,
and speed of the corona and solar wind through which it passes, as
well as to determine the outgassing rate of the comet, we develop a
Monte Carlo simulation of the H I Lyα emission of a comet moving
through a coronal plasma. From the outgassing rate, we estimate a
nucleus diameter of about 9 m. This rate steadily increases as the
comet approaches the Sun, while the optical brightness decreases by
more than a factor of 10 and suddenly recovers. This indicates that
the optical brightness is determined by the lifetimes of the grains,
sodium atoms, and molecules produced by the comet.
---------------------------------------------------------
Title: On the nucleus structure and activity of comet
67P/Churyumov-Gerasimenko
Authors: Sierks, Holger; Barbieri, Cesare; Lamy, Philippe L.; Rodrigo,
Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal,
Jessica; A'Hearn, Michael F.; Angrilli, Francesco; Auger, Anne-Therese;
Barucci, M. Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Besse,
Sebastien; Bodewits, Dennis; Capanna, Claire; Cremonese, Gabriele; Da
Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino;
Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert;
Giacomini, Lorenza; Groussin, Olivier; Gutierrez-Marques, Pablo;
Gutiérrez, Pedro J.; Güttler, Carsten; Hoekzema, Nick; Hviid, Stubbe
F.; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kovacs, Gabor;
Kramm, J. Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia,
Fiorangela; Lara, Luisa M.; Lazzarin, Monica; Leyrat, Cédric; Lopez
Moreno, Josè J.; Magrin, Sara; Marchi, Simone; Marzari, Francesco;
Massironi, Matteo; Michalik, Harald; Moissl, Richard; Mottola, Stefano;
Naletto, Giampiero; Oklay, Nilda; Pajola, Maurizio; Pertile, Marco;
Preusker, Frank; Sabau, Lola; Scholten, Frank; Snodgrass, Colin;
Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste; Wenzel,
Klaus-Peter; Zaccariotto, Mirco; Pätzold, Martin
2015Sci...347a1044S Altcode: 2015Sci...347.1044S
Images from the OSIRIS scientific imaging system onboard Rosetta
show that the nucleus of 67P/Churyumov-Gerasimenko consists of two
lobes connected by a short neck. The nucleus has a bulk density less
than half that of water. Activity at a distance from the Sun of >3
astronomical units is predominantly from the neck, where jets have been
seen consistently. The nucleus rotates about the principal axis of
momentum. The surface morphology suggests that the removal of larger
volumes of material, possibly via explosive release of subsurface
pressure or via creation of overhangs by sublimation, may be a major
mass loss process. The shape raises the question of whether the two
lobes represent a contact binary formed 4.5 billion years ago, or a
single body where a gap has evolved via mass loss.
---------------------------------------------------------
Title: Instant: An Innovative L5 Small Mission Concept for Coordinated
Science with Solar Orbiter and Solar Probe Plus
Authors: Lavraud, B.; Liu, Y. D.; Harrison, R. A.; Liu, W.;
Auchere, F.; Gan, W.; Lamy, P. L.; Xia, L.; Eastwood, J. P.;
Wimmer-Schweingruber, R. F.; Zong, Q.; Rochus, P.; Maksimovic, M.;
Temmer, M.; Escoubet, C. P.; Kilpua, E.; Rouillard, A. P.; Davies,
J. A.; Vial, J. C.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard,
T. A.; DeForest, C. E.
2014AGUFMSH21B4109L Altcode:
We will present both the science objectives and related instrumentation
of a small solar and heliospheric mission concept, INSTANT:
INvestigation of Solar-Terrestrial Activity aNd Transients. It will be
submitted as an opportunity to the upcoming ESA-China S-class mission
call later this year. This concept was conceived to allow innovative
measurements and unprecedented, early determination of key properties
of Earthbound CMEs from the L5 vantage point. Innovative measurements
will include magnetic field determination in the corona thanks to
Hanle measurement in Lyman-α and polarized heliospheric imaging
for accurate determination of CME trajectories. With complementary
in situ measurements, it will uniquely permit solar storm science,
solar storm surveillance, and synergy with Solar Orbiter and Solar
Probe Plus (the ESA-China S2 mission launch is planned in 2021).
---------------------------------------------------------
Title: Multi-Resolution Stereophotoclinometry by Deformation, a New
3D Shape Reconstruction Method Applied to ROSETTA/OSIRIS Images
Authors: Capanna, C.; Jorda, L.; Gesquière, G.; Gaskell, R. W.;
Groussin, O.; Gutiérrez, P.; Hviid, S. F.; Lamy, P. L.; Preusker,
F.; Rodionov, S.; Scholten, F.; Vibert, D.
2014AGUFM.P41C3941C Altcode:
We developed a new 3D shape reconstruction method which combines stereo,
photoclinometry and the deformation of a triangular mesh describing
the surface of the object. The method deforms the mesh - initially
a sphere - until the set of synthetic images, created from the mesh
(Jorda et al., SPIE 2010) match the observed one. Stereo control points
can be used as a constraint in the deformation of the mesh, but it is
not required at low resolutions.This new technique has been applied
to images of the nucleus of comet 67P/Churyumov-Gerasimenko acquired
by the OSIRIS instrument aboard the Rosetta spacecraft. The technique
allowed to reconstruct the shape of the nucleus and to retrieve its
rotational parameters from low-resolution images obtained with the
narrow-angle camera of OSIRIS in mid-July 2014, when stereo-based
techniques were still inapplicable. This model called "SHAP1" has
been delivered to ESA and to the lander team in July. The technique
has also been applied to higher-resolution images of the nucleus later
on, using the stereo information as a constraint. A comparison of the
reconstructed global and local models with those retrieved with other
techniques, such as stereophotoclinometry (Gaskell et al., MPS 2008)
and stereophotogrammetry (Preusker et al., PSS 2012) will be presented.
---------------------------------------------------------
Title: GIADA On-Board Rosetta: Early Dust Grain Detections and Dust
Coma Characterization of Comet 67P/C-G
Authors: Rotundi, A.; Della Corte, V.; Accolla, M.; Ferrari, M.;
Ivanovski, S.; Lucarelli, F.; Mazzotta Epifani, E.; Sordini, R.;
Palumbo, P.; Colangeli, L.; Lopez-Moreno, J. J.; Rodriguez, J.;
Fulle, M.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Green, S.;
Grün, E.; Lamy, P. L.; McDonnell, T.; Mennella, V.; Molina, A.;
Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. M.; Rodrigo, R.;
Weissman, P. R.; Zakharov, V.; Zarnecki, J.
2014AGUFM.P32B..05R Altcode:
GIADA (Grain Impact Analyzer and Dust Accumulator) flying on-board
Rosetta is devoted to study the cometary dust environment of
67P/Churiumov-Gerasimenko. GIADA is composed of 3 sub-systems:
the GDS (Grain Detection System), based on grain detection through
light scattering; an IS (Impact Sensor), giving momentum measurement
detecting the impact on a sensed plate connected with 5 piezoelectric
sensors; the MBS (MicroBalances System), constituted of 5 Quartz
Crystal Microbalances (QCMs), giving cumulative deposited dust mass by
measuring the variations of the sensors' frequency. The combination
of the measurements performed by these 3 subsystems provides: the
number, the mass, the momentum and the velocity distribution of
dust grains emitted from the cometary nucleus.No prior in situ dust
dynamical measurements at these close distances from the nucleus and
starting from such large heliocentric distances are available up to
date. We present here the first results obtained from the beginning
of the Rosetta scientific phase. We will report dust grains early
detection at about 800 km from the nucleus in August 2014 and the
following measurements that allowed us characterizing the 67P/C-G
dust environment at distances less than 100 km from the nucleus and
single grains dynamical properties. Acknowledgements. GIADA was
built by a consortium led by the Univ. Napoli "Parthenope" &
INAF-Oss. Astr. Capodimonte, IT, in collaboration with the Inst. de
Astrofisica de Andalucia, ES, Selex-ES s.p.a. and SENER. GIADA is
presently managed & operated by Ist. di Astrofisica e Planetologia
Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale
Italiana, IT, with a support of the Spanish Ministry of Education and
Science MEC, ES. GIADA was developped from a PI proposal supported by
the University of Kent; sci. & tech. contribution given by CISAS,
IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and
USA. We thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for
their outstanding work. Science support provided by NASA through the US
Rosetta Project managed by JPL/California Institute of Technology. GIADA
calibrated data will be available through the ESA's PSA web site
(www.rssd.esa.int/index.php?project=PSA&page=index). Thanks
Angioletta.
---------------------------------------------------------
Title: The photosphere-corona Interface: enrichement of the corona
in low FIP elements and helium shells
Authors: Bazin, C.; Koutchmy, S.; Lamy, P.; Veselovski, I.
2014sf2a.conf..209B Altcode:
Slitless consecutive spectra were obtained during the contacts of
the last total solar eclipses (2008, 2009, 2010, 2012, et 2013). They
allowed to show that the overabundance of low First Ionisation Potential
(FIP) elements (Fe II, Ti II, Ba II) in the corona comes from the low
layers of the solar atmosphere, just near and above the temperature
minimum region of the high photosphere. All spectra are recorded
with a fast CCD/CMOS camera, with an equivalent radial resolution of
60 milliarcseconds, or 45 km in the solar atmosphere, above a solar
edge not affected by the parasitic light like it is outside of total
eclipse conditions. Many emission lines of low FIP elements appear in
regions situated between 200 to 600 km above the solar limb defined by
the true continuum measured between the lines. This continuum appears
at these altitudes where the beta of the plasma is near 1. The He I
4713 Å and He II 4686 Å (Paschen alpha line) shells appear at the
height of 800 km above the solar edge and higher. The light curve I =
f(h) of each ion is located at a particuliar altitude in the solar
atmosphere. The scale height corresponds to a density variation, which
allows to evaluate the temperature thanks to the hydrostatic equilibrium
assumption. Moreover, with ionised Titanium lines taken as markers,
we show a similarity between the photosphere-corona interface and
the prominence-corona interface. We discuss the role of the magnetic
field and the ambipolar diffusion for supplying the corona in mass,
without taking into account the role of spicules. The photo-ionisation
of the helium lines by the EUV coronal lines is illustrated thanks to
an extract of SDO/AIA coronal stacked image simultaneously obtained.
---------------------------------------------------------
Title: Overview of the Geomorphology of the Nucleus of Comet
67P/Churyumov-Gerasimenko from OSIRIS Observations
Authors: Groussin, O.; Thomas, N.; Sierks, H.; Barbieri, C.; Lamy,
P. L.; Rickman, H.; Rodrigo, R.; Koschny, D.
2014AGUFM.P33F..01G Altcode:
Because of the very peculiar conditions at the surface of cometary
nuclei with very low gravity, outgassing, presence of ices and dust,
their geomorphology is particularly complex. The presence of hummocky
terrains (e.g., pits, hills, ridges, ...) and smooth terrains (e.g.,
mesas, …) and their spatial distribution over the surface contain
very valuable information to understand how comets work and to which
extend they may still contain pristine materials on or close to their
surface. Since July 2014, the Rosetta spacecraft has taken numerous
high spatial resolution images (meter scale) of the surface of the
nucleus of comet 67P/Churyumov-Gerasimenko with the OSIRIS cameras NAC
(Narrow Angle Camera) and WAC (Wide Angle Camera). In this paper, we
will present an overview of the geomorphologic features observed on
this comet nucleus, including the cartography of the main features,
and try to propose a scenario for the chronology of their formation
and evolution.
---------------------------------------------------------
Title: Experimental study of an uncooled microbolometer array for
thermal mapping and spectroscopy of asteroids
Authors: Brageot, E.; Groussin, O.; Lamy, P.; Reynaud, J. -L.
2014ExA....38..381B Altcode:
We report on the experimental study of the imaging and spectroscopic
capabilities of an uncooled microbolometer array for space missions
to small bodies in the inner solar system. The selected Nano640E <SUP>
T M </SUP> device manufactured by the ULIS company (Grenoble, France)
has a format of 640x480 pixels and can measure temperatures down to
at least 255 K, the lower limit reached in our tests. It has a Noise
Equivalent Temperature Difference (NETD) of 40.9 ±4.5 mK (300 K,
F/0.86) and the capability to produce excellent, radiometrically
calibrated images with an error of the order of 1 to 5 K depending
upon the number of calibration sources. Using a set of neutral density
filters, we determined the signal-to-noise ratio (SNR) of a spectrum
acquired by the detector, as a function of the scene temperature,
wavelength and spectral resolution. Considering an asteroid at 1 AU
from the Sun, an optical system at F/0.86, a spectral resolution of
0.3 μm and a scene temperature of >350 K, the resulting spectrum
has sufficient SNR to properly identify the main mineralogical emission
features. Our results show that uncooled microbolometer arrays are very
promising to acquire calibrated thermal images and mid-infrared (8-14
μm) spectra of the surface of small bodies in the inner solar system.
---------------------------------------------------------
Title: The Geomorphology of Comet Churymov-Gerasimenko As Revealed
By Rosetta/Osiris: Implicationsfor Past Collisional Evolution
Authors: Marchi, S.; A'Hearn, M. F.; Barbieri, C.; Barucci, M. A.;
Besse, S.; Cremonese, G.; Ip, W. H.; Keller, H. U.; Koschny, D.; Kuhrt,
E.; Lamy, P. L.; Marzari, F.; Massironi, M.; Pajola, M.; Rickman,
H.; Rodrigo, R.; Sierks, H.; Snodgrass, C.; Thomas, N.; Vincent, J. B.
2014AGUFM.P41C3940M Altcode:
In this paper we present the major geomorphological features of comet
Churymov-Gerasimenko (C-G), with emphasis on those that may have formed
through collisional processes. The C-G nucleus has been imaged with
the Rosetta/OSIRIS camera system at varying spatial resolution. At
the moment of this writing the maximum spatial resolution achieved is
~20 meter per pixel, and it will improve to reach the unprecedented
centimeter-scale in November 2014. This resolution should allow us to
identify and characterize pits, lineaments and blocks that could be
the result of collisional evolution. Indeed, C-G has spent some 1000
years on orbits crossing the main asteroid belt, and a much longer time
in the outer solar system. Collisions may have, therefore, shaped the
morphology of the nucleus in various ways. Previously imaged Jupiter
Family Comets (e.g., Tempel 1) show significant numbers of pits and
lineaments, some of which could be due to collisions. Additional
proposed formation mechanisms are related to cometary activity
processes, such as volatile outgassing.In addition to small scale
features, the overall shape of C-G could also provide insights into
the role of collisional processes. A striking feature is that C-G's
shape is that of a contact binary. Similar shapes have been observed
on rocky asteroids (e.g., Itokawa) and are generally interpreted as
an indication of their rubble pile nature. A possibility is that C-G
underwent similar processes, and therefore it may be constituted by
reaccumulated fragments ejected from a larger precursor. An alternative
view is that the current shape is the result of inhomogeneous outgassing
activity, which may have dug a ~1-km deep trench responsible for
the apparent contact binary shape.The role of the various proposed
formation mechanisms (collisional vs outgassing) for both small scale
and global features will be investigated and their implications for
the evolution of C-G will be discussed.
---------------------------------------------------------
Title: The Nucleus of Comet 67P/Churyumov-Gerasimenko : a New Case
of Contact Binary ?
Authors: Lamy, P. L.; A'Hearn, M. F.; Groussin, O.; Jorda, L.; Keller,
H. U.; Rickman, H.
2014AGUFM.P41C3937L Altcode:
The nucleus of comet 67P/Churyumov-Gerasimenko appears to be formed of
two components as revealed by images obtained with the OSIRIS narrow
angle camera and the derived 3-D shape model (Jorda et al. 2014). This
shape raises questions far beyond the obvious differences with the
nuclei visited so far. We will explore the possible scenarios that
may explain it. Whereas contact- binaries have been advocated for
elongated nuclei (e.g., 19P/Borrelly and 103P/Hartley 2), the only
unquestionable case remains that of 8P/Tuttle based on radar imaging
(Harmon at al. 2010) and indirectly confirmed by HST observations
(Lamy et al. 2008). However 8P originates from the Oort cloud where
the collisional activity is essentially non-existent. A contact-binary
among the Jupiter family comets (JFC) such as 67P would have profound
implications since it must be primordial and the comet must have
survived a possible history of collisions in the Kuiper belt. The
present cumulative distribution function of size of nuclei of JFC comets
indeed suggests a collisionally-relaxed population. Asymmetric erosion
of an initially larger more regular body or even of a pre-existing
contact binary will be studied in the framework of the past dynamical
evolution of 67P (e.g., Groussin et al. 2007). Although unlikely, the
scenario of a re-accumulated body following a catastrophic collision
will be considered. Forthcoming images at higher spatial resolution
with OSIRIS on the orbiter and CIVA and the lander will hopefully help
deciphering the origin of the nucleus of 67P and restricting the number
of possible scenarios.
---------------------------------------------------------
Title: Geomorphology of Active Regions on Comet
67P/Churyumov-Gerasimenko from Osiris Observations
Authors: Auger, A. T.; Groussin, O.; Jorda, L.; Bouley, S.; Lamy,
P. L.; Cremonese, G.; Thomas, N.; Sierks, H.
2014AGUFM.P41C3936A Altcode:
The geomorphological study of active regions on comets provides valuable
insights to understand how comets work and to which extend they may
still contain pristine materials on or close to their surface. The
Rosetta spacecraft is orbiting comet 67P/Churyumov-Gerasimenko since
summer 2014 and offers a unique opportunity to address this science
topic. The Narrow and Wide Angle Cameras of the OSIRIS imaging
experiment have acquired numerous images of the nucleus surface,
with a spatial resolution down to the meter scale. Here, we focus on
the geomorphology of some specific, active, regions of the nucleus,
releasing materials from their surface or from their upper layers. With
the help of digital terrains models and GIS tools, we map these regions
and report their size, area, shape, slopes and surface roughness. This
detailed analysis give us a reference point to emphasize their evolution
as the comet approaches perihelion, but also provide information on
the possibly pristine nature of these morphologies.
---------------------------------------------------------
Title: Comet 67P/Churyumov-Gerasimenko - First Science Results by
Rosetta/OSIRIS
Authors: Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny,
D.; Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Angrilli, F.; Barucci,
M. A.; Bertaux, J. L.; Bertini, I.; Besse, S.; Bodewits, D.; Capanna,
C.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco,
M.; Ferri, F.; Fornasier, S.; Fulle, M.; Gaskell, R. W.; Groussin,
O.; Güttler, C.; Gutiérrez, P.; Hviid, S. F.; Ip, W. H.; Jorda,
L.; Keller, H. U.; Joerg, K.; Kramm, R.; Kuhrt, E.; Küppers, M.; La
Forgia, F.; Lara, L.; Lazzarin, M.; Leyrat, C.; Moreno, J. F.; Lowry,
S.; Magrin, S.; Marchi, S.; Marzari, F.; Michalik, H.; Mottola, S.;
Account, T.; Oklay, N.; Pajola, M.
2014AGUFM.P32B..02S Altcode:
Abstract ESA's Rosetta mission arrived on August 6, 2014, at target
comet 67P/Churyumov-Gerasimenko after 10 years of cruise. OSIRIS
(Optical, Spectroscopic, and Infrared Remote Imaging System) is the
scientific imaging system onboard Rosetta. It comprises a Narrow
Angle Camera (NAC) for nucleus surface and dust studies and a Wide
Angle Camera (WAC) for the wide field coma investigations. We present
the first science results achieved by OSIRIS from the arrival at the
comet throughout the mapping phase. The overview will cover surface
morphology and activity of the nucleus as seen in gas, dust, and
local jets. Acknowledgements OSIRIS was built by a consortium led
by the Max-Planck-Institut für Sonnensystemforschung, Göttingen,
Germany, in collaboration with CISAS, University of Padova, Italy,
the Laboratoire d'Astrophysique de Marseille, France, the Instituto de
Astrofísica de Andalucia, CSIC, Granada, Spain, the Scientific Support
Office of the European Space Agency, Noordwijk, The Netherlands,
the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain,
the Universidad Politéchnica de Madrid, Spain, the Department of
Physics and Astronomy of Uppsala University, Sweden, and the Institut
für Datentechnik und Kommunikationsnetze der Technischen Universität
Braunschweig, Germany. The support of the national funding agencies of
Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB),
and the ESA Technical Directorate is gratefully acknowledged. We
thank the Rosetta Science Ground Segment at ESAC, the Rosetta Mission
Operations Centre at ESOC and the Rosetta Project at ESTEC for their
outstanding work enabling the science return of the Rosetta Mission.
---------------------------------------------------------
Title: Albedo and color variegations on 67/P Churyumov-Gerasimenko
as observed by OSIRIS/Rosetta
Authors: Leyrat, Cedric; Barucci, Maria Antonietta; Fornasier, Sonia;
Sierks, Holger; Hasselmann, Pedro; Besse, Sebastien; Oklay, Nilda;
Jorda, Laurent; Barbieri, Cesare; Lamy, Philippe; Koschny, Detlef;
Magrin, Sara; Bertini, Ivano; La Forgia, Fiorangela; A'Hearn, Michael;
Bertaux, Jean Loup; Davidsson, Bjorn; Fulle, Marco; Groussin, Olivier;
Gutierrez, Pablo; Hviid, Stubbe; Keller, Horst Uwe; Kueppers, Michael;
Lazzarin, Monica; Kuehrt, Ekkehard; Lara, Luisa; Thomas, Nicolas;
Vincent, Jean-Baptiste; Pajola, Maurizio
2014DPS....4610002L Altcode:
The ESA Rosetta spacecraft is in orbit around its target 67/P
Churyumov-Gerasimenko since August 6th 2014. The OSIRIS camera system
composed of the NAC (Narrow angle camera) and the WAC (Wide angle
Camera) has the capability to image both the nucleus and the coma
at different wavelengths from 0.245 microns up to 1 micron using
filters. First images acquired from 100km distance have already
revealed a very complex shape and potential areas with photometric
variations. From August 2014 to the Philae landing event in November
2014, the nucleus surface will be mapped at multiple resolutions (1m up
to 20 cm), helping in the landing site selection process. Such images
will be obtained at very different incidence, emission and phase angles,
allowing us to correct from topographical features the photometric
properties of the surface. This presentation will focus on the albedo
and colors variations, and on the spectral slopes derived from the
OSIRIS filters. Of particular interest will be the identification
of ices on the surface, and the mineralogical differences between
different areas characterized by different topographic features.
---------------------------------------------------------
Title: Comet 67P/Churyumov-Gerasimenko: First science results by
Rosetta/OSIRIS
Authors: Thomas, Nicolas; Sierks, Holger; Barbieri, Cesare; Lamy,
Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Agarwal,
Jessica; A'Hearn, Michael; Angrilli, Francesco; Barucci, Antonella;
Bertaux, Jean-Loup; Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis;
Capanna, Claire; Cremonese, Gabriele; Da Deppo, Vania; Davidsson,
Björn; Debei, Stefano; De Cecco, Mariolino; Ferri, Francesca;
Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Groussin, Olivier;
Güttler, Carsten; Gutierrez, Pedroj; Hviid, Stubbe; Ip, Wing-Huen;
Jorda, Laurent; Keller, Horst Uwe; Knollenberg, Jörg; Kramm, Rainer;
Kührt, Ekkehard; Küppers, Michael; LaForgia, Fiorangela; Lara,
Luisa; Lazzarin, Monica; Leyrat, Cedric; Lopez Moreno, Jose Juan;
Lowry, Stephen; Magrin, Sara; Marchi, Simone; Marzari, Francesco;
Michalik, Harald; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda;
Pajola, Maurizio; Sabau, Lola; Snodgrass, Colin; Tubiana, Cecilia;
Vincent, Jean-Baptiste; Wenzel, Peter
2014DPS....4610001T Altcode:
ESA’s Rosetta mission arrived on August 6, 2014, at target comet
67P/Churyumov-Gerasimenko after 10 years of cruise. OSIRIS (Optical,
Spectroscopic, and Infrared Remote Imaging System) is the scientific
imaging system onboard Rosetta. It comprises a Narrow Angle Camera (NAC)
for nucleus surface and dust studies and a Wide Angle Camera (WAC) for
the wide field coma investigations.We present the first science results
achieved by OSIRIS from the arrival at the comet throughout the mapping
phase. The overview will cover surface morphology and activity of the
nucleus as seen in gas, dust, and local jets.AcknowledgementsOSIRIS
was built by a consortium led by the Max-Planck-Institut für
Sonnensystemforschung, Göttingen, Germany, in collaboration with
CISAS, University of Padova, Italy, the Laboratoire d'Astrophysique de
Marseille, France, the Instituto de Astrofísica de Andalucia, CSIC,
Granada, Spain, the Scientific Support Office of the European Space
Agency, Noordwijk, The Netherlands, the Instituto Nacional de Técnica
Aeroespacial, Madrid, Spain, the Universidad Politéchnica de Madrid,
Spain, the Department of Physics and Astronomy of Uppsala University,
Sweden, and the Institut für Datentechnik und Kommunikationsnetze
der Technischen Universität Braunschweig, Germany. The support of
the national funding agencies of Germany (DLR), France (CNES), Italy
(ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate
is gratefully acknowledged. We thank the Rosetta Science Ground Segment
at ESAC, the Rosetta Mission Operations Centre at ESOC and the Rosetta
Project at ESTEC for their outstanding work enabling the science return
of the Rosetta Mission.
---------------------------------------------------------
Title: Hubble Space Telescope Observations of the Nucleus of Comet
C/2012 S1 (ISON)
Authors: Lamy, Philippe L.; Toth, Imre; Weaver, Harold A.
2014ApJ...794L...9L Altcode:
We report on the analysis of several sequences of broadband visible
images of comet C/2012 S1 (ISON) taken with the Wide Field Camera 3
of the Hubble Space Telescope on 2013 April 10, May 8, October 9, and
November 1 in an attempt to detect and characterize its nucleus. Whereas
the overwhelming coma precluded the detection of the nucleus in the
first two sequences, the contrast was sufficient in early October to
unambiguously retrieve the signal from the nucleus. Two images taken
within a few minutes led to similar V magnitudes for the nucleus of
21.97 and 22.0 with a 1σ uncertainty of 0.065. Assuming a standard
value for the geometric albedo (0.04) and a linear phase function with
a coefficient of 0.04 mag deg<SUP>-1</SUP>, these V values imply that
the nucleus radius is 0.68 ± 0.02 km. Although this result does depend
on these two assumptions, we argue that the radius most likely lies in
the range 0.6-0.9 km. This result is consistent with the constraints
derived from the water production rates reported by Combi et al. The
last sequence of images in 2013 November revealed temporal variation
of the innermost coma. If attributed to a single rotating jet, this
coma brightness variation suggests the rotational period of the nucleus
may be close to ~10.4 hr.
---------------------------------------------------------
Title: The rotation state of 67P/Churyumov-Gerasimenko from approach
observations with the OSIRIS cameras on Rosetta
Authors: Mottola, S.; Lowry, S.; Snodgrass, C.; Lamy, P. L.; Toth,
I.; Rożek, A.; Sierks, H.; A'Hearn, M. F.; Angrilli, F.; Barbieri,
C.; Barucci, M. A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo,
V.; Davidsson, B.; De Cecco, M.; Debei, S.; Fornasier, S.; Fulle,
M.; Groussin, O.; Gutiérrez, P.; Hviid, S. F.; Ip, W.; Jorda, L.;
Keller, H. U.; Knollenberg, J.; Koschny, D.; Kramm, R.; Kührt, E.;
Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari,
F.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.;
Thomas, N.; Wenzel, K. -P.; Agarwal, J.; Bertini, I.; Ferri, F.;
Güttler, C.; Magrin, S.; Oklay, N.; Tubiana, C.; Vincent, J. -B.
2014A&A...569L...2M Altcode:
<BR /> Aims: Approach observations with the Optical, Spectroscopic,
and Infrared Remote Imaging System (OSIRIS) experiment onboard
Rosetta are used to determine the rotation period, the direction of
the spin axis, and the state of rotation of comet 67P's nucleus. <BR
/> Methods: Photometric time series of 67P have been acquired by
OSIRIS since the post wake-up commissioning of the payload in March
2014. Fourier analysis and convex shape inversion methods have been
applied to the Rosetta data as well to the available ground-based
observations. <BR /> Results: Evidence is found that the rotation rate
of 67P has significantly changed near the time of its 2009 perihelion
passage, probably due to sublimation-induced torque. We find that
the sidereal rotation periods P<SUB>1</SUB> = 12.76129 ± 0.00005 h
and P<SUB>2</SUB> = 12.4043 ± 0.0007 h for the apparitions before
and after the 2009 perihelion, respectively, provide the best fit to
the observations. No signs of multiple periodicity are found in the
light curves down to the noise level, which implies that the comet
is presently in a simple rotation state around its axis of largest
moment of inertia. We derive a prograde rotation model with spin
vector J2000 ecliptic coordinates λ = 65° ± 15°, β = + 59°
± 15°, corresponding to equatorial coordinates RA = 22°, Dec = +
76°. However, we find that the mirror solution, also prograde, at λ
= 275° ± 15°, β = + 50° ± 15° (or RA = 274°, Dec = + 27°),
is also possible at the same confidence level, due to the intrinsic
ambiguity of the photometric problem for observations performed close to
the ecliptic plane. <P />Table 1 is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201424590/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Time dependent tomographic reconstruction of the solar corona
Authors: Peillon, C.; Vibert, D.; Frazin, R.; de Patoul, J.; Lamy, P.
2014ssip.confP...1P Altcode: 2014ssip.confP...1C
The distribution of the electron density in the corona is crucial to
advance the knowledge in understanding the nature of solar coronal
phenomena. Several methods for the reconstruction of 3D density of
the solar corona from projection data have been proposed. One of
the major difficulties is the problem of the restrictive assumption
that the structure of the corona does not vary with time. The solar
temporal evolution introduces a lot of errors in classic tomographic
reconstruction. In this poster we present a new time dependent
tomography method by adding a spatial, temporal and rotational
regularization matrices. We perform the method on images from a 3D MHD
model of the corona during a period of 14 days in November 2008. We
compute the normalized error between the model and the reconstruction
in order to estimate the quality of the reconstruction. We also perform
the developed tomography methods on polarized brightness images of
the SOHO/LASCO instrument. We show that the new time dependent method
decrease the number of artefacts by comparing our results with classic
static tomographic reconstruction. In particular, we show that the
spatial and temporal regularization matrices improves significantly
the reconstruction and that the rotational regularization is useful
when using a large amount of images during the 14 days period.
---------------------------------------------------------
Title: Constraints on the subsurface structure and density of
the nucleus of Comet 67P/Churyumov-Gerasimenko from Arecibo radar
observations
Authors: Kamoun, P.; Lamy, P. L.; Toth, I.; Herique, A.
2014A&A...568A..21K Altcode:
Context. Little is known about the internal structure of cometary
nuclei. In addition to understanding their accretion in the early
solar nebula and their subsequent evolution in the solar system,
we find this question to be of acute and timely interest in the case
of 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) due to be visited
by the Rosetta spacecraft in the second half of 2014. In particular,
the successful landing of the Philae surface module depends critically
upon the bulk density of the nucleus and the structure of its surface
layer. <BR /> Aims: In addition to fostering our general knowledge of
these properties, it is important to exploit all possible information
to assist in preparing the delivery of Philae. <BR /> Methods: We
performed an in-depth analysis of the observations done with the
radar system of the Arecibo Observatory in November 1982 when comet
67P/C-G had a close encounter with Earth at a geocentric distance of
0.4AU taking our present knowledge of the properties of its nucleus
(size, rotational state) into account. <BR /> Results: In the absence
of a detectable radar echo, we determined a maximum radar cross
section of 0.7 km<SUP>2</SUP>, leading to a maximum radar albedo of
0.05. This low albedo probably results from a combination of a low
radar reflectivity material and a lightly packed upper layer of the
nucleus with substantial roughness (rms slope of ≈55°), consistent
with its low thermal inertia. Based on radar observations of other
cometary nuclei and asteroids, it is unlikely that the albedo can
be lower than 0.04 so that we were able to constrain the dielectric
permittivity of the subsurface layer to a narrow range of 1.9 to
2.1. Laboratory measurements and our modeling of mixtures of ice and
dust have led to a porosity in the range of approximately 55 to 65%
and a density in the range of ≈600 to ≈1000 kg m<SUP>-3</SUP>
for the top ≈2.5 m layer of the nucleus. This would be the bulk
density range for a homogeneous nucleus and would place the success
of the landing at risk, but an inhomogeneous nucleus with an overall
density below this range remains a possibility.
---------------------------------------------------------
Title: Similar origin for low- and high-albedo Jovian Trojans and
Hilda asteroids?
Authors: Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan,
M.; Lamy, P.; Binzel, R. P.
2014A&A...568L...7M Altcode: 2014arXiv1407.7016M
Hilda asteroids and Jupiter Trojans are two low-albedo (p<SUB>v</SUB>
~ 0.07) populations for which the Nice model predicts an origin in
the primordial Kuiper Belt region. However, recent surveys by WISE
and the Spitzer Space Telescope (SST) have revealed that ~2% of these
objects possess high albedos (p<SUB>v</SUB> ≥ 0.15), which might
indicate interlopers - that is, objects not formed in the Kuiper
Belt - among these two populations. Here, we report spectroscopic
observations in the visible and / or near-infrared spectral ranges of
twelve high-albedo (p<SUB>v</SUB> > 0.15) Hilda asteroids and Jupiter
Trojans. These twelve objects have spectral properties similar to those
of the low-albedo population, which suggests a similar composition and
hence a similar origin for low- and high-albedo Hilda asteroids and
Jupiter Trojans. We therefore propose that most high albedos probably
result from statistical bias or uncertainties that affect the WISE
and SST measurements. However, some of the high albedos may be true
and the outcome of some collision-induced resurfacing by a brighter
material that could include water ice. Future work should attempt
to investigate the nature of this supposedly bright material. The
lack of interlopers in our sample allows us to set an upper limit of
0.4% at a confidence level of 99.7% on the abundance of interlopers
with unexpected taxonomic classes (e.g., A-, S-, V-type asteroids)
among these two populations. <P />Reflectance spectra presented
in this paper are available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/568/L7">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/568/L7</A>Based
on observations collected at the European Organisation for Astronomical
Research in the Southern Hemisphere, Chile (ESO program ID: 091.C-0247).
---------------------------------------------------------
Title: Constraints on the nucleus of comet C/2012 S1 (ISON) from
the Hubble Space Telescope observations
Authors: Lamy, P.; Toth, I.; Li, J.; Weaver, H.
2014acm..conf..304L Altcode:
Comet C/2012 S1 (ISON) was both a dynamically new comet, visiting
the inner solar system for the first time since being scattered
and deeply frozen in the Oort Cloud, and a sungrazing comet. This
unique combination made it an attractive target for the Hubble Space
Telescope. It was observed on 10 April 2013 when the comet was 4.15 au
from the Sun, 4.24 au from the Earth, and at a phase angle of 13.7°,
henceforth well before C/ISON crossed the ”snow line” (2.5--3
au), avoiding strong activity driven by water-ice sublimation and,
thus, potentially increasing the chance of detecting its nucleus. The
observations were performed over three separate orbits spanning a time
interval of 18 hours using the Wide Field Camera 3 (WFC3) UVIS detector
to image C/ISON through two broadband filters, the ”wide-V” F606W and
”blue” F438W filters (Li at al. 2013). The twelve images obtained
with the F606W filter were analyzed using our well-proven technique
of fitting a parametric model of the expected surface brightness to
the observed images (e.g., Lamy et al. 2006). The model consists of
an unresolved point source and a coma specified by a power law, both
convolved with the point spread function of the telescope. The nucleus
is basically undetected, which imposes an upper limit of its radius
of ∼0.3 km. However, the analysis is complicated by the so-called
”breathing” of the WFC3 camera, an uncontrolled slight defocus
which distorts the PSF. We investigated this question in detail and
considered various cases of defocus. We will report on this effort
and the resulting robust upper limit which we can put on the size of
the nucleus of C/ISON.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Reflectance spectra of 12 Trojans
and Hildas (Marsset+, 2014)
Authors: Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan,
M.; Lamy, P.; Binzel, R. P.
2014yCat..35689007M Altcode:
We present 17 reflectance spectra of 12 high albedo
(p<SUB>v</SUB>>0.14) Trojans (8 objects) and Hildas (4 objects)
obtained with the ESO/VLT Echelle spectrograph X-SHOOTER in
the 0.3-2.2um spectral range (14 spectra) and with the NASA/IRTF
spectrograph SpeX in the 0.8-2.5um spectral range (3 spectra). X-SHOOTER
spectra were normalized to unity at 0.55um and SpeX spectra were
normalized to unity at 2.2um . The spectra presented in this work were
collected between April and December 2013. <P />(18 data files).
---------------------------------------------------------
Title: Early results on 67P/Churyumov-Gerasimenko observed by
Rosetta/OSIRIS
Authors: Sierks, H.; Tubiana, C.; Snodgrass, C.; Agarwal, J.;
Güttler, C.; Oklay, N.; Vincent, J.; Küppers, M.; Barbieri, C.;
Lamy, P.; Rickman, H.; Rodrigo, R.; Koschny, D.; Hviid, S.; Mottola,
S.; Osiris Team
2014acm..conf..495S Altcode:
67P/Churyumov-Gerasimenko (67P) is the target comet of the ESA
Rosetta mission. Launched in 2004, the Rosetta spacecraft woke up on
the 20th of January 2014. After 36 months of deep space hibernation,
Rosetta is now traveling to rendezvous with the comet at 4.1 au from
the Sun, and it will follow 67P along its orbit, investigating how the
comet changes and evolves while approaching the Sun. <P />The Optical,
Spectroscopic, and Infrared Remote Imaging System OSIRIS (Keller et al.,
2007) is the scientific imaging system onboard Rosetta. It comprises
the Narrow Angle Camera (NAC) with wavelength range 250--1000 nm and
the Wide Angle Camera (WAC) with wavelength range 240--720 nm. The NAC
(FOV = 2.20×2.22 deg) is a system with high spatial resolution that
allows an initial detection of the nucleus, studies its structure and
rotation from relatively great distances, investigates the mineralogy
of the surface, and studies the dust ejection processes. The WAC has
much lower spatial resolution but, accordingly, a much wider field
of view (about 11.35×12.11 deg). This allows observations of the
3-dimensional flow field of dust and gas near the nucleus and, in
addition, provides a synoptic view of the whole nucleus. In summary,
the WAC would provide long-term monitoring of the entire nucleus from
close distances, while the NAC studies the details. The two camera
units have been designed as a complementary pair, which, on one hand,
addresses the study of the nucleus surface, and on the other hand,
investigates the dynamics of the sublimation process. <P />After
commissioning in March 2014, OSIRIS took first images of comet 67P and
its dust environment. Ground-based observations performed in 2007/08
when 67P was in the same orbital arc as it will be in March/April
2014, show that the comet was already active at 4.3 au inbound and
that its behavior was repetitive during the last three apparitions
(Snodgrass et al. 2013). We therefore expect to detect early comet
activity by OSIRIS in March/April 2014. At this time, Rosetta will
be at about 4 million kilometers from the comet and 67P will still be
unresolved. <P />We present results about the early cometary activity
based on OSIRIS images. Orange-filter images (central wavelength 649.2
nm) will be used to determine the dust environment of 67P, since this
wavelength range is quite free from gas emission lines. <P />Moreover,
a series of lightcurves will be taken to compare with the existing
ones and look for possible changes in the rotational period due to
its last perihelion passage.
---------------------------------------------------------
Title: Investigation of the interior of primordial asteroids and
the origin of the Earth's water: The INSIDER space mission
Authors: Vernazza, P.; Lamy, P.
2014acm..conf..559V Altcode:
Today's asteroid belt may not only be populated by objects that
formed in situ, typically between 2.2 and 3.3 au, but also by bodies
that formed over a very large range of heliocentric distances. It is
currently proposed that both the early (<5 Myrs after Solar System
formation) and late (>700 Myrs after Solar System formation)
dynamical evolution of the Solar System was governed by giant
planet migrations that led to the insertion of inner (1--3 au) as
well as outer (4--13 au) small bodies in the asteroid belt. Taken
altogether, the current dynamical models are able to explain many
striking features of the asteroid belt including i) its incredible
compositional diversity deduced mainly from spectroscopic observations
and meteorites measurements, and ii) the evidence of radial mixing
experienced by the various asteroid classes (e.g., S-, C-types) after
their formation. In a broad stroke, the idea that the asteroid belt
is a condensed version of the primordial Solar System is progressively
emerging. The asteroid belt therefore presents the double advantage of
being easily accessible and of offering crucial tests for the formation
models of the Solar System by exploring the building blocks predicted
by models of i) the telluric planets, ii) the giant planet cores,
iii) the giant planets' satellites, and iv) outer small bodies such
TNOs and comets. It also appears as an ideal place to search for the
origin of Earth's water. <P />Up to now, only a few asteroid classes
(e.g., several S-types) have been visited by spacecraft and the focus
of these in situ measurements has been mainly to give a geological
context to ground based observations as well as strengthen/validate
their interpretation. Most of the tantalizing discoveries of asteroid
missions have been realized via images of the objects surfaces. Time
has come for asteroid space science to reach a new milestone by
extending the reconnaissance of the Belt's diversity and addressing
new science questions. <P />The scientific objectives of the INSIDER
mission, to be proposed in response to the 2014 ESA call for an M-class
mission, require the exploration of diverse primordial asteroids ---
possibly the smallest surviving protoplanets of our Solar System ---
in order to constrain the earliest stages of planetesimal formation
thus avoiding the effect of destructive collisions, which produce
extensively processed rubble piles. Our science objectives that
justify in situ measurements in the context of an M-class mission
and that are expected to lead to significant breakthroughs include:
<P />- The exploration of the diversity of the asteroid belt <P />-
The first investigation of the internal structure of asteroids <P
/>- The origin of water on Earth <P />The proposed mission scenario
consists in i) successive rendez-vous followed by orbit insertion of
two and possibly three large (D>100 km) objects, ii) one or two small
landing modules (MASCOT type) to perform cosmochemical measurements (D/H
ratio, O isotopes). The potential targets would include 24 Themis and 10
Hygiea. <P />Meeting our science objectives requires instruments (such
as radar, seismometers to be dropped to the surface, magnetometer, high
resolution laser-desorption-ionization mass spectrometer to analyse the
surface samples) not flown so far during past asteroids missions along
with the traditional powerhouses, such as cameras and spectrometers.
---------------------------------------------------------
Title: Preliminary solution for the shape and rotational state of
the nucleus of comet 67P/Churyumov-Gerasimenko
Authors: Lamy, P.; Jorda, L.; Kaasalainen, M.; Hviid, S.; Faury, G.;
Toth, I.; Groussin, O.
2014acm..conf..303L Altcode:
In preparation of ESA's ROSETTA mission to comet
67P/Churyumov-Gerasimenko, solutions for the shape and rotational state
of its nucleus have been published based on observation with the Hubble
and Spitzer space telescopes as well as ground-based observations
(Lamy et al. 2006, 2007, 2008; Lowry et al. 2012). Following the
wake-up of the Rosetta spacecraft in January 2014 and the successful
commissioning of the OSIRIS camera system in March, a first lightcurve
of the inactive nucleus has been obtained on 23 March 2014 with the
OSIRIS Narrow Angle Camera (NAC). Further lightcurves will be acquired
in the forthcoming months. We will present an updated solution for the
shape and rotational state based on these data sets as of end of June
2014 combined with past Hubble and Spitzer space telescopes as well as
ground-based observations using the technique of lightcurve inversion.
---------------------------------------------------------
Title: Constraints on the subsurface structure and density of the
nucleus of Comet 67P/Churyumov-Gerasimenko from radar observations
Authors: Lamy, Philippe; Kamoun, Paul; Toth, Imre; Herique, Alain
2014EGUGA..16.6993L Altcode:
We performed an in-depth analysis of the observations carried with
the radar system of the Arecibo Observatory in November 1982 when
comet 67P/Churyumov-Gerasimenko had a close encounter with Earth
at a geocentric distance of 0.4 AU taking into account our present
knowledge of the properties of its nucleus (size, rotational state). In
the absence of a detectable radar echo, we determined a maximum
radar cross section of 0.7 km2 leading to a maximum radar albedo of
0.05. This low albedo probably results from a combination of a low radar
reflectivity material and a lightly packed upper layer of the nucleus
with substantial roughness (rms slope of ≡55°), consistent with
its low thermal inertia. Based on radar observations of other cometary
nuclei and asteroids, it is unlikely that the albedo can be lower than
0.04 so that we were able to constrain the dielectric permittivity
of the subsurface layer to a narrow range of 1.9 to 2.1. Laboratory
measurements and our modeling of mixtures of ice and dust led to a
porosity in the range of approximately 55 to 65% and a density in the
range of ≡600 to ≡1000 kg m-3 for the top ≡2.5 m layer of the
nucleus. This would be the bulk density range for an homogeneous nucleus
and would place the success of the landing at risk but an inhomogeneous
nucleus with an overall density below this range remains a possibility.
---------------------------------------------------------
Title: Radiation forces on small particles in the Solar System:
A re-consideration
Authors: Burns, Joseph A.; Lamy, Philippe L.; Soter, Steven
2014Icar..232..263B Altcode:
We respond to Klačka et al. (Klačka, J., Petržala,
J., Pástor, P., Kómar, L. [2014]. Icarus, this issue,
http://dx.doi.org/10.1016/j.icarus.2012.06.044.), who have criticized
many previous derivations of the acceleration experienced by a
spherical interplanetary particle owing to the Sun’s radiation. Much
of their criticism arises from differences in semantics and
notation as well as effects that are unimportant at Solar System
speeds. Accordingly, in the appropriate limiting cases, most published
expressions for the radiation forces, such as that found in Burns
et al. (Burns, J.A., Lamy, P.L., Soter, S. [1979]. Icarus 40 1-48),
are correct and duplicate the results of Klačka et al. (Klačka, J.,
Petržala, J., Pástor, P., Kómar, L. [2014]. Icarus, this issue,
http://dx.doi.org/10.1016/j.icarus.2012.06.044).
---------------------------------------------------------
Title: Low and high albedo jovian Trojans and Hildas: a similar or
different origin?
Authors: Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan,
M.; Lamy, P.; Binzel, R. P.
2014EPSC....9...54M Altcode:
Jupiter Trojans and Hilda asteroids are small primitive bodies
located near or beyond the snow line, around respectively the L4 and
L5 Lagrange points of Jupiter at ~5.2AU from the sun (Trojans) and in
the 2:3 mean-motion resonance with Jupiter near 3.9AU (Hildas). Our
current understanding of the early dynamical evolution of the Solar
System tells us that they probably originated from the primordial
transneptunian region from which they were captured in their current
location (Nice model; [6, 5]). In addition, this region not only
comprised planetesimals formed beyond the snow line (D-, T- and
X-type asteroids) but also a minor population of rocky interlopers
(e.g., A-, S-, V-type asteroids) that migrated outward during the
very early evolutionary phases of the Solar System 5 to 7My after its
formation (Grand Tack model; [8]). The recent discovery by WISE [2,
3] and Spitzer [1] of high albedo (pv ≥0.15) asteroids within jovian
Trojans and Hildas opened the possibility of an observational evidence
for the presence of a small fraction (~2 %) of such interlopers among
these two low albedo (pv ∼0.07) populations. Here, we report the
very first spectroscopic characterization of a sample of high albedo
tTrojans and Hildas obtained with X-SHOOTER and SpeX in the visible
and / or nearinfrared ranges. This study allows us to investigate
the origin of these high albedo objects and to provide an estimate
of the contamination rate of jovian Trojans and Hilda asteroids by
objects that do not belong to the C / T / D-type complex (e.g., A-,
S-, V-type asteroids), thus constraining migration models [7, 4, 6,
5, 8]. The results of this study will be presented in details.
---------------------------------------------------------
Title: The Interaction Between Coronal Mass Ejections and Streamers:
A Statistical View over 15 Years (1996 - 2010)
Authors: Floyd, O.; Lamy, P.; Llebaria, A.
2014SoPh..289.1313F Altcode:
We report on the statistical analysis of the interaction between
coronal mass ejections (CMEs) and streamers based on 15 years (from
1996 to 2010 inclusive) of observation of the solar corona with the
LASCO-C2 coronagraph. We used synoptic maps and improved the method
of analysis of past investigations by implementing an automatic
detection of both CMEs and streamers. We identified five categories of
interaction based on photometric and geometric variations between the
pre- and post-CME streamers: "brightening", "dimming", "emergence",
"disappearance", and "deviation". A sixth category, "no change",
included all cases where none of the above variations is observed. A
"global set" of 21 242 CMEs was considered as well as a subset of the
10 % brightest CMEs (denoted "top-ten") and three typical periods of
solar activity: minimum, intermediate, and maximum. We found that about
half of the global population of CMEs are not associated with streamers,
whereas 93 % of the 10 % brightest CMEs are associated. When there is a
CME-streamer association, approximately 95 % of the streamers experience
a change, either geometric or radiometric. The "no change" category
therefore amounts to approximately 5 %, but this percentage varies
from 1 - 2 % during minimum to 7 - 8 % during intermediate periods of
activity; values of 3 - 5 % are recorded during maximum. Emergences
and disappearances of streamers are not dominant processes; they
constitute 16 - 17 % of the global set and 23 % (emergence) and 28 %
(disappearance) of the "top-ten" set. Streamer deviations are observed
for 57 % and 70 % of, respectively, the global set and "top-ten"
CMEs. The cases of dimming and brightening are roughly equally present
and each case constitutes approximately 30 - 35 % of either set,
global or "top-ten".
---------------------------------------------------------
Title: Automated Processing of LASCO Coronal Images: Spurious
Point-Source-Filtering and Missing-Blocks Correction
Authors: Pagot, E.; Lamy, P.; Llebaria, A.; Boclet, B.
2014SoPh..289.1433P Altcode:
We report on automated procedures for correcting the images of the LASCO
coronagraph for i) spurious quasi-point-sources such as the impacts
of cosmic rays, stars, and planets, and ii) the absence of signal due
to transmission errors or dropouts, which results in blocks of missing
information in the images. Correcting for these undesirable artifacts
is mandatory for all quantitative works on the solar corona that require
data inversion and/or long series of images, for instance. The nonlinear
filtering of spike noise or point-like objects is based on mathematical
morphology and implements the procedure opening by morphological
reconstruction. However, a simple opening filter is applied whenever
the fractional area of corrupted pixels exceeds 50 % of the original
image. We describe different strategies for reconstructing the missing
information blocks. In general, it is possible to implement the method
of averaged neighbors using the two images obtained immediately before
and after the corrupted image. For the other cases, and in particular
when missing blocks overlapped in three images, we developed an
original procedure of weighted interpolation along radial profiles
from the center of the Sun that intercept the missing block(s). This
procedure is also adequate for the saturated images of bright planets
(such as Venus) that bleed along the neighboring pixels. Missing
blocks in polarized images may generally be reconstructed using the
associated unpolarized image of the same format. But in the case of
overlapping missing blocks, we implemented our procedure of weighted
interpolation. All tests performed on numerous LASCO-C2 images at
various periods of solar activity (i.e. varying complexity of the
structure of the corona) demonstrate the excellent performance of
these new procedures, with results vastly superior to the methods
implemented so far in the pipeline-processing of the LASCO images.
---------------------------------------------------------
Title: Global and Spatially Resolved Photometric Properties of the
Nucleus of Comet 67P/C-G from OSIRIS Images
Authors: Lamy, P.
2014EPSC....9..233L Altcode:
Following the successful wake-up of the ROSETTA spacecraft on 20
January 2014, the OSIRIS imaging system was fully re-commissioned at the
end of March 2014 confirming its initial excellent performances. The
OSIRIS instrument includes two cameras: the Narrow Angle Camera (NAC)
and the Wide Angle Camera (WAC) with respective fieldsofview of 2.2°
and 12°, both equipped with 2K by 2K CCD detectors and dual filter
wheels. The NAC filters allow a spectral coverage of 270 to 990 nm
tailored to the investigation of the mineralogical composition of
the nucleus of comet P/Churyumov- Gerasimenko whereas those of the
WAC (245-632 nm) aim at characterizing its coma [1]. The NAC has
already secured a set of four complete light curves of the nucleus
of 67P/C-G between 3 March and 24 April 2014 with a primary purpose
of characterizing its rotational state. A preliminary spin period of
12.4 hours has been obtained, similar to its very first determination
from a light curve obtained in 2003 with the Hubble space telescope
[2]. The NAC and WAC will be recalibrated in the forthcoming weeks
using the same stellar calibrators VEGA and the solar analog 16 Cyg B
as for past inflight calibration campaigns in support of the flybys of
asteroids Steins and Lutetia. This will allow comparing the pre- and
post-hibernation performances of the cameras and correct the quantum
efficiency response of the two CCD and the throughput for all channels
(i.e., filters) if required. The accurate photometric analysis of the
images requires utmost care due to several instrumental problems, the
most severe and complex to handle being the presence of optical ghosts
which result from multiple reflections on the two filters inserted
in the optical beam and on the thick window which protects the CCD
detector from cosmic ray impacts. These ghosts prominently appear as
either slightly defocused images offset from the primary images or
large round or elliptical halos. We will first present results on the
global photometric properties of the nucleus of comet 67P/C-G, albedo,
phase function and spectral reflectivity and compare with previous
results obtained with the Hubble and Spitzer space telescopes [2, 3,
4]. Then observations during the approach and first bound orbits in
July-August 2014 will allow mapping the surface of the nucleus with
OSIRIS at a scale of up to 1 meter per pixel. The images will be used
to reconstruct the 3D surface of the nucleus at highresolution allowing
separating true photometric variations from topographic effects. We
will present results on the spatially resolved photometric properties
of the nucleus based on a novel method developed in the space of the
facets representing the three-dimensional shape of the body. This
method successfully implemented in the cases of the nucleus of comet
9P/Tempel 2 and of asteroid (2867) Steins [5] has the advantage of
automatically tracking the same local surface element on a series of
images. The analysis will then proceed with the determination of the
global Hapke and other standard photometric parameters as well as their
two-dimensional variations across the surface. This allows defining, in
the body-fixed reference frame, “high residual regions” (HRRs) which
correspond to significant relative differences between the observed
and modeled photometric parameters such as the singlescattering albedo
(SSA), the mean roughness slope angle, and the reflectivity gradient. Of
particular interest will be the search for ice patches and possible
mineralogical differences resulting from the past activity of the comet.
---------------------------------------------------------
Title: First close view at comet 67P/ Churyumov-Gerasimenko by
Rosetta/OSIRIS
Authors: Sierks, H.; Barbieri, C.; Lamy, P.; Rickman, H.; Rodrigo, R.;
Koschny, D.; Keller, H. U.; Jorda, L.; Fornasier, S.; Massironi, M.;
Vincent, J. -B.; Snodgrass, C.; Tubiana, C.; Agarwal, J.; Güttler,
C.; Oklay, N.
2014EPSC....9..518S Altcode:
ESA's Rosetta mission arrived at target comet 67P/Churyumov-Gerasimenko
after 10 years of cruise. OSIRIS (Optical, Spectroscopic, and
Infrared Remote Imaging System) is the scientific imaging system
onboard Rosetta. It comprises a Narrow Angle Camera (NAC) for nucleus
surface and dust studies and a Wide Angle Camera (WAC) for the wide
field coma investigations. We present the first scientific results
from comet detection, activity wake-up, to the high resolution images
of surface and topographical features.
---------------------------------------------------------
Title: Global Shape and Topography of the Nucleus of Comet 67P/C-G
from ROSETTA/OSIRIS Images
Authors: Jorda, L.; Gaskell, R.; Hviid, S.; Capanna, C.; Groussin,
O.; Gutierrez, P.; Lamy, P.; Scholten, F.; Preusker, F.; Kaasalainen,
M.; Keller, H. U.; Knollenberg, J.; Kührt, E.; Mottola, S.; Sierks,
H.; Snodgrass, C.; Thomas, N.; Toth, I.; Vincent, J. -B.
2014EPSC....9..665J Altcode:
The ROSETTA spacecraft will approach the nucleus of comet
P/Churyumov-Gerasimenko in early August 2014 after a successful wake-up
on January 20, 2014. The OSIRIS instrument is a set of two cameras
aboard ROSETTA: the Narrow Angle Camera and the Wide Angle Camera which
have fields-of-view of 2.2° and about 12° respectively. Both cameras
are equipped with a 2K by 2K CCD detector. The two cameras have been
successfully re-commissioned at the end of March 2014. Observations
during the approach and first bound orbits in July-August 2014 will
allow to map the surface of the nucleus with OSIRIS at a scale as
small as 1 m/pixel. The images will be used to reconstruct the 3D
global topography of the nucleus at high-resolution with a combination
of two advanced reconstruction techniques: stereophotogrammetry and
stereophotoclinometry. The reconstructed global shape will be used
to determine the bulk density of the nucleus with an accuracy of
a few percent and to localize and quantitatively characterize the
main topographic features at its surface. It will also allow us to
identify the different types of terrains present at the surface of the
nucleus. We will describe and discuss the bulk properties of the nucleus
(bulk shape, density and moments of inertia) against those of other
comets observed from the ground or by previous space probes. We will
also identify the main topographic features from a combined analysis of
images and global digital terrain models and compare them with those
identified at the surface of comets P/Borrelly, P/Wild 2 and P/Tempel
1 by previous space probes. Finally, we will propose a preliminary
interpretation for the processes involved in their formation.
---------------------------------------------------------
Title: Early Grain Detections in the Coma of Comet
67P/Churyumov-Gerasimenko
Authors: Rotundi, A.; Della Corte, V.; Fulle, M.; Accolla, M.;
Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Sordini, R.; Zakharov, V.;
Mazzotta Epifani, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Colangeli,
L.; Palumbo, P.; Crifo, J. C.; Bussoletti, E.; Esposito, F.; Green, S.;
Grün, E.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.;
Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. -M.;
Rietmeijer, F. J. M.; Rodrigo, R.; Weissman, P. R.; Zarnecki, J. C.;
Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jeronimo, J. M.;
Leese, M. R.; Lopez-Jimenez, A.; Altobelli, N.
2014EPSC....9..868R Altcode:
The GIADA (Grain Impact Analyser and Dust Accumulator) instrument aboard
the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko (67P/C-G)
measures dust grain number, mass, momentum and velocity [1,2]. GIADA
is composed of three sub-systems: the Grain Detection System (GDS),
detecting dust grains based on light scattering; an Impact Sensor
(IS), providing momentum measurements from the impact on a plate
connected to five piezoelectric sensors; and the MicroBalances System
(MBS), made up of five Quartz Crystal Microbalances (QCMs), to yield
cumulative deposited dust mass through the shift in resonance frequency.
---------------------------------------------------------
Title: Giada: its Status after the Rosetta Cruise Phase and
On-Ground Activity in Support of the Encounter with Comet
67P/CHURYUMOV-GERASIMENKO
Authors: Della Corte, V.; Rotundi, A.; Accolla, M.; Sordini, R.;
Palumbo, P.; Colangeli, L.; Lopez–Moreno, J. J.; Rodriguez, J.;
Rietmeijer, F. J. M.; Ferrari, M.; Lucarelli, F.; Mazzotta Epifani, E.;
Ivanovski, S.; Aronica, A.; Cosi, M.; Bussoletti, E.; Crifo, J. F.;
Esposito, F.; Fulle, M.; Green, S. F.; Gruen, E.; Herranz, M. L.;
Jeronimo, J. M.; Lamy, P.; Lopez Jimenez, A.; McDonnell, J. A. M.;
Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Palomba, E.;
Perrin, J. M.; Rodrigo, R.; Weissman, P.; Zakharov, V.; Zarnecki, J. C.
2014JAI.....350011D Altcode:
GIADA (Grain Impact Analyser and Dust Accumulator) on-board the
Rosetta mission to comet 67P/Churyumov-Gerasimenko was designed
to study the physical and dynamical properties of dust particles
ejected by the comet during the encounter. In this paper we report
the results of the analysis of data collected by GIADA during the
past seven years of the cruise phase. During this period the GIADA
detection subsystems were switched on for periodic in-flight payload
checkouts to monitor their state-of-health including potential changes
in its performance that could affect its data collection. Only slight
variations in sensitivity and dynamical range were identified that
will not affect the GIADA measurement capability during the Rosetta
comet encounter and rendezvous phase. The GIADA microbalance system
detected the presence of low-volatility material over a period of
about 169 days when the GIADA cover remained partially opened. It
is highly probable that this material originated from the spacecraft
itself, as a spacecraft's outgassing was observed by the ROSINA mass
spectrometer (on-board Rosetta) during the cruise phase. <P />The
identification of the low-volatility mass deposited on the microbalances
as self-contamination will allow us to evaluate the mass rate background
to be subtracted from the GIADA science data. These results obtained
from GIADA cruise data analysis coupled with laboratory calibration data
obtained from measurements using the GIADA spare model for selected
cometary dust analogs will be the basis for the interpretation of the
GIADA scientific data.
---------------------------------------------------------
Title: Possible measurements of the magnetic field in eruptive
prominences using the PROBA-3 coronagraph
Authors: Serge, Koutchmy; Zhukov, Andrei; Dolla, Laurent; Heinzel,
Petr; Lamy, Philippe; Bazin, Cyrille; Bommier, Veronique; Faurobert,
Marianne
2014cosp...40E2971S Altcode:
The PROBA-3 mission will fly a spacecraft put in the shadow of a
precisely occulting sister satellite orbiting “in formation” at a
distance of 150 m in front of it to make artificial total eclipses. The
region right above the solar limb will be studied for the first time
over a coronal background not polluted by any spurious light. Although
the priority will be the high-resolution fast imaging of the dynamic
white-light corona, the use of a narrow filter centered on a low
excitation D3 line of He I, is planned for imaging prominences. Adding
the linear polarization analysis would permit the measurements of the
magnetic field using the Hanle effect. We evaluate the possibility
offered during the eruptive phase of a CME with prominence material
inserted inside, for studying the associated magnetic field changes
related to both the heating process and the ejection of material. The
background highly polarized K-corona is taken into account. Sequences of
quasi- simultaneous white-light processed images at high resolution are
an additional feature of great interest for interpreting the overall
magnetic structure.
---------------------------------------------------------
Title: Observation of the prominence cavity region using slitless
eclipse flash spectra and space borne EUV filtergrams
Authors: Bazin, Cyrille; Koutchmy, Serge; Lamy, Philippe; Tavabi, Ehsan
2014IAUS..300..151B Altcode:
We used total solar eclipse free of parasitic light for studying the
prominence to corona interface, and the corresponding cavity in the
context of the coronal physics. We analysed the visible continuum
between the prominences to directly look at the electron density. We
demonstrate some enhanced heating in the cavity region. Some
similarities with the interface regions are shown: the photosphere
to the chromosphere and the prominence to the corona interface. The
optically thin neutral Helium at 4713 Å and the singly ionized Helium
4686 Å Paschen α lines are considered. We summed 80 slitless visible
eclipse flash spectra that we compare with simultaneously obtained
EUV SWAP/Proba2 174 Å images of ESA and AIA/SDO 171Å 193 Å 304 Å
and 131 Å filtergrams. Intensity profiles in a radial direction are
studied. We deduce the variation of the intensity ratio I(He I 4713)
/ I(He II 4686). Discussion: the temperature rises at the edge of the
prominences. We evaluate for the first time with spectrophotometric
accuracy the continuum modulations in prominence spectra. W-L intensity
deficits are observed near the prominence boundaries in both eclipse
spectra and in EUV images, confirming that the prominence -cavity
regions correspond to a relative depression of plasma density of the
surrounding corona. Conclusion: we demonstrate some enhanced heating
occurring in these regions assuming hydrostatic equilibrium.
---------------------------------------------------------
Title: Comparing the solar minima of cycles 22/23 and 23/24: The
view from LASCO white light coronal images
Authors: Lamy, P.; Barlyaeva, T.; Llebaria, A.; Floyd, O.
2014JGRA..119...47L Altcode:
The Large Angle and Spectrometric Coronagraph LASCO-C2 aboard SOHO has
now completed 17 years (1996-2012) of quasi-continuous white-light
imaging of the corona from 2.2 to 6.5 solar radii, thus allowing
an unprecedented view of its evolution over a solar cycle and a half
including the minima of solar cycles 22/23 and 23/24. The corrected and
calibrated polarization sequences produce images of the radiance (B),
the polarized radiance (pB), and the electron density N<SUB>e</SUB>
of the K corona, and, in turn, of their synoptic maps. Their temporal
variations are quantified by integration first globally, then in the
north and south hemispheres, and finally, in sectors of 30° latitudinal
extent centered along the equatorial and polar directions. The global
radiance of the K corona follows well the solar activity as described
by the sunspot number and the radio flux and was 24% fainter during the
minimum of solar cycle 23/24 than during that of cycle 22/23. However,
the two hemispheres experienced different reductions, 17% for the north
one and 29% for the south one. The equatorial sector suffered a drastic
reduction of 44%, in remarkable agreement with the in situ measurements
of Wind and ACE at 1 AU, whereas the north and south polar sectors did
not experience much variation. Cycle 23 is estimated to have lasted
12 years and 3 months. Maximum conditions have been reached in the
northern region, whereas the southern region is still lagging. Finally,
the rate of coronal mass ejections follows well the solar activity.
---------------------------------------------------------
Title: Coronal mass ejections (CMEs) during the ascending phase of
cycle 24
Authors: Lamy, Philippe; Floyd, Olivier; Barlyaeva, Tatiana
2014cosp...40E1745L Altcode:
The Artemis-II catalog of coronal mass ejections (Floyd et al.,
Solar Phys 2013) lists their properties (date and time of appearance,
position angle, angular width, mass and kinetic energy) based on
detection and measurements performed on synoptic maps constructed from
the calibrated SOHO/LASCO-C2 images of the K-corona from January 1996
to December 2010. It has now been extended to 2013 allowing an analysis
of their properties during the ascending phase of solar cycle 24 and
a comparison with the previous cycle. In addition, these properties
are compared to three indices of solar activity, the international
sunspot number (SSN), the sunspot area (SSA) and the radio flux at
10.7~cm (F10.7), either globally or separately in the North and South
hemispheres in the case of the first two proxies. The monthly averaged
number and mass of CMEs exhibit a time shift of 12 years and 9 months
between the ascending phases of cycles 23 and 24, in agreement with
the anomanously long 23/24 minimum. Both are significantly less during
the present cycle than the previous one in agreement with a weak cycle
24. There are strong linear correlations of the monthly averaged number
and mass of CMEs with both SSA and F10.7 but less so with SSN. However
two significantly different regimes are observed for the whole cycle
23 and for the ascending phase of cycle 24 implying a comparatively
larger CME activity after 2009 with respect to both SSA and F10.7. The
analysis in separate hemispheres reveals a contrasted situation with
significantly different rates and different linear correlations with
the proxies. Possible origins of these differences will be discussed.
---------------------------------------------------------
Title: The WATCHER Heliospheric and Spaceweather Mission
Authors: Lamy, Philippe; Xia, Lidong
2014cosp...40E1746L Altcode:
Coronal mass ejections (CMEs) and their interplanetary counterparts
ICMEs and corotating interaction region (CIRs) are the main disturbances
of solar origin that impact Earth’s magnetosphere resulting in
geomagnetic storms. In addition, CMEs can drive shock starting very
close to the Sun than can therefore hit the Earth contrary to CIRs
shocks which form beyond 1 AU. We present the WATCHER mission with
the dual purpose of providing key scientific data on the two primary
sources of spaceweather and directly serving the very purposes of
spaceweather forecast. This will be achieved by placing a three-axis
stabilized satellite on the Earth-L5 (Lagrangian point) arc at an offset
angle of 30-60° from Earth and an adequate payload combining remote
and in situ capabilities. From this ideal position and overlooking the
region extending from the Sun to 1 AU, it will act as a CME/ICME and CIR
watcher and sample the local solar wind. WATCHER will be able to provide
advanced warning of solar eruptions, CMEs, CIRs and shocks well before
their detection by Earth-based or L1 space-based observatories. WATCHER
mission will address the following science objectives. 1. Determine the
magnetic conditions in the Sun interior and at its surface precursors
of interplanetary disturbances terrestrial observations. 2. Detect
and track interplanetary disturbances (CMEs/ICMEs and CIRs) from their
sources to Earth and determine their magnetic structure. 3. Determine
where shocks form and how they evolve. 4. Understand the role of
interactions affecting the propagation of disturbances (especially
CMEs) and how they affect their arrival time at Earth. 5. Study the
Sun-Earth relations as a global, complex system. The WATCHER S/C will
carry the following suite of instruments. A Magnetic and Doppler
Imager will i) measure the photospheric magnetic field and acquire
magnetograms allowing observing the source regions of CMEs before they
rotate to Earth view, ii) measure velocity fields allowing performing
stereo heliosismology in combination with other observatories probing
the convection zone where the Sun acquires its magnetism. A combined
disk imager and inner coronal imager in EUV. EUV images offer several
diagnostics of eruptions, indicate the solar source location of CMEs,
and map coronal holes. They will provide advanced warning of active
regions that would be rotating on to the disk to face Earth and of HSS
and CIRs. A white light coronagraph will then observe, characterize and
track CMEs up to about 20 solar radii (Rs). A couple of heliospheric
imagers will pursue the tracking to 1 AU. A Solar Wind Plasma Instrument
and a magnetometer will make in-situ measurements of the solar wind
providing information on CIRs that would arrive at Earth about 4
days after being detected in situ. Possible additional candidates,
depending on S/C resources are a low-frequency radiotelescope with
spectral coverage of 2-100 Rs to identify CMEs driving shocks and an
energetic particle detector to address the unsolved issue of flare
and CME-shock contributions to large SEP events.
---------------------------------------------------------
Title: The Characteristics and Evolution of the Dust Coma of Comet
C/2012 S1 (ISON)
Authors: Li, Jian-Yang; Kelley, M. S.; Knight, M. M.; Farnham, T.;
Weaver, H. A.; A'Hearn, M. F.; Mutchler, M. J.; Kolokolova, L.; Lamy,
P. L.; Toth, I.; Xia, K.
2014AAS...22321806L Altcode:
C/2012 S1 (ISON) is a dynamically new comet with a sungrazing perihelion
only 1.7 solar radii from the Sun's surface, which makes it unique
among the known comets. The discovery of C/ISON in September 2012
at a heliocentric distance of ~6 AU is more than one year before its
perihelion in November 2013, allowing a detailed characterization as
the comet moves from the frigid conditions of the outer solar system
to extreme heating during its close passage near the Sun. As part
of an international observing campaign, the Hubble Space Telescope
(HST) imaged the comet in multiple epochs from April to October 2013
pre-perihelion to characterize its dust coma at 4.15, 3.78, and 1.50
AU. We report on our analysis of these HST images, including the
dust production rate, the dust coma colors and morphology, and the
rotation pole of the nucleus. The first two epochs of observations
showed that C/ISON displays a color variations in its dust coma within
~5000 km from the nucleus that is best explained by the existence and
sublimation of water ice grains. The pole orientation, as measured
from the sunward jet, suggests a high obliquity, and indicates that
the nucleus of C/ISON always faces the Sun with one hemisphere until
about a week before the perihelion. We will use the observations in
October to search for any evolutionary changes in the coma, and to
refine the determination of the rotation pole.
---------------------------------------------------------
Title: Physical properties of craters on the Achaia region of asteroid
(21) Lutetia
Authors: Auger, A.; Bouley, S.; Jorda, L.; Groussin, O.; Baratoux,
D.; Capanna, C.; Lamy, P. L.
2013AGUFM.P23A1755A Altcode:
The Rosetta spacecraft flew by the main-belt asteroid (21) Lutetia
on 10 July 2010. Images of the surface were acquired with the Narrow
Angle Camera, from which Digital Terrain Models (DTM) of the surface
were produced. These DTMs give access to the topography to study the
physical properties of the craters of the asteroid. In this study,
we focus on their depth-to-diameter ratio (d/D) to study their
degradation. The d/D ratios are are derived from the DTM of Jorda et
al. (2012), based on the method of Gaskell et al. (2008), which offers
the best compromise between spatial resolution and the accuracy of the
topographic reconstruction. Our values differ notably from previous
studies (Vincent et al., 2012; Thomas et al., 2012). The discrepancy
has been found to result from the fact that the local slope of the
terrains on which the craters formed is ignored in these studies,
whereas we rigorously takes this into account in our calculations. As
a consequence, we find that d/D values for the fresh craters of Lutetia
are consistent with the values found on other asteroids of similar size
(within on order of magnitude) like (243) Ida or (951) Gaspra (Carr et
al., 1994; Sullivan et al., 1996). The Achaia region may be divided
into three units based on geomorphological analysis. A comparison of
the crater density on the three units suggests two different ages, the
youngest part corresponding to the Nicaea crater unit. Interestingly,
the mean d/D values of the three units are different. The craters of
these units were therefore differently affected by geological events
(e.g., essentially impact and associated phenomena such as seismic
shaking or ejecta blanketing) that occurred in the past history of
Lutetia. Some of these events must be recent since several lineaments
intersect most craters of one of the unit. Ejecta deposits have been
previously noted on one part of Achaia and provide a good explanation
for the low d/D values on this unit. Moreover, we suggest that tectonic
activity may have been responsible for the erasure of small craters. The
link between these events and the impacts at the origin of the North
Polar Crater Cluster of Lutetia will be discussed.
---------------------------------------------------------
Title: Pre-perihelion characterization of Comet C/2012 S1 (ISON)
Authors: Li, J.; Kelley, M. S.; Farnham, T. L.; A'Hearn, M. F.;
Knight, M. M.; Weaver, H. A.; Mutchler, M.; Lamy, P. L.; Toth, I.
2013AGUFM.P24A..02L Altcode:
Comet C/2012 S1 (ISON) is a dynamically new comet on a sungrazing
orbit. As such, C/ISON represents a unique opportunity to study both
the cosmic-ray-irradiated surface, produced during the comet's long
residence in the Oort cloud, and much deeper layers in the nucleus,
exposed when the comet passes within 2 solar radii of the Sun at
perihelion. During the first phase of our investigation, we collected
broadband images of C/ISON on April 10, 2012 at a heliocentric distance
of 4.15 AU, using the Hubble Space Telescope WFC3/UVIS. We used the
F606W and F438W filters in three HST orbits covering a total span of ~19
hrs. The comet shows a well delineated coma in the sunward direction
extending about 2" from the nucleus, and a dust tail at least 25"
long. The coma has an average red color of 5%/0.1 micron within 1.6"
from the nucleus, becoming redder towards the tail. Both the color
and the size of the coma in the sunward direction are consistent
with outflow of micron sized dust. Broadband photometry yielded Afρ
of 1376 cm at 589 nm, and 1281 cm at 433 nm, measured with a 1.6"
radius aperture. The total brightness of the comet within a 0.12"
radius aperture remained unchanged within 0.03 mag for the entire
duration of the observations. A well defined sunward jet is visible
after removing the 1/ρ brightness distribution. The jet is centered
at position angle 290 deg (E of Celestial N), with a cone angle of 45
deg, a projected length of 1.6", and a slight curvature towards the
north near the end. No temporal change in the morphology is observed,
suggesting the jet is circumpolar. Under this assumption, the jet's
apparent position constrains the rotational pole to lie within 30 deg
of (RA, Dec) = (330, 0), and an obliquity of 50-80 deg. Preliminary
analysis using a coma-nucleus separation technique suggests a nuclear
radius less than 2 km. The survival of such a small nucleus during
its perihelion at 2.7 solar radii is certainly questionable.
---------------------------------------------------------
Title: Characterizing the Dust Coma of Comet C/2012 S1 (ISON) at
4.15 AU from the Sun
Authors: Li, Jian-Yang; Kelley, Michael S. P.; Knight, Matthew M.;
Farnham, Tony L.; Weaver, Harold A.; A'Hearn, Michael F.; Mutchler,
Max J.; Kolokolova, Ludmilla; Lamy, Philippe; Toth, Imre
2013ApJ...779L...3L Altcode: 2013arXiv1311.0826L
We report results from broadband visible images of comet C/2012 S1
(ISON) obtained with the Hubble Space Telescope Wide Field Camera 3
on 2013 April 10. C/ISON's coma brightness follows a 1/ρ (where ρ
is the projected distance from the nucleus) profile out to 5000 km,
consistent with a constant speed dust outflow model. The turnaround
distance in the sunward direction suggests that the dust coma is
composed of sub-micron-sized particles emitted at speeds of tens of
m s<SUP>-1</SUP>. A(θ)fρ, which is commonly used to characterize
the dust production rate, was 1340 and 1240 cm in the F606W and
F438W filters, respectively, in apertures <1.”6 in radius. The
dust colors are slightly redder than solar, with a slope of 5.0% ±
0.2% per 100 nm, increasing to >10% per 100 nm 10,000 km down the
tail. The colors are similar to those of comet C/1995 O1 (Hale-Bopp)
and other long-period comets, but somewhat bluer than typical values for
short-period comets. The spatial color variations are also reminiscent
of C/Hale-Bopp. A sunward jet is visible in enhanced images, curving
to the north and then tailward in the outer coma. The 1.”6 long
jet is centered at a position angle of 291°, with an opening angle
of ~45°. The jet morphology remains unchanged over 19 hr of our
observations, suggesting that it is near the rotational pole of the
nucleus, and implying that the pole points to within 30° of (R.A.,
decl.) = (330°, 0°). This pole orientation indicates a high obliquity
of 50°-80°.
---------------------------------------------------------
Title: ARTEMIS II: A Second-Generation Catalog of LASCO Coronal Mass
Ejections Including Mass and Kinetic Energy
Authors: Floyd, O.; Lamy, P.; Boursier, Y.; Llebaria, A.
2013SoPh..288..269F Altcode:
The ARTEMIS-I catalog of coronal mass ejections (CMEs) was initially
developed on a first generation of low-resolution synoptic maps
constructed from the SOHO/LASCO-C2 images of the K-corona and resulted
in an online database listing all events detected since January 1996
(Boursier et al., Solar Phys.257, 125, 2009). A new generation of
synoptic maps with higher temporal (a factor of 1.5) and angular
(a factor of 2.5) resolutions allowed us to reconsider the question
of CME detection and resulted in the production of a new catalog:
ARTEMIS-II. The parameters estimated for each detected CME are still
the date and time of appearance, the position angle, the angular width,
and (when detected at several solar distances) the global and median
velocities. The new synoptic maps correct for the limited number of
velocity determinations reported in the ARTEMIS-I catalog. We now
determine the propagation velocity of 79 % of detected CMEs instead
of 30 % in the previous version. A final major improvement is the
estimation of the mass and kinetic energy of all CMEs for which we
could determine the velocity, that is ≈ 13 000 CMEs until December
2010. Individual comparisons of velocity determination of 23 CMEs
for which a full three-dimensional kinematical solution has been
published indicate that ARTEMIS-II performs extremely well except at
the highest velocities, an intrinsic limitation of our method. Finally,
individual comparisons of mass determination of seven CMEs for which
a robust solution has been obtained from stereographic observations
demonstrate the quality of the ARTEMIS-II results.
---------------------------------------------------------
Title: Sunskirting comets discovered with the LASCO coronagraphs
over the decade 1996-2008
Authors: Lamy, P.; Faury, G.; Llebaria, A.; Knight, M. M.; A'Hearn,
M. F.; Battams, K.
2013Icar..226.1350L Altcode:
In addition to an unprecedented number of Kreutz sungrazing comets, the
LASCO coronagraphs have discovered some 238 unrelated “sunskirting”
comets over the 12 years from 1996 to 2008. This new class is organized
in several groups, and at least two comets have further been found
periodic. This article presents the photometry and the heliocentric
light curves of these 238 sunskirting comets. The bulk of them exhibit
a continuous increase of the brightness as the comet approaches the
Sun, reach a peak before perihelion and then progressively fade with
a large variety of brightness gradients. However some of them have
peak brightness either at or post-perihelion, whereas a quite large
number are approximately flat. Likewise for the sungrazers, we find a
color effect prominent between 8 and 40R<SUB>⊙</SUB> (solar radii)
which we interpret as resulting from the emission lines of the Na I
doublet (D lines). We finally characterize the different groups of
sunskirters on the basis of their cumulative distribution function of
the peak brightness and of their fragmentation history.
---------------------------------------------------------
Title: Early pre-perihelion characterization of Comet C/2012 S1 (ISON)
Authors: Li, Jian-Yang; Kelley, M. S.; Farnham, T. L.; A'Hearn, M. F.;
Knight, M. M.; Weaver, H. A.; Mutchler, M. J.; Lamy, P.; Toth, I.
2013DPS....4540702L Altcode:
Comet C/2012 S1 (ISON) is a dynamically new comet on a sungrazing
orbit. As such, C/ISON represents a unique opportunity to study both
the cosmic-ray-irradiated surface, produced during the comet's long
residence in the Oort cloud, and much deeper layers in the nucleus,
exposed when the comet passes 1.7 solar radii from the Sun's surface at
perihelion. During the first phase of our investigation, we collected
broadband images of C/ISON on April 10, 2012 at a heliocentric distance
of 4.15 AU, using the Hubble Space Telescope WFC3/UVIS. We used the
F606W and F438W filters in three HST orbits covering a total span of ~19
hrs. The comet shows a well delineated coma in the sunward direction
extending about 2" from the nucleus, and a dust tail at least 25"
long. The coma has an average red color of 5%/0.1 micron within 1.6"
from the nucleus, becoming redder towards the tail. Both the color
and the size of the coma in the sunward direction are consistent
with outflow of micron sized dust. Broadband photometry yielded Afρ
of 1376 cm at 589 nm, and 1281 cm at 433 nm, measured with a 1.6"
radius aperture. The total brightness of the comet within a 0.12"
radius aperture remained unchanged within 0.03 mag for the entire
duration of the observations. A well defined sunward jet is visible
after removing the 1/ρ brightness distribution. The jet is centered
at position angle 290 deg (E of Celestial N), with a cone angle of 45
deg, a projected length of 1.6", and a slight curvature towards the
north near the end. No temporal change in the morphology is observed,
suggesting the jet is circumpolar. Under this assumption, the jet’s
apparent position constrains the rotational pole to lie within 30 deg
of (RA, Dec) = (330, 0), and an obliquity of 50-80 deg. Preliminary
analysis using a coma-nucleus separation technique suggests a nuclear
radius less than 2 km. The survival of such a small nucleus during
its sungrazing perihelion is certainly questionable.
---------------------------------------------------------
Title: Hubble Imaging of the Nucleus of Comet ISON
Authors: Lamy, Philippe
2013hst..prop13478L Altcode:
Comet C/2012 S1 {ISON} is both a new "nearly isotropic" and a
sungrazing comet with anoutstanding apparition in cycle 21, passing
within 0.42 AU of the Earth.We propose a 12-orbit Hubble postperihelion
investigation of this comet that will provide a detailed view of its
nucleus originating from the Oort cloud and of the possible consequences
of its very close approach to the Sun at a perihelion distance of
0.012471 AU such as fragmentation.We will determine the size, shape,
rotational period, and color {UBVRI} ofthe nucleus of C/2012 S1 or of
its fragment should disruption occurs. This passage of a new "nearly
isotropic" comet very close tothe Earth offers a rare opportunity
to investigate this population ofobjects, and we expect many other
observatories to attempt detecting itsnucleus in the mid-infrared,
millimetric and centimetric domains.Combining the Hubble results with
those from other observatories shouldyield a comprehensive picture
of this NIC that can be compared to thedetailed data collected on
ecliptic comets {ECs} during the past 3decades. The differences and
similarities between NICs and ECs shouldyield valuable insights into
the origin and evolution of comets.
---------------------------------------------------------
Title: Millimetre continuum observations of comet C/2009 P1 (Garradd)
Authors: Boissier, J.; Bockelée-Morvan, D.; Groussin, O.; Lamy, P.;
Biver, N.; Crovisier, J.; Colom, P.; Moreno, R.; Jorda, L.; Piétu, V.
2013A&A...557A..88B Altcode: 2013arXiv1307.8253B
Context. Little is known about the physical properties of the nuclei
of Oort Cloud comets. Measuring the thermal emission of a nucleus
is one of the few means for deriving its size and constraining some
of its thermal properties. <BR /> Aims: We attempted to measure the
nucleus size of the Oort Cloud comet C/2009 P1 (Garradd). <BR />
Methods: We used the Plateau de Bure Interferometer to measure the
millimetric thermal emission of this comet at 157 GHz (1.9 mm) and 266
GHz (1.1 mm). <BR /> Results: Whereas the observations at 266 GHz were
not usable due to bad atmospheric conditions, we derived a 3σ upper
limit on the comet continuum emission of 0.41 mJy at 157 GHz. Using a
thermal model for a spherical nucleus with standard thermal parameters,
we found an upper limit of 5.6 km for the radius. The dust contribution
to our signal is estimated to be negligible. Given the water production
rates measured for this comet and our upper limit, we estimated that
Garradd was very active, with an active fraction of its nucleus larger
than 50%. <P />Based on observations carried out with the IRAM Plateau
de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG
(Germany), and IGN (Spain).
---------------------------------------------------------
Title: THERMAP: the mid-infrared (8-16 µm) spectro-imager of the
ESA Marco Polo R mission
Authors: Groussin, O.; Licandro, J.; Helbert, J.; Alí Lagoa, V.;
Brageot, E.; Davidsson, B.; Delbó, M.; Delsanti, A.; Garcia-Talavera,
M. R.; Green, S.; Jorda, L.; Knollenberg, J.; Kührt, E.; Lamy, P.;
Lellouch, E.; Levacher, P.; Reynaud, J. -L.; Rozitis, B.; Sunshine,
J.; Vernazza, P.
2013EPSC....8..196G Altcode:
THERMAP is a mid-infrared (8-16 μm) spectroimager, selected by
the European Space Agency (ESA) in February 2013 for the scientific
payload of the Marco Polo R M-class mission. We present in this paper
the instrument and its scientific objectives.
---------------------------------------------------------
Title: Thermal properties, sizes, and size distribution of
Jupiter-family cometary nuclei
Authors: Fernández, Y. R.; Kelley, M. S.; Lamy, P. L.; Toth, I.;
Groussin, O.; Lisse, C. M.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.;
Fitzsimmons, A.; Licandro, J.; Lowry, S. C.; Meech, K. J.; Pittichová,
J.; Reach, W. T.; Snodgrass, C.; Weaver, H. A.
2013Icar..226.1138F Altcode: 2013arXiv1307.6191F
We present results from SEPPCoN, an on-going Survey of the Ensemble
Physical Properties of Cometary Nuclei. In this report we discuss
mid-infrared measurements of the thermal emission from 89 nuclei of
Jupiter-family comets (JFCs). All data were obtained in 2006 and 2007
using imaging capabilities of the Spitzer Space Telescope. The comets
were typically 4-5 AU from the Sun when observed and most showed only
a point-source with little or no extended emission from dust. For those
comets showing dust, we used image processing to photometrically extract
the nuclei. For all 89 comets, we present new effective radii, and for
57 comets we present beaming parameters. Thus our survey provides the
largest compilation of radiometrically-derived physical properties of
nuclei to date. We have six main conclusions: (a) The average beaming
parameter of the JFC population is 1.03 ± 0.11, consistent with unity;
coupled with the large distance of the nuclei from the Sun, this
indicates that most nuclei have Tempel 1-like thermal inertia. Only
two of the 57 nuclei had outlying values (in a statistical sense) of
infrared beaming. (b) The known JFC population is not complete even at
3 km radius, and even for comets that approach to ∼2 AU from the Sun
and so ought to be more discoverable. Several recently-discovered comets
in our survey have small perihelia and large (above ∼2 km) radii. (c)
With our radii, we derive an independent estimate of the JFC nuclear
cumulative size distribution (CSD), and we find that it has a power-law
slope of around -1.9, with the exact value depending on the bounds
in radius. (d) This power-law is close to that derived by others from
visible-wavelength observations that assume a fixed geometric albedo,
suggesting that there is no strong dependence of geometric albedo with
radius. (e) The observed CSD shows a hint of structure with an excess
of comets with radii 3-6 km. (f) Our CSD is consistent with the idea
that the intrinsic size distribution of the JFC population is not a
simple power-law and lacks many sub-kilometer objects.
---------------------------------------------------------
Title: The persistent activity of Jupiter-family comets at 3-7 AU
Authors: Kelley, Michael S.; Fernández, Yanga R.; Licandro, Javier;
Lisse, Carey M.; Reach, William T.; A'Hearn, Michael F.; Bauer,
James; Campins, Humberto; Fitzsimmons, Alan; Groussin, Olivier; Lamy,
Philippe L.; Lowry, Stephen C.; Meech, Karen J.; Pittichová, Jana;
Snodgrass, Colin; Toth, Imre; Weaver, Harold A.
2013Icar..225..475K Altcode: 2013arXiv1304.3818K
We present an analysis of comet activity based on the Spitzer Space
Telescope component of the Survey of the Ensemble Physical Properties
of Cometary Nuclei. We show that the survey is well suited to measuring
the activity of Jupiter-family comets at 3-7 AU from the Sun. Dust was
detected in 33 of 89 targets (37 ± 6%), and we conclude that 21 comets
(24 ± 5%) have morphologies that suggest ongoing or recent cometary
activity. Our dust detections are sensitivity limited, therefore
our measured activity rate is necessarily a lower limit. All comets
with small perihelion distances (q < 1.8 AU) are inactive in our
survey, and the active comets in our sample are strongly biased to
post-perihelion epochs. We introduce the quantity ɛfρ, intended to
be a thermal emission counterpart to the often reported Afρ, and find
that the comets with large perihelion distances likely have greater dust
production rates than other comets in our survey at 3-7 AU from the Sun,
indicating a bias in the discovered Jupiter-family comet population. By
examining the orbital history of our survey sample, we suggest that
comets perturbed to smaller perihelion distances in the past 150 yr
are more likely to be active, but more study on this effect is needed.
---------------------------------------------------------
Title: Photometric Calibration of the LASCO-C2 Coronagraph over 14
Years (1996 - 2009)
Authors: Gardès, B.; Lamy, P.; Llebaria, A.
2013SoPh..283..667G Altcode:
We present a photometric calibration of the SOHO/LASCO-C2 coronagraph
based on the analysis of all stars down to magnitude V=8 that transited
its field of view during the past 14 years of operation (1996 - 2009),
extending the previous work of Llebaria, Lamy, and Danjard (Icarus182,
281, 2006). The pre-processing of the images incorporates the most
recent determination of the evolution of the LASCO-C2 performances. The
automatic procedure then analyzes some 260 000 images to detect,
locate, and measure those stars. Aperture photometry is performed
using four different aperture sizes, and the zero points (ZPs)
of the photometric transformations between the LASCO-C2 magnitudes
for its orange filter and the standard V magnitudes are determined
after introducing a correction for the color of the stars. A new
statistical method ("bootstrap") is introduced to assess the confidence
intervals of the mean yearly value of the ZPs. The correction for finite
aperture required to derive the calibration coefficient for the surface
photometry of extended sources is based on the reconstructed image of
bright saturated stars and a robust model for the growth curve. The
global temporal evolution of the sensitivity of LASCO-C2 is compatible
with a continuous decrease at a rate of ≈ 0.56 % per year. However,
it is better described by two separate linear variations with a
discontinuity at the time of the loss of SOHO. After the resumption
of normal operations in 1999, the linear decrease of the sensitivity
amounts to ≈ 0.35 % per year.
---------------------------------------------------------
Title: Comet C/2012 S1 (Ison)
Authors: Li, Jian-Yang; Weaver, H. A.; Kelley, M. S.; Farnham, T. L.;
A'Hearn, M. F.; Knight, M. M.; Mutchler, M. J.; Lamy, P.; Toth, I.;
Yoshimoto, K.; Gonzalez, J. J.; Shurpakov, S.; Pilz, U.; Scarmato, T.
2013CBET.3496....1L Altcode: 2013CBET.3496....1W
Jian-Yang Li, Planetary Science Institute; H. A. Weaver, Applied Physics
Laboratory, Johns Hopkins University; M. S. Kelley, T. L. Farnham, and
M. F. A'Hearn, University of Maryland; M. M. Knight, Lowell Observatory;
M. J. Mutchler, Space Telescope Science Institute; P. Lamy, Laboratoire
d'Astrophysique de Marseille; and I. Toth, Hungarian Academy of
Sciences, obtained broadband images of comet C/2012 S1 (cf. CBET 3238)
on Apr. 10 (when at r = 4.15 AU and D = 4.24 AU) using the Hubble Space
Telescope (HST) WFC3/UVIS cameras with the F606W and F438W filters. The
observations were performed in three HST orbits, with the second orbit
about 2.5 hr after the first, and the last about 13.5 hr from the
second. Preliminary analysis using a coma-nucleus separation technique
(cf. Lamy et al. 2009, A.Ap. 508, 1045) suggests a nuclear radius less
than 2 km. The total brightness of the comet within a 0".24-diameter
aperture remained unchanged within 0.03 mag over the 19-hr observing
window. Broadband photometry yielded Af(rho) = 1376 cm at 589 nm, and
1281 cm at 433 nm, consistent with a red slope of 5 percent per 0.1
micron for the coma dust. A well-defined jet is visible after removing
the 1/r brightness distribution. The jet is centered on position angle
290 deg, with a cone angle of 45 deg, a projected length of 1".6, and a
slight curvature towards the north near the end. No temporal change in
the morphology is observed over the three epochs, suggesting that the
jet is circumpolar. Under this assumption, the jet's apparent position
constrains the rotational pole to lie within 30 deg of R.A. = 330 deg,
Decl. = 0 deg (equinox 2000.0). The images are posted at the following
website URL: http://hubblesite.org/newscenter/archive/releases/2013/14/.
Total-magnitude estimates (visual unless otherwise noted):
2012 Oct. 14.77 UT, 17.3 (K. Yoshimoto, Yamaguchi, Japan, 0.16-m
reflector + CCD); Dec. 19.82, 16.5 (Yoshimoto); 2013 Jan. 13.90, 14.8
(J. J. Gonzalez, Leon, Spain, 0.20-m reflector; visual); 21.85, 15.8
(S. Shurpakov, Baran', Belarus, 20-cm reflector + CCD); Feb. 2.90,
15.0 (U. Pilz, Leipzig, Germany, 32-cm reflector; visual); 11.57, 15.8
(Yoshimoto); 23.74, 15.8 (Shurpakov); Mar. 6.72, 15.5 (Shurpakov);
10.76, 16.1 (T. Scarmato, Calabria, Italy, 25-cm reflector + CCD +
R_c filter); 23.79, 15.8 (Scarmato); Apr. 6.82, 16.2 (Scarmato); 9.48,
15.8 (Yoshimoto); 19.81, 16.2 (Scarmato).
---------------------------------------------------------
Title: A new multiresolution method applied to the 3D reconstruction
of small bodies
Authors: Capanna, C.; Jorda, L.; Lamy, P. L.; Gesquiere, G.
2012AGUFM.P23B1937C Altcode:
The knowledge of the three-dimensional (3D) shape of small solar system
bodies, such as asteroids and comets, is essential in determining
their global physical properties (volume, density, rotational
parameters). It also allows performing geomorphological studies of
their surface through the characterization of topographic features,
such as craters, faults, landslides, grooves, hills, etc.. In the case
of small bodies, the shape is often only constrained by images obtained
by interplanetary spacecrafts. Several techniques are available to
retrieve 3D global shapes from these images. Stereography which relies
on control points has been extensively used in the past, most recently
to reconstruct the nucleus of comet 9P/Tempel 1 [Thomas (2007)]. The
most accurate methods are however photogrammetry and photoclinometry,
often used in conjunction with stereography. Stereophotogrammetry
(SPG) has been used to reconstruct the shapes of the nucleus of
comet 19P/Borrelly [Oberst (2004)] and of the asteroid (21) Lutetia
[Preusker (2012)]. Stereophotoclinometry (SPC) has allowed retrieving
an accurate shape of the asteroids (25143) Itokawa [Gaskell (2008)] and
(2867) Steins [Jorda (2012)]. We present a new photoclinometry method
based on the deformation of a 3D triangular mesh [Capanna (2012)]
using a multi-resolution scheme which starts from a sphere of 300
facets and yields a shape model with 100; 000 facets. Our strategy is
inspired by the "Full Multigrid" method [Botsch (2007)] and consists
in going alternatively between two resolutions in order to obtain an
optimized shape model at a given resolution before going to the higher
resolution. In order to improve the robustness of our method, we use
a set of control points obtained by stereography. Our method has been
tested on images acquired by the OSIRIS visible camera, aboard the
Rosetta spacecraft of the European Space Agency, during the fly-by of
asteroid (21) Lutetia in July 2010. We present the corresponding 3D
shape model of its surface and compare it with models obtained with
the SPG and SPC methods. We finally illustrate the practical interest
of our approach in geomorphological studies through an analysis of
depth to diameter ratio of several craters and topographic properties
of other features. Botsch, M., et al., "Geometric modeling based on
polygonal meshes," Proc. ACM SIGGRAPH Course Notes, 2007 Capanna,
C., et al.: 3D Reconstruction of small solar system bodies using
photoclinometry by deformation, IADIS International Journal on Computer
Science and Information Systems, in press, 2012. Gaskell, R. W., et
al.: Characterizing and navigating small bodies with imaging data,
Meteoritics and Planetary Science, vol 43, p. 1049, 2008. Jorda, L.,
et al: Asteroid (2867) Steins: Shape, Topography and Global Physical
Properties from OSIRIS observations, Icarus, in press, 2012. Oberst,
J., et al.: The nucleus of Comet Borrelly: a study of morphology
and surface brightness, Icarus, vol. 167, 2004. Preusker, F., et
al.: The northern hemisphere of asteroid 21 Lutetia topography and
orthoimages from Rosetta OSIRIS NAC image data, Planetary and Space
Science, vol. 66, p. 54-63, 2012. Thomas, P. C., et al.: The shape,
topography, and geology of Tempel 1 from Deep Impact observations,
Icarus, vol. 187, Issue 1, p. 4-15, 2007
---------------------------------------------------------
Title: Testing a Two-temperature Model of the Solar Corona with
Empirically-derived Plasma parameters
Authors: Strachan, L.; Panasyuk, A.; Lamy, P. L.; van der Holst, B.;
Oran, R.; Frazin, R. A.; Manchester, W. B.
2012AGUFMSH31B..04S Altcode:
We compare the plasma parameters predicted from the Michigan
two-temperature chromosphere-corona model to those parameters obtained
from the analyses of UVCS and LASCO data. The empirical data are
organized as Carrington rotation maps for the electron densities, proton
kinetic temperatures, and outflow velocities. This data format makes
it convenient for understanding the differences between the modeled and
observed latitudinal variations in the plasma parameters. In addition,
we discuss the model performance for characterizing streamers and
coronal holes at different phases in the solar activity cycle. These
tests are useful for investigating how well coronal and solar wind
models simulate the underlying physical processes that operate in the
solar corona.
---------------------------------------------------------
Title: Disk-resolved photometry of Asteroid (2867) Steins
Authors: Spjuth, S.; Jorda, L.; Lamy, P. L.; Keller, H. U.; Li, J. -Y.
2012Icar..221.1101S Altcode:
We present a new method to perform disk-resolved photometry in order
to investigate the intrinsic photometric properties of the surface
of small Solar System bodies. We adopt the standard approach where
a shape model is combined with a photometric formalism - in practise
the Hapke formalism - to remove the effects of topography and recover
the photometric (Hapke) parameters of either the global surface or, in
its most elaborated form, the spatial variations of these parameters
across the surface. Our method operates in the space of the facets
representing the three-dimensional shape of the body, whereas all past
analysis have always been performed in the space of the image pixels
although they are not intrinsic to the surface of the body. This has
the advantage of automatically tracking the same local surface element
on a series of images. We first apply our method to images of the
nucleus of Comet 9P/Tempel 1 obtained by the High-Resolution Imager
(HRI) instrument on board the Deep Impact spacecraft and our derived
Hapke parameters are in good agreement with those published by Li et
al. (Li, J.-Y. et al. [2007]. Icarus 187, 41-55) within their respective
uncertainties. We confirm the presence of an extended region of higher
roughness in the southern hemisphere of the nucleus and the higher
albedo of the ice-rich regions identified by Sunshine et al. (Sunshine,
J.M. et al. [2006]. Science 311, 1453-1455) near the equator. The
photometric properties of Asteroid (2867) Steins are then studied
from multi-spectral images obtained with the OSIRIS Wide Angle Camera
(WAC) on board the Rosetta spacecraft during its flyby on 5 September
2008. Our analysis indicates that the surface is highly porous (∼84%)
and that it exhibits both a shadow-hiding opposition effect (SHOE)
and probably, a coherent-backscatter opposition effect (CBOE). The
single scattering albedo is the highest (SSA = 0.57) ever observed among
small bodies visited by spacecrafts. Our modelled roughness parameter
is indicative of a high microscale roughness. The surface of Steins
may in fact exhibit a fractal surface with high roughness present on a
large range of scales, from micrometers to centimeters. The geometric
and Bond albedos are calculated with the Hapke parameters yielding
A<SUB>p</SUB> = 0.39 ± 0.02 and A<SUB>B</SUB> = 0.24 ± 0.01. This high
albedo is consistent with an iron-poor surface composition similar to
aubrite meteorites which are suspected to originate from the E-type
asteroids. We find no photometric variations on the surface at the
(limited) spatial resolution of the WAC images.
---------------------------------------------------------
Title: Asteroid (2867) Steins: Shape, topography and global physical
properties from OSIRIS observations
Authors: Jorda, L.; Lamy, P. L.; Gaskell, R. W.; Kaasalainen, M.;
Groussin, O.; Besse, S.; Faury, G.
2012Icar..221.1089J Altcode:
The Rosetta spacecraft flew by Asteroid (2867) Steins on 5 September
2008, allowing the onboard OSIRIS cameras to collect the first
images of an E-type asteroid. We implemented several three-dimensional
reconstruction techniques to retrieve its shape. Limb profiles, combined
with stereo control points, were used to reconstruct an approximate
shape model. This model was refined using a stereophotoclinometry
technique to accurately retrieve the topography of the hemisphere
observed by OSIRIS. The unseen part of the surface was constrained
by the technique of light curves inversion. <P />The global shape
resembles a top with dimensions along the principal axes of inertia
of 6.83 × 5.70 × 4.42 km. It is conspicuously more regular than
other small asteroids like (233) Eros and (25143) Itokawa. Its mean
radius is R<SUB>m</SUB> = 2.70 km and its equivalent radius (radius
of a sphere of equivalent volume) is R<SUB>v</SUB> = 2.63 km. The
north pole is oriented at RA = 99 ± 5° and Dec = -59 ± 5°, which
implies a very large obliquity of 172° and a retrograde rotation. <P
/>Maps of the gravitational field and slopes were calculated for the
well-imaged part of the asteroid. Together with the shape, they helped
characterizing the most prominent topographic features identified at
the surface of (2867) Steins: an equatorial ridge restricted to the
extremities of the long axis, a large crater having dimensions of
2100 × 1800 m in the southern hemisphere, and an elongated hill in
the northern hemisphere. We conjecture that the equatorial ridge was
formed by centrifugal acceleration as the asteroid was spun up by the
Yarkovsky-O’Keefe-Radzievskii-Paddack effect.
---------------------------------------------------------
Title: High surface porosity as the origin of emissivity features
in asteroid spectra
Authors: Vernazza, P.; Delbo, M.; King, P. L.; Izawa, M. R. M.;
Olofsson, J.; Lamy, P.; Cipriani, F.; Binzel, R. P.; Marchis, F.;
Merín, B.; Tamanai, A.
2012Icar..221.1162V Altcode:
Emission features in the mid-IR domain (7-25 μm) are quite ubiquitous
among large asteroids and therefore offer the potential to uncover
their surface composition. However, when comparing these spectra
with the actual laboratory spectra of both minerals and meteorites,
they do not necessarily match. Here, and in a companion paper by King
et al. (in preparation, 2012), we show that by modifying the sample
preparation - typically by suspending meteorite and/or mineral powder
(<30 μm) in IR-transparent KBr (potassium bromide) powder - we are
able to reproduce the spectral behavior of those main-belt asteroids
with emissivity features. This resulting good match between KBr-diluted
meteorite spectra and asteroid spectra suggests an important surface
porosity (>90%) for the first millimeter for our asteroid sample. It
therefore appears that mid-IR emission spectra of asteroids do not
only carry information about their surface composition but they can
also help us constraining their surface structure (under-dense versus
compact surface structure), as suggested by Emery et al. (Emery,
J.P., Cruikshank, D.P., van Cleve, J. [2006]. Icarus 182, 496-512) in
the case of the Jupiter Trojans. The large surface porosity inferred
from the mid-IR spectra of certain asteroids is also implied by two
other independent measurements, namely their thermal inertia and their
radar albedo. We further clarified how much compositional information
can be retrieved from the mid-IR range by focusing our analysis on a
single object, 624 Hektor. We showed that the mid-IR range provides
critical constraints (i) on its origin and of that of the red Trojans
that we locate in the formation regions of the comets, and (ii) on the
primordial composition of the dust present in the outer region (>10
AU) of the Solar System’s protoplanetary disk. Future investigations
should focus on finding the mechanism responsible for creating such
high surface porosity.
---------------------------------------------------------
Title: Identification and physical properties of craters on Asteroid
(2867) Steins
Authors: Besse, S.; Lamy, P.; Jorda, L.; Marchi, S.; Barbieri, C.
2012Icar..221.1119B Altcode:
We report on the physical properties of the craters of Asteroid
(2867) Steins based on an analysis of images obtained with the OSIRIS
instrument during the Rosetta flyby that took place on 5 September
2008. To compensate for the limited spatial resolution of the images
and unfavorable illumination conditions, we applied three different
filtering techniques designed to enhance the craters detection. The
selected images covered 44% of the overall surface of the asteroid and
42 craters were detected. We calculated their diameter and depth using
a forward modeling procedure that combines a global shape model with
an idealized semi-hemispherical representation of the craters, further
incorporating photometric properties to generate simulated images. The
resulting images were then compared to the original images. Crater
diameters range from 150 to 2100 m with depth-to-diameter ratios
of 0.04-0.25, a wide range consistent with other small bodies. A
striking dichotomy was observed between the two sides of the asteroid
reflected by both a ratio of 3.6 between the spatial density and
very different power exponents of the size distribution functions,
-3.3 versus -1.5. Altogether these peculiar properties most likely
reflect the particular history of Steins, in particular the impact
that created the largest crater, Diamond, and extensively damaged the
“original” Steins. A combination of various processes, including
destruction, erasure, direct or indirect infill by seismic shaking,
and even the YORP effect can explain the observed physical properties
of the craters on Steins. A few craters may be drainage basins connected
to a hypothetical fault, itself a product of the Diamond event.
---------------------------------------------------------
Title: Intercomparison of the LASCO-C2, SECCHI-COR1, SECCHI-COR2,
and Mk4 Coronagraphs
Authors: Frazin, Richard A.; Vásquez, Alberto M.; Thompson, William
T.; Hewett, Russell J.; Lamy, Philippe; Llebaria, Antoine; Vourlidas,
Angelos; Burkepile, Joan
2012SoPh..280..273F Altcode: 2012SoPh..tmp..140F
In order to assess the reliability and consistency of white-light
coronagraph measurements, we report on quantitative comparisons between
polarized brightness [pB] and total brightness [B] images taken by
the following white-light coronagraphs: LASCO-C2 on SOHO, SECCHI-COR1
and -COR2 on STEREO, and the ground-based MLSO-Mk4. The data for this
comparison were taken on 16 April 2007, when both STEREO spacecraft were
within 3.1<SUP>∘</SUP> of Earth's heliographic longitude, affording
essentially the same view of the Sun for all of the instruments. Due
to the difficulties of estimating stray-light backgrounds in COR1 and
COR2, only Mk4 and C2 produce reliable coronal-hole values (but not
at overlapping heights), and these cannot be validated without rocket
flights or ground-based eclipse measurements. Generally, the agreement
between all of the instruments' pB values is within the uncertainties
in bright streamer structures, implying that measurements of bright
CMEs also should be trustworthy. Dominant sources of uncertainty and
stray light are discussed, as is the design of future coronagraphs
from the perspective of the experiences with these instruments.
---------------------------------------------------------
Title: Multi Element Telescope for Imaging and Spectroscopy (METIS)
coronagraph for the Solar Orbiter mission
Authors: Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero;
Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Nicolosi,
Piergiorgio; Abbo, Lucia; Andretta, Vincenzo; Bemporad, Alessandro;
Auchère, Frédéric; Berlicki, Arkadiusz; Bruno, Roberto; Capobianco,
Gerardo; Ciaravella, Angela; Crescenzio, Giuseppe; Da Deppo, Vania;
D'Amicis, Raffaella; Focardi, Mauro; Frassetto, Fabio; Heinzel,
Peter; Lamy, Philippe L.; Landini, Federico; Massone, Giuseppe;
Malvezzi, Marco A.; Moses, J. Dan; Pancrazzi, Maurizio; Pelizzo,
Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.;
Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela
2012SPIE.8443E..09A Altcode:
METIS, the “Multi Element Telescope for Imaging and Spectroscopy”,
is a coronagraph selected by the European Space Agency to be part of
the payload of the Solar Orbiter mission to be launched in 2017. The
unique profile of this mission will allow 1) a close approach to the
Sun (up to 0.28 A.U.) thus leading to a significant improvement in
spatial resolution; 2) quasi co-rotation with the Sun, resulting in
observations that nearly freeze for several days the large-scale outer
corona in the plane of the sky and 3) unprecedented out-of-ecliptic
view of the solar corona. This paper describes the experiment concept
and the observational tools required to achieve the science drivers
of METIS. METIS will be capable of obtaining for the first time: •
simultaneous imaging of the full corona in polarized visible-light
(590-650 nm) and narrow-band ultraviolet HI Lyman α (121.6 nm); •
monochromatic imaging of the full corona in the extreme ultraviolet
He II Lyman α (30.4 nm); • spectrographic observations of the HI
and He II Ly α in corona. These measurements will allow a complete
characterization of the three most important plasma components of
the corona and the solar wind, that is, electrons, hydrogen, and
helium. This presentation gives an overview of the METIS imaging and
spectroscopic observational capabilities to carry out such measurements.
---------------------------------------------------------
Title: In-orbit determination of the straylight in the SOHO/LASCO-C2
coronagraph and its temporal evolution
Authors: Llebaria, A.; Loirat, J.; Lamy, P.
2012SPIE.8442E..26L Altcode:
The LASCO-C2 coronagraph aboard SOHO (the SOlar and Heliospheric
Observatory) is continuously observing the solar corona since early
1996. The instrument as well as the experimental context underwent
during this period many changes and observational constraints. The
consequences for the in-orbit calibration procedures are illustrated
with the systematic measure of the coronagraph straylight. Disentangle
the coronal signal and the straylight is the crucial point. The
separation and monitoring of the straylight component rely on the
daily sets of polarized observations of the corona and a minimal set
of assumptions about the symmetry of the F-corona (the dust component
of the solar corona). Four main changes have been detected since
1996. Specific recommendations for the in-orbit calibration of future
spatial coronagraphs will be presented.
---------------------------------------------------------
Title: THERMAP : a mid-infrared spectro-imager for the Marco Polo
R mission
Authors: Groussin, O.; Brageot, E.; Reynaud, J. -L.; Lamy, P.; Jorda,
L.; Licandro, J.; Helbert, J.; Knollenberg, J.; Kührt, E.; Delbó, M.
2012epsc.conf...48G Altcode: 2012espc.conf...48G
We present THERMAP, a mid-infrared (8-16 μm) spectro-imager based
on uncooled micro-bolometer detector arrays. Due to the recent
technological development of these detectors, which have undergone
significant improvements in the last decade, we wanted to test
their performances for a space mission to small bodies in the inner
Solar System. THERMAP was selected by ESA in January 2012 for a one
year assessment study, in the framework of a call for declaration
of interest in science instrumentation for the Marco Polo R Cosmic
Vision mission. In this paper, we present some results of this study
and in particular demonstrate that the new generation of uncooled
micro-bolometer detectors has all the imaging and spectroscopic
capabilities to fulfill the scientific objectives of the Marco
Polo R mission. THERMAP scientific objectives - The midinfrared
instrument of the Marco Polo R mission must be able i) to determine
the surface temperature by mapping the entire surface with an absolute
accuracy of at least 5 K (goal 1 K) above 200 K, ii) to determine
the thermal inertia with an accuracy of 10% and iii) to determine
the surface composition by mapping the entire surface with a spectral
resolution of 70 between 8 and 16 μm. The above mappings should be
performed with a spatial resolution of 10 m for the entire surface
(global characterization) and 10 cm for the sampling sites (local
characterization). THERMAP imaging capabilities - In order to test the
imaging capabilities of the THERMAP uncooled microbolometer detector,
we set up an experiment based on a 640x480 ULIS micro-bolometer array,
a germanium objective and a black body. Using the results of this
experiment, we show that calibrated radiometric images can be obtained
down to at least 258 K (lower limit of our experiment), and that two
calibration points are sufficient to determine the absolute scene
temperature with an accuracy better than 1.5 K. An extrapolation to
lower temperatures provides an accuracy of about 5 K at 180 K, the
lowest temperature the detector can measure. THERMAP spectroscopic
capabilites - In order to test the spectroscopic performances of the
detector, we added flux attenuating neutral density mid-infrared filters
(transmittance: 50%, 10%, 1%) to our experiment. Our results show that
we can perform spectroscopic measurements with a spectral resolution
R=40-80 in the wavelength range 8-16 μm for a scene temperature larger
than 300 K, the typical surface temperature of a Near Earth Asteroid
at 1 AU from the Sun. THERMAP preliminary design - From the above
results, we defined a preliminary design for the instrument. THERMAP
is a mid-infrared (8-16 μm) spectro-imager based on two uncooled
microbolometer arrays. It is composed of two channels, one for imaging
and one for spectroscopy. A flip mirror allows switching between the
two channels. Calibration is performed using deep space and two black
bodies at known temperature. The design of the THERMAP instrument has a
strong heritage from the MERTIS instrument on board Bepi-Colombo [1],
which guarantees its feasibility and reliability. Our design is very
flexible in term of operations, which is fundamental for a mission
to a binary asteroid system (1996 FG3). The THERMAP instrument will
be proposed for Marco Polo R and any future space missions to small
bodies in the inner solar system.
---------------------------------------------------------
Title: THERMAP: a mid-infrared spectro-imager based on an uncooled
micro-bolometer for space missions to small bodies of the solar system
Authors: Brageot, E.; Groussin, O.; Lamy, P.; Reynaud, J. -L.; Fargant,
G.; Licandro, J.; Helbert, J.; Knollenberg, J.; Kührt, E.
2012SPIE.8442E..4OB Altcode:
We report on the feasibility study of a mid-infrared (8-18 µm)
spectro-imager called THERMAP, based on an uncooled micro-bolometer
detector array. Due to the recent technological development of these
detectors, which have undergone significant improvements in the last
decade, we wanted to test their performances for the Marco Polo R
ESA Cosmic Vision mission. In this study, we demonstrate that the new
generation of uncooled micro-bolometer detectors has all the imaging and
spectroscopic capabilities to fulfill the scientific objectives of this
mission. In order to test the imaging capabilities of the detector,
we set up an experiment based on a 640x480 ULIS micro-bolometer
array, a germanium objective and a black body. Using the results of
this experiment, we show that calibrated radiometric images can be
obtained down to at least 255 K (lower limit of our experiment), and
that two calibration points are sufficient to determine the absolute
scene temperature with an accuracy better than 1.5 K. Adding flux
attenuating neutral density mid-infrared filters (transmittance: 50%,
10%, 1%) to our experiment, we were able to evaluate the spectroscopic
performances of the detector. Our results show that we can perform
spectroscopic measurements in the wavelength range 8-16 µm with a
spectral resolution of R~40-80 for a scene temperature <300 K,
the typical surface temperature of a Near Earth Asteroid at 1 AU from
the Sun. The mid-infrared spectro-imager THERMAP, based on the above
detector, is therefore well suited for the Marco Polo R mission.
---------------------------------------------------------
Title: Lutetia global shape and topography reconstructed with
photoclinometry by deformation
Authors: Capanna, C.; Jorda, L.; Gesquière, G.; Lamy, P.; Kaasalainen,
M.
2012epsc.conf..616C Altcode: 2012espc.conf..616C
3D reconstruction of asteroids and cometary nuclei allows us to model
their physical, geomorphological and geological properties. We applied a
new reconstruction method by photoclinometry based on the minimization
of the chi-square difference between observed and synthetic images by
deformation of a 3D triangular mesh to a set of images of asteroid (21)
Lutetia acquired by the OSIRIS cameras aboard ESA's ROSETTA spacecraft
in July 2010. This allowed us to retrieve an improved global shape
of the asteroid as well as the local topography of its main features:
the large Massalia crater, the North pole crater complex and several
other topographic features of interest. A comparison of this model
with those obtained with other techniques will be presented.
---------------------------------------------------------
Title: Sunskirting comets discovered with the LASCO coronagraphs
(1996-2008)
Authors: Lamy, P.; Faury, G.; Llebaria, A.; Knight, M.; A'Hearn, M.
2012epsc.conf..308L Altcode: 2012espc.conf..308L
In addition to an unprecedented number of Kreutz sungrazing comets,
the LASCO coronagraphs aboard SOHO have discovered some 238 unrelated
"sunskirting" comets from 1996 to 2008. This new family is organized
in several groups, and two comets have further been found periodic. We
present the photometry and the heliocentric light curves of these
sunskirting comets. The bulk of them exhibit a continuous increase
of the brightness as the comet approaches, reaching a peak before
perihelion and then progressively fading with a large variety of
brightness gradients. However, some of them have peak brightness either
at or post-perihelion whereas a quite large number are approximately
flat. We finally characterize the different groups of sunskirters
on the basis of their distribution of peak magnitudes and of their
fragmentation history.
---------------------------------------------------------
Title: A portrait of the asteroid (21) Lutetia after the Rosetta flyby
Authors: Jorda, Laurent; Thomas, Nicolas; Scholten, Frank; Preusker,
Frank; Gaskell, Robert; Lamy, Philippe; Marchi, Simone; Vernazza,
Pierre; Carry, Benoit; Hviid, Stubbe; Sierks, Holger; Keller, Horst
Uwe; Kaasalainen, Mikko
2012cosp...39..836J Altcode: 2012cosp.meet..836J
The asteroid (21) Lutetia has been observed by several instruments
aboard ESA's ROSETTA spacecraft on July 10, 2010. The OSIRIS imaging
system allowed the reconstruction of the topography of its surface. A
number of intriguing features appeared on the images and/or on the
topographic models: boulders, landslides, craters with various profiles,
among others. The combination of these data with light curves and
adaptive optics profiles allowed to retrieve the global shape of the
asteroid, which yielded an estimate of its volume. Combined with the
accurate mass determination from the radio science RSI instrument,
a very high density of 3.4 g/cm^{3} was obtained.
---------------------------------------------------------
Title: Plasmoid Ejection at a Solar Total Eclipse
Authors: Koutchmy, S.; Bazin, C.; Berghmans, D.; De Groof, A.;
Druckmüller, M.; Tavabi, E.; Engell, A.; Filippov, B.; Golub, L.;
Lamy, Ph.; Linker, J.; Mikic, Z.; Mouette, J.; Nitschelm, Ch.; Seaton,
D.; Slemzin, V.
2012EAS....55..223K Altcode:
The existence of coronal plasmoids has been postulated for many years
in order to supply material to streamers and possibly to the solar
wind (SW). The W-L SoHO C2 Lasco coronagraph observations were made
under the 2.2 solar radii (R0) occulting disk to look at the ultimate
sources of the SW; EUV imagers are preferably devoted to the analysis
of the corona on and very near the solar disk. Here, in addition to
eclipse white-light (W-L) snapshots, we used the new SWAP space-borne
imager designed for the systematic survey of coronal activity in the
EUV lines near 17.4 nm, over a field of view (FOV) up to 2 R0. Using
summed and co-aligned images, the corona can then be evaluated for the
1st time up to the limit of this FOV. At the time of the July 11, 2010,
solar total eclipse a 20h continuous run of observations was collected,
including images taken during eclipse totality from several ground
observing locations where W-L data were collected. A plasmoid-like
off-limb event was followed using the SWAP summed
---------------------------------------------------------
Title: Shape modeling technique KOALA validated by ESA Rosetta at
(21) Lutetia
Authors: Carry, B.; Kaasalainen, M.; Merline, W. J.; Müller, T. G.;
Jorda, L.; Drummond, J. D.; Berthier, J.; O'Rourke, L.; Ďurech,
J.; Küppers, M.; Conrad, A.; Tamblyn, P.; Dumas, C.; Sierks, H.;
Osiris Team; A'Hearn, M.; Angrilli, F.; Barbieri, C.; Barucci, A.;
Bertaux, J. -L.; , Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei,
S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez,
P.; Ip, W. -H. Hviid, S.; Keller, H. U.; Koschny, D.; Knollenberg,
J.; Kramm, J. R.; Kuehrt, E.; Lamy, P.; Lara, L. M.; Lazzarin, M.;
López-Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Rickman,
H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Wenzel, K. -P.
2012P&SS...66..200C Altcode: 2011arXiv1112.5944C; 2012P&SS...66..200T
We present here a comparison of our results from ground-based
observations of asteroid (21) Lutetia with imaging data acquired during
the flyby of the asteroid by the ESA Rosetta mission. This flyby
provided a unique opportunity to evaluate and calibrate our method
of determination of size, 3-D shape, and spin of an asteroid from
ground-based observations. Knowledge of certain observable physical
properties of small bodies (e.g., size, spin, 3-D shape, and density)
have far-reaching implications in furthering our understanding
of these objects, such as composition, internal structure, and
the effects of non-gravitational forces. We review the different
observing techniques used to determine the above physical properties
of asteroids and present our 3-D shape-modeling technique KOALA
- Knitted Occultation, Adaptive-optics, and Lightcurve Analysis -
which is based on multi-dataset inversion. We compare the results we
obtained with KOALA, prior to the flyby, on asteroid (21) Lutetia with
the high-spatial resolution images of the asteroid taken with the OSIRIS
camera on-board the ESA Rosetta spacecraft, during its encounter with
Lutetia on 2010 July 10. The spin axis determined with KOALA was found
to be accurate to within 2°, while the KOALA diameter determinations
were within 2% of the Rosetta-derived values. The 3-D shape of the
KOALA model is also confirmed by the spectacular visual agreement
between both 3-D shape models (KOALA pre- and OSIRIS post-flyby). We
found a typical deviation of only 2 km at local scales between the
profiles from KOALA predictions and OSIRIS images, resulting in a volume
uncertainty provided by KOALA better than 10%. Radiometric techniques
for the interpretation of thermal infrared data also benefit greatly
from the KOALA shape model: the absolute size and geometric albedo
can be derived with high accuracy, and thermal properties, for example
the thermal inertia, can be determined unambiguously. The corresponding
Lutetia analysis leads to a geometric albedo of 0.19±0.01 and a thermal
inertia below 40 J m<SUP>-2</SUP> s<SUP>-0.5</SUP> K<SUP>-1</SUP>, both
in excellent agreement with the Rosetta findings. We consider this to be
a validation of the KOALA method. Because space exploration will remain
limited to only a few objects, KOALA stands as a powerful technique to
study a much larger set of small bodies using Earth-based observations.
---------------------------------------------------------
Title: Geological map and stratigraphy of asteroid 21 Lutetia
Authors: Massironi, Matteo; Marchi, Simone; Pajola, Maurizio;
Snodgrass, Colin; Thomas, Nicolas; Tubiana, Cecilia; Baptiste Vincent,
Jean; Cremonese, Gabriele; da Deppo, Vania; Ferri, Francesca; Magrin,
Sara; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rickman,
Hans; Rodrigo, Rafael; Koschny, Detlef; Osiris Team
2012P&SS...66..125M Altcode: 2012P&SS...66..125T
The OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System)
images acquired during the recent Rosetta fly-by of Lutetia (10th of
July 2010), enabled us to unravel the long geological history of the
asteroid. This is recorded on its highly varied surface which displays
geological units of disparate ages. In particular, using images of
the closest approach, five main regions (in turn subdivided into
minor units) have been discriminated on the basis of crater density,
overlapping and cross-cutting relationships, and presence of linear
features (i.e., fractures, faults, grooves, troughs). Other regions,
with still unclear stratigraphic position, were also recognized on
images of lower resolution on the bases of geomorphological properties
such as crater density, relationship with scarp and ridges, and sharp
morphological boundaries. In this work the geological evolution of
Lutetia surface is reconstructed through the description of its main
units and related contacts. The oldest regions imaged during the closest
approach (Achaia and Noricum) are pervasively affected by fractures
and grooves and display surfaces so heavily cratered to be dated back
to a period not far from the Late Heavy Bombardment (yielding Achaia
a crater retention age of 3.6-3.7 Ga). A crater of 55 km diameter,
named Massilia and corresponding to the Narbonensis region, cuts both
Achaia and Noricum regions and probably represents the most prominent
event of the Lutetia history. The considerable crater density on its
floor and walls, the absence of discernable deposits related to the
impact event, and the intense deformation of it floor - all attest to
its relatively great age. The North Polar Cluster (Baetica region) is
associated with smooth ejecta broadly mantling the surrounding units
and displays few craters and no linear features, demonstrating its
relatively young age (estimated at less than 300 Ma). The North Polar
Crater Cluster is the product of superimposed impacts; the last one of
24 km of diameter excavated the pre-existing ejecta up to the bedrock
which locally outcrops at the crater rim. The ejecta of this last impact
were involved in several gravitational phenomena testified by the great
variety of deposits made up of mega-boulders diamictons, fine materials,
gravitational taluses and debris, and landslide accumulations. A part
from the big cratering events generating Massilia and the North Polar
Crater Cluster, the Lutetia geological history is also punctuated by
minor events still recorded by its stratigraphic record well imaged
by the closest approach data.
---------------------------------------------------------
Title: The geomorphology of (21) Lutetia: Results from the OSIRIS
imaging system onboard ESA's Rosetta spacecraft
Authors: Thomas, N.; Barbieri, C.; Keller, H. U.; Lamy, P.; Rickman,
H.; Rodrigo, R.; Sierks, H.; Wenzel, K. P.; Cremonese, G.; Jorda, L.;
Küppers, M.; Marchi, S.; Marzari, F.; Massironi, M.; Preusker, F.;
Scholten, F.; Stephan, K.; Barucci, M. A.; Besse, S.; El-Maarry, M. R.;
Fornasier, S.; Groussin, O.; Hviid, S. F.; Koschny, D.; Kührt, E.;
Martellato, E.; Moissl, R.; Snodgrass, C.; Tubiana, C.; Vincent, J. -B.
2012P&SS...66...96T Altcode:
The surface of (21) Lutetia is highly complex with significant
interactions between ancient and more recent structures. This work
attempts to summarize the surface geomorphology observed using the
high resolution images from OSIRIS, the imaging system onboard the
European Space Agency's Rosetta spacecraft. A wide range of surface
morphologies are seen including heavily cratered terrain, extensive
sets of lineaments, young impact craters, and a ridge, the height
of which is more than 1/5th of the mean radius of the body. Very
young and very old terrains (as inferred from crater densities) are
seen in close proximity. The longest continuous lineament is over
80 km long. The lineaments show regional-dependent organization and
structure. Several categories of lineament can be described. Lineaments
radial to impact craters as seen on other asteroidal bodies are mostly
absent. Although the lineaments may be of seismic origin (and possibly
the result of several impact-induced events), impacts producing recent
large craters place constraints on seismic phenomena. In particular,
stronger attenuation of shocks than seen on other asteroidal bodies
seems to be required. Inhomogeneous energy transport, possibly matching
observed inhomogeneous ejecta deposition may offer explanations for
some of the observed phenomena. Some impact craters show unusual
forms, which are probably the result of impact into a surface with
relief comparable to the resultant crater diameter and/or oblique
impact. There is evidence that re-surfacing through landslides has
occurred at several places on the object.
---------------------------------------------------------
Title: Boulders on Lutetia
Authors: Küppers, Michael; Moissl, Richard; Vincent, Jean-Baptiste;
Besse, Sébastien; Hviid, Stubbe F.; Carry, Benoît; Grieger, Björn;
Sierks, Holger; Keller, Horst Uwe; Marchi, Simone; OSIRIS Team;
A'Hearn, M.; Angrilli, F.; Barbieri, C.; Barucci, A.; Bertaux, J. -L.;
Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.;
Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P.; Ip, W. -H.,
Jorda, L., Koschny, D.; Knollenberg, J.; Kramm, J. R.; Kührt, E.;
Lamy, P.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari,
F.; Michalik, H. Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.;
Thomas, N.; Wenzel, K. -P.
2012P&SS...66...71K Altcode: 2012P&SS...66...71T
More than 200 boulders are among the many prominent geological
features seen on Lutetia by the OSIRIS cameras onboard Rosetta. Most
are concentrated around the central crater in Baetica regio with
a few more apparently associated with Patavium crater. The size
range of boulders visible to OSIRIS is about 60-300 m. We model the
trajectories of boulders ejected from the central crater and show that
their distribution is consistent with most of them being created from
that crater, similar to the situation on asteroid Eros where most
of the boulders are believed to originate from Shoemaker crater. We
evaluate various destruction mechanisms for ejecta blocks and conclude
that, using current estimates of the number of small asteroids in the
main belt, destruction by impacts of small (several meters diameter)
projectiles limits the lifetime of the boulders (and the age of the
central crater) to a maximum of 300 million years. Since several
analyses of crater ages and size distributions also come up with
surprisingly young ages, the size-frequency distribution of small
main-belt asteroids (below the size currently reached by surveys)
may warrant to be revisited.
---------------------------------------------------------
Title: (21) Lutetia spectrophotometry from Rosetta-OSIRIS images
and comparison to ground-based observations
Authors: Magrin, S.; La Forgia, F.; Pajola, M.; Lazzarin, M.;
Massironi, M.; Ferri, F.; da Deppo, V.; Barbieri, C.; Sierks, H.;
Osiris Team; A'Hearn, M.; Angrilli, F.; Barucci, A.; Bertaux, J. -L.;
Cremonese, G.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier,
S.; Fulle, M.; Groussin, O.; Gutiérrez, P.; Hviid, S.; Ip, W. -H.;
Jorda, L.; Keller, H. U.; Knollenberg, J.; Koschny, D.; Kramm, J. R.;
Kuehrt, E.; Küppers, M.; Lamy, P.; Lara, L. M.; López-Moreno, J. J.;
Marzari, F.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.;
Sabau, L.; Thomas, N.; Weissman, P. R.; Wenzel, K. -P.
2012P&SS...66...43M Altcode: 2012P&SS...66...43T
Here we present some preliminary results on surface variegation found
on (21) Lutetia from ROSETTA-OSIRIS images acquired on 2010-07-10. The
spectrophotometry obtained by means of the two cameras NAC and WAC
(Narrow and Wide Angle Cameras) is consistent with ground based
observations, and does not show surface diversity above the data error
bars. The blue and UV images (shortward 500 nm) may, however, indicate
a variegation of the optical properties of the asteroid surface on
the Baetica region (Sierks et al., 2011). We also speculate on the
contribution due to different illumination and to different ground
properties (composition or, more probably, grain size diversity). In
particular a correlation with geologic units independently defined by
Massironi et al. (2012) is evident, suggesting that the variegation
of the ground optical properties is likely to be real.
---------------------------------------------------------
Title: Physical properties of craters on asteroid (21) Lutetia
Authors: Vincent, Jean-Baptiste; Besse, Sébastien; Marchi, Simone;
Sierks, Holger; Massironi, Matteo; OSIRIS Team; A'Hearn, M.; Angrilli,
F.; Barbieri, C.; Barucci, A.; Bertaux, J. -L.; Cremonese, G.; Da
Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.;
Fulle, M.; Groussin, O.; Gutierrez, P.; Hviid, S. F.; Ip, W. -H.;
Jorda, L.; Keller, H. U.; Koschny, D.; Knollenberg, J.; Kramm, J. R.;
Kuehrt, E.; Lamy, P.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.;
Marzari, F.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.;
Sabau, L.; Thomas, N.; Wenzel, K. -P.
2012P&SS...66...79V Altcode: 2012P&SS...66...79T
This paper presents an analysis of the physical properties of craters
on asteroid (21) Lutetia, derived from images acquired by OSIRIS,
the high-resolution cameras onboard ESA's spacecraft Rosetta. Crater
morphology on (21) Lutetia fits very well with the general picture
of what was known for previously visited small bodies, with a typical
depth to diameter ratio of 0.12. We discuss here the distribution of
this parameter all across the surface, but also region by region, and
see how it can vary from one location to another and help to distinguish
between different geological units. In a later section of the paper
we study in more details Beatica region where a deep ejecta blanket
filled most of the craters, and estimate the thickness profile of this
ejecta based on our analysis of the d/D. We find a good agreement
with existing scaling laws, and use this to constrain the scale of
the original event that reshaped the surface around the North pole of
the asteroid. Finally, we report on the observations of avalanches in
several crater flanks, and the presence of many asymmetrical craters
with flow-like features, and discuss the evidence for widespread fine
material all over the surface.
---------------------------------------------------------
Title: Search for satellites near (21) Lutetia using OSIRIS/Rosetta
images
Authors: Bertini, Ivano; Sabolo, Walter; Gutierrez, Pedro J.;
Marzari, Francesco; Snodgrass, Colin; Tubiana, Cecilia; Moissl,
Richard; Pajola, Maurizio; Lowry, Stephen C.; Barbieri, Cesare; Ferri,
Francesca; Davidsson, Björn; Sierks, Holger; OSIRIS Team; A'Hearn, M.;
Angrilli, F.; Barucci, A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo,
V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.;
Hviid, S.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.;
Koschny, D.; Kramm, J. R.; Kuehrt, E.; Küppers, M.; Lamy, P.; Lara,
L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Michalik, H.; Naletto, G.;
Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Wenzel, K. -P.
2012P&SS...66...64B Altcode: 2012P&SS...66...64T
On 2010 July 10 the ESA Rosetta mission flew by the large asteroid
(21) Lutetia. One of the scientific goals of the onboard OSIRIS
instrument was the search for satellites of the asteroid, with more
than 20 images specifically dedicated to this topic. An observational
campaign was devised with a selection of filters and exposure times
tailored to maximize the possibility of detecting small companions
and determining their bound orbits. Data were analyzed with suitable
methods to remove cosmic ray hits and known background objects, in
order to search for persistent detections of potential interesting
flux sources. We found no unambiguous detections of a satellite larger
than ∼160m inside the entire sphere of gravitational influence. Our
search confirmed the absence of bound companions larger than ∼30m
inside 20 primary radii. These limits are a factor of ∼30 smaller
than the values reported so far from large ground-based telescopes
using adaptive optics and from the Hubble Space Telescope.
---------------------------------------------------------
Title: ESCAPE : a first step to high resolution solar coronagraphy
in Antarctica
Authors: Damé, L.; Abe, L.; Faurobert, M.; Fineschi, S.; Kuzin, S.;
Lamy, P.; Meftah, M.; Vives, S.
2012EAS....55..359D Altcode:
The Dome C high plateau is unique for coronagraphic observations: sky
brightness is reduced, water vapour is low, seeing is excellent and
continuity of observations on several weeks is possible. ESCAPE (the
Extreme Solar Coronagraphy Antarctic Program Experiment) will perform
2-dimensional spectroscopy of the forbidden line of FeXIV at 530.285 nm:
precise line profile analysis will allow the diagnostic of the nature
of waves by simultaneous measurements of velocities and intensities in
the corona. ESCAPE is proposed to Institut Paul-Emile Victor (IPEV)
for a campaign in 2012-2013 at Dome C/Concordia since all subsystems
are available in particular thanks to an ESA STARTIGER 2010 R&D
"Toward a New Generation of Formation Flying Coronagraph". Using
state-of-the-art technologies developed for Space missions (a
Three Mirrors Anastigmat telescope, the TMA, a 4 stages Liquid
Crystal Tunable-filter Polarimeter, the LCTP) allows us to propose
an automated Coronal Green Line full-field Polarimeter for unique
observations (waves nature and intensity to address coronal heating)
with the best possible performances on Earth and for preparing and
testing the technologies for the next steps in Space. No other site
would allow such coronagraphic performances (the sky brightness is a
factor 2 to 4 better than in Hawaï) and with high spatial resolution
(better than an arcsec is possible).
---------------------------------------------------------
Title: High Surface Porosity as the Origin of Emissivity Features
in Asteroid Spectra
Authors: Vernazza, P.; Delbo, M.; King, P. L.; Izawa, M. R. M.;
Olofsson, J.; Lamy, P.; Cipriani, F.; Binzel, R. P.; Marchis, F.;
Merin, B.; Tamanai, A.
2012LPICo1667.6049V Altcode:
Here we show that mid-IR emission spectra of asteroids do not only
carry information about their surface composition but they can also
help us constraining their surface structure (under-dense versus
compact surface structure).
---------------------------------------------------------
Title: Visible-Wavelength Survey of Jupiter-Family Cometary Nuclei
as Part of SEPPCoN
Authors: Fernandez, Y. R.; Lowry, S. C.; Meech, K. J.; Laird, R.;
Fitzsimmons, A.; Snodgrass, C.; Weissman, P. R.; Pittichova, J.;
Bauer, J. M.; Weaver, H. A.; Lisse, C. M.; A'Hearn, M. F.; Campins,
H.; Groussin, O.; Kelley, M. S.; Lamy, P. L.; Licandro, J.; Toth,
I.; Reach, W. T.
2012LPICo1667.6488F Altcode:
We present observations of a statistically-significant number of
Jupiter-family cometary nuclei as part of SEPPCoN (Survey of the
Ensemble Physical Properties of Cometary Nuclei). We present preliminary
results on distributions of albedos and shapes.
---------------------------------------------------------
Title: The Trojans' Odyssey Space Mission
Authors: Lamy, P.; Vernazza, P.; Groussin, O.; Poncy, J.; Martinot,
V.; Hinglais, E.; Bell, J.; Cruikshank, D.; Helbert, J.; Marzari,
F.; Morbidelli, A.; Rosenblatt, P.
2012LPICo1667.6443L Altcode:
The proposed Trojans' Odyssey mission is envisioned as a reconnaissance,
multiple flyby mission aimed at visiting several objects, typically
five Trojans and one Hilda.
---------------------------------------------------------
Title: Asteroid (21) Lutetia: Global and Spatially Resolved
Photometric Properties
Authors: Lamy, P.; Jorda, L.; Vernazza, P.; Faury, G.
2012LPICo1667.6442L Altcode:
We will present results on the global photometric properties of (21)
Lutetia, as well as spatially resolved properties based on the Hapke
formalism.
---------------------------------------------------------
Title: The Geomorphology of Asteroid 21 Lutetia from In-Situ Imaging
Authors: Jorda, L.; Thomas, N.; Lamy, P.
2012LPICo1667.6406J Altcode:
We present an overview of the surface geomorphology of asteroid 21
Lutetia observed using the high resolution images from OSIRIS, the
imaging system onboard the European Space Agency’s Rosetta spacecraft.
---------------------------------------------------------
Title: Comet 8P/Tuttle: A portrait of a contact-binary nucleus from
Hubble and Spitzer space telescopes observations
Authors: Lamy, P.; Toth, I.; Jorda, L.; Groussin, O.; Faury, G.;
Weaver, H.
2012EGUGA..1410506L Altcode:
We detected the nucleus of comet 8P/Tuttle, a nearly-isotropic comet
(NIC) in a 13.5~yr orbital period, during its 2007--2008 close
(0.25~AU) Earth encounter with the Planetary Camera 2 of the Hubble
Space Telescope(HST on 10-11 December 2007 and with the infrared
camera (MIPS) of the Spitzer Space Telescope (SST) on 22-23 June 2008,
sampling the rotational period of the nucleus. We determined a synodic
rotational period of 11.40 +/-0.12 h and, by combining with the radar
observations of Harmon et al. (2010), a sidereal rotation period
of 11.444 +/-0.001h. The visible and thermal light curve exhibit a
complex shape best modeled by a contact-binary as evidenced by the radar
observations. By combining these light curves and adding a constraint on
the thermal inertia coming from millimetric observations at the Plateau
de Bure Observatory, we determined the shape and size of the binary
system approximated by two spheres in contact with respective radius
of 2.56 and 1.1 km, a common albedo in the range 0.04 to 0.054 and
a linear phase coefficient in the range 0.033 to 0.04 mag/deg. These
results suggest a strong similarity of the properties of the nuclei
of ecliptic and nearly-isotropic comets. We found that the shape model
resulting from the radar observations is incompatible with both the HST
and SST observations. A partial agreement could be obtained by assuming
very different albedos of the two components, in a ratio of at least 5.
---------------------------------------------------------
Title: Trojans' Odyssey: Unveiling the early history of the Solar
System
Authors: Lamy, Philippe; Vernazza, Pierre; Poncy, Joel; Martinot,
Vincent; Hinglais, Emmanuel; Canalias, Elisabet; Bell, Jim;
Cruikshank, Dale; Groussin, Olivier; Helbert, Joern; Marzari,
Francesco; Morbidelli, Alessandro; Rosenblatt, Pascal; Sierks, Holger
2012ExA....33..685L Altcode: 2011ExA...tmp...71L; 2011ExA...tmp..114L; 2011ExA...tmp...92L
In our present understanding of the Solar System, small bodies
(asteroids, Jupiter Trojans, comets and TNOs) are the most
direct remnants of the original building blocks that formed the
planets. Jupiter Trojan and Hilda asteroids are small primitive bodies
located beyond the `snow line', around respectively the L<SUB>4</SUB>
and L<SUB>5</SUB> Lagrange points of Jupiter at ∼5.2 AU (Trojans) and
in the 2:3 mean-motion resonance with Jupiter near 3.9 AU (Hildas). They
are at the crux of several outstanding and still conflicting issues
regarding the formation and evolution of the Solar System. They hold
the potential to unlock the answers to fundamental questions about
planetary migration, the late heavy bombardment, the formation of the
Jovian system, the origin and evolution of trans-neptunian objects,
and the delivery of water and organics to the inner planets. The
proposed Trojans' Odyssey mission is envisioned as a reconnaissance,
multiple flyby mission aimed at visiting several objects, typically five
Trojans and one Hilda. It will attempt exploring both large and small
objects and sampling those with any known differences in photometric
properties. The orbital strategy consists in a direct trajectory to one
of the Trojan swarms. By carefully choosing the aphelion of the orbit
(typically 5.3 AU), the trajectory will offer a long arc in the swarm
thus maximizing the number of flybys. Initial gravity assists from
Venus and Earth will help reducing the cruise time as well as the ΔV
needed for injection thus offering enough capacity to navigate among
Trojans. This solution further opens the unique possibility to flyby a
Hilda asteroid when leaving the Trojan swarm. During the cruise phase,
a Main Belt Asteroid could be targeted if requiring a modest ΔV. The
specific science objectives of the mission will be best achieved with a
payload that will perform high-resolution panchromatic and multispectral
imaging, thermal-infrared imaging/ radiometry, near- and mid-infrared
spectroscopy, and radio science/mass determination. The total mass
of the payload amounts to 50 kg (including margins). The spacecraft
is in the class of Mars-Express or a down-scaled version of Jupiter
Ganymede Orbiter. It will have a dry mass of 1200 kg, a total mass at
launch of 3070 kg and a ΔV capability of 700 m/s (after having reached
the first Trojan) and can be launched by a Soyuz rocket. The mission
operations concept (ground segment) and science operations are typical
of a planetary mission as successfully implemented by ESA during, for
instance, the recent flybys of Main Belt asteroids Steins and Lutetia.
---------------------------------------------------------
Title: The interaction between coronal mass ejections and streamers
as viewed by LASCO over 15 years
Authors: Floyd, O.; Lamy, P.; Llebaria, A.
2012EGUGA..14.9899F Altcode:
The question of the relationship of coronal mass ejections (CMEs)
to streamers dates back to the early observations of CMEs with space
coronagraphs and subsequent efforts to understand their origin. Whereas
the mass and kinetic energy losses of CMEs are insignificant in
the corona, they are considered a key player as a means to remove
magnetic flux and helicity that would otherwise build up in the
corona. How this may work essentially boils down to the nature of the
CME-streamer interaction i.e., as to whether CMEs respond passively
or contribute dynamically to the coronal field restructuring. We are
reconsidering this question on the basis of high resolution synoptic
maps at 3 Rsun constructed from the LASCO-C2 images of the corona
over 15 years (1996-2010) thus encompassing cycle 23 and the rising
phase of cycle 24. During that period, our ARTEMIS II catalog of
LASCO CMEs reports 21394 events and studying their interaction with
the streamer belt requires an automated procedure. For this purpose,
we consider that streamers are prominently one dimensional objects,
manifesting the boundary between regions of opposite magnetic
polarities that can be represented by the line of maximum radiance
along them. As such, streamers are defined as ridges on the synoptic
maps and an efficient way to detect these ridges consist in applying
a watershed filter. Then for each CME (which appears as a vertical
streak on the synoptic maps), we detect the streamer ridges present
before and after its occurence all along its latitudinal extent. The
CME-streamer interaction is then quantified in terms of geometric
changes (appearance/disappearance or displacement of the streamer)
and photometric changes (brightening/dimming of the streamer). We
will present statistical data on these interactions for the 1996-2010
time period.
---------------------------------------------------------
Title: A Global Two-temperature Corona and Inner Heliosphere Model:
A Comprehensive Validation Study
Authors: Jin, M.; Manchester, W. B.; van der Holst, B.; Gruesbeck,
J. R.; Frazin, R. A.; Landi, E.; Vasquez, A. M.; Lamy, P. L.; Llebaria,
A.; Fedorov, A.; Toth, G.; Gombosi, T. I.
2012ApJ...745....6J Altcode:
The recent solar minimum with very low activity provides us a unique
opportunity for validating solar wind models. During CR2077 (2008
November 20 through December 17), the number of sunspots was near
the absolute minimum of solar cycle 23. For this solar rotation,
we perform a multi-spacecraft validation study for the recently
developed three-dimensional, two-temperature, Alfvén-wave-driven
global solar wind model (a component within the Space Weather Modeling
Framework). By using in situ observations from the Solar Terrestrial
Relations Observatory (STEREO) A and B, Advanced Composition Explorer
(ACE), and Venus Express, we compare the observed proton state (density,
temperature, and velocity) and magnetic field of the heliosphere with
that predicted by the model. Near the Sun, we validate the numerical
model with the electron density obtained from the solar rotational
tomography of Solar and Heliospheric Observatory/Large Angle and
Spectrometric Coronagraph C2 data in the range of 2.4 to 6 solar
radii. Electron temperature and density are determined from differential
emission measure tomography (DEMT) of STEREO A and B Extreme Ultraviolet
Imager data in the range of 1.035 to 1.225 solar radii. The electron
density and temperature derived from the Hinode/Extreme Ultraviolet
Imaging Spectrometer data are also used to compare with the DEMT as
well as the model output. Moreover, for the first time, we compare
ionic charge states of carbon, oxygen, silicon, and iron observed in
situ with the ACE/Solar Wind Ion Composition Spectrometer with those
predicted by our model. The validation results suggest that most of the
model outputs for CR2077 can fit the observations very well. Based on
this encouraging result, we therefore expect great improvement for the
future modeling of coronal mass ejections (CMEs) and CME-driven shocks.
---------------------------------------------------------
Title: The Evolution of Plasma Parameters on a Coronal Source Surface
at 2.3 R <SUB>⊙</SUB> during Solar Minimum
Authors: Strachan, L.; Panasyuk, A. V.; Kohl, J. L.; Lamy, P.
2012ApJ...745...51S Altcode: 2011arXiv1111.1206S
We analyze data from the Solar and Heliospheric Observatory to
produce global maps of coronal outflow velocities and densities
in the regions where the solar wind is undergoing acceleration. The
maps use UV and white light coronal data obtained from the Ultraviolet
Coronagraph Spectrometer and the Large Angle Spectroscopic Coronagraph,
respectively, and a Doppler dimming analysis to determine the mean
outflow velocities. The outflow velocities are defined on a sphere at
2.3 R <SUB>⊙</SUB> from Sun-center and are organized by Carrington
Rotations during the solar minimum period at the start of solar cycle
23. We use the outflow velocity and density maps to show that while the
solar minimum corona is relatively stable during its early stages, the
shrinkage of the north polar hole in the later stages leads to changes
in both the global areal expansion of the coronal hole and the derived
internal flux tube expansion factors of the solar wind. The polar hole
areal expansion factor and the flux tube expansion factors (between
the coronal base and 2.3 R <SUB>⊙</SUB>) start out as super-radial
but then they become more nearly radial as the corona progresses away
from solar minimum. The results also support the idea that the largest
flux tube expansion factors are located near the coronal hole/streamer
interface, at least during the deepest part of the solar minimum period.
---------------------------------------------------------
Title: Asteroid (21) Lutetia as a remnant of Earth’s precursor
planetesimals
Authors: Vernazza, P.; Lamy, P.; Groussin, O.; Hiroi, T.; Jorda, L.;
King, P. L.; Izawa, M. R. M.; Marchis, F.; Birlan, M.; Brunetto, R.
2011Icar..216..650V Altcode:
Isotopic and chemical compositions of meteorites, coupled with dynamical
simulations, suggest that the main belt of asteroids between Mars and
Jupiter contains objects formed in situ as well as a population of
interlopers. These interlopers are predicted to include the building
blocks of the terrestrial planets as well as objects that formed
beyond Neptune (Bottke et al. 2006, Levison et al. 2009, Walsh et
al. 2011). Here we report that the main belt asteroid (21) Lutetia -
encountered by the Rosetta spacecraft in July 2010 - has spectral (from
0.3 to 25 μm) and physical (albedo, density) properties quantitatively
similar to the class of meteorites known as enstatite chondrites. The
chemical and isotopic compositions of these chondrites indicate that
they were an important component of the formation of Earth and other
terrestrial planets. This meteoritic association implies that Lutetia
is a member of a small population of planetesimals that formed in
the terrestrial planet region and that has been scattered in the
main belt by emerging protoplanets (Bottke et al. 2006) and/or by the
migration of Jupiter (Walsh et al. 2011) early in its history. Lutetia,
along with a few other main-belt asteroids, may contains part of the
long-sought precursor material (or closely related materials) from
which the terrestrial planets accreted.
---------------------------------------------------------
Title: The cosmic dust analyser onboard cassini: ten years of
discoveries
Authors: Srama, R.; Kempf, S.; Moragas-Klostermeyer, G.; Altobelli,
N.; Auer, S.; Beckmann, U.; Bugiel, S.; Burton, M.; Economomou, T.;
Fechtig, H.; Fiege, K.; Green, S. F.; Grande, M.; Havnes, O.; Hillier,
J. K.; Helfert, S.; Horanyi, M.; Hsu, S.; Igenbergs, E.; Jessberger,
E. K.; Johnson, T. V.; Khalisi, E.; Krüger, H.; Matt, G.; Mocker, A.;
Lamy, P.; Linkert, G.; Lura, F.; Möhlmann, D.; Morfill, G. E.; Otto,
K.; Postberg, F.; Roy, M.; Schmidt, J.; Schwehm, G. H.; Spahn, F.;
Sterken, V.; Svestka, J.; Tschernjawski, V.; Grün, E.; Röser, H. -P.
2011CEAS....2....3S Altcode: 2018arXiv180204772S
The interplanetary space probe Cassini/Huygens reached Saturn in July
2004 after 7 years of cruise phase. The German cosmic dust analyser
(CDA) was developed under the leadership of the Max Planck Institute
for Nuclear Physics in Heidelberg under the support of the DLR
e.V. This instrument measures the interplanetary, interstellar and
planetary dust in our solar system since 1999 and provided unique
discoveries. In 1999, CDA detected interstellar dust in the inner
solar system followed by the detection of electrical charges of
interplanetary dust grains during the cruise phase between Earth and
Jupiter. The instrument determined the composition of interplanetary
dust and the nanometre-sized dust streams originating from Jupiter's
moon Io. During the approach to Saturn in 2004, similar streams of
submicron grains with speeds in the order of 100 km/s were detected
from Saturn's inner and outer ring system and are released to the
interplanetary magnetic field. Since 2004 CDA measured more than one
million dust impacts characterising the dust environment of Saturn. The
instrument is one of the three experiments which discovered the active
ice geysers located at the south pole of Saturn's moon Enceladus in
2005. Later, a detailed compositional analysis of the water ice grains
in Saturn's E ring system led to the discovery of large reservoirs of
liquid water (oceans) below the icy crust of Enceladus. Finally, the
determination of the dust-magnetosphere interaction and the discovery
of the extended E ring (at least twice as large as predicted) allowed
the definition of a dynamical dust model of Saturn's E ring describing
the observed properties. This paper summarizes the discoveries of a
10-year story of success based on reliable measurements with the most
advanced dust detector flown in space until today. This paper focuses
on cruise results and findings achieved at Saturn with a focus on flux
and density measurements. CDA discoveries related to the detailed dust
stream dynamics, E ring dynamics, its vertical profile and E ring
compositional analysis are published elsewhere (see Hus et al. in
AIP Conference Proccedings 1216:510-513, 2010; Hsu et al. in Icarus
206:653-661, 2010; Kempf et al. in Icarus 193:420, 2008; 206(2):446,
2010; Postberg et al. in Icarus 193(2):438, 2008; Nature 459:1098,
2009; Nature, 2011, doi: 10.1038/nature10175).
---------------------------------------------------------
Title: Comparison of Velocity, Density, Temperature, and Mass Flux
Results with Solar Coronal Models
Authors: Strachan, L.; Cranmer, S. R.; Panasyuk, A.; Kohl, J. L.;
Lamy, P. L.
2011AGUFMSH53C..07S Altcode:
We have recently computed a series of global maps of plasma parameters
in the extended corona using data from the Solar and Heliospheric
Observatory (SOHO). The synoptic maps of velocity, density, temperature,
and mass flux were derived from UV and white light coronal data
obtained from the Ultraviolet Coronagraph Spectrometer (UVCS) and
the Large Angle Spectroscopic Coronagraph (LASCO). The parameters
are defined on a sphere at 2.3~ R<SUB>⊙</SUB> from Sun-center and
are organized by Carrington Rotations during the 1996 -- 1998 solar
minimum for Solar Cycle 23. The data imply that there are large flux
tube expansion factors near the coronal hole/streamer boundaries,
but these factors change significantly as the corona evolves from
minimum to the rising phase. We compare these data to an independently
developed theoretical model that includes damping and acceleration
by Alfven waves in the corona (see Cranmer et al. 2007, ApJS, 171,
520). The data set will be extended in the future and it will be used
for constraining other theoretical models of the corona and solar wind.
---------------------------------------------------------
Title: The helium shells of HeI and HeII at solar minimum: New
results from eclipse flash spectra of 2008- 2010
Authors: Bazin, C.; Koutchmy, S.; Lamy, P.
2011sf2a.conf..203B Altcode:
Flash spectra taken at high frame rate during the total solar
eclipse of August 1st 2008 in Siberia and during the July 11th 2010
in French Polynesia are compared in the context of the quiet Sun near
the minimum of activity. They both reveal the weak Paschen α 468.6
nm ionized helium line, seen as a helium shell in layers up to the
8 Mm heights. The preliminary evaluated effective height of the He
I 4713 shell is 1.8 Mm and it is approximately 2.0 Mm for the He II
4686 emissions outside polar regions. These lines can be measured
only in eclipse conditions, when the parasitic scattered light is
negligible for very low solar fluxes corresponding to the coronal
levels. Many faint lines are also seen in emission such as Ba +, Ti +,
Fe +, but with a much lower radial extension. They were observed to be
superposed to F-lines when defining the solar limb using the continuum
background. A cartoon is proposed to describe the structuration of
these low layers and to illustrate the contribution of the magnetic
field. These observations are important new insights for understanding
(i) the magnetic field inference in the very low layers of the solar
transition region and (ii) the ionisation mechanisms producing the
big jump of the temperature towards the corona, including the source
of heating.
---------------------------------------------------------
Title: Observations of the White Light Corona from Solar Orbiter
and Solar Probe Plus
Authors: Howard, R. A.; Thernisien, A. F.; Vourlidas, A.; Plunkett,
S. P.; Korendyke, C. M.; Sheeley, N. R.; Morrill, J. S.; Socker,
D. G.; Linton, M. G.; Liewer, P. C.; De Jong, E. M.; Velli, M. M.;
Mikic, Z.; Bothmer, V.; Lamy, P. L.
2011AGUFMSH43F..06H Altcode:
The SoloHI instrument on Solar Orbiter and the WISPR instrument on Solar
Probe+ will make white light coronagraphic images of the corona as the
two spacecraft orbit the Sun. The minimum perihelia for Solar Orbiter
is about 60 Rsun and for SP+ is 9.5 Rsun. The wide field of view of the
WISPR instrument (about 105 degrees radially) corresponds to viewing
the corona from 2.2 Rsun to 20 Rsun. Thus the entire Thomson hemisphere
is contained within the telescope's field and we need to think of
the instrument as being a traditional remote sensing instrument and
then transitioning to a local in-situ instrument. The local behavior
derives from the fact that the maximum Thomson scattering will favor
the electron plasma close to the spacecraft - exactly what the in-situ
instruments will be sampling. SoloHI and WISPR will also observe
scattered light from dust in the inner heliosphere, which will be an
entirely new spatial regime for dust observations from a coronagraph,
which we assume to arise from dust in the general neighborhood of about
half way between the observer and the Sun. As the dust grains approach
the Sun, they evaporate and do not contribute to the scattering. A
dust free zone has been postulated to exist somewhere inside of 5 Rsun
where all dust is evaporated, but this has never been observed. The
radial position where the evaporation occurs will depend on the
precise molecular composition of the individual grains. The orbital
plane of Solar Orbiter will gradually increase up to about 35 degrees,
enabling a very different view through the zodiacal dust cloud to test
the models generated from in-ecliptic observations. In this paper we
will explore some of the issues associated with the observation of
the dust and will present a simple model to explore the sensitivity
of the instrument to observe such evaporations.
---------------------------------------------------------
Title: The Trojans' Odyssey space mission
Authors: Lamy, P.; Vernazza, P.; Groussin, O.; Poncy, J.; Martinot,
V.; Hinglais, E.; Bell, J.; Cruikshank, D.; Helbert, J.; Marzari,
F.; Morbidelli, A.; Rosenblatt, P.
2011epsc.conf..703L Altcode: 2011DPS....43..703L
In our present understanding of the Solar System, small bodies
(asteroids, Jupiter Trojans, comets and TNOs) are the most
direct remnants of the original building blocks that formed the
planets. Jupiter Trojan and Hilda asteroids are small primitive
bodies located beyond the "snow line", around respectively the L4
and L5 Lagrange points of Jupiter at 5.2 AU (Trojans) and in the
2:3 mean-motion resonance with Jupiter near 3.9 AU (Hildas). They
are at the crux of several outstanding and still conflicting issues
regarding the formation and evolution of the Solar System. They hold
the potential to unlock the answers to fundamental questions about
planetary migration, the late heavy bombardment, the formation of the
Jovian system, the origin and evolution of trans-neptunian objects,
and the delivery of water and organics to the inner planets. The
proposed Trojans' Odyssey mission is envisioned as a reconnaissance,
multiple flyby mission aimed at visiting several objects, typically five
Trojans and one Hilda. It will attempt exploring both large and small
objects and sampling those with any known differences in photometric
properties. The orbital strategy consists in a direct trajectory to one
of the Trojan swarms. By carefully choosing the aphelion of the orbit
(typically 5.3 AU), the trajectory will offer a long arc in the swarm
thus maximizing the number of flybys. Initial gravity assists from Venus
and Earth will help reducing the cruise to 7 years as well as the ?V
needed for injection thus offering enough capacity to navigate among
Trojans. This solution further opens the unique possibility to flyby a
Hilda asteroid when leaving the Trojan swarm. During the cruise phase,
a Main Belt Asteroid could be targeted if requiring a modest ?V. The
specific science objectives of the mission will be best achieved with a
payload that will perform high-resolution panchromatic and multispectral
imaging, thermal-infrared imaging/ radiometry, near- and mid-infrared
spectroscopy, and radio science/mass determination. The total mass
of the payload amounts to 50 kg (including margins). The spacecraft
is in the class of Mars-Express or a down-scaled version of Jupiter
Ganymede Orbiter. It will have a dry mass of 1200 kg, a total mass at
launch of 3070 kg and a V capability of 700 m/sec (after having reached
the first Trojan) and can be launched by a Soyuz rocket. The mission
operations concept (ground segment) and science operations are typical
of a planetary mission as successfully implemented by ESA during, for
instance, the recent flybys of Main Belt asteroids Steins and Lutetia.
---------------------------------------------------------
Title: THERMAP: a mid-infrared spectro-imager based on an uncooled
micro-bolometer for the Marco Polo R mission.
Authors: Brageot, E.; Groussin, O.; Lamy, P.; Reynaud, J. L.;
Fargant, G.
2011epsc.conf..129B Altcode: 2011DPS....43..129B
We report on an on-going feasibility study of a midinfrared (8-18 μm)
spectro-imager for the Marco Polo R mission (THERMAP). Based on the
recent development of uncooled micro-bolometer technology, we can now
use these detectors for planetary missions. We present our results
on using this detector to perform calibrated radiometric images,
and a preliminary assessment of its performances for spectroscopic
measurements of a Near Earth Asteroid (NEA).
---------------------------------------------------------
Title: Shape and Physical Properties of Asteroid (21) Lutetia from
OSIRIS Images
Authors: Jorda, L.; Gaskell, R.; Lamy, P.; Kaasalainen, M.; Groussin,
O.; Faury, G.; Gutierrez, P.; Sabolo, W.; Hviid, S.
2011epsc.conf..776J Altcode: 2011DPS....43..776J
The Rosetta spacecraft of the European Space Agency flew by asteroid
(21) Lutetia on July, 10, 2010 on its way to its final target, comet
67P/Churyumov- Gerasimenko. A total of 460 images has been acquired
during the flyby with the narrow (NAC) and wide (WAC) angle cameras
of the OSIRIS instrument, the NAC pixel scale reaching a minimum
value of 60 m at closest approach. Several filters have been used,
covering a wavelength range from the far UV (0.25 μm) to the end of
the visible spectrum (1.0 μm). The phase angle went through the range
11°-0°-160°, the spacecraft reaching opposition 18 min before closest
approach. We will report on the calculation of the threedimensional
high-resolution global shape model of (21) Lutetia using two techniques:
stereophotoclinometry for the regions observed by OSIRIS, complemented
by inversion of photometric light curves and adaptive optics profiles
for the rest of the surface. This allows us to retrieve the physical
properties of this object: volume, moments of inertia, gravity field,
local gravitational slopes and rotational parameters. The density is
calculated using the mass measured by the radio science experiment (RSI)
on board Rosetta. We will further discuss quantitatively the properties
of the main geo-morphological features observed at the surface.
---------------------------------------------------------
Title: Images of Asteroid 21 Lutetia: A Remnant Planetesimal from
the Early Solar System
Authors: Sierks, H.; Lamy, P.; Barbieri, C.; Koschny, D.; Rickman, H.;
Rodrigo, R.; A'Hearn, M. F.; Angrilli, F.; Barucci, M. A.; Bertaux,
J. -L.; Bertini, I.; Besse, S.; Carry, B.; Cremonese, G.; Da Deppo,
V.; Davidsson, B.; Debei, S.; De Cecco, M.; De Leon, J.; Ferri, F.;
Fornasier, S.; Fulle, M.; Hviid, S. F.; Gaskell, R. W.; Groussin, O.;
Gutierrez, P.; Ip, W.; Jorda, L.; Kaasalainen, M.; Keller, H. U.;
Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.;
Lazzarin, M.; Leyrat, C.; Moreno, J. J. Lopez; Magrin, S.; Marchi,
S.; Marzari, F.; Massironi, M.; Michalik, H.; Moissl, R.; Naletto,
G.; Preusker, F.; Sabau, L.; Sabolo, W.; Scholten, F.; Snodgrass,
C.; Thomas, N.; Tubiana, C.; Vernazza, P.; Vincent, J. -B.; Wenzel,
K. -P.; Andert, T.; Pätzold, M.; Weiss, B. P.
2011Sci...334..487S Altcode:
Images obtained by the Optical, Spectroscopic, and Infrared Remote
Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft
reveal that asteroid 21 Lutetia has a complex geology and one of
the highest asteroid densities measured so far, 3.4 ± 0.3 grams per
cubic centimeter. The north pole region is covered by a thick layer of
regolith, which is seen to flow in major landslides associated with
albedo variation. Its geologically complex surface, ancient surface
age, and high density suggest that Lutetia is most likely a primordial
planetesimal. This contrasts with smaller asteroids visited by previous
spacecraft, which are probably shattered bodies, fragments of larger
parents, or reaccumulated rubble piles.
---------------------------------------------------------
Title: Shape reconstruction of irregular bodies with multiple
complementary data sources
Authors: Kaasalainen, M.; Viikinkoski, M.; Carry, B.; Durech, J.;
Lamy, P.; Jorda, L.; Marchis, F.; Hestroffer, D.
2011epsc.conf..416K Altcode: 2011DPS....43..416K
Irregularly shaped bodies with at most partial in situ data are a
particular challenge for shape reconstruction and mapping. We have
created an inversion algorithm and software package for complementary
data sources, with which it is possible to create shape and spin
models with feature details even when only groundbased data are
available. The procedure uses photometry, adaptive optics or other
images, occultation timings, and interferometry as main data sources,
and we are extending it to include range-Doppler radar and thermal
infrared data as well. The data sources are described as generalized
projections in various observable spaces [2], which allows their uniform
handling with essentially the same techniques, making the addition of
new data sources inexpensive in terms of computation time or software
development. We present a generally applicable shape support that can be
automatically used for all surface types, including strongly nonconvex
or non-starlike shapes. New models of Kleopatra (from photometry,
adaptive optics, and interferometry) and Hermione are examples of this
approach. When using adaptive optics images, the main information from
these is extracted from the limb and terminator contours that can be
determined much more accurately than the image pixel brightnesses that
inevitably contain large errors for most targets. We have shown that the
contours yield a wealth of information independent of the scattering
properties of the surface [3]. Their use also facilitates a very fast
and robustly converging algorithm. An important concept in the inversion
is the optimal weighting of the various data modes. We have developed
a mathematicallly rigorous scheme for this purpose. The resulting
maximum compatibility estimate [3], a multimodal generalization of
the maximum likelihood estimate, ensures that the actual information
content of each source is properly taken into account, and that the
resolution scale of the ensuing model can be reliably estimated. We
have applied our procedure to several asteroids, and the ground truth
from the Rosetta/Lutetia flyby confirmed the ability of the approach
to recover shape details [1] (see also Carry et al., this meeting). We
have created a general flyby-version of the procedure to construct
full models of planetary targets for which probe images are only
available of a part of the surface (a typical setup for many planetary
missions). We have successfully combined flyby images with photometry
(Steins [4]) and adaptive optics images (Lutetia); the portion of
the surface accurately determined by the flyby constrains the shape
solution of the "dark side" efficiently.
---------------------------------------------------------
Title: Asteroids (21) Lutetia and (2867) Steins: same origin but
different evolution ?
Authors: Lamy, P.; Vernazza, P.; Groussin, O.; Jorda, L.
2011epsc.conf..699L Altcode: 2011DPS....43..699L
Asteroids (21) Lutetia and (2867) Steins which have recently been
visited by the Rosetta spacecraft of the European Space Agency are both
members of very small populationss of bodies among the vast majority
of asteroids. After having been the archetype of the M taxonomy class,
Lutetia is now an Xc type (DeMeo et al. 2009). Steins is classified as
an igneous E-type asteroids, more precisely in the new Xe subclass (De-
Meo et al. 2009) which contains only 7 known members. The composition
and henceforth origin of asteroids rely on their association to
meteorites if proper analogs based on visible, NIR and MIR reflectances
can be identified. Following the most recent spectroscopic works,
the association of Lutetia to enstatite chondrites appears robust
(Vernazza et al. 2011). The case of Steins is less clear but aubrite
meteorites are favored although several features in its spectrum still
poses problems and we actually may not have in our present meteorite
collections the proper analog (Clark et al. 2004). The trend of these
associations with meteorites which represent a reduced, volatile-poor,
anhydrous end-member of early solar system materials (Rubin 1997,
Scott 2007) thought to have formed in the inner region of the solar
nebula, near the proto-Sun implies that neither Lutetia nor Steins
formed at their present location in the asteroid belt and are probably
part of the population of interlopers. The dynamical mechnanism that
transported them from the inner solar system to the main belt is likely
to be similar to the one explaining the origin of iron meteorites as
remnants of differentiated planetesimals formed in the terrestrial
planet region (Bottke et al. 2006). Extended dynamical simulations
reveal that, at the time where terrestrial accretion was ongoing, a
small fraction (<2%) of the planetesimals residing in the 0.5-1.5
AU region were scattered out by emerging protoplanets and achieved
main-belt orbits, thus becoming dynamically indistinguishable from
the rest of the main-belt population. However based on the physical
properties derived from the recent flybys, Lutetia and Steins have
followed very different evolutions. With a density of 3.4 g/cm3,
Lutetia appears as a primordial planetesimal having suffered at most
minimal shattering from the largest impacts. On the contrary, the
shape of Steins suggests complete restructuring in a rubble-pile as
a consequence of the catastrophic disruption of its parent body.
---------------------------------------------------------
Title: Asteroids (21) Lutetia: global and spatially resolved
photometric properties
Authors: Faury, G.; Lamy, P.; Vernazza, P.; Jorda, L.; Toth, I.
2011epsc.conf..759F Altcode: 2011DPS....43..759F
Asteroids (21) Lutetia has recently been visited by the Rosetta
spacecraft of the European Space Agency and imaged by its Rosetta
narrow (NAC) and wide (WAC) angle cameras. The accurate photometric
analysis of the images requires utmost care due to several instrumental
problems, the most severe and complex to handle being the presence of
optical ghosts which result from multiple reflections on the two filters
inserted in the optical beam and on the thick window which protects the
CCD detector from cosmic ray impacts. These ghosts prominently appears
as either slighlty defocused images offset from the primary images or
large round or elliptical halos. The appearance, the location and the
radiance of each individual ghost depends upon the optical configuration
(selected filters) and on the image itself so that no general model
can be proposed. Consequently, a case-by-case approach must be adopted
which requires a long and tedious work where each ghost is individually
parametrized according to its specific geometry (defocused offset image
or halo) and iteratively fitted to the original image. The procedure
has been successfully applied to all NAC and WAC images and works
extremely well with residuals and sometime artifacts at insignificant
levels. Both NAC and WAC have further been recalibrated using the most
recent observations of stellar calibrators VEGA and the solar analog
16 Cyg B allowing to correct the quantum efficiency response of the
two CCD and the throughput for all channels (i.e., filters). We will
present results on the global photometric properties of (21) Lutetia,
albedo, phase function and spectral reflectivity as well as spatially
resolved properties based on a novel method developed in the space of
the facets representing the three-dimensional shape of the body. This
method successfully implemented in the cases of the nucleus of comet
9P/Tempel 2 and of asteroid (2867) Steins (Spjuth et al. 2011) has the
advantage of automatically tracking the same local surface element on
a series of images. The analysis proceeds with the determination of the
global Hapke and other standard photometric parameters as well as their
two-dimensional variations across the surface. This allows defining,
in the body-fixed reference frame, "high residual regions" (HRRs) which
correspond to significant relative differences between the observed
and modeled photometric parameters such as the singlescattering albedo
(SSA), the mean roughness slope angle, and the reflectivity gradient.
---------------------------------------------------------
Title: Plateau de Bure observations of the methanol in 103P/Hartley
Authors: Boissier, J.; Bockelée-Morvan, D.; Biver, N.; Crovisier, J.;
Colom, P.; Lellouch, E.; Moreno, R.; Groussin, O.; Jorda, L.; Lamy, P.
2011epsc.conf..985B Altcode: 2011DPS....43..985B
The comet 103P/Hartley 2 made a close approach to the Earth in October
2010, down to a distance of 0.12 AU. In early November, the Deep
Impact spacecraft performed a flyby of the comet, in the framework
of its extended mission Epoxi [1]. It has been the target of various
observing campaigns at all wavelengths involving ground- and space-based
observatories [2]. We present here the results of observations performed
with the IRAM Plateau de Bure. We observed the emission of several
methanol lines from which we built the methanol rotation diagram and
measured the rotational temperature in the coma. The interferometric
maps have a spatial resolution of few arcseconds, corresponding to
few hundred kilometers. Combined to single dish observations these
data allow the measurement of the temperature profile in the coma. In
addition, other coma properties can be investigateded from our data
set such as the origin of methanol in the coma, the coma structure
and its time variability.
---------------------------------------------------------
Title: Asteroid 21 Lutetia: Low Mass, High Density
Authors: Pätzold, M.; Andert, T. P.; Asmar, S. W.; Anderson, J. D.;
Barriot, J. -P.; Bird, M. K.; Häusler, B.; Hahn, M.; Tellmann, S.;
Sierks, H.; Lamy, P.; Weiss, B. P.
2011Sci...334..491P Altcode:
Asteroid 21 Lutetia was approached by the Rosetta spacecraft on 10 July
2010. The additional Doppler shift of the spacecraft radio signals
imposed by 21 Lutetia’s gravitational perturbation on the flyby
trajectory were used to determine the mass of the asteroid. Calibrating
and correcting for all Doppler contributions not associated with
Lutetia, a least-squares fit to the residual frequency observations
from 4 hours before to 6 hours after closest approach yields a mass
of (1.700 ± 0.017) × 10<SUP>18</SUP> kilograms. Using the volume
model of Lutetia determined by the Rosetta Optical, Spectroscopic,
and Infrared Remote Imaging System (OSIRIS) camera, the bulk density,
an important parameter for clues to its composition and interior, is
(3.4 ± 0.3) × 10<SUP>3</SUP> kilograms per cubic meter.
---------------------------------------------------------
Title: A new 3D reconstruction method of small solar system bodies
Authors: Capanna, C.; Jorda, L.; Lamy, P.; Gesquiere, G.
2011epsc.conf..945C Altcode: 2011DPS....43..945C
The 3D reconstruction of small solar system bodies consitutes an
essential step toward understanding and interpreting their physical
and geological properties. We propose a new reconstruction method by
photoclinometry based on the minimization of the chisquare difference
between observed and synthetic images by deformation of a 3D triangular
mesh. This method has been tested on images of the two asteroids
(2867) Steins and (21) Lutetia observed during ESA's ROSETTA mission,
and it will be applied to elaborate digital terrain models from images
of the asteroid (4) Vesta, the target of NASA's DAWN spacecraft.
---------------------------------------------------------
Title: A Global Two-Temperature Corona and Inner Heliosphere Model:
A Validation Study
Authors: Jin, Meng; Manchester, W. B.; van der Holst, B.; Gruesbeck,
J.; Frazin, R. A.; Vasquez, A. M.; Lamy, P. L.; Llebaria, A.; Fedorov,
A.; Toth, G.; Gombosi, T. I.
2011shin.confE..12J Altcode:
The recent solar minimum with very low activity provides us a unique
opportunity for validating solar wind models. During CR2077 (2008,
November 20 through December 17), the sunspots number reaches the
absolute minimum of solar cycle 23. For this solar rotation, we
perform a multi-spacecraft validation study for the recently developed
three-dimensional, two-temperature, Alfven-wave-driven global solar wind
model (a component within the Space Weather Modeling Framework). By
using in situ observations from STEREO A and B, ACE/WIND and Venus
Express, we compare the observed proton state (density, temperature and
velocity) and magnetic field of the heliosphere with that predicted
by the model. Near the Sun, we validate the numerical model with the
electron density obtained from the solar rotational tomography of
SOHO/LASCO-C2 data in the range of 2.4 to 6 solar radii. Electron
temperature and density are determined from differential emission
measure tomography of STEREO A and B EUVI data in the range of 1.035 to
1.225 solar radii. Moreover, we compare ionic charge states of carbon,
oxygen, silicon, and iron observed in situ with ACE/SWICS and that
predicted by our model. The validation results suggest that most of
the model outputs for CR2077 can fit the observations very well. Based
on this encouraging result, we therefore expect great improvement for
the modeling of CMEs and CME-driven shocks in the future.
---------------------------------------------------------
Title: The properties of asteroid (2867) Steins from Spitzer Space
Telescope observations and OSIRIS shape reconstruction
Authors: Groussin, O.; Lamy, P.; Fornasier, S.; Jorda, L.
2011A&A...529A..73G Altcode: 2011arXiv1104.5328G
<BR /> Aims: We report on the thermal properties and composition of
asteroid (2867) Steins derived from an analysis of new Spitzer Space
Telescope (SST) observations performed in March 2008, in addition to
previously published SST observations performed in November 2005. <BR />
Methods: We consider the three-dimensional shape model and photometric
properties derived from OSIRIS images obtained during the flyby of the
Rosetta spacecraft in September 2008, which we combine with a thermal
model to properly interpret the observed SST thermal light curve and
spectral energy distributions. <BR /> Results: We obtain a thermal
inertia of 100 ± 50 J K<SUP>-1</SUP> m<SUP>-2</SUP> s<SUP>-1/2</SUP>
and a beaming factor (roughness) in the range 0.7-1.0. We confirm
that the infrared emissivity of Steins is consistent with an enstatite
composition. The November 2005 SST thermal light curve is most reliably
interpreted by assuming inhomogeneities in the thermal properties
of the surface, with two different regions of slightly different
roughness, as observed on other small bodies, such as the nucleus
of comet 9P/Tempel 1. Our results emphasize that the shape model is
important to an accurate determination of the thermal inertia and
roughness. Finally, we present temperature maps of Steins, as seen
by Rosetta during its flyby, and discuss the interpretation of the
observations performed by the VIRTIS and MIRO instruments.
---------------------------------------------------------
Title: Earth-based detection of the millimetric thermal emission
from the nucleus of comet 8P/Tuttle
Authors: Boissier, J.; Groussin, O.; Jorda, L.; Lamy, P.;
Bockelée-Morvan, D.; Crovisier, J.; Biver, N.; Colom, P.; Lellouch,
E.; Moreno, R.
2011A&A...528A..54B Altcode: 2011arXiv1101.3415B
Context. Little is known about the physical properties of cometary
nuclei. Measuring the thermal emission of a nucleus is one of
the few means of deriving its size, independently of its albedo,
and constraining some of its thermal properties. This emission is
difficult to detect from Earth but space telescopes, such as th
Infrared Space Observatory, Spitzer Space Telescope, and Herschel
Space Observatory, allow reliable measurements to be made in the
infrared and the sub-millimetre domains. <BR /> Aims: We attempt to
characterize more accurately the thermal properties of the nucleus
of comet 8P/Tuttle using multiwavelength space- and ground-based
observations, in the visible, infrared, and millimetre range. <BR />
Methods: We used the Plateau de Bure Interferometer to measure the
millimetre thermal emission of comet 8P/Tuttle at 240 GHz (1.25 mm)
and analysed the observations with the shape model derived from Hubble
Space Telescope observations and the nucleus size derived from Spitzer
Space Telescope observations. <BR /> Results: We report on the first
detection of the millimetre thermal emission of a cometary nucleus since
comet C/1995 O1 Hale-Bopp in 1997. Using the two contact-sphere shape
model derived from Hubble Space Telescope observations, we constrain the
thermal properties of the nucleus. Our millimetre observations are most
accurately reproduced by assuming: i) a thermal inertia lower than ~10
J K<SUP>-1</SUP> m<SUP>-2</SUP> s<SUP>-1/2</SUP>, and ii) an emissivity
lower than 0.8, which is indicative of a non-negligible contribution
of the colder sub-surface layers to the outcoming millimetre flux. <P
/>Based on observations carried out with the IRAM Plateau de Bure
Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany)
and IGN (Spain).
---------------------------------------------------------
Title: Properties of the nuclei and comae of 10 ecliptic comets from
Hubble Space Telescope multi-orbit observations
Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; A'Hearn, M. F.;
Jorda, L.
2011MNRAS.412.1573L Altcode: 2011MNRAS.tmp..381L
We report on our on-going effort to detect and characterize cometary
nuclei with the Hubble Space Telescope (HST). During cycle 9 (2000 July
to 2001 June), we performed multi-orbit observations of 10 ecliptic
comets with the Wide Field Planetary Camera 2. Nominally, eight
contiguous orbits covering a time interval of ∼11 h were devoted
to each comet but a few orbits were occasionally lost. In addition
to the standard R band, we could additionally observe four of them
in the V band and the two brightest ones in the B band. Time series
photometry was used to constrain the size, shape and rotational period
of the 10 nuclei. Assuming a geometric albedo of 0.04 for the R band,
a linear phase law with a coefficient of 0.04 mag deg<SUP>-1</SUP>
and an opposition effect similar to that of comet 19P/Borrelly,
we determined the following mean values of the effective radii
47P/Ashbrook-Jackson: 2.86±0.08 km, 61P/Shajn-Schaldach: 0.62±0.02
km, 70P/Kojima: 1.83±0.05 km, 74P/Smirnova-Chernykh: 2.23±0.04 km,
76P/West-Kohoutek-Ikemura: 0.30±0.02 km, 82P/Gehrels 3: 0.69±0.02
km, 86P/Wild 3: 0.41±0.03 km, 87P/Bus: 0.270.01 km, 110P/Hartley 3:
2.15±0.04 km and 147P/Kushida-Muramatsu: 0.21±0.01 km. Because of
the limited time coverage (∼11 h), the rotational periods could not
be accurately determined, multiple solutions were sometime found and
three periods were not constrained at all. Our estimates range from
∼5 to ∼32 h. The lower limits for the ratio a/b of the semi-axis of
the equivalent spheroids range from 1.10 (70P) to 2.20 (87P). The four
nuclei for which we could measure (V-R) are all significantly redder
than the Sun, with 86P/Wild 3 (V-R) = 0.86 ± 0.10 appearing as an
ultrared object. We finally determined the dust activity parameter Afρ
of their coma in the R band, the colour indices and the reflectivity
spectra of four of them. Based on observations made with the NASA/ESA
Hubble Space Telescope, obtained at Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy under NASA contract NAS 5-26555.
---------------------------------------------------------
Title: Physical Properties of Craters on Asteroid (21) Lutetia
Authors: Vincent, J. -B.; Marchi, S.; Besse, S.; Böhnhardt, H.;
Sierks, H.; A'Hearn, M.; Angrilli, F.; Barbieri, C.; Barucci, A.;
Cremonese, G.; da Deppo, V.; Davidsson, B.; Debei, S.; de Cecco, M.;
Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P.; Hviid, S. F.;
Ip, W. -H.; Keller, H. U.; Kramm, J. R.; Knollenberg, J.; Koschny,
D.; Kuehrt, E.; Kueppers, M.; Lamy, P.; Lara, L. M.; Lazzarin, M.;
Lopez-Moreno, J. J.; Magrin, S.; Marzari, F.; Massironi, M.; Michalik,
H.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.;
Wenzel, K. -P.
2011LPI....42.2417V Altcode:
This abstract presents the physical properties of craters derived from
the measurement of depth/diameter ratios on asteroid (21) Lutetia. We
show how the d/D ratio varies in different regions and how it can be
used to better understand the processes that affected the surface.
---------------------------------------------------------
Title: Partition of Proton and Electron Heating in the Solar Wind
(Invited)
Authors: van der Holst, B.; Jin, M.; Manchester, W. B.; Frazin, R. A.;
Vasquez, A. M.; Lamy, P. L.; Llebaria, A.; Gombosi, T. I.
2010AGUFMSH41E..01V Altcode:
The electron and proton temperature profiles in the solar wind are
very nonadiabatic so that additional heat deposition is needed for both
species. A possible heating source is the Kolmogorov-like dissipation of
the Alfvén waves. It is still an open issue how turbulence partitions
the heat between the electrons and protons (see, e.g., Stawarz et
al., 2009 and Breech et al., 2009). Comparison of empirical electron
temperature, derived from differential emission measure tomography
(DEMT) applied to STEREO A and B EUVI images, with numerical solar wind
models allows us to constrain this heating partition. The DEMT results
cover the height range 1.035 to 1.225 Rsun. The densities are compared
to the solar rotational tomography on LASCO-C2 data of SOHO to further
constrain the wind acceleration and heating models. We specifically
analyze the periods of Carrington rotations 2077 and 2095. We use the
recently developed three-dimensional two-temperature solar wind model
within the Space Weather Modeling Framework (SWMF), which includes
the anisotropic electron thermal heat conduction, and the collisional
heat transfer between the electrons and protons. The solar wind is
assumed to be accelerated by the Alfvén waves, and we use Kolmogorov
dissipation of these waves to heat both the protons and electrons.
---------------------------------------------------------
Title: Testing Coronal and Solar Wind MHD Models with UV Spectroscopic
and Visible Light Coronagraph Data
Authors: Strachan, L.; Panasyuk, A.; Kohl, J. L.; Woolsey, L.; Lamy,
P. L.
2010AGUFMSH42A..08S Altcode:
We present synoptic maps of coronal outflow velocities obtained at 2.3
Rs in the solar wind acceleration region of the corona during Solar
Cycle 23. The outflow velocities are obtained by using data from the
SOHO coronagraphs: H I Lyman alpha and O VI line profiles (from UVCS)
and white light polarized brightness data (from LASCO). The information
contained in the maps provide constraints on the electron densities,
bulk outflow speeds, and anisotropic kinetic temperatures (velocity
distributions for protons and minor ions. We show some examples of how
these data can be used to test MHD models of the solar corona and solar
wind. The data set can be used to compare empirically derived plasma
parameters directly with the MHD model parameters or alternatively it
can be used to compare the observed profiles with synthetic profiles
obtained by forward modeling of the MHD data.
---------------------------------------------------------
Title: Multispacecraft Validation of a Global Two-Temperature Corona
and Inner Heliosphere Model (Invited)
Authors: van der Holst, B.; Jin, M.; Manchester, W. B.; Frazin, R. A.;
Vasquez, A. M.; Lamy, P. L.; Llebaria, A.; Gombosi, T. I.
2010AGUFMSH42A..05V Altcode:
During the recent solar minimum, the two STEREO spacecrafts have imaged
many Corotating Interaction Regions (CIRs) in the interplanetary
medium. The multi-spacecraft view of the CIRs during this period of
very low activity is a unique opportunity for validating solar wind
models. According to the National Oceanic and Atmospheric Administration
Space Weather Prediction Center the absolute minimum of Sunspots number
for solar cycle 23 happened during CR2077 (2008, November 20 through
December 17). We use this rotation to perform a multi-spacecraft
validation study for a recently developed three-dimensional
two-temperature and Alfvén wave driven global solar wind model
within the Space Weather Modeling Framework (SWMF). We compare the
CIRs of this model with in situ STEREO A and B, ACE/WIND as well as
Venus Express. Near the Sun, we validate the numerical model with the
density obtained from the solar rotational tomography on LASCO-C2 data
of SOHO in the height range of 2.4 to 6 Rsun and electron temperature
and density from differential emission measure tomography on STEREO
A and B EUVI images in the height range of 1.035 to 1.225 Rsun.
---------------------------------------------------------
Title: Imaging Asteroid (21) Lutetia with OSIRIS onboard Rosetta
(Invited)
Authors: Keller, H.; Barbieri, C.; Koschny, D.; Lamy, P. L.; Rickman,
H.; Rodrigo, R.; Sierks, H.; OSIRIS Team
2010AGUFM.P14B..02K Altcode:
The Optical, Spectroscopic, and Infrared Remote Imaging System
OSIRIS observed the asteroid (21) Lutetia during the fly-by of ESA’s
Rosetta spacecraft on 10. July 2010. Observations with the narrow angle
(NAC) and wide angle (WAC) cameras covered a large phase angle range
(from 10 deg during approach through near zero reaching almost 150
deg after closest approach (CA)). The large field of view (2048 x
2048 pixels) of the narrow angle camera (NAC) was almost filled by
the 100 km sized body at CA from a distance of 3160 km providing
a scale of 60 m per pixel. The rugged body of (21) Lutetia appears
to be shaped by an extensive collision history resulting in crater
diameters comparable to the mean radius of the asteroid. Most of
the visible northern hemisphere is scarred by numerous craters and
therefore geologically old. However, several recent large impacts have
covered their surroundings with thick layers of regolith. In addition
to a wide variety of crater shapes a large diversity of geological
features can be discerned: ridges, grabens, pits, landslides, talus,
and boulders (> 150 m) and boulder tracks. Grooves are pervasive,
radially aligned or concentric around recent craters, often cutting
older craters indicating strong seismic activity caused by frequent
impacts. In contrast to the observations of asteroid (2867) Steins
weak variations of the surface albedo and colour variegations can be
discerned and correlated with surface features. The observed opposition
effect will constrain the properties of the regolith such as its grain
size. The spectrum of Lutetia over the wavelength range of 250 to 1000
nm covered by the filters of the WAC and NAC is flat and hence Lutetia
does not appear as red as Steins. Detailed photometric modeling taking
advantage of the wide range of phase angles and spectral coverage will
be combined and iterated with digital terrain models to describe the
surface topography down to the resolution limit of the images and the
overall shape to Lutetia.
---------------------------------------------------------
Title: Multi-color, rotationally resolved photometry of asteroid 21
Lutetia from OSIRIS/Rosetta observations
Authors: Lamy, P. L.; Faury, G.; Jorda, L.; Kaasalainen, M.; Hviid,
S. F.
2010A&A...521A..19L Altcode:
Context. Asteroid 21 Lutetia is the second target of the Rosetta space
mission. Extensive pre-encounter, space-, and ground-based observations
are being performed to prepare for the flyby in July 2010. <BR />
Aims: The aim of this article is to accurately characterize the
photometric properties of this asteroid over a broad spectral range
from the ultraviolet to the near-infrared and to search for evidence of
surface inhomogeneities. <BR /> Methods: The asteroid was imaged on 2
and 3 January 2007 with the Narrow Angle Camera (NAC) of the Optical,
Spectroscopic, and Infrared Remote Imaging System (OSIRIS) during
the cruise phase of the Rosetta spacecraft. The geometric conditions
were such that the aspect angle was 44^circ (i.e., mid-northern
latitudes) and the phase angle 22.4^circ. Lutetia was continuously
monitored over 14.3 h, thus exceeding one rotational period and a
half, with twelve filters whose spectral coverage extended from 271
to 986 nm. An accurate photometric calibration was obtained from
the observations of a solar analog star, 16 Cyg B. <BR /> Results:
High-quality light curves in the U, B, V, R and I photometric bands
were obtained. Once they were merged with previous light curves from
over some 45 years, the sidereal period is accurately determined:
P<SUB>rot</SUB> = 8.168271 ± 0.000002 h. Color variations with
rotational phase are marginally detected with the ultraviolet
filter centered at 368 nm but are absent in the other visible and
near-infrared filters. The albedo is directly determined from the
observed maximum cross-section obtained from an elaborated shape model
that results from a combination of adaptive-optics imaging and light
curve inversion. Using current solutions for the phase function, we find
geometric albedos p<SUB>V</SUB> = 0.130 ± 0.014 when using the linear
phase function and p<SUB>V</SUB>(H-G) = 0.180 ± 0.018 when using the
(H-G) phase function, which incorporates the opposition effect. The
spectral variation of the reflectance indicates a steady decrease with
decreasing wavelength rather than a sharp fall-off. <P />Photometric
tables (Tables 4 to 8) are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/521/A19">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/521/A19</A>
---------------------------------------------------------
Title: Visible-wavelength Observations of Jupiter-family Comet Nuclei
as Part of Seppcon.
Authors: Pittichova, Jana; Lowry, S. C.; Laird, R.; A'Hearn, M. F.;
Bauer, J. M.; Campins, H.; Fernández, Y.; Fitzsimmons, A.; Groussin,
O.; Hsieh, H.; Kelley, M.; Lamy, P.; Licandro, J.; Lisse, C. M.;
Meech, K. J.; Reach, W. T.; Snodgrass, C.; Toth, I.; Weaver, H. A.;
Weaissman, P.
2010DPS....42.2826P Altcode: 2010BAAS...42..964P
We present the latest analysis and results from SEPPCoN (Survey of
Ensemble Physical Properties of Cometary Nuclei). This on-going survey
involves studying 100 JFCs - about 25% of the known population - at both
mid-infrared and visible wave-lengths to constrain the distributions of
sizes, shapes, spins, and albedos of this population. Having earlier
reported results from measuring thermal emissions of our sample
nuclei [1,2,3,4], we report here progress on the visible-wavelength
observations that we have obtained at many ground-based facilities
in Chile, Spain, and the United States. To date we have attempted
observations of 91% of our sample of 100 JFCs, and at least 64 of
those were successfully detected. In most cases the comets were at
heliocentric distances between 3.0 and 6.5 AU so as to decrease the
odds of a comet having a coma. Of the 64 detected comets, 48 were
apparently bare, having no extended emission. Our datasets are further
augmented by archival data and photometry from the NEAT program [5]. An
important goal of SEPPCoN is to accumulate a large comprehensive set
of high quality physical data on cometary nuclei in order to make
accurate statistical comparisons with other minor-body populations
such as Trojans, Centaurs, and Kuiper-belt objects. Information
on the size, shape, spin-rate, albedo and color distributions is
critical for understanding their origins and evolutionary processes
affecting them. <P />This work was supported in part by grants from NASA
(NNX09AB44G) and NSF (AST-0808004). <P />[1] Fernandez, Y., et al. 2008,
Asteroids Comets Mete-ors 2008, LPI Co. No. 1405, paper id. 8307. <P
/>[2] Kelley, M., et al. 2008, Asteroids Comets Meteors 2008, LPI
Co. No. 1405, paper id. 8272. <P />[3] Groussin, O., et al. 2009,
Icarus 199, 568. <P />[4] Licandro, J., et al. 2009, A&A 507,
1667. <P />[5] Bauer, J., et al. 2010, AAS Meeting 216, paper 409.01.
---------------------------------------------------------
Title: A collision in 2009 as the origin of the debris trail of
asteroid P/2010A2
Authors: Snodgrass, Colin; Tubiana, Cecilia; Vincent, Jean-Baptiste;
Sierks, Holger; Hviid, Stubbe; Moissi, Richard; Boehnhardt, Hermann;
Barbieri, Cesare; Koschny, Detlef; Lamy, Philippe; Rickman, Hans;
Rodrigo, Rafael; Carry, Benoit; Lowry, Stephen C.; Laird, Ryan J. M.;
Weissman, Paul R.; Fitzsimmons, Alan; Marchi, Simone; OSIRIS Team
2010Natur.467..814S Altcode: 2010arXiv1010.2883S
The peculiar object P/2010A2 was discovered in January 2010 and given
a cometary designation because of the presence of a trail of material,
although there was no central condensation or coma. The appearance of
this object, in an asteroidal orbit (small eccentricity and inclination)
in the inner main asteroid belt attracted attention as a potential
new member of the recently recognized class of main-belt comets. If
confirmed, this new object would expand the range in heliocentric
distance over which main-belt comets are found. Here we report
observations of P/2010A2 by the Rosetta spacecraft. We conclude that
the trail arose from a single event, rather than a period of cometary
activity, in agreement with independent results. The trail is made up
of relatively large particles of millimetre to centimetre size that
remain close to the parent asteroid. The shape of the trail can be
explained by an initial impact ejecting large clumps of debris that
disintegrated and dispersed almost immediately. We determine that this
was an asteroid collision that occurred around 10 February 2009.
---------------------------------------------------------
Title: VizieR Online Data Catalog: 21 Lutetia UBVRI light curves
(Lamy+, 2010)
Authors: Lamy, P.; Faury, G.; Jorda, L.; Kaasalainen, M.; Hviid, S. F.
2010yCat..35210019L Altcode: 2010yCat..35219019L
The asteroid was imaged on 2 and 3 January 2007 with the Narrow Angle
Camera (NAC) of the Optical, Spectroscopic, and Infrared Remote Imaging
System (OSIRIS) during the cruise phase of the Rosetta spacecraft. The
geometric conditions were such that the aspect angle was 44° (i.e.,
mid-northern latitudes) and the phase angle 22.4°. Lutetia was
continuously monitored over 14.3h, thus exceeding one rotational period
and a half, with twelve filters whose spectral coverage extended from
271 to 986nm. An accurate photometric calibration was obtained from
the observations of a solar analog star, 16 Cyg B. <P />(5 data files).
---------------------------------------------------------
Title: The P/2010 A2 Asteroid Collision Confirmed by Rosetta/OSIRIS
Observation
Authors: Snodgrass, Colin; Tubiana, C.; Vincent, J.; Sierks, H.;
Hviid, S.; Moissl, R.; Boehnhardt, H.; Barbieri, C.; Koschny, D.;
Lamy, P.; Rickman, H.; Rodrigo, R.; Carry, B.; Lowry, S. C.; Laird,
R. J. M.; Weissman, P. R.; Fitzsimmons, A.; Marchi, S.; OSIRIS Team
2010DPS....42.3933S Altcode:
The discovery of P/2010 A2 by the LINEAR survey in January 2010 revealed
an object displaying a large trail of material similar in shape to
a cometary tail although no central condensation or coma could be
detected. The appearance of this object in an asteroidal orbit in the
inner main belt attracted attention as a potential new member of the
Main Belt Comets class (MBCs) but the discovery of a nucleus, with
an estimated diameter of 120 m, around 1500 km away from the trail
implied that the extended object we were seeing could be the debris
trail from a recent collision rather than the tail of a comet. Due to
the low inclination of its orbit, it is difficult to conclude about the
nature of P/2010 A2 from Earth-based data only, as different scenarios
lead to the same appearance in the orbital configuration at the times
of observations. We present here another set of images, acquired from
the unique viewing geometry provided by ESA's Rosetta spacecraft en
route to comet 67P/Churyumov-Gerasimenko. Albeit faint (22 magnitude),
the object could be observed by the high-resolution camera OSIRIS. We
used a Finson-Probstein model to simulate the shape of the trail, and
estimate the time of emission and β parameter (ratio between solar
radiation pressure and gravity) for the dust grains. Simulations were
compared to the OSIRIS images and ground based observations acquired
at NTT and Palomar telescopes. Thanks to the different phase angle
provided by Rosetta, we could reduce the number of solutions to a
unique model, leading to the conclusive demonstration that the trail
is due to a single event rather than a period of cometary activity.
---------------------------------------------------------
Title: Properties And Distribution Of The Craters Of Asteroid (21)
Lutetia From The Rosetta\Osiris Fly-by
Authors: Besse, Sebastien; Lamy, P.; Jorda, L.; Groussin, O.; Marchi,
S.; Debei, S.; Da Deppo, V.; Ferri, F.; Keller, H. U.; Kueppers,
M.; Massironi, M.; Moissl, R.; Sierks, H.; Thomas, N.; Tubiana, C.;
Vincent, J.; OSIRIS Team
2010DPS....42.3903B Altcode: 2010BAAS...42R1032B
The Rosetta spacecraft of the European Space Agency performed
successfully its second flyby of an asteroid on July 10 2010 on its
way to its final target comet 67p/Churyumov-Gerasimenko. Main belt
asteroid (21) Lutetia has been observed by the OSIRIS experiment at
a distance of 3160 km. The best resolution of the images is about 59
meters per pixel, numerous geological features can be distinguished
at this scale. We report on here the physical characteristics and
properties of the craters of the largest (100km in diameter) asteroid
ever observed in-situ. The values of the diameter and the depth of
the craters are essential to determine the age of the surface based
on crater counting and the evolution of the surface. Preliminary
observations already attest for a highly impacted surface with very
large craters. Displacement of regolith is seen on the surface and
especially in the walls of craters. The properties of the craters
will help understand the history and evolution of this large scale
and possible primordial body.
---------------------------------------------------------
Title: Hints on the Puzzling 21 Lutetia Nature from OSIRIS Rosetta
Data
Authors: Barucci, Maria Antonieta; Sierks, H.; Barbieri, C.; Koschny,
D.; Lamy, P.; Rickman, H.; Rodrigo, R.; Keller, U. H.; OSIRIS Team
2010DPS....42.4301B Altcode: 2010BAAS...42.1043B
From the ground based observations, 21 Lutetia appeared to be a
puzzling asteroid different from all the other asteroids. Its nature was
uncertain because of contradictory observations, either favoring an M
type or a C type asteroid. From polarimetry (Belskaya et al. 2010, AA,
515, 29), Lutetia appeared an atypical object with a surface covered
by a fine-grained regolith. <P />From the amazing images received by
OSIRIS imaging system (Keller et al. 2007 SSRev. 128, 433), on board of
ESA Rosetta spacecraft, Lutetia reveals a complex and morphologically
diverse surface. <P />Lutetia seems to be a very old object with an
irregular shape which is the result of its collisional history. Some
smooth younger areas have been also observed. The asteroid lifelong
bombardment produced several big craters (tens of kilometers), and
many different generations of smaller craters. An apparently thick
regolith layer probably covers most of the surface of the asteroid and
its presence is revealed by the unique land slide structures along the
walls of some craters, most likely generated by impact-induced seismic
activity. The presence inside some big craters of sparse boulders,
apparently dark, indicates a complex impact mechanism. Moreover images
display a great richness of different structures: pits, craters chains,
ridges, scarps and wide younger terrains. More details will be available
at the time of the presentation. An overview of the obtained results
will be presented. <P />The first analysis of the data shows the
extreme diversity of Lutetia which does not resemble any other space
explored asteroid. The variety of shapes, morphologies, structures,
histories provides us with an invaluable patrimony of information.
---------------------------------------------------------
Title: Shape and Physical Properties of Asteroid 21 Lutetia from
OSIRIS Images
Authors: Jorda, Laurent; Lamy, P.; Besse, S.; Capanna, C.; Carry,
B.; Faury, G.; Gaskell, R.; Gesquière, G.; Groussin, O.; Gutiérrez,
P.; Kaasalainen, M.; Sabolo, W.; Sierks, H.; Spjuth, S.; OSIRIS Team
2010DPS....42.4303J Altcode: 2010BAAS...42.1043J
The Rosetta spacecraft of the European Space Agency flew by the asteroid
21 Lutetia on July, 10, 2010 on its way to its final target, comet
67P/Churyumov-Gerasimenko. A total of 460 images have been acquired by
OSIRIS during the flyby, with a minimum pixel scale of 64 m at closest
approach (hereafter "CA") with the narrow angle camera. Several filters
have been used, covering a wavelength range from the far UV (0.25
microns) to the end of the visible spectrum (1.0 microns). The phase
angle went through 11°-0°-160°, reaching opposition 18 min before
CA. We report here on a preliminary interpretation of the images of the
asteroid acquired by OSIRIS, the imaging system aboard Rosetta. These
images are combined with pre-flyby light curves and adaptive optics
measurements to retrieve the shape and the rotational parameters of
the asteroid. The bulk physical properties: size, surface, volume,
moments of inertia, gravity field, are then extracted from the shape.
---------------------------------------------------------
Title: Thermal properties of asteroids 21 Lutetia and 2867 Steins
from Spitzer Space Telescope observations
Authors: Groussin, O.; Lamy, P. L.; Fornasier, S.; Jorda, L.;
Kaasalainen, M.; Carry, B.
2010epsc.conf...55G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hektor : a space mission towards Jupiter Trojans
Authors: Lamy, P.; Poncy, J.; Martinot, V.; Jorda, L.; Delsanti, A.;
Groussin, O.
2010epsc.conf..138L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Asteroid collision confirmed by Rosetta/OSIRIS observations
Authors: Vincent, J. -B.; Snodgrass, C.; Tubiana, C.; Sierks, H.;
Hviid, S.; Moissl, R.; Böhnhardt, H.; Barbieri, C.; Koschny, D.;
Lamy, P.
2010epsc.conf..634V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: 21 Lutetia: Overview of results from OSIRIS images
Authors: Sierks, H.; Barbieri, C.; Koschny, D.; Lamy, P.; Rickman,
H.; Rodrigo, R.; OSIRIS Team
2010epsc.conf..664S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The shape and physical properties of asteroid 2867 Steins
from OSIRIS images
Authors: Lamy, P.; Jorda, L.; Spjuth, S.; Besse, S.; Marchi, S.;
Barbieri, C.; Gaskell, R.; Groussin, O.; Kaasalainen, M.; Keller, H. U.
2010epsc.conf..204L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: THERMAP: a thermal infrared spectro-imager for space missions
to small bodies of the solar system
Authors: Brageot, E.; Groussin, O.; Lamy, P.; Reynaud, J. -L.;
Fargant, G.
2010epsc.conf...51B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Restitution of multiple overlaid components on extremely long
series of solar corona images
Authors: Llebaria, A.; Loirat, J.; Lamy, P.
2010ada..confE..12L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The shape and physical properties of asteroid 21 Lutetia from
OSIRIS images
Authors: Jorda, L.; Lamy, P.; Besse, S.; Capanna, C.; Carry, B.;
Faury, G.; Gaskell, R.; Gesquiere, G.; Groussin, O.; Kaasalainen, M.
2010epsc.conf..200J Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Three-Dimensional Electron Density from Tomographic Analysis
of LASCO-C2 Images of the K-Corona Total Brightness
Authors: Frazin, Richard A.; Lamy, Philippe; Llebaria, Antoine;
Vásquez, Alberto M.
2010SoPh..265...19F Altcode: 2010SoPh..tmp...79F
We present the first quantitative three-dimensional (3D) tomographic
reconstructions of electron density from coronagraph measurements of
the K-corona's total brightness (B) made by LASCO-C2 on SOHO. This
is possible because new calibrations of the LASCO-C2 images in both
polarized brightness (pB) and B have now been made for the entire
mission. The B and pB reconstructions are compared, and the differences
are explained in terms of line of sight weighting functions in Thomson
scattering. We conclude that the LASCO-C2 B archive, which is vastly
larger than the pB archive, will be a very valuable resource for
determining the 3D electron density throughout the SOHO mission which
started taking data in 1996.
---------------------------------------------------------
Title: Analytic and experimental determination of ghosts in the
Rosetta Narrow-Angle Camera and their impact on imaging performance
Authors: Dohlen, Kjetil; Jorda, Laurent; Lamy, Philippe; Toth, Imre;
Origne, Alain
2010SPIE.7731E..49D Altcode: 2010SPIE.7731E.138D
The Rosetta cometary rendezvous mission, one of ESA's cornerstone
missions, was launched in 2004 and will be inserted in orbit around
comet 67P/Churyumov-Gerasimenko in 2014. One of its instruments, the
Osiris Narrow Angle Camera (NAC), will take high-resolution images
of the comet and map its nucleus as well as the jets of gas and dust
emanating from localized areas. This is quite challenging as the
contrast between the radiance of these jets and that of the nucleus is
expected to be of the order of 1/1000. A major limitation comes from
the presence of multiple ghosts which results from the presence of two
filters and a protective window in front of the CCD detector. Rigorous
knowledge of these instrumental ghost images is therefore required. We
present analytical models of the structure and intensity of these
ghosts, compare them with pre and post-launch observations, and describe
image analysis tools developed to handle them.
---------------------------------------------------------
Title: The cratering history of asteroid (2867) Steins
Authors: Marchi, S.; Barbieri, C.; Küppers, M.; Marzari, F.;
Davidsson, B.; Keller, H. U.; Besse, S.; Lamy, P.; Mottola, S.;
Massironi, M.; Cremonese, G.
2010P&SS...58.1116M Altcode: 2010arXiv1003.5655M
The cratering history of main belt asteroid (2867) Steins has been
investigated using OSIRIS imagery acquired during the Rosetta flyby
that took place on the 5th of September 2008. For this purpose, we
applied current models describing the formation and evolution of main
belt asteroids, that provide the rate and velocity distributions of
impactors. These models coupled with appropriate crater scaling laws,
allow the cratering history to be estimated. Hence, we derive Steins'
cratering retention age, namely the time lapsed since its formation
or global surface reset. We also investigate the influence of various
factors - like bulk structure and crater erasing - on the estimated age,
which spans from a few hundred Myrs to more than 1 Gyr, depending on
the adopted scaling law and asteroid physical parameters. Moreover,
a marked lack of craters smaller than about 0.6 km has been found and
interpreted as a result of a peculiar evolution of Steins cratering
record, possibly related either to the formation of the 2.1 km wide
impact crater near the south pole or to YORP reshaping.
---------------------------------------------------------
Title: Stray light analysis and optimization of the ASPIICS/PROBA-3
formation flying solar coronagraph
Authors: Mazzoli, A.; Landini, F.; Vives, S.; Lamy, P.; Halain, J. P.;
Rochus, P.
2010SPIE.7731E..46M Altcode: 2010SPIE.7731E.135M
PROBA-3 is a technology mission devoted to the in-orbit demonstration
of formation flying techniques and technologies. PROBA-3 will implement
a giant coronagraph (called ASPIICS) that will both demonstrate and
exploit the capabilities and performances of formation flying. ASPIICS
is distributed on two spacecrafts separated by 150m, one hosting
the external occulting disk and the other the optical part of the
coronagraph. This part implements a three-mirror-anastigmat (TMA)
telescope. Its pupil is placed about 800mm in front of the primary
mirror, a solution allowing an efficient baffling and a high reduction
of the stray light inside the instrument. A complete stray light
analysis of the TMA has been carried out to design the baffles and to
establish the required roughness of the mirrors. The analysis has been
performed in two steps: first, by calculating the diffraction pattern
behind the occulter due to an extended monochromatic source having the
diameter of the Sun; second, by propagating this diffraction pattern,
through all the telescope optical components, to the prime focal
plane. The results obtained are described in this article.
---------------------------------------------------------
Title: Demonstrator of the formation flying solar coronagraph
ASPIICS/PROBA-3
Authors: Vives, Sébastien; Damé, Luc; Lamy, Philippe; Antonopoulos,
A.; Bon, W.; Capobianco, G.; Crescenzio, G.; da Deppo, V.; Ellouzi,
M.; Garcia, J.; Guillon, C.; Mazzoli, A.; Soilly, T.; Stathopoulos,
F.; Tsiganos, C.
2010SPIE.7731E..47V Altcode: 2010SPIE.7731E.136V
Formation Flying opens the possibility to conceive and deploy giant
solar coronagraphs in space permanently reproducing the optimum
conditions of a total eclipse of the Sun ("artificial" eclipse) thus
giving access to the inner corona with unprecedented spatial resolution
and contrast (low stray light). The first opportunity to implement such
a coronagraph "ASPIICS" will be offered by the European Space Agency
(ESA) PROBA-3 technology mission devoted to the in-orbit demonstration
of formation flying technologies. Two spacecrafts separated by about 150
m form a giant externally-occulted coronagraph: the optical part hosted
by one spacecraft remains entirely protected from direct sunlight
by remaining in the shadow of an external occulter hosted by the
other spacecraft. We developed and tested a scale-model 'breadboard'
(i.e., 30m) of the PROBA-3/ASPIICS Formation Flying coronagraph. The
investigations focused on two metrology systems capable of measuring
both the absolute pointing of the coronagraph (by sensing the projected
shadow and penumbra produced by the external occulting disk) and
the alignment of the formation (by re-imaging light sources located
on the rear-side of the occulting disk with the optical part of the
coronagraph). In this contribution, we will describe the demonstrator
and report on our results on the crucial question of the alignment and
pointing in space of long instruments (> 100 m) with an accuracy of
a few arcsec. This study has been conducted in the framework of an ESA
"STARTIGER" Initiative, a novel approach aimed at demonstrating the
feasibility of a new and promising technology on a very short time scale
(six months).
---------------------------------------------------------
Title: ASPIICS: a giant coronagraph for the ESA/PROBA-3 Formation
Flying Mission
Authors: Lamy, Philippe; Damé, Luc; Vivès, Sébastien; Zhukov, Andrei
2010SPIE.7731E..18L Altcode: 2010SPIE.7731E..31L
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and the
vignetted pupil which degrades the spatial resolution prevent useful
observations of the white light corona inside typically 2-2.5 solar
radii. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs using a
two-component space system with the external occulter on one spacecraft
and the optical instrument on the other spacecraft at a distance of
hundred meters. Such an instrument, ASPIICS (Association de Satellites
Pour l'Imagerie et l'Interférométrie de la Couronne Solaire), has
just been selected by the European Space Agency (ESA) to fly (launch
expected in 2014) on its third PROBA (Project for On-Board Autonomy)
mission of formation flying demonstration which is presently in phase
B. It will perform both high spatial resolution imaging of the solar
corona as well as 2- dimensional spectroscopy of several emission
lines (in particular the forbidden line of FeXIV at 530.285 nm) from
the coronal base out to 3 solar radii. For this, it will use filters,
polarisers and a solid Fabry-Perot interferometer ("étalon"). The
classical design of an externally-occulted coronagraph is adapted to the
formation flying configuration allowing the detection of the very inner
corona as close as 0.04-0.05 solar radii (40-50 arcsec) from the solar
limb. By tuning the position of the occulter spacecraft, it may even be
possible to reach the chromosphere and the upper part of the spicules.
---------------------------------------------------------
Title: Measurements and optimization of the occulting disk for the
ASPIICS/PROBA-3 formation flying solar coronagraph
Authors: Landini, Federico; Mazzoli, Alexandra; Venet, Melanie;
Vivès, Sébastien; Romoli, Marco; Lamy, Philippe; Rossi, Guglielmo
2010SPIE.7735E..4DL Altcode: 2010SPIE.7735E.146L
Solar coronagraphs in formation ying require several mechanical and
technological constraints to be met. One of the most critical issues is
the external occulter design and its optimization. The occulter edge
requires special attention in order to minimize the diraction while
being compatible with the constraints of handling and integrating large
delicate space components. Moreover, it is practically impossible to
realize a full scale model for laboratory tests. This article describes
the results of tests performed with a scaled-model breadboard of the
ASPIICS coronagraph disk edge, using the Articial Sun facility at
Laboratoire d'Astrophysique de Marseille.
---------------------------------------------------------
Title: Towards a New Formation Flying Solar Coronagraph
Authors: Lamy, P.; Vives, S.; Curdt, W.; Dame, L.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Kuzin, S.; Schmutz, W.; Tsinganos,
K.; Turck-Chieze, S.; Zhukov, A.
2010ASPC..424...15L Altcode:
We briefly describe an investigation aiming at the development of a
giant solar coronagraph instrument onboard of two satellites, separated
by about 150 m in formation flight for the detailed observation of the
solar coronal plasma. The European Space Agency (ESA) has selected this
instrument as the only payload onboard the Proba 3 satellites which
will be launched in 2013. The Greek team is developing the command
control board of the coronagraph.
---------------------------------------------------------
Title: The Solar Wind as Seen by SOHO/SWAN Since 1996: Comparison
with SOHO/LASCO C2 Coronal Densities
Authors: Lallement, R.; Quémerais, E.; Lamy, P.; Bertaux, J. -L.;
Ferron, S.; Schmidt, W.
2010ASPC..428..253L Altcode: 2010arXiv1003.4243L
We update the SOHO/SWAN H Lyman-α brightness analysis to cover the
1996-2008 time interval. A forward model applied to the intensity
maps provides the latitude and time dependence of the interstellar
hydrogen ionization rate over more than a full solar cycle. The hydrogen
ionization, being almost entirely due to charge-exchange with solar
wind ions, reflects closely the solar wind flux. Our results show
that the solar wind latitudinal structure during the present solar
minimum is strikingly different from the previous minimum, with a
much wider slow solar wind equatorial belt which persists until at
least the end of 2008. We compute absolute values of the in-ecliptic H
ionization rates using OMNI solar wind data and use them to calibrate
our ionization rates at all heliographic latitudes. We then compare
the resulting fluxes with the synoptic LASCO/C2 electron densities at
6 solar radii. The two time-latitude patterns are strikingly similar
over all the cycle. This comparison shows that 6 R<SUB>s</SUB> densities
can be used to infer the solar wind type close to its source, with high
(low) densities tracing the slow (fast) solar wind, simply because the
density reflects the altitude at which the acceleration occurs. The
comparison between the two minima suggests that the fast polar wind
acceleration occurs at a larger distance during the current minimum
compared to the previous one. This difference, potentially linked to
the magnetic field decrease and/or the coronal temperature decrease
should be reproduced by solar wind expansion models.
---------------------------------------------------------
Title: Thermal properties of asteroid 21 Lutetia from Spitzer Space
Telescope observations
Authors: Lamy, P. L.; Groussin, O.; Fornasier, S.; Jorda, L.;
Kaasalainen, M.; Barucci, M. A.
2010A&A...516A..74L Altcode:
Context. Asteroid 21 Lutetia is the second target of the Rosetta
space mission with a flyby scheduled in July 2010. To best prepare the
observational campaign, Lutetia is being extensively characterized by
ground- and space-based astronomical facilities. <BR /> Aims: We used
the Spitzer Space Telescope (SST) to determine the thermal properties
of Lutetia and more generally, to contrain its physical properties
and nature. <BR /> Methods: The observations were performed with the
infrared spectrograph (IRS) of the SST on 10 and 11 December 2005,
when the asteroid was 2.81 AU from the Sun, 2.65 AU from the SST and
at a phase angle of 21°. We obtained 14 spectra ranging from 5.2 to
38.0 μm, and sampling the rotational period of the asteroid. They were
interpreted with a standard thermal model incorporating the thermal
inertia. <BR /> Results: We obtained the first thermal light curve
of Lutetia. Using the most recent solution for its three-dimensional
shape and rotational state, as well as independently determined
parameters such as the albedo, we satisfactorily reproduced the 14
spectral energy distributions and the complete thermal light curve
of Lutetia. The best thermal model has a thermal inertia I ≤ 30
JK<SUP>-1</SUP>m<SUP>-2</SUP>s<SUP>-1/2</SUP> and a beaming factor in
the range ~0.70-0.83. This low thermal inertia is typical of main belt
asteroids and implies that the surface of Lutetia is likely covered
by a thick regolith layer. Since the beaming factor only reflects the
effects of surface rugosity, the above range implies a high degree of
roughness. In addition, our results show evidence of inhomogeneities
in the surface roughness in the equatorial band of Lutetia.
---------------------------------------------------------
Title: A Hundred Comets: The Visual-Wavelength Observations of the
Survey of Ensemble Physical Properties of Cometary Nuclei (SEPPCoN)
Authors: Bauer, James M.; Fernandez, Y. R.; Lowry, S. C.; Meech, K. J.;
Fitzsimmons, A.; Snodgrass, C.; Pittichova, J.; Weaver, H. A.; Lisse,
C. M.; A'Hearn, M. F.; Campins, H.; Groussin, O.; Kelley, M. S.;
Lamy, P. L.; Licandro, J.; Reach, W. T.; Toth, I.
2010AAS...21640901B Altcode: 2010BAAS...41..816B
We present new results from SEPPCoN, a Survey of Ensemble Physical
Properties of Cometary Nuclei. This project is currently surveying
100 Jupiter-family comets (JFCs) to measure the mid-infrared thermal
emission and visible reflected sunlight of the nuclei. The scientific
goal is to determine the distributions of radius, geometric albedo,
thermal inertia, axial ratio, and color among the JFC nuclei. In the
past we have presented results from the completed mid-IR observations
of our sample [1]; here we present preliminary results from ongoing,
broadband visible-wavelength observations of nuclei obtained from a
variety of ground-based facilities (Mauna Kea, Cerro Pachon, La Silla,
La Palma, Apache Point, Table Mtn., and Palomar Mtn.), including
contributions from the Near Earth Asteroid Telescope project (NEAT)
archive. The nuclei were observed at high heliocentric distance (usually
over 4 AU) and so many comets show either no or little contamination
from dust coma. While several nuclei have been observed as snapshots,
we have multiepoch photometry for many of our targets. With our datasets
we are building a large database of photometry, and such a database
is essential to the derivation of albedo and shape of a large number
of nuclei, and to the understanding of biases in the survey. Support
for this work was provided by NSF and the NASA Planetary Astronomy
program. Reference: [1] Fernandez, Y.R., et al. 2007, BAAS 39, 827.
---------------------------------------------------------
Title: The nucleus of comet C/1983 H1 IRAS-Araki-Alcock
Authors: Groussin, O.; Lamy, P. L.; Jorda, L.
2010P&SS...58..904G Altcode:
We present a synthetic analysis of all available infrared (2-20 μm)
and radio (1.3-6.1 cm) observations of comet C/1983 H1 IRAS-Araki-Alcock
performed during its close approach to Earth in May 1983. We implement a
model based on a spherical nucleus with a macroscopic mosaic of small
and numerous active and inactive regions, and take into account the
strong phase effect in the calculations of the thermal flux (often
neglected in past interpretations). The orientation of the spin axis
is assumed to be that determined by Sekanina [1988. Astron. J. 95,
1876-1894]. Additional constraints coming from visible photometry,
measurements of the water production rate and the temporal variations
of the cometary activity are introduced. We derive an equivalent
nucleus radius of 3.4±0.5 km, consistent with a geometric albedo of
0.04 ±0.01 and a phase coefficient β=0.04mag deg in the visible,
and an active fraction of 2.9 ±1.9%. Although the nucleus is probably
elongated as found in the past ( Sekanina, 1988), we show that the
relevant measurements were likely contaminated by the contribution of
a variable coma.
---------------------------------------------------------
Title: The solar wind flux and acceleration height as seen by
SOHO/SWAN and LASCO/C2
Authors: Lallement, Rosine; Quemerais, Eric; Bertaux, Jean-Loup;
Lamy, Philippe; Schmidt, Walter
2010EGUGA..12.8445L Altcode:
We present an update of the SOHO/SWAN H Lyman-alpha data to cover
the 1996-2009 time interval. A forward model applied to the intensity
maps provides the latitude and time dependence of the interstellar H
ionisation rate over more than a full solar cycle. This ionisation,
being almost entirely due to charge-exchange with solar wind ions,
reflects closely the solar wind flux. We show that the solar
wind latitudinal structure during the present solar minimum is
strikingly different from the previous minimum, with a much wider
slow solar wind equatorial belt which persists until at least the
end of 2008. After calibration of our 3D ionisation rates on OMNI
in-ecliptic data, we compare the resulting solar wind fluxes with the
synoptic LASCO/C2 electron densities at 6 Rs. The two time-latitude
patterns are strikingly similar over all the cycle, high (resp. low)
H ionisation and 6Rs coronal densities tracing the slow (resp. fast)
solar wind. This is because the H ionisation reflects the solar wind
flux and speed, while the coronal density reflects at which altitude
occurs the acceleration. The comparison between the two minima
of activity suggests that the high latitude fast wind accelerates
at larger distance from the Sun surface during the current minimum
compared to the previous one. This difference, potentially linked to
the magnetic field decrease or(and) the coronal temperature decrease
should be reproduced by solar wind expansion models.
---------------------------------------------------------
Title: The Interstellar H Flow: Updated Analysis of SOHO/SWAN Data
Authors: Lallement, Rosine; Quémerais, Eric; Koutroumpa, Dimitra;
Bertaux, Jean-Loup; Ferron, Stéphane; Schmidt, Walter; Lamy, Philippe
2010AIPC.1216..555L Altcode: 2014arXiv1405.3474L
We update two kinds of results obtained with the SWAN instrument on
board SOHO. First, we use H cell data recorded in 2001 and derive
the H flow direction in the same way the study was done at solar
minimum. We again compare with the Helium flow direction and doing
so correct for the coordinate system change between the Ulysses and
SOHO missions. The deflection plane we obtain is compatible with our
previous result within error bars, confirming the potential predominant
role of the interstellar magnetic field. In a second part, we extend
the computation of the interstellar H ionization as a function of
heliographic latitude and time, a quantity which reflects closely
the SW flux latitudinal structure. The pattern for the present solar
minimum is strikingly different from the previous minimum, with a much
wider slow solar wind equatorial belt which persists until at least
2008. Comparing with synoptic LASCO/C2 electron densities we infer
from a preliminary study that the acceleration of the high speed solar
wind occurs at a higher altitude during this minimum compared to the
previous one, a difference expansion models must be able to reproduce.
---------------------------------------------------------
Title: Photometric Study of the Kreutz Comets Observed by SOHO from
1996 to 2005
Authors: Knight, Matthew M.; A'Hearn, Michael F.; Biesecker, Douglas
A.; Faury, Guillaume; Hamilton, Douglas P.; Lamy, Philippe; Llebaria,
Antoine
2010AJ....139..926K Altcode:
We present analysis of the photometry of more than 900 Kreutz comets
observed by SOHO from 1996 to 2005. The Kreutz comets have "sungrazing"
orbits with q≈ 1-2 R <SUB>sun</SUB>, high inclinations (i ≈ 143°),
and periods of 500-1000 years. We find that they do not have a bimodal
distance of peak brightness as previously reported, but instead peak
from 10.5 R <SUB>sun</SUB> to 14 R <SUB>sun</SUB> (prior to perihelion),
suggesting there is a continuum of compositions rather than two
distinct subpopulations. The light curves have two rates of brightening,
typically vprop r <SUP>-7.3 ± 2.0</SUP> when first observed by SOHO
(at distances of 30-35 R <SUB>sun</SUB>) then rapidly transitioning
to vprop r <SUP>-3.8 ± 0.7</SUP> between 20 R <SUB>sun</SUB> and 30 R
<SUB>sun</SUB>. It is unclear at what distance the steeper slope begins,
but it likely does not extend much beyond the SOHO field of view. We
derive nuclear sizes up to ~50 m in radius for the SOHO-observed comets,
with a cumulative size distribution of N(>R) vprop R <SUP>-2.2</SUP>
for comets larger than 5 m in radius. This size distribution cannot
explain the largest members of the family seen from the ground,
suggesting that either the size distribution does not extend to the
largest sizes or that the distribution is not uniform around the
orbit. The total mass of the distribution up to the largest expected
size (~500 m) is ~4 × 10<SUP>14</SUP> g, much less than the estimated
masses of the largest ground-observed members. After correcting for
the changing discovery circumstances, the flux of comets reaching
perihelion has increased since 1996, and the increase is seen in
comets of all sizes. Comparison of the SOHO comets with the Solwind
and Solar Maximum Mission discoveries suggests there may have been an
overabundance of bright comets arriving from 1979 to 1989, possibly
indicative of a changing distribution around the Kreutz orbit.
---------------------------------------------------------
Title: Coronal Fine Linear Rays: Are They Fast Streams From Active
Regions?
Authors: Koutchmy, Serge; Lamy, Philippe; Viladrich, Christian;
Filippov, Boris; Nikoghossian, Arthur; Golub, Leon
2010AIPC.1216..339K Altcode:
Eclipse observations of the W-L corona show linear rays above active
regions at times of solar maximum. We show that these linear rays are
also observed in the field-of-view of the C2-LASCO coronagraph, in
perfect correspondence with the eclipse results. A selected prominent
case taken from the 2001 eclipse observation in Angola is analysed
with several different methods, including the use of a synoptic map
constructed using SoHO/LASCO C2 images. A clear signature of time
variations near the eclipse observation is detected, suggesting that
at least some parts of the beam are collimated. These observations
strongly suggest high speed streams that apparently ignore the potential
large scale coronal magnetic field rooted rather low in the corona. A
possible origin is the neutral magnetic points located above the
active region. Several mechanisms exist to explain how the plasma is
accelerated in these regions to large quasi-relativistic velocities,
possibly related to the occurrence of type III radio bursts. We point
out a curious analogy with phenomena occurring inside coronal holes.
---------------------------------------------------------
Title: Properties of Comet Nuclei
Authors: Lamy, P. L.; Toth, I.; Fernandez, Y. R.; Weaver, H. A.
2010PDSS.8122E....L Altcode:
This data set presents tables 1, 2, 3, 4, 5 and 7 of 'Sizes, Shapes,
Albedos, and Colors of Cometary Nuclei' (Lamy et al., 2004), and
includes references for the sources cited. The authors culled this data
from published or well-known unpublished sources, and have indicated
what they judge to be the most reliable value available.
---------------------------------------------------------
Title: HiRISE Mission to Address the Dynamical Chromosphere-Corona
Interface
Authors: Damé, Luc; Lamy, Philippe; von Fay-Siebenburgen Erdélyi,
Robert
2010cosp...38.2844D Altcode: 2010cosp.meet.2844D
Several ground facilities and space missions are currently dedicated
to the study of the Sun at high resolution and of the solar corona
in particular. However, and despite significant progress with the
advent of space missions and UV, EUV and XUV direct observations of
the hot chro-mosphere and million degrees coronal plasma, much is yet
to be achieved in the understanding of these high temperatures, fine
dissipative structures and of the coronal heating in general. Recent
missions have shown the definite role of waves and of the magnetic
field deep in the inner corona, at the chromosphere-corona interface,
where dramatic changes occur. The dynamics of the chromosphere and
corona is controlled by the emerging magnetic field, guided by the
coronal magnetic field. Accordingly, the direct measurement of the
chromospheric and coronal magnetic fields is of prime importance. The
solar corona consists of many thin loops or threads with the plasmas
brightening and fading independently. The dynamics in each thread is
believed to be related to the formation of filaments, each one being
dynamic, in a non-equilibrium state. The mechanism sustaining that
dynamics, oscillations or waves (Alfvén or MHD?), require both very
high-cadence, multi-spectral observations, and high resolution. This
is foreseen in the future Space Mission HiRISE, the ultimate new
generation ultrahigh resolution, interferomet-ric and coronagraphic,
Solar Physics Mission, proposed for ESA Cosmic Vision (pre-selected
in 2007, and under preparation for 2012 second call). HiRISE (High
Resolution Imaging and Spectroscopy Explorer), at the L1 Lagrangian
point, provides meter class FUV imaging and spectro-imaging, EUV and
XUV imaging and spectroscopy, and ultimate coronagraphy by a remote
external occulter (satellites in formation flying 280 m apart) allowing
to characterize temperature, densities and velocities in the solar upper
chromosphere, transition zone and inner corona with, in particular, 2D
very high resolution multi-spectral imaging-spectroscopy, direct coronal
magnetic field measurement: a unique set of tools to understand the
structuration and onset of coronal heating. We give a detail account
of the proposed mission profile, major scien-tific objectives and
model payload of HiRISE, a natural complement to the Solar Probe type
missions lacking duty cycle, high resolution, spatial, spectral and
temporal multi-temperature diagnostics and full coronal magnetometry.
---------------------------------------------------------
Title: ASPIICS / PROBA-3 formation flying externally-occulted giant
coronagraph mission
Authors: Lamy, Philippe; Damé, Luc
2010cosp...38.1882L Altcode: 2010cosp.meet.1882L
During the time operation of the Helios mission, from 1974 to
metricconverterProductID1986, a1986, a large number of magnetic clouds
was identified by the magnetic field and solar wind sensors onboard
the probes. Among these magnetic clouds, some of them were identified
by at least two probes, provided that IMP-8 and ISEE-3 were monitoring
the dayside magnetosphere. The magnetic cloud observed on from DOY 029
to DOY 030/1977 by Helios 1, Helios 2, and IMP-8 represents a potential
multi-spacecraft observed magnetic cloud. Despite the interaction with
the high-speed stream that compressed the magnetic cloud, the minimum
variance analysis technique showed the same direction of rotation of
the magnetic field inside the magnetic cloud. This helped to associate
the observation of the magnetic cloud at multi-spacecraft.
---------------------------------------------------------
Title: ASPIICS / PROBA-3: a formation flying externally-occulted
giant coronagraph mission
Authors: Lamy, Philippe; Damé, Luc; Curdt, W.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Howard, R.; Kuzin, S.; Schmutz,
W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.2858L Altcode: 2010cosp.meet.2858L
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are detailed.
---------------------------------------------------------
Title: Physical properties of asteroid 2867 Steins
Authors: Keller, Horst Uwe; Jorda, Laurent; Spjuth, Sofie; Lamy,
Philippe; Groussin, Olivier; Schroder, Stefan; Marchi, Simone;
Kueppers, Michael; Gaskell, Robert
2010cosp...38..632K Altcode: 2010cosp.meet..632K
ESA's spacecraft Rosetta passed the E-type asteroid 2867
Steins on 5. Sept. 2009 on its way to a rendezvous with comet
67P/Churyumov-Gerasimenko. The scientific camera system OSIRIS took
several hundred images. The best resolution of 160 m (2 pixel) was
achieved at a closest approach of 803 km. The images show an oblate body
with an effective spherical diameter of 5.3 km. A large crater of 2.1
km in diameter suggests that Steins is a rubble pile. Its conical shape
could be the result of YORP spin-up. A lack of small craters indicates
a rather recent resurfacing event. Disk resolved photometry based on a
shape model constructed from trian-gular facets and using the formalism
of Hapke (1993, 2002) constrains the surface properties. On its inbound
leg the spacecraft passed near zero phase angle and the photometry of
the op-position effect suggests that both shadow-hiding and coherent
backscattering are present. The optically relevant regolith surface of
Steins appears to be porous, consisting of fine transparent grains. The
geometric albedo calculated from the Hapke parameters can be compared
to the value derived directly from the images near zero phase angle.
---------------------------------------------------------
Title: Multi-spacecraft observation of a magnetic cloud
Authors: de Lucas, Aline; Dal Lago, Alisson; Schwenn, Rainer; Clúa de
Gonzalez, Alicia L.; Marsch, Eckart; Lamy, Philippe; Damé, Luc; Curdt,
W.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Howard, R.;
Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.1921D Altcode: 2010cosp.meet.1921D
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are presented.
---------------------------------------------------------
Title: Restitution of multiple overlaid components on extremely long
series of solar corona images
Authors: Llebaria, A.; Loirat, J.; Lamy, P.
2010SPIE.7533E..0YL Altcode: 2010SPIE.7533E..25L
This contribution describes the methods used to accurately disentangle
the components observed on a very large series of images of the solar
corona. This series consists of 12 years of continuous observations
provided by the LASCO/C2 coronagraph aboard SOHO (the SOlar and
Heliospheric Observatory). Continuously centred on the Sun, which is
masked, the observed images display a blend of many components. The
more conspicuous are the K-corona from the coronal plasma, the F-corona
from the coronal dust and the instrumental straylight. All of them are
optically thin but in the LASCO/C2 field of view only the K-corona is
polarized. The set of observations is composed of two huge series of
images: the "polarization series" (at least one observation every day)
and the "white light series" (more than 50 images every day). The goal
is to determine quantitatively the evolution of each image component
during the 12 years. Assuming 1) a small and slow temporal evolution
for the F-corona and straylight, 2) the 2D regularity of the F-corona
and 3) the ability to deduce the influence of the SOHO-Sun distance,
the F-corona function is determined from the polarized series and
afterwards subtracted of the white light series to obtain the K-corona
white light series.
---------------------------------------------------------
Title: E-Type Asteroid (2867) Steins as Imaged by OSIRIS on Board
Rosetta
Authors: Keller, H. U.; Barbieri, C.; Koschny, D.; Lamy, P.; Rickman,
H.; Rodrigo, R.; Sierks, H.; A'Hearn, M. F.; Angrilli, F.; Barucci,
M. A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.;
De Cecco, M.; Debei, S.; Fornasier, S.; Fulle, M.; Groussin, O.;
Gutierrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg,
J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. -M.; Lazzarin,
M.; Moreno, J. Lopez; Marzari, F.; Michalik, H.; Naletto, G.; Sabau,
L.; Thomas, N.; Wenzel, K. -P.; Bertini, I.; Besse, S.; Ferri, F.;
Kaasalainen, M.; Lowry, S.; Marchi, S.; Mottola, S.; Sabolo, W.;
Schröder, S. E.; Spjuth, S.; Vernazza, P.
2010Sci...327..190K Altcode:
The European Space Agency’s Rosetta mission encountered the main-belt
asteroid (2867) Steins while on its way to rendezvous with comet
67P/Churyumov-Gerasimenko. Images taken with the OSIRIS (optical,
spectroscopic, and infrared remote<SUP> </SUP>imaging system) cameras
on board Rosetta show that Steins is an oblate body with an effective
spherical diameter of 5.3 kilometers. Its surface does not show color
variations. The morphology of Steins is dominated by linear faults
and a large 2.1-kilometer-diameter crater near its south pole. Crater
counts reveal a distinct lack of small craters. Steins is not solid
rock but a rubble pile and has a conical appearance that is probably
the result of reshaping due to Yarkovsky-O’Keefe-Radzievskii-Paddack
(YORP) spin-up. The OSIRIS images constitute direct evidence for the
YORP effect on a main-belt asteroid.
---------------------------------------------------------
Title: OASIS: a simulator to prepare and interpret remote imaging
of solar system bodies
Authors: Jorda, L.; Spjuth, S.; Keller, H. U.; Lamy, P.; Llebaria, A.
2010SPIE.7533E..11J Altcode: 2010SPIE.7533E..28J
We present a new tool, called "OASIS" (Optimized Astrophysical Simulator
for Imaging Systems), whose aim is to generate synthetic calibrated
images of solar system bodies. OASIS has been developed to support the
operations and the scientific interpretation of visible images acquired
by the OSIRIS visible camera aboard the Rosetta spacecraft, but it
can be used to create synthetic images taken by the visible imaging
system of any spacecraft. OASIS allows takes as input the shape model
of the object, in the form of triangular facets defining its surface,
geometric parameters describing the position and orientation of the
objects included in the scene and of the observer, and instrumental
parameters describing the geometric and radiometric properties of the
camera. The rendering of the object is performed in several steps which
involve: (i) sorting the triangular facets in planes perpendicular
to the direction of the light source and to the direction of the
line-of-sight, (ii) tracing rays from a given facet to the light source
and to the observer to check if it is illuminated and in view from
the observer, (iii) calculating the intersection between the projected
coordinates of the facets and the pixels of the image, and finally (iv)
radiometrically calibrating the images. The pixels of the final image
contain the expected signal from the object in digital numbers (DN). We
show in the article examples of synthetic images of the asteroid (2867)
Steins created with OASIS, both for the preparation of the flyby and
for the scientific interpretation of the acquired images later on.
---------------------------------------------------------
Title: On the 3-D reconstruction of Coronal Mass Ejections using
coronagraph data
Authors: Mierla, M.; Inhester, B.; Antunes, A.; Boursier, Y.; Byrne,
J. P.; Colaninno, R.; Davila, J.; de Koning, C. A.; Gallagher, P. T.;
Gissot, S.; Howard, R. A.; Howard, T. A.; Kramar, M.; Lamy, P.;
Liewer, P. C.; Maloney, S.; Marqué, C.; McAteer, R. T. J.; Moran, T.;
Rodriguez, L.; Srivastava, N.; St. Cyr, O. C.; Stenborg, G.; Temmer,
M.; Thernisien, A.; Vourlidas, A.; West, M. J.; Wood, B. E.; Zhukov,
A. N.
2010AnGeo..28..203M Altcode:
Coronal Mass ejections (CMEs) are enormous eruptions of magnetized
plasma expelled from the Sun into the interplanetary space, over the
course of hours to days. They can create major disturbances in the
interplanetary medium and trigger severe magnetic storms when they
collide with the Earth's magnetosphere. It is important to know their
real speed, propagation direction and 3-D configuration in order to
accurately predict their arrival time at the Earth. Using data from
the SECCHI coronagraphs onboard the STEREO mission, which was launched
in October 2006, we can infer the propagation direction and the 3-D
structure of such events. In this review, we first describe different
techniques that were used to model the 3-D configuration of CMEs in
the coronagraph field of view (up to 15 R⊙). Then, we apply these
techniques to different CMEs observed by various coronagraphs. A
comparison of results obtained from the application of different
reconstruction algorithms is presented and discussed.
---------------------------------------------------------
Title: PHYSICAL PROPERTIES OF STEINS' CRATERS
Authors: Besse, S.; Lamy, P. L.; Marchi, S.; Jorda, L.
2009AGUFM.P11C1235B Altcode:
The ROSETTA spacecraft, on its way to rendez-vous comet
67P/Churyumov-Gerasimenko, has successfully flew by asteroid 2867
Steins in September 2008. The OSIRIS experiment (Keller et al,
2007) has imaged the asteroid both with the Wide Angle Camera (WAC)
and the Narrow Angle Camera (NAC). The resolutions of the images are
sufficient to distinguish features on the surface, especially craters
which are detected all over the observed part of the asteroidal surface
(44%). In this study, we focus on the physical properties of the craters
and particularly theirs diameters and depths which we can compare with
others small bodies previously observed. Starting from the first shape
model of the asteroid (Besse et al, 2009), we add artificial craters
that best match the observations and correlate the simulated images and
the real images. The highest correlation yields the diameter and the
depth of the craters. The average Depth/Diameter ratio for Steins is
0.12. However, these values are quite heterogeneous and ranged from 0.04
to 0.25. These results are in agreement with previous studies: 0.15 for
Ida (Sullivan et al, 1996) and 0.14 for Gaspra (Carr et al,1994). The
difference is likely due to the resurfacing of the surface by the large
impact that occurs on the south pole of Steins with a diameter of 2100
meters. Craters with extreme values of the Depth/Diameter ratio are
located in the vicinity of this large crater and may be related to the
large impact. Shallower craters could have been filled by ejecta or
regolith displacement, while steeper craters could result from fault
basin related to the impact or simply be recent events.
---------------------------------------------------------
Title: Spitzer observations of the asteroid-comet transition object
and potential spacecraft target 107P (4015) Wilson-Harrington
Authors: Licandro, J.; Campins, H.; Kelley, M.; Fernández, Y.;
Delbó, M.; Reach, W. T.; Groussin, O.; Lamy, P. L.; Toth, I.;
A'Hearn, M. F.; Bauer, J. M.; Lowry, S. C.; Fitzsimmons, A.; Lisse,
C. M.; Meech, K. J.; Pittichová, J.; Snodgrass, C.; Weaver, H. A.
2009A&A...507.1667L Altcode: 2009arXiv0910.0116L
Context: Near-Earth asteroid-comet transition object 107P/ (4015)
Wilson-Harrington is a possible target of the joint European Space
Agency (ESA) and Japanese Aerospace Exploration Agency (JAXA) Marco Polo
sample return mission. Physical studies of this object are relevant
to this mission, and also to understanding its asteroidal or cometary
nature.<BR /> Aims: Our aim is to obtain significant new constraints on
the surface thermal properties of this object.<BR /> Methods: We present
mid-infrared photometry in two filters (16 and 22 μm) obtained with
NASA's Spitzer Space Telescope on February 12, 2007, and results from
the application of the Near Earth Asteroid Thermal Model (NEATM). We
obtained high S/N in two mid-IR bands allowing accurate measurements
of its thermal emission. <BR /> Results: We obtain a well constrained
beaming parameter (η = 1.39±0.26) and obtain a diameter and geometric
albedo of D = 3.46±0.32 km, and p<SUB>V</SUB> = 0.059±0.011. We also
obtain similar results when we apply this best-fitting thermal model
to single-band mid-IR photometry reported by Campins et al. (1995,
P&SS, 43, 733), Kraemer et al. (2005, AJ, 130, 2363) and Reach et
al. (2007, Icarus, 191, 298).<BR /> Conclusions: The albedo of 4015
Wilson-Harrington is low, consistent with those of comet nuclei and
primitive C-, P-, D-type asteorids. We establish a rough lower limit
for the thermal inertia of W-H of 60 Jm<SUP>-2</SUP>s<SUP>-0.5</SUP>
K<SUP>-1</SUP> when it is at r = 1 AU, which is slightly over the
limit of 30 Jm<SUP>-2</SUP> s<SUP>-0.5</SUP> K<SUP>-1</SUP> derived
by Groussin et al. (2009, Icarus, 199, 568) for the thermal inertia
of the nucleus of comet 22P/Kopff.
---------------------------------------------------------
Title: Tomography with LASCO-C2 Total Brightness Images
Authors: Frazin, R. A.; Llebaria, A.; Lamy, P. L.
2009AGUFMSH44A..08F Altcode:
The recently completed calibration of the K-corona total brightness
(B) images from the SOHO/LASCO archive offers the opportunity for
3D reconstruction of the corona's electron density from a vastly
larger data set than is available from the polarized brightness (pB)
images. Since the B has a different line-of-sight weighting than the pB,
the two may be combined to provide more information than is available
from either one (this fact has already been exploited to locate CME
centers of mass), leading to better results. Here, we present the first
tomography based on B images and compare the results to those based
on pB images and the combination of pB and B images. Implications
for time-dependent tomography and improved modeling the of F-corona
are discussed.
---------------------------------------------------------
Title: Properties of the nuclei and comae of 13 ecliptic comets from
Hubble Space Telescope snapshot observations
Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; A'Hearn, M. F.;
Jorda, L.
2009A&A...508.1045L Altcode:
Context: Knowledge of the size distribution of cometary nuclei and, more
generally, of their physical properties is important for constraining
models of the formation and evolution of the Solar System. <BR /> Aims:
We report on our on-going effort to determine the ensemble properties
of comets based on our success in detecting the nuclei of active comets
with the Hubble Space Telescope (HST). <BR /> Methods: During cycle
8 (July 1999 to June 2000), we observed 13 ecliptic comets with the
planetary camera 2 through at least two filters (V and R) and up to four
(B, V, R, I) for the brightest ones. The ~30 min of HST observational
time devoted to each comet did not permit a proper determination
of light curves, so our “snapshot” observations yield effective
radii, not shapes. <BR /> Results: Assuming spherical nuclei with a
geometric albedo of 0.04 for the R band (except 0.024 for 10P/Tempel
2, as independently measured) and a phase law of 0.04 mag/deg, we
obtained the following effective radii: 4P/Faye: 1.77 km, 10P/Tempel
2: 5.98 km, 17P/Holmes: 1.71 km, 37P/Forbes: 0.81 km 44P/Reinmuth 2:
1.61 km, 50P/Arend: 0.95 km, 59P/Kearns-Kwee: 0.79 km, 63P/Wild 1:
1.46 km, 71P/Clark: 0.68 km, 84P/Giclas: 0.90 km, 106P/Schuster:
0.94 km, 112P/Urata-Niijima: 0.90 km, 114P/Wiseman-Skiff: 0.78 km. In
our present sample, eight out of thirteen nuclei have sub-kilometer
radii. The average color of the observed nuclei is (V-R) = 0.52±0.04,
which is significantly redder than the Sun. We determined the dust
activity parameter Afρ of their coma in the R band, and estimated the
dust production rates. The average reflectivity gradient of the dust
comae of six comets is S' [670,792 nm] = 15.2±2.3% per kÅ.<BR /> <P
/>Based on observations made with the NASA/ESA Hubble space telescope,
obtained at Space Telescope Science Institute, which is operated by
the Association of Universities for Research in Astronomy under NASA
contract NAS 5-26555.
---------------------------------------------------------
Title: The Thermal Emission of Comet 8P/tuttle Nucleus as Observed
with the Plateau de Bure Interferometer
Authors: Boissier, Jeremie; Bockelée-Morvan, D.; Groussin, O.; Biver,
N.; Colom, P.; Crovisier, J.; Jorda, L.; Lamy, P.; Moreno, R.
2009DPS....41.2001B Altcode:
Measuring the thermal emission of cometary nuclei allows the
determination of albedo-independent sizes for comets that are
not visited by space probes. In the IR, the atmosphere makes such
observations difficult from the ground, so that space telescopes
(ISO, Spitzer) are frequently used to observe cometary nuclei. In
the millimeter range, single dish observations are mainly sensitive
to the dust coma. Interferometric measurements are required but
restricted up to now to two cometary nuclei from the Oort cloud
(Hyakutake, Hale-Bopp). <P />The Halley type comet 8P/Tuttle made
a close approach to the Earth in January 2008 (geocentric distance
of 0.25 AU). Previous studies suggested that its nucleus was large
(7.8 km radius) and faintly active. As a result this comet was a
good target for interferometric observations of its nucleus thermal
emission at millimeter wavelengths. <P />8P/Tuttle was observed at
240 GHz (1.25 mm) with the IRAM interferometer on the Plateau de Bure
in January 2008. The thermal emission of the nucleus was detected and
found to be lower than expected, corresponding to an apparent radius
close to 2 km. Independant observations carried out with Hubble and
Spitzer space telescopes indicate a slightly larger size (2.8 km
radius) and were used to build a shape and thermal emission model of
8P nucleus (Groussin et al., A&A suubmitted). We used this model
to interpret the Plateau de Bure data and we present here the results
of this analysis. <P />Observations of cometary nuclei in millimeter
interferometry will grow up in number in the forthcoming years with
the upgrading of current instruments and the opening of ALMA. This
will increase the sample of observed nuclei from all the comet dynamic
classes and enable further studies of their physical properties.
---------------------------------------------------------
Title: Exploring Potential Surface Heterogeneity of the Asteroid
Steins observed from the Rosetta OSIRIS Instrument
Authors: Leyrat, Cedric; Jorda, L.; Fornasier, S.; Fulchignoni,
M.; Barucci, A.; Belskaya, I.; Lamy, P.; Groussin, O.; Charnoz, S.;
Keller, H.; Sierks, H.; Hviid, S.; OSIRIS Team
2009DPS....41.5003L Altcode:
Asteroid 2867 Steins is the first E type asteroid visited by a
spacecraft. During the Rosetta flyby in September 2008, the OSIRIS
NAC and WAC cameras have obtained several disk-resolved images in
visible wavelengths, at different phase angles. At closest approach,
the spatial resolution of the WAC images was about 80m/pixel, allowing
looking for potential surface heterogeneity. <P />We have applied the
G-mode multivariate statistical method (Coradini et al, 1977) to both
NAC and WAC images obtained around closest approach, at different
wavelengths, from 295 to 986 nm. The geometric parameters have been
retrieved with the SPICE routines. The shape of Steins is assumed to be
represented by a polyhedron of almost 58000 facets. The OASIS simulator
(developed at LAM and MPS) has been used to retrieve the I/F quantity
of each visible 'facet' of the asteroid 3D shape model. Thereafter,
photometric corrections have been performed using the Hapke (2002)
model to eliminate the variable illuminations conditions at the
surface. The G-mode classification method has been performed on a
limited number of facets, in a region limited to [-50,+70] deg. in
latitude and [-20,+90] deg. in longitude. <P />Moreover, a gravity
map of the asteroid has been obtained on the basis of the shape model
considering a homogeneous internal density. <P />Here we present our
results on the potential presence of compositional heterogeneities at
the surface of Steins and of gravitational anomalies, and we discuss
their possible implications on the evolution of the asteroid.
---------------------------------------------------------
Title: The Physical Properties of Asteroid 2867 Steins
Authors: Lamy, Philippe L.; Jorda, L.; Gaskell, R.; Besse, S.;
Groussin, O.; Kaasalainen, M.; OSIRIS Team
2009DPS....41.5901L Altcode:
We will present an overview of the physical properties of the E-type
asteroid 2867 Steins from the OSIRIS campaign during the Rosetta flyby
(September 2008), from ground-based observations, and from recent
thermal spectroscopy obtained with the Spitzer space telescope. A
complete shape solution has been obtained from the combination of
resolved images and inversion of light curves. We will discuss the
properties of the impact craters, the formation of the large crater and
its consequences on topographic features and the possible influence
of the YORP effect in shaping Steins. We will review and confront
the various sources of information on the composition and surface
photometric properties of Steins.
---------------------------------------------------------
Title: New perspective in solar coronal physics: Giant externally
occulted coronagraphs using satellites in flight formation
Authors: Lamy, P.; Vivès, S.
2009AcAau..65..273L Altcode:
Formation flying opens new perspectives in solar physics, and
allow to conceive giant, externally occulted coronagraphs using
a two-component space system with the external occulter on one
spacecraft and the optical instrument on the other spacecraft at a
distance of 100 m. ASPIICS (Association de Satellites Pour l'Imagerie
et l'Interférométrie de la Couronne Solaire) is a mission proposed
to ESA in the framework of its PROBA-3 demonstration program of
formation flying which is presently in phase A. ASPIICS is a single
coronagraph which will perform both high spatial resolution imaging of
the solar corona as well as two-dimensional spectroscopy of several
emission lines from the coronal base out to 3R<SUB>⊙</SUB> using
an étalon Fabry-Pérot interferometer. The classical design of an
externally occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.01R<SUB>⊙</SUB> from the solar limb. By tuning the position
of the occulter spacecraft, it will even be possible to reach the
chromosphere and the upper part of the spicules.
---------------------------------------------------------
Title: The ARTEMIS Catalog of LASCO Coronal Mass Ejections. Automatic
Recognition of Transient Events and Marseille Inventory from
Synoptic maps
Authors: Boursier, Y.; Lamy, P.; Llebaria, A.; Goudail, F.; Robelus, S.
2009SoPh..257..125B Altcode:
The LASCO-C2 coronagraph aboard the SOHO solar observatory has been
providing a continuous flow of coronal images since 1996. Synoptic
maps for each Carrington rotation have been built from these images,
and offer a global view of the temporal evolution of the solar corona,
particularly the occurrence of transient events. Coronal Mass Ejections
(CMEs) present distinct signatures thus offering a novel approach to the
problem of their identification and characterization. We present in this
article an automated method of detection based on their morphological
appearance on synoptic maps. It is based on adaptive filtering and
segmentation, followed by merging with high-level knowledge. The
program builds a catalog which lists the CMEs detected for each
Carrington Rotation, together with their main estimated parameters:
time of appearance, position angle, angular extent, average velocity
and intensity. Our final catalog LASCO-ARTEMIS (Automatic Recognition
of Transient Events and Marseille Inventory from Synoptic maps) is
compared with existing catalogs, CDAW, CACTUS and SEEDS. We find that,
likewise the automated CACTUS and SEEDS catalogs, we detect many more
events than the CDAW catalog which is based on visual detection. The
total number of detected CMEs strongly depends upon the sensitivity
to small, faint and numerous events.
---------------------------------------------------------
Title: The colors of cometary nuclei—Comparison with other primitive
bodies of the Solar System and implications for their origin
Authors: Lamy, P.; Toth, I.
2009Icar..201..674L Altcode:
We present new color results of cometary nuclei obtained with the
Hubble Space Telescope (HST) whose superior resolution enables
us to accurately isolate the nucleus signals from the surrounding
comae. By combining with scrutinized available data obtained with
ground-based telescopes, we accumulated a sample of 51 cometary nuclei,
44 ecliptic comets (ECs) and 7 nearly-isotropic comets (NICs) using
the nomenclature of Levison [Levison, H.F., 1996. In: Rettig, T.W.,
Hahn, J.M. (Eds.), Completing the Inventory of the Solar System. In:
ASP Conf. Ser., vol. 107, pp. 173-192]. We analyze color distributions
and color-color correlations as well as correlations with other
physical parameters. We present our compilation of colors of 232
outer Solar System objects—separately considering the different
dynamical populations, classical KBOs in low and high-inclination
orbits (respectively CKBO-LI and CKBO-HI), resonant KBOs (practically
Plutinos), scattered-disk objects (SDOs) and Centaurs—of 12 candidate
dead comets, and of 85 Trojans. We perform a systematic analysis of all
color distributions, and conclude by synthesizing the implications of
the dynamical evolution and of the colors for the origin of the minor
bodies of the Solar System. We find that the color distributions are
remarkably consistent with the scenarios of the formation of TNOs
by Gomes [Gomes, R.S., 2003. Icarus 161, 404-418] generalized by the
"Nice" model [Levison, H.F., Morbidelli, A., VanLaerhoven, Ch., Gomes,
R., Tsiganis, L., 2008. Icarus 196, 258-273], and of the Trojans
by Morbidelli et al. [Morbidelli, A., Levison, H.F., Tsiganis, K.,
Gomes, R., 2005. Nature 435, 462-465]. The color distributions of the
Centaurs are globally similar to those of the CKBO-HI, the Plutinos
and the SDOs. However the potential bimodality of their distributions
allows to possibly distinguish two groups based on their (B-R) index:
Centaur I with (B-R)>1.7 and Centaurs II with (B-R)<1.4. Centaurs
I could be composed of TNOs (prominently CKBO-LI) and ultra red objects
from a yet unstudied family. Centaurs II could consist in a population
of evolved objects which have already visited the inner Solar System,
and which has been scattered back beyond Jupiter. The diversity of
colors of the ECs, in particular the existence of very red objects,
is consistent with an origin in the Kuiper belt. Candidate dead comets
represent an ultimate state of evolution as they appear more evolved
than the Trojans and Centaurs II.
---------------------------------------------------------
Title: Three-Dimensional Kinematics of Coronal Mass Ejections from
STEREO/SECCHI-COR2 Observations in 2007 - 2008
Authors: Boursier, Y.; Lamy, P.; Llebaria, A.
2009SoPh..256..131B Altcode:
We present a new method to perform the three dimensional
characterization of coronal mass ejections (CMEs) using stereoscopic
images obtained with the STEREO/SECCHI-COR2 coronagraphs. Two approaches
are proposed, and each associated algorithm gives the trajectory of the
CME and its kinematical properties (velocity and acceleration profiles)
intended for space weather forecast. The first approach is based on
forward modeling appropriate to the reconstruction of surfaces in
an optically thin medium, and performs a local approximation of the
observed CME by a hemispherical shell, thus tracking the leading edge
of the event. The second approach is based on tracking the center
of gravity of the radiance of the CME in the images. More than 16
000 blind tests have been performed to assess the performance of
each algorithm. For that purpose, we used three distinct libraries
of simulated images of CMEs that correspond to three CME models:
hemispherical shell, flux rope, and cloud-like. The two methods are
applied to a set of CMEs observed in 2007 and 2008 by the SECCHI-COR2
coronagraphs, and when possible, our results are compared to those
already published. The determinations of the direction of propagation
and of the velocity are generally found in good agreement.
---------------------------------------------------------
Title: Imaging Asteroid (2867) Steins with OSIRIS onboard Rosetta
Authors: Keller, H.; A'Hearn, M.; Angrilli, F.; Barbieri, C.; Barucci,
A.; Bertaux, J.; Cremonese, G.; Davidson, B.; de Cecco, M.; Debei,
S.; Fulle, M.; Groussin, O.; Gutierrez, P.; Hviid, S.; Ip, W.; Jorda,
L.; Knollenberg, J.; Koschniy, D.; Kramm, J.; Kührt, E.; Küppers,
M.; Lamy, P.; Lara, L.; Lopez Moreno, J.; Marzari, F.; Michalik,
H.; Naletto, G.; Rickmann, H.; Rodrigo, R.; Sabau, L.; Sierks, H.;
Thomas, N.; Wenzel, P.; Lazzarin, M.
2009AGUSM.P12A..02K Altcode:
The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS
observed the E-type asteroid (2867) Steins during the fly-by of ESA's
Rosetta spacecraft. Observations over a large phase angle range (from
near 0 to 140) by the scientific camera system OSIRIS revealed the
illuminated hemisphere of the asteroid's diamond-like shaped body
with a mean radius of 2.7 km and a projected surface at zero phase
angle of 5.3 x 3.9 km2. A large crater (diameter 2 km) is evidence of
an almost disastrous impact and implies that Steins is not a solid
rock. More than 30 craters or crater-like features with diameters
> 150 m are identified. 7 round concavities are arranged along a
line pointing radially away from the big impact crater. The shape and
volume of asteroid Steins is derived from models based on the images
of both OSIRIS cameras and earlier observations of the photometric
light curves. Its resemblance to a spinning top suggests that it was
influenced by the YORP effect making it the first optical observation
of such a body. Analysis of the images provide the disk integrated
albedo, reveal a strong opposition effect, and photometric properties
of the surface showing very little variegation. Its very uniform,
bright surface suggests that this asteroid is homogeneously formed
out of the igneous (magmatic) minerals found in enstatite achondrite
meteorites that are produced in melts requiring temperatures of more
than 1000 C. Consequently (2867) Steins is a fragment of the interior
of a large parent body.
---------------------------------------------------------
Title: Three-dimensional kinematics of coronal mass ejections from
STEREO/SECCHI-COR2 observations in 2007-2008
Authors: Boursier, Y.; Lamy, P.; Llebaria, A.
2009EGUGA..1112760B Altcode:
We present a new method to perform the three dimensional
characterization of coronal mass ejections (CMEs) using stereoscopic
images obtained with the STEREO/SECCHI-COR2 coronagraphs. Two approaches
are proposed, and each associated algorithms returns the trajectory
of the CME and its kinematics properties (velocity and acceleration
profiles) intended for space weather forecast. The first approach is
based on forward modeling appropriate to the reconstruction of surfaces
in an optically thin medium, and performs a local approximation
of the observed CME by an hemispherical shell, thus tracking the
leading edge of the event. The second approach is based on tracking
the center of gravity of the radiance of the CME on the images. More
than 16000 blind tests have been performed to assess the performances
of each algorithm. For that purpose, we used three distinct libraries
of simulated images of CMEs that correspond to three CME models:
hemispherical shell, flux rope, and cloud-like. The two methods are
applied to a set of CMEs observed in 2007 and 2008 by the SECCHI-COR2
coronagraphs, and when possible, our results are compared to those
already published. The determinations of the direction of propagation
and of the velocity are generally found in good agreement.
---------------------------------------------------------
Title: The DynaMICCS perspective. A mission for a complete and
continuous view of the Sun dedicated to magnetism, space weather
and space climate
Authors: Turck-Chièze, S.; Lamy, P.; Carr, C.; Carton, P. H.;
Chevalier, A.; Dandouras, I.; Defise, J. M.; Dewitte, S.; Dudok de Wit,
T.; Halain, J. P.; Hasan, S.; Hochedez, J. F.; Horbury, T.; Levacher,
P.; Meissonier, M.; Murphy, N.; Rochus, P.; Ruzmaikin, A.; Schmutz,
W.; Thuillier, G.; Vivès, S.
2009ExA....23.1017T Altcode: 2008ExA...tmp...42T
The DynaMICCS mission is designed to probe and understand the dynamics
of crucial regions of the Sun that determine solar variability,
including the previously unexplored inner core, the radiative/convective
zone interface layers, the photosphere/chromosphere layers and the
low corona. The mission delivers data and knowledge that no other
known mission provides for understanding space weather and space
climate and for advancing stellar physics (internal dynamics)
and fundamental physics (neutrino properties, atomic physics,
gravitational moments...). The science objectives are achieved
using Doppler and magnetic measurements of the solar surface,
helioseismic and coronographic measurements, solar irradiance at
different wavelengths and in-situ measurements of plasma/energetic
particles/magnetic fields. The DynaMICCS payload uses an original
concept studied by Thalès Alenia Space in the framework of the
CNES call for formation flying missions: an external occultation of
the solar light is obtained by putting an occulter spacecraft 150 m
(or more) in front of a second spacecraft. The occulter spacecraft,
a LEO platform of the mini sat class, e.g. PROTEUS, type carries
the helioseismic and irradiance instruments and the formation flying
technologies. The latter spacecraft of the same type carries a visible
and infrared coronagraph for a unique observation of the solar corona
and instrumentation for the study of the solar wind and imagers. This
mission must guarantee long (one 11-year solar cycle) and continuous
observations (duty cycle > 94%) of signals that can be very weak
(the gravity mode detection supposes the measurement of velocity
smaller than 1 mm/s). This assumes no interruption in observation
and very stable thermal conditions. The preferred orbit therefore is
the L1 orbit, which fits these requirements very well and is also an
attractive environment for the spacecraft due to its low radiation and
low perturbation (solar pressure) environment. This mission is secured
by instrumental R and D activities during the present and coming
years. Some prototypes of different instruments are already built
(GOLFNG, SDM) and the performances will be checked before launch on
the ground or in space through planned missions of CNES and PROBA ESA
missions (PICARD, LYRA, maybe ASPIICS).
---------------------------------------------------------
Title: ASPIICS, a giant externally occulted coronagraph for the
PROBA-3 formation flying mission
Authors: Vivès, S.; Lamy, P.; Koutchmy, S.; Arnaud, J.
2009AdSpR..43.1007V Altcode:
Formation flying opens new perspectives for coronal physics, and
allow to conceive giant, externally occulted coronagraphs using a
two-component space system with the external occulter on one spacecraft
and the optical instrument on the other spacecraft. ASPIICS (Association
de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne
Solaire) is a mission proposed to ESA in the framework of the PROBA-3
program of formation flying which is presently in phase A, to exploit
this technique for coronal observations. ASPIICS is composed of a
single coronagraph which performs high spatial resolution imaging of
the corona as well as 2-dimensional spectroscopy of several emission
lines from the coronal base out to 3 R<SUB>⊙</SUB>. The selected
lines allow to address different coronal regions: the forbidden
line of Fe XIV at 530.285 nm (coronal matter), Fe IX/X at 637.4 nm
(coronal holes), HeI at 587.6 nm (cold matter). An additional broad
spectral channel will image the white light corona so as to derive
electron densities. The classical design of an externally occulted
coronagraph is adapted to the detection of the very inner corona
as close as 1.01 R<SUB>⊙</SUB> and the addition of a Fabry-Perot
interferometer using a so-called " étalon". This paper is dedicated
to the description of the optical design and its critical components:
the entrance optics and the Fabry-Pérot interferometer. ASPIICS will
address the question of coronal heating and of the role of waves by
characterizing propagating fluctuations (waves and turbulence) in the
solar wind acceleration region and by looking for oscillations in the
intensity and Doppler shift of spectral lines. The combined imaging
and spectral diagnostics capabilities available with ASPIICS will
allow to map the velocity field of the corona both in the sky plane
(directly on the images) and along the line-of-sight by measuring
the Doppler shifts of emission lines. We will attempt to determine
how the different components of the solar wind, slow and fast are
accelerated. ASPIICS will observe the corona during the maximum of
solar activity, insuring the detection of many Coronal Mass Ejections
(CMEs). By rapidly alternating high resolution imaging and spectroscopy,
CMEs will be thoroughly characterized. In addition, ASPIICS will attempt
to characterize the topology of the magnetic field in the corona.
---------------------------------------------------------
Title: 3-Dimensional Reconstruction of Asteroid 2867 Steins
Authors: Besse, S.; Groussin, O.; Jorda, L.; Lamy, P.; Kaasalainen,
M.; Gesquiere, G.; Remy, E.; OSIRIS Team
2009LPI....40.1545B Altcode:
The OSIRIS imaging experiment has imaged asteroid Steins. We have
combined three methods to retrieve the shape: limbs, Point of Interest
and light curves. The mean radius of Steins is 2.7 ± 0.3km, for a
volume of 78 ± 30km^3 and a surface of 98 ± 25km^2.
---------------------------------------------------------
Title: The size and thermal properties of the nucleus of Comet
22P/Kopff
Authors: Groussin, O.; Lamy, P.; Toth, I.; Kelley, M.; Fernandez, Y.;
A'Hearn, M.; Campins, H.; Licandro, J.; Lisse, C.; Lowry, S.; Meech,
K.; Snodgrass, C.
2009Icar..199..568G Altcode:
We detected the nucleus of Comet 22P/Kopff at 4.87 AU from the Sun with
the two IRS peak-up cameras of the Spitzer Space Telescope on April
19, 2007. Using the thermal model of [Groussin, O., and 15 colleagues,
2007. Icarus 187, 16-25], we derive a nucleus size of 1.89±0.16 km, in
agreement with [Lamy, P., Toth, I., Jorda, L., Groussin, O., A'Hearn,
M.F., Weaver, H.A., 2002. Icarus 156, 442-455], and a thermal inertia
I⩽30 JKms.
---------------------------------------------------------
Title: Separation of limb and terminator on apparent contours of
solar system small bodies
Authors: Llebaria, A.; Jorda, L.; Groussin, O.; Gesquiere, G.; Lamy, P.
2009SPIE.7246E..10L Altcode: 2009SPIE.7246E..29L
Segmentation of contours and silhouettes is a recurrent topic in image
recognition and understanding. In this paper we describe a new method
used to divide in two parts (the limb and the terminator) the apparent
silhouette of an irregular astronomical body illuminated by a unique
source, the Sun. One of the main objectives of the asteroids and comets
flyby is the detailed 3D reconstruction of such bodies. However the
number of images obtained during a flyby is limited, as well as the
number of viewing geometries. In the 3D reconstruction we must consider
not only the camera motion but also the free rotation of the body. The
local brightness variations in the image vary with the rotation of the
body and with the changing body-camera distance. The topography at the
surface of the body can vary from very smooth to highly chaotic. In
the shape from silhouette 3D reconstruction methods, limb profiles are
used to retrieve the visual hull of the body. It is therefore required
to be able to separate the limb profiles from the terminator ones. In
this communication, we present a new method to perform this task based
on the local measurement of the contour smoothness, which we define
here as "activity". Developed in the framework of the Rosetta mission
our method has been tested on a large set of asteroid and comet images
taken during interplanetary missions. It looks robust to magnification
and enlightenment changes
---------------------------------------------------------
Title: Disk-Resolved Photometry of 9P/Tempel 1 and 2867 Steins
Authors: Laurent, Jorda; Spjuth, S.; Keller, H.; Lamy, P.; OSIRIS Team
2009DPS....40.2837L Altcode: 2009BAAS...41..559L
Disk-resolved photometric properties of asteroids have been obtained
on a sample of objects observed by space missions since the 80's. We
have developed a method to retrieve such properties from images
acquired by imaging instruments aboard spacecrafts. <P />We applied
the method to images of the nucleus of comet 9P/Tempel 1 acquired by
the DEEP IMPACT HRI camera, and we derived both local and global Hapke
parameters for the comet nucleus, as well as its geometric albedo. The
results have been compared to those obtained by Li et al. (Icarus 191,
161, 2007). We will also present very preliminary results on asteroid
2867 Steins observed by OSIRIS, the imaging system aboard ROSETTA,
after its flyby on Sept. 5, 2008.
---------------------------------------------------------
Title: Asteroid 21 Lutetia : UBVRI Light Curves from OSIRIS-NAC
Authors: Faury, Guillaume; Jorda, L.; Lamy, P.; Kaasalainen, M.;
Mottola, S.; OSIRIS Team
2009DPS....40.2838F Altcode: 2009BAAS...41..559F
We report on new observations aimed at characterizing asteroid 21
Lutetia, one of the targets of the Rosetta space mission. The asteroid
was imaged with the OSIRIS-NAC camera during the cruise phase of the
Rosetta spacecraft, at a phase angle of 22.36º, and was continuously
monitored over 14 hr (on 2 and 3 January 2007), thus covering one
rotational period and a half. From accurate photometric calibrations
with the solar analog star, 16 CygB, we have obtained high quality
light curves of 21 Lutetia in the U, B, V, R and I photometric bands. We
confirm a sidereal period of 8.17 hr. No spectral variations with the
rotation have been found. The resulting reflectivity spectrum is in
a very good agreement with that of Barucci et al. (2005). Combining
with existing observations, we have obtained its phase function.
---------------------------------------------------------
Title: First Results from the Rosetta Asteroid Steins Fly-by Observed
by OSIRIS and VIRTIS
Authors: Keller, Horst Uwe; Coradini, A.; Barbieri, C.; Koschny, D.;
Lamy, P.; Rickman, H.; Rodrigo, R.; Capaccioni, F.; Drossart, P.;
De Sanctis, M. C.; Arnold, G.; OSIRIS Science Team; VIRTIS Science Team
2009DPS....40.6010K Altcode: 2009BAAS...41..564K
On Sep 5<SUP>th</SUP> 2008 the ESA Rosetta spacecraft made a close
fly-by of the E-type asteroid (2867) Steins. During the fly-by the
asteroid was observed with the OSIRIS camera system and the VIRTIS
infrared imaging spectrometer. OSIRIS is composed of a wide-angle (100um
resolution) imager and a narrow angle (18.7um resolution) imager. VIRTIS
is an instrument that combines imaging and spectrometry in the Vis
and IR (0.25-5um), through a slit spectrometer(VIRTIS-M) with a high
resolution IR channel (VIRTIS-H). <P />Rosetta passed through zero
phase angle shortly before CA provided the opportunity to determine the
geometric albedo and the phase function of the asteroid. High spatial
resolution hyperspectral images were obtained by VIRTIS. The high
albedo of the E-type asteroid is confirmed. The spectrum of Steins was
observed using a complement of 23 OSIRIS filters from 245 to 1000 nm
and VIRTIS spectra. The spectrum is in good agreement with published
telescopic spectra in the visible and shows a strong drop off in the
UV below 400 nm. <P />Images around CA show the asteroid surface on a
scale of 80 m per pixel. The dimensions of Steins are 4.0 km along its
spin axis and 5.9 km in the perpendicular direction. A shape model will
be presented. The appearance of the body is dominated by a large crater
(diameter 2 km) at the northern pole. From there a chain of 7 craters
(catenae) extends across the surface visible during the fly-by. More
than 20 craters with diameters > 0.2 km can be counted. First results
of a photometric model based on detailed topography are expected.
---------------------------------------------------------
Title: Rosetta Fly-by of Asteroid 2867 Steins: Phase Function from
the OSIRIS Imaging System
Authors: Hviid, Stubbe; Fornasier, S.; Vernazza, P.; Sierks, H.;
Keller, U.; Sabolo, W.; Kueppers, M.; Ferri, F.; Da Deppo, V.;
Barbieri, C.; Lamy, P.; Jorda, L.; Groussin, O.; Koschny, D.;
OSIRIS Team
2009DPS....40.2834H Altcode: 2009BAAS...41..558H
The ESA Rosetta mission performed a fly-by of the E-type asteroid Steins
on September 5, 2008. The geometry of the fly-by was optimized to reach
the zero phase angle aspect a couple of minutes before the closest
approach. A fast monitoring sequence was implemented to investigate the
phase function of the asteroid in the narrowband OI filter, centered
at 630 nm, with the Wide Angle Camera of the OSIRIS imaging system. A
set of 21 images of 30 ms exposure time were acquired for monitoring
the opposition surge in the phase angle range from 0 to 11 degrees with
a step of 0.5-1 degrees. In addition, several OI images were taken in
the spectrophotometric sequences allowing us to reach a phase function
coverage up to 140 degrees. In this work we present the Steins phase
function and its interpretation. The derived values of the albedo,
of the linear slope, and of the Hapke G parameter match those of E
class asteroids.
---------------------------------------------------------
Title: Shape, Rotational Properties and Phase Function of Asteroid
2867 Steins
Authors: Lamy, Philippe L.; Kaasalainen, M.; Jorda, L.; Gutierrez,
P.; Faury, G.; Sabolo, W.; OSIRIS Team
2009DPS....40.2833L Altcode: 2009BAAS...41..558L
The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS
observed the E-type asteroid (2867) Steins during the fly-by of ESA's
Rosetta spacecraft. Before the flyby, the OSIRIS camera obtained
two light curves on 20 August and 4 September 2008. Combined with
previously published OSIRIS and ground-based observations, we will
present a refined global shape model of the asteroid, the rotational
parameters and the phase function (at large phase angles).
---------------------------------------------------------
Title: Spitzer Space Telescope observations of the nucleus of comet
67P/Churyumov-Gerasimenko
Authors: Lamy, P. L.; Toth, I.; Groussin, O.; Jorda, L.; Kelley,
M. S.; Stansberry, J. A.
2008A&A...489..777L Altcode:
Context: Comet 67P/Churyumov-Gerasimenko is the target of the Rosetta
mission, and an early characterization of its nucleus is required
to assist in preparing the orbital strategy of the spacecraft, the
delivery of the Philae surface module and the science operations. We
detected the nucleus using the Hubble Space Telescope in March 2003,
but had to assume an albedo to derive its size from its observed
magnitudes. <BR />Aims: It is important to derive an additional
constraint for independently determining both the comet size and
albedo. <BR />Methods: We implemented the well-known “radiometric
method”, which combines visible and infrared photometry. Sixteen
thermal images of 67P/C-G were obtained by the Multiband Imaging
Photometer (MIPS) 24 μm channel of the Spitzer Space Telescope (SST)
on 25 February 2004: the observations spanned a time interval of ~12.5
h, which sampled the rotational light curve of its nucleus. The comet
was then outbound at a heliocentric distance of 4.48 AU, at a distance
of 4.04 AU from SST, and at a solar phase angle of 12.1°. The nucleus
conspicuously appeared as a bright point source superimposed on a dust
trail; it was necessary to apply the point-spread function fitting
technique using an adequate model of the trail to correctly determine
the thermal flux from the nucleus. The data were analyzed using a
standard thermal model that incorporated the thermal inertia. <BR
/>Results: Our preferred solution with a low thermal inertia has overall
dimensions measured along the principal axis of 4.40-5.20 km, 4.16-4.30
km, and 3.40-3.50 km, corresponding to an effective radius of a sphere
with the same volume in the range of 1.93-2.03 km. Larger values of
thermal inertia produce larger sizes but the effective radius cannot
exceed ~2.3 km. The albedo is in the range 0.039-0.043, remarkably
consistent with the canonical value of 0.04 for cometary nuclei. The
success of the landing of the Philae surface module remains critically
dependent upon the bulk density of the nucleus: it would be safe if
close to 0.35 g cm<SUP>-3</SUP>, but a larger value, for instance 0.5
g cm<SUP>-3</SUP>, would present some risks. <P />Based on observations
made with the NASA Spitzer Space Telescope.
---------------------------------------------------------
Title: The Rosetta Asteroid Steins Flyby Observed by OSIRIS
Authors: Keller, Horst Uwe; Barbieri, C.; Koschny, D.; Lamy, P.;
Rickman, H.; Rodrigo, R.; OSIRIS Team
2008DPS....40.2831K Altcode: 2008BAAS...40..442K
The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS
was already used to observe the light curve of the E-type asteroid
(2867) Steins in preparation of the ESA Rosetta flyby (Küppers et
al. A&A 2007). During the approach observations of the light curve
will be repeated to improve the knowledge about the rotational status,
coarse shape, and phase of Steins. The closest approach (CA) campaign
will start 2 hours before CA when the spacecraft is still 60000 km
away from the asteroid. Changes of the reflectivity while passing
through zero phase angle shortly before CA will be recorded taking
images as fast as possible. The wide angle camera (WAC) will be used
to search for satellites. Boulders as small as 10 cm in diameter can
be detected in the large field of view. The narrow angle camera (NAC)
will concentrate to observe the properties of Steins determining its
shape and surface morphology. Near CA at a distance of 800 km images
of Steins will cover about 330 pixel in diameter out of the 2k by 2k
pixel CCD. We will report on the topography and geomorphology based
on a derived digital terrain model. Photometric properties and phase
angle variations will be determined over taking advantage of the
varying observation geometry. Both cameras will use a complement of
23 filters between 245 to 1000 nm.
---------------------------------------------------------
Title: Asteroid 2867 Steins. I. Photometric properties from
OSIRIS/Rosetta and ground-based visible observations
Authors: Jorda, L.; Lamy, P. L.; Faury, G.; Weissman, P.; Barucci,
M. A.; Fornasier, S.; Lowry, S.; Toth, I.; Küppers, M.
2008A&A...487.1171J Altcode:
Context: Asteroid 2867 Steins is the first target of the Rosetta space
mission with a flyby scheduled in September 2008. <BR />Aims: An early
characterization is needed to optimize the flyby parameters and the
science operations and to maximize the scientific return. The aim of
this article is to characterize the photometric properties of this
asteroid. <BR />Methods: The asteroid was imaged with the Narrow Angle
Camera (NAC) of the Optical, Spectroscopic, and Infrared Remote Imaging
System (OSIRIS) during the cruise phase of the Rosetta spacecraft,
at a phase angle of 41.7° significantly larger than achievable from
Earth. It was continuously monitored over ~24 h (on 11 March 2006), thus
covering four rotational periods, at a temporal cadence of 6 min. An
accurate photometric calibration was obtained from the observations of
a solar analog star, 16 Cyg B. <BR />Results: The light curve in the R
photometric band of the Johnson-Kron-Cousins system has a mean value
R(1,1,α = 41.7° = 14.13 ± 0.03 and an amplitude of 0.25 ± 0.04
mag. The periodicity was analyzed with different techniques yielding a
mean value of the synodic rotational period of 6.054 ± 0.003 h. By
combining with ground-based observations obtained at different phase
angles, the phase function is constructed and characterized by a
linear part having a phase coefficient β = 0.025 ± 0.001 mag/deg and
a mean value R(1,1,0) = 13.10 ± 0.04. In terms of the H-G formalism,
the best fit photometric values are G = 0.35 ± 0.05 and H = 12.84 ±
0.07, but the resulting opposition surge of 0.25 mag, although typical
of E-type asteroids, is not really constrained because of the lack of
data at phase angles below 7°. Altogether the photometric properties
of asteroid 2867 Steins (phase function, color and albedo) indicate
that it is a somewhat extreme E-type object, although it is known that
this quite small population exhibits at least three different surface
mineralogies. <P />Table [see full textsee full text] is only available
in electronic form at http://www.aanda.org
---------------------------------------------------------
Title: Asteroid 2867 Steins. III. Spitzer Space Telescope
observations, size determination, and thermal properties
Authors: Lamy, P. L.; Jorda, L.; Fornasier, S.; Groussin, O.; Barucci,
M. A.; Carvano, J.; Dotto, E.; Fulchignoni, M.; Toth, I.
2008A&A...487.1187L Altcode:
Context: Asteroid 2867 Steins is the first target of the Rosetta
space mission with a flyby scheduled in September 2008. <BR />Aims:
An early characterization is needed to optimize the flyby parameters
and the science operations, and to maximize the scientific return. <BR
/>Methods: We used the infrared spectrograph (IRS) of the Spitzer Space
Telescope (SST) to obtain 14 spectra ranging from 5.2 to 38.0 μm, and
to sample the rotational period of the asteroid. The observations were
performed on 22 November 2005, when the asteroid was 2.13 AU from the
Sun, 1.60 AU from the SST, and at a phase angle of 27.2°. They were
interpreted using a standard thermal model incorporating the thermal
inertia. <BR />Results: The solution for a spherical shape leads to an
effective radius r<SUB>n</SUB> = 2.46 ± 0.20 km and a thermal inertia
I = 150 ± 60 J K<SUP>-1</SUP> m<SUP>-2</SUP> s<SUP>-1/2</SUP>, for
a beaming factor between 0.8 and 1.0. The geometric albedo is then
constrained by visible photometry to p<SUB>R</SUB> = 0.31 ± 0.05 and
p<SUB>V</SUB> = 0.27 ± 0.04 when using a linear phase function. The
H-G phase law, which includes an opposition effect, leads to larger
values of the albedo, p_R(H-G) = 0.40 ± 0.07 and p_V(H-G) = 0.34
± 0.06. The solution for our 3-dimensional shape model has overall
dimensions of 5.73 ± 0.52 × 4.95 ± 0.45 × 4.58 ± 0.41 km.
---------------------------------------------------------
Title: Hubble Space Telescope Observations of Fragment C of the
Split Comet 73p/schwassmann-wachmann 3 in 2001 and 2006
Authors: Toth, Imre; Lamy, P. L.; Weaver, H. A.; Noll, K. S.; Mutchler,
M. J.
2008DPS....40.0508T Altcode: 2008BAAS...40..394T
We unambiguously detected fragment C of the split comet
73P/Schwassmann-Wachmann 3 on 26 November 2001 with the PC2 and on 10
April 2006 with the HRC of the ACS of the HST. On 26 November 2001
it was at heliocentric and geocentric distances respectively 3.26
AU and 2.34 AU and despite of its large heliocentric distance it was
highly active and from images obtained during two consecutive orbits
we determined an effective radius of 0.68±0.04 km assuming a spherical
shape and standard values for the geometric albedo (0.04) and the phase
function (0.04 mag/deg) (Icarus 178, 235-247, 2005). We re-observed
fragment C in 2006, taking advantage of the exceptional close encounter
of the comet with Earth. The heliocentric and geocentric distances
were respectively 1.24 AU and 0.29 AU. Six HST orbits spread over 21
hrs allowed us to obtain multi-color images (BVR) but only a poorly
sampled light curve. We determined a possible synodic rotational period
in the range 3.5-4 hr. The mean magnitude of the light curve leads to an
effective radius of 0.53±0.02 km for the fragment C (assuming the same
standard values for the albedo and phase function) and its amplitude,
to a minimum axial ratio of 1.8±0.3. Our deep exposures did not reveal
any subfragment in the vicinity of the main C fragment. We will discuss
possible scenarios to explain the decrease of the size of the C fragment
which apparently took place between 2001 and 2006. Moreover, we will
discuss a scenario to explain the increase of the rotational period of
the C fragment which apparently took place between our HST observations
and the radar observations (BAAS 38, abstr. 12.06, p. 504, 2006) about
one month later. H,A,W. acknowledges supports by NASA through grant
GO/10625 from the STScI, I.T. acknowledges support from CNES, France.
---------------------------------------------------------
Title: Photometry of the Kreutz Comets 1996-2005
Authors: Knight, Matthew M.; A'Hearn, M. F.; Biesecker, D. A.; Faury,
G.; Hamilton, D. P.; Lamy, P.; Llebaria, A.
2008DPS....40.1601K Altcode: 2008BAAS...40Q.411K
We present the results of our photometric study of the Kreutz group
of sungrazing comets observed by SOHO-LASCO from 1996-2005. We extend
the work of Biesecker et al. (2002), expanding the sample from 141
to more than 900 comets. The Kreutz comets seen by SOHO are produced
by fragmentation from the more massive members of the family which
include Ikeya-Seki (C/1965 S1 = 1965f) and C/1882 R1. None of the SOHO
observed Kreutz comets have survived perihelion due to both their small
size (we infer sizes less than 50 meters in radius) and perihelion
distances below 2 solar radii. <P />Kreutz comets typically brighten
at a rate near r<SUP>-7.3</SUP> when first entering the SOHO field of
view (at distances near 30 solar radii), then rapidly transition to
brightening at a rate near r<SUP>-3.8</SUP> from 16-24 solar radii. We
find that they do not have a bimodal distance of peak brightness
as previously reported by Biesecker et al. (2002), but instead
peak between 10-14 solar radii, suggesting there is a continuum,
perhaps due to compositional variations, rather than two distinct
subpopulations. Inside of 10 solar radii but prior to perihelion, the
comets fade rapidly and disappear by 6 solar radii. <P />We derive
nuclear sizes of up to 50 meters in radius, with a cumulative size
distribution of N(>R) R<SUP>-2.2</SUP> for comets larger than 5
meters in radius. This size distribution cannot explain the six largest
members of the family seen from the ground, suggesting that either the
family is not collisionally evolved or that the distribution is not
uniform around the orbit. The total mass of the distribution up to the
largest expected size ( 500 meters) is 4x10<SUP>14</SUP> g, much less
than the estimated mass of the largest ground observed members. <P
/>This research was supported by NASA Planetary Atmospheres grants
NAG513295 and NNG06GF29G.
---------------------------------------------------------
Title: Spitzer Space Telescope Observations of the Nucleus of Comet
8P/Tuttle
Authors: Groussin, Olivier; Kelley, M.; Lamy, P.; Toth, I.; Fernandez,
Y.; Jorda, L.; Weaver, H.
2008DPS....40.0503G Altcode: 2008BAAS...40..393G
We observed comet 8P/Tuttle, a nearly isotropic comet (NIC), with the
IRS and MIPS instruments of the Spitzer Space Telescope (SST). The
IRS observations were performed on 2 November 2007 when the comet
was at 1.32 AU from SST, 1.61 AU from the Sun, and nearly 3 months
before perihelion on 27 January 2008 when its heliocentric distance
was 1 AU. We used IRS in low-resolution mode to obtain the spectral
energy distribution (SED) from 5 to 35 micron. The MIPS observations
were performed on 22 June 2008 when the comet was at 1.58 AU from SST
and 2.24 AU from the Sun. We sampled a period of 15 hours with 20 MIPS
images at 24 µm, and also acquired 4 MIPS images at 70 µm to better
constrain the SED. From these IRS and MIPS observations, we derived
the size and thermal inertia of the nucleus of comet 8P/Tuttle. The
(010-000) vibrational emission band of water at 6.3 microns was also
detected, and we derived the water production rate and active surface
fraction.
---------------------------------------------------------
Title: Asteroid 2867 Steins. II. Multi-telescope visible observations,
shape reconstruction, and rotational state
Authors: Lamy, P. L.; Kaasalainen, M.; Lowry, S.; Weissman, P.;
Barucci, M. A.; Carvano, J.; Choi, Y. -J.; Colas, F.; Faury, G.;
Fornasier, S.; Groussin, O.; Hicks, M. D.; Jorda, L.; Kryszczynska,
A.; Larson, S.; Toth, I.; Warner, B.
2008A&A...487.1179L Altcode:
Context: Asteroid 2867 Steins is the first target of the Rosetta space
mission with a flyby scheduled in September 2008. <BR />Aims: An early
physical characterization is needed to optimize the flyby parameters
and the science operations, and to maximize the scientific return. The
aim of this article is to characterize the shape and rotational state
of this asteroid. <BR />Methods: We compile a set of 26 visible light
curves whose phase angle coverage extends from 7.5° to 41.7°, and
perform their simultaneous inversion relying on convex modeling. <BR
/>Results: The full three-dimensional solution for asteroid 2867
Steins is rather spherical with axial ratios a/b=1.17 and a/c=1.25. The
rotational state is characterized by a sidereal period of 6.04681 ±
0.00002 h, and the pole direction defined by its ecliptic coordinates
λ ≈ 250° and β ≈ - 89° has an uncertainty of about 5°. It is
therefore almost exactly perpendicular to the ecliptic plane, and the
viewing geometries are thus restricted to only ±20° about Steins'
equator. Consequently, the shape model is not strongly constrained,
and the polar flattening has an uncertainty of about 10%. Inversion is
basically scale-free, and absolute scaling comes from a measurement
of its thermal emission with the Spitzer Space Telescope (Lamy et
al. 2008, A&A, 487, 1187), yielding overall dimensions of 5.73 ±
0.52, 4.95±0.45, and 4.58 ± 0.41 km.
---------------------------------------------------------
Title: Hubble Space Telescope Observations of the Nucleus of Comet
8P/Tuttle
Authors: Lamy, Philippe L.; Toth, I.; Jorda, L.; Weaver, H. A.;
Groussin, O.; A'Hearn, M. F.
2008DPS....40.0502L Altcode: 2008BAAS...40..393L
We unambiguously detected the nucleus of comet 8P/Tuttle, a
nearly-isotropic comet (NIC) in a 13.5 yr orbital period, during its
recent close (0.25 AU) Earth encounter with the Planetary Camera 2 of
the Hubble Space Telescope (HST). <P />The observations were performed
from December 10.0 to 11.2, 2007, and consisted in 12 visits extending
over a 28-hour period. At the mid-point of the observing window, the
comet was 1.25 AU from the Sun , 0.48 AU from the Earth and at a phase
angle of 46.6 deg. During each visit corresponding to an HST orbit,
typically twelve images were obtained through five broadband filters
(UBVRI). The light curve exhibits a complex shape best modeled by
a bilobate body as evidenced by the radar observations of Harmon
et al. (2008). We determined a synodic rotational period of 11.4
hr. Assuming the same albedo of 0.04 for the two lobes, we found
respective radii of 1.2 km and 2.8 km. During the HST observations,
the nucleus was at an aspect angle (between spin axis and line of sight)
of 65 deg.
---------------------------------------------------------
Title: 3-Dimensional Reconstruction of the ROSETTA Targets -
Application to Asteroid 2867 Steins
Authors: Besse, Sebastien; Groussin, O.; Jorda, L.; Lamy, P.;
OSIRIS Team
2008DPS....40.2830B Altcode: 2008BAAS...40..442B
The OSIRIS imaging experiment aboard the Rosetta spacecraft will
image asteroids Steins in September 2008 and Lutetia in 2010, and
comet 67P/Churyumov-Gerasimenko in 2014. An accurate determination
of the shape is a key point for the success of the mission operations
and scientific objectives. Based on the experience of previous space
missions (Deep Impact, Near, Galileo, Hayabusa), we are developing
our own procedure for the shape reconstruction of small bodies. We use
two different techniques : i) limb and terminator constraints and ii)
ground control points (GCP) constraints. The first method allows the
determination of a rough shape of the body when it is poorly resolved
and no features are visible on the surface, while the second method
provides an accurate shape model using high resolution images. We
are currently testing both methods on simulated data, using and
developing different algorithms for limb and terminator extraction
(e.g.,wavelet), detection of points of interest (Harris, Susan,
Fast Corner Detection), points pairing using correlation techniques
(geometric model) and 3-dimensional reconstruction using line-of-sight
information (photogrammetry). Both methods will be fully automated. We
will hopefully present the 3D reconstruction of the Steins asteroid
from images obtained during its flyby. <P />Acknowledgment: Sébastien
Besse acknowledges CNES and Thales for funding.
---------------------------------------------------------
Title: In-orbit calibration of the polarization flat fields of the
SOHO-LASCO coronagraphs
Authors: Llebaria, A.; Lamy, P.
2008SPIE.7010E..1IL Altcode: 2008SPIE.7010E..46L
Since 11 years SOHO-LASCO coronagraphs are producing a unique set of
the Sun corona images in the 2-32 solar radius range. For the first
time a complete set of coronal calibrated images in WL (polarized and
unpolarized) for the full solar cycle is available. The telescopes are
equipped with 3 polarizers at -60,0 and 60 degrees, one all pass channel
and a set filters. Ground calibrations were completed with in orbit
calibrations. To control the evolution of sensivity for each bandpass
and for each polarizer, the LASCO-C2 and LASCO-C3 coronographs were
provided with an internal system of calibration in orbit. The measures
obtained in 1996 and 2003 have been used to determine the CCD flat field
for each filter bandpass, the gain constant (ADU to phe<SUP>-</SUP>
conversion) and the polarizers transmittance map. The solar corona
itself was also used to control the local response. Spacecraft rotations
by 45 and 90 complete the test, and allowed for a ultimate but relevant
global correction of the polarized images.
---------------------------------------------------------
Title: In-flight validation of the formation flying technologies
using the ASPIICS/PROBA-3 giant coronagraph
Authors: Vivès, S.; Lamy, P.; Levacher, P.; Venet, M.; Boit, J. L.
2008SPIE.7010E..3RV Altcode: 2008SPIE.7010E.109V
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. Formation flyers open new perspectives and allow
conceiving giant, externally-occulted coronagraphs using two-spacecraft
system. The PROBA-3 formation flying demonstration mission, currently
in its preparatory study phase, is intended to incorporate the ASPIICS
(Association de Satellites Pour l'Imagerie et l'Interfromtrie de la
Couronne Solaire) scientific payload. ASPIICS is a solar coronagraph
designed to observe from the coronal base out to 3 solar radii with high
spatial resolution in the visible range. Formation flying technique
imposes new constraints and major challenges in particular in terms
of metrology. ASPIICS will both use and demonstrate the formation
flying features and performances. In order to fully validate the
formation flying technique and to improve the scientific return,
original developments linked to the formation flying constraints have
been made these last years and are presented in this article.
---------------------------------------------------------
Title: The coronal dynamics imagers for the KuaFu mission
Authors: Vives, S.; Lamy, P.; Rousset, G.; Boit, J. L.
2008AdSpR..42..106V Altcode:
The Space Weather Explorer - KuaFu mission will provide simultaneous,
long-term, and synoptic observations of the complete chain of
disturbances from the solar atmosphere to the geospace. KuaFu-A
(located at the L1 liberation point) includes Coronal Dynamics Imagers
composed of a Lyman-α coronagraph (from 1.15 to 2.7 solar radii)
and a white light coronagraph (out to 15 solar radii), in order to
identify the initial sources of Coronal Mass Ejections (CMEs) and
their acceleration profiles. The difficulty of observing the lower
corona should not be underestimated since instrumental stray light
remains a critical issue in the visible because of the low contrast
of the corona with respect to the Sun. Observing the corona in the
Lyman-α line is a valid alternative to white light observations. This
approach takes advantage of both the intrinsic higher contrast of
the corona with respect to the solar disk in this line compared to
the visible, and the absence of F-corona at 121.6 nm. Furthermore,
it has been convincingly shown that the coronal structures seen in
Lyman-α correspond to those seen in the visible and which result from
Thomson scattering of the coronal ionized gas. This is because the
plasma is still collisional in the lower corona so that the hydrogen
neutral atoms are coupled to the protons. A classical, all-reflecting
internally-occulted Lyot coronagraph is required so as to preserve the
image quality down to the inner limit of the field-of-view. A narrow
band interference filter located in a collimated beam allows isolating
the Lyman-α line. The visible coronagraph will adopt the approach of a
single instrument having a large field-of-view extending from 2.5 to 15
solar radii. Such a design is based on refractive externally-occulted
coronagraphs built for recent past missions, essentially the LASCO-C2
and C3 instruments and the SECCHI/COR 2 of the STEREO mission, which
is itself a combination of the C2 and C3 instruments.
---------------------------------------------------------
Title: Comet 144P/KUSHIDA
Authors: Kelley, M. S.; Fernandez, Y.; Weaver, H.; Toth, I.; Reach,
W.; Pittichova, J.; Meech, K.; Lowry, S.; Lisse, C.; Licandro, J.;
Lamy, P.; Groussin, O.; Fitzsimmons, A.; Campins, H.; Bauer, J.;
A'Hearn, M.; Marsden, B. G.
2008MPEC....N...20K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comet Observations [245 Spitzer Space Telescope]
Authors: Kelley, M. S.; Fernandez, Y.; Weaver, H.; Toth, I.; Reach, W.;
Pittichova, J.; Meech, K.; Lowry, S.; Lisse, C.; Licandro, J.; Lamy,
P.; Groussin, O.; Fitzsimmons, A.; Campins, H.; Bauer, J.; A'Hearn, M.
2008MPC..63320..13K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: New perspectives in solar coronagraphy offered by formation
flying: from PROBA-3 to Cosmic Vision
Authors: Lamy, P.; Vivès, S.; Damé, L.; Koutchmy, S.
2008SPIE.7010E..1HL Altcode:
Formation flying opens new perspectives in solar physics, and allow to
conceive giant, externally-occulted coronagraphs using a two-component
space system with the external occulter on one spacecraft and the
optical instrument on the other spacecraft at a distance of hundred
meters. Conditions close to those of a solar total eclipse can then be
achieved offering the capability of imaging the solar corona down to the
limb at very high spatial resolution. ASPIICS (Association de Satellites
Pour l'Imagerie et l'Interférométrie de la Couronne Solaire) is a
mission proposed to ESA in the framework of its PROBA-3 demonstration
program of formation flying which is presently in phase A. ASPIICS is
a single coronagraph which will perform both high spatial resolution
imaging of the solar corona as well as 2-dimensional spectroscopy of
several emission lines from the coronal base out to 3 R\beye using
a Fabry-Pérot étalon interferometer. The classical design of an
externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as
close as 0.01 R\beye from the solar limb. Super-ASPIICS is an even
more ambitious instrument part of the scientific payload of HiRise,
the High Resolution Imaging and Spectroscopy Explorer proposed to
ESA in the framework of its Cosmic Vision program. With an increased
inter-satellite distance of 280 m, an aperture of 300 mm, a spectral
domain extending from the ultraviolet to the near-infrared, and
spectroscopic capabilities, Super-ASPIICS will offer unprecedented
diagnostic capabilities, including the measurement of coronal magnetic
fields.
---------------------------------------------------------
Title: The Origin of Polar Streamers in the Solar Corona
Authors: Zhukov, A. N.; Saez, F.; Lamy, P.; Llebaria, A.; Stenborg, G.
2008ApJ...680.1532Z Altcode:
We investigate the large-scale three-dimensional (3D) structure of the
solar corona near the maximum of the 23rd solar cycle in an attempt to
determine the origin of polar streamers. We use a model that allows
us to simulate the quasi-stationary configuration of the large-scale
coronal density distribution. The coronal neutral line, as given by
the potential field source surface (PFSS) model, serves as a proxy for
mid- and low-latitude current sheets. We investigate the contribution
of possible polar coronal current sheets associated with large-scale
photospheric magnetic neutral lines around the poles of the Sun (polar
crown neutral lines). Positions of polar neutral lines are radially
extrapolated outward to obtain the configuration of polar current
sheets. Coronal plasma sheets are centered around introduced current
sheets. Streamer positions during Carrington rotation 1965, near the
activity maximum, are calculated. Simulated synoptic maps of the coronal
brightness are compared with those obtained from observations by the
LASCO C2 coronagraph on board the SOHO spacecraft. We demonstrate that
polar streamers are "classical" streamers situated above low-lying loops
(observed by SOHO EIT) connecting the regions of opposite magnetic
polarity on two sides of polar crown neutral lines. Polar streamer
configurations obtained from our model are close to those observed
by LASCO. Our results suggest that the PFSS model cannot adequately
describe the configuration of streamers during the epoch of high solar
activity. The representation of the streamer belt as a single tilted
and warped current sheet becomes questionable. Multiple coronal current
sheets may better correspond to the observed streamer configurations.
---------------------------------------------------------
Title: Results From SEPPCoN, a Survey to Study the Physical Properties
of the Nuclei and Dust of Jupiter-Family Comets
Authors: Fernandez, Y.; Kelley, M.; Lamy, P.; Reach, W.; Toth,
I.; Groussin, O.; Lisse, C.; A'Hearn, M.; Bauer, J.; Campins, H.;
Fitzsimmons, A.; Licandro, J.; Lowry, S.; Meech, K.; Pittichova, J.;
Snodgrass, C.; Weaver, H.
2008AGUSM.P41A..08F Altcode:
We present results from SEPPCoN, our Survey of Ensemble Physical
Properties of Cometary Nuclei. This survey involves studying 100
Jupiter-family comets (JFCs) -- about 30% of the known population
-- at both mid-infrared and visible wavelengths. We have used the
Spitzer Space Telescope to study the comets' thermal emission, and
many ground-based telescopes (Apache Point's ARC 3.5-m; ESO's NTT
3.6-m; MKO's UH 2.2-m and Keck 10-m; Palomar's 5-m and 1.5-m; ORM's
WHT 4.2-m, NOT 2.6-m, and LT 2-m; Cerro Pachon's SOAR 4.1-m) to study
the reflected sunlight. The Spitzer observations (imaging with IRS PU
and MIPS) are complete, and the ground-based observations (imaging
in at least R band) are about half complete. Almost all our targets
are imaged while farther than 4 AU from the Sun, to minimize (and
often eliminate) confusion caused by dust from cometary activity. The
Spitzer data constrain the effective radii of the nuclei; we find
preliminarily that the cumulative size distribution's power-law slope
is similar to what has been found by others using visible wavelength
studies, suggesting that there is no strong trend of albedo with
size. The Spitzer data also tell us about the thermal inertia, and we
find that many -- though not all -- cometary nuclei seem to have low
values of this, consistent with a porous, fluffy, poorly-conducting,
dusty surface layer. The Spitzer images show that about one-third of
our sample appeared with extended dust emission despite being close to
aphelion. We find that often the activity observed at these distances
seems to turn off abruptly once a JFC passes aphelion. We have used
dynamical analysis to constrain the dust grain sizes and thereby
distinguish dust tails from dust trails. The dust temperatures are in
most cases consistent with isothermal, low-albedo grains in LTE. We
thank the Spitzer Science Center and the TACs of the aforementioned
telescopes for supporting this research.
---------------------------------------------------------
Title: A Portrait of Asteroid 2867 Steins from Visible and Infrared
Observations with Ground- and Space-Based Telescopes
Authors: Lamy, P. L.; Barucci, A.; Fornasier, S.; Groussin, O.; Jorda,
L.; Kaasalainen, M.; Lowry, S.; Toth, I.
2008LPICo1405.8163L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar cycle evolution of the magnetic topology of the corona
as deduced from Lasco-C2
Authors: Llebaria, Antoine; Lamy, Philippe; Saez, Fabien
2008cosp...37.1812L Altcode: 2008cosp.meet.1812L
The magnetic topology of the corona is clearly revealed by the
structures in the corona. Its temporal evolution can therefore
be analyzed using synoptic maps of the polarized radiance pB of
the K-corona or the derived electron densities. In January 2008,
the LASCO-C2 coronagraph aboard SOHO has completed 12 years of
quasi-continuous observations of the solar corona from 2 to 6 solar
radii, thus allowing a full view of the evolution of the magnetic
topology over a full solar cycle. From this data set, we have produced
synoptic maps of of unsurpassed spatial and temporal resolutions. The
periodic sampling (2 x 14 days) of this series best shows the global
evolution of the whole corona. The onset of the Sun activity period is
clearly marked by increasing twists of the neutral sheet, shifting the
activity to higher and higher latitudes. The neutral sheet then splits
into two or more oscillating branches branches characterized by long
oscillating periods. Surprisingly this situation prevails until the
end of the present 23rd cycle. Short scale variations have also been
analyzed and will be discussed.
---------------------------------------------------------
Title: Hubble Investigation of the B and G Fragments of Comet
73P/Schwassmann-Wachmann 3
Authors: Weaver, H. A.; Lisse, C. M.; Mutchler, M.; Lamy, P. L.;
Toth, I.; Reach, W. T.; Vaubaillon, J.
2008LPICo1405.8248W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Kuiper Belt Objects in the Planetary Region: The Jupiter-Family
Comets
Authors: Lowry, S.; Fitzsimmons, A.; Lamy, P.; Weissman, P.
2008ssbn.book..397L Altcode:
Jupiter-family comets (JFCs) are a dynamically distinct group with
low orbital inclinations and orbital periods ó20 yr. Their origin
has been shown computationally to be the Kuiper belt region beyond
Neptune. Therefore studying the nuclei of these comets, as well as
their coma species, can provide valuable insights into the nature of
the kilometer-sized Kuiper belt objects (KBOs). These include their
size distribution, internal structure, and composition, as well as some
hints at their likely surface features. Although JFCs are much closer
to the Sun than KBOs, they are still very difficult to observe due to
their intrinsic faintness and outgassing comae. However, observational
studies are advancing rapidly and we are now starting to place valuable
constraints on the bulk physical properties of these nuclei. In this
chapter, we review some of the more important findings in this field
and their relevance to KBO studies.
---------------------------------------------------------
Title: A Portrait of Asteroid 21 Lutetia from Visible and Infrared
Observations with Ground- and Space-Based Telescopes
Authors: Lamy, P. L.; Barucci, A.; Fornassier, S.; Faury, G.; Groussin,
O.; Kaasalainen, M.; Jorda, L.; Mottola, S.; Toth, I.
2008LPICo1405.8245L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Determination of Photometric Properties of Asteroid Steins
Authors: Spjuth, S.; Jorda, L.; Li, J.; Keller, H. U.; Kueppers, M.;
Hviid, S.; Lamy, P.
2008LPICo1405.8082S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Asteroids 2867 Steins and 21 Lutetia: surface composition
from far infrared observations with the Spitzer space telescope
Authors: Barucci, M. A.; Fornasier, S.; Dotto, E.; Lamy, P. L.; Jorda,
L.; Groussin, O.; Brucato, J. R.; Carvano, J.; Alvarez-Candal, A.;
Cruikshank, D.; Fulchignoni, M.
2008A&A...477..665B Altcode:
Aims:The aim of this paper is to investigate the surface composition of
the two asteroids 21 Lutetia and 2867 Steins, targets of the Rosetta
space mission. <BR />Methods: We observed the two asteroids through
their full rotational periods with the Infrared Spectrograph of the
Spitzer Space Telescope to investigate the surface properties. The
analysis of their thermal emission spectra was carried out to
detect emissivity features that diagnose the surface composition. <BR
/>Results: For both asteroids, the Christiansen peak, the Reststrahlen,
and the Transparency features were detected. The thermal emissivity
shows a clear analogy to carbonaceous chondrite meteorites, in
particular to the CO-CV types for 21 Lutetia, while for 2867 Steins,
already suggested as belonging to the E-type asteroids, the similarity
to the enstatite achondrite meteorite is confirmed.
---------------------------------------------------------
Title: Comet Dust and Activity in the SEPPCoN Survey
Authors: Kelley, M. S.; Fernández, Y. R.; A'Hearn, M. F.; Bauer, J.;
Campins, H.; Fitzsimmons, A.; Groussin, O.; Lamy, P. L.; Licandro,
J.; Lisse, C. M.; Lowry, S. C.; Meech, K. J.; Pittichová, J.; Reach,
W. T.; Snodgrass, C.; Toth, I.; Weaver, H. A.
2008LPICo1405.8272K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Coronal electron density over a full solar cycle - Implications
for the solar wind velocity
Authors: Lamy, Philippe
2008cosp...37.1687L Altcode: 2008cosp.meet.1687L
In January 2008, the LASCO-C2 coronagraph aboard SOHO has completed
12 years of quasicontinuous observations of the solar corona from
2 to 6 solar radii, that is over a full solar cycle. We study the
temporal evolution of the electron density derived from the calibrated
pB images over this unsurpassed time span, first globally, and then
by distinguishing different latitude intervals so as to characterize
the the equatorial and polar regions. The local density moderately
increases with activity (factor 2), as the bulk of the increase
essentially results from the development of new sources associated to
emerging neutral or current sheets. We extensively study different
typical structures of the corona, polar and trans-equatorial holes
and the streamer belt to constrain the velocity profiles of different
regimes of solar wind. Finally we combine LASCO-C2 density profiles,
SWAN mass flux data and interplanetary solar wind velocities derived
from ground-based Interplanetary Scintillation Observations (IPS) to
conclude that the fast solar wind reaches its terminal velocity about 6
solar radii, and expands with constant velocity beyond this distance,
while the slow solar wind reaches only half its terminal velocity
value at this distance and thus continues its acceleration further out.
---------------------------------------------------------
Title: Three-dimensional reconstruction of Coronal Mass Ejections
using STEREO/SECCHI-COR2 and SoHO/LASCO-C2 data.
Authors: Boursier, Yannick; Lamy, Philippe; Saez, Fabien; Llebaria,
Antoine
2008cosp...37..361B Altcode: 2008cosp.meet..361B
We present a new method to perform the three-dimensional reconstruction
of CMEs using stereoscopic images obtained with the STEREO/SECCHI-COR2
coronagraph, as well as images from the SoHO/LASCO-C2 and C3
coronagraphs. Our algorithm is based on a forward modeling approach
appropriate to the reconstruction of surfaces in optically thin
medium. It involves four main steps : i) definition of three distinct
geometrical and representative models of CMEs (spherical shell,
fluxrope, cloud-like), ii) generation of a library of simulated images,
iii) local approximation of the observed CME by a sphere shell for a
first estimate of the parameters, iv) determination of the model in
the library that best fits the observed CME . The comparison between
simulated and observed images is based on purely geometrical criteria
and geometric invariants. The algorithm provides two estimates of
the direction of propagation, an estimate of the velocity profile,
and the set of parameters which define the shape and the orientation
of the CME for space weather forecast. Uncertainties on the direction
of propagation are derived from error measurement on the images. We
have applied our algorithm to a set of CMEs observed in 2007, and
when possible, our results are compared with those coming from the
Geometric Localization Method (Pizzo and Biesecker, 2004 ; de Koning,
C. A.; Pizzo, V. J.; Biesecker, D. A., 2007). Finally an identification
of the source regions have been performed.
---------------------------------------------------------
Title: The Size, Thermal Inertia and Water Production Rate of Comet
8P/Tuttle
Authors: Groussin, O.; Kelley, M. S.; Fernández, Y. R.; Jorda, L.;
Lamy, P. L.; Toth, I.; Weaver, H. A.
2008LPICo1405.8035G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Phase Angle Effects on Sungrazing Comets Observed by SOHO
Authors: Knight, M. M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.;
Hamilton, D. P.; Lamy, P.; Llebaria, A.
2008LPICo1405.8143K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Astrophysics, Interferometry, and Coronagraphy at
DomeC/Concordia
Authors: Damé, L.; Amans, J. -P.; Dournaux, J. -L.; Koutchmy, S.;
Lamy, P.; Preumont, A.
2008EAS....33..105D Altcode:
Excellent seeing, coronal conditions, and very low IR thermal
background are qualities of the Dome C/Concordia station site that
will allow unique solar astrophysics science. We review the science
case for inner corona observations (onset of the coronal heating
mechanism still poorly understood) and the promises of high angular
resolution to disentangle the possible mechanisms at work between
waves, convection, and reconnection in this particularly magnetically
structured solar atmosphere between the high chromosphere and inner
corona. For coronagraphy, IR and high resolution possibilities, Dome
C is a case by itself between classical ground-based sites and space
opportunities. Telescopes from 50 cm (coronagraphy oriented) to 4 m
(full high resolution advantage including IR access) are proposed to
benefit from these remarkable observing capabilities. Using 3×O50
cm off-axis telescopes, we first propose a medium size facility
(1.4 m equivalent telescope) for very high resolution access, ADSIIC
(Antarctica Demonstrator of Solar Interferometric Imaging &
Coronagraphy), before the ultimate 9-telescope Solar Facility
equivalent to a 4 m diameter telescope: A-FOURMI (Antarctica 4 m
Interferometer). Finally, 30 m tower designs and their logistics using
standard containers and elementary elements of 6 m maximum length,
are presented and discussed. These towers are indeed of general
interest also for the other optical and IR telescopes intended for
Dome C/Concordia, allowing to get over most of the turbulent ground
layer and to reach the best possible permanent seeing conditions
(better than half an arcsec).
---------------------------------------------------------
Title: Three-dimensional structure of white light polar Plumes at
the beginning and at the end of Solar Cycle 23
Authors: Boursier, Yannick; Llebaria, Antoine; Lamy, Philippe
2008cosp...37..362B Altcode: 2008cosp.meet..362B
In spite of a large set of observations from spatial instruments, the
3D structure of polar plumes remains an open question. Even if the
connection between plumes observed in the EUV and WL seems globally
established, their dynamics and the one-to-one relationship remains
unclear. We first examine and compare high cadence observations obtained
in March 1997 and in March 2006 by the well know method of sinogram,
and find a pronounced similarity. We then implement a forward model,
introducing a fractal distribution of the electron density, and
show that it provides a better agreement to the observations than
classical models such as curtains or columns of plasma, at least from
the geometric and photometric points of view.
---------------------------------------------------------
Title: Results from SEPPCoN, A Survey of Ensemble Physical Properties
of Cometary Nuclei
Authors: Fernández, Y. R.; Kelley, M. S.; Lamy, P. L.; Toth,
I.; Groussin, O.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.;
Fitzsimmons, A.; Licandro, J.; Lisse, C. M.; Lowry, S. C.; Meech,
K. J.; Pittichová, J.; Reach, W. T.; Snodgrass, C.; Weaver, H. A.
2008LPICo1405.8307F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Characterization of the Nucleus Fragment
73P/Schwassmann-Wachmann 3-C from Hubble Space Telescope Observation
in 2001 and 2006
Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; Noll, K. S.
2008LPICo1405.8160L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Commission 21: Light of the Night Sky
Authors: Gustafson, Bo A. S.; Witt, Adolf N.; Lamy, Philippe; Dwek,
Eli; Lamy, Philippe; Henry, Richard C.; Mann, Ingrid
2007IAUTB..26..138G Altcode:
Applications have been received from Dr. Peter Wheatley (proposed by
UK), Prof. Harald Schuh (proposed by Austria), and Dr. Busaba Kramer
(proposed by Thailand). All applications were endorsed, with the caveat
that Dr. Kramer's application needs to be endorsed by at least one
of the other commissions since she has not a publication record in
our field.
---------------------------------------------------------
Title: Recent Evolution of the Kracht Group of Comets
Authors: Knight, Matthew M.; A'Hearn, M. F.; Biesecker, D. A.; Faury,
G.; Hamilton, D. P.; Lamy, P.; Llebaria, A.
2007AAS...211.8504K Altcode: 2007BAAS...39Q.877K
The Kracht group contains 29 comets discovered in SOHO images from
1996-2005 with perihelion distances of 7-11 solar radii and inclinations
of 12-15 degrees. Unlike the much more populous Kreutz sungrazing group,
many Kracht comets are observed to survive perihelion, and as many as
five may have been observed on two apparitions, with periods ranging
from 4.8-5.8 years. Kracht comets tend to arrive in clusters followed
by many months devoid of comets before another cluster arrives. Ohtsuka
et al. (2003) and Sekanina and Chodas (2005) have shown that the Kracht
group represents an evolutionary stage of the Machholz complex, which
has evolved over many centuries and also includes 96P/Machholz 1,
the Marsden group of comets, the Daytime Arietids, and the Southern
delta Aquarids. <P />Here we explain the recent evolution of individual
members of the Kracht group as a series of cascading fragmentations
of a few large comets (causing the temporal clusters) which have
had somewhat different orbital histories since splitting from each
other within the last hundred years or so (causing the gaps between
temporal clusters). We use dynamical simulations to search for possible
fragmentation scenarios and to estimate the rate at which the orbital
elements evolve due to the gravitational influence of the planets. We
predict that 8 of the 19 fragments seen since 2002 may be observable
in upcoming perihelion passages, including five that should reappear
before the end of 2008. If observed, two of these will have been seen
at three perihelion passages, allowing a rough estimation of the mass
loss due to erosion. <P />This research was supported by NASA Planetary
Atmospheres grant NNG06GF29G.
---------------------------------------------------------
Title: Results From SEPPCoN, a Survey to Study the Physical Properties
of the Nuclei and Dust of Jupiter-Family Comets
Authors: Fernandez, Yanga R.; Kelley, M. S.; Lamy, P. L.; Reach,
W. T.; Toth, I.; Groussin, O.; Lisse, C. M.; A'Hearn, M. F.; Bauer,
J. M.; Campins, H.; Fitzsimmons, A.; Licandro, J.; Lowry, S. C.;
Meech, K. J.; Pittichova, J.; Weaver, H. A.
2007AAS...211.5602F Altcode: 2007BAAS...39..827F
We present results from SEPPCoN, our Survey of Ensemble Physical
Properties of Cometary Nuclei. This survey involves studying 100
Jupiter-family comets (JFCs) -- about 30% of the known population --
using the Spitzer Space Telescope for mid-infrared measurements
of thermal emission and several ground-based telescopes for
visible-wavelength measurements of reflected sunlight. The Spitzer
observations (imaging with IRS PU and MIPS) are complete, and the
ground-based observations (imaging in at least R band) are about half
complete. Almost all our targets are imaged while farther than 4 AU
from the Sun, to minimize (and often eliminate) confusion caused by
dust from cometary activity. The Spitzer data constrain the effective
radii of the JFC nuclei and thus give us an independent measurement
of the cumulative size distribution (CSD). We find preliminarily that
the CSD power-law slope is similar to what has been found by others
using visible wavelength studies, suggesting that there is no strong
trend of albedo with size. The Spitzer data also tell us about the JFC
thermal inertia, and we find that many -- though not all -- cometary
nuclei seem to have low values of this, consistent with a porous,
fluffy, poorly-conducting, dusty surface layer. To our surprise,
the Spitzer images show that about one-third of our sample appeared
with extended dust emission despite being close to aphelion, and
in many cases the dust originated from cometary activity happening
right then. Interestingly, we find that the activity observed at
these distances seems to turn off rather abruptly once a JFC passes
aphelion. We have used dynamical analysis to constrain the dust grain
sizes and thereby distinguish dust tails from dust trails. The dust
temperatures are in most cases consistent with isothermal, low-albedo
grains in LTE. We thank the Spitzer Science Center for supporting
this research.
---------------------------------------------------------
Title: Velocity Profiles in the Solar Corona from Multi-Instrument
Observations
Authors: Quémerais, E.; Lallement, R.; Koutroumpa, D.; Lamy, P.
2007ApJ...667.1229Q Altcode: 2007arXiv0706.1913Q
We present a method to derive outflow velocities in the solar corona
using different data sets, including solar wind mass flux coming from
the SWAN SOHO instrument, electron density values from LASCO-C2,
and interplanetary solar wind velocities derived from ground-based
interplanetary scintillation observations (IPS). In a first step, we
combine the LASCO electron densities at 6 R<SUB>solar</SUB> and the IPS
velocities and compare the product to the SWAN mass fluxes. It is found
that this product represents the actual mass flux at 6 R<SUB>solar</SUB>
for the fast wind, but not for the slow wind. In regions dominated
by the slow wind, the fluxes derived from SWAN are systematically
smaller. This is interpreted as proof that the fast solar wind has
reached its terminal velocity at ~6 R<SUB>solar</SUB> and expands with
constant velocity beyond this distance. On the contrary, the slow solar
wind has reached only half of its terminal value and is thus accelerated
farther out. In a second step, we combine the LASCO-C2 density profiles
and the SWAN flux data to derive velocity profiles in the corona between
2.5 and 6 R<SUB>solar</SUB>. Such profiles can be used to test models
of the acceleration mechanism of the fast solar wind.
---------------------------------------------------------
Title: Recent Evolution of the Kracht Group of Comets
Authors: Knight, Matthew M.; A'Hearn, M. F.; Biesecker, D. A.; Faury,
G.; Hamilton, D. P.; Lamy, P.; Llebaria, A.
2007DPS....39.5903K Altcode: 2007BAAS...39..534K
The Kracht group contains 29 comets discovered in SOHO images from
1996-2005 with perihelion distances of 7-11 solar radii and inclinations
of 12-15 degrees. Unlike the much more populous Kreutz sungrazing group,
many Kracht comets are observed to survive perihelion, and as many as
five may have been observed on two apparitions, with periods ranging
from 4.8-5.8 years. Kracht comets tend to arrive in clusters followed by
many months devoid of comets before another cluster arrives. Ohtsuka
et al. (2003) and Sekanina and Chodas (2005) have shown that the
Kracht group represents an evolutionary stage of the Machholz complex,
which has evolved over many centuries and also includes 96P/Machholz,
the Marsden group of comets, and the Arietids. <P />Here we explain
the recent evolution of individual members of the Kracht group as a
series of cascading fragmentations of a few large comets (causing
the temporal clusters) which have had somewhat different orbital
histories since splitting from each other within the last hundred
years or so (causing the gaps between temporal clusters). We use
dynamical simulations to search for possible fragmentation scenarios
and to estimate the rate at which the orbital elements evolve due to
the gravitational influence of the planets. We predict that 8 of the
19 fragments seen since 2002 may be observable in upcoming perihelion
passages, including five that should reappear before the end of 2008. If
observed, two of these will have been seen at three perihelion passages,
allowing a rough estimation of the mass loss due to erosion. <P />This
research was supported by NASA Planetary Atmospheres grant NNG06GF29G.
---------------------------------------------------------
Title: SEPPCoN: Comet Dust and Activity at Moderate Heliocentric
Distances as Observed with Spitzer
Authors: Kelley, Michael S.; Fernández, Y. R.; Reach, W. T.; Lisse,
C. M.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.; Fitzsimmons, A.;
Groussin, O.; Lamy, P. L.; Licandro, J.; Lowry, S. C.; Meech, K. J.;
Pittichova, J.; Toth, I.; Weaver, H. A.
2007DPS....39.5407K Altcode: 2007BAAS...39..525K
A Survey of Ensemble Physical Properties of Cometary Nuclei (SEPPCoN)
is underway to characterize the nuclei of 100 Jupiter-family comets
(JFC). The survey combines both visible and mid-infrared observations
to measure the JFC size and albedo distributions. We inspected Spitzer
Space Telescope MIPS and IRS images of the survey targets for dust
comae, tails, and trails. Out of 98 observed comets, we found 32 to
have some emission from dust outside of the central point source. A
few of these sources were also observed to have dust in visible,
ground-based data. The heliocentric distances (rh) of the 32 targets
range from 3.5 to 6.5 AU, with most between 4 and 5 AU. We derive
color-temperatures for the 20 dust detections observed in both the 16
and 22 micron IRS cameras and find the color-temperature approximately
varies as 280*rh^(-0.5) [K], as expected for isothermal low-albedo
dust in local thermodynamic equilibrium. We discuss the evidence for
outliers from this trend. We compare our observations to dust syndynes
and 3-dimensional dust models to distinguish dust trails from dust
tails. Unlike dust tails, dust trails only weakly respond to solar
radiation pressure and, therefore, likely represent the largest (>
1 mm) grains ejected from the nucleus. We also compare observations
to model images in order to determine the extent of recent coma
activity. Water sublimation is expected to be greatly extinguished on
comet surfaces by 3.5 AU. Dust structures observed outside of this
rh could arise from recent coma activity (timescales up to weeks)
caused by the sublimation of highly volatile ices (such as CO2) or the
crystallization of amorphous water ice. Alternatively, the observed
dust may be slowly dispersing grains ejected at a much earlier epoch
(timescales up to years) when water sublimation dominated coma activity.
---------------------------------------------------------
Title: Three-dimensional reconstruction of the streamer belt and
other large-scale structures of the solar corona. I. Method
Authors: Saez, F.; Llebaria, A.; Lamy, P.; Vibert, D.
2007A&A...473..265S Altcode:
Context: The high spatial resolution, white-light images obtained by
the LASCO coronagraphs provide a detailed record of the solar corona
over almost a full solar cycle. Their analysis and interpretation poses
a formidable challenge for ultimately retrieving the 3-dimensional
distribution of electrons in the corona. <BR />Aims: Our goal is to
implement an efficient forward modeling method capable of generating
high-resolution synthetic images of large-scale coronal structures
(the streamer belt, isolated streamers, coronal mass ejections) over
any time scales (as long as a solar cycle) to be directly compared,
both qualitatively and quantitatively, to coronographic images of the
corona. <BR />Methods: Our model assumes a 3-dimensional distribution
of electrons described by analytic functions and represented using
the octree compression's techniques. The radiance of the synthetic
images is calculated with a ray-tracing algorithm that incorporates
the Thomson scattering. A multi-octree generalization of the method
allows simulation of the temporal evolution of the structures. We first
concentrate on the coronal streamer belt. Starting from photospheric
magnetograms, we calculate the position of the neutral line at the
source surface (2.5 R_sun) using the potential field source surface
model. The plasma sheet forming the belt is centered on the current
sheet represented as the radial extension of the neutral line. Its
electron density is represented by a parametric function of both the
distances to the Sun center and to the current sheet. The parameters
are optimized by adjusting the synthetic images to the observations,
using either the coronal images or synoptic maps of the corona. The
method is then extended to other large-scale coronal structures,
polar plumes, and coronal mass ejections. <BR />Results: As examples,
we present results for the streamer belt observed by LASCO-C2 during two
Carrington rotations, CR 1910 and CR 1913, as well as illustrations of
future coronographic observations expected from the STEREO and Solar
Orbiter missions. The results suggest that our method is sufficient
for qualitatively and quantitatively simulating the structures of the
solar corona even if some discrepancies can be noticed. A systematic
analysis of the LASCO data over almost a full solar cycle will be
developed in forthcoming articles.
---------------------------------------------------------
Title: Thermal Properties, Size Distribution, and Albedo Distribution
of Jupiter-Family Comets
Authors: Fernandez, Yanga R.; Kelley, M. S.; Lamy, P. L.; Toth, I.;
Groussin, O.; Lisse, C. M.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.;
Fitzsimmons, A.; Licandro, J.; Lowry, S. C.; Meech, K. J.; Pittichova,
J.; Reach, W. T.; Weaver, H. A.
2007DPS....39.4301F Altcode: 2007BAAS...39..497F
We present results from SEPPCoN (Survey of Ensemble Physical Properties
of Cometary Nuclei), a survey of 100 Jupiter-family comets (JFCs) using
the Spitzer Space Telescope for mid-infrared measurements of thermal
emission and several ground-based telescopes for visible-wavelength
measurements of reflected sunlight. Our sample represents about 30%
of all known JFCs. The Spitzer observations are complete, and each
comet was observed at either two wavelengths (16 and 22 μm) or at
one wavelength twice (24 μm). Our survey constrains the effective
radii of the JFC nuclei and thence the size distribution while only
assuming that cometary geometric albedos are low (few percent); we need
not assume that they are all the same. Also, nearly all survey targets
were observed when farther than 4 AU from the Sun to minimize (and in
most cases eliminate) coma confusion. Using the observations of comets
at two wavelengths, and using the Near-Earth Asteroid Thermal Model, we
have estimated the JFC ensemble-average beaming parameter to be about
1.1. On average, cometary nuclei seem to have low thermal inertia and
not have significant infrared beaming, although we do find that some of
our survey targets have significantly higher parameters and thus likely
higher thermal inertia. Analysis on the cumulative size distribution
continues and we present our preliminary estimate of its shape, as well
as the implications for the assumption of uniform albedo and for the
extent of the small-comet (sub-km) population. So far we have obtained
visible magnitudes on almost half of our targets; we plan to complete
this part of the survey in the coming years. With these data we will
constrain the JFC albedo distribution and again address the question
of albedo uniformity; current progress on this task is reported as
well. We thank the Spitzer Science Center for supporting this research.
---------------------------------------------------------
Title: Active Regions On The Nucleus Of Comet
67P/Churyumov-Gerasimenko
Authors: Groussin, Olivier; Lamy, P.; Jorda, L.; Besse, S.
2007DPS....39.3601G Altcode: 2007BAAS...39..485G
Rosetta will orbit and land on comet 67P/Churyumov-Gerasimenko in
2014. The planning of the mission depends strongly on the location and
intensity of active regions. We have developped a model to calculate the
water production rate of 67P as a function of heliocentric distance. Our
model takes into account the orbital elements of 67P, the orientation of
the pole, the rotational period, the shape (spherical or more complex)
and the localisation and type of active regions (either small, very
active regions or extended, low active regions). The comparison between
the water production rates calculated by the model and the compilation
of water production rates from the 1982 and 1996 perihelion passages by
D.G. Schleicher (2006, Icarus 181, 442-457) gives some constraints on
the localisation of active regions. A particular emphasis is placed
on reproducing the rotational variability of the water production
rate. <P />We derive that one small very active region covering about
4-5% of the nucleus surface and located in the Northern hemisphere at
a latitude of about +65 degree is sufficient to match the data and
their temporal variations. Two small active regions located in the
Northern hemisphere is not excluded but less probable. One extended,
low active region covering about 60% of the nucleus surface can also
fit the data, but only the part in the Northern hemisphere contributes
to the production rate at perihelion. The case with one region only,
located in the Southern hemisphere, is excluded, so that there must be
active regions in the Northern hemisphere of 67P. Finally, we conclude
that the shape (spherical or more complex) has no influence on the
localisation of the active regions. <P />This work was supported by
a grant from the CNES.
---------------------------------------------------------
Title: The giant externally occulted coronagraph ASPIICS for the
PROBA-3 formation flying mission
Authors: Vivès, Sébastien; Lamy, Philippe; Venet, Melanie; Levacher,
Patrick; Boit, J. L.
2007SPIE.6689E..0FV Altcode: 2007SPIE.6689E..11V
Formation flying opens new perspectives in solar physics, and
allow to conceive giant, externally-occulted coronagraphs using
a two-component space system with the external occulter on one
spacecraft and the optical instrument on the other spacecraft at a
distance of hundred meters. ASPIICS (Association de Satellites Pour
l'Imagerie et l'Interferometrie de la Couronne Solaire) is a mission
proposed to ESA in the framework of its PROBA-3 demonstration program
of formation flying which is presently in phase A. ASPIICS is a single
coronagraph which will perform both high spatial resolution imaging
of the solar corona as well as 2-dimensional spectroscopy of several
emission lines from the coronal base out to 3 R(symbol) using an etalon
Fabry-Perot interferometer. The selected lines will allow to address
different coronal regions: the forbidden line of FeXIV at 530.285 nm
(hot coronal matter), Fe IX/X at 637.4 nm (coronal holes), HeI at
587.6 nm (cold matter). An additional broad spectral channel will
image the white light corona so as to derive electron densities. The
classical design of an externally-occulted coronagraph is adapted to
the formation flying configuration allowing the detection of the very
inner corona as close as 0.01 R(symbol) from the solar limb.
---------------------------------------------------------
Title: The BepiColombo Laser Altimeter (BELA): Concept and baseline
design
Authors: Thomas, N.; Spohn, T.; Barriot, J. -P.; Benz, W.; Beutler,
G.; Christensen, U.; Dehant, V.; Fallnich, C.; Giardini, D.; Groussin,
O.; Gunderson, K.; Hauber, E.; Hilchenbach, M.; Iess, L.; Lamy, P.;
Lara, L. -M.; Lognonné, P.; Lopez-Moreno, J. J.; Michaelis, H.;
Oberst, J.; Resendes, D.; Reynaud, J. -L.; Rodrigo, R.; Sasaki, S.;
Seiferlin, K.; Wieczorek, M.; Whitby, J.
2007P&SS...55.1398T Altcode:
The BepiColombo Laser Altimeter (BELA) has been selected for flight on
board the European Space Agency's BepiColombo Mercury Planetary Orbiter
(MPO). The experiment is intended to be Europe's first planetary laser
altimeter system. Although the proposed system has similarities to the
Mercury Laser Altimeter (MLA) currently flying on board NASA's MESSENGER
mission to Mercury, the specific orbit and construction of the MPO
force the use of novel concepts for BELA. Furthermore, the base-lined
range-finding approach is novel. In this paper, we describe the BELA
system and show preliminary results from some prototype testing.
---------------------------------------------------------
Title: Old and New Aspects of Prominence Physics from Coronal
Observations
Authors: Koutchmy, S.; Filippov, B.; Lamy, P.
2007ASPC..368..331K Altcode:
Classical W-L eclipse observations at typical spatial resolution
of 10 arcsec show dark cavities surrounding prominences. Images at
higher spatial resolution processed with a spatial filter reveal
small dynamical cool clouds moving inside the inner corona around
prominences. More recently EIT/SoHO observations taken using the
304 Å channel showed He<SUP>+</SUP> prominences sometimes not seen
in cooler lines. TRACE movies of the Fe IX and XI emissions where
prominences are seen in absorption also bring appreciable informations
on the dynamical surrounding of prominences, without showing obvious
correlations between prominence and coronal structures. Accordingly,
we re-examine the significance of the cavity and propose a possible
interpretation as magnetic interlaced 3-D flux ropes and loops
evacuating the corona, in addition to twisted flux ropes where the
prominence plasma is condensing. Future space missions like ASPIICS
should pay more attention to cavities and emptiness, to coronal dynamics
around prominences, in order to resolve the long-standing problem of
the origin of prominences and perhaps, perform a new diagnostic of
the erupting process responsible for many CMEs.
---------------------------------------------------------
Title: Characterization of Asteroid 2867 Steins, a Target of the
Rosetta Mission
Authors: Lamy, Philippe; Barucci, Antonella; Dotto, Elisabetta;
Fornasier, Sonia; Fulchignoni, Marcello; Groussin, Olivier; Jorda,
Laurent
2007sptz.prop40259L Altcode:
We propose to re-observe asteroids 2867 Steins, one of the target
of the Rosetta mission in order to definitevely ascertain its
taxonomic classification and its surface composition. Our previous SST
observations performed during cycle 2 had to assume a much bigger size
than presently established, and our spectra do not have a good enough
signal-over-noise ratio to clearly distinguish the exact position of
the different bands. The proposed SST observations consist in taking
low resolution spectra with the IRS instrument over its full wavelength
range 5-38 micron so as to reach a signal-over-noise ratio larger than
200 in the 7-20 micron spectral range which is of prime interest for
identification of the mineralogical features. Five individual spectra
will be obtained for a total observing time of 1.4 hr. The expected
results will allow identifying the mineralogical signatures so as to
determine the taxonomic classification, the surface composition and
possible weathering processes.
---------------------------------------------------------
Title: Chromospheric and Prominence Physics with the ASPIICS Formation
Flying Coronagraph
Authors: Lamy, P.; Vivès, S.; Koutchmy, S.; Arnaud, J.
2007ASPC..368..639L Altcode:
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
observing the inner corona inside typically 2--2.5 solar radii
(R<SUB>⊙</SUB>). Formation flying opens new perspectives and allow to
conceive giant, externally-occulted coronagraphs using a two-component
space system with the external occulter on one spacecraft and the
optical instrument on the other spacecraft. ASPIICS (Association
de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne
Solaire) is a mission proposed to ESA in the framework of the PROBA-3
program of formation flying which is presently under study, to exploit
this technique for coronal observations. ASPIICS is composed of a
single coronagraph which performs high spatial resolution imaging of
the corona as well as 2-dimensional spectroscopy of several emission
lines (in particular the forbidden line of Fe XIV at 530.285 nm) from
the coronal base out to 3 R<SUB>⊙</SUB>. The classical design of an
externally occulted coronagraph is adapted to the detection of the very
inner corona, and the addition of a Fabry-Pérot interferometer. By
tuning the position of the occulter spacecraft, it will be possible to
reach the chromosphere and the upper part of the spicules. Filtergrams
on the helium D3 line or even better, the hydrogen Hβ line (which is
optically thin contrary to Hα) will give access to the “cold corona”,
and could allow measuring the chromospheric prolateness.
---------------------------------------------------------
Title: Measuring the physical properties of the nucleus of comet
8P/Tuttle
Authors: Groussin, Olivier; Fernandez, Yanga; Jorda, Laurent; Kelley,
Michael; Lamy, Philippe; Toth, Imre; Weaver, Hal
2007sptz.prop40270G Altcode:
Comet 8P/Tuttle is a returning nearly isotropic comet (NIC), i.e.,
an 'Oort cloud comet', with an outstanding apparition in cycle 4,
passing within 0.25 AU of the Earth. We propose to observe it with
MIPS (photometry at 24 and 70 micron) and IRS (spectroscopy in the
5-38 micron range), to measure the physical properties of its nucleus:
size, shape, rotation period, thermal inertia and mineralogy. This will
provide the most detailed view of a NIC nucleus since the spacecraft
flyby of 1P/Halley in 1986. The return of 8P is a rare opportunity
that Spitzer should not miss. The results should yield a comprehensive
picture of this NIC that can be compared to the detailed data collected
on ecliptic comets (ECs) during the past 3 decades. The differences
and similarities between NICs and ECs should yield valuable insights
into the origin and evolution of comets.
---------------------------------------------------------
Title: The long-term evolution and initial size of comets 46P/Wirtanen
and 67P/Churyumov-Gerasimenko
Authors: Groussin, O.; Hahn, G.; Lamy, P. L.; Gonczi, R.; Valsecchi,
G. B.
2007MNRAS.376.1399G Altcode: 2007MNRAS.tmp..179G
We present a new method to study the long-term evolution of
cometary nuclei in order to estimate their original size, and
we consider the case of comets 46P/Wirtanen (hereafter 46P) and
67P/Churyumov-Gerasimenko (hereafter 67P). We calculate the past
evolution of the orbital elements of both comets over 100000yr
using a Bulirsch-Stoer integrator and over 450000yr using a Radau
integrator, and we incorporate a realistic model of the erosion of
their nucleus. Their long-term orbital evolution is prominently chaotic,
resulting from several close encounters with planets, and this result
is independent of the choice of the integrator and of the presence
or not of non-gravitational forces. The dynamical lifetime of comet
46P is estimated at ~133000yr and that of comet 67P at ~105000yr. Our
erosion model assumes a spherical nucleus composed of a macroscopic
mixture of two thermally decoupled components, dust and pure water
ice. Erosion strongly depends upon the active fraction and the density
of the nucleus. It mainly takes place at heliocentric distances <4au
and lasts for only ~7 per cent of the lifetime. Assuming a density
of 300kgm<SUP>-3</SUP> and an average active fraction over time of 10
per cent, we find an initial radius of ~1.3km for 46P and ~2.8km for
67P. Upper limit are obtained assuming a density of 100kgm<SUP>-3</SUP>
and an active fraction of 100 per cent, and amounts to 21km for
46P and 25km for 67P. Erosion acts as a rejuvenating process of the
surface so that exposed materials on the surface may only contain
very little quantities of primordial materials. However, materials
located just under it (a few centimetres to metres) may still be much
less evolved. We will apply this method to several other comets in
the future.
---------------------------------------------------------
Title: Rotational state of the nucleus of Comet 9P/Tempel 1: Results
from Hubble Space Telescope observations in 2004
Authors: Lamy, Philippe L.; Toth, Imre; A'Hearn, Michael F.; Weaver,
Harold A.; Jorda, Laurent
2007Icar..187..132L Altcode:
The nucleus of Comet 9P/Tempel 1 was first observed with the Hubble
Space Telescope (HST) in December 1997 [Lamy, P., Toth, I., A'Hearn,
M.F., Weaver, H., Weissman, P.R., 2001. Icarus 154, 337-344], but
the temporal coverage was insufficient to determine its rotational
period. Because the success of the Deep Impact mission was critically
dependent on understanding the rotational state and approximate shape
and size of the nucleus, we extensively re-observed 9P/Tempel 1,
this time with the Advanced Camera for Surveys (HST/ACS), from May
7.9 to 9.5, 2004 (UT). At the mid-point of the observing window, the
comet was 3.52 AU from the Sun, 4.03 AU from the Earth, and at a solar
phase angle of 13.3°. The program was comprised of 18 separate visits,
each one corresponding to an HST orbit filled with 3 ACS exposures of
either 800 or 857 s duration with the F606W broadband filter. These
very deep exposures revealed a star-like object, without any apparent
coma. The light curve, defined by 49 data points, is characterized
by a mean apparent V magnitude of 21.8 and an amplitude of 0.5 mag,
indicating that we were viewing the varying cross-section of a rotating,
elongated body. The periodicity was analyzed with seven different
techniques yielding a rotational period in the range 39.40 to 43.00 h,
and a mean value of 41.27±1.85 h (1 σ). Using an albedo p=0.04 and a
linear phase law with a coefficient β=0.0465 magdeg, we determined an
effective radius of 3.01 km; a possible prolate spheroid solution has
semi-axes a=3.71 km, b=2.36 km and a minimum axial ratio a/b∼1.57. By
comparing the light curves obtained in 1997 and in 2004, we were able
to constrain the phase function of the nucleus. Finally, an upper
limit of Afρ<0.04 cm is set based on the non-detection of the coma.
---------------------------------------------------------
Title: Observations of Comet 9P/Tempel 1 around the Deep Impact
event by the OSIRIS cameras onboard Rosetta
Authors: Keller, Horst Uwe; Küppers, Michael; Fornasier, Sonia;
Gutiérrez, Pedro J.; Hviid, Stubbe F.; Jorda, Laurent; Knollenberg,
Jörg; Lowry, Stephen C.; Rengel, Miriam; Bertini, Ivano; Cremonese,
Gabriele; Ip, Wing-H.; Koschny, Detlef; Kramm, Rainer; Kührt,
Ekkehard; Lara, Luisa-Maria; Sierks, Holger; Thomas, Nicolas; Barbieri,
Cesare; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; A'Hearn,
Michael F.; Angrilli, Francesco; Barucci, Maria-Antonella; Bertaux,
Jean-Loup; da Deppo, Vania; Davidsson, Björn J. R.; de Cecco,
Mariolino; Debei, Stefano; Fulle, Marco; Gliem, Fritz; Groussin,
Olivier; Lopez Moreno, José J.; Marzari, Francesco; Naletto,
Giampiero; Sabau, Lola; Sanz Andrés, Angel; Wenzel, Klaus-Peter
2007Icar..187...87K Altcode:
The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel
1 from 5 days before to 10 days after it was hit by the Deep Impact
projectile. The Narrow Angle Camera (NAC) monitored the cometary dust
in 5 different filters. The Wide Angle Camera (WAC) observed through
filters sensitive to emissions from OH, CN, Na, and OI together with
the associated continuum. Before and after the impact the comet showed
regular variations in intensity. The period of the brightness changes
is consistent with the rotation period of Tempel 1. The overall
brightness of Tempel 1 decreased by about 10% during the OSIRIS
observations. The analysis of the impact ejecta shows that no new
permanent coma structures were created by the impact. Most of the
material moved with ∼200ms. Much of it left the comet in the form
of icy grains which sublimated and fragmented within the first hour
after the impact. The light curve of the comet after the impact and
the amount of material leaving the comet ( 4.5-9×10kg of water ice
and a presumably larger amount of dust) suggest that the impact ejecta
were quickly accelerated by collisions with gas molecules. Therefore,
the motion of the bulk of the ejecta cannot be described by ballistic
trajectories, and the validity of determinations of the density and
tensile strength of the nucleus of Tempel 1 with models using ballistic
ejection of particles is uncertain.
---------------------------------------------------------
Title: Properties of the dust cloud caused by the Deep Impact
experiment
Authors: Jorda, L.; Lamy, P.; Faury, G.; Keller, H. U.; Hviid, S.;
Küppers, M.; Koschny, D.; Lecacheux, J.; Gutiérrez, P.; Lara, L. M.
2007Icar..187..208J Altcode:
We present an analysis of the observations of the Deep Impact event
performed by the OSIRIS narrow angle camera aboard the Rosetta
spacecraft over two weeks, in an effort to characterize the cometary
dust grains ejected from the nucleus of Comet 9P/Tempel 1. We adopt
a Monte Carlo approach to generate calibrated synthetic images, and
a linear combination of them is fitted to the calibrated images so
as to determine the physical parameters of the dust cloud. Our model
considers spherical olivine particles with a density of 3780 kg m
<SUP>-3</SUP>. It incorporates constraints on the direction of the
cone of emission coming from additional images obtained at Pic du Midi
observatory, and constraints on the dust terminal velocities coming from
the physics of the impact. We find that the slope of the differential
dust size distribution of grains with radii <20 μm ( β>0.008)
is 3.1±0.3, a value typical of cometary dust tails. This shows that
there is no evidence in our data for an enhancement in sub-micron
particles in the ejecta compared to the typical dust distribution of
active comets. We estimate the mass of particles with radii <1.4 μm
( β>0.14) to be 1.5±0.2×10 kg. These particles represent more
than 80% of the cross-section of the observed dust cloud. The mass
carried by larger particles depends whether the gas significantly
increases the kinetic energy of the grains in the inner coma; it
lies in the range 1-14×10 kg for particles with radii <100 μm
( β>0.002). We obtain the distribution of terminal velocities
reached by the dust after the dust-gas interaction which is very well
constrained between 10 and 600 m s <SUP>-1</SUP>. It is characterized
by Gaussian with a maximum at about 190 m s <SUP>-1</SUP> and a width
at half maximum of 150 m s <SUP>-1</SUP>.
---------------------------------------------------------
Title: Commission 21: Light of the Night Sky
Authors: Gustafson, Bo Å. S.; Witt, Adolf N.; Dwek, E.; Lamy, P.;
Henry, R.; Mann, I.
2007IAUTA..26..161G Altcode:
Commission 21, one of IAU's smallest commissions, consists of some
hundred members and consultants working to understand and describe the
light of the night sky with emphasis on the diffuse components. Many
more work on these topics without being members of the commission. Light
is here defined in its broader sense of electromagnetic radiation of
any frequency. The diffuse components of the light of the night sky
encompass a variety of physical phenomena over the full range of cosmic
distance scales and include scattered light, thermal emission, line
emission, and any other emission phenomena producing a diffuse light
source. These attract interest not only as scientific topics of study
in their own right but also as an unwanted foreground or background
against which all other sky phenomena are observed. Commission 21 has
for mandate to promote research and availability of results on issues
related to the diffuse light of the night sky. This document is a report
on activities in this field and is not confined to the activities of its
members, no distinction is made between work carried out by commission
members and non commission members. The report is organized starting
with a summary of the state of broad surveys that provide most of the
observations. The report on developments in the various disciplines
start with the sources closest to the observer known as airglow and
progresses by way of the interplanetary and interstellar mediums to
the increasingly distant integrated starlight, diffuse galactic light
and diffuse emission in other galaxies ending with the extragalactic
background radiation.
---------------------------------------------------------
Title: OSIRIS The Scientific Camera System Onboard Rosetta
Authors: Keller, H. U.; Barbieri, C.; Lamy, P.; Rickman, H.; Rodrigo,
R.; Wenzel, K. -P.; Sierks, H.; A'Hearn, M. F.; Angrilli, F.; Angulo,
M.; Bailey, M. E.; Barthol, P.; Barucci, M. A.; Bertaux, J. -L.;
Bianchini, G.; Boit, J. -L.; Brown, V.; Burns, J. A.; Büttner, I.;
Castro, J. M.; Cremonese, G.; Curdt, W.; Deppo, V. Da; Debei, S.;
Cecco, M. De; Dohlen, K.; Fornasier, S.; Fulle, M.; Germerott, D.;
Gliem, F.; Guizzo, G. P.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Koschny,
D.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Llebaria,
A.; López, A.; López-Jimenez, A.; López-Moreno, J.; Meller, R.;
Michalik, H.; Michelena, M. D.; Müller, R.; Naletto, G.; Origné, A.;
Parzianello, G.; Pertile, M.; Quintana, C.; Ragazzoni, R.; Ramous,
P.; Reiche, K. -U.; Reina, M.; Rodríguez, J.; Rousset, G.; Sabau,
L.; Sanz, A.; Sivan, J. -P.; Stöckner, K.; Tabero, J.; Telljohann,
U.; Thomas, N.; Timon, V.; Tomasch, G.; Wittrock, T.; Zaccariotto, M.
2007SSRv..128..433K Altcode: 2007SSRv..tmp...26K
The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS
is the scientific camera system onboard the Rosetta spacecraft
(Figure 1). The advanced high performance imaging system will be
pivotal for the success of the Rosetta mission. OSIRIS will detect
67P/Churyumov-Gerasimenko from a distance of more than 10<SUP>6</SUP>
km, characterise the comet shape and volume, its rotational state and
find a suitable landing spot for Philae, the Rosetta lander. OSIRIS
will observe the nucleus, its activity and surroundings down to a
scale of ~2 cm px<SUP>−1</SUP>. The observations will begin well
before the onset of cometary activity and will extend over months
until the comet reaches perihelion. During the rendezvous episode of
the Rosetta mission, OSIRIS will provide key information about the
nature of cometary nuclei and reveal the physics of cometary activity
that leads to the gas and dust coma.
---------------------------------------------------------
Title: Civa
Authors: Bibring, J. -P.; Lamy, P.; Langevin, Y.; Soufflot, A.;
Berthé, M.; Borg, J.; Poulet, F.; Mottola, S.
2007SSRv..128..397B Altcode: 2007SSRv..tmp...81B
CIVA (Comet Infrared and Visible Analyser) is an integrated set of
imaging instruments, designed to characterize the 360<SUP>∘</SUP>
panorama (CIVA-P) as seen from the Rosetta Lander Philae, and to study
surface and subsurface samples (CIVA-M). CIVA-P is a panoramic stereo
camera, while CIVA-M is an optical microscope coupled to a near infrared
microscopic hyperspectral imager. CIVA shares a common Imaging Main
Electronics (IME) with ROLIS. CIVA-P will characterize the landing site,
with an angular sampling (IFOV) of 1.1 mrad: each pixel will image
a 1 mm size feature at the distance of the landing legs, and a few
metres at the local horizon. The panorama will be mapped by 6 identical
miniaturized micro-cameras covering contiguous FOV, with their optical
axis 60<SUP>∘</SUP> apart. Stereoscopic capability will be provided
by an additional micro-camera, identical to and co-aligned with one
of the panoramic micro-camera, with its optical axis displaced by 10
cm. CIVA-M combines two ultra-compact and miniaturised microscopes,
one operating in the visible and one constituting an IR hyperspectral
imaging spectrometer: they will characterize, by non-destructive
analyses, the texture, the albedo, the molecular and the mineralogical
composition of each of the samples provided by the Sample Drill and
Distribution (SD2) system. For the optical microscope, the spatial
sampling is 7 μm; for the IR, the spectral range (1-4 μm) and the
spectral sampling (5 nm) have been chosen to allow identification of
most minerals, ices and organics, on each pixel, 40 μm in size. After
being studied by CIVA, the sample could be analysed by a subsequent
experiment (PTOLEMY and/or COSAC). The process would be repeated for
each sample obtained at different depths and/or locations.
---------------------------------------------------------
Title: A Portrait of the Nucleus of Comet 67P/Churyumov-Gerasimenko
Authors: Lamy, Philippe L.; Toth, Imre; Davidsson, Björn J. R.;
Groussin, Olivier; Gutiérrez, Pedro; Jorda, Laurent; Kaasalainen,
Mikko; Lowry, Stephen C.
2007SSRv..128...23L Altcode: 2007SSRv..tmp...74L
In 2003, comet 67P/Churyumov-Gerasimenko was selected as the new target
of the Rosetta mission as the most suitable alternative to the original
target, comet 46P/Wirtanen, on the basis of orbital considerations
even though very little was known about the physical properties of
its nucleus. In a matter of a few years and based on highly focused
observational campaigns as well as thorough theoretical investigations,
a detailed portrait of this nucleus has been established that will serve
as a baseline for planning the Rosetta operations and observations. In
this review article, we present a novel method to determine the size
and shape of a cometary nucleus: several visible light curves were
inverted to produce a size-scale free three-dimensional shape, the
size scaling being imposed by a thermal light curve. The procedure
converges to two solutions which are only marginally different. The
nucleus of comet 67P/Churyumov-Gerasimenko emerges as an irregular
body with an effective radius (that of the sphere having the same
volume) = 1.72 km and moderate axial ratios a/b = 1.26 and a/c =
1.5 to 1.6. The overall dimensions measured along the principal axis
for the two solutions are 4.49-4.75 km, 3.54-3.77 km and 2.94-2.92
km. The nucleus is found to be in principal axis rotation with a
period = 12.4-12.7 h. Merging all observational constraints allow us
to specify two regions for the direction of the rotational axis of
the nucleus: RA = 220°<SUP>+50°</SUP><SUB>−30°</SUB> and Dec =
−70<SUP>°</SUP> ± 10<SUP>°</SUP> (retrograde rotation) or RA =
40°<SUP>+50°</SUP><SUB>-30°</SUB> and Dec = +70<SUP>°</SUP>±
10<SUP>°</SUP> (prograde), the better convergence of the various
determinations presently favoring the first solution. The phase
function, although constrained by only two data points, exhibits a
strong opposition effect rather similar to that of comet 9P/Tempel
1. The definition of the disk-integrated albedo of an irregular body
having a strong opposition effect raises problems, and the various
alternatives led to a R-band geometric albedo in the range 0.045-0.060,
consistent with our present knowledge of cometary nuclei. The active
fraction is low, not exceeding ~ 7% at perihelion, and is probably
limited to one or two active regions subjected to a strong seasonal
effect, a picture coherent with the asymmetric behaviour of the
coma. Our slightly downward revision of the size of the nucleus of
comet 67P/Churyumov-Gerasimenko resulting from the present analysis
(with the correlative increase of the albedo compared to the originally
assumed value of 0.04), and our best estimate of the bulk density of
370 kg m<SUP>−3</SUP>, lead to a mass of ~ 8 × 10<SUP>12</SUP>
kg which should ease the landing of Philae and insure the overall
success of the Rosetta mission.
---------------------------------------------------------
Title: Properties of the dust cloud caused by the Deep Impact
experiment
Authors: Jorda, L.; Lamy, P.; Faury, G.; Keller, H. U.; Hviid, S.;
Küppers, M.; Koschny, D.; Lecacheux, J.; Gutiérrez, P.; Lara, L. M.
2007Icar..191S.412J Altcode: 2007Icar..191..412J
We present an analysis of the observations of the Deep Impact event
performed by the OSIRIS narrow angle camera aboard the Rosetta
spacecraft over two weeks, in an effort to characterize the cometary
dust grains ejected from the nucleus of Comet 9P/Tempel 1. We adopt
a Monte Carlo approach to generate calibrated synthetic images,
and a linear combination of them is fitted to the calibrated images
so as to determine the physical parameters of the dust cloud. Our
model considers spherical olivine particles with a density of 3780
kg m<SUP>-3</SUP>. It incorporates constraints on the direction of the
cone of emission coming from additional images obtained at Pic du Midi
observatory, and constraints on the dust terminal velocities coming from
the physics of the impact. We find that the slope of the differential
dust size distribution of grains with radii <20 μm (β>0.008)
is 3.1±0.3, a value typical of cometary dust tails. This shows that
there is no evidence in our data for an enhancement in sub-micron
particles in the ejecta compared to the typical dust distribution of
active comets. We estimate the mass of particles with radii <1.4
μm (β>0.14) to be 1.5±0.2×10<SUP></SUP> kg. These particles
represent more than 80% of the cross-section of the observed dust
cloud. The mass carried by larger particles depends whether the gas
significantly increases the kinetic energy of the grains in the inner
coma; it lies in the range 1 14×10<SUP></SUP> kg for particles with
radii <100 μm (β>0.002). We obtain the distribution of terminal
velocities reached by the dust after the dust gas interaction which
is very well constrained between 10 and 600 m s<SUP>-1</SUP>. It is
characterized by Gaussian with a maximum at about 190 m s<SUP>-1</SUP>
and a width at half maximum of 150 m s<SUP>-1</SUP>.
---------------------------------------------------------
Title: Determination of the light curve of the Rosetta target asteroid
(2867) Steins by the OSIRIS cameras onboard Rosetta
Authors: Küppers, M.; Mottola, S.; Lowry, S. C.; A'Hearn, M. F.;
Barbieri, C.; Barucci, M. A.; Fornasier, S.; Groussin, O.; Gutiérrez,
P.; Hviid, S. F.; Keller, H. U.; Lamy, P.
2007A&A...462L..13K Altcode: 2006astro.ph.12097K
Context: In 2004 asteroid (2867) Steins has been selected as a flyby
target for the Rosetta mission. Determination of its spin period and
the orientation of its rotation axis are essential for optimization
of the flyby planning. <BR />Aims: Measurement of the rotation period
and light curve of asteroid (2867) Steins at a phase angle larger than
achievable from ground based observations, providing a high quality
data set to contribute to the determination of the orientation of the
spin axis and of the pole direction. <BR />Methods: On March 11, 2006,
asteroid (2867) Steins was observed continuously for 24 h with the
scientific camera system OSIRIS onboard Rosetta. The phase angle was
41.7 degrees, larger than the maximum phase angle of 30 degrees when
Steins is observed from Earth. A total of 238 images, covering four
rotation periods without interruption, were acquired. <BR />Results:
The light curve of (2867) Steins is double peaked with an amplitude of
≈0.23 mag. The rotation period is 6.052~± 0.007 h. The continuous
observations over four rotation periods exclude the possibility
of period ambiguities. There is no indication of deviation from a
principal axis rotation state. Assuming a slope parameter of G = 0.15,
the absolute visual magnitude of Steins is 13.05 ± 0.03. <P />Table
2 is only available in electronic form at http://www.aanda.org
---------------------------------------------------------
Title: Hubble Space Telescope observations of the nucleus of Comet
9P/Tempel 1
Authors: Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Weaver, H. A.;
Weissman, P. R.
2007Icar..191S...4L Altcode: 2007Icar..191....4L
The nucleus of Comet 9P/Tempel 1, the target of the Deep Impact mission,
was detected during Hubble Space Telescope observations taken with
the wide-field planetary camera 2 (WFPC2) on 31 December 1997 when
the comet's solar phase angle was 3.°8, its heliocentric distance was
4.48 AU, and its geocentric distance was 3.53 AU. Sixteen images were
taken through the F675W filter, and all of them revealed a point-like
source without any detectable coma. From these images, we derived the
R magnitude of the nucleus in the Johnson Kron Cousins photometric
system for the entire 11.5-h time span of the observations. Assuming
a prolate spheroid whose spin axis lies close to the plane of the
sky, the partial lightcurve indicates semi-axes a-3.9 km and b-2.8
km (assuming a geometric albedo of 0.04 for the R band and a phase
coefficient of 0.04 mag deg<SUP>-1</SUP>) and a rotational period
in the range of ∼25-33 h. The upper limit of the parameter Afρ,
which characterizes the dust production rate, is 1 cm. We also derive
a fractional active area at 1.78 AU of ∼4%.
---------------------------------------------------------
Title: Observations of Comet 9P/Tempel 1 around the Deep Impact
event by the OSIRIS cameras onboard Rosetta
Authors: Keller, Horst Uwe; Küppers, Michael; Fornasier, Sonia;
Gutiérrez, Pedro J.; Hviid, Stubbe F.; Jorda, Laurent; Knollenberg,
Jörg; Lowry, Stephen C.; Rengel, Miriam; Bertini, Ivano; Cremonese,
Gabriele; Ip, Wing-H.; Koschny, Detlef; Kramm, Rainer; Kührt,
Ekkehard; Lara, Luisa-Maria; Sierks, Holger; Thomas, Nicolas; Barbieri,
Cesare; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; A'Hearn,
Michael F.; Angrilli, Francesco; Barucci, Maria-Antonella; Bertaux,
Jean-Loup; da Deppo, Vania; Davidsson, Björn J. R.; de Cecco,
Mariolino; Debei, Stefano; Fulle, Marco; Gliem, Fritz; Groussin,
Olivier; Lopez Moreno, José J.; Marzari, Francesco; Naletto,
Giampiero; Sabau, Lola; Sanz Andrés, Angel; Wenzel, Klaus-Peter
2007Icar..191S.241K Altcode: 2007Icar..191..241K
The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel
1 from 5 days before to 10 days after it was hit by the Deep Impact
projectile. The Narrow Angle Camera (NAC) monitored the cometary dust
in 5 different filters. The Wide Angle Camera (WAC) observed through
filters sensitive to emissions from OH, CN, Na, and OI together with
the associated continuum. Before and after the impact the comet showed
regular variations in intensity. The period of the brightness changes is
consistent with the rotation period of Tempel 1. The overall brightness
of Tempel 1 decreased by about 10% during the OSIRIS observations. The
analysis of the impact ejecta shows that no new permanent coma
structures were created by the impact. Most of the material moved
with ∼200ms<SUP></SUP>. Much of it left the comet in the form of icy
grains which sublimated and fragmented within the first hour after the
impact. The light curve of the comet after the impact and the amount
of material leaving the comet (4.5 9×10<SUP></SUP>kg of water ice
and a presumably larger amount of dust) suggest that the impact ejecta
were quickly accelerated by collisions with gas molecules. Therefore,
the motion of the bulk of the ejecta cannot be described by ballistic
trajectories, and the validity of determinations of the density and
tensile strength of the nucleus of Tempel 1 with models using ballistic
ejection of particles is uncertain.
---------------------------------------------------------
Title: Rotational state of the nucleus of Comet 9P/Tempel 1: Results
from Hubble Space Telescope observations in 2004
Authors: Lamy, Philippe L.; Toth, Imre; A'Hearn, Michael F.; Weaver,
Harold A.; Jorda, Laurent
2007Icar..191S.310L Altcode: 2007Icar..191..310L
The nucleus of Comet 9P/Tempel 1 was first observed with the Hubble
Space Telescope (HST) in December 1997 [Lamy, P., Toth, I., A'Hearn,
M.F., Weaver, H., Weissman, P.R., 2001. Icarus 154, 337 344], but
the temporal coverage was insufficient to determine its rotational
period. Because the success of the Deep Impact mission was critically
dependent on understanding the rotational state and approximate shape
and size of the nucleus, we extensively re-observed 9P/Tempel 1, this
time with the Advanced Camera for Surveys (HST/ACS), from May 7.9 to
9.5, 2004 (UT). At the mid-point of the observing window, the comet
was 3.52 AU from the Sun, 4.03 AU from the Earth, and at a solar phase
angle of 13.3°. The program was comprised of 18 separate visits, each
one corresponding to an HST orbit filled with 3 ACS exposures of either
800 or 857 s duration with the F606W broadband filter. These very deep
exposures revealed a star-like object, without any apparent coma. The
light curve, defined by 49 data points, is characterized by a mean
apparent V magnitude of 21.8 and an amplitude of 0.5 mag, indicating
that we were viewing the varying cross-section of a rotating, elongated
body. The periodicity was analyzed with seven different techniques
yielding a rotational period in the range 39.40 to 43.00 h, and a mean
value of 41.27±1.85 h (1σ). Using an albedo p<SUB></SUB>=0.04 and
a linear phase law with a coefficient β=0.0465 magdeg<SUP></SUP>, we
determined an effective radius of 3.01 km; a possible prolate spheroid
solution has semi-axes a=3.71 km, b=2.36 km and a minimum axial ratio
a/b∼1.57. By comparing the light curves obtained in 1997 and in 2004,
we were able to constrain the phase function of the nucleus. Finally,
an upper limit of Afρ<0.04 cm is set based on the non-detection
of the coma.
---------------------------------------------------------
Title: Hubble Space Telescope observations of the nucleus and inner
coma of comet 67P/Churyumov-Gerasimenko
Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; Jorda, L.; Kaasalainen,
M.; Gutiérrez, P. J.
2006A&A...458..669L Altcode:
Context: .Following the postponement of the launch of the Rosetta
spacecraft scheduled in January 2003, comet 67P/Churyumov-Gerasimenko
emerged as the most suitable new target. However a critical issue was
the size, that is, the mass of its nucleus, as the surface module
Philae was designed to land on a nucleus with a radius no larger
than approximately 1.5 km. <BR /> Aims: . It was therefore crucial
to the success of the mission to achieve a timely characterization of
the nucleus of 67P/C-G so as to take any proper action on the design
needed before the new launch. <BR /> Methods: . We used the Wide Field
Planetary Camera 2 (WFPC2) of the Hubble Space Telescope (HST) whose
superior spatial resolution enabled us to accurately separate the
signal of the nucleus from that of the coma. The observations were
performed on 12 and 13 March 2003, when the comet was 2.50 AU from
the Sun, 1.52 AU from the Earth, and at a phase angle of 4.8°. <BR
/> Results: . The nucleus of comet 67P/Churyumov-Gerasimenko was
easily detected, and we measured its V and R magnitudes in the
Johnson-Kron-Cousins photometric system. Assuming that the nucleus is
spherical, with a geometric albedo of 0.04 and a phase coefficient of
0.04 mag/deg for the R band, we derived a radius of 1.98±0.02 km. The
spheroidal solution has semiaxes a = 2.41 km and b = c = 1.55 km and
a rotational period of 12.41±0.41 h. We inverted the light curve
and solved it for a full three-dimensional nucleus having an overall
size of 4.56×3.81×3.44 km viewed at an aspect angle of ∼80°
(i.e., near equatorial view) at the time of our observations. When
combined with other constraints, the direction of the pole is
found at either RA = 40°<SUP>+70°</SUP><SUB>-20°</SUB> and Dec =
+70±10° (prograde rotation) or RA = 250±30° and Dec = -70±10°
(retrograde rotation). The color of the nucleus is moderately red
with (V-R)=0.52±0.05. From an analysis of the dust coma, we derived
Afρ = 40.2±0.3 cm, a dust production rate Q<SUB>d</SUB> ∼ 4 kg
s<SUP>-1</SUP>, and we characterized its color. <BR />
---------------------------------------------------------
Title: Determination Of The Light Curve Of Rosetta Target Asteroid
2867 Steins With The Osiris Narrow Angle Camera Onboard Rosetta
Authors: Kueppers, Michael; Keller, H. U.; Hviid, S. F.; Mottola,
S.; Fornasier, S.; Barbieri, C.; Barucci, A.; Gutiérrez, P.; Lamy,
P.; OSIRIS Team
2006DPS....38.5920K Altcode: 2006BAAS...38..596K
On its way to comet 67P/Churyumov-Gerasimenko, the European Space
Agency's Rosetta spacecraft is going to fly by Asteroids 2867 Steins in
Sept. 2008 and 21 Lutetia in July 2010. While 21 Lutetia is a large main
belt asteroid with a long history of investigation, relatively little
is known about 2867 Steins. In particular, knowledge of the rotation
period and the orientation of the rotation axis are valuable for the
flyby preparations. <P />OSIRIS is the scientific camera system onboard
Rosetta, consisting of a narrow angle camera (NAC) and a wide angle
camera (WAC). In March 2006, the NAC observed 2867 Steins continuously
for 24 hours, acquiring 238 images, with a clear filter. The camera
performed flawlessly. The data obtained from spacecraft are unique
in terms of continuous temporal coverage and phase angle. Indeed,
the NAC observations were taken at a phase angle of 42 deg., compared
to a maximum phase angle of 30 deg. when seen from Earth. The distance
between Rosetta and 2867 Steins was 1.06 AU. <P />The OSIRIS data show
a double peaked light curve with an amplitude of 0.23 magnitudes and
a synodic rotation period of 6.052 ± 0.035 hours, in good agreement
with ground based data by Hicks et al. (2004, IAU Circular 8315) and
Weissman et al. (2006, ACM Conference). The continuous observations
over four rotations completely exclude the possibility of period
ambiguities. There is no indication of deviation from a principal axis
rotation state. The observations are being combined with Earth-based
data sets to derive the orientation of the spin axis and pole position
for 2867 Steins. <P />We acknowledge funding from the national space
agencies ASI, CNES, DLR, the Spanish Space Program (Ministerio de
Educación y Ciencia), SNSB, and ESA.
---------------------------------------------------------
Title: Visible and Infrared Observations of Asteroid 2867 Steins,
a target of the Rosetta Mission
Authors: Lamy, Philippe L.; Jorda, L.; Fornasier, S.; Kaasalainen, M.;
Lowry, S.; Barucci, A.; Faury, G.; Kuppers, M.; Toth, I.; Weissman, P.
2006DPS....38.5909L Altcode: 2006BAAS...38..594L
We present the results of a coordinated campaign of visible and infrared
observations aimed at fostering our knowledge of asteroid 2867 Steins
in preparation of its flyby by the Rosetta spacecraft in Sept. 2008,
on its way to comet 67P/Churyumov-Gerasimenko. Our data set includes
16 visible light curves and 14 infrared spectra. Fifteen light curves
were obtained with various ground-based observatories and an additional
one, with the narrow angle camera (NAC) of the OSIRIS scientific camera
aboard Rosetta that continuously monitored 2867 Steins over 24 hr in
March 2006. Simultaneous inversion of the 16 light curves allows to
generate a three-dimensional shape model of 2867 Steins with axial
ratios a/b = 1.2 and b/c = 1.6, to determine its rotational period
(6.0481 ± 0.0004 hr) and two possible solutions for the direction
of its rotational axis. The infrared spectra were obtained with the
low resolution mode of the Spitzer space telescope IRS; they extend
from 5 to 35 microns and sample the rotational light curve with a
temporal resolution of 30 min. Preliminary analysis using a standard
thermal model yield an equivalent diameter of approximately 5 km and
an albedo in the range 0.30 - 0.40. This classifies 2867 Steins as an
E-type asteroid, a class of differentiated bodies which experienced
significant heating episodes. The large beaming factor probably implies
a thermal inertia in the range 150 - 300 SI but this will be further
explored using more elaborated thermal models.
---------------------------------------------------------
Title: HST Observations of the Nucleus Fragment
73P/Schwassmann-Wachmann 3-C During its Close Approach to Earth
in 2006
Authors: Toth, I.; Lamy, P.; Weaver, H.; A'Hearn, M.; Kaasalainen,
M.; Lowry, S.
2006DPS....38.0601T Altcode: 2006BAAS...38..489T
Fragment C of 73P/Schwassmann-Wachmann 3 (73P) was first detected with
the HST-WFPC2 on 26 November 2001 when its heliocentric and geocentric
distances were 3.26 AU and 2.34 AU, respectively. At that time, we
found a very active nucleus with an effective radius of 0.68±0.04
km (Toth et al., 2005: Icarus 178, 235-247). The comet's favorable
apparition in April-May 2006 offered an exceptional opportunity to
re-observe this nucleus at close range. Our observations took place
on 10 April when the comet was 1.24 AU from the Sun, 0.29 AU from the
Earth, and at a phase angle of 31°. They were performed with the HRC
mode of the ACS with three standard filters, F475W ("B"), F555W ("V")
and F625W ("R"), as well as with the broadband F606W (broad "V") to
search for possible orbiting fragments. Fragment C was highly active,
and the nucleus and the coma contributed almost equally in the central
pixels. Assuming a spherical body with a geometric albedo of 0.04 and
a linear phase coefficient of 0.04 mag/deg for the R-band, we derived
an effective radius of 0.41±0.02 km. The light curve suggest that
we were seeing the varying cross-section of an elongated body and we
determined a = 0.57±0.08 km, b = c = 0.31 ±0.02 km, the minimum
axial ratio 1.8±0.3, and a rotational period of 3.7±0.2 hr. Its
color is characterized by (V-R) = 0.57±0.11 and (B-V) = 1.16±0.20,
slightly outside the main trend among cometary nuclei, but comparable
to a few of them. We were unable to detect any fragment in the vicinity
of the C fragment on our deep HST images. H.A.W. acknowledges support
by NASA through grant GO-10625 from the STScI, S.C.L. acknowledges
support from the UK Particle Physics and Astronomy Research Council,
and I.T. acknowledges support from CNRS, France.
---------------------------------------------------------
Title: Hubble Space Telescope Investigation of the Disintegration
of 73P/Schwassmann-Wachmann 3
Authors: Weaver, Harold A.; Lisse, C. M.; Mutchler, M. J.; Lamy, P.;
Toth, I.; Reach, W. T.
2006DPS....38.0602W Altcode: 2006BAAS...38..490W
Following reports of dramatic temporal variability of the B and G
fragments of 73P/Schwassmann-Wachmann 3 (73P/SW3) in early April 2006,
our team was awarded Director's Discretionary time on the Hubble Space
Telescope to investigate the continuing disintegration of the nuclei. We
observed the B fragment three different times (UT 2006 April 18.974,
19.773, and 20.773) and discovered a swarm of sub-fragments trailing
behind the principal nucleus, including some that were probably released
coincident with the brightness outbursts reported by ground-based
observers during the first few days of April. The single observation
of the G fragment (UT 2006 April 18.574) also showed a nearby swarm of
sub-fragments, including some that were probably released just a few
days prior to the Hubble observations. For both the B and G fragments,
the Hubble images provide information on the fragmentation history of
both nuclei during the preceding month, if not earlier. In contrast,
a single Hubble observation of the C fragment during this same period
(UT 2006 April 18.642) did not reveal any new sub-fragments, consistent
with the rather steady activity observed for the C fragment throughout
early-April by both ground-based facilities and another Hubble program
(Lamy et al.). We examine in detail the morphology and kinematics of
the continuing disintegration of the B and G fragments and compare the
Hubble results to those obtained from earlier and later observations
with the Spitzer Space Telescope to develop a more comprehensive
understanding of the nucleus disruption process. <P />Financial
support for this work was provided by NASA through grant GO-10992 from
the STScI.
---------------------------------------------------------
Title: Aphelion Observations of the Nucleus of Comet
67P/Churyumov-Gerasimenko: Target of ESA's Rosetta Comet Orbiter
Mission
Authors: Lowry, Stephen C.; Fitzsimmons, A.; Jorda, L.; Kaasalainen,
M.; Lamy, P.; Toth, I.
2006DPS....38.0801L Altcode: 2006BAAS...38..492L
Rosetta is ESA's new comet orbiter mission, launched in
March 2004 and currently en route to Jupiter-family comet
67P/Churyumov-Gerasimenko. The probe will rendezvous with the comet
in 2014 and remain in orbit around the nucleus for on-going detailed
physical and compositional analysis. Pre-encounter observations of
the target are important for characterization of the heliocentric
light-curve behaviour and the physical properties of the nucleus,
information that is critical for mission planning. We present our
latest results from detailed observations carried out when the comet
was near aphelion at a heliocentric distance of 5.6 AU. The comet was
also at opposition, with an average phase angle of just 0.46°. Three
nights of optical imaging data were taken with ESO's 3.5m NTT at
La Silla (Chile), between May 10-14, 2005. The data includes CCD
VRI-filter imaging taken with the EMMI instrument. The rotational
signature of the nucleus was clearly detected at all passbands with
no sign of resolved coma or dust trail. Full rotational light-curves
in all three passbands were obtained, allowing detailed inspection of
surface colours at all rotational phases. A Fourier analysis of the
R-filter light-curve gives a robust best-fit synodic rotation period
of 12.72 ± 0.05 hours. The observed brightness range of 0.38 ± 0.04
magnitudes implies a projected nucleus axial ratio of 1.42 ± 0.05. The
mean R-filter magnitude is 22.41 ± 0.03, which corresponds to mean
nucleus effective radius of 2.26 ± 0.03 km (assuming an albedo and
linear phase coefficient of 0.04). The projected semi-axial dimensions
are therefore 2.94 ± 0.15 and 2.07 ± 0.04 km. Our size is slightly
larger than a previous estimate [Lamy et al. 2003. BAAS 35, 970],
which implies a steep phase-darkening law or a more complex phase
function that includes an opposition-surge effect.
---------------------------------------------------------
Title: Understanding the Kreutz Sungrazing Comets
Authors: Knight, Matthew M.; A'Hearn, M. F.; Biesecker, D. A.; Faury,
G.; Hamilton, D. P.; Lamy, P.; Llebaria, A.
2006DPS....38.2002K Altcode: 2006BAAS...38..516K
We present updated results of our photometric study of the Kreutz
family comets observed by SOHO-LASCO. This is a continuation of earlier
work by Biesecker et al. (2002) and includes all Kreutz comets which
reached perihelion in the SOHO-LASCO field of view by the end of 2005,
a sample of over 900 comets. Typical Kreutz light curves brighten
at a relatively constant rate, reach a peak in brightness at 10-13
solar radii (prior to perihelion), then fade rapidly, with a small
subset displaying a second (smaller) peak in brightness inside of 6
solar radii. We are attempting to explain these light curve features
using physical models of the nucleus such as composition, density,
porosity, and production rates and will report on our findings. We are
also investigating the relationship between Kreutz comets and other
comets observed by SOHO-LASCO (the sungrazing families: Meyer, Marsden,
and Kracht, and other non-sungrazing comets) and with observations of
prominent sungrazers seen from the ground, e.g. Ikeya-Seki (1965 f),
to estimate production rates at larger heliocentric distances. From
these rates we hope to improve the scaling relationship between size
and apparent brightness and constrain the size distribution of the
Kreutz family. <P />This research was supported by NASA Planetary
Atmospheres grant NAG513295.
---------------------------------------------------------
Title: In situ dust measurements in the inner Saturnian system
Authors: Srama, R.; Kempf, S.; Moragas-Klostermeyer, G.; Helfert, S.;
Ahrens, T. J.; Altobelli, N.; Auer, S.; Beckmann, U.; Bradley, J. G.;
Burton, M.; Dikarev, V. V.; Economou, T.; Fechtig, H.; Green, S. F.;
Grande, M.; Havnes, O.; Hillier, J. K.; Horanyi, M.; Igenbergs, E.;
Jessberger, E. K.; Johnson, T. V.; Krüger, H.; Matt, G.; McBride, N.;
Mocker, A.; Lamy, P.; Linkert, D.; Linkert, G.; Lura, F.; McDonnell,
J. A. M.; Möhlmann, D.; Morfill, G. E.; Postberg, F.; Roy, M.;
Schwehm, G. H.; Spahn, F.; Svestka, J.; Tschernjawski, V.; Tuzzolino,
A. J.; Wäsch, R.; Grün, E.
2006P&SS...54..967S Altcode:
In July 2004 the Cassini-Huygens mission reached the Saturnian system
and started its orbital tour. A total of 75 orbits will be carried
out during the primary mission until August 2008. In these four years
Cassini crosses the ring plane 150 times and spends approx. 400 h
within Titan's orbit. The Cosmic Dust Analyser (CDA) onboard Cassini
characterises the dust environment with its extended E ring and
embedded moons. Here, we focus on the CDA results of the first year
and we present the Dust Analyser (DA) data within Titan's orbit. This
paper does investigate High Rate Detector data and dust composition
measurements. The authors focus on the analysis of impact rates, which
were strongly variable primarily due to changes of the spacecraft
pointing. An overview is given about the ring plane crossings and the
DA counter measurements. The DA dust impact rates are compared with
the DA boresight configuration around all ring plane crossings between
June 2004 and July 2005. Dust impacts were registered at altitudes
as high as 100 000 km above the ring plane at distances from Saturn
between 4 and 10 Saturn radii. In those regions the dust density of
particles bigger than 0.5μm can reach values of 0.001m<SUP>-3</SUP>.
---------------------------------------------------------
Title: On the mechanisms leading to orphan meteoroid streams
Authors: Vaubaillon, J.; Lamy, P.; Jorda, L.
2006MNRAS.370.1841V Altcode: 2006MNRAS.tmp..735V
We analyse several mechanisms capable of creating orphan meteoroid
streams (OMSs) for which a parent has not been identified. OMSs
have been observed as meteor showers since the XIXth century and by
the IRAS satellite in the 1980s. We find that the process of close
encounters with giant planets (particularly Jupiter) is the most
efficient mechanism to create them: only a limited section of the
stream is perturbed and follows the parent body on its new orbit,
while the majority of the meteoroids remain in their pre-encounter
orbit or in an intermediate state, breaking the link with their
parent body. Cometary non-gravitational forces can also contribute
to the process since they cause the comet to drift away from its
stream. However, they are not sufficient by themselves to produce an
OMS. Resonances can either split or confine a stream over a long time
(>1000 yr). Some meteoroid streams may look like OMSs since their
parent comet is dormant or not observable (e.g. long period). Even if
new techniques succeed in linking minor objects to meteoroid streams,
OMSs will still exist simply because cometary nuclei are subject to
complete disruption leading to their disappearance.
---------------------------------------------------------
Title: Analysis of Space Coronagraphic Images : Application to ten
years of SOHO/LASCO data
Authors: Burtin, M.; Llebaria, A.; Lamy, P.
2006ASPC..351..275B Altcode: 2006adass..15..275B
Since 1996, the LASCO (Large Angle and Spectrometric Coronagraph)
Coronagraphs of the ESA/NASA SOHO (Solar and Heliospheric
Observatory) mission have been providing the solar astronomical
and geophysical communities with an unprecedented view of the solar
corona. The photometric restitution of the huge amount of data is
of prime importance for understanding the physics of the corona,
its evolution over a solar cycle as well as its consequences on the
Earth environment, and represents a major challenge. The combination
of ground calibrations, continuous in-flight calibrations and the
implementation of novel procedures has been necessary to disentangle
the strong intercorrelation between many instrumental effects such
as vignetting, polarization, straylight, optical distortion and
timing. Geometricals parameters are extracted in a first pass. The
vignetting correction relies on a detailed model of the instrument
supplemented by a comparison with ground-based observations of the
inner corona during the 1998 total eclipse. The polarimetric response
based on the Mueller method was finely corrected thanks to polarized
images obtained during specific maneuvers of the SOHO spacecraft. The
straylight has been deduced on a yearly basis using the unpolarized
component extracted from polarization sequences. The photometric
calibration and its temporal evolution relies on several hundreds stars
observed over ten years of operation. We will describe the overall
software and database architectures of these calibration-pipeline
chains, and the final products made available on our LASCO website.
---------------------------------------------------------
Title: Magnetic Variability of the Streamer Belt
Authors: Saez, F.; Lamy, P.; Llebaria, A.
2006ESASP.617E..74S Altcode: 2006soho...17E..74S
No abstract at ADS
---------------------------------------------------------
Title: Interaction of CMEs with the Streamer Belt
Authors: Llebaria, A.; Saez, F; Lamy, P.; Robelus, S.; Boursier, Y.
2006ESASP.617E.135L Altcode: 2006soho...17E.135L
No abstract at ADS
---------------------------------------------------------
Title: The Marseille-Artemis Catalog of LASCO CMES
Authors: Boursier, Y.; Lamy, P.; Llebaria, A.; Robelus, S.
2006ESASP.617E.119B Altcode: 2006soho...17E.119B
No abstract at ADS
---------------------------------------------------------
Title: Formation flying applied to solar coronal diagnostics: the
ASPIICS coronagraph
Authors: Vivès, S.; Lamy, P.; Levacher, P.; Boit, J. L.; Saisse, M.
2006SPIE.6265E..24V Altcode: 2006SPIE.6265E..64V
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter
and the front objective. The diffraction fringe from the occulter
and the vignetted pupil which degrades the spatial resolution
prevent observing the inner corona inside typically 2-2.5 solar
radii. Formation flyers open new perspectives and allow to conceive
giant, externally-occulted coronagraphs using a two-component space
system with the external occulter on one spacecraft and the optical
instrument on the other spacecraft at approximately 100-150 m from
the first one. ASPIICS (Association de Satellites Pour l'Imagerie et
l'Interfromtrie de la Couronne Solaire) is a payload proposed to ESA
in the framework of the PROBA-3 mission of formation flyers presently
under study. ASPIICS is composed of a single coronagraph which performs
high spatial resolution imaging of the corona as well as 2-dimensional
spectroscopy of several emission lines (in particular the forbidden line
of Fe XIV at 530.285 nm) from the coronal base out to 3 solar radii (
R <SUB>solar</SUB>). Thus ASPIICS will address the main questions of
the coronal physics. The classical design of an externally occulted
coronagraph is adapted to the detection of the very inner corona as
close as 1.01 R <SUB>solar</SUB> and the addition of a Fabry-Perot
interferometer using a so-called etalon.
---------------------------------------------------------
Title: Survey of Ensemble Physical Properties of Cometary Nuclei
Authors: Fernandez, Yanga; A'Hearn, Michael; Bauer, James; Campins,
Humberto; Groussin, Olivier; Lamy, Philippe; Licandro, Javier; Lisse,
Carey; Lowry, Stephen; Meech, Karen; Reach, William; Toth, Imre;
Weaver, Harold
2006sptz.prop30908F Altcode:
We propose to make an albedo and radius survey of 100 cometary nuclei
using IRS PU and MIPS imaging. We focus on Jupiter family comets
(JFCs), which have dynamical and evolutionary connections to other
Solar System groups: transneptunian objects (TNOs), Centaurs, Trojan
asteroids, and extinct comet candidates. However, among these groups,
the nuclei of JFCs remain the _only_ group not yet the subject of a
detailed mid-infrared survey. Understanding the evolution of comets
since formation is crucial for unlocking their secrets about the
thermophysical and compositional environment of the protoplanetary
disk. An important way to do this is to study comparisons and contrasts
among comets, and between comets and related dynamical groups. To
this end, we propose a mid-IR survey of JFCs. Our scientific goals
are as follows. 1) Measure the thermal emission from the JFC nuclei
to calculate their effective radii. 2) Use complementary ground-based
visible-wavelength observations to derive the nuclei's geometric
albedos. Note that simultaneity for these observations is not needed. 3)
Compare the cometary albedo distribution with those of Centaurs, TNOs,
Trojans, and extinct comet candidates to gauge the effects of surface
evolution. The glaring albedo difference between TNOs and Centaurs
versus other groups needs to be explained. 4) Test for correlations
between cometary albedos and other properties of the nuclei, such
as composition and dynamical age. 5) Resolve once and for all the
long-standing question of just how safe it is to assume an albedo for
a cometary nucleus. 6) Use these radii to derive a completely new and
independent estimate of the current JFC size distribution that will
resolve the ongoing debate between several groups. The number of targets
in our sample is driven by the need to test recent indications that
the size distribution is truncated at radii smaller than 2 km. In such
a case, ours would be the definitive study of the JFC size distribution.
---------------------------------------------------------
Title: Photometric calibration of the LASCO-C2 coronagraph for Solar
System objects
Authors: Llebaria, A.; Lamy, P.; Danjard, J. -F.
2006Icar..182..281L Altcode:
We present a photometric calibration of the SOHO/LASCO-C2 coronagraph
appropriate to Solar System objects based on the extensive analysis
of all stars down to magnitude V=8 which transited its field-of-view
during the past nine years of operation (1996-2004). An automatic
procedure was developed to analyze some 143,000 images, and to detect,
locate and measure those stars. Aperture photometry was performed
using three different aperture sizes and the zero points of the
photometric transformations between the LASCO-C2 magnitudes for its
three filters (orange, blue and red) and the standard V magnitudes
were determined after introducing a correction for the color of the
stars. The calibration coefficients for the surface photometry of
extended sources were then derived from the zero points. An analysis of
their temporal evolution indicates a slight decrease of the sensitivity
of LASCO-C2 at a rate of ∼0.7% per year.
---------------------------------------------------------
Title: Calibration of the Soho/Lasco C3 White Light Coronagraph
Authors: Morrill, J. S.; Korendyke, C. M.; Brueckner, G. E.; Giovane,
F.; Howard, R. A.; Koomen, M.; Moses, D.; Plunkett, S. P.; Vourlidas,
A.; Esfandiari, E.; Rich, N.; Wang, D.; Thernisien, A. F.; Lamy, P.;
Llebaria, A.; Biesecker, D.; Michels, D.; Gong, Q.; Andrews, M.
2006SoPh..233..331M Altcode:
We present a detailed review of the calibration of the LASCO C3
coronagraph on the SOHO satellite. Most of the calibration has been
in place since early in the mission and has been utilized to varying
degrees as required by specific analysis efforts. However, using
observational data from the nearly decade-long database of LASCO images,
we have re-evaluated and improved many aspects of the calibration. This
includes the photometric calibration, vignetting function, geometric
distortion, stray light, and exposure and observation times. Using this
comprehensive set of corrections we have generated and made available a
set of calibrated coronal images along with a set of periodic background
images to ease the accessibility and use of the LASCO database.
---------------------------------------------------------
Title: 3D Simulations of the Solar Corona using Octree Compression
Authors: Saez, F.; Lamy, P.; Llebaria, A.
2006IAUS..233..236S Altcode:
We present a new powerful tool to simulate the streamer belt of the
solar corona based on forward modeling. It takes into account the
temporal evolution of the corona and provides both qualitative and
quantitative results. Starting from the National Solar Observatory
photospheric magnetograms, the position of the neutral line at the
source surface (2.5 Rsun) is caculated using the potential field source
surface model. The plasma sheet of the streamer belt is centered around
the current sheet represented as the radial extension of the neutral
line. The 3D electron density is represented with octree compression and
the radiance images are computed by a ray-tracing algorithm implementing
the Thomson scattering. A multi-octree method allows to simulate the
temporal evolution of the streamer belt and to compute the synoptic
maps from time-series of generated images. The comparison between the
synoptic maps of the streamer belt obtained with the SOHO/LASCO-C2
coronagraph and the simulated synoptic maps constructed from our model
shows a global agreement for both radiance profiles and global behaviour
of the streamer and confirms earlier findings by Wang et al. (1997) that
the streamers are associated with folds in the plasma sheet. However,
some features cannot be explained using this method and are interpreted
by introducing two types of large-scale structures. Our results suggest
that the potential field source surface model is not fully adequate
for the description of the fine structure of the streamer belt, even
during the time of low solar activity. We present new applications of
our method to future coronographic observations with SECCHI/COR-2 on
STEREO and SILC on Solar Orbiter.
---------------------------------------------------------
Title: ASPIICS, a giant externally occulted coronagraph for the
PROBA-3 formation flyer mission
Authors: Vivès, S.; Lamy, P.; Koutchmy, S.; Arnaud, J.
2006cosp...36.3063V Altcode: 2006cosp.meet.3063V
Formation flyers open new perspectives and allow to conceive giant
externally-occulted coronagraphs using a two-component space system with
the external occulter on one spacecraft and the optical instrument on
the other spacecraft at approximately 100 m from the first one ASPIICS
Association de Satellites Pour l Imagerie et l Interferometrie de la
Couronne Solaire is a mission proposed to ESA in the framework of the
PROBA-3 program of formation flyers which is presently in phase A to
exploit this technique for coronal observations ASPIICS is composed of
a single coronagraph which performs high spatial resolution imaging of
the corona as well as 2-dimensional spectroscopy of several emission
lines from the coronal base out to 3 Rs The selected lines allow to
address different coronal regions the forbidden line of FeXIV at 530
285 nm coronal matter Fe IX X at 637 4 nm coronal holes HeI at 587
6 cold matter An additional broad spectral channel will image the
white light corona and derive electron densities The classical design
of an externally occulted coronagraph is adapted to the detection
of the very inner corona as close as 1 01 Rs and the addition of
a Fabry-Perot interferometer using a so-called etalon ASPIICS will
address the question of the coronal heating and the role of waves by
characterizing propagating fluctuations waves and turbulence in the
solar wind acceleration region and by looking for oscillations in the
intensity and Doppler shift of spectral lines The combined imaging
and spectral diagnostics capabilities available with ASPIICS
---------------------------------------------------------
Title: A portrait of the nucleus of comet 67P/Churyumov-Gerasimenko,
the target of the Rosetta mission
Authors: Lamy, P.; Toth, I.; Jorda, L.; Lowry, S.; Gutierrez, P.;
Groussin, O.; Kaasalainen, M.
2006cosp...36.3366L Altcode: 2006cosp.meet.3366L
We present a detailed portrait of the nucleus of comet 67P
Churyumov-Gerasimenko based on observations performed with the Hubble
Space Telescope with the Spitzer Space Telescope and with the ESO New
Technology Telescope in Chili In all cases the observations extended
over several hours so that light curves could be secured Results will
encompass the size shape albedo and rotational state of the nucleus
of 67P as well as a 3D solution reconstruction of its shape resulting
from the inversion of the light curves
---------------------------------------------------------
Title: Properties of the DEEP IMPACT Dust Cloud
Authors: Jorda, L.; Lamy, P.; Faury, G.; Keller, H. -U.; Kueppers,
M.; Hviid, S.; Koschny, D.; Lecacheux, J.; Gutierrez, P.; Lara, L.
2006cosp...36.3223J Altcode: 2006cosp.meet.3223J
The OSIRIS Narrow Angle Camera aboard ROSETTA observed in the visible
the dust cloud created by the DEEP IMPACT impactor during more than
2 weeks Additional observations were also obtained at Pic du Midi
Observatory in the visible before and after the impact We compare the
acquired images with synthetic images resulting from a Monte-Carlo
simulation to compute the mass and the kinetic energy of the dust in
the cloud We also derive the size mass and velocity distributions
of the dust particles Our study is however restricted to submicron
particles which can be easily detected on our images
---------------------------------------------------------
Title: Electron density in polar and trans-equatorial coronal
holes. Implications for the solar wind
Authors: Lamy, P.; Saez, F.; Llebaria, A.
2006cosp...36.3338L Altcode: 2006cosp.meet.3338L
We present the final analysis of the polarized images of the solar
corona obtained with the LASCO-C2 coronagraph aboard SOHO over the
last 10 years The calibrated polarized radiance pB has been inverted to
produce 2-D maps of the electron density assuming either spherical or
cylindrical symmetry We concentrate here on polar and trans-equatorial
coronal holes We compare the measured profiles with those from models
and past observations We attempt to determine the lowest possible
density profile in a hole We finally discuss the implications of our
measurements for the properties of the solar wind
---------------------------------------------------------
Title: The Coronal Dynamics Imagers for the KUAFU mission
Authors: Vivès, S.; Lamy, P.; Rousset, G.; Boit, J. -L.
2006cosp...36.3054V Altcode: 2006cosp.meet.3054V
The Space Weather Explorer - KuaFu mission will provide simultaneous
long-term and synoptic observations of the complete chain of
disturbances from the solar atmosphere to the geospace KuaFu-A located
at the L1 liberation point includes Coronal Dynamics Imagers composed
of a Lyman-alpha coronagraph from 1 1 to 2 5 solar radii and a white
light coronagraph out to 15 solar radii in order to identify the
initial sources of Coronal Mass Ejections CMEs and their acceleration
profiles The difficulty of observing the lower corona should not be
underestimated since instrumental stray light remains a critical issue
in the visible because of the low contrast of the corona with respect
to the Sun Observing the corona in the Lyman-alpha line is a valid
alternative to white light observations The Lyman-alpha approach takes
advantage of both the intrinsic higher contrast of the corona wrt the
solar disk in this line compared to the visible and the absence of
F-corona at 121 6nm Furthermore it has been convincingly shown that
the coronal structures seen in Lyman-alpha correspond to those seen in
the visible and which result from Thomson scattering of the coronal
ionized gas This is because the plasma is still collisional in the
lower corona so that the hydrogen neutral atoms are coupled to the
protons A classical internally-occulted Lyot coronagraph is required
so as to preserve the image quality down to the inner limit of the
field of view Following the general concept of a Lyot coronagraph the
optical design uses only mirrors A narrow band interferential filter
---------------------------------------------------------
Title: Visible and infrared observations of Asteroid Steins, a target
of the Rosetta mission
Authors: Lamy, P.; Barucci, A.; Jorda, L.; Lowry, S.; Carvano, J.;
Fornasier, S.; Groussin, O.; Kaasalainen, M.
2006cosp...36.3351L Altcode: 2006cosp.meet.3351L
In 2008 the ROSETTA spacecraft will flyby asteroid 2867 Steins a small
main belt asteroid whose present knowledge is still very limited In
particular its albedo is unknown since it has never been observed in
the infrared Its rotational period of 6 06 -0 05 hours and light curve
amplitude of 0 2 mag have been recently determined but the orientation
of its spin axis is unknown In order to improve our knowledge of this
asteroid and prepare the flyby we have conducted a campaign of visible
measurements using ground-based telescopes and infrared measurements
using the SST Spitzer space telescope In all cases Steins has been
observed over several hours to secure rotational light curves in order
to rephase them for proper interpretation We will present our results
for the size shape albedo and rotational state of this asteroid as
well as a 3D solution reconstruction of its shape resulting from the
inversion of the light curves
---------------------------------------------------------
Title: Understanding the Kreutz sungrazing comets
Authors: Knight, M. M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.;
Hamilton, D. P.; Lamy, P.; Llebaria, A.
2006cosp...36.2697K Altcode: 2006cosp.meet.2697K
We present the results of our study of the Kreutz family comets
observed by SOHO-LASCO This is a continuation of earlier work by
Biesecker et al 2002 and includes all Kreutz comets which reached
perihelion in the SOHO-LASCO field of view by the end of 2005 a
sample of over 900 comets We use physical models of the nucleus such
as composition density porosity and production rates to explain the
characteristic features of Kreutz light curves notably the slope
of brightening the peak in brightness at 10-13 solar radii prior to
perihelion and the rapid fading interior to this The possibility that
there exists two distinct subgroups of Kreutz comets which reach peak
brightness at slightly different heliocentric distances is reexamined
and modeled We compare the Kreutz comets with other comets observed by
SOHO-LASCO the sungrazing families Meyer Marsden and Kracht and other
non-sungrazing comets and with observations of prominent sungrazers
seen from the ground e g C 1965 S1 Ikeya-Seki to estimate production
rates at larger heliocentric distances From these rates we improve the
scaling relationship between size and apparent brightness and constrain
the size distribution of the Kreutz family Finally we predict discovery
rates of Kreutz comets by the upcoming STEREO mission and ground-based
surveys such as Pan-STARRS This research was supported by NASA Planetary
Atmospheres grant NAG513295
---------------------------------------------------------
Title: 3-D simulations of the solar Corona for the STEREO and SOLAR
ORBITER missions
Authors: Saez, F.; Lamy, P.; Llebaria, A.
2006cosp...36.3344S Altcode: 2006cosp.meet.3344S
We present a new powerful tool based on a forward modeling method which
allows to simulate the streamer belt taking into account the temporal
evolution of the solar corona and which provides both qualitative and
quantitative results Starting from the NSO photospheric magnetograms the
position of the neutral line at the source surface 2 5 Rsun is caculated
using the potential field source surface model The plasma sheet of
the streamer belt is centered around the current sheet represented
as the radial extension of the neutral line The 3-D electron density
is represented with octree compression and the radiance images are
computed by a ray-tracing algorithm implementing the Thomson scattering
A multi-octree method permits to simulate the temporal evolution of
the streamer belt This method has now been generalized to hanble the
plumes and the coronal mass ejections and is well adapted to multi-views
of the corona such as will be offered by the STEREO mission and to
out-of-ecliptic views that SOLAR ORBITER will achieve We will present
synthetic images as expected from the coronagraphs of these missions
---------------------------------------------------------
Title: The Lyman Alpha Imaging-Monitor Experiment (LAIME) for
TESIS/CORONAS-PHOTON
Authors: Damé, L.; Koutchmy, S.; Kuzin, S.; Lamy, P.; Malherbe,
J. -M.; Noëns, J. -C.
2006cosp...36.3524D Altcode: 2006cosp.meet.3524D
LAIME the Lyman Alpha Imaging-Monitor Experiment is a remarkably
simple no mechanisms and compact 100x100x400 mm full Sun imager to be
flown with TESIS on the CORONAS-PHOTON mission launch expected before
mid-2008 As such it will be the only true chromospheric imager to be
flown in the next years supporting TESIS EUV-XUV imaging SDO and the
Belgian LYRA Lyman Alpha flux monitor on the ESA PROBA-2 microsatellite
launch expected in September 2007 We will give a short description
of this unique O60 mm aperture imaging telescope dedicated to the
investigating of the magnetic sources of solar variability in the UV and
chromospheric and coronal disruptive events rapid waves Moreton waves
disparitions brusques of prominences filaments eruptions and CMEs onset
The resolution pixel is 2 7 arcsec the field of view 1 4 solar radius
and the acquisition cadence could be as high as 1 image minute The back
thinned E2V CCD in the focal plane is using frame transfer to avoid
shutter and mechanisms Further more the double Lyman Alpha filtering
allows a 40 AA FWHM bandwidth and excellent rejection yet providing
a vacuum seal design of the telescope MgF2 entrance window Structural
stability of the telescope focal length 1 m is preserved by a 4-INVAR
bars design with Aluminium compensation in a large pm 10 o around 20 o
---------------------------------------------------------
Title: Combined Visible Observations Of Comet 9P/Tempel 1 During
The Deep Impact Event From Pic du Midi Observatory And With The
ROSETTA/OSIRIS Narrow Angle Camera
Authors: Jorda, L.; Lamy, P. L.; Faury, G.; Gutierrez, P.; Keller,
H. -U.; Kueppers, M.; Lecacheux, J.; Colas, F.; Hviid, S.; Lara,
L. M.; OSIRIS Team
2005DPS....37.4414J Altcode: 2005BAAS...37.1568J
We observed comet 9P/Tempel 1 before and after the impact in the visible
from the Earth with the 1-m telescope at Pic du Midi Observatory
and with the narrow angle camera (OSIRIS/NAC) aboard the ROSETTA
spacecraft. The latter observations allowed an uninterrupted monitoring
from 120 hrs pre-impact to 250 hrs post-impact, but at a low spatial
resolution (1 pixel projected to 1500 km at the comet). The former
observations offered a less extensive temporal coverage (about 3 hrs
per night from June 25 to July 7) but at a higher spatial resolution
(1 pixel projected to 600 km at the comet). The angle of 27 degrees
between the two lines-of-sight further allowed to follow the same event
from two different viewing angles. We present a combined preliminary
analysis of the images obtained with both instruments. The dust
production rate is monitored via two proxies, the [Afrho] parameter
and the dust cross section, which is more appropriate in the case of a
non-canonic coma. This indicates that the comet went back to its normal,
pre-impact state within about 7 days of the impact thus showing that
it did not create a detectable active region. Dust structures were
found and followed in the coma and in the dust tail and we discuss
their significance. Several spectral analysis of the pre-impact light
curve reveal a periodic variation attributed to the rotation of the
nucleus with a period of about 41 hrs.
---------------------------------------------------------
Title: The rotational state of the nucleus of comet 9P/Tempel 1
Authors: Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Weaver, H. A.
2005DPS....37.4411L Altcode: 2005BAAS...37Q1568L
The nucleus of comet 9P/Tempel 1 was observed with the Hubble Space
Telescope Advanced Camera for Surveys (HST/ACS) in May 2004, in an
effort to pin down its rotational period and assist in the preparation
of the operations of the Deep Impact mission. The observations were
performed from May 7.9 to 9.5, 2004, and extended over a 39-hour
period. At the mid-point of the observing window, the comet was 3.52
AU from the Sun , 4.03 AU from the Earth and at a phase angle of 13.5
deg. The program consisted in 18 separate visits, each one corresponding
to an HST orbit and including 3 identical exposures of 857 sec duration
with the F606W broadband filter. These very deep exposures revealed a
point-source object, albeit the nucleus, without any coma. Photometry
was performed by PSF fitting, the required (model) PSFs being generated
with the TinyTim software. The mean V magnitude of the nucleus was
21.85 and had an amplitude of 0.45 mag indicating that we were seeing
the varying cross-section of a rotating, elongated body. There is a
very clear asymmetry between the two half-periods of the light curve
with one minimum being much deeper than the other. The periodicity was
analyzed with six different techniques yielding a rotational period in
the range 38.32 to 42.68 hr, and resulting in a mean value of 41.0 hr.
---------------------------------------------------------
Title: The colors of cometary nuclei and other primitive bodies
Authors: Toth, I.; Lamy, P. L.
2005DPS....37.1617T Altcode: 2005BAAS...37.1563T
Primitive minor objects like Kuiper-belt objects (KBOs), Centaurs,
cometary nuclei and low-albedo asteroids contain a considerable
amount of information regarding the formation of early solar system
planetesimals and some of the primordial processes. Broadband colors
by themselves offer limited insight into surface composition but
correlations either between different color indices or with other
(e.g., orbital) parameters can shed some light on the questions of
the composition and the evolution of the minor objects. Furthermore,
a systematic comparison of the color indices of various populations may
provide clues on their relationships, and concur along with dynamical
studies, to establish a scenario of their formation and evolution in the
solar system. We present new color results on cometary nuclei obtained
with the Hubble Space Telescope (HST) whose superior resolution enables
us to accurately isolate the nucleus signals from the surrounding
comae. By combining with scrutinized available data obtained with
ground-based telescopes, we accumulated a sample of 39 cometary nuclei,
34 ecliptic comets (ECs) and 5 nearly-isotropic comets (NICs) using
the nomenclature of Levison (1996). We analyze color distributions and
color-color correlations as well as correlations with other physical
parameters. We present our own compilation of colors of 282 objects in
the outer solar system, separately considering the different dynamical
populations, classical KBOs in low and high-inclination orbits,
resonant KBOs (practically Plutinos), scattered-disk objects (SDOs)
and Centaurs. We perform a systematic analysis of color distributions
of all plausible parent-child combinations and conclude by synthesizing
the implications of the colors for the origin of ecliptic comets. <P
/>We acknowledge the support of the French "Programme National de
Planétologie", jointly funded by CNRS and CNES, and of the bilateral
French--Hungarian cooperation program. I. Toth further acknowledges
the support of the Université de Provence, of the Hungarian Academy
of Sciences through grant No. 9871.
---------------------------------------------------------
Title: Hubble Space Telescope observations of the nucleus fragment
73P/Schwassmann Wachmann 3-C
Authors: Toth, I.; Lamy, P.; Weaver, H. A.
2005Icar..178..235T Altcode:
The investigation of fragmented comets provides information on the
physical properties and internal structure of cometary nuclei, as well
as insights into the mechanisms responsible for cometary breakups. The
Jupiter-family Comet 73P/Schwassmann-Wachmann 3 (73P/SW3) fragmented
non-tidally into at least four components, and probably more, in the
autumn of 1995. Fragment C was detected with the Wide Field Planetary
Camera 2 (WFPC2) of the Hubble Space Telescope (HST) on 26 November
2001 when it was 3.26 AU from the Sun and 2.34 AU from the Earth. The
high spatial resolution of the HST allowed us to separate the signal of
the fragment from that of its coma, and to determine its R magnitude in
the Johnson-Kron-Cousins photometric system from four images taken with
the F675W filter. Assuming a spherical body with a geometric albedo
of 0.04 and a linear phase coefficient of 0.04 mag deg <SUP>-1</SUP>
for the R band, we derived an effective radius of 0.68±0.04km. The
pre-breakup radius of the original nucleus was estimated to be 1.1 km,
which implies that the volume of fragment C is ∼25% of the total
volume of the pre-breakup nucleus. The limited temporal coverage of
our observations preclude deriving an accurate shape or rotational
period; our measurements are consistent with a rather spherical body
but an elongated shape cannot be excluded. Fragment C was very active
despite its rather large heliocentric distance, with an estimated dust
production rate of ∼1.5kgs (∼130 metric tons day <SUP>-1</SUP>). A
very large fraction of the surface area of fragment C must have been
sublimating to sustain such a high level of activity. Fragment C may
be recovered at its next return in 2006, if it does not experience
further fragmentation.
---------------------------------------------------------
Title: On the 3-dimensional structure of the streamer belt of the
solar corona
Authors: Saez, F.; Zhukov, A. N.; Lamy, P.; Llebaria, A.
2005A&A...442..351S Altcode:
We investigate the three-dimensional structure of the streamer belt
of the solar corona using a model that allows us to simulate its
quasi-stationary configuration. Starting from the National Solar
Observatory photospheric magnetograms, the position of the neutral
line at the source surface (2.5 ~R_⊙) is determined using the
potential field source surface model. A plasma sheet is centered
around the current sheet represented as the radial extension of
the neutral line. Comparing the synoptic maps of the streamer belt
obtained with the SOHO/LASCO-C2 coronagraph and the simulated synoptic
maps constructed from our model of the warped plasma sheet, we confirm
earlier findings by Wang et al. (1997, ApJ, 485, 875; Wang et al. 2000,
Geophys. Res. Lett., 27, 149) that the streamers are associated with
folds in the plasma sheet. Although the large-scale structure of the
streamer belt is described reasonably well, some features, however,
cannot be explained in this framework. We propose that two types of
large-scale structures take part in the formation of these additional
features. The first one is an additional fold of the neutral line, which
does not appear in the modeled source surface neutral line, but is well
visible in photospheric magnetograms. The second one is a plasma sheet
with a ramification in the form of a secondary short plasma sheet. We
show that these structures better describe the observed configurations
of the streamer belt. The secondary plasma sheet can be formed between
two secondary current sheets connected to the main current sheet. Our
results suggest that the potential field source surface model is
not fully adequate for the description of the fine structure of the
streamer belt, even during the time of low solar activity.
---------------------------------------------------------
Title: A large dust/ice ratio in the nucleus of comet 9P/Tempel 1
Authors: Küppers, Michael; Bertini, Ivano; Fornasier, Sonia;
Gutierrez, Pedro J.; Hviid, Stubbe F.; Jorda, Laurent; Keller,
Horst Uwe; Knollenberg, Jörg; Koschny, Detlef; Kramm, Rainer; Lara,
Luisa-Maria; Sierks, Holger; Thomas, Nicolas; Barbieri, Cesare; Lamy,
Philippe; Rickman, Hans; Rodrigo, Rafael; A'Hearn, M. F.; Angrilli,
F.; Bailey, M.; Barthol, P.; Barucci, M. A.; Bertaux, J. -L.; Burns,
J. A.; Cremonese, G.; Curdt, W.; De Cecco, M.; Debei, S.; Fulle, M.;
Gliem, F.; Ip, W. H.; Huhrt, E.; Llebaria, A.; Lopez Moreno, J. J.;
Marzari, F.; Naletto, G.; Sabau, L.; Sanz Andres, A.; Sivan, J. P.;
Tondello, G.; Wenzel, K. -P.
2005Natur.437..987K Altcode:
Comets spend most of their life in a low-temperature environment
far from the Sun. They are therefore relatively unprocessed and
maintain information about the formation conditions of the planetary
system, but the structure and composition of their nuclei are poorly
understood. Although in situ and remote measurements have derived
the global properties of some cometary nuclei, little is known about
their interiors. The Deep Impact mission shot a projectile into comet
9P/Tempel 1 in order to investigate its interior. Here we report the
water vapour content (1.5 × 10<SUP>32</SUP> water molecules or 4.5 ×
10<SUP>6</SUP>kg) and the cross-section of the dust (330km<SUP>2</SUP>
assuming an albedo of 0.1) created by the impact. The corresponding
dust/ice mass ratio is probably larger than one, suggesting that
comets are `icy dirtballs' rather than `dirty snowballs' as commonly
believed. High dust velocities (between 110ms<SUP>-1</SUP> and
300ms<SUP>-1</SUP>) imply acceleration in the comet's coma, probably
by water molecules sublimated by solar radiation. We did not find
evidence of enhanced activity of 9P/Tempel 1 in the days after the
impact, suggesting that in general impacts of meteoroids are not the
cause of cometary outbursts.
---------------------------------------------------------
Title: Deep Impact Observations by OSIRIS Onboard the Rosetta
Spacecraft
Authors: Keller, Horst Uwe; Jorda, Laurent; Küppers, Michael;
Gutierrez, Pedro J.; Hviid, Stubbe F.; Knollenberg, Jörg; Lara,
Luisa-Maria; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rickman,
Hans; Rodrigo, Rafael
2005Sci...310..281K Altcode:
The OSIRIS cameras (optical, spectroscopic, and infrared remote imaging
system) onboard the European Space Agency's Rosetta spacecraft observed
comet 9P/Tempel 1 for 17 days continuously around the time of NASA's
Deep Impact mission. The cyanide-to-water production ratio was slightly
enhanced in the impact cloud, compared with that of normal comet
activity. Dust particles were flowing outward in the coma at >160
meters per second, accelerated by the gas. The slope of the brightness
increase showed a dip about 200 seconds after the impact. Dust Afρ
values before and long after the impact confirm the slight decrease of
cometary activity. The dust-to-water mass ratio was much larger than 1.
---------------------------------------------------------
Title: Outgassing-induced effects in the rotational state of comet
67P/Churyumov—Gerasimenko during the Rosetta mission
Authors: Gutiérrez, Pedro J.; Jorda, Laurent; Samarasinha, Nalin H.;
Lamy, Philippe
2005P&SS...53.1135G Altcode:
The new target of the Rosetta mission is comet 67P/Churyumov-Gerasimenko
(hereafter 67P/C-G). In order to support the planning of the mission,
in particular the strategy during the mapping and landing phases, we
have performed numerical simulations of the rotational evolution of a
comet in the orbit of 67P/C-G. In these simulations, the currently known
observational constraints have been taken into account and a large set
of initial conditions were considered. For most of the simulations,
we observe that the sublimation-induced torques produce significant
changes in the rotational parameters of a 67P/C-G-like comet. Typical
rates of change for the spin period from the rendezvous up to the
end of the nominal mission range from 0.001 to 0.05hday<SUP>-1</SUP>
depending on different circumstances as described in the text. At
perihelion, rates of change of the orientation of the angular momentum
vector amount to about 0.01- 0.1degday<SUP>-1</SUP>. These simulations
suggest that a specific strategy should be defined in order to monitor
likely variations of the rotational parameters. As an example we
show a possible optimized schedule for observations with the OSIRIS
instrument to determine the rotational parameters of comet 67P/C-G
and their possible evolution.
---------------------------------------------------------
Title: Formation flyers applied to solar coronal observations:
the ASPICS mission
Authors: Vives, S.; Lamy, P.; Auchere, F.; Vial, J. -C.; Koutchmy,
S.; Arnaud, J.; Prado, J. -Y.; Frassetto, F.; Naletto, G.
2005SPIE.5901..305V Altcode:
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and the
vignetted pupil which degrades the spatial resolution prevent observing
the inner corona inside typically 2-2.5 solar radii. Formation flyers
open new perspectives and allow to conceive giant, externally-occulted
coronagraphs using a two-component space system with the external
occulter on one spacecraft and the optical instrument on the
other spacecraft at approximately 100 m from the first one. ASPICS
(Association de Satellites Pour l'Imagerie Coronographique Solaire)
is a mission proposed to CNES in the framework of their demonstration
program of formation flyers which is presently under study to exploit
this technique for coronal observations. In the baseline concept,
ASPICS includes three coronagraphs operating in three spectral
domains: the visible continuum (K-corona brightness), the HI Lyman
alpha emission line at 121.6 nm, and the HeII emission line at 30.4
nm. Their unvignetted fields of view extend from 1.1 to 3.2 solar radii
with a typical spatial resolution of 3 arcsec. In order to connect
coronal activity to photospheric events, ASPICS further includes
two disk imagers. The first one is devoted to the HI Lyman alpha
emission line. The second one is a multi-channel instrument similar to
SOHO/EIT and devoted to the HeII (30.4 nm), FeIX/X (17.1 nm) and FeXII
(19.5 nm) emission lines. Two concepts of the space system are under
consideration: a symmetric configuration where the disk imagers and
the external occulter are on one spacecraft and the coronagraphs on
the other, an asymmetric configuration where the external occulter is
on one spacecraft and the scientific instruments are regrouped on the
other one.
---------------------------------------------------------
Title: Possible optical design for ASPICS, a formation-flyer solar
coronagraph for close-limb visible and Lyman-α imaging of the corona
Authors: Frassetto, Fabio; Naletto, Giampiero; Vives, Sebastien;
Lamy, Philippe
2005SPIE.5901..316F Altcode:
The recent possibility of deploying clusters of satellites in
flight formation allows the development of a new generation of
space instruments, and among them, of externally occulted solar
coronagraphs. This can be implemented by introducing a large occulter
on a first satellite, and all the remaining optical system on a second
satellite, located in the shadow of the occulter. Since the capability
of looking close to the solar limb is directly related to the distance
between the external occulter and the coronagraphic objective, formation
flyers offer the capability of a major improvement in observing the
lower corona from space. In this paper, we describe a possible optical
design for ASPICS, a formation flyer solar coronagraph composed of
two satellites separated by about 100 m. The proposed dual channel
design will allow for the first time to simultaneously observe the
lower and intermediate corona in both visible and ultraviolet (HI
Lyman-α line) spectral regions at a 6 arcsec/pixel scale factor with
a single instrument.
---------------------------------------------------------
Title: Concept of formation flyer for the ASPICS solar coronagraphic
mission
Authors: Leyre, Xavier; Sghedoni, M.; Vives, S.; Lamy, P.; Pailharey,
E.
2005SPIE.5899..221L Altcode:
This paper describes a concept of a formation flyer for ASPICS
(Association de Satellites Pour l'Imagerie et la Coronagraphie
Solaire), a giant 100 m based, externally occulted coronagraph aimed
at observing the inner corona (and the solar disk) in the visible and
ultra-violet. The two-satellite formation approach, based on existing
space systems, is composed of a Myriade micro-satellite supporting
the occulter and a Proteus platform as the main system carrying the
coronagraph and imager scientific instruments. Both spacecrafts are
launched as a single composite and deployed once on orbit, preferably
a 3-day orbit or at the L1 Lagrange point. The coronagraph satellite
acts as the "master" and provides the main functions of the mission
(data handling, communication, propulsion, Guidance Navigation and
control) while the Myriade acts as the "slave". The control of the
formation is performed in two steps: i) RF metrology for deployment
and preliminary pointing, ii) classical optical attitude sensors and
metrology based on diverging laser beams. This will insure the nominal
requirement of a lateral positioning with an accuracy of 1 mm and a
longitudinal positioning with an accuracy of 500 mm.
---------------------------------------------------------
Title: Light Curves of Kreutz Comets
Authors: Knight, M. M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.;
Hamilton, D. P.; Lamy, P.; Llebaria, A.
2005DPS....37.1103K Altcode: 2005BAAS...37Q.632K
We present the results of our study of the light curves of the Kreutz
family comets observed by SOHO-LASCO. This is a continuation of the
earlier work by Biesecker et al. (2002) and includes all Kreutz comets
which reached perihelion in the SOHO-LASCO field of view by the end of
2003, a sample of more than 600 comets. We do not see the bimodality
of the light curves found by Biesecker et al., however we find that
the brightest comets increase in brightness more rapidly and fade more
slowly than fainter comets. To test if the slope of the brightening seen
at the small heliocentric distances observed by SOHO-LASCO (inside 0.14
AU) extends to larger distances (1-3 AU), we imaged fields statistically
likely to contain Kreutz comets prior to their entering the SOHO-LASCO
field of view using the Kitt Peak National Observatory 4-m telescope
with the MOSAIC wide-field imager in January 2005. No comets were
discovered in these fields, however they will be searched again using
the ephemerides of all Kreutz comets that reach perihelion in the
SOHO-LASCO field of view during May and June 2005, since some of these
comets should have been in the observed fields. This will allow us to
set constraints on the rate of brightening at heliocentric distances
beyond the SOHO-LASCO field of view. <P />This work is supported by
the NASA Planetary Atmospheres Program under grant NAG513295.
---------------------------------------------------------
Title: Automatic detection of coronal mass ejections on LASCO-C2
synoptic maps
Authors: Boursier, Yannick; Llebaria, Antoine; Goudail, Francois;
Lamy, Philippe; Robelus, Sebastien
2005SPIE.5901...13B Altcode:
The LASCO-C2 coronagraph on-board the SOHO solar observatory has
been providing a continuous flow of coronal images for the past nine
years. Synoptic maps for each Carrington rotation have been constructed
from these images and offer a global view of the temporal evolution
of the solar corona, particularly the occurrence of transient events
such as the coronal mass ejections (CMEs), an important component of
space weather activity. CMEs present distinct signatures on synoptic
maps offering a novel approach to the problem of their statistical
detection. We are presently testing several techniques of automatic
detection based on their morphological properties. The basic procedure
involves three steps: i) morphological characterization, ii) definition
and application of adapted filters (optimal trade-off filters, Canny
filter,...), iii) segmentation of the filtered synoptic maps. At this
stage, the CMEs are detected. The efficiency of the detection of the
various filters is estimated using the ROC curves. On-going studies
include the classification of CMEs based on their physical properties,
the determination of their velocities, and the question of their
connection to the streamer belt.
---------------------------------------------------------
Title: Characterization of Asteroids 2867 Steins and 21 Lutetia,
Targets of the Rosetta Mission
Authors: Lamy, Philippe; Barucci, Antonella; Carvano, Jorge;
Cruikshank, Dale; Dotto, Elisabetta; Fornasier, Sonia; Fulchignoni,
Marcello; Groussin, Olivier; Jorda, Laurent; Migliorini, Alessandra
2005sptz.prop20653L Altcode:
Asteroids 2867 Steins and 21 Lutetia are the new targets of the
Rosetta mission. Our present knowledge of these two objects is still
very limited. Their albedos are either unknown (Steins) or subject
to question (Lutetia), with severe consequences for their sizes and
their taxonomic classifications and their surface compositions are
either unclear or controversial. We propose to investigate the physical
properties (size, shape), the surface and thermal properties (albedo,
thermal inertia, surface roughness) and surface composition of these
two asteroids by taking advantage of the capabilities and performances
of the Spitzer Space Telescope (SST), supplemented by ground-based
observations. The SST observations consist in taking low resolution
spectra with the IRS instrument over its full wavelength range 5-38
micron. Each asteroid will be observed 14 times at time intervals of
30 min for Steins and 40 mn for Lutetia in order to properly sample
their light curve. The detailed knowledge of these asteroids that
will result from our proposed program will be of critical importance
for optimizing the flyby strategy of the Rosetta spacecraft and the
operation of its instruments. They will later supplement the in-situ
observations necessarily limited by the conditions of a fast flyby
and contribute to their global characterization.
---------------------------------------------------------
Title: A Multiwavelength Investigation of Comet 73P/SW3-C
Authors: Lamy, Philippe; Weaver, Harold; Jorda, Laurent; A'Hearn,
Michael; Toth, Imre; Groussin, Olivier; Kaasalainen, Mikko; Lowry,
Stephem
2005sptz.prop20001L Altcode:
The nucleus of comet 73P/Schwassmann-Wachmann-3 experienced a non-tidal
breakup in late 1995. The largest fragment (73P/SW3-C) survived
its subsequent perihelion passage in 2001 and will return in 2006,
when it will pass very close to (0.08AU) Earth. This represents an
outstanding opportunity to characterize a fresh cometary nucleus,
and we propose an intensive investigation using both the Hubble
and Spitzer telescopes. Employing the technique that our group has
developed over the past decade to characterize 31 cometary nuclei, we
will use HST/ACS to photometrically resolve the nucleus of 73P/SW3-C
at optical wavelengths and SST/MIPS to do the same thing at thermal
infrared wavelengths, thereby allowing us to determine both the size
and albedo of this fragment. We also plan to measure the lightcurve
of 73P/SW3-C to obtain detailed shape information, and use HST/NICMOS
to probe the composition, in particular to search for evidence of icy
material on the fresh surface. Previous observations indicate that
most of the remaining mass of 73P/SW3 is in the form of numerous small
fragments. A few of those may have been captured by the C fragment,
and the determination of their orbits would allow the first, direct
measurement of the mass of a cometary nucleus. Thus, we will also
perform a deep search for any possible companions to the C-fragment.
---------------------------------------------------------
Title: Deep Impact: Working Properties for the Target Nucleus Comet
9P/Tempel 1
Authors: Belton, Michael J. S.; Meech, Karen J.; A'Hearn, Michael F.;
Groussin, Olivier; McFadden, Lucy; Lisse, Carey; Fernández, Yanga R.;
Pittichová, Jana; Hsieh, Henry; Kissel, Jochen; Klaasen, Kenneth;
Lamy, Philippe; Prialnik, Dina; Sunshine, Jessica; Thomas, Peter;
Toth, Imre
2005SSRv..117..137B Altcode:
In 1998, Comet 9P/Tempel 1 was chosen as the target of the Deep Impact
mission (A’Hearn, M. F., Belton, M. J. S., and Delamere, A., Space
Sci. Rev., 2005) even though very little was known about its physical
properties. Efforts were immediately begun to improve this situation by
the Deep Impact Science Team leading to the founding of a worldwide
observing campaign (Meech et al., Space Sci. Rev., 2005a). This
campaign has already produced a great deal of information on the global
properties of the comet’s nucleus (summarized in Table I) that is
vital to the planning and the assessment of the chances of success at
the impact and encounter. Since the mission was begun the successful
encounters of the Deep Space 1 spacecraft at Comet 19P/Borrelly and
the Stardust spacecraft at Comet 81P/Wild 2 have occurred yielding
new information on the state of the nuclei of these two comets. This
information, together with earlier results on the nucleus of comet
1P/Halley from the European Space Agency’s Giotto, the Soviet Vega
mission, and various ground-based observational and theoretical studies,
is used as a basis for conjectures on the morphological, geological,
mechanical, and compositional properties of the surface and subsurface
that Deep Impact may find at 9P/Tempel 1. We adopt the following
working values (circa December 2004) for the nucleus parameters of
prime importance to Deep Impact as follows: mean effective radius =
3.25± 0.2 km, shape irregular triaxial ellipsoid with a/b = 3.2±
0.4 and overall dimensions of ∼14.4 × 4.4 × 4.4 km, principal axis
rotation with period = 41.85± 0.1 hr, pole directions (RA, Dec, J2000)
= 46± 10, 73± 10 deg (Pole 1) or 287± 14, 16.5± 10 deg (Pole 2)
(the two poles are photometrically, but not geometrically, equivalent),
Kron-Cousins (V-R) color = 0.56± 0.02, V-band geometric albedo =
0.04± 0.01, R-band geometric albedo = 0.05± 0.01, R-band H(1,1,0)
= 14.441± 0.067, and mass ∼7×10<SUP>13</SUP> kg assuming a bulk
density of 500 kg m<SUP>-3</SUP>. As these are working values, {i.e.},
based on preliminary analyses, it is expected that adjustments to
their values may be made before encounter as improved estimates become
available through further analysis of the large database being made
available by the Deep Impact observing campaign. Given the parameters
listed above the impact will occur in an environment where the local
gravity is estimated at 0.027 0.04 cm s<SUP>-2</SUP> and the escape
velocity between 1.4 and 2 m s<SUP>-1</SUP>. For both of the rotation
poles found here, the Deep Impact spacecraft on approach to encounter
will find the rotation axis close to the plane of the sky (aspect
angles 82.2 and 69.7 deg. for pole 1 and 2, respectively). However,
until the rotation period estimate is substantially improved, it will
remain uncertain whether the impactor will collide with the broadside
or the ends of the nucleus.
---------------------------------------------------------
Title: UVCS Observation of Sungrazer C/2001 C2: Possible Comet
Fragmentation and Plasma-Dust Interactions
Authors: Bemporad, A.; Poletto, G.; Raymond, J. C.; Biesecker, D. A.;
Marsden, B.; Lamy, P.; Ko, Y. -K.; Uzzo, M.
2005ApJ...620..523B Altcode:
In this paper we analyze SOHO Ultraviolet Coronagraph Spectrometer
(UVCS) observations of the sungrazing comet C/2001 C2, a member of the
Kreutz family, observed on 2001 February 7 at heliocentric distances
of 4.98 and 3.60 R<SUB>solar</SUB>. This comet apparently went through
sequential fragmentation events along its path: further indication of
fragmentation processes is provided by UVCS observations, which show
the presence of two separate tails in the 4.98 R<SUB>solar</SUB> data
set, which we interpret as two fragments unresolved by LASCO images,
one of which sublimates before reaching 3.60 R<SUB>solar</SUB>. The
cometary hydrogen Lyα signal, decaying exponentially with time,
has been interpreted in terms of the H<SUB>2</SUB>O outgassing rate
and the interactions of coronal protons with atoms created by the
photodissociation of water. However, one of the fragments shows an
additional Lyα contribution, constant with time, which adds to the
temporally decaying signal. This contribution has been ascribed to
the sublimation of pyroxene dust grains, whose end products neutralize
coronal protons via charge exchange processes. Hence, the two fragments
have different composition; differences throughout the comet body may
have been the primary cause for the comet fragmentation.
---------------------------------------------------------
Title: The SIde-Looking Coronagraph for the solar orbiter mission:
Optical and mechanical designs
Authors: Vivès, S.; Lamy, P.; Guitton, J.; Boit, J. L.; Dargent, P.
2005AdSpR..36.1406V Altcode:
The SIde-Looking Coronagraph (SILC) is intented to be proposed as
part of the payload of the Solar Orbiter mission of the European
Space Agency. Solar Orbiter will follow elliptic orbits with a large
range of heliocentric distance, from 0.21 to 0.6 AU, and will reach
heliographic latitudes as high as 38°. Furthermore, the spacecraft
will have an offset pointing capability so as to target any point
of the solar disk. These characteristics, in addition to the severe
thermal environment, are very restrictive for a coronagraph and lead
us to propose an externally occulted coronagraph entirely protected
from direct sunlight by remaining in the shadow of the spacecraft and
looking sideways. The optical design follows the general principles
of an externally occulted coronagraph adapted to the side-looking
concept. Although SILC loses the full spatial coverage of the corona,
it can observe the inner part of the corona (down to 1.5 solar radii)
during the whole mission and compensate the off-pointing of the
spacecraft. The optical and mechanical designs of SILC are presented
in detail.
---------------------------------------------------------
Title: Meteoroid Streams Associated to Comets 9P/Tempel 1 and
67P/Churyumov-Gerasimenko
Authors: Vaubaillon, J.; Lamy, P.; Jorda, L.
2004EM&P...95...75V Altcode: 2005EM&P...95...75V
The meteoroid streams associated to short-period comets
9P/Tempel 1 (the target of the Deep Impact mission)<SUP>.</SUP>
and 67P/Churyumov-Gerasimenko (the target of the Rosetta mission)
are studied. Their structure is overwhelmingly under the control of
Jupiter and repeated relatively close encounters cause a reversal of
the direction of the spatial distribution of the stream relative to the
comet* an initial stream trailing the comet as usually seen eventually
collapses, becomes a new stream leading the comet and even splits into
several components. Although these two comets do not produce meteor
showers on Earth, this above feature shows that meteor storms can
occur several years before the perihelion passage of a parent body.
---------------------------------------------------------
Title: Physical Properties of the Deep Impact Target Comet 9P/Tempel
1 from Spitzer and Hubble Space Telescope Observations
Authors: Lisse, C. M.; A'Hearn, M. F.; Belton, M. J. S.; Fernandez,
Y. R.; Groussin, O.; Lamy, P.; Meech, K. J.; Toth, I.; Weaver, H. A.
2004DPS....36.3402L Altcode: 2004BAAS...36Q1148L
Comet 9P/Tempel 1 is the target of the Deep Impact mission to
be launched at the end of this year. Accurate knowledge of the
physical properties of the comet's nucleus is important for mission
success. Current published size estimates for the nucleus are uncertain
by 50% [Fernandez et al. 2003] and the current best rotational solutions
have periods of 22 and 42 hours [Belton and Meech, 2004]. <P />In
Spring 2004, with the comet outside the ice line and inactive and
inbound on the final leg before the DI encounter, we obtained 12
spectrophotometric (7.5-40 microns) visits of the nucleus with the
Spitzer Space Telescope over a 40 hour period in March 2004, and 18
photometric (F606) visits over a 42 hour period in May 2004 with the
Hubble Space Telescope. Collating these observations into lightcurves,
we have applied rotational and thermal models [Belton et al. 2005,
Groussin et al. 2004] to derive values for the effective radius,
axial ratio, pole position, bulk surface albedo, active surface area,
and thermal inertia. Initial analysis of the observations has yielded a
nucleus with an average radius of about 3 km, an axial ratio of about 3,
a geometric albedo of about 4%, and an active surface fraction of about
8%. The thermal inertia is low, similar to that of other primitive
bodies. The rotation pole orientation's J2000 RA and Dec are either
(99<SUP>o</SUP>,-19<SUP>o</SUP>) or (60<SUP>o</SUP>,+72<SUP>o</SUP>)
, with an error of about 4 degrees. We present the latest results of
our observations and analysis here.
---------------------------------------------------------
Title: The Cassini Cosmic Dust Analyzer
Authors: Srama, R.; Ahrens, T. J.; Altobelli, N.; Auer, S.; Bradley,
J. G.; Burton, M.; Dikarev, V. V.; Economou, T.; Fechtig, H.; Görlich,
M.; Grande, M.; Graps, A.; Grün, E.; Havnes, O.; Helfert, S.; Horanyi,
M.; Igenbergs, E.; Jessberger, E. K.; Johnson, T. V.; Kempf, S.;
Krivov, A. V.; Krüger, H.; Mocker-Ahlreep, A.; Moragas-Klostermeyer,
G.; Lamy, P.; Landgraf, M.; Linkert, D.; Linkert, G.; Lura, F.;
McDonnell, J. A. M.; Möhlmann, D.; Morfill, G. E.; Müller, M.;
Roy, M.; Schäfer, G.; Schlotzhauer, G.; Schwehm, G. H.; Spahn, F.;
Stübig, M.; Svestka, J.; Tschernjawski, V.; Tuzzolino, A. J.; Wäsch,
R.; Zook, H. A.
2004SSRv..114..465S Altcode:
The Cassini-Huygens Cosmic Dust Analyzer (CDA) is intended to
provide direct observations of dust grains with masses between
10<SUP>-19</SUP> and 10<SUP>-9</SUP> kg in interplanetary space and
in the jovian and saturnian systems, to investigate their physical,
chemical and dynamical properties as functions of the distances
to the Sun, to Jupiter and to Saturn and its satellites and rings,
to study their interaction with the saturnian rings, satellites and
magnetosphere. Chemical composition of interplanetary meteoroids will
be compared with asteroidal and cometary dust, as well as with Saturn
dust, ejecta from rings and satellites. Ring and satellites phenomena
which might be effects of meteoroid impacts will be compared with the
interplanetary dust environment. Electrical charges of particulate
matter in the magnetosphere and its consequences will be studied,
e.g. the effects of the ambient plasma and the magnetic field on the
trajectories of dust particles as well as fragmentation of particles
due to electrostatic disruption.
---------------------------------------------------------
Title: The Side-Looking Coronagraph (SILC) for the Solar Orbiter
mission: optical performances
Authors: Vivès, Sébastien; Lamy, Philippe
2004ESASP.554..381V Altcode: 2004icso.conf..381V
The SIde-Looking Coronagraph (SILC) is one of the solar remote-sensing
instruments proposed for the payload of the Solar Orbiter mission
(European Space Agency, ESA). The specificities of the Solar Orbiter
mission are very restrictive for a coronagraph: large range of
heliocentric distance from 0.21 to 0.6 AU, offset pointing capability
of the spacecraft, severe thermal environment of limited mass and
volume available. To cope with them, we propose an externally occulted
coronagraph entirely protected from direct sunlight by remaining in
the shadow of the spacecraft and looking sideways. The optical design
follows the general principles of an externally-occulted coronagraph
adapted to the side-looking concept. The performances and the expected
stray light level will be presented here together with their evolution
as function of the heliocentric distance.
---------------------------------------------------------
Title: The August 11th, 1999 CME
Authors: Koutchmy, S.; Baudin, F.; Bocchialini, K.; Daniel, J. -Y.;
Delaboudinière, J. -P.; Golub, L.; Lamy, P.; Adjabshirizadeh, A.
2004A&A...420..709K Altcode:
We present here a set of observations, space borne and ground based,
at different wavelengths, of the solar corona at and after the time of
the total solar eclipse of August 11{th}. It is used to consider some
unusual features of the coronal dynamics related to a limb Coronal Mass
Ejection (CME) observed after the total eclipse. The complementary
aspect of simultaneous ground-based and space-borne observations
of the corona is used to produce an accurate composite image of the
White Light (W-L) corona before the CME. A high arch system (possibly
a dome-like structure, with large cavities inside but without a cusp
further out) which appeared on the eclipse W-L images, is suggested to
be a large-scale precursor of the CME, well preceding the eruption of
the top part of the brightest prominence recorded in W-L. This bright
prominence is shown as a filament in absorption using the Transition
Region And Corona Explorer (TRACE) images taken in different coronal
lines. The analysis of the images of the Large Angle and Spectrometric
Coronograph (LASCO) on board the Solar and Heliospheric Observatory
(SoHO), showing the progression of the CME, is discussed in an attempt
to make a connection with the surface event. A SoHO-EIT (Extreme
UV Imager Telescope) image sequence details the prominence eruption
and shows the sudden heating processes of the ejected parts. We found
that there is no reason to assume that the huge cavity is significantly
destabilised well before the eruption of the upper part of the low-lying
bright twisted filament which coincides with the position of one of
the legs of the high arch. Observations are still compatible with the
assumption of both the break-out model and of the flux rope erupting
model as a result of a shear or of an increasing poloıdal magnetic
flux from below. We stress the possible role of buoyancy of the giant
cavity as a destabilizing factor leading to the CME, noticing that some
motion of coronal material back toward the surface can be seen during at
least the first phase of the CME, from both EIT and LASCO observations.
---------------------------------------------------------
Title: Preliminary calibration results of the wide angle camera of
the imaging instrument OSIRIS for the Rosetta mission
Authors: da Deppo, V.; Naletto, G.; Nicolosi, P.; Zambolin, P.; de
Cecco, M.; Debei, S.; Parzianello, G.; Ramous, P.; Zaccariotto, M.;
Fornasier, S.; Verani, S.; Thomas, N.; Barthol, P.; Hviid, S. F.;
Sebastian, I.; Meller, R.; Sierks, H.; Keller, H. U.; Barbieri, C.;
Angrilli, F.; Lamy, P.; Rodrigo, R.; Rickman, H.; Wenzel, K. P.
2004ESASP.554..191D Altcode: 2004icso.conf..191D
Rosetta is one of the cornerstone missions of the European Space Agency
for having a rendezvous with the comet 67P/Churyumov-Gerasimenko
in 2014. The imaging instrument on board the satellite is OSIRIS
(Optical, Spectroscopic and Infrared Remote Imaging System), a
cooperation among several European institutes, which consists of
two cameras: a Narrow (NAC) and a Wide Angle Camera (WAC). The WAC
optical design is an innovative one: it adopts an all reflecting,
unvignetted and unobstructed two mirror configuration which allows
to cover a 12°x12° field of view with an F/5.6 aperture and gives
a nominal contrast ratio of about 10<SUP>-4</SUP>. The flight model
of this camera has been successfully integrated and tested in our
laboratories, and finally has been integrated on the satellite which
is now waiting to be launched in February 2004. In this paper we are
going to describe the optical characteristics of the camera, and to
summarize the results so far obtained with the preliminary calibration
data. The analysis of the optical performance of this model shows a
good agreement between theoretical performance and experimental results.
---------------------------------------------------------
Title: The nuclei of comets 126P/IRAS and 103P/Hartley 2
Authors: Groussin, O.; Lamy, P.; Jorda, L.; Toth, I.
2004A&A...419..375G Altcode:
We report the detection of the nucleus of 126P/IRAS and 103P/Hartley
2 with the Infrared Camera of the Infrared Space Observatory
(ISOCAM). 126P/IRAS was observed on 12 November 1996, when it was at
r_h=1.71 AU from the Sun and Δ=1.32 AU from the Earth. 103P/Hartley
2 was observed on 5 February 1998, when it was at r_h=1.21 AU from the
Sun and Δ=0.91 AU from the Earth. The observations were performed with
the broadband LW10 filter centered at 11.5 μm. The spatial resolution
was adequate to separate the thermal emission of the nuclei from
that of their respective comae. We combined the ISOCAM observations
with measured water production rates, using a model that considers
a spherical nucleus with a macroscopic mosaic of small and numerous
active and inactive regions, and we derived a radius of 1.57±0.14 km
and an active fraction at perihelion of 0.11±0.03 for 126P/IRAS, and
a radius of 0.71±0.13 km and an active fraction of ∼1 at perihelion
and 0.30±0.11 at 1.11 AU post-perihelion for 103P/Hartley 2. These
two examples illustrate the large diversity of activity pattern that
exists among cometary nuclei. <P />Based on observations made with the
Infrared Space Observatory, an ESA project with instruments funded
by ESA Member States (especially the PI countries: France, Germany,
The Netherlands and UK) and with the participation of ISAS and NASA.
---------------------------------------------------------
Title: Lessons learned from the SOHO/LASCO-C2 calibration
Authors: Llebaria, Antoine; Lamy, Philippe L.; Bout, Maurice V.
2004SPIE.5171...26L Altcode:
The LASCO-C2 coronagraph onboard the SOHO solar probe have been
providing for the last seven years an unprecedented long sequence
of coronal images at high cadence (about 75 images/day). The LASCO-C2
calibrations included the determination of the geometric characteristics
(attitude, distortion) as well as the photometric and photopolarimetric
responses. Such calibrations needed resort to a complementary set
of approaches including optical-modelling, pre-flight measures and
in-orbit measures and monitoring. In this paper we discuss about the
specific contribution of each of them, the example of radiometric
calibration of LASCO-C2 is dominated by the strong vignetting induced
by the occultors. The occultors fully mask the extended circular area
centered on the Sun image. Due to operational constraints the vignetting
function has been obtained using a complementary set of approaches:
1) ray tracing, 2) the geometric convolution of diaphragms, 3) the
measure of uniform sources in laboratory, 4) the measures in orbit
of the stars and F-corona. Finaly the relationship of radiometry
with geometric calibrations, strylight calibration and the log term
stability monitoring is discussed.
---------------------------------------------------------
Title: Optical design of the Lyman alpha coronagraph for the LYOT
microsatellite
Authors: Vives, Sebastien; Lamy, Philippe L.; Vial, Jean-Claude
2004SPIE.5171..298V Altcode:
The LYOT (LYman Orbiting Telescope) solar mission (proposed for a CNES
micro-satellite) is composed of a disk imager and a coronagraph, both
working at Lyman-α (121.6 nm). The coronagraph is internally occulted
and all-reflective with a field-of-view of 1.2 R up to 2.5 R and high
spatial resolution (2 pixels) amounts to 5 arcsec. The optical design
is driven by the requirement to use a superpolished spherical mirror
to minimize the scattered light into the instrument. The LYOT mission
will observe the Lyman-α corona at high cadence (1 image/5 minutes)
over a period of two years.
---------------------------------------------------------
Title: Visible, externally occulted coronagraph for Solar Orbiter
Authors: Vives, Sebastien; Lamy, Philippe L.; Korendyke, Clarence
2004SPIE.5171..131V Altcode:
The SIde-Looking Coronagraph (SILC) is one of the solar remote-sensing
instruments proposed for the payload of the Solar Orbiter mission. The
Solar Orbiter is a mission selected in September 2000 by the European
Space Agency (ESA) for the definition study phase. The Solar Orbiter
will describe elliptic orbits with a large range of heliocentric
distance, from 0.21 to 0.6 AU (astronomical units), that is a factor
3 for the geometric conditions and will reach heliographic latitudes
as high as 38 degrees. Furthermore, the spacecraft will have offset
pointing capability so as to target any point of the solar disk. These
constraints (in addition to the severe thermal environment) lead
us to propose an externally occulted coronagraph entirely protected
from direct sunlight by remaining in the shadow of the spacecraft and
looking sideways. The optical design follows the general principles
of an externally-occulted coronagraph adapted to the side-looking
concept. Although SILC loses the full spatial coverage of the corona, it
can observe the inner part of the corona (down to 1.5R) during the whole
mission and compensate the off-pointing of the spacecraft in the two
directions. The performances, resulting from ray-tracing calculations,
are presented here together with the expected stray light level.
---------------------------------------------------------
Title: Measuring the Size and Shape of Comet
67P/Churyumov-Gerasimenko, the Target of the Rosetta Mission
Authors: Lamy, Philippe
2004sptz.prop..222L Altcode:
In support of the Rosetta mission, we request Director's Discretionary
time to measure the size and shape of its target, the nucleus of
comet 67P/Churyumov-Gerasimenko. A safe landing of the Lander package
on its surface remains critically dependent upon its size which
is not unambiguoulsy determined from visible photometry because of
the uncertainty on its albedo. On the contrary, measurements of the
thermal emission of the nucleus will allow a direct determination
of its size. Observations with the Spitzer Space Telescope in late
February 2004 will provide the best possible data thanks to very
favourable observing conditions. We propose to use MIPS to image the
nucleus at 24 microns seventeen times, over a time interval of 12.5
hr to as to cover the full light curve of the nucleus and derive both
its size and shape. Complementary observations at 70 microns will help
constraining its SED and the thermal model to interpret the data. By
further combining with past HST observations, the rotational state
of the nucleus will be better con strained and the albedo will be
determined thus allowing to characterize its surface.
---------------------------------------------------------
Title: The sizes, shapes, albedos, and colors of cometary nuclei
Authors: Lamy, P. L.; Toth, I.; Fernandez, Y. R.; Weaver, H. A.
2004come.book..223L Altcode:
We critically review the data on the sizes, shapes, albedos, and
colors of cometary nuclei. Reliable sizes have been determined for
65 ecliptic comets (ECs) and 13 nearly isotropic comets (NICs). The
effective radii fall in the range 0.2-15 km for the ECs and 1.6-37
km for the NICs. We note that several nuclei recently measured by the
Hubble Space Telescope are subkilometer in radius, and that only 5 of
the 65 well-measured EC nuclei have effective radii larger than 5 km. We
estimate that the cumulative size distribution (CSD) of the ECs obeys a
single power law with an exponent qS = 1.9 ± 0.3 down to a radius of
~1.6 km. Below this value there is an apparent deficiency of nuclei,
possibly owing to observational bias and/or mass loss. When augmented
by 21 near-Earth objects (NEOs) that are thought to be extinct ECs,
the CSD flattens to qS = 1.6 ± 0.2. The cumulative size distribution
of NICs remains ill-defined because of the limited statistical basis
compared to ECs. The axial ratios a/b of the measured nuclei of ECs have
a median value of ~1.5 and rarely exceed a value of 2, although it must
be noted that the observed a/b values are often lower limits because
of uncertainties in the aspect angle. The range of rotational periods
extends from 5 to 70 h. The lower limit is significantly larger than
that of main-belt asteroids and NEOs (~2.2 h, excluding the monolithic
fast rotators), and this has implications for the bulk density of
cometary nuclei. By combining rotation and shape data when available,
we find a lower limit of 0.6 g cm-3 for the nucleus bulk density to
ensure stability against centrifugal disruption. Cometary nuclei are
very dark objects with globally averaged albedos falling within a
very restricted range: 0.02-0.06, and possibly even narrower. (B-V),
(V-R), and (R-I) color indices indicate that, on average, the color
of cometary nuclei is redder than the color of the Sun. There is,
however, a large diversity of colors, ranging from slightly blue to
very red. While two comets have well-characterized phase functions with
a slope of 0.04 mag deg-1, there is evidence for steeper (2P/Encke,
48P/Johnson) and shallower (28P/Neujmin 1) functions, so that the
observed range is 0.025-0.06 mag deg-1. The study of the physical
properties of cometary nuclei is still in its infancy, with many
unresolved issues, but significant progress is expected in the near
future from current and new facilities, both groundbased and spaceborne.
---------------------------------------------------------
Title: Solar Cycle Variation of the Radiance and the Global Electronic
Content of the Solar Corona
Authors: Lamy, P.; Llebaria, A.; Quemerais, E.
2004cosp...35.1876L Altcode: 2004cosp.meet.1876L
The question of the global activity of the solar corona, as a function
of time and distance from the center of the Sun, is considered by
analyzing SOHO/LASCO-C2 images over more than eight years, thus
covering a large part of solar cycle 23. The polarized images are
first analyzed to construct a photometric model of the F-corona wich
reflects its annual variations resulting from geometric effects and
of the instrumental straylight. Synoptic maps of the radiance of the
K-corona are created at different distances between 2.7 and 6.5 solar
radii. In order to conveniently quantify its temporal variation, the
radiance is integrated first globally and then in zones of different
latitudes to separate the equatorial and the polar regions. A similar
analysis is performed with the electronic density obtained by the
inversion of the polarized brightness assuming either a spherical or a
cylindrical model of the corona. Both the radiance and the electronic
density strongly vary with solar activity but the equatorial and polar
regions exhibit different behaviours. These variations are compared
with other indices of solar activity.
---------------------------------------------------------
Title: Dust Near The Sun
Authors: Mann, Ingrid; Kimura, Hiroshi; Biesecker, Douglas A.;
Tsurutani, Bruce T.; Grün, Eberhard; McKibben, R. Bruce; Liou,
Jer-Chyi; MacQueen, Robert M.; Mukai, Tadashi; Guhathakurta, Madhulika;
Lamy, Philippe
2004SSRv..110..269M Altcode:
We review the current knowledge and understanding of dust in the inner
solar system. The major sources of the dust population in the inner
solar system are comets and asteroids, but the relative contributions
of these sources are not quantified. The production processes inward
from 1 AU are: Poynting-Robertson deceleration of particles outside of
1 AU, fragmentation into dust due to particle-particle collisions,
and direct dust production from comets. The loss processes are:
dust collisional fragmentation, sublimation, radiation pressure
acceleration, sputtering, and rotational bursting. These loss processes
as well as dust surface processes release dust compounds in the
ambient interplanetary medium. Between 1 and 0.1 AU the dust number
densities and fluxes can be described by inward extrapolation of 1
AU measurements, assuming radial dependences that describe particles
in close to circular orbits. Observations have confirmed the general
accuracy of these assumptions for regions within 30° latitude of the
ecliptic plane. The dust densities are considerably lower above the
solar poles but Lorentz forces can lift particles of sizes < 5 μm
to high latitudes and produce a random distribution of small grains
that varies with the solar magnetic field. Also long-period comets
are a source of out-of-ecliptic particles. Under present conditions
no prominent dust ring exists near the Sun. We discuss the recent
observations of sungrazing comets. Future in-situ experiments should
measure the complex dynamics of small dust particles, identify the
contribution of cometary dust to the inner-solar-system dust cloud, and
determine dust interactions in the ambient interplanetary medium. The
combination of in-situ dust measurements with particle and field
measurements is recommended.
---------------------------------------------------------
Title: Properties of the nuclei of Centaurs Chiron and Chariklo
Authors: Groussin, O.; Lamy, P.; Jorda, L.
2004A&A...413.1163G Altcode:
We analyze visible, infrared, radio and spectroscopic observations of
2060 Chiron in a synthetic way to determine the physical properties of
its nucleus. From visible observations performed from 1969 to 2001,
we determine an absolute V magnitude for the nucleus of 7.28±0.08
with an amplitude of 0.16±0.03, implying a nearly spherical nucleus
with a ratio of semi-axes a/b=1.16±0.03. Infrared observations at 25,
60, 100 and 160 μm (i.e., covering the broad maximum of the spectral
energy distribution) obtained with the Infrared Space Observatory
Photometer (ISOPHOT) in June 1996 when Chiron was near its perihelion
are analyzed with a thermal model which considers an intimate mixture
of water ice and refractory materials and includes heat conduction
into the interior of the nucleus. We find a very low thermal inertia
of 3<SUP>+5</SUP><SUB>-3</SUB> J K<SUP>-1</SUP> m<SUP>-2</SUP>
s<SUP>-1/2</SUP> and a radius of 71±5 km. Combining the visible and
infrared observations, we derive a geometric albedo of 0.11±0.02. We
find that the observed spectra of Chiron can be fitted by a mixture
of water ice (∼30%) and refractory (∼ 70%) grains, and that this
surface model has a geometric albedo consistent with the above value. We
also analyze the visible, infrared and radio observations of Chariklo
(1997 CU26) and derive a radius of 118±6 km, a geometric albedo
of 0.07±0.01 and a thermal inertia of 0<SUP>+2</SUP><SUB>-0</SUB>
J K<SUP>-1</SUP> m<SUP>-2</SUP> s<SUP>-1/2</SUP>. A mixture of water
ice (∼ 20%) and refractory (∼ 80%) grains is compatible with the
near-infrared spectrum and the above albedo.
---------------------------------------------------------
Title: Rotational Properties of Deep Impact Target Comet 9P/Tempel 1
Authors: Lisse, C. M.; Groussin, O.; A'Hearn, M. F.; Weaver, H. A.;
Lamy, P.; Meech, K. J.; Belton, M. J. S.; Fernandez, Y. R.; Toth, I.
2004cosp...35.3161L Altcode: 2004cosp.meet.3161L
Comet 9P/Tempel 1 is the target of the Deep Impact mission to be
launched at the end of this year. To improve our understanding of
the rotational properties of the Tempel 1 nucleus [e.g., the current
rotational period solutions are 22 and 42 hours with an axial ratio
> 2.5 :1 (Belton and Meech, 2004)], we performed 12 spectroscopic
(7.5-40 microns) observations of the nucleus with the Spitzer Space
Telescope over a 42 hour period in March 2004, and 18 photometric (F606)
observations over a 42 hour period in May 2004 with the Hubble Space
Telescope. Ground based optical observations of the lightcurve were
also obtained during these times, in order to establish the albedo and
inter-phase the results. We present here the lightcurve results, and
the most likely solution for the rotational periodicity. We also discuss
the axial ratio of the body as estimated from the lightcurve amplitudes.
---------------------------------------------------------
Title: Visible and thermal infrared observations of the nucleus of
comet 67P/Churyumov-Gerasimenko
Authors: Lamy, P. L.; Jorda, L.; Toth, I.; Weaver, H. A.; Cruikshank,
D.; Fernandez, Y.
2004cosp...35.1824L Altcode: 2004cosp.meet.1824L
The nucleus of comet 67P/Churyumov-Gerasimenko was first unambiguously
detected in the visible with the planetary camera of the Hubble Space
Telescope in early March 2003 (Lamy, P.L. et al., BAAS 35, 970). By
observing the comet over 21 hours, the rotational period was found
to be 12.3 hr and assuming an albedo of 0.04, a radius of 2 km was
determined. It will be further observed in the thermal infrared with
the Spitzer Space Telescope in late February 2004 at a heliocentric
distance of 4.5 AU where it is presumed to be inactive. The nucleus will
be imaged with the multiband imaging photometer (MIPS) at 24 microns
seventeen times, over a time interval of 12.5 hr to as to cover the
full light curve. The infared flux will give directly access to its
size. By further combining with past HST observations, the rotational
state of the nucleus will be better constrained and the albedo will
be determined thus allowing to characterize its surface.
---------------------------------------------------------
Title: Approach to 3-D reconstruction of the solar corona from
STEREO observations
Authors: Portier-Fozzani, F.; Lamy, P.; Llebaria, A.
2004cosp...35.3977P Altcode: 2004cosp.meet.3977P
In this poster, we present the work that we planned to do at the
Laboratoire d'Astrophysique de Marseille concerning 3D reconstructions
for the mission STEREO. Getting 3D informations from a large
images database could be sometimes very puzzling while it requires
3D inversions together with image analysis decomposition. From
coronagraphic data, Vibert et al., 1997, used octree methods to
rebuilt the neutral sheet of the solar corona. The octree method
helps to reorganize a large number of data to be used by tomographic
method. More recently, Portier-Fozzani and Inhester (SOLSPA 2001)
proposed to reconstruct the solar corona in EUV by stereoscopic methods
in using the solar cycle for improving the decomposition into structures
to reconstruct. Portier-Fozzani, Bijaoui et al. (2002, 2004) used
the Multiscale Vision Model based on spatial wavelets decomposition,
to define in their image pair, groups of sub-objects, which are needed
for the matching step in stereovision. We derive here how we can use
these approaches for a full automatic reconstruction depending of the
solar cycle.
---------------------------------------------------------
Title: Three-dimensional Model of the Streamer Belt over Solar
Cycle 23
Authors: Saez, F.; Llebaria, A.; Lamy, P.
2004cosp...35.1854S Altcode: 2004cosp.meet.1854S
White-light images of the corona obtained with the SOHO/LASCO-C2
coronagraph over more than 8 years reveal the dramatic changes
of the structure and radiance distribution of the streamer belt
from the minimum to the maximum of the present solar cycle. While
it is qualitatively understood that the widening of the belt is
a consequence of the tilting and warpening of the plasma current
sheet, no quantitative study has been performed to derive physical
parameters from these images. Our approach consists in reproducing the
widening of the streamer belt and its periodic evolution with the solar
rotation with a model combining a layer of plasma centered around the
heliospheric current sheet and isolated streamers associated to active
regions. We first determine the neutral sheet from solar photospheric
magnetograms. Next, we introduce a parametric description of the
electronic density in streamers and construct its octree representation
based on a non-uniform sampling of the 3D space. The synthesized images
are generated using a ray-tracing algorithm which calculates the
Thomson scattering through the octree. Finally, we present a method
that allows to simulate the time evolution of the coronal magnetic
field during a Carrington rotation. The comparaison between the model
and the LASCO-C2 observations is performed on synoptic maps, to offer
a global view of the evolution of the corona, and on radiance profiles
to assess the quantitative agreement.
---------------------------------------------------------
Title: The SIde-Looking Coronagraph (SILC) for the Solar Orbiter
mission
Authors: Vives, S.; Lamy, P.; Korendyke, C.
2004cosp...35..951V Altcode: 2004cosp.meet..951V
The SIde-Looking Coronagraph (SILC) is one of the solar remote-sensing
instruments proposed for the payload of the Solar Orbiter mission
(European Space Agency, ESA). The Solar Orbiter will describe elliptic
orbits with a large range of heliocentric distance, from 0.21 to
0.6 AU, that is a factor 3 for the geometric conditions, and will
reach heliographic latitudes as high as 38 degrees. Furthermore, the
spacecraft will have offset pointing capability so as to target any
point of the solar disk. These specificities (in addition to the severe
thermal environment) are very restrictive for a coronagraph and lead
us to propose an externally occulted coronagraph entirely protected
from direct sunlight by remaining in the shadow of the spacecraft and
looking sideways. The optical design follows the general principles
of an externally-occulted coronagraph adapted to the side-looking
concept. Although SILC loses the full spatial coverage of the corona,
it can observe the inner part of the corona (down to 1.5 solar radii)
during the whole mission and compensate the off-pointing of the
spacecraft in the two directions. The performances, resulting from
ray-tracing calculations, will be presented together with the first
measurements of the stray light level.
---------------------------------------------------------
Title: Activity on the surface of the nucleus of comet 46P/Wirtanen
Authors: Groussin, O.; Lamy, P.
2003A&A...412..879G Altcode:
We present a thermal model of the nucleus of comet 46P/Wirtanen,
constrained by the temporal variations of the water production rate,
in order to understand the activity on its surface. We consider a
spherical nucleus with a macroscopic mosaic of small and numerous
active and inactive regions. At heliocentric distances r<SUB>h</SUB>
> 1.5 AU, the active regions represent 5-15% of the surface. At ~
1.5 AU, a rapid increase takes place and the active fraction reaches
70 to 100% in about 10 days, and then remains approximately constant up
to perihelion where Q<SUB>H_2O</SUB>=1.3+/-0.3*E<SUP>28</SUP> molecule
s<SUP>-1</SUP>. Post-perihelion, this fraction returns to ~ 10%. The
model is consistent with a geometric albedo <=0.06. A refractory
crust likely forms post-perihelion and can explain the variations of
the activity over an orbit. Finally, we derived an erosion of ~ 0.5
m per revolution and a remaining lifetime for the nucleus of several
hundred revolutions.
---------------------------------------------------------
Title: Long term evolution of cometary nuclei - Application to
46P/Wirtanen
Authors: Groussin, O.; Lamy, P.; Valsecchi, G.; Gonczi, R.
2003DPS....35.3828G Altcode: 2003BAAS...35Q1488G
We present a new method to study the long term evolution of cometary
nuclei in order to retrieve their original size. We consider first the
case of comet 46P/Wirtanen (the former target of the Rosetta mission)
and we calculate the past evolution of its orbital elements over
10<SUP>5</SUP> years, with and without non-gravitational forces. The
chaotic behaviour is simulated by considering 9 different values of
the initial mean anomaly. For an homogeneous nucleus with a composition
of 50% water ice + 50% dust and a density of 500 kg/m<SUP>3</SUP>, we
obtain an initial radius in the range 1.4-7.8 km, depending upon the
inital conditions. This result also depends upon the composition and
the density, but not on the presence, or not, of the non-gravitational
forces. We will apply this method to many other cometary nuclei in
the future.
---------------------------------------------------------
Title: LASCO C2 and C3 Level-1 Images: Calibration and Pipeline
Processing
Authors: Thernisien, A. F.; Morrill, J.; Llebaria, A.; Rich, N.;
Vourlidas, A.; Esfandiari, E.; Wang, D.; Korendyke, C.; Moses, D.;
Biesecker, D.; Bout, M.; Lamy, P.; Howard, R. A.
2003AGUFMSH41B0461T Altcode:
The LASCO C2 and C3 coronagraphs have provided coronal observations
since May, 1996. Initial calibrations have been available during most
of this time period. We have subsequently completed a re-evaluation
and refinement of these calibration procedures. We are now able
to present the final version of the level-1 data using the latest
improvements from in-flight calibration results. Further details
on the LASCO calibration and level-1 data access are presented at
http://lasco-www.nrl.navy.mil/level_1/lascocal_index.html. In this
presentation we will sum up the different aspects of the LASCO
C2-C3 image corrections such as vignetting, absolute photometry,
time corrections, geometric distortion, sun center position, and
spacecraft orientation.
---------------------------------------------------------
Title: New spin period determination for comet 6P/d'Arrest
Authors: Gutiérrez, P. J.; de León, J.; Jorda, L.; Licandro, J.;
Lara, L. M.; Lamy, P.
2003A&A...407L..37G Altcode:
A lightcurve of comet 6P/d'Arrest from R-band CCD images taken at
La Palma 2.52 m NOT telescope is presented. The lightcurve shows
noticeable periodic changes in brightness produced by rotational
modulation. The periodogram analysis of the lightcurve shows a peak with
a confidence level exceeding 99.9% at 3.336 h. Assuming an elongated
nucleus, the most likely spin period is therefore 6.67 +/- 0.03 h,
but other periodicities are also possible. The peak to peak amplitude
is 0.082 +/- 0.016 mag. This period, and the other peaks detected in
the periodogram, are not commensurable with previous estimates of the
spin period of comet 6P/d'Arrest. If all the measurements are correct,
the differences between this estimate and the previous ones could be
due to a possible change in the spin period of comet 6P/d'Arrest or
to this comet being rotating in a complex mode.
---------------------------------------------------------
Title: Outgassing-induced effects in the rotational state of comet
67P/Churyumov-Gerasimenko during the Rosetta mission.
Authors: Gutierrez, P. J.; Jorda, L.; Samarasinha, N. H.; Lamy, P.
2003DPS....35.3802G Altcode: 2003BAAS...35..984G
Comet 67P/Churyumov-Gerasimenko [hereafter 67P/C-G] is the new main
target of the Rosetta mission (a cornerstone mission in ESA's "Horizon
2000" program). The Rosetta spacecraft will orbit comet 67P/C-G for
almost one year in 2015, and a module will land on its surface. In order
to ensure the correct interpretation of the measurements taken by the
instruments onboard the spacecraft and to help in the definition of
an appropriate landing strategy, we carry out numerical simulations of
the evolution of the rotational state of this comet under the effects
of the sublimation-induced torque from the currrent epoch to the end of
the Rosetta mission. In the simulations, we will take into account the
known observational constraints on the nucleus size and the spin period
and consider a range of scenarios: two thermophysical models, several
densities, three initial angular momentum orientations, several activity
patterns on the surface, and two initial rotational states. We will
present our initial results including the typical changes in the angular
momentum orientation and the spin period during the operational phase.
---------------------------------------------------------
Title: SOHO/LASCO observation of an outburst of Comet 2P/Encke at
its 2000 perihelion passage
Authors: Lamy, P.; Biesecker, D. A.; Groussin, O.
2003Icar..163..142L Altcode:
Comet 2P/Encke was observed with the SOHO/LASCO C2 and C3 coronagraphs
over a time interval of 11 days, starting 4 days before its September
2000 perihelion passage and through several broadband visible
filters. The lightcurve reveals an outburst which started 4.9 days
after perihelion, with the brightness of the coma increasing by 1.5
mag in just a few hours and progressively decreasing thereafter,
probably going back to its original state in about 9 days. The color
information indicates that an approximately solar color continuum was
detected, implying that the observed signals were dominated by solar
light scattered off submillimetric dust grains. We propose that the
rapid migration of the subsolar point over the southern hemisphere
during the perihelion passage activates one or several new active
regions enriched in submillimetric grains, with the observed outburst
corresponding to the initial blow-off of their mantle. This scenario
is consistent with other observations and implies that the south polar
region of the nucleus of 2P/Encke has very distinct properties.
---------------------------------------------------------
Title: New Modeling of Cometary Dust Tails
Authors: Jorda, L.; Lamy, P. L.; Coliac, J. -F.; Bout, M.; Colas,
F.; Lecacheux, J.; Rauer, H.; Weiler, M.
2003DPS....35.3820J Altcode: 2003BAAS...35R.988J
We present a technique for modeling cometary dust tails. The
technique is based on Monte Carlo simulations of a large number of
“model-images”, recombined linearly to fit the observed CCD image of
the dust tail. In essence, our technique is similar (but not identical)
to that originally proposed by Kimura and Liu (1975, 1982) and developed
by Fulle (1987, 1989), but incorporates new features such as the
rigorous calculation of the light scattered by the dust grains. It
can be used to interactively retrieve the dust size and velocity
distributions and to compute the dust production rate. We present
the application of this technique to comet 67P/Churyumov-Gerasimenko,
the new target of ESA's Rosetta mission and to comets observed with
the SOHO/LASCO coronagraphs (C/1996 B2 Hyakutake, C/2002 S2 SOHO 517,
C2002 X5 Kudo-Fujikawa, C2002 V1 NEAT and 96P/Machholz 1). <P />--
Fulle, M., A&A 171, 327, 1987. <P />-- Fulle, M., A&A 217, 283,
1989. <P />-- Kimura, H., and Liu, C.-P., AcASn 16, 138, 1975. <P />--
Kimura, H., and Liu, C.-P., AcASn 23, 232, 1982.
---------------------------------------------------------
Title: The Nucleus of Comet 67P/Churyumov-Gerasimenko, the New Target
of the Rosetta Mission
Authors: Lamy, P. L.; Toth, I.; Weaver, H.; Jorda, L.; Kaasalainen, M.
2003DPS....35.3004L Altcode: 2003BAAS...35..970L
We report the detection of the nucleus of comet
67P/Churyumov-Gerasimenko, the new target of the Rosetta mission, with
the Planetary Camera (WFPC2) of the Hubble Space Telescope (HST). The
observations were performed between 11.4 and 12.3 March 2003 (i.e.,
a time interval of 21 hr) when the comet was at heliocentric and
geocentric distances of respectively 2.51 and 1.53 AU and at a phase
angle of 4.8 deg. The high spatial resolution (a WFPC2 pixel projected
to 50 km at the distance of the comet) insured a very large contrast of
the nucleus over its surrounding coma, reaching a factor of typically
30 in the peak pixels. The 61 images allowed us to determine 49 R
magnitudes and 12 V magnitudes of the nucleus. Assuming a spherical
body with a geometric albedo of 0.04 and a phase coefficient of 0.04
mag/deg, we derived an effective radius of 1.98 +/- 0.02 km. The
lightcurve data were analyzed using both the PDM (Phase Dispersion
Minimization) and the Fourier technics. Assuming a classical double
peak lightcurve, the two technics give the same rotational period of
P=12.3 +/- 0.27 hr. This result is highly robust since the probability
that the period detection with the PDM technics is due to random noise
amounts to only 3E-11. The lightcurve which conspicuously deviates
from a sinusoide with shallow minima and narrow, unequal maxima, was
inverted in order to model the 3-dimensional shape of the nucleus using
the method developed by Kaasalainen et al. (Icarus 153, 37, 2001). The
rotational state is constrained to be close to principal axis rotation
of maximum inertia to get physically consistent solutions. All plausible
solutions share the same qualitative global shape characteristics. The
model which best fits the observed lightcurve (rms deviation of 0.028
mag) has a rotation axis tilted by about 8 deg from the principal axis,
a rotational period of 12.69 +/-0.10 hr, an aspect angle of 90 +/- 20
deg (i.e., equatorial view) and a slightly rugged shape. The color of
the nucleus is moderately red with a color index V-R = 0.51, the most
common value among cometary nuclei. The OH production rates impose a
rather low active fraction at perihelion, 4% to 7%. The activity is
thus limited to probably a few, very small areas, consistent with the
detection of several jets in the coma. The dust production rate was
characterized by Afρ = 40 cm. <P />We thank S. Beckwith for granting
us HST Director's Discretionary time on a very short notice. This work
was supported by grants from CNRS and CNES, and from NASA to H. W.
---------------------------------------------------------
Title: Hubble Space Telescope Observations of the Nucleus Fragment
73P/Schwassmann-Wachmann 3-B
Authors: Toth, I.; Lamy, P. L.; Weaver, H. A.
2003DPS....35.3805T Altcode: 2003BAAS...35..985T
The nucleus of 73P/Schwassmann-Wachmann 3 (73P/SW3), a Jupiter-Family
comet, has non-tidally broken into at least three components A, B and
C, in autumn 1995. Fragment B was detected with the Planetary Camera
2 of the Hubble Space Telescope on 26 November 2001. i.e., after the
comet's perihelion passage on 27.9 January 2001, when it was at 3.25
AU from the Sun, 2.33 AU from the Earth, and at a solar phase angle
of 7.4<SUP>o</SUP>. The high spatial resolution of the PC2 allowed
to separate the signal of the faint nucleus fragment from that of its
active coma, and we measured its R magnitude from our images taken with
the F675W filter. Assuming a spherical body whose geometric albedo is
0.04 and a linear phase coefficient of 0.04 mag/deg for the R band,
we derived an effective radius of 0.68+/-0.04 km. The short time span
of our HST observations did not allow to determine its shape but the
lower limit of its axial ratio a/b (assuming a prolate spheroid)
is ∼1.16. From the pre-breakup radius of the original nucleus
of 1.3 km determined by Boehnhardt et al. (2002: EMPl 90, 131),
we found that the fractional volume of fragment B is about 14%. Its
size of a few hundred meters, typical of fragments of other split
comets, is probably too large for a primordial building block and
indicate that it still is a conglomerate; further disintegration of
this fragment remains possible. Its level of activity is remarkably
high in spite of a heliocentric distance of ∼3.2 AU, just beyond
the limit for sublimation of water ice (2.8 AU). We measured an Afρ
of 19.6-23.2 cm but the determination of a dust production rate is
precluded by the absence of gas production rates at the time of our
observation. Ground-based observations performed in 2001 by Boehnhardt
et al. (2002: EMPl 90, 131) indicate that another fragment (E) has
already disappeared, and we conclude that this may well be short-term
fate of fragment B as it may not survive its next perihelion passage in
2006. The tau-Herculids meteor swarm associated to 73P/SW3 will likely
experience an increase of activity. <P />This work was supported by the
CNRS, CNES, and Université de Provence, France, and by the Hungarian
Academy of Science through grant No. 9871.
---------------------------------------------------------
Title: SOHO/LASCO Observation of Comet C/2002 X5 Kudo-Fujikawa at
its 2003 Perihelion Passage
Authors: Bout, M. V.; Lamy, P. L.; Llebaria, A.
2003DPS....35.3821B Altcode: 2003BAAS...35..988B
Comet C/2002 X5 Kudo-Fujikawa was observed with the SOHO/LASCO C2
and C3 coronagraphs over a time interval of 7 days, starting 4 days
before its 29 January 2003 perihelion passage and through several
broadband visible filters. A total of 134 images were obtained with
the C3 clear filter, 51 images with the C2 orange filter completed
by 20 color sequences. The lightcurves reveal that the brightness
of the coma steeply increased to reach local maxima on 27 January,
then suffered a drastic turnover, decreasing by about 0.8 mag to reach
minimum values on 27.8, then increased again to reach absolute maxima
slightly before perihelion passage and finally decreased. This pattern
of activity is consistent with the apparition of a new, anti-solar dust
tail widely separated from the main tail that the comet originally
sported. This translates in an unusual butterfly pattern where two
"decoupled" tails co-exist at the same time. Short-time variations
in the lightcurves may be caused by the rotation of the nucleus,
suggesting a rotation period of about 4 hours.
---------------------------------------------------------
Title: The solar high-resolution imager - coronagraph LYOT mission
Authors: Vial, Jean-Claude; Song, Xueyan; Lemaire, Philippe; Gabriel,
Alan H.; Delaboudiniere, Jean-Pierre; Bocchialini, Karine; Koutchmy,
Serge L.; Lamy, Philippe L.; Mercier, Raymond; Ravet, Marie Francoise;
Auchere, Frederic
2003SPIE.4853..479V Altcode:
The LYOT (LYman Orbiting Telescope) solar mission is proposed to
be implemented on a micro-satellite of CNES (France) under phase A
study. It includes two main instruments, which image the solar disk
and the low corona up to 2.5 R<SUB>o</SUB> in the H I Lyman-α line
at 121.6 nm. The spatial resolution is about 1” for the disk and
2.5” for corona. It also carries an EIT-type telescope in the He II
(30.4 nm) line. The coronagraph needs a super polished mirror at the
entrance pupil to minimize the light scattering. Gratings and optical
filters are used to select the Lyman-α wavelength. VUV cameras with
2048×2048 pixels record solar images up to every 10 seconds. The
satellite operates at a high telemetry rate (more then 100 kb/s,
after onboard data compression). The envisaged orbits are either
geostationary or heliosynchronous. Possible launch dates could be end
of 2006 - beginning of 2007.
---------------------------------------------------------
Title: Commission 21: Light of the night sky (Lumière du ciel
nocturne)
Authors: Lamy, Philippe
2003IAUTA..25..199L Altcode: 2003IAUTr..25A.199L
No abstract at ADS
---------------------------------------------------------
Title: Two-dimensional electron density in the solar corona from
inversion of white light images - Application to SOHO/LASCO-C2
observations
Authors: Quémerais, E.; Lamy, P.
2002A&A...393..295Q Altcode:
We present here the inversion method which has been developed to derive
the electron density in the Solar Corona from LASCO-C2 white light
images. We discuss how our inversion scheme can be applied either
to images of polarized brightness of the corona or images of total
brightness after removal of the dust and stray light components. The
outputs from both schemes are compared. For the inversion of
two-dimensional images of the solar corona, it is necessary to assume a
global geometry for the electron density. We compare results obtained
for spherical and axi-symmetric geometries. Finally, our results for
December 1996 are compared to previous derivations of the electron
radial density profiles obtained by other measurements.
---------------------------------------------------------
Title: The Study of Comets
Authors: Combi, M. R.; Capria, M. T.; Cremonese, G.; de Sanctis,
M. C.; Farnham, T. L.; Fernandez, Y. R.; Festou, M. C.; Fink, U.;
Green, J. R.; Harris, W. M.; Hergenrother, C. W.; Lamy, P. L.;
Larson, S. M.; Levison, H. F.; Lien, D. J.; Lisse, C. M.; Meisel,
D. D.; Moehlmann, D. T. F.; Mueller, B. E. A.; Samarasinha, N. H.;
Sitko, M. L.; Weaver, H. A.; Weissman, P. R.
2002ASPC..272..323C Altcode: 2002fsse.conf..323C
The study of comets is critical to our understanding the origin,
structure and evolution of the solar system in general and of life
itself. We present here a brief summary of our current understanding
of comets and their important place in the solar system, as well as
our recommendations regarding priorities for their study over the next
decade in the context of a coordinated program of spacecraft missions
and ground-based and theoretical investigations.
---------------------------------------------------------
Title: Sungrazing Comets Discovered with the SOHO/LASCO Coronagraphs
1996-1998
Authors: Biesecker, D. A.; Lamy, P.; St. Cyr, O. C.; Llebaria, A.;
Howard, R. A.
2002Icar..157..323B Altcode:
The Kreutz sungrazing family of comets is unique because of its small
perihelion distance and because of the large number of known members
of this family. SOHO/LASCO coronagraph observations beginning in 1996
have revealed an unprecedented number of Kreutz comets. These new
coronagraph observations improve upon earlier observations because of a
larger field-of-view, increased image cadence, and better photometric
measurements. This paper presents the lightcurves of the 141 Kreutz
family comets observed from 1996 through 1998. Throughout this period,
the number of family members discovered each year is shown to be
constant. None of the comets were detected postperihelion. The
lightcurves show distinctive characteristics which reveal much
about the properties of the nuclei. It is shown that the individual
fragments can be related to one of two “standard candles,” which
we call Universal Curves. The comets all reach a peak brightness at
one of two characteristic distances (both near 12 R<SUB>⊙</SUB>)
and that the comets fragment at another characteristic distance
(about 7 R<SUB>⊙</SUB>). Also, evidence is seen for line emission,
which varies with heliocentric distance.
---------------------------------------------------------
Title: The fractal nature of the polar plumes
Authors: Llebaria, A.; Saez, F.; Lamy, P.
2002ESASP.508..391L Altcode: 2002soho...11..391L
Polar plumes are often perceived as isolated structures, possibly
tube-like, in super-radial expansion. As a consequence, coronal
holes are considered composed of plumes and dominating inter-plume
regions from which the fast solar wind originates. In order to test
the validity of this concept, we pursued the analysis of a sequence of
high cadence continuous observations obtained with the SOHO/LASCO-C2
coronagraph in March 1997. The spectral analysis of the plume pattern
show that their spatial distribution is of fractal type. This implies
that their distribution in a surface section of the coronal hole is
self-affine and that coronal holes have a fibrous structure, at least
at the spatial scales of the visible observations.
---------------------------------------------------------
Title: Electron density in coronal jets
Authors: Bout, M.; Lamy, P.; Llebaria, A.
2002ESASP.508..379B Altcode: 2002soho...11..379B
Coronal jets are observed by the SOHO/LASCO C2 and C3 coronagraphs
as thin, highly collimated structures. The determination of their
electron density cannot be performed with the standard inversion of pB
images because of the inherent assumption of global spherical or axial
symmetry of the corona which is totally inappropriate in the case of
local structures. Our analysis first isolates the jets by subtracting
the background corona. Their radiance is then compared to calculated
models which assume a tube like structure. This allows to derive the
true radial profile of their electron density.
---------------------------------------------------------
Title: Calibration of the LASCO C3 Coronal Images
Authors: Morrill, J.; Biesecker, D.; Esfandiari, A.; Korendyke, C.;
Moses, D.; Rich, N.; Vourlidas, A.; Wang, D.; Howard, R. A.; Lamy,
P.; Llebaria, A.; Thernisien, A.
2002AAS...200.5503M Altcode: 2002BAAS...34R.732M
The LASCO C3 coronagraph has provided coronal observations since May,
1996. Preliminary calibrations have been available during most of this
time period. However, some aspects of the calibration have required
re-evaluation and we are just completing a complete review of the
calibration procedure for these images. In this presentation we will
discuss the steps required to correct LASCO C3 images. This includes
corrections required by both optical and electrical characteristics
of the instrument as well as timimg and spacecraft pointing driven
correctons.
---------------------------------------------------------
Title: The Nucleus of Comet 22P/Kopff and Its Inner Coma
Authors: Lamy, P. L.; Toth, I.; Jorda, L.; Groussin, O.; A'Hearn,
M. F.; Weaver, H. A.
2002Icar..156..442L Altcode:
We report the detection of the nucleus of Comet 22P/Kopff with the
Planetary Camera of the Hubble Space Telescope (HST) and with the
Infrared Camera of the Infrared Space Observatory (ISOCAM). The
HST observations were performed on 18 July 1996, 16 days after its
perihelion passage of 2 July 1996, when it was at R<SUB>h</SUB>=1.59
AU from the Sun and Δ=0.57 AU from the Earth. A sequence of images
taken with four broad-band filters was repeated eight times over
a 12-h time interval. The ISOCAM observations were performed on 15
October 1996, 106 days after the perihelion passage, when the comet
was at R<SUB>h</SUB>=1.89 AU from the Sun and Δ=1.32 AU from the
Earth. Seven images were obtained with a broad-band filter centered at
11.5 μm. In both instances, the spatial resolution was appropriate to
separate the signal of the nucleus from that of the coma. We determine
the Johnson-Kron-Cousins BVRI magnitudes of the nucleus. The visible
lightcurves constrain neither the rotation period nor the ratio
of semiaxes. We favor the solution of a rather spherical nucleus,
although the situation of a pole-on view of an irregular body cannot
be excluded. The systematic decreasing trend of the lightcurves
could suggest a period of several days. Combining the visible and
infrared observations, we find that an ice-dust mixed model is ruled
out, while the standard thermal model leads to a nuclear radius of
R<SUB>n</SUB>=1.67±0.18 km of albedo p<SUB>v</SUB>=0.042±0.006. The
red color of the nucleus is characterized by a nearly constant gradient
of S'=14±5% per kÅ from 400 to 800 nm. We estimate a fractional
active area of 0.35 which places 22P/Kopff in the class of highly
active short-period comets. At R<SUB>h</SUB>=1.59 AU, the dust coma
is characterized by a red color with a reflectivity gradient S'=17±3%
per kÅ, compatible with that of the nucleus, and Afρ=545 cm, yielding
a dust production rate of Q<SUB>d</SUB>=130 kg sec <SUP>-1</SUP>.
---------------------------------------------------------
Title: New insights on the onsets of coronal mass ejections from soho
Authors: Plunkett, S. P.; Michels, D. J.; Howard, R. A.; Brueckner,
G. E.; St. Cyr, O. C.; Thompson, B. J.; Simnett, G. M.; Schwenn, R.;
Lamy, P.
2002AdSpR..29.1473P Altcode:
Coronal mass ejections (CMES) are among the most dramatic forms of
transient activity occurring in the solar atmosphere. Despite over
twenty years of research, many basic questions related to the physics
of CMEs have remained unanswered. Observations with the LASCO and EIT
experiments on SOHO, combined with recent theoretical modeling, have
provided new insights on some of these outstanding questions and have
also raised many new ones that need to be addressed in the future. In
this paper, we present some of the new results from SOHO pertaining
to the source regions and onsets of CMEs, and their evolution in the
corona. We emphasize the important role that studies of CMEs will play
in the International Solar Cycle Studies program.
---------------------------------------------------------
Title: New Modeling of 19P/Borrelly s Spin State
Authors: Jorda, L.; Gutierrez, P.; Lamy, P.
2002cosp...34E3221J Altcode: 2002cosp.meetE3221J
Comet 19P/Borrelly has been imaged by the Deep Space 1 (DS1) spacecraft
in Sept. 2001. The images allowed the retrieval of the size and shape
of the comet nucleus with a high accuracy. The spin orientation of
this comet has also been derived from the DS1 MICAS images and from
ground-based observations obtained during the last decades. We will
present here new modeling of the temporal evolution of the spin state
of comet 19P/Borrelly using these new observational constraints.
---------------------------------------------------------
Title: Solar cycle variation of the radiance and the global electron
density of the solar corona
Authors: Lamy, P.; Llebaria, A.; Quemerais, E.
2002AdSpR..29..373L Altcode:
The question of the global activity of the solar corona, as a function
of time and distance from the center of the Sun, is considered by
analyzing SOHO/LASCO-C2 daily polarized images over four years, i.e.,
from the minimum to the rising phase of the 23rd solar cycle. After
proper correction for instrumental polarization, they are combined
to produce maps of the polarized radiance pB and of the radiance
of the K-corona (assuming a model for the K-corona polarization
p <SUB>K</SUB>). The electron density is obtained by inversion of
the pB images assuming local spherical symmetry. Synoptic maps are
created at four distances between 2.7 and 5.5 solar radii. In order to
conveniently quantify their temporal variation, the polarized radiance,
the radiance and the electron density are integrated first globally
and then in zones of different latitudes to separate the equatorial and
the polar regions. These integrals remained constant in 1996 and then
progressively increased with the rising activity of the Sun. However
the polar and equatorial regions exhibited different behaviours as the
former remained stable over a much longer time interval and experienced
a larger increase than the latter.
---------------------------------------------------------
Title: Characterization of coronal streamers from LASCO-C2
observations and implications for the slow solar wind
Authors: Lamy, P.; Bout, M.; Llebaria, A.; Thernisien, A.
2002cosp...34E1507L Altcode: 2002cosp.meetE1507L
Recent analysis of LASCO images of the corona obtained during the
rising phase of the present solar cycle indicates that there exists
streamers distinct from the classical streamer belt which results
from line-of-sight integration through folds in a warped current sheet
(Liewer et al., 2001, JGR 106, A8, 15903). These "isolated" streamers
are the result of scattering from regions of enhanced density associated
with active region outflow. A preliminary quantitative analysis
of LASCO-C2 images of several such structures indicates enhancement
factors as large as 50 compared to the classical model of Van de Hulst
(Bout et al., 2002, SOHO-11 Conference). We will report on further
progress in analyzing these streamers and our attempt to measure
outflow speeds. Our ultimate purpose is to assess the contribution of
these structures to the slow solar wind.
---------------------------------------------------------
Title: The Properties of Sun-grazing Comets
Authors: Lamy, P.; Biesecker, D.
2002cosp...34E3159L Altcode: 2002cosp.meetE3159L
Over 450 sun -grazing comets have now been detected with the Large
Angle Spectroscopic Coronagraphs (LASCO) on the Solar and Heliospheric
Observatory (SOHO). The bulk of them belong to the Kreutz family while
49 are either scattered or belong to other families. In this review,
we first consider the statistical properties of the distribution of
the orbital elements to establish the reality of sub-groups and to
characterize the process of their fragmentation. We then analyze the
light curves and confront the different observed behavior with the
dynamical families. For a few comets, color information is available
and helps to characterize the sun-grazers.
---------------------------------------------------------
Title: Characterization of the polar plumes from high cadence
LASCO-C2 observations
Authors: Llebaria, A.; Thernisien, A.; Lamy, P.
2002AdSpR..29..343L Altcode:
In order to understand the spatio-temporal characteristics of polar
plumes, we analyzed a sequence of continuous observations obtained
with the SOHO/LASCO-C2 coronagraph over a period of 3 days with a time
resolution of 10 minutes. We generated the time intensity diagram (TID)
where the radiance of the plumes is displayed as a function of their
angular positions and time. The derivatives of the TID with respect
to the phase angle on the one hand and to time on the other hand allow
us to define the trajectories of individual plumes and their temporal
variations. This confirms that polar plumes are enduring structures
that are only transiently lit, as we found before, but the present
analysis reveals that the blinking takes place on time scales as
short as 2 hours. This is confirmed by the radial intensity diagrams
(RID) which track each individual plume by displaying its radiance
as a function of time and distance. These diagrams also indicate a
constant speed of expansion with a mean value of 460 km/sec.
---------------------------------------------------------
Title: Properties of the surface of 46P/Wirtanen from the observed
water production rate
Authors: Groussin, O.; Lamy, P.
2002cosp...34E2963G Altcode: 2002cosp.meetE2963G
We present a thermal model to explain the temporal variations of
the water production rates QH2 O of comet 46P/Wirtanen, in order to
analyse its surface. Our model is a differenciated spherical nucleus
with a macroscopic mosaic of small and numerous active and inactive
regions. At a heliocentric distance Rh >1.5 AU, the active regions
represent 5-15 % of the surface. At 1.5 AU, a rapid increase takes
place in about 10 days and the active fraction reaches 70 to 100 %,
and then remains approximatively constant up to perihelion where QH2 O
=1.1-1.7 1028 molecules s-1 . Post-perihelion, the activity goes down
again to 10 %. The model is consistent with a geometric albedo lower
than 0.1. A rubble mantle of a few millimeters can form post-perihelion
and explain the variations of the activity over one orbit. Finally,
we derived an erosion of 1 meter per revolution and a lifetime for
the nucleus of several hundred revolu- tions.
---------------------------------------------------------
Title: The Rosetta/Osiris Narrow Angle Camera: Performances and
Prospects for High Spatial Resolution Imaging of the Nucleus of
Comet 46P/Wirtanen
Authors: Lamy, P.; Jorda, L.; Origne, A.; Thomas, N.; Hviid, S.
2002cosp...34E3158L Altcode: 2002cosp.meetE3158L
The Narrow Angle Camera (NAC) of the OSIRIS experiment is aimed at
imaging a cometary nucleus, that of 46P/Wirtanen, at an unsurpassed
spatial resolution of a few centimeters per pixel. We describe the
innovative three-mirror, anastigmatic optical design and its all
silicon carbide implementation (mirrors and structure). We report
on the extended program of tests and calibrations carried out to
fully characterize the instrument, in particular at low temperatures,
and synthesize the actual performances. We finally discuss the future
program of observation and the prospect for characterizing the asteroids
Otawara and Siwa and the nucleus of 46P/Wirtanen.
---------------------------------------------------------
Title: Evolution of the Electron Density in the Streamer Belt during
the Solar
Authors: Llebaria, A.; Lamy, P.; Saez, F.
2002cosp...34E1606L Altcode: 2002cosp.meetE1606L
White-light images of the corona obtained with the SOHO/LASCO-C2
coronagraph over more than six years reveal the dramatic changes
of the structure and radiance distribution of the streamer belt
from the minimum to the maximum of the present solar cycle. While
it is qualitatively understood that the widening of the belt is a
consequence of the tilting and warpening of the plasma current sheet,
no quantitative study has been performed to derive physical parameters
from these images in order to help characterizing the slow solar
wind. Our approach consists in reproducing the widening of the streamer
belt and its periodic evolution with the solar rotation with a model
combining a layer of plasma centered around the heliospheric current
sheet and isolated streamers associated to active regions. The Thompson
scattering from the coronal electrons of this 3D model is calculated
and comp ared to the LASC0-C2 images. This allows to estimate the local
electron density in the corona between 3 and 6 solar radii during the
rising phase of a solar cycle and to put constraints on the evolution
of the slow solar wind.
---------------------------------------------------------
Title: Hubble Space Telescope Observations of the Nucleus of Comet
9P/Tempel 1
Authors: Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Weaver, H. A.;
Weissman, P. R.
2001Icar..154..337L Altcode:
The nucleus of Comet 9P/Tempel 1, the target of the Deep Impact mission,
was detected during Hubble Space Telescope observations taken with
the wide-field planetary camera 2 (WFPC2) on 31 December 1997 when
the comet's solar phase angle was 3.°8, its heliocentric distance was
4.48 AU, and its geocentric distance was 3.53 AU. Sixteen images were
taken through the F675W filter, and all of them revealed a point-like
source without any detectable coma. From these images, we derived the
R magnitude of the nucleus in the Johnson-Kron-Cousins photometric
system for the entire 11.5-h time span of the observations. Assuming
a prolate spheroid whose spin axis lies close to the plane of the
sky, the partial lightcurve indicates semi-axes a=3.9 km and b=2.8
km (assuming a geometric albedo of 0.04 for the R band and a phase
coefficient of 0.04 mag deg <SUP>-1</SUP>) and a rotational period
in the range of ∼25-33 h. The upper limit of the parameter Afρ,
which characterizes the dust production rate, is 1 cm. We also derive
a fractional active area at 1.78 AU of ∼4%.
---------------------------------------------------------
Title: Latest Results from SOHO/LASCO Observations of Kreutz Family
Comets
Authors: Biesecker, D. A.; Lamy, P. L.; St. Cyr, O. C.; Llebaria,
A.; Howard, R. A.
2001DPS....33.4601B Altcode: 2001BAAS...33Q1123B
As of September 2001, almost 350 members of the Kreutz sungrazing comet
family have been observed with the LASCO coronagraphs on SOHO. The
lightcurves of many of these comets share common features. They
all reach a peak brightness at a heliocentric distance of about 12
solar radii (0.056 AU), then fade as they approach closer to the Sun,
down to a distance of 7 solar radii where the fading stops. A closer
examination reveals that two groups can be distinguished, one which
peaks at 11.2 solar radii and one at 12.3 solar radii. Observations
through an `Orange' filter (5400-6400 Angstroms) are systematically
brighter than those through a `Clear' filter (4000-9000 Angstroms)
and the difference changes with heliocentric distance. Recently,
high cadence observations with other color filters have shown that the
enhancement is limited to the Orange and Clear filters. This supports
our idea that Na emission is a likely candidate for the enhancement. We
will present these observations as well as our latest ideas to explain
the LASCO observations.
---------------------------------------------------------
Title: The Nucleus of 10 Short-Period Comets
Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; Delahodde, C. E.;
Jorda, L.; A'Hearn, M. F.
2001DPS....33.3101L Altcode: 2001BAAS...33Q1093L
We report on the successful detection and extensive characterization
of the nuclei of 10 short-period comets with the Hubble Space
Telescope: 47P/Ashbrook-Jackson, 61P/Shajn-Schaldach, 70P/Kojima,
74P/Smirnova-Chernikh, 76P/West-Kohoutek-Ikemura, 82P/Gehrels 3,
86P/Wild 3, 87P/Bus, 110P/Hartley 3, 147P/Kushida-Muramatsu. The
observations were performed with the Planetary Camera of WFPC2 during
cycle 9, between July 2000 and June 2001. Each comet was observed eight
times over a time span of about 12 hours through different filters, up
to three (V, R, I) for the brightest ones. The sizes were determined
assuming a geometric albedo of 0.04 for the R band and a phase law
of 0.04 mag/deg. We confirm our past findings that cometary nuclei
are generally extremely small; the radius of 147P/Kushida-Muramatsu
was only 0.13 km. We also present the results for the colors and
the lightcurves of the nuclei and discuss the implications for
their shape and rotational state. This work was supported by grants
from the Universite de Provence, from C.N.E.S., C.N.R.S. (France),
from the Hungarian Academy of Science and from NASA through grant
HST-GO-08699.01-A from the STScI.
---------------------------------------------------------
Title: Broadband infrared photometry of comet Hale-Bopp with ISOPHOT
Authors: Grün, E.; Hanner, M. S.; Peschke, S. B.; Müller, T.;
Boehnhardt, H.; Brooke, T. Y.; Campins, H.; Crovisier, J.; Delahodde,
C.; Heinrichsen, I.; Keller, H. U.; Knacke, R. F.; Krüger, H.; Lamy,
P.; Leinert, Ch.; Lemke, D.; Lisse, C. M.; Müller, M.; Osip, D. J.;
Solc, M.; Stickel, M.; Sykes, M.; Vanysek, V.; Zarnecki, J.
2001A&A...377.1098G Altcode:
Comet Hale-Bopp was observed five times with ISOPHOT, the photometer
on board ESA's Infrared Space Observatory (ISO) between 4.6 and 2.8
AU. Each time, broadband photometry was performed using 4 different
detectors, 5 apertures and 10 filters covering the range between 3.6
and 170 mu m. Background observations were performed with identical
instrument settings at the same positions on the sky several days
after the comet observations. The observation strategy and the data
reduction steps are described in some detail, including the techniques
to correct for variable detector responsivity. The resulting inband
power values of the Hale-Bopp observations and their uncertainties are
given. The mean uncertainty is 25%. The final fluxes were computed,
taking into account the zodiacal background, possible offset of the
comet's position from the center of the aperture, the brightness
distribution within the coma, and the spectral energy distribution
of the comet's emission. Strong thermal emission from a broad size
distribution of dust particles was detected in all of the data sets,
even at r=4.6-4.9 AU pre-perihelion and 3.9 AU post-perihelion; the
total thermal energy varied as r<SUP>-3</SUP>. The 7.3-12.8 mu m color
temperature was ~ 1.5 times the blackbody temperature, higher than
that observed in any other comet. Silicate features at 10 and 25 mu m
were prominent in all 5 data sets, the largest heliocentric distances
that silicate emission has been detected in a comet. The presence of
crystalline water ice grains is suggested from the 60 mu m excess
emission at 4.6-4.9 AU, consistent with the observed Q<SUB>mathrm
{OH</SUB>} if the icy grains were slightly warmer than an equilibrium
blackbody. The average albedo of the dust is higher than that of comet
P/Halley, but lower than other albedo measurements for Hale-Bopp nearer
perihelion. There is no evidence for a component of cold, bright icy
grains enhancing the scattered light at 4.6 AU. Simple models for a
mixture of silicate and absorbing grains were fit to the ISO spectra
and photometry at 2.8 AU. The observed flux at lambda > 100 mu m
requires a size distribution in which most of the mass is concentrated
in large particles. Dust production rates of order 1.5x 10<SUP>5</SUP>
kg s<SUP>-1</SUP> at 2.8 AU and 3x 10<SUP>4</SUP> kg s<SUP>-1</SUP>
at 4.6 AU have been found. They correspond to dust to gas mass ratios
of 6 to 10. With supporting observations by ISOCAM, SWS, LWS, and
ground-based observations at the European Southern Observatory at La
Silla in Chile.
---------------------------------------------------------
Title: Solar Polar Plume Lifetime and Coronal Hole Expansion:
Determination from Long-Term Observations
Authors: DeForest, C. E.; Lamy, P. L.; Llebaria, A.
2001ApJ...560..490D Altcode:
We have generated off-limb polar synoptic charts of polar plume
evolution at various solar altitudes using EUV Imaging Telescope and
Large Angle and Spectrometric Coronagraph data from 1996 December. The
charts allow direct measurement of the altitude expansion of the solar
minimum coronal holes. We find expansion values that are consistent with
the conventional picture of superradial expansion and inconsistent with
radial expansion. Using visible red line data as a bridge between EUV
and white-light images of the corona, we are able to confirm that the
coronal structure seen at the base of the corona is preserved throughout
the considered altitude range of 1.1-3.0 R<SUB>solar</SUB>. We show that
polar plumes are episodic in nature, lasting perhaps 24 hr but recurring
for up to weeks at a time; this strengthens the picture that they are
caused by magnetic heating under the influence of supergranulation.
---------------------------------------------------------
Title: HST and VLT Investigations of the Fragments of Comet C/1999 S4
(LINEAR)
Authors: Weaver, H. A.; Sekanina, Z.; Toth, I.; Delahodde, C. E.;
Hainaut, O. R.; Lamy, P. L.; Bauer, J. M.; A'Hearn, M. F.; Arpigny,
C.; Combi, M. R.; Davies, J. K.; Feldman, P. D.; Festou, M. C.; Hook,
R.; Jorda, L.; Keesey, M. S. W.; Lisse, C. M.; Marsden, B. G.; Meech,
K. J.; Tozzi, G. P.; West, R.
2001Sci...292.1329W Altcode:
At least 16 fragments were detected in images of comet C/1999 S4
(LINEAR) taken on 5 August 2000 with the Hubble Space Telescope (HST)
and on 6 August with the Very Large Telescope (VLT). Photometric
analysis of the fragments indicates that the largest ones have
effective spherical diameters of about 100 meters, which implies that
the total mass in the observed fragments was about 2 × 10<SUP>9</SUP>
kilograms. The comet's dust tail, which was the most prominent optical
feature in August, was produced during a major fragmentation event,
whose activity peaked on UT 22.8 +/- 0.2 July 2000. The mass of
small particles (diameters less than about 230 micrometers) in the
tail was about 4 × 10<SUP>8</SUP> kilograms, which is comparable
to the mass contained in a large fragment and to the total mass lost
from water sublimation after 21 July 2000 (about 3 × 10<SUP>8</SUP>
kilograms). HST spectroscopic observations during 5 and 6 July 2000
demonstrate that the nucleus contained little carbon monoxide ice
(ratio of carbon monoxide to water is less than or equal to 0.4%),
which suggests that this volatile species did not play a role in the
fragmentation of C/1999 S4 (LINEAR).
---------------------------------------------------------
Title: Projective Transform Techniques to Reconstruct the 3-D
Structure and the Temporal Evolution of Solar Polar Plumes
Authors: Llebaria, A.; Thernisien, A.; Lamy, P.
2001ASPC..238..377L Altcode: 2001adass..10..377L
A sequence of 400 images obtained over three days with the C2-LASCO/SOHO
coronagraph was used to disentangle the complex evolution of the
structures observed on the corona of the Sun's North pole. Projective
transforms were used to find and delimit the elusive linear structures
on each image (< 1:1 of SNR). From frame to frame, these structures
show strong brightness variations as well as lateral shifts which
are linked to rotation of the Sun. Taking advantage of solar corona
rotation as a rigid body (of ~28 days period), we are able to extract
short sinograms to obtain a 3-D reconstruction with few hypotheses. The
whole procedure is described, emphasizing the role of the bilinear
transform as a new tool in this process.
---------------------------------------------------------
Title: Division III: Planetary Systems Sciences
Authors: Marov, Mikhail Ya.; A'Hearn, G. M. F.; Baggaley, J.; Bowell,
E.; Bowyer, S.; Cruikshank, D.; de Bergh, C.; Keller, H.; Lamy, P.;
Porubcan, V.; Watanabe, J.; Williams, I.; Zappala, V.
2001IAUTB..24..113M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Mars NetLander panoramic camera
Authors: Jaumann, Ralf; Langevin, Yves; Hauber, Ernst; Oberst,
Jürgen; Grothues, Hans-Georg; Hoffmann, Harald; Soufflot, Alain;
Bertaux, Jean-Loup; Dimarellis, Emmanuel; Mottola, Stefano; Bibring,
Jean-Pierre; Neukum, Gerhard; Albertz, Jörg; Masson, Philippe; Pinet,
Patrick; Lamy, Philippe; Formisano, Vittorio
2000P&SS...48.1377J Altcode:
The panoramic camera (PanCam) imaging experiment is designed to
obtain high-resolution multispectral stereoscopic panoramic images
from each of the four Mars NetLander 2005 sites. The main scientific
objectives to be addressed by the PanCam experiment are (1) to locate
the landing sites and support the NetLander network sciences, (2)
to geologically investigate and map the landing sites, and (3) to
study the properties of the atmosphere and of variable phenomena. To
place in situ measurements at a landing site into a proper regional
context, it is necessary to determine the lander orientation on
ground and to exactly locate the position of the landing site with
respect to the available cartographic database. This is not possible
by tracking alone due to the lack of on-ground orientation and the
so-called map-tie problem. Images as provided by the PanCam allow
to determine accurate tilt and north directions for each lander and
to identify the lander locations based on landmarks, which can also
be recognized in appropriate orbiter imagery. With this information,
it will be further possible to improve the Mars-wide geodetic control
point network and the resulting geometric precision of global map
products. The major geoscientific objectives of the PanCam lander
images are the recognition of surface features like ripples, ridges and
troughs, and the identification and characterization of different rock
and surface units based on their morphology, distribution, spectral
characteristics, and physical properties. The analysis of the PanCam
imagery will finally result in the generation of precise map products
for each of the landing sites. So far comparative geologic studies
of the Martian surface are restricted to the timely separated Mars
Pathfinder and the two Viking Lander Missions. Further lander missions
are in preparation (Beagle-2, Mars Surveyor 03). NetLander provides the
unique opportunity to nearly double the number of accessible landing
site data by providing simultaneous and long-term observations at four
different surface locations which becomes especially important for
studies of variable surface features as well as properties and phenomena
of the atmosphere. Major changes on the surface that can be detected by
PanCam are caused by eolian activities and condensation processes, which
directly reflect variations in the prevailing near-surface wind regime
and the diurnal and seasonal volatile and dust cycles. Atmospheric
studies will concentrate on the detection of clouds, measurements of
the aerosol contents and the water vapor absorption at 936 nm. In order
to meet these objectives, the proposed PanCam instrument is a highly
miniaturized, dedicated stereo and multispectral imaging device. The
camera consists of two identical camera cubes, which are arranged in a
common housing at a fixed stereo base length of 11 cm. Each camera cube
is equipped with a CCD frame transfer detector with 1024×1024 active
pixels and optics with a focal length of 13 mm yielding a field-of-view
of 53°×53° and an instantaneous filed of view of 1.1 mrad. A filter
swivel with six positions provides different color band passes in the
wavelength range of 400-950 nm. The camera head is mounted on top of a
deployable scissors boom and can be rotated by 360° to obtain a full
panorama, which is already covered by eight images. The boom raises
the camera head to a final altitude of 90 cm above the surface. Most
camera activities will take place within the first week and the
first month of the mission. During the remainder of the mission, the
camera will operate with a reduced data rate to monitor time-dependent
variations on a daily basis. PanCam is a joint German/French project
with contributions from DLR, Institute of Space Sensor Technology
and Planetary Exploration, Berlin, Institut d'Astrophysique Spatiale,
CNRS, Orsay, and Service d'Aéronomie, CNRS, Verrières-le-Buisson.
---------------------------------------------------------
Title: The nucleus of 13 short-period comets
Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; Delahodde, C.; Jorda,
L.; A'Hearn, M. F.
2000DPS....32.3604L Altcode: 2000BAAS...32.1061L
We report the successful detection of the nucleus of 13 short-period
comets with the Hubble Space Telescope. One orbit was devoted to each
comet and the observations were performed with the Planetary Camera
and at least two filters (V and R) and up to four (B, V, R, I) for the
brightest ones. Assuming spherical nuclei with a geometric albedo of
0.04 for the R band and a phase law of 0.04 mag/deg, we determined the
following radii: 4P/Faye: 1.77 km; 10P/Tempel 2: 4.60 km; 17P/Holmes:
1.71 km; 37P/Forbes: 0.81 km; 44P/Reinmuth 2: 1.63 km; 50P/Arend: 0.95
km; 59P/Kearns-Kwee: 0.79 km; 63P/Wild 1: 1.46 km; 71P/Clark: 0.68
km; 84P/Giclas: 0.90 km; 106P/Schuster: 0.94 km; 112P/Urata-Niijima:
0.90 km; 114P/Wiseman-Skiff: 0.78 km. We also obtained the spectral
reflectivities of those nuclei and of their coma and calculated the
dust production rates.
---------------------------------------------------------
Title: Detailed Phase Function of a Comet Nucleus: 28P/Neujmin 1
Authors: Delahodde, C. E.; Hainaut, O. R.; Lamy, P. L.; Meech, K. J.
2000DPS....32.3609D Altcode: 2000BAAS...32.1062D
Very little is known on the surface properties of cometary nuclei --
with the notable exception of the in-situ measurements for comet
Halley. A still unexplored method of investigation is the study of
the solar phase function, which can give us direct information on
the surface roughness as well as some independent constraints on the
albedo. In order to estimate properly the Hapke parameters describing
the phase function, one has to obtain measurements not only over a broad
phase angle (α ) range, but also at very small phase angle, in order
to sample the “opposition surge”, a brightening of the phase curve
occurring at α < 2-3<SUP>o</SUP>. In 2000, Comet 28P/Neujmin 1 was
an ideal candidate for a phase function study: its April opposition
was almost ideal (α = 0.8° ), and previous observations by Meech
et al. at similar heliocentric distances (r<SUB>h</SUB> >= 4 AU)
indicated that the comet was likely not to be active. We observed
this comet using ESO's NTT and 2.2m telescopes at La Silla, on 6
epochs from April to August 2000, covering α = 0.8 - 8<SUP>o</SUP> ,
with a good sampling of the opposition surge. In order to disentangle
the rotation effects from the phase effects, we obtained a complete
rotation coverage at opposition, providing us with a light-curve
template. For each subsequent epoch, we have obtained enough rotation
coverage to re-synchronize the light-curve fragments with the template,
and determine the magnitude change caused by the phase function. Using
these data, we hope to present the first detailed comet nucleus phase
function, and compare it with known C-type asteroids.
---------------------------------------------------------
Title: Spectral properties of the nucleus of short-period comets
Authors: Toth, I.; Lamy, P. L.
2000DPS....32.3705T Altcode: 2000BAAS...32.1063T
Comets, Edgeworth-Kuiper-Belt Objects (EKBOs), Centaurs and low albedo
asteroids contain a considerable amount of information regarding some
of the primordial processes that governed the formation of the early
Solar System planetesimals. Opportunities to determine the colors
of cometary nuclei are rare and relevant ground-based observations
are difficult to perform. Color diversities and similarities between
different types of small bodies have already been considered ([1] and
references therein). We pursue this analysis further by introducing new
BVRI colors obtained from our survey of cometary nuclei with the Hubble
Space Telescope [2] as well as recent data obtained on EKBOs. We present
preliminary results on the distribution of the BVRI colors (histograms,
two-color diagrams) and possible relationships between the colors
and orbital elements as well as the determined body sizes. The mean
colors of the selected sample of the short-period (s-p) comets are:
< (B-V) > = 0.91, < (V-R) > = 0.52, and < (V-I) > =
0.84. Pearson's linear correlation analysis of the (B-V) versus (V-R)
and (V-R) versus (V-I) colors show significant correlations for the
EKBOs+Centaurs sample while the s-p sample seems to be uncorrelated,
with a few outliers. The linear regression lines of the EKBOs+Centaurs
sample crosses through the sample of the s-p comets. There are no
correlations of the colors versus perihelion distances, effective
radii and perihelion distances as well as the (a,sin(i)) diagrams. This
work was supported by grants from CNRS and CNES, France and partially
by the the Hungarian Research Foundation OTKA T025049. [1] Luu, J.,
1993. Icarus 104, 138. [2] Lamy, P.L. et al., this conference
---------------------------------------------------------
Title: HST and VLT Investigations of the Fragments of C/1999 S4
(LINEAR)
Authors: Weaver, H. A.; West, R.; A'Hearn, M. F.; Arpigny, C.; Bauer,
J. M.; Combi, M. R.; Davies, J. K.; Delahodde, C. E.; Feldman, P. D.;
Fes tou, M. C.; Hainaut, O. R.; Hook, R.; Jorda, L.; Keesey, M. S. W.;
Lamy, P. L.; Lisse, C. M.; Marsden, B. G.; Meech, K. J.; Sekanina,
Z.; Toth, I.; Tozzi, G. -P.
2000DPS....32.3606W Altcode: 2000BAAS...32.1061W
Observations of C/1999 S4 (LINEAR) with the Hubble Space Telescope
(HST) on 2000 August 5.167--5.467 UT and with the Very Large Telescope
(VLT) on August 6.978--6.999 UT revealed the presence of over 17
fragments following the breakup of the nucleus in late July. Nearly
half the fragments were located in a “swarm” near the western “tip”
of the dust tail (i.e., the sunward side of the tail), but several
were significantly sunward of the tip, including one object that we
tentatively identify as the primary remnant of the original nucleus. The
correspondence between fragments in the HST and VLT images is generally
very good, but the brightest fragment in the HST image is not seen in
the VLT image, indicating rapid variability in activity. The dynamic
nature of the fragments was further highlighted by a dramatic change
in the appearance of the fragments in VLT images taken during August
9.976--9.996 UT, when they were barely detectable. The locations
and brightnesses of the fragments will be presented, along with a
discussion of the dynamics associated with the breakup event and its
subsequent evolution. We thank the Directors of the Space Telescope
Science Institute and the ESO/VLT for approving our observing programs
for Director's Discretionary Time.
---------------------------------------------------------
Title: Properties of 2060 Chiron from infrared ISOPHOT observations
Authors: Groussin, O.; Peschke, S.; Lamy, P. L.
2000DPS....32.2105G Altcode: 2000BAAS...32.1031G
We present the analysis of new observations of 2060 Chiron with
the Infrared Space Observatory (ISO). They were performed with the
ISO photometer (ISOPHOT) from 8 to 15 June 1996, when Chiron was
near perihelion at a heliocentric distance of 8.46 AU, using four
filters centered at 25, 60, 100 and 160 μ m. The observed fluxes
are fitted to a thermal model which considers a mixture of water ice
and refractory materials on the surface and includes heat conduction
into the interior of the nucleus. We derive a thermal inertia of 10
JK<SUP>-1</SUP>m<SUP>-2</SUP>s<SUP>-1/2</SUP>. Combining the present IR
data with visible observations by Luu (1990) and Marcialis (1993), we
determine a radius of 80+/-10 km and a geometric albedo of 0.14+/-0.02.
---------------------------------------------------------
Title: Observation of the origin of CMEs in the low corona
Authors: Delannée, C.; Delaboudinière, J. -P.; Lamy, P.
2000A&A...355..725D Altcode:
The aim of the main observing program with EIT on board SOHO,
is to monitor the whole Sun surface in the Fe xii emission line
at 195 Ä, every 17 minutes. The very beginning of some CMEs can
be observed. We interpret Fe xii images in conjunction with He ii,
Hα and coronagraph observations over a period of 6 days. We find
that 7 prominences produced ejections. An active region produced 9
ejections. Five ejections are seen as dark bubbles propagating above
the solar limb while 9 are seen as dimmings on the solar surface. The
3 other ejections are bright bubbles observed rising up above the
limb. Thirteen of the 17 observed ejections are related to a CME. Two
CMEs of the 15 CMEs observed with LASCO C2 are not related to Fe xii
low corona events. Probably, these CMEs have their origin behind the
limb. Prominences give rise to quite slow CMEs, 50-120 km s<SUP>-1</SUP>
while fast CMEs, 110-1000 km s<SUP>-1</SUP>, originate close to active
regions. We conclude that CMEs start in the low corona and that large
scale coronal structures reconfigurations occur when these disturbances
propagate outward.
---------------------------------------------------------
Title: Properties of coronal mass ejections: SOHO LASCO observations
from January 1996 to June 1998
Authors: St. Cyr, O. C.; Plunkett, S. P.; Michels, D. J.; Paswaters,
S. E.; Koomen, M. J.; Simnett, G. M.; Thompson, B. J.; Gurman, J. B.;
Schwenn, R.; Webb, D. F.; Hildner, E.; Lamy, P. L.
2000JGR...10518169S Altcode: 2000JGR...105.8169S; 2000JGRA..105.8169S
We report the properties of all the 841 coronal mass ejections (CMEs)
observed by the Solar and Heliospheric Observatory (SOHO) Large Angle
Spectroscopic Coronagraph (LASCO) C2 and C3 white-light coronagraphs
from January 1996 through June 1998, and we compare those properties to
previous observations by other similar instruments. Both the CME rate
and the distribution of apparent locations of CMEs varied during this
period as expected based on previous solar cycles. The distribution
of apparent speeds and the fraction of CMEs showing acceleration were
also in agreement with earlier reports. The pointing stability provided
by an L-1 orbit and the use of CCD detectors have resulted in superior
brightness sensitivity for LASCO over earlier coronagraphs; however, we
have not detected a significant population of fainter (i.e., low mass)
CMEs. The general shape of the distribution of apparent sizes for LASCO
CMEs is similar to those of earlier reports, but the average (median)
apparent size of 72° (50°) is significantly larger. The larger
average apparent size is predominantly the result of the detection of
a population of partial and complete halo CMEs, at least some of which
appear to be events with a significant longitudinal component directed
along the Sun-Earth line, either toward or away from the Earth. Using
full disk solar images obtained by the Extreme ultraviolet Imaging
Telescope (EIT) on SOHO, we found that 40 out of 92 of these events
might have been directed toward the Earth, and we compared the timing
of those with the Kp geomagnetic storm index in the days following
the CME. Although the “false alarm” rate was high, we found that 15
out of 21 (71%) of the Kp>=6 storms could be accounted for as SOHO
LASCO/EIT frontside halo CMEs. If we eliminate three Kp storms that
occurred following LASCO/EIT data gaps, then the possible association
rate was 15 out of 18 (83%).
---------------------------------------------------------
Title: Commission 21: Light of the Night Sky: (Lumiere du Ciel
Nocturne)
Authors: Bowyer, S.; Lamy, P.; Dwek, E.; Gustafson, B.; Hanner,
M.; Levasseur-Regourd, A. Ch.; Mikhail, J.; Mann, I.; Mukai, T.;
Matsumoto, T.
2000IAUTA..24..152B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: ISOCAM Observations of Cometary Nuclei
Authors: Jorda, L.; Lamy, P.; Groussin, O.; Toth, I.; A'Hearn, M. F.;
Peschke, S.
2000ESASP.455...61J Altcode: 2000ibps.conf...61J
ISOCAM images of comets C/1995 O1 (Hale-Bopp), 22P/Kopff, 46P/Wirtanen,
55P/Tempel-Tuttle, 103P/Hartley and 126P/IRAS were obtained between
7.8 and 15 microns in Oct.-Nov. 1996 and Jan.-Feb. 1998 in order to
characterize their nucleus by detecting their thermal emission. All
images were corrected for the dark current, detector non-uniformity and
transient effects with standard methods available in CIA V3.0. Further
IDL based processing is performed to correct the images from the
overshot, preserve the nuclear region from glitch removal and eliminate
images with a high percentage of glitches. The signal from the nucleus
was measured by fitting the data with a model including the contribution
from both the coma and the nucleus. By combining the thermal fluxes with
the visible fluxes, obtained with the same technique from HST images,
we derived the size and geometric albedo of three comets (C/1995 O1,
22P and 55P). For comets 103P and 126P, we only derived their size. The
radii range from 0.56 km (103P) to 56 km (C/1995 O1). The determined
geometric albedos are between 0.02 and 0.07, in agreement with previous
measurements on several other nuclei.
---------------------------------------------------------
Title: Coronal Mass Ejections and Large Scale Structure of the Corona
Authors: Maia, D.; Vourlidas, A.; Pick, M.; Howard, R.; Schwenn, R.;
Lamy, P.
2000AdSpR..25.1843M Altcode:
A comparative study of two events accompanied by both a flare and a
CME has been performed. The data analysis has been made by comparing
the observations of the LASCO/SOHO coronagraphs with those of the
Nancay radioheliograph. The observations show a clear connection
between coronal green and red line transient activity, burst radio
emission and the CME development which is due to successive loop
interactions. Signatures of these interactions are given by the radio
emission. One can identify successive sequences in the evolution
of the coronal restructuring leading to the full development of the
CME. Identification and timing of these sequences result from the radio
emission analysis. For flare-CME events , the evolution takes place
in the low corona and is extremely fast of the order, on a few minutes
---------------------------------------------------------
Title: CMEs Observed Continuously from the Lower Corona to the
Far Corona
Authors: Delannée, C.; Delaboudinière, J. -P.; Lamy, P.
2000AdSpR..26...67D Altcode:
A campaign of observations with EIT on board SOHO called “CME watch”,
is designed to observe the whole sun surface in 195 A&ring i.e. in a
Fe XII emission line, every 17 minutes. In order to analyze the events,
we also used He II and coronagraph observations of 97/11/03. By this
way, the very beginning of some CMEs was observed. The ejections
were seen in Fe XII as a dark bubble propagating in the corona
above a prominence, and dimmings produced near an active region and
propagating on the solar surface. Two of the ejections coming from
the active region were produced with a very short time of delay (1
hour). All the ejections were associated to a CME. However, one CME
was not related to a Fe xII low corona event, but maybe this CME had
its origin behind the limb. The CME associated with the prominence
was quite slow (50 km s<SUP>-1</SUP>) and the ones associated with
the active region were quite fast (114-490 km s<SUP>-1</SUP>). This
analysis permitted a better identification of the different CMEs
appearing in the coronagraph field of view
---------------------------------------------------------
Title: Eclipse of August 11, 1999: White-light Images and Simultaneous
EIT/SOHO Observations
Authors: Adjabshirizadeh, A.; Baudin, F.; Bocchialini, K.;
Delaboudinière, J. -P.; Grorod, P. -A.; Koutchmy, S.; Laal Aaly,
M.; Lamy, P.; Lochard, J.; Mouette, J.
1999ESASP.448.1283A Altcode: 1999ESPM....9.1283A; 1999mfsp.conf.1283A
No abstract at ADS
---------------------------------------------------------
Title: The Global Activity of the Solar Corona
Authors: Llebaria, A.; Lamy, P.; Koutchmy, S.
1999ESASP.446..441L Altcode: 1999soho....8..441L
The question of the global activity of the solar corona, as a function
of time and distance from the center of the Sun, is considered by
analyzing long time-series of LASCO-C2 images. Polarized images
are first considered to perform the separation of the K and F
components. The F-corona images are used to construct a photometric
model of the F-corona wich reflects its annual variations resulting from
geometric effects. This time-varying model is then subtracted from all
corrected and calibrated images (unpolarized) to yield images of the
K-corona. Synoptic maps are created at different distances between 2.5
and 6 solar radii and the total white-light intensity is integrated to
estimate the total mass of the corona. Its variations in the range of
heliocentric distance and over a time span of 3 years will be presented
and discussed.
---------------------------------------------------------
Title: Monolithic SiC telescope of the OSIRIS Narrow-Angle Camera
for the cometary mission ROSETTA
Authors: Castel, Didier; Calvel, Bertrand; Lamy, Philippe L.; Dohlen,
Kjetil; Bougoin, Michel
1999SPIE.3785...56C Altcode:
The international Rosetta mission, now planned by ESA to be launched
in January 2003, will provide a unique opportunity to directly study
the nucleus of comet 46P/Wirtanen and its activity from a heliocentric
distance of 3.2 AU to the perihelion passage at 1.06 AU in July 2013. We
describe here the design, the development and the performances of
the telescope of the Narrow Angle Camera of the OSIRIS experiment
which will give high resolution images of the cometary nucleus in the
visible spectrum.
---------------------------------------------------------
Title: Simultaneous LASCO/1998-Eclipse Observations Of A Large-Scale
Polar Event
Authors: Zhukov, A.; Koutchmy, S.; Lamy, Ph.; Delaboudinière,
J. -P.; Delannée, C.; Bocchialini, K.; Guisard, S.; Filippov, B.;
Veselovsky, I.
1999ESASP.446..731Z Altcode: 1999soho....8..731Z
A relatively faint but large scale polar region event was observed
in Aug. 1996 by Boulade et al. 1998 (SoHO SP 404, 217); we first
reconsider this event which has been related to a high latitude
filament disappearance. We continue the study of this class of events by
analyzing the large scale restructuring which occurred above the N-Pole
region at the time of the last Feb. 26, 1998 total solar eclipse. Well
calibrated WL-eclipse images are used to provide the absolute values
of electron densities of the quasi-radial structure appearing at
the feet of the event. This structure can also be considered as a
type of abnormally broad and curved polar plume, a type of activity
already reported in the literature. Unfortunately, the examination
of sequences of EIT images taken at that time seems to indicate that
the roots of the structure are on the back side of the Sun. However
the most impressive effects are seen in the high polar region, at
several radii, based on the analysis of processed Lasco-C2 difference
images. Large proper motions are deduced over density structures. Both
these events confirm that polar regions are indeed showing a new class
of CME activity (possibly related to the Hewish's CMEs), which is seen
inside coronal holes. A whole set of interesting questions is then
appearing to understand the occurrence of a polar CME propagating in
the heart of a large unipolar magnetic region of the corona.
---------------------------------------------------------
Title: Characterization of the nucleus of comet Hale-Bopp from HST
and ISO observations
Authors: Lamy, P.; Jorda, L.; Toth, I.; Groussin, O.; A'Hearn, M. F.;
Weaver, H. A.
1999DPS....31.2703L Altcode:
High resolution images were obtained in the visible with the Planetary
Camera of the Hubble Space Telescope and "B,V,R" filters and in the
thermal infrared with ISOCAM and from filters centered at 7.75, 9.62,
11.4 and 15.0 micron. The latter images were carefully processed to
independently correct for the temporal evolution of the signal in each
pixel. Using our standard technics, we separated the nuclear and comatic
contributions to retrieve the flux from the nucleus. Two thermal models
were used to interpret the infrared fluxes, the Standard Thermal Model
(STM) and a mixed ice-dust model. Combining the visible and thermal
data, the STM model suggests a body with a radius of 35+/-6 km with
an albedo of 0.05+/-0.02 and a maximum temperature of 254 K while the
mixed model indicates a larger radius 52+/-5 km and a lower maximum
temperature of 192 K. The spectral energy distribution is best fit
with the mixed ice-dust model with an excess at 10 micron attributed
to the silicate band.
---------------------------------------------------------
Title: The sungrazing comets discovered with the SOHO/LASCO
coronagraphs: 1996-1998.
Authors: Biesecker, D. A.; Lamy, P.; St. Cyr, O. C.; Llebaria, A.;
Howard, R.
1999DPS....31.1404B Altcode:
An unprecedented number of Kreutz sungrazing comets have been discovered
with the LASCO coronagraphs on the SOHO spacecraft. We present here
the results of the analysis of the first 53 sungrazing comets, which
were discovered between January, 1996 and June, 1998. In this poster, we
summarize the capabilities and calibration of the LASCO coronagraphs for
comet observations. We discuss the frequency of the comet discoveries
and summarize the properties of the computed orbits. We show examples
of typical comet light curves and discuss their common features. In
particular, we show that the comets are completely disintegrated before
they reach perihelion. One particular feature of the observations is
the presence of a dust tail for only a few sungrazers while no tail
is evident for the majority of them. Analysis of the light curves is
used to investigate the properties of the nuclei (size, fragmentation,
destruction) and the dust production rates. This work was funded in
part by NASA SOHO-GI Grant NAG5-8003.
---------------------------------------------------------
Title: The sungrazing comets discovered with the SOHO/LASCO
coronagraphs: 1996-1998.
Authors: Biesecker, D. A.; Lamy, P.; St. Cyr, O. C.; Llebaria, A.;
Howard, R.
1999BAAS...31.1094B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Experiments for in-situ monitoring of dust environments in
the Solar System
Authors: Colangeli, L.; Bussoletti, E.; Lopez Moreno, J. J.; Epifani,
E.; Esposito, F.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi,
A.; Vergara, S.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.;
Morales, R.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez,
J. F.; Ruiz-Falco, A.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.;
Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.;
Angrilli, F.; Coradini, A.; Giovane, F.; Gruen, E.; Gustafson, B.;
Maag, C.; Weissman, P. R.
1999DPS....31.2906C Altcode:
"Dust" is present in the Solar System, from planetary surfaces
to comets. The in-situ monitoring of its physical and dynamical
properties is one of the main scientific tasks to be achieved in order
to characterise grains and to correctly understand their role in the
evolution of Solar System bodies. A new generation of methods for
in-situ exploration of dusty environments in the Solar System has been
studied and adopted in different instruments under development or study
for future planetary space missions. Mass flux measurements by quartz
crystal microbalances, optical detection of single grains and momentum
monitoring by piezoelectric transducers are techniques which provide
high sensitivity for grains at relatively low (below some hundreds m/s)
velocities. The GIADA (Grain Impact Analyser and Dust Accumulator)
experiment is part of the payload of the ESA Rosetta orbiter, targeted
to a rendez-vous of 46P/Wirtanen comet. Thanks to GIADA, one of the
prime scientific objectives of the mission will be fulfilled, i.e. the
monitoring of the cometary coma dust environment. The dust flux from
different directions vs. time and the momentum and velocity vs. mass
of particles will be measured, while comet will approach the Sun. The
MAGO (Martian Atmospheric Grain Observer) instrument, under study in
the framework of the next Mars exploration opportunities (e.g.: Mars
Surveyor Program 2003) adopts similar technical solutions and is aimed
at measuring, directly for the first time, the dust mass flux in the
Martian atmosphere and the dynamical properties of airborne particles
vs. time. Finally, similar measurement techniques can be integrated with
other detection/collection systems (e.g. aerogel collectors) to monitor
the dust in the near Earth environment, e.g. from the space station.
---------------------------------------------------------
Title: Characterization of the nucleus of comet Hale-Bopp from HST
and ISO observations.
Authors: Lamy, P.; Jorda, L.; Toth, I.; Groussin, O.; A'Hearn, M. F.;
Weaver, H. A.
1999BAAS...31.1116L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hubble Space Telescope Observations of the Nucleus of Comet
45P/Honda-Mrkos-Pajdusakova and Its Inner Coma
Authors: Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Weaver, H. A.
1999Icar..140..424L Altcode:
The nucleus of Comet 45P/Honda-Mrkos-Pajdusakova was detected during
Hubble Space Telescope observations taken with the Wide-Field Planetary
Camera 2 (WFPC2) in February 1996 when the comet was 0.17 AU from the
Earth. The high spatial resolution (1 pixel projected to 5.6 km at
the distance of the comet) allowed us to separate the signal of the
nucleus from that of the coma, and images taken through five broadband
filters allowed us to determine the UBVRI magnitudes of the nucleus
in the Johnson-Kron-Cousins photometric system (sometime known as the
Landolt system). Assuming a spherical body whose geometric albedo
is 0.04 for the V band and a phase coefficient of 0.04 mag/deg, we
derive an effective radius of 0.34 km. The uncertainty is dominated
by the unknown phase law; the radius may be as small as 0.22 km if
the phase coefficient is 0.03 mag/deg. The correlated variations of
the magnitudes over 1 day suggest an elongated body with an axis
ratio of at least 1.3. The strong reddening of the nucleus in the
ultraviolet progressively decreases, and its color tends to neutral
in the near infrared. We also derive a fractional active area of 11%
and a dust production rate of 1.0 kg s<SUP>-1</SUP> (86 metric tons
day<SUP>-1</SUP>).
---------------------------------------------------------
Title: Streamer disconnection events observed with the LASCO
coronagraph
Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Howard, R. A.; Rich,
N. B.; Lamy, P. L.
1999GeoRL..26.1349W Altcode:
We present Large Angle Spectrometric Coronagraph (LASCO) observations
of two events that suggest magnetic disconnection in coronal
streamers. During the 1-2 days preceding each event, successions of
narrow looptops are seen rising slowly through the 2-6 R<SUB>S</SUB>
field of view, forming a bright streamer stalk which continues to
elongate with time. As the streamer becomes ever more constricted, it
eventually severs at a heliocentric distance of ∼4 R<SUB>S</SUB>. The
lower part of the stalk collapses back to form a cusplike structure
extending to ∼3 R<SUB>S</SUB>, while the disconnected segment is
observed as a kink or density enhancement that propagates outward with
a speed of order 200 km s<SUP>-1</SUP>. We interpret these non-CME
events as transient openings and closings of magnetic flux rooted at
the boundaries of coronal holes.
---------------------------------------------------------
Title: Influence of image compression on the in situ stereoscopic
reconstruction of a cometary surface for the ROSETTA mission.
Authors: Takerkart, S.; Lamy, P.; Llebaria, A.
1999CRASB.327..547T Altcode:
As part of the ROSETTA mission, the surface science package, wich will
land on the nucleus of the comet 46P/Wirtanen, includes a stereoscopic
imaging instrument CIVA-P. The data volume required by the scientific
objectives and the limited capability of the telemetry imposes the
use of image-loss compression techniques. The authors study the
influence of the losses due to compression on the three-dimensional
surface reconstruction. They prove that the best strategy consists
in compressing both the left and right images with the same ratio,
transmitting them and finally applying on Earth the stereoscopic
calculation on the decompressed images.
---------------------------------------------------------
Title: ISOPHOT observations of comet Hale-Bopp: initial data reduction
Authors: Grun, E.; Peschke, S. B.; Stickel, M.; Muller, T. G.; Kruger,
H.; Bohmhardt, H.; Brooke, T. Y.; Campins, H.; Crovisier, J.; Hanner,
M. S.; Heinrichsen, I.; Keller, H. U.; Knacke, R.; Lamy, P.; Leinert,
C.; Lemke, D.; Lisse, C. M.; Muller, M.; Osip, D. J.; Solc, M.; Sykes,
M.; Vanysek, V.; Zarnecki, J.
1999ESASP.427..181G Altcode: 1999usis.conf..181G; 1998astro.ph.12171G
Comet Hale-Bopp was observed five times with ISOPHOT, the photometer
on board the Infrared Space Observatory (ISO). Each time broadband
photometry was performed using 4 different detectors, 5 apertures and,
10 filters covering the range between 3.6 to 175 μm. Calibration
measurements using the internal Fine Calibration Source were done
together with each individual measurement. Background observations were
performed with identical instrument settings at the same positions on
the sky several days after the comet observations. The observation
strategy and the initial data reduction steps are described in
some detail and the resulting in-band power values of the Hale-Bopp
observations and their uncertainties are derived. Initial reduction
of these measurements was performed in 3 steps: (1) processing of
raw data by removing instrumental and energetic particle effects,
(2) averaging of the individual signals, and (3) determination of the
detector responsivities and their uncertainties. The detector signal is
determined by two different methods and the best value is chosen. At the
present level of processing uncertainties range from 10% to a factor
of 3 for the low power levels at short wavelengths. The in-band power
levels at different wavelengths varied over 3 orders of magnitude.
---------------------------------------------------------
Title: LASCO observations of the coronal rotation
Authors: Lewis, D. J.; Simnett, G. M.; Brueckner, G. E.; Howard,
R. A.; Lamy, P. L.; Schwenn, R.
1999SoPh..184..297L Altcode:
The near-rigid rotation of the corona above the differential rotation
of the photosphere has important implications for the form of the
global coronal magnetic field. The magnetic reconfiguring associated
with the shear region where the rigidly-rotating coronal field lines
interface with the differentially-rotating photospheric field lines
could provide an important energy source for coronal heating. We present
data on coronal rotation as a function of altitude provided by the Large
Angle Spectrometric Coronagraph (LASCO) instrument aboard the Solar and
Heliospheric Observatory (SOHO) spacecraft. LASCO comprises of three
coronagraphs (C1, C2, and C3) with nested fields-of-view spanning 1.1
R⊙ to 30 R⊙. An asymmetry in brightness, both of the Fe xiv emission
line corona and of the broad-band electron scattered corona, has been
observed to be stable over at least a one-year period spanning May
1996 to May 1997. This feature has presented a tracer for the coronal
rotation and allowed period estimates to be made to beyond 15 R⊙,
up to 5 times further than previously recorded for the white-light
corona. The difficulty in determining the extent of differential motion
in the outer corona is demonstrated and latitudinally averaged rates
formed and determined as a function of distance from the Sun. The
altitude extent of the low latitude closed coronal field region is
inferred from the determined rotation periods which is important to the
ability of the solar atmosphere to retain energetic particles. For the
inner green line corona (<2 R⊙) we determine a synodic rotation
period of (27.4±0.1) days, whereas, for the outer white- light corona,
(>2.5 R⊙) we determine a rotation period of (27.7±0.1) days.
---------------------------------------------------------
Title: Time Domain Analysis of Solar Coronal Structures Through
Hough Transform TEC hniques
Authors: Llebaria, A.; Lamy, P.
1999ASPC..172...46L Altcode: 1999adass...8...46L
The Hough transform technique is applied to a series of images
from the LASCO/C2 coronagraph in order to understand the temporal
evolution of radial structures on the solar corona, the so-called
“polar plumes”. They may corotate with the solar corona and therefore
change aspect with time due to projection effects on the plane of the
sky. In the images these structures suddenly appear, shift, mix, and
fade away on short periods of time. >From a long series of images
(~100), we determined for each image the polar intensity profile and
built up the evolution of such profiles against time. The result is
a Time Intensity Diagram (TID) where intensities are plotted with
respect to time and position coordinates. Radial structures appear as
peak intensities in each profile and therefore as bright points in the
TID. The Hough transform techniques are applied to detect coherent
trajectories. This technique has been applied successfully to study
coronal plumes on coronal images obtained by different instruments
aboard the SOHO satellite.
---------------------------------------------------------
Title: The GIADA Experiment for Rosetta Mission to Comet 46P/Wirtanen:
Design and Performances
Authors: Bussoletti, E.; Colangeli, L.; Lopez Moreno, J. J.; Epifani,
E.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.;
Girela, F.; Herranz, M.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina,
A.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.;
Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot,
S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Benini,
E.; Casini, L.; Cherubini, G.; Coradini, A.; Giovane, F.; Grün, E.;
Gustafson, B.; Maag, C.; Weissmann, P. R.
1999AdSpR..24.1149B Altcode:
Rosetta is one of the most ambitious missions planned by ESA for
the beginning of the next millennium. It will explore from very
close a comet nucleus along its trajectory up to perihelion. In the
instrument complex forming the scientific payload, the GIADA (Grain
Impact Analyser and Dust Accumulator) experiment is devoted to study
the cometary dust flux evolution and grain dynamic properties. To
achieve the required performances and the expected scientific return,
GIADA has been designed as a multi-sensor instrument. It is able to
detect grain passage by laser light scattering measurement, particle
momentum through piezoelectric transducers and mass flux by means of
quartz crystal microbalances. In this paper we describe the technical
solutions and performances which have been reached on the development
models of GIADA
---------------------------------------------------------
Title: Preface
Authors: Lamy, Philippe; Thomas, Nicolas
1999AdSpR..24.1079L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The panoramic camera of the ROSETTA mission: performances of
prototype 3D microcameras
Authors: Beauvivre, S.; Lamy, P.; Nguyen-Trong, T.; Reynaud, J. -L.
1999AdSpR..24.1105B Altcode:
We present the evaluation of the performances of microcameras prototypes
manufactured in 3D packaging technology developed for the panoramic
camera of the lander for the ROSETTA cometary mission. Two different
prototypes were tested, one manufactured by Alcatel and the other
by CSEM. A specific laboratory setup with cooling capabilities was
implemented to perform electrical, mechanical and photometric tests
in the temperature range -90°C to +20°C. Our results show that
the photometric performances are nominal and do not change in this
temperature range. The reduced size of the camera, associated with
its operating mode, leads to a transient thermal behaviour that does
not affect the cameras properties when operated at temperatures below
-55°C. We show that this kind of miniature camera is suitable to deep
space missions like ROSETTA, provided specific cares are taken in the
electrical and mechanical designs.
---------------------------------------------------------
Title: The GIADA experiment for ROSETTA mission to comet 46P/wirtanen:
Design and performances
Authors: Bussoletti, E.; Colangeli, L.; Lopez Moreno, J. J.; Epifani,
E.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.;
Girela, F.; Herranz, M.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina,
A.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.;
Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot,
S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Benini,
E.; Casini, L.; Cherubini, G.; Coradini, A.; Giovane, F.; Grün, E.;
Gustafson, B.; Maag, C.; Weissmann, P. R.
1999AdSpR..24.1139B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Exploration of small bodies in the solar system: I. Initial
results and future prospects : proceedings of the B1.1 Symposium of
COSPAR Scientific Commission B which was held during the Thirty-second
COSPAR Scientific Assembly, Nagoya, Japan, 12-19 July, 1998
Authors: Lamy, P. L.; Thomas, N.
1999AdSpR..24.....L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Experiments for in-situ monitoring of dust environments in
the Solar System.
Authors: Colangeli, L.; Bussoletti, E.; López-Moreno, J. J.; Epifani,
E.; Esposito, F.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi,
A.; Vergara, S.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.;
Morales, R.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez,
J. F.; Ruiz-Falco, A.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.;
Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.;
Angrilli, F.; Coradini, A.; Giovane, F.; Gruen, E.; Gustafson, B.;
Maag, C.; Weissman, P. R.
1999BAAS...31R1119C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: CME observed continuously from the lower corona to the far
corona (CME's onset on November 3, 1997).
Authors: Delannée, C.; Delaboudinière, J. -P.; Lamy, P.
1999joso.proc..162D Altcode:
A program of observations with EIT on board SOHO, is to observe the
whole sun surface in 195 Å, i.e. in a Fe XII emission line, every
17 minutes. The very beginning of some CMEs is observed. The authors
correlate each Fe XII observation with He II, Hα and coronagraph
observations on 97/11/03 and 97/11/04. They found that three prominences
were ejected, and that an active region produced 4 ejections. The
ejections are dark bubbles propagating above the sun limb, and dimmings
propagating on the solar surface in Fe XII. They each produced an
associated CME. One CME was not correlated to a Fe XII low corona
event. Maybe, this CME had its origin behind the limb. The prominence
gave a quite slow CME, i.e. about 50 km s<SUP>-1</SUP> and the active
region produced some quite fast CMEs, i.e. about 300 km s<SUP>-1</SUP>.
---------------------------------------------------------
Title: Hubble Space Telescope observations of the nucleus and inner
coma of comet 19P/1904 Y2 (Borrelly)
Authors: Lamy, Philippe L.; Toth, Imre; Weaver, Harold A.
1998A&A...337..945L Altcode:
The nucleus of comet 19P/Borrelly was detected using the Planetary
Camera (WFPC2) of the Hubble Space Telescope (HST). During the time
of our observations, the comet was 0.62 AU from the Earth, 1.40 AU
from the Sun, and had a solar phase angle of 38°. The high spatial
resolution of the HST images allowed us to discriminate clearly between
the signal from the nucleus and that from the coma. The lightcurve
of the nucleus indicates that it is a highly elongated body rotating
with a synodic period of 25.0+/-0.5 hr. Assuming that the nucleus has
a geometric albedo of 4% and is a prolate spheroid with a rotational
axis pointing in the direction determined by Sekanina (1979), we
derive that its semi-axes are 4.4+/-0.3 km and 1.8+/-0.15 km. The
corresponding fractional active area of $() sim$8 {%} suggests a
moderately active comet. The highly anisotropic coma is dominated by
a strong sunward fan, and the dust production rate exhibited signs of
temporal variability throughout our observations. Based on observations
made with the NASA/ESA Hubble Space Telescope, obtained at the Space
Telescope Science Institute, which is operated by the Association of
Universities for Research in Astronomy, under NASA contract NAS 5-26555
---------------------------------------------------------
Title: Joint Nancay Radioheliograph and LASCO Observations of Coronal
Mass Ejections - II. The 9 July 1996 Event
Authors: Pick, M.; Maia, D.; Kerdraon, A.; Howard, R.; Brueckner,
G. E.; Michels, D. J.; Paswaters, S.; Schwenn, R.; Lamy, P.; Llebaria,
A.; Simnett, G.; Lanzerotti, L. J.; Aurass, H.
1998SoPh..181..455P Altcode:
The development of a coronal mass ejection on 9 July 1996 has been
analyzed by comparing the observations of the LASCO/SOHO coronagraphs
with those of the Nancay radioheliograph. The spatial and temporal
evolution of the associated radioburst is complex and involves a
long-duration continuum. The analysis of the time sequence of the
radio continuum reveals the existence of distinct phases associated
with distinct reconnection processes and magnetic restructuring
of the corona. Electrons are accelerated in association with these
reconnection processes. An excellent spatial association is found
between the position and extension of the radio source and the CME seen
by LASCO. Furthermore, it is shown that the topology and evolution
of the source of the radio continuum involve successive interactions
between two systems of loops. These successive interactions lead to
magnetic reconnection, then to a large scale coronal restructuring. Thus
electrons of coronal origin may have access to the interplanetary
medium in a large range of heliographic latitudes as revealed by the
Ulysses observations.
---------------------------------------------------------
Title: Comet 9P/Tempel 1
Authors: Lamy, P.
1998IAUC.7000....3L Altcode: 1998IAUC.7000C...1L; 1998IAUC.7000S...1L
P. Lamy, Laboratoire d'Astronomie Spatiale, and his team report the
detection of the nucleus of comet 9P with the Hubble Space Telescope
(+ WFPC2) on 1997 Dec. 31 at Delta = 3.53 AU and r = 4.48 AU: "The
slightly incomplete lightcurve indicates an elongated body having
semi-axes a = 3.9 and b = 2.8 km (assuming a geometric albedo of 0.04)
and a rotational period of about 25 hr. No coma was detected."
---------------------------------------------------------
Title: Geomagnetic storms caused by coronal mass ejections (CMEs):
March 1996 through June 1997
Authors: Brueckner, G. E.; Delaboudiniere, J. -P.; Howard, R. A.;
Paswaters, S. E.; St. Cyr, O. C.; Schwenn, R.; Lamy, P.; Simnett,
G. M.; Thompson, B.; Wang, D.
1998GeoRL..25.3019B Altcode:
(1) All but two geomagnetic storms with Kp ≥ 6 during the operating
period (March 1996 through June 1997) of the Large Angle Spectroscopic
Coronagraph (LASCO) experiment on the Solar and Heliospheric Observatory
(SOHO) spacecraft can be traced to Coronal Mass Ejections (CMEs). (2)
These geomagnetic storms are not related to high speed solar wind
streams. (3) The CMEs which cause geomagnetic effects, can be classified
into two categories: Halo events and toroidal CMEs. (4) The CMEs are
accompanied by Coronal Shock Waves as seen in the Extreme Ultraviolet
Imaging Telescope (EIT) Fe XII images. (5) Some CMEs are related to
flares, others are not. (6) In many cases, the travel time between
the explosion on the Sun and the maximum geomagnetic activity is about
80 hours.
---------------------------------------------------------
Title: The Solar Minimum Active Region 7978, Its X2.6/1B Flare, CME,
and Interplanetary Shock Propagation of 9 July 1996
Authors: Dryer, M.; Andrews, M. D.; Aurass, H.; DeForest, C.; Galvin,
A. B.; Garcia, H.; Ipavich, F. M.; Karlický, M.; Kiplinger, A.;
Klassen, A.; Meisner, R.; Paswaters, S. E.; Smith, Z.; Tappin,
S. J.; Thompson, B. J.; Watari, S. I.; Michels, D. J.; Brueckner,
G. E.; Howard, R. A.; Koomen, M. J.; Lamy, P.; Mann, G.; Arzner, K.;
Schwenn, R.
1998SoPh..181..159D Altcode:
The first X-class flare in four years occurred on 9 July 1996. This
X2.6/1B flare reached its maximum at 09:11 UT and was located in active
region 7978 (S10° W30°) which was an old-cycle sunspot polarity
group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before
and after this event together with Yohkoh SXT images of the flare,
radio observations of the type II shock, and GOES disk-integrated soft
X-ray flux during an extended period that included energy build-up in
this active region.
---------------------------------------------------------
Title: The nucleus and inner coma of Comet 46P/Wirtanen
Authors: Lamy, P. L.; Toth, I.; Jorda, L.; Weaver, H. A.; A'Hearn, M.
1998A&A...335L..25L Altcode:
We report the detection of the nucleus of comet 46P/Wirtanen from
analysis of images taken with the Planetary Camera (WFPC2) of the Hubble
Space Telescope (HST) on 28 August 1996. The high spatial resolution
(a WFPC2 pixel projects to 50 km at the distance of the comet) allowed
us to separate the signal of the nucleus from that of the coma and to
determine the Landolt V and R magnitudes of the nucleus. Assuming a
spherical body with a geometric albedo of 0.04 and a phase coefficient
of 0.04 mag/deg, we derived a radius of 0.60+/-0.02 km. The color of the
nucleus is moderately red with a gradient of 10{%} per 1000 Angstroms at
optical wavelengths. From the lightcurve data we derived a rotational
period of 6.0+/-0.3 hr and find that the ratio of the semi-axes of the
assumed ellipsoidal body must satisfy a/b >= 1.2. From an analysis
of the dust coma, we derived that Afrho is 23 cm and that the dust
production rate is 4 kg sec(-1) . Based on observations made with the
NASA/ESA Hubble Space Telescope, obtained at Space Telescope Science
Institute, which is operated by the Association of Universities for
Research in Astronomy under NASA contract NAS 5-26555
---------------------------------------------------------
Title: Joint Nançay Radioheliograph and LASCO Observations of
Coronal Mass Ejections - I. The 1 July 1996 Event
Authors: Maia, D.; Pick, M.; Kerdraon, A.; Howard, R.; Brueckner,
G. E.; Michels, D. J.; Paswaters, S.; Schwenn, R.; Lamy, P.; Llebaria,
A.; Simnett, G.; Aurass, H.
1998SoPh..181..121M Altcode:
The development of a coronal mass ejection on 1 July 1996 has been
analyzed by comparing the observations of the LASCO/SOHO coronagraph
with those of the Nançay radioheliograph. This comparison brings new
insight and very useful diagnosis for the study of CME events. It
is shown that the initial instability took place in a small volume
located above an active region and that the occurrence of short radio
type III bursts implies a triggering process due to magnetic field
interactions. The subsequent spatial and temporal evolution of the
radio emission strongly suggests that the large scale structure becomes
unstable within the first minute of the event.
---------------------------------------------------------
Title: LASCO observations of an Earth-directed coronal mass ejection
on May 12, 1997
Authors: Plunkett, S. P.; Thompson, B. J.; Howard, R. A.; Michels,
D. J.; St. Cyr, O. C.; Tappin, S. J.; Schwenn, R.; Lamy, P. L.
1998GeoRL..25.2477P Altcode:
Coronal mass ejections (CMEs) that occur near the center of the
solar disk are most likely to impact Earth. Detection of such
events as ‘halos’ in white-light coronagraphs has been somewhat
controversial in recent years. We present observations from the LASCO
coronagraphs on SOHO that provide convincing evidence of the detection
of an Earth-directed CME on May 12, 1997. The event began at about
04:35 UT and propagated outwards from the Sun with a projected speed
of around 250 km s<SUP>-1</SUP>. Using some reasonable assumptions
about the geometry of the CME, we estimate the true speed to be around
600 km s<SUP>-1</SUP>. The onset of the event in LASCO is coincident
(to within measurement uncertainties) with an eruptive event detected
in extreme ultraviolet observations of the solar disk by the SOHO
EIT. This is the first reported observation of a halo CME at projected
distances greater than 10 R<SUB>⊙</SUB>, with a clearly identifiable
solar origin. We discuss the possibility that at least some of the
enhanced brightness observed by LASCO may be due to a compressional
wave propagating in the corona.
---------------------------------------------------------
Title: Space exploration of the outer space solar system and cometary
nuclei. Proceedings. B0.2 and B0.6 Symposia of COSPAR Scientific
Commission B held during the Thirty-first COSPAR Scientific Assembly,
Birmingham (UK), 14 - 21 Jul 1996.
Authors: Matson, D. L.; Thomas, N.; Lamy, P.
1998AdSpR..21.....M Altcode:
This is a collection of six papers. Current and planned exploration
activities for the giant planets, Jupiter and Saturn are discussed. The
volume starts with an account of the results of the mass spectrometer
measurements of the Jovian atmosphere. This is a key result from
the instrumented probe which the Galileo spacecraft delivered to
Jupiter. Next are results of measurements on the location of the Jovian
magnetopause and bow shock. Then, several theoretical investigations
explore effects in the magnetospheres of Jupiter and Saturn. Finally,
data from the Pioneer and Voyager spacecraft are used to model some
of the properties of energetic electrons in the Saturnian magnetosphere.
---------------------------------------------------------
Title: Origin of Streamer Material in the Outer Corona
Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Walters, J. H.; Brueckner,
G. E.; Howard, R. A.; Michels, D. J.; Lamy, P. L.; Schwenn, R.;
Simnett, G. M.
1998ApJ...498L.165W Altcode:
We investigate the nature and origin of the outward-moving density
inhomogeneities (“blobs”) detected previously with the Large Angle and
Spectrometric Coronagraph on the Solar and Heliospheric Observatory. The
blobs are concentrated around the thin plasma layer that surrounds
the heliospheric current sheet and that constitutes the outer streamer
belt; they represent only a small, fluctuating component of the total
density within the plasma sheet. As noted before in Sheeley et al.,
blobs are characterized by low speeds and are continually emitted
from the elongated tips of helmet streamers at 3-4 R<SUB>solar</SUB>
from Sun center. We suggest that both the blobs and the plasma sheet
itself represent closed-field material injected into the solar wind as
a result of footpoint exchanges between the stretched helmet-streamer
loops and neighboring open field lines. The plasma sheet is thus
threaded by newly reconnected, open magnetic field lines, which lend
the white-light streamer belt its filamentary appearance. Since in
situ observations at 1 AU show that the slow wind (with speeds below
500 km s<SUP>-1</SUP>) spreads over an angular extent much greater
than the <~3° width of the plasma sheet, we deduce that a major
component of this wind must originate outside the helmet streamers
(i.e., from just inside coronal holes).
---------------------------------------------------------
Title: Comet 55P/Tempel-Tuttle
Authors: Lamy, P.; Znojil, V.; Biver, N.
1998IAUC.6851....2L Altcode: 1998IAUC.6851R...1L; 1998IAUC.6851B...1L
P. Lamy, Laboratoire d'Astronomie Spatiale, and his team report the
detection of the nucleus of comet 55P with the Hubble Space Telescope
(+ WFPC2) on Jan. 9 at Delta = 0.46 AU: "After removing the faint
contribution of the coma to the central pixels, the magnitude of
the nucleus was R = 16.62, showing no variation over 10 hr. For a
geometric albedo of 0.04 and a phase coefficient of 0.04 mag/deg,
the mean effective radius is 1.8 km, the largest uncertainty coming
from the phase law. The red color of the nucleus is characterized
by a normalized reflectivity gradient of 0.16 percent/nm." Visual
m_1 estimates: Mar. 1.75 UT, 8.7 (V. Znojil, Brno, Czech R., 25x100
binoculars); 18.24, 9.7: (N. Biver, Honolulu, HI, 0.26-m reflector).
---------------------------------------------------------
Title: Discrimination of point-like objects in astronomical images
using surface curvature.
Authors: Llebaria, A.; Lamy, P.; Malburet, P.
1998A&AS..127..587L Altcode:
We present a method for the discrimination of point-like objects in
astronomical images using surface curvature. The principal curvatures
k_1 and k_2 are calculated using a local quadric approximation to the
log of the intensity of the original image. The analysis of the (k_1,
k_2) diagram allows to easily separate various shapes and to establish
a criterion for discrimination. A mask is then generated and the
invalid pixels are replaced by a local, pyramidal interpolation using
a non-linear, multiresolution method. We present two applications,
the discrimination and removal of stars from the dust tail of comet
P/Halley observed while it was crossing the Milky Way, and the removal
of cosmic ray impacts from images of the solar corona obtained with
a space-coronagraph.
---------------------------------------------------------
Title: Reconstruction of the Electron Density Distribution in the
Solar Corona Based on LASCO C2 Observations
Authors: Gabryl, J. -R.; Cugnon, P.; Lamy, P.
1998ASPC..155..361G Altcode: 1998sasp.conf..361G
No abstract at ADS
---------------------------------------------------------
Title: DFA-the dust flux analyzer for the Rosetta orbiter
Authors: Lamy, P.; Perruchot, S.; Reynaud, J. -L.; Leese, M. R.;
McDonnell, J. A. M.; Green, S. F.; Busoletti, E.; Colangeli, L.;
Fulle, M.; Rotundi, A.; Giovane, F.; Gustafson, B.; Perrin, J. -M.
1998AdSpR..21.1557L Altcode:
We describe the scientific objectives, the design concept and the
implementation of the Dust Flux Analyser (DFA) for the ESA Rosetta
mission. DFA is designed to detect individual dust particles in order
to study their physical and dynamical properties as a function of
time and of orbital position, to monitor the spatial distribution
of the dust production and correlate it with the nucleus emission
sites and to analyse gas-dust interactions and the evolution of the
coma. The instrument is composed of three detectors with a common
electronic box. The Velocity Measurement System (VMS) will measure
the velocity of the incoming dust particles and the dust detector
(MOM), its momentum. A separate deposition system (DEP) composed of
three quartz microbalances will monitor the cometary dust flux in three
directions. DFA will be able to detect dust particles in the size range
5-1000 μm and velocity range 0.1-150 m.s^-1. Required resources are
a mass of 4.9 kg, a power of 3.6 W to 16.7 W and a telemetry of 50 to
512 kBits per hour depending upon the operating modes.
---------------------------------------------------------
Title: OSIRIS-the optical, spectroscopic and infrared remote imaging
system for the Rosetta Orbiter
Authors: Thomas, N.; Keller, H. U.; Arijs, E.; Barbieri, C.; Grande,
M.; Lamy, P.; Rickman, H.; Rodrigo, R.; Wenzel, K. -P.; A'Hearn,
M. F.; Angrilli, F.; Bailey, M.; Barucci, M. A.; Bertaux, J. -L.;
Brieß, K.; Burns, J. A.; Cremonese, G.; Curdt, W.; Deceuninck, H.;
Emery, R.; Festou, M.; Fulle, M.; Ip, W. -H.; Jorda, L.; Korth, A.;
Koschny, D.; Kramm, J. -R.; Kührt, E.; Lara, L. M.; Llebaria, A.;
Lopez-Moreno, J. J.; Marzari, F.; Moreau, D.; Muller, C.; Murray,
C.; Naletto, G.; Nevejans, D.; Ragazzoni, R.; Sabau, L.; Sanz, A.;
Sivan, J. -P.; Tondello, G.
1998AdSpR..21.1505T Altcode:
The scientific objectives, design, and implementation of the Optical,
Spectroscopic, and Infrared Remote Imaging System (OSIRIS) for the
International Rosetta Mission are described. The instrument comprises
two camera systems with a common electronics box. A narrow angle camera
will provide high resolution images of the structure and morphology
of the nucleus of a comet. A wide angle camera with high straylight
rejection and dynamic range will be used to investigate the innermost
coma and the emission process at the surface of the comet. An infrared
imaging system, which dramatically enhances the scientific return has
been included in the narrow angle camera at little extra cost.
---------------------------------------------------------
Title: Time domain analysis of polar plumes observed with LASCO-C2
and EIT
Authors: Llebaria, A.; Lamy, P.; Deforest, Ce.; Koutchmy, S.
1998ESASP.421...87L Altcode: 1998sjcp.conf...87L
No abstract at ADS
---------------------------------------------------------
Title: The panoramic cameras for the Champollion and Roland Cometary
Surface Science Packages
Authors: Lamy, P.; Bibring, J. -P.; Nguyen-Trong, T.; Soufflot, A.;
Boit, J. L.; Dohlen, K.
1998AdSpR..21.1581L Altcode:
We describe the scientific objectives, the design concept and the
implementation of the panoramic cameras which are parts of the In-situ
Imaging System (ISIS) and of the Roland Imaging System (ROLIS) for
respectively the Champollion and Roland Surface Science Packages of the
ESA Rosetta mission. Both instruments will characterize the cometary
surface near the landing site, from the anchoring legs at spatial scales
not achievable by the orbiter cameras, to the local horizon. ROLIS-P
will further monitor the cometary activity and the resulting changes in
the local topography. Both instruments are composed of several identical
miniaturized cameras incorporating a 1024 x 1024 pixels, frame transfer
CCD and a wide-angle optics having a field-of-view of 70 deg. ISIS-P
includes six such cameras to record the full panorama without any
mechanical rotation plus three additional ones to offer stereoscopic
capability in three of the six fields-of-view. ROLIS-P takes advantage
of the rotating capability of the Roland probe and is therefore limited
to a single pair of (stereo) cameras. The camera heads with associated
electronics will be integrated in a single module using the technology
of three-dimensional packaging of electronic components resulting in
highly compact, extremely lightweight units. Both instruments will
provide unique information on the cometary surface at a spatial scale
of 2 mm.
---------------------------------------------------------
Title: Development of Coronal Mass Ejections and Association with
Interplanetary Events
Authors: Pick, M.; Maia, D.; Howard, R.; Thompson, B.; Lanzerotti,
L. J. L.; Bothmer, V.; Lamy, P.
1997ESASP.415..195P Altcode: 1997cpsh.conf..195P
No abstract at ADS
---------------------------------------------------------
Title: Evidence of an Erupting Magnetic Flux Rope: LASCO Coronal
Mass Ejection of 1997 April 13
Authors: Chen, J.; Howard, R. A.; Brueckner, G. E.; Santoro, R.;
Krall, J.; Paswaters, S. E.; St. Cyr, O. C.; Schwenn, R.; Lamy, P.;
Simnett, G. M.
1997ApJ...490L.191C Altcode:
A coronal mass ejection (CME) observed by LASCO exhibits evidence
that its magnetic field geometry is that of a flux rope. The dynamical
properties throughout the fields of view of C2 and C3 telescopes are
examined. The results are compared with theoretical predictions based
on a model of solar flux ropes. It is shown that the LASCO observations
are consistent with a two-dimensional projection of a three-dimensional
magnetic flux rope with legs that remain connected to the Sun.
---------------------------------------------------------
Title: White-Light Coronal Mass Ejections: A New Perspective from
LASCO
Authors: St. Cyr, O. C.; Howard, R. A.; Simnett, G. M.; Gurman, J. B.;
Plunkett, S. P.; Sheeley, N. R.; Schwenn, R.; Koomen, M. J.; Brueckner,
G. E.; Michels, D. J.; Andrews, M.; Biesecker, D. A.; Cook, J.; Dere,
K. P.; Duffin, R.; Einfalt, E.; Korendyke, C. M.; Lamy, P. L.; Lewis,
D.; Llebaria, A.; Lyons, M.; Moses, J. D.; Moulton, N. E.; Newmark,
J.; Paswaters, S. E.; Podlipnik, B.; Rich, N.; Schenk, K. M.; Socker,
D. G.; Stezelberger, S. T.; Tappin, S. J.; Thompson, B.; Wang, D.
1997ESASP.415..103S Altcode: 1997cpsh.conf..103S
No abstract at ADS
---------------------------------------------------------
Title: Circumstellar grains: radiation pressure and temperature
distribution
Authors: Lamy, P. L.; Perrin, J. -M.
1997A&A...327.1147L Altcode:
The ratio beta of the radiation pressure force to the gravitational
attraction is calculated for circumstellar grains. Eleven stars of
various spectral type are considered and their spectral flux compiled
from available data sometimes supplemented by appropriate models. The
materials composing the grains are a silicate (obsidian), organic
materials (ice tholin, poly-HCN), graphite and glassy carbon. The
radius of the grain extends from 0.005 to 25 mu m. beta exceeds 1
for submicronic grains around the hottest stars with the exception of
the obsidian grains. As far as the coldest stars are concerned, the
results are not so clear and depend sharply on the illuminating stars
as well as the nature of the material of the solid particles. Their
temperatures are also studied and two examples are given for obsidian
and graphite grains of radii 0.01, 0.1, 1 and 10 mu m. Our results
are of interest for thin stellar shells such as exo-zodiacal clouds
and for the inner region of dense shells where multiple scattering
effects are not taking place.
---------------------------------------------------------
Title: LASCO Observations of Disconnected Magnetic Structures Out
to Beyond 28 Solar Radii During Coronal Mass Ejections
Authors: Simnett, G. M.; Tappin, S. J.; Plunkett, S. P.; Bedford,
D. K.; Eyles, C. J.; St. Cyr, O. C.; Howard, R. A.; Brueckner, G. E.;
Michels, D. J.; Moses, J. D.; Socker, D.; Dere, K. P.; Korendyke,
C. M.; Paswaters, S. E.; Wang, D.; Schwenn, R.; Lamy, P.; Llebaria,
A.; Bout, M. V.
1997SoPh..175..685S Altcode:
Two coronal mass ejections have been well observed by the LASCO
coronagraphs to move out into the interplanetary medium as disconnected
plasmoids. The first, on July 28, 1996, left the Sun above the west
limb around 18:00 UT. As it moved out, a bright V-shaped structure
was visible in the C2 coronagraph which moved into the field-of-view
of C3 and could be observed out to beyond 28 solar radii. The derived
average velocity in the plane of the sky was 110 ± 5 km s<SUP>-1</SUP>
out to 5 solar radii, and above 15 solar radii the velocity was 269
± 10 km s<SUP>-1</SUP>. Thus there is evidence of some acceleration
around 6 solar radii. The second event occurred on November 5, 1996
and left the west limb around 04:00 UT. The event had an average
velocity in the plane of the sky of ∼54 km s<SUP>-1</SUP> below
4 R⊙, and it accelerated rapidly around 5 R⊙ up to 310 ± 10 km
s<SUP>-1</SUP>. In both events the rising plasmoid is connected back
to the Sun by a straight, bright ray, which is probably a signature of
a neutral sheet. In the November event there is evidence for multiple
plasmoid ejections. The acceleration of the plasmoids around a projected
altitude of 5 solar radii is probably a manifestation of the source
surface of the solar wind.
---------------------------------------------------------
Title: First View of the Extended Green-Line Emission Corona At
Solar Activity Minimum Using the Lasco-C1 Coronagraph on SOHO
Authors: Schwenn, R.; Inhester, B.; Plunkett, S. P.; Epple, A.;
Podlipnik, B.; Bedford, D. K.; Eyles, C. J.; Simnett, G. M.; Tappin,
S. J.; Bout, M. V.; Lamy, P. L.; Llebaria, A.; Brueckner, G. E.;
Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels,
D. J.; Moses, J. D.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.;
St. Cyr, O. C.; Wang, D.
1997SoPh..175..667S Altcode:
The newly developed C1 coronagraph as part of the Large-Angle
Spectroscopic Coronagraph (LASCO) on board the SOHO spacecraft has
been operating since January 29, 1996. We present observations
obtained in the first three months of operation. The green-line
emission corona can be made visible throughout the instrument's full
field of view, i.e., from 1.1 R⊙ out to 3.2 R⊙ (measured from Sun
center). Quantitative evaluations based on calibrations cannot yet be
performed, but some basic signatures show up even now: (1) There are
often bright and apparently closed loop systems centered at latitudes
of 30° to 45° in both hemispheres. Their helmet-like extensions
are bent towards the equatorial plane. Farther out, they merge into
one large equatorial `streamer sheet' clearly discernible out to 32
R⊙. (2) At mid latitudes a more diffuse pattern is usually visible,
well separated from the high-latitude loops and with very pronounced
variability. (3) All high-latitude structures remain stable on time
scales of several days, and no signature of transient disruption of
high-latitude streamers was observed in these early data. (4) Within
the first 4 months of observation, only one single `fast' feature was
observed moving outward at a speed of 70 km s<SUP>-1</SUP> close to
the equator. Faster events may have escaped attention because of data
gaps. (5) The centers of high-latitude loops are usually found at the
positions of magnetic neutral lines in photospheric magnetograms. The
large-scale streamer structure follows the magnetic pattern fairly
precisely. Based on our observations we conclude that the shape
and stability of the heliospheric current sheet at solar activity
minimum are probably due to high-latitude streamers rather than to
the near-equatorial activity belt.
---------------------------------------------------------
Title: The Relationship of Green-Line Transients to White-Light
Coronal Mass Ejections
Authors: Plunkett, S. P.; Brueckner, G. E.; Dere, K. P.; Howard,
R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.;
Moulton, N. E.; Paswaters, S. E.; St. Cyr, O. C.; Socker, D. G.;
Wang, D.; Simnett, G. M.; Bedford, D. K.; Biesecker, D. A.; Eyles,
C. J.; Tappin, S. J.; Schwenn, R.; Lamy, P. L.; Llebaria, A.
1997SoPh..175..699P Altcode:
We report observations by the Large Angle Spectrometric Coronagraph
(LASCO) on the SOHO spacecraft of three coronal green-line transients
that could be clearly associated with coronal mass ejections (CMEs)
detected in Thomson-scattered white light. Two of these events, with
speeds >25 km s<SUP>-1</SUP>, may be classified as `whip-like'
transients. They are associated with the core of the white-light
CMEs, identified with erupting prominence material, rather than with
the leading edge of the CMEs. The third green-line transient has a
markedly different appearance and is more gradual than the other two,
with a projected outward speed <10 km s<SUP>-1</SUP>. This event
corresponds to the leading edge of a `streamer blowout' type of CME. A
dark void is left behind in the emission-line corona following each of
the fast eruptions. Both fast emission-line transients start off as a
loop structure rising up from close to the solar surface. We suggest
that the driving mechanism for these events may be the emergence of new
bipolar magnetic regions on the surface of the Sun, which destabilize
the ambient corona and cause an eruption. The possible relationship of
these events to recent X-ray observations of CMEs is briefly discussed.
---------------------------------------------------------
Title: MHD Interpretation of LASCO Observations of a Coronal Mass
Ejection as a Disconnected Magnetic Structure
Authors: Wu, S. T.; Guo, W. P.; Andrews, M. D.; Brueckner, G. E.;
Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses,
J. D.; Socker, D. G.; Dere, K. P.; Lamy, P. L.; Llebaria, A.; Bout,
M. V.; Schwenn, R.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J.
1997SoPh..175..719W Altcode:
We present a qualitative and quantitative comparison of a single
coronal mass ejection (CME) as observed by LASCO (July 28-29, 1996)
with the results of a three-dimensional axisymmetric time-dependent
magnetohydrodynamic model of a flux rope interacting with a helmet
streamer. The particular CME considered was selected based on the
appearance of a distinct `tear-drop' shape visible in animations
generated from both the data and the model.
---------------------------------------------------------
Title: EIT and LASCO Observations of the Initiation of a Coronal
Mass Ejection
Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.;
Korendyke, C. M.; Kreplin, R. W.; Michels, D. J.; Moses, J. D.;
Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Delaboudinière, J. P.;
Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. F.; Millier,
F.; Song, X. Y.; Chauvineau, J. P.; Marioge, J. P.; Defise, J. M.;
Jamar, C.; Rochus, P.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.;
Neupert, W.; Clette, F.; Cugnon, P.; Van Dessel, E. L.; Lamy, P. L.;
Llebaria, A.; Schwenn, R.; Simnett, G. M.
1997SoPh..175..601D Altcode:
We present the first observations of the initiation of a coronal mass
ejection (CME) seen on the disk of the Sun. Observations with the EIT
experiment on SOHO show that the CME began in a small volume and was
initially associated with slow motions of prominence material and a
small brightening at one end of the prominence. Shortly afterward,
the prominence was accelerated to about 100 km s<SUP>-1</SUP> and
was preceded by a bright loop-like structure, which surrounded an
emission void, that traveled out into the corona at a velocity of
200-400 km s<SUP>-1</SUP>. These three components, the prominence,
the dark void, and the bright loops are typical of CMEs when seen at
distance in the corona and here are shown to be present at the earliest
stages of the CME. The event was later observed to traverse the LASCO
coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest
is the fact that this large-scale event, spanning as much as 70 deg in
latitude, originated in a volume with dimensions of roughly 35" (2.5
x 10<SUP>4</SUP> km). Further, a disturbance that propagated across
the disk and a chain of activity near the limb may also be associated
with this event as well as a considerable degree of activity near the
west limb.
---------------------------------------------------------
Title: Estimating the Size of Hale-Bopp's Nucleus
Authors: Weaver, H. A.; Lamy, P. L.
1997EM&P...79...17W Altcode:
A variety of independent methods have been used to estimate the size of
the nucleus of comet Hale-Bopp. Several groups have analyzed optical
and infrared images of the comet and claim to detect the signature of
the nucleus, despite the presence of a strong coma. A detection of
the nucleus was also claimed during mm- and cm-wave observations of
Hale-Bopp shortly before perihelion. A team of observers detected the
occultation of a star by the nucleus of Hale-Bopp in October 1996. The
maximum observed gas production rate of the comet near perihelion can
be used to place a lower limit on the size of the nucleus. This paper
critically reviews the many different methods used to constrain the size
of Hale-Bopp's nucleus. All of the techniques are affected by systematic
errors that can be difficult to quantify precisely. Nevertheless, the
available evidence strongly suggests that the nucleus of Hale-Bopp has
an effective radius of at least 15 km and is probably in the range 20
35 km. Thus, the prodigious gas and production rates from this comet
are naturally explained by its unusually large size.
---------------------------------------------------------
Title: Origin and Evolution of Coronal Streamer Structure During
the 1996 Minimum Activity Phase
Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Howard, R. A.; Kraemer,
J. R.; Rich, N. B.; Andrews, M. D.; Brueckner, G. E.; Dere, K. P.;
Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.;
Paswaters, S. E.; Socker, D. G.; Wang, D.; Lamy, P. L.; Llebaria,
A.; Vibert, D.; Schwenn, R.; Simnett, G. M.
1997ApJ...485..875W Altcode:
We employ coronal extrapolations of solar magnetograph data to interpret
observations of the white-light streamer structure made with the LASCO
coronagraph in 1996. The topological appearance of the streamer belt
during the present minimum activity phase is well described by a model
in which the Thomson-scattering electrons are concentrated around a
single, warped current sheet encircling the Sun. Projection effects
give rise to bright, jet-like structures or spikes whenever the current
sheet is viewed edge-on multiple spikes are seen if the current sheet is
sufficiently wavy. The extreme narrowness of these features in polarized
images indicates that the scattering layer is at most a few degrees
wide. We model the evolution of the streamer belt from 1996 April to
1996 September and show that the effect of photospheric activity on
the streamer belt topology depends not just on the strength of the
erupted magnetic flux, but also on its longitudinal phase relative
to the background field. Using flux transport simulations, we also
demonstrate how the streamer belt would evolve during a prolonged
absence of activity.
---------------------------------------------------------
Title: Measurements of Flow Speeds in the Corona Between 2 and 30
R<SUB>⊙</SUB>
Authors: Sheeley, N. R.; Wang, Y. -M.; Hawley, S. H.; Brueckner,
G. E.; Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.;
Michels, D. J.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C.;
Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; Simnett, G. M.;
Plunkett, S.; Biesecker, D. A.
1997ApJ...484..472S Altcode:
Time-lapse sequences of white-light images, obtained during sunspot
minimum conditions in 1996 by the Large Angle Spectrometric Coronagraph
on the Solar and Heliospheric Observatory, give the impression of
a continuous outflow of material in the streamer belt, as if we
were observing Thomson scattering from inhomogeneities in the solar
wind. Pursuing this idea, we have tracked the birth and outflow of
50-100 of the most prominent moving coronal features and find that:
<P />1. They originate about 3-4 R<SUB>⊙</SUB> from Sun center as
radially elongated structures above the cusps of helmet streamers. Their
initial sizes are about 1 R<SUB>⊙</SUB> in the radial direction and
0.1 R<SUB>⊙</SUB> in the transverse direction. <P />2. They move
radially outward, maintaining constant angular spans and increasing
their lengths in rough accord with their speeds, which typically
double from 150 km s<SUP>-1</SUP> near 5 R<SUB>⊙</SUB> to 300 km
s<SUP>-1</SUP> near 25 R<SUB>⊙</SUB>. <P />3. Their individual speed
profiles v(r) cluster around a nearly parabolic path characterized
by a constant acceleration of about 4 m s<SUP>-2</SUP> through most
of the 30 R<SUB>⊙</SUB> field of view. This profile is consistent
with an isothermal solar wind expansion at a temperature of about
1.1 MK and a sonic point near 5 R<SUB>⊙</SUB>. <P />Based on their
relatively small initial sizes, low intensities, radial motions, slow
but increasing speeds, and location in the streamer belt, we conclude
that these moving features are passively tracing the outflow of the
slow solar wind.
---------------------------------------------------------
Title: Using LASCO Observations to Infer Solar Wind Flow Near the Sun
Authors: Sheeley, N. R., Jr.; Brueckner, G. E.; Dere, K. P.; Howard,
R. A.; Korendyke, C. M.; Michels, D. J.; Socker, D. G.; Koomen, M. J.;
Paswaters, S. E.; Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.;
St Cyr, O. C.; Simnett, G. M.; Plunkett, S.; Biesecker, D. A.
1997SPD....28.0301S Altcode: 1997BAAS...29..907S
We have continued to track individual coronal features as they become
detached from helmet streamers and move outward from the Sun. The
composite speed profile for 50-100 features has a parabolic shape
with a constant acceleration of about 4 m/s(2) over the 2-30 R field
of view. This well-determined speed profile contrasts strongly with
the nearly uniform scatterplot obtained for about 50 nominal coronal
mass ejections (CMEs), and suggests that these detached bits of coronal
“debris” are passively tracing the speed of the slow solar wind. We
have also begun the more difficult task of tracking outflow along
polar plumes and will summarize these results as of June 1997.
---------------------------------------------------------
Title: The Solar Minimum X2. 6/1B Flare and CME of 9 July 1996;
Part 1: Solar Data
Authors: Andrews, M. D.; Dryer, M.; Aurass, H.; DeForest, C.;
Kiplinger, A. L.; Meisner, R.; Paswaters, S. E.; Smith, Z.; Tappipn,
S. J.; Thompson, B. J.; Watari, S. I.; Lamy, P.; Mann, G.; Schwenn,
R.; Michels, D. J.; Brueckner, G. E.; Howard, R. A.; Koomen, M.
1997ESASP.404..169A Altcode: 1997cswn.conf..169A
No abstract at ADS
---------------------------------------------------------
Title: Intercomparison between UVCS/WLC and LASCO/C2 measured
polarized brightness
Authors: Romoli, M.; Biesecker, D.; Benna, C.; Fineschi, S.; Lamy,
P. L.; Llebaria, A.; Kohl, J. L.; Noci, G.
1997ESASP.404..637R Altcode: 1997cswn.conf..637R
No abstract at ADS
---------------------------------------------------------
Title: Characterisation of Polar Plumes from LASCO-C2 Images in
Early 1996
Authors: Lamy, P.; Liebaria, A.; Koutchmy, S.; Reynet, P.; Molodensky,
M.; Howard, R.; Schwenn, R.; Simnett, G.
1997ESASP.404..487L Altcode: 1997cswn.conf..487L
No abstract at ADS
---------------------------------------------------------
Title: The April 7, 1997 Event: LASCO and Nancay Radioheliograph
Joint Observations
Authors: Maia, D.; Pick, M.; Howard, R.; Brueckner, G. E.; Lamy, P.
1997ESASP.404..539M Altcode: 1997cswn.conf..539M
No abstract at ADS
---------------------------------------------------------
Title: The Solar Minimum X2. 6/1B Flare and CME of 9 July 1996;
Part 2: Propagation
Authors: Dryer, M.; Andrews, M. D.; Aurass, H.; DeForest, C.; Karlicky,
M.; Kiplinger, A.; Klassen, A.; Meisner, R.; Ipavich, F. M.; Galvin,
A. B.; Paswaters, S. E.; Smith, Z.; Tappin, S. J.; Thompson, B. J.;
Watari, S. -I.; Michels, D. J.; Brueckner, G. E.; Howard, R. A.;
Koomen, M. J.; Lamy, P.; Mann, G.; Arzner, K.; Schwenn, R.
1997ESASP.404..331D Altcode: 1997cswn.conf..331D
No abstract at ADS
---------------------------------------------------------
Title: Acceleration of Coronal Mass Ejections in the Upper Corona:
Observations from Lasco/Soho
Authors: Simnett, G. M.; Tappin, S. J.; Brueckner, G. E.; Howard,
R. A.; Lamy, P.; Michels, D. J.; Schwenn, R.
1997ICRC....1..181S Altcode: 1997ICRC...25a.181S
No abstract at ADS
---------------------------------------------------------
Title: Dynamical Evolution of a Coronal Mass Ejection (CME) to
Magnetic Cloud: A Preliminary Analysis of the January 6-10, 1997
CME Observed by LASCO/SOHO
Authors: Wu, S. T.; Guo, W. P.; Michels, D. J.; Andrews, M. D.;
Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.;
Moses, J. D.; Socker, D. G.; Dere, K. P.; Bougeret, Jean-Louis; Lamy,
P. L.; Schwenn, R.; Simnett, G. M.
1997ESASP.404..739W Altcode: 1997cswn.conf..739W
No abstract at ADS
---------------------------------------------------------
Title: In-Orbit Calibration of the Distortion of the SOHO/LASCO-C2
Coronagraph
Authors: Llebaria, A.; Aubert, S.; Lamy, P.; Plunkett, S.
1997ASPC..125..435L Altcode: 1997adass...6..435L
This paper describes distortion calibration procedures for the
SOHO/LASCO-C2 Coronagraph, based on in-orbit data and extensive image
processing methods. It addresses specific problems of externally
occulted coronagraphs (obstructed center of field-of-view, strong
vignetting, and presence of stray light) and limitations inherent
to space-based instrumentation (cosmic rays and limited number of
reference points).
---------------------------------------------------------
Title: EIT and LASCO Observations of the Initiation of a Coronal
Mass Ejection
Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.;
Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Socker,
D. G.; Delaboudiniere, J. P.; Hochedez, J. F.; Lamy, P. L.; Schwenn,
R.; Simnett, G. M.; Defise, J. M.; Catura, R. C.
1997IAUJD..19E..18D Altcode:
We present the first observations of the initiation of a corona mass
ejection (CME) seen on the disk of the Sun. Observations with the EIT
and LASCO experiments on SOHO show that the CME starts in a small volume
and is associated with slow motions of prominence material. At about
the same time, a shock wave is created that travels out into the corona
at a velocity of 400 km s^{-1} ahead of an eruptive prominence. This
shock wave is clearly the event that is later seen as a classical CME
when observed in the coronagraph above 1.5 solar radii. Although the
CME clearly starts in a small region, a chain of activity near the
limb may also be associated with this event.
---------------------------------------------------------
Title: The Streamer Belt at Solar Minimum: Simulation and Comparison
with LASCO-C2 Images
Authors: Vibert, D.; Lamy, P.; Liebaria, A.
1997ESASP.404..713V Altcode: 1997cswn.conf..713V
No abstract at ADS
---------------------------------------------------------
Title: Reconstruction of the electron density distribution in the
solar corona based on LASCO C2 observations
Authors: Cugnon, P.; Gabryl, J. -R.; Lamy, P.
1997IAUJD..19E..17C Altcode:
From total intensities images provided by the C2 coronagraph with orange
filter (visible range) we try to reconstruct the large scale electron
density in the corona, using a model based on the assumption of an
axisymmetric corona, which allows for a separation between the angular
and radial descriptions. This method has been successfully applied to
the eclipse observations of 1991 and 1994 and gave results up to 3.1
solar radii. In the case of LASCO C2, the range extends from 2.5 to
7 solar radii, where the F-corona gets more and more predominant. In
order to extract the K-corona signal, accurate values of the F-corona
must be subtracted from total intensities. An iterative process based
on pre-existing tables is applied for this purpose. We also trace the
evolution of the global structure of the corona during a solar rotation.
---------------------------------------------------------
Title: Electronic Densities in Coronal Holes from LASCO-C2 Images
Authors: Lamy, P.; Quemerais, E.; Llebaria, A.; Bout, M.; Howard,
R.; Schwenn, R.; Simnett, G.
1997ESASP.404..491L Altcode: 1997cswn.conf..491L
No abstract at ADS
---------------------------------------------------------
Title: Joint Radioheliograph and LASCO Observations of Coronal
Mass Ejections
Authors: Pick, M.; Maia, D.; Howard, R.; Kerdraon, A.; Brueckner,
G. E.; Lamy, P.; Schwenn, R.; Aurass, H.
1997ESASP.404..601P Altcode: 1997cswn.conf..601P
No abstract at ADS
---------------------------------------------------------
Title: Visibility of Earth-Directed Coronal Mass Ejections
Authors: Michels, D. J.; Howard, R. A.; Koomen, M. J.; Plunkett, S.;
Brueckner, G. E.; Lamy, Ph.; Schwenn, R.; Biesecker, D. A.
1997ESASP.404..567M Altcode: 1997cswn.conf..567M
No abstract at ADS
---------------------------------------------------------
Title: Analysis of a High Latitude Slow CME with Travelling Ejecta
Authors: Boulade, S.; Delanné, C.; Koutchmy, S.; Lamy, P.; Llebaria,
A.; Howard, R.; Schwenn, R.; Simnett, G.
1997ESASP.404..217B Altcode: 1997cswn.conf..217B
No abstract at ADS
---------------------------------------------------------
Title: Synthetic Images of the Solar Corona from Octree Representation
of 3-D Electron Distributions
Authors: Vibert, D.; Llebaria, A.; Netter, T.; Balard, L.; Lamy, P.
1997ASPC..125..230V Altcode: 1997adass...6..230V
Empirical and theoretical modeling of 3-D structures in the solar corona
is confronted by the tremendous amount of data needed to represent
phenomena with a large dynamic range both in size and magnitude,
and with a rapid temporal evolution. Octree representation of the
3-D coronal electron distribution offers the right compromise between
resolution and size, allowing computation of synthetic images of the
solar corona.
---------------------------------------------------------
Title: The infrared spectrum of comet C/1995 O1 (Hale-Bopp) at 4.6
AU from the Sun.
Authors: Crovisier, J.; Brooke, T. Y.; Hanner, M. S.; Keller, H. U.;
Lamy, P. L.; Altieri, B.; Bockelee-Morvan, D.; Jorda, L.; Leech, K.;
Lellouch, E.
1996A&A...315L.385C Altcode:
Comet C/1995 O1 (Hale-Bopp) was observed on 27 April 1996 with the
ISOPHOT instrument of ISO when it was at 4.6 AU from the Sun. The
2.5-12μm spectrum was recorded at low resolution. We present here
the preliminary results of this observation. The 2.5-5μm spectrum
shows emission in the CO_2_ ν_3_ band. The CO_2_ production rate is
about 1.3x10^28^ s^-1^. The 6-12μm spectrum shows thermal emission
at a colour temperature of 162K (6-8μm range) and a strong silicate
band around 10μm, with a narrow feature at 11.2μm indicative of
crystalline silicates.
---------------------------------------------------------
Title: STEREO: a solar terrestrial event observer mission concept
Authors: Socker, Dennis G.; Antiochos, S. K.; Brueckner, Guenter E.;
Cook, John W.; Dere, Kenneth P.; Howard, Russell A.; Karpen, J. T.;
Klimchuk, J. A.; Korendyke, Clarence M.; Michels, Donald J.; Moses,
J. Daniel; Prinz, Dianne K.; Sheely, N. R.; Wu, Shi T.; Buffington,
Andrew; Jackson, Bernard V.; Labonte, Barry; Lamy, Philippe L.;
Rosenbauer, H.; Schwenn, Rainer; Burlaga, L.; Davila, Joseph M.; Davis,
John M.; Goldstein, Barry; Harris, H.; Liewer, Paulett C.; Neugebauer,
Marcia; Hildner, E.; Pizzo, Victor J.; Moulton, Norman E.; Linker,
J. A.; Mikic, Z.
1996SPIE.2804...50S Altcode:
A STEREO mission concept requiring only a single new spacecraft has been
proposed. The mission would place the new spacecraft in a heliocentric
orbit and well off the Sun- Earth line, where it can simultaneously view
both the solar source of heliospheric disturbances and their propagation
through the heliosphere all the way to the earth. Joint observations,
utilizing the new spacecraft and existing solar spacecraft in earth
orbit or L1 orbit would provide a stereographic data set. The new
and unique aspect of this mission lies in the vantage point of the
new spacecraft, which is far enough from Sun-Earth line to allow an
entirely new way of studying the structure of the solar corona, the
heliosphere and solar-terrestrial interactions. The mission science
objectives have been selected to take maximum advantage of this new
vantage point. They fall into two classes: those possible with the
new spacecraft alone and those possible with joint measurements using
the new and existing spacecraft. The instrument complement on the new
spacecraft supporting the mission science objectives includes a soft
x-ray imager, a coronagraph and a sun-earth imager. Telemetry rate
appears to be the main performance determinant. The spacecraft could
be launched with the new Med-Lite system.
---------------------------------------------------------
Title: Spectroscopic Observations of Comet C/1995 O1 (Hale-Bopp)
with the Infrared Space Observatory
Authors: Crovisier, J.; Bockelee-Morvan, D.; Lellouch, E.; Brooke,
T. Y.; Hanner, M. S.; Keller, H. U.; Jorda, L.; Altieri, B.; Leech,
K.; Lamy, P. L.
1996DPS....28.0921C Altcode: 1996BAAS...28.1092C
Comet C/1995 O1 (Hale-Bopp) was selected to be observed in the
target-of-opportunity comet program of the Infrared Space Observatory
(ISO). The first results of the spectroscopic part of this program
are reported here. Comet Hale-Bopp was observed on 27 April 1996 with
the ISOPHOT instrument of ISO when it was at 4.6 AU from the Sun. The
2.5--12 mu m spectrum was recorded at low resolution. The 2.5--5. mu m
spectrum shows emission in the CO_2 nu_3 band at 4.26 mu m. Upper limits
for other molecular bands (H_2O, CO, CH_3OH) are in agreement with
observations of these species at other wavelengths. The CO_2 production
rate is about 1.3 x 10(28) molecules s(-1) . This is about one third of
the H_2O and CO production rates observed at other wavelengths, which
indicates that carbon dioxide is an important constituant of cometary
volatiles at this heliocentric distance. The 6--12 mu m spectrum shows
thermal emission at a colour temperature of 162 K (6--8 mu m range)
and a strong silicate band around 10 mu m, with a narrow feature at
11.2 mu m indicative of crystalline silicates. There is no indication
of differences of composition for grains in comets Hale-Bopp and
Halley. Comet Hale-Bopp is to be observed at higher spectral resolution
with the SWS and LWS instruments of ISO in September-October 1996.
---------------------------------------------------------
Title: Comet 46P/Wirtanen
Authors: Lamy, P.
1996IAUC.6478....2L Altcode:
P. Lamy, Laboratoire d'Astronomie Spatiale, and his team report the
apparent detection of the nucleus of 46P with the Hubble Space Telescope
(+ WFPC2) on Aug. 28: "After removing the small contribution of the
(stable) coma to the central pixels, the R magnitude of the nucleus
was found to vary from 21.6 to 21.9 over time intervals of 1.5 hr,
though a clear rotational pattern is not evident. For a geometric
albedo of 0.04, the mean effective radius is 0.58 km."
---------------------------------------------------------
Title: HST Observations of the Nuclei of Comets
45P/Honda-Mrkos-Pajdusakova, 22P/Kopff, and 46P/Wirtanen
Authors: Lamy, P. L.; A'Hearn, M. F.; Toth, I.; Weaver, H. A.
1996DPS....28.0804L Altcode: 1996BAAS...28.1083L
Comet 45P/Honda-Mrkos-Pajdusakova (H-M-P) was observed with
the Planetary Camera (WFPC2) of the Hubble Space Telescope on
two consecutive days, 4 and 5 February 1996, at which time the
geocentric distance was 0.17 AU (1 pixel projected to a distance
of 5.6 km at the comet) and the phase angles were 93 and 88 deg,
respectively. Although much fainter than expected, the nucleus was
clearly detected superimposed on a very weak coma. The accuracy of
the determination of the size of the nucleus is limited primarily
by the unknown phase law for such large phase angles. Assuming a
constant phase coefficient of 0.04 mag/deg and a geometric albedo of
0.04 near 675 nm, we derived an effective diameter of 0.70 km. Comet
22P/Kopff was observed on 18 July 1996 at a geocentric distance of
0.57 AU (1 pixel projected to a distance of 19 km at the comet) and
a phase angle of 3 deg. Over the 11 hour time interval spanned by
the observations, we see a variation in the nuclear magnitude that
corresponds to changes in the effective nuclear diameter from 3.30 to
3.84 km, using the same assumptions as above for the albedo and phase
law. The uncertainty in the nuclear diameter is determined primarily
by the systematic error in estimating the contribution of the coma
to the peak pixel intensity. The light curve data are being used
to determine the rotation period for the nucleus. Comparison of our
derived sizes with published gas production rates for comets H-M-P and
Kopff indicate that the fractional active surface area is ~ 10% for
each nucleus. Comet 46P/Wirtanen will be observed on 28 August 1996,
and we expect to report preliminary results on its size.
---------------------------------------------------------
Title: LASCO Observations of the 03Feb96 Streamer Blow-out
Authors: Andrews, M. D.; Korendyke, C. M.; Koomen, M. J.; Brueckner,
G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses,
J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.;
St. Cyr, O. C. St.; Wang, D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.;
Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker, D. A.; Eyles,
C. J.; Plunkett, S.; Simnett, G. M.
1996AAS...188.3716A Altcode: 1996BAAS...28..880A
The C2 and C3 telescopes on the Large Angle Spectrometric Coronograph
(LASCO) have recorded images of a Streamer Blow-out which occured
on 03Feb96. We will present a series of images produces by combining
data from the 2 coronographs. These images show a rapid evolution of
the coronal streamer belt over projected distances of 2 to 20 solar
radii. The streamer belt shows a dramatic brightening, which is seen to
propagate outward. A bubble-like structure is seen to move away from
the Sun and expand. At the end of this event, the equatorial corona
is significantly less bright than prior to the event.
---------------------------------------------------------
Title: LASCO Observations of the Solar Corona to 32 R<SUB>sun</SUB>
Authors: Cook, J. W.; Koomen, M. J.; Korendyke, C. M.; Brueckner,
G. E.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Morrill, J. S.;
Moses, J. D.; Socker, D. G.; Paswaters, S. E.; Wang, D.; Moulton,
N. E.; Cyr, O. C. St.; Andrews, M. D.; Schwenn, R.; Podlipnik, B.;
Lamy, P. L.; Llebaria, A.; Bout, M. V.; Simnett, G. M.; Bedford,
D. K.; Eyles, C. J.; Plunkett, S.; Biesecker, D. A.
1996AAS...188.3717C Altcode: 1996BAAS...28..880C
The Large Angle Spectrometric Coronagraph (LASCO) was launched on
board the SOHO satellite on 2 December 1995. The C3 externally-occulted
coronagraph of LASCO observes the solar corona over a field from 3.7-32
R_ ⊙, using a 1024x1024 CCD detector with a pixel size corresponding
to 56 arc sec. Observations can be made using color filters ranging
from the blue (420-520 nm) to the near-IR (860-1050 nm), and through
polarizing filters. We report on early observations of the solar corona
out to 32 R<SUB>sun</SUB>.
---------------------------------------------------------
Title: Preliminary Photometric Calibration of LASCO C3 Coronagraph
Images using Pre-Flight Laboratory Images of Standard Sources and
In-Flight Images of Standard Stars
Authors: Korendyke, C. M.; Koomen, M. J.; Andrews, M. D.; Brueckner,
G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.;
Moses, J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.;
Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.;
Bout, M. V.; Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker,
D. A.; Eyles, C. J.; Plunkett, S.; Simnett, G. M.
1996AAS...188.3621K Altcode: 1996BAAS...28..876K
The C3 coronagraph is a wide field (+/-8.0 degrees), externally
occulted, white light coronagraph. The instrument is one of three
coronagraphs comprising the Large Angle Spectrometric COronagraph
(LASCO) experiment mounted on the Solar Heliospheric Observatory
satellite. The satellite was launched on Dec. 2, 1996; C3 observations
began in early Jan. 1997. The coronagraph optical train includes a set
of five broadband color filters mounted in a wheel. Prior to flight,
an image was obtained through each color filter of a well characterized,
rear-illuminated, opal glass diffusing screen. The C3 in-flight images,
in addition to the coronal structures, also contain several hundred
bright stars. We present a comparison of the photometric calibration
derived from standard stars with the laboratory measurements. The
resulting calibration is then used to examine color variations in the
white light corona over the field of view. The LASCO experiment was
developed by a scientific consortium of members from NRL (USA), MPAe
(Germany), LAS (France) and U. Birmingham (United Kingdom).
---------------------------------------------------------
Title: Optical designs for the Rosetta narrow-angle camera
Authors: Dohlen, Kjetil; Saisse, Michel; Claeysen, Genevieve; Lamy,
Philippe L.; Boit, Jean-Lucien
1996OptEn..35.1150D Altcode:
Optical designs for the Rosetta narrow-angle camera (NAC) and its UV
spectrograph are presented. The NAC requires a 600 mm focal length
system of focal ratio f/7 imaging a square field of width 2.3 deg onto
a square detector array 2048 pixels wide. A cartographic method has
been used to search for flat-field, three-mirror anastigmats (TMA)
with the required geometrical constraints and at least one spherical
surface; the use of spherical surfaces reduces fabrication cost and
complexity and facilitates alignment. Two such systems are described,
one with a spherical secondary, the other with a spherical tertiary. A
deterministic alignment method is outlined where alignment defects are
calculated from measurements of image position and Zernike wavefront
coefficients. For the spectrograph, an all-reflecting, Thevenin-type
concentric spectrograph has been designed. This design offers excellent
image quality both spectrally and spatially along a long slit and it
is compact and easily accommodated.
---------------------------------------------------------
Title: A coronal optical imager for a solar probe
Authors: Lamy, P.; Koutchmy, S.
1996AdSpR..17c..95L Altcode: 1996AdSpR..17...95L
A Coronal Optical Imager (COI) can make a significant contribution
to a solar probe, for instance, by detecting the faintest plasma and
magnetic structures, by analyzing the He/H ratio and the cool plasma
component and by observing possible sources of dust near the Sun. We
describe an instrument which combines the capability of EUV, UV and
visible imaging as well as visible polarimetry, and propose two versions
respectively adapted to a spinning and a 3-axis stabilized probes.
---------------------------------------------------------
Title: Observations of Comet P/Faye 1991 XXI with the Planetary
Camera of the Hubble Space Telescope
Authors: Lamy, P. L.; Toth, I.; Grün, E.; Keller, H. U.; Sekanina,
Z.; West, R. M.
1996Icar..119..370L Altcode:
Comet P/Faye 1991 XXI (1991 n) was observed with the planetary
camera (PC) of the Hubble Space Telescope (HST) between October
29 and November 21, 1991, when its geocentric distance was in the
range 0.62-0.67 AU. The resulting high resolution-a single PC pixel
projected to a distance of ∼20 km at the comet-made it possible to
clearly discriminate the nucleus and to study the dust coma within
∼100 km from the nucleus. The spherical aberration which affected
the early operation of the HST has severely complicated the analysis
and image restoration using the Richardson-Lucy method has failed to
give satisfactory results. The coma is dominated by the point spread
function (PSF) of the nucleus up to a radial distance of ∼100 km
and cannot be recovered. Beyond, it is affected by the spherical
aberration up to approximately 750 km and was analyzed by comparison
with a grid of models convolved with appropriate PSFs. Beyond 750 km,
it remains unaffected and can be studied directly. From the outer to
the innermost regions, the coma presents an elongated shape which may
be explained either by an active source on the nucleus or, more likely,
by a projection effect of the dust tail. If this second interpretation
is correct, then the temporal evolution of the comet is very slow
and smooth, suggesting an extended source of dust on the nucleus. The
dust production rate, corrected for the projection effect of the tail,
amounts to 125 kg sec<SUP>-1</SUP>.
---------------------------------------------------------
Title: Summary Remarks
Authors: Lamy, Ph. L.
1996ASPC..104..527L Altcode: 1996IAUCo.150..527L; 1996pcdi.conf..527L
No abstract at ADS
---------------------------------------------------------
Title: An Optical Instrument to Characterize Individual Dust Particles
Authors: Giovane, F.; Gustafson, B. A. S.; Lamy, Ph. L.
1996ASPC..104..247G Altcode: 1996pcdi.conf..247G; 1996IAUCo.150..247G
No abstract at ADS
---------------------------------------------------------
Title: Laboratory Measurements of Light Scattering by Dust Particles
Authors: Combet, Pp.; Lamy, Ph. L.
1996ASPC..104..409C Altcode: 1996pcdi.conf..409C; 1996IAUCo.150..409C
No abstract at ADS
---------------------------------------------------------
Title: Observations of the comet Hyakutake by the LASCO coronagraph
on the SOHO satellite.
Authors: Andrews, M. D.; Paswaters, S. E.; Brueckner, G. E.; Korendyke,
C. M.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses, J. D.;
Morril, J. S.; Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Wang,
D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Podlipnik,
B.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Plunket, S.;
Simnet, G. M.
1996BAAS...28.1195A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dust Flux Analyser experiment for the Rosetta mission
Authors: Leese, M. R.; McDonnell, J. A. M.; Green, S. F.; Busoletti,
E.; Clark, B. C.; Colangeli, L.; Crifo, J. F.; Eberhardt, P.; Giovane,
F.; Grün, E.; Gustafson, B.; Hughes, D. W.; Jackson, D.; Lamy, P.;
Langevin, Y.; Mann, I.; McKenna-Lawlor, S.; Tanner, W. G.; Weissman,
P. R.; Zarnecki, J. C.
1996AdSpR..17l.137L Altcode: 1996AdSpR..17..137L
We present the description of a design for a proposed Dust Flux Analyser
for the Rosetta cometary mission. A concept first developed for the
NASA/ESA Tempel II Rendezvous and Halley Intercept Mission /1/, the
instrument is able to measure dust particle parameters and fluxes over
a velocity range typical of emission from cometary surfaces. It would
be mounted on the Rosetta Orbiter and would measure the variation in
flux rate throughout all mission phases at the comet. The instrument
would measure particle flux, velocity, momentum and density, shape
and scattering properties.
---------------------------------------------------------
Title: Concepts for Dust Velocity Measurements on a Cometary Orbiter
Authors: Perruchot, S.; Lamy, Ph. L.; Giovane, F.; Gustafson, B. A. S.
1996ASPC..104..255P Altcode: 1996IAUCo.150..255P; 1996pcdi.conf..255P
No abstract at ADS
---------------------------------------------------------
Title: The Large Angle Spectroscopic Coronagraph (LASCO)
Authors: Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke,
C. M.; Michels, D. J.; Moses, J. D.; Socker, D. G.; Dere, K. P.;
Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Simnett, G. M.;
Bedford, D. K.; Eyles, C. J.
1995SoPh..162..357B Altcode:
The Large Angle Spectroscopic Coronagraph (LASCO) is a three
coronagraph package which has been jointly developed for the Solar
and Heliospheric Observatory (SOHO) mission by the Naval Research
Laboratory (USA), the Laboratoire d'Astronomie Spatiale (France),
the Max-Planck-Institut für Aeronomie (Germany), and the University
of Birmingham (UK). LASCO comprises three coronagraphs, C1, C2, and C3,
that together image the solar corona from 1.1 to 30 R<SUB>⊙</SUB> (C1:
1.1 - 3 R<SUB>⊙</SUB>, C2: 1.5 - 6 R<SUB>⊙</SUB>, and C3: 3.7 - 30
R<SUB>⊙</SUB>). The C1 coronagraph is a newly developed mirror version
of the classic internally-occulted Lyot coronagraph, while the C2 and
C3 coronagraphs are externally occulted instruments. High-resolution
imaging spectroscopy of the corona from 1.1 to 3 R<SUB>⊙</SUB> can
be performed with the Fabry-Perot interferometer in C1. High-volume
memories and a high-speed microprocessor enable extensive on-board image
processing. Image compression by a factor of about 10 will result in
the transmission of 10 full images per hour.
---------------------------------------------------------
Title: Comet 19P/Borrelly
Authors: Lamy, P.
1995IAUC.6204....2L Altcode:
P. Lamy, Laboratoire d'Astronomie Spatiale, Marseille, and his team
report: "Using the Wide Field Planetary Camera 2 of the Hubble Space
Telescope, we have detected a highly elongated nucleus rotat- ing
with a synodic period of 24.7 hr. The prolate spheroid that gives
the best fit to the nuclear-magnitude light curve has major and minor
axes dimensions of 8.3 and 3.3 km, respectively, assuming a geometric
albedo of 4 percent. We estimate that about 10 percent of the surface
area is active."
---------------------------------------------------------
Title: Visible and Radio Observations of Comet 19P/Borrelly
Authors: Bockelée-Morvan, D.; Biver, N.; Colom, P.; Crovisier, J.;
Gérard, E.; Jorda, L.; Davies, J. K.; Dent, B.; Colas, F.; Despois,
D.; Paubert, G.; Lamy, P.
1995DPS....27.3308B Altcode: 1995BAAS...27.1144B
No abstract at ADS
---------------------------------------------------------
Title: HST Observations of the Nucleus of Comet 19P/Borrelly 1994 I
Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.
1995DPS....27.3315L Altcode: 1995BAAS...27.1145L
No abstract at ADS
---------------------------------------------------------
Title: Temporal and Spatial Variations among the SL9 Fragments
Authors: Weaver, H. A.; A'Hearn, M. F.; Arpigny, C.; Feldman, P. D.;
Lamy, Ph.; Meech, K. J.; Noll, K. S.; Smith, T. E.
1995DPS....27.2016W Altcode: 1995BAAS...27Q1115W
No abstract at ADS
---------------------------------------------------------
Title: The Hubble Space Telescope (HST) Observing Campaign on Comet
Shoemaker- Levy 9
Authors: Weaver, H. A.; A'Hearn, M. F.; Arpigny, C.; Boice, D. C.;
Feldman, P. D.; Larson, S. M.; Lamy, P.; Levy, D. H.; Marsden, B. G.;
Meech, K. J.; Noll, K. S.; Scotti, J. V.; Sekanina, Z.; Shoemaker,
C. S.; Shoemaker, E. M.; Smith, T. E.; Stern, S. A.; Storrs, A. D.;
Trauger, J. T.; Yeomans, D. K.; Zellner, B.
1995Sci...267.1282W Altcode:
The Hubble Space Telescope made systematic observations of the
split comet P/Shoemaker-Levy 9 (SL9) (P designates a periodic comet)
starting in July 1993 and continuing through mid-July 1994 when the
fragments plunged into Jupiter's atmosphere. Deconvolutions of Wide
Field Planetary Camera images indicate that the diameters of some
fragments may have been as large as ~2 to 4 kilometers, assuming
a geometric albedo of 4 percent, but significantly smaller values
(that is, <1 kilometer) cannot be ruled out. Most of the fragments
(or nuclei) were embedded in circularly symmetric inner comae from July
1993 until late June 1994, implying that there was continuous, but weak,
cometary activity. At least a few nuclei fragmented into separate,
condensed objects well after the breakup of the SL9 parent body, which
argues against the hypothesis that the SL9 fragments were swarms of
debris with no dominant, central bodies. Spectroscopic observations
taken on 14 July 1994 showed an outburst in magnesium ion emission that
was followed closely by a threefold increase in continuum emission,
which may have been caused by the electrostatic charging and subsequent
explosion of dust as the comet passed from interplanetary space into
the jovian magnetosphere. No OH emission was detected, but the derived
upper limit on the H_2O production rate of ~10<SUP>27</SUP> molecules
per second does not necessarily imply that the object was water-poor.
---------------------------------------------------------
Title: Direct detection of a cometary nucleus with the Hubble Space
Telescope.
Authors: Lamy, P. L.; Toth, I.
1995A&A...293L..43L Altcode:
We report the unambiguous detection with the Planetary Camera of the
Hubble Space Telescope of the nucleus of comet P/Faye 1991XXI during
its last perihelion passage when it was at 0.6AU from the Earth. The
high resolution of the HST allowed to discriminate the nucleus against
the bright coma. The reduced V magnitude of the nucleus ranges between
15.5 and 15.9. Assuming a geometric albedo of 0.04, we found a rather
spherical body with a mean radius of 2.68km.
---------------------------------------------------------
Title: Discrimination of Point-like Objects in Astronomical Images
using Surface Curvature
Authors: Llebaria, A.; Lamy, P.; Malburet, P.
1995ASPC...77..484L Altcode: 1995adass...4..484L
A new method for the discrimination of point-like objects in
astronomical images is presented. The method makes use of the surface
curvature of the image, without any a priori knowledge of the shape
of the point-like objects.
---------------------------------------------------------
Title: The LASCO database at LAS
Authors: Mathieu, C.; Llebaria, A.; Lamy, P.
1995VA.....39..109M Altcode:
In the framework of the SOHO (Solar Heliospheric Observatory) space
mission of observation of the sun, conducted jointly by ESA and NASA,
the Marseilles Laboratoire d'Astronomie Spatiale (LAS) contributes
to the LASCO experiment — a study of the Solar corona — within
an international consortium. Our laboratory participates in LASCO
data reduction and is responsible for setting up a national database
for French investigators. This database shall provide access to a
huge amount of data, resulting from the collection and archiving of
about 180 images per day (each image having a size between 2 and 4
Mo), during the whole mission duration (2 years; launch scheduled in
September 1995). Of a relational structure (Sybase), the database is
designed to store calibration images, from before and after launch,
as well as mission images. It is intended to build interfaces to
automatically load the new images into the database and into the
IDL image processing software. Data will be made available to French
astronomers through a WWW server which will provide compressed images,
transferable via networks. The server will also offer interactive
access to the data and will deliver the necessary information on how
to retrieve the images and on the status of the ongoing mission. Tools
developed at ESO, such as WDB or STARCAT, will be used appropriately.
---------------------------------------------------------
Title: The coronal aureole.
Authors: Fang, Y.; Lamy, P. L.; Llebaria, A.
1995A&A...293..208F Altcode:
We calculate the coronal aureole using the Fourier transform and we
show that the outer corona significantly contributed to its value. We
further propose a new, simple mathematical method which allows to derive
the scattering function directly from two observational images taken
successively during an eclipse. This method is successfully tested
using different models of the scattering function.
---------------------------------------------------------
Title: Pulsars at 1 MeV: the Crab and PSR 1509-58.
Authors: Combet, P.; Lamy, P. L.
1995AdSpR..15j..65C Altcode: 1995AdSpR..15R..65C
The Compton Imaging Telescope COMPTEL observed at an early stage of the
CGRO sky survey pulsed emission from the two classical γ-ray pulsars,
Crab and Vela. Further efforts were necessary to detect one of the
four new pulsars detected by the other CGRO instruments, namely PSR
1509-58. These are the only three pulsars detected so far at an energy
of 1 MeV. In spite of the similarity of their timing parameters, the
Crab pulsar and PSR 1509-58 display very different characteristics in
their MeV emissions, observed by COMPTEL.
---------------------------------------------------------
Title: HST Observations of Comet P/Faye 1991 XXI
Authors: Lamy, P. L.; Toth, I.; Grün, E.; Keller, H. U.; Sekanina,
Z.; West, R. M.
1994BAAS...26.1552L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Capabilities of the Cosmic Dust Analyser (CDA) for the
Mission CASSINI
Authors: Srama, R.; Grün, E.; Fechtig, H.; Jeßberger, E. K.;
Pernicka, E.; Lura, F.; Möhlmann, D.; Wäsch, R.; Ahrens, J.; Auer,
S.; Cruise, A. M.; Havnes, O.; Igenbergs, E.; Johnson, T. V.; Lamy,
P.; Morfill, G. E.; Schwehm, G. H.; Svestka, J.; Tuzzolino, A. J.;
Zook, H. A.; Cassini-Cda-Team
1994DPS....26.2109S Altcode: 1994BAAS...26.1142S
No abstract at ADS
---------------------------------------------------------
Title: HST Monitoring of Comet P/Shoemaker-Levy 9
Authors: Weaver, H. A.; Noll, K. S.; Storrs, A. D.; Smith, T. E.;
A'Hearn, M. F.; Arpigny, C.; Feldman, P. D.; Boice, D. C.; Stern,
S. A.; Lamy, P. L.; Larson, S. M.; Levy, D. H.; Scotti, J. V.; Marsden,
B. G.; Meech, K. J.; Shoemaker, C. S.; Shoemaker, E. M.; Sekanina,
Z.; Trauger, J. T.; Yeomans, D. K.; Zellner, B.
1994DPS....26.0101W Altcode: 1994BAAS...26.1564W
No abstract at ADS
---------------------------------------------------------
Title: IR Observations of the K and F Corona During the 1991 Eclipse
Authors: Kuhn, J. R.; Lin, H.; Lamy, P.; Koutchmy, S.; Smartt, R. N.
1994IAUS..154..185K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The potential of the dust grains of comet halley
Authors: Lamy, P.; Lafon, J. -P. J.; Dumas, C.
1993AdSpR..13j.259L Altcode: 1993AdSpR..13..259L
We calculate the electrostatic potential of silicate, graphite and
carbon submicronic grains in the coma of comet P/Halley located at
1 AU from the Sun using the “orbit-limited” solution. The physical
properties of the materials as well as the plasma parameters of the
subsolar cometosheath are taken into account. We find that the potential
lies between -3 and +4 volts in all cases, under likely conditions. It
could be negative, between 0 and -10 volts, if the plasma would be
a little more dense than usually admitted, as suggested by recent
measures.
---------------------------------------------------------
Title: Status of the LASCO Instrument Development Program
Authors: Moses, D.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.;
Korendyke, C. M.; Michels, D. J.; Socker, D. G.; Lamy, P.; Schwenn,
R.; Simnett, G. M.
1993BAAS...25.1192M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Absolute Photometry of the Dust Tail of Comet P/Halley
Authors: Lamy, P.; Malburet, P.
1993LPICo.810..178L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observation of Comet Faye (1991n) with the Hubble Space
Telescope
Authors: Lamy, P.; Toth, I.
1993LPICo.810..179L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Changing Properties of the Dust Coma of P/Halley: Implications
for an Inhomogeneous Nucleus
Authors: Lamy, P.; Cosmovici, C.; Schwarz, G.
1993LPICo.810..180L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Large Angle Spectroscopic Coronagraph (LASCO): visible
light coronal imaging and spectroscopy.
Authors: Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke,
C.; Michels, D. J.; Socker, D. G.; Lamy, P.; Llebaria, A.; Maucherat,
J.; Schwenn, R.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J.
1992ESASP.348...27B Altcode: 1992cscl.work...27B
The Large Angle Spectroscopic Coronagraph (LASCO) is a triple
coronagraph being jointly developed for the SOlar and Heliospheric
Observatory (SOHO) mission by the Naval Research Laboratory (USA),
the Laboratoire d'Astronomie Spatiale (France), the Max Planck
Institut für Aeronomie (Germany), and the University of Birmingham
(UK). LASCO comprises three nested coronagraphs (C1, C2, and C3)
that image the solar corona from 1.1 R<SUB><SUB>sun</SUB></SUB> to
30 R<SUB><SUB>sun</SUB></SUB>.
---------------------------------------------------------
Title: No Evidence of a Circumsolar Dust Ring from Infrared
Observations of the 1991 Solar Eclipse
Authors: Lamy, P.; Kuhn, J. R.; Lin, H.; Koutchmy, S.; Smartt, R. N.
1992Sci...257.1377L Altcode:
During the past 25 years there have been many attempts to detect a
possible dust ring around the sun, with contradictory results. Before
the 1991 eclipse, infrared eclipse experiments used single-element
detectors to scan the corona along the ecliptic for excess surface
brightness peaks. The availability of relatively large-format infrared
array detectors now provides a considerable observational advantage:
two-dimensional mapping of the brightness and polarization of the corona
with high photometric precision. The 1991 eclipse path included the
high-altitude Mauna Kea Observatory, a further advantage to measure the
corona out to large angular distances from the sun. Results are reported
from an experiment conducted on Mauna Kea with a HgCdTe-array detector
sensitive to wavelengths between 1 and 2.5 micrometers, using broad-band
J, H, and K filters. Although the sky conditions were not ideal, the H-
and K-band surface brightnesses clearly show the inhomogeneous structure
in the K-corona and the elliptical flattening of the F-corona, but no
evidence of a circumsolar, local dust component out to 15 solar radii.
---------------------------------------------------------
Title: LASCO - Large Angle Spectrometric Coronagraph for SOHO
Authors: Howard, R. A.; Brueckner, G. E.; Dere, K. P.; Korendyke,
C. M.; Koomen, M. J.; Michels, D. J.; Moses, D.; Socker, D. G.;
Schwenn, R.; Inhester, B.; Lamy, P.; Maucherat, A.; Simnett, G. M.;
Eyles, C.
1992AAS...180.3307H Altcode: 1992BAAS...24..781H
No abstract at ADS
---------------------------------------------------------
Title: The Physics and Dynamics of Charged Dust Grains
Authors: Lamy, P.
1992ibpd.conf..369L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Zodiacal Light
Authors: Lamy, P.
1992iawi.conf..251L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Laboratory Spectroscopy for ISO Report of the ISO Working-Group
Authors: Encrenaz, T.; Crovisier, J.; D'Hendecourt, L.; Lamy, P.;
Tully, J. A.
1992iawi.conf..141E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Data Analysis of the HST Observations of Comet P/Faye
Authors: Lamy, Ph.; Llebaria, A.; Adorf, H. -M.
1992ESOC...44..481L Altcode: 1992swhs.conf..481L
No abstract at ADS
---------------------------------------------------------
Title: Photomultiplier for optically probing Comet Halley
Authors: Giovane, Frank; Eichhorn, G.; McKisson, J.; Weinberg,
J. L.; Weisenberger, Andrew; Lamy, P.; Llebaria, A.; Detaille, M;
Levasseur-Regourd, A. C.; Le Blanc, J. M.
1991ApOpt..30.2579G Altcode:
A low mass eight-color channel photopolarimeter was developed
for the Giotto spacecraft. Utilizing the spin of the spacecraft,
a multichannel plate photomultiplier, and a unique optical design,
the instrument required no moving parts to measure color and linear
polarization. The photopolarimeter collected data as the spacecraft
passed through the coma of Comet Halley on March 13 and 14, 1986. This
instrument's design, calibration, and reduction are discussed and some
final results are presented.
---------------------------------------------------------
Title: Changing Properties of the Dust Coma of P/Halley: Implications
for an Inhomogeneous Nucleus
Authors: Lamy, P.; Cosmovici, C.; Schwarz, G.
1991LPICo.765..130L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Electric Effects on Cometary Grains
Authors: Lafon, J. P. J.; Lamy, Ph.; Bouzinac, C.
1991isrs.conf..213L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Physical Properties of Cometary Dust
Authors: McDonnell, J. A. M.; Lamy, P. L.; Pankiewicz, G. S.
1991ASSL..167.1043M Altcode: 1991cphe.conf.1043M; 1991IAUCo.116.1043M
Prior to the 1986 apparition of Comet Halley, all attempts to
determine the physical properties of cometary dust were limited to
remote observations and the analysis of various particles captured by
the earth's atmosphere. The in situ measurements made by the three
spacecraft that passed within 10,000 km of the nucleus provided the
first opportunity to investigate both the full size-range of particles
and the complete process of dust production. Information on composition
is derived through mass spectra and the scattering and emission of light
from the grains, while the dynamics of the dust coma can be modeled
from the three separate sets of measurements made over a period of
eight days.
---------------------------------------------------------
Title: Future Observations of the F-Corona with the LASCO Coronagraph
Space Experiment
Authors: Lamy, P. L.; Llebaria, A.; Maucherat, A.; Koutchmy, S.;
Giovane, F.
1991ASSL..173..191L Altcode: 1991IAUCo.126..191L; 1991oeid.conf..191L
No abstract at ADS
---------------------------------------------------------
Title: Synthetic Maps of the Brightness and Polarization of the
F-Corona
Authors: Fang, Y.; Lamy, P. L.; Llebaria, A.
1991ASSL..173..195F Altcode: 1991oeid.conf..195F; 1991IAUCo.126..195F
No abstract at ADS
---------------------------------------------------------
Title: The Optical Properties of Interplanetary Dust (invited Review)
Authors: Lamy, P. L.; Perrin, J. M.
1991ASSL..173..163L Altcode: 1991oeid.conf..163L; 1991IAUCo.126..163L
No abstract at ADS
---------------------------------------------------------
Title: On the Validity of Effective-Medium Theories in the Case of
Light Extinction by Inhomogeneous Dust Particles
Authors: Perrin, J. -M.; Lamy, P. L.
1990ApJ...364..146P Altcode:
The application of Maxwell-Garnett and Bruggeman effective-medium
theories to the problem of light scattering by inhomogeneous dust
particles is investigated. It is shown that in the framework of
classical electrodynamics these theories are not rigorously valid when
applied to particles. Numerical computations of scattering using a
discrete dipole approximation for very small grains composed of a matrix
material with embedded inclusions are carried out, and the results are
compared with results obtained using these effective-medium theories. It
is shown that the application of these theories to the studies of the
interactions of light with inhomogeneous dust particles is limited.
---------------------------------------------------------
Title: Optical linear polarization measurements of Comet Halley from
the Giotto Halley Optical Probe Experiment.
Authors: Weisenberger, A. G.; Giovane, F.; Eichhorn, G.; Lamy, P.;
Llebaria, A.
1990BAAS...22..744W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The dust tail of comet Halley.
Authors: Lamy, P. L.
1990ch2..book....1L Altcode: 1990ch......2....1L
Contents: 1. From early ages to the present day: an historical
perspective of cometary dust tails. 2. From streamers to striae:
a perspective on structures in cometary tails. 3. A good perspective
on the dust tail of comet Halley. 4. The dust tail of comet Halley in
1986. 5. Photopolarimetric properties of the tail and its modelling.
---------------------------------------------------------
Title: The color of the zodiacal light and the size distribution
and composition of interplanetary dust
Authors: Perrin, J. -M.; Lamy, P. L.
1989A&A...226..288P Altcode:
The color of the zodiacal light is studied in the general context
of light scattered by dust particles. It is shown that the color
is controlled by various mechanisms in a complex way. The spectral
variation of the complex index of refraction, the size distribution
function and the roughness of the dust grains all play a significant
role in the color of the scattered light. It is also shown that the
very geometrical conditions of observation of the zodiacal light result
in a color effect which depends upon the elongation.
---------------------------------------------------------
Title: Optical properties of irregular interstellar grains.
Authors: Perrin, J. M.; Lamy, P. L.
1989IAUS..135P.381P Altcode:
In order to study the interaction of light with interstellar grains,
the authors represent an irregular particle by a network of interacting
dipoles whose polarizability is determined in a first approach by
the Clausius-Mossoti relationship. Typically, 10000 dipoles are
considered. In the case of spherical particles, the results from Mie
theory are fully recovered.
---------------------------------------------------------
Title: Comet P/Halley at a heliocentric preperihelion distance of
2.6 AU - Jet activity and properties of the dust coma
Authors: Lamy, P. L.; Malburet, P.; Llebaria, A.; Koutchmy, S.
1989A&A...222..316L Altcode:
This paper presents an in-depth analysis of a high-resolution
photograph of comet P/Halley obtained on September 12, 1985 when it
was a heliocentric distance of 2.6 AU preperihelion. The coma has a
diameter of 138,000 km and exhibits structures which are interpreted
as three jets, one best seen in the outer part of the coma extending
to 29000 km and the two others, in the inner part extending to about
7000 km. The integrated magnitude and radial profiles of the coma are
given showing that the comet does not follow the simple steady-state,
radial outflow model. By combining the photometric result with nearly
simultaneous ultraviolet and infrared observations, it is found that
the strong reddening in the ultraviolet gradually levels off in the
visible as the color becomes neutral at 2 microns and blue beyond 3
microns. A geometric albedo at zero phase angle of 0.04 is obtained,
as well as a dust production rate of 30 to 120 kgs.
---------------------------------------------------------
Title: Infrared properties of rough cometary grains
Authors: Perrin, J. M.; Lamy, P. L.
1989AdSpR...9c.241P Altcode: 1989AdSpR...9..241P
In order to study the interaction of light with cometary grains,
we represent an irregular particle by a network of interacting
dipoles whose polarizability is determined in a first approach by
the Clausius-Mossiti relationship. Typically, 10000 dipoles are
considered. In the case of spherical particles, the results from Mie
theory are fully recovered. The main interest of this method is to
study with a good accuracy the implications of surface roughness and/or
inhomogeneities on optical properties in the infrared spectral range,
particularly of the silicate emission features.
---------------------------------------------------------
Title: Optical properties of organic grains: Implications for
interplanetary and cometary dust
Authors: Lamy, Philippe L.; Perrin, Jean-Marie
1988Icar...76..100L Altcode:
On the basis of the organic material "tholin" whose optical constants
have been measured by B. N. Khare et al. (1984, Icarus 60, 127-137),
we investigate the optical properties of tholin grains and find an
original behavior, intermediate between dielectric and absorbing
material. Solving for the interaction with the solar radiation field,
we obtain the ratio β of the radiation pressure and gravitational
forces and the temperature distribution. The temperature is a strong
function of the size of the grains with the submicron grains much
hotter than the blackbody. The presence of such an organic material in
cometary dust looks very promising for explaining several "puzzling"
observations such as the CN jets and the absence of the silicate
emission feature at heliocentric distances beyond ⋍1.5 AU.
---------------------------------------------------------
Title: Light scattering of large rough particles application to
cometary grains.
Authors: Lamy, Philippe L.; Perrin, J. M.
1988ioch.rept..156L Altcode:
While the electromagnetic field scattered by a spherical particle is
classically obtained by the Helmholtz equation, the general case of
an arbitrary particle may be investigated in the general framework of
the interaction of a wave with a scattering potential. A wave function
then satisfies the Schroedinger equation. The general solution of the
Schroedinger equation is given. The main disadvantage of this approach
are its restriction to large particles and its scalar nature preventing
the calculation of the polarization. However, Perrin and Lamy have
shown how to avoid the second limitation and retrieve a vectorial
description. They proved that in the case of large spheres when the
ad hoc assumptions are satisfied, the expression of the scattering
amplitude may be approximated by an expansion series in partial waves,
i.e., on a discrete basis. The analogy may be generalized, and the ratio
of the two components for a rough particle obtained by taking the ratio
of the reflectivities for the two directions of polarization. These
reflectivities involve the simple and double reflections calculated
following the method developed by Wolff for rough surfaces. The theory
is further detailed.
---------------------------------------------------------
Title: Laboratory Measurements of Light Scattering by Dust Particles
Authors: Bliek, P.; Lamy, P.
1988ASSL..149..253B Altcode: 1988ecda.book..253B
No abstract at ADS
---------------------------------------------------------
Title: Etude de la dynamique du nuage zodiacal par la mesure du
décalage Doppler.
Authors: Lamy, P.; Koutchmy, S.; Bücher, A.; Robley, R.
1988jopl.conf..227L Altcode:
At the Pic-du-Midi Observatory, the authors have started a program
to observe the spectrum of the zodiacal light in the region of
the b absorption lines of Mg I. They use a 1 m spectrograph with a
holographic grating followed by a focal reducer to obtain a 19 Å/mm
dispersion over the micro-channel plate camera. Calibrated spectra
obtained with an exposure time of 10 minutes systematically show earth
atmospheric emission lines attributed to both N I and OH. The temporal
variability of these emissions prevents an accurate determination of
the line profiles.
---------------------------------------------------------
Title: Observations et propriétés des poussières de la comète
de Halley.
Authors: Lamy, P.; Perrin, J. M.; Koutchmy, S.; Grün, E.; Llebaria,
A.; Malburet, P.
1988jopl.conf..211L Altcode:
The authors present the results of various observations and analysis
of the dust grains of comet Halley.
---------------------------------------------------------
Title: Comet P/Halley - Implications of the mass distribution function
for the photopolarimetric properties of the dust coma.
Authors: Lamy, P. L.; Gruen, E.; Perrin, J. M.
1987A&A...187..767L Altcode:
The dust particle fluences measured aboard the Vega (SP-1 and SP-2
impact sensors) and Giotto probes (DIDSY impact sensors) are analyzed
to obtain the differential size distribution function of the dust in
the coma of comet Halley. The brightness integral is then calculated
for perfectly spherical (Mie scattering) and rough grains of various
compositions. It is shown that the photopolarimetric observations
rule out the dominating presence of weakly obsorbing silicates such
as olivine but are compatible with rough moderately absorbing silicate
grains having a density decreasing with radius and with rough graphite
grains. A mixture of the two types gives in fact the best agreement
with the observations.
---------------------------------------------------------
Title: The Dust Tail of Comet p/ Halley in 1986APR
Authors: Lamy, P. L.; Pedersen, H.; Vio, R.
1987A&A...187..661L Altcode:
Images of the dust tail of comet Halley were obtained with the
ESO wide-field CCD camera during April 1986 with the Johnson B,
V and R filters in polarized light. An analysis of selected images
taken on April 6 and 11, processed for photometric analysis, is
presented. Results are given for the absolute brightness, the color,
the polarization and its variation with wavelength.
---------------------------------------------------------
Title: Compatibility of the in-situ mass distribution with
photopolarimetricobservations of comet Halley.
Authors: Lamy, P. L.; Grün, E.; Perrin, J. M.
1987ESASP.278..409L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Similarity and diversity of the polarization of comets.
Authors: Perrin, J. -M.; Lamy, P. L.
1987ESASP.278..411P Altcode: 1987dsc..proc..411P
The polarization measurements of the dust coma of 10 comets
including P/Halley were analyzed. Separation of the dust from the gas,
emphasizing the value of the narrow-band and spectropolarimetric data,
is outlined. Polarization curves are deduced, implying unambiguous
differences in the physical properties of the cometary dust. The
negative branch of polarization is discussed and intepreted as
suggesting a rough surface for the grains.
---------------------------------------------------------
Title: Book Review: Interrelationship among circumstellar,
interstellar, and planetary dust. Edited by Joseph A. Nuth III and
Robert E. Stencel. NASA Conference Publication 2403, Proceedings of
a workshop held at the Aspen Institute's Wye Plantation Conference
Center, Wye, MD, February 27 to March 1, 1985
Authors: Lamy, Philippe L.
1987Icar...71..198L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: B00K-REVIEW - Properties and Interactions of Interplanetary
Dust
Authors: Giese, R. H.; Lamy, P.
1987Sci...236.1009G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Night sky optical spectrum from a high altitude observatory.
Authors: Louistisserand, S.; Bucher, A.; Koutchmy, S.; Lamy, P.
1987A&AS...68..539L Altcode:
Night sky spectrum between 380 and 660 nm with effective spectral
resolution of 0.2 nm is presented for evaluation of effects
produced by the different sources of light including lights of urban
origin. Numerous emission lines superposed on a continuum spectrum
are identified.
---------------------------------------------------------
Title: Radiation pressure and temperature of Beta Pictoris
circumstellar dust grains.
Authors: Lamy, P.
1987BAAS...19..633L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book-Review - Properties and Interactions of Interplanetary
Dust 85TH Colloquium I.A.U. / Marseille 1984
Authors: Giese, R. H.; Lamy, P.
1987ApL....25..270G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book-Review - Properties and Interactions of Interplanetary
Dust - 85TH Colloquium of the I.A.U. Marseille - 1984
Authors: Giese, R. G.; Lamy, P.
1987ApL....25..265G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ground-Based Large-Scale Monochromatic Images of Comet Halley
during the Giotto Flyby
Authors: Koutchmy, S.; Lamy, P.; Loucif, M.; Malburet, P.
1986ESASP.250c..79K Altcode: 1986ehc3.conf...79K
A wide-field camera (f = 135 mm) equipped with an image-tube was set up
at the geophysical observatory of Tamanrasset during the first half of
March. Monochromatic images were obtained in CN (390 nm), CO<SUP>+</SUP>
(426.3 nm) and in the continuum (582 nm), in March 14.19, a few hours
after the Giotto flyby.
---------------------------------------------------------
Title: The Dust Tail of Comet Halley: Brightness, Colour, Polarisation
Authors: Lamy, P.; Pedersen, H.; Vio, R.
1986ESASP.250b..69L Altcode: 1986ehc2.conf...69L
Images of the dust tail of comet Halley were obtained with the ESO
wide-field CCD camera during April 1986 with the Johnson B, V and
R filters in polarized light. A preliminary analysis of selected
images taken on April 6 and 11, processed for photometric analysis,
is presented. Results are given for the absolute brightness, the color,
the polarization and its variation with wavelength.
---------------------------------------------------------
Title: Comet Halley: Implications of the Impact Measurements for
the Optical Properties of the Dust
Authors: Lamy, P. L.; Perrin, J. -M.
1986ESASP.250b..65L Altcode: 1986ehc2.conf...65L
The cumulative mass flux function obtained by VEGA-2 SP-2 impact
instrument is used to calculate the brightness integral, for grains
of various compositions, in the framework of Mie theory and of the
authors' model for light scattering by rough grains. Polarization
for large scattering angles and color in the ultra violet and visible
range are also obtained. The results are compared with the space and
ground-based observations. General indications on the properties of
cometary dust are outlined.
---------------------------------------------------------
Title: Inner Coma Dust and Gas as a Function of Distance to the
Nucleus: Measurements from Giotto
Authors: Levasseur-Regourd, A. C.; Bertaux, J. -L.; Dumont, R.;
Eichhorn, G.; Festou, M.; Giese, R. H.; Giovane, F.; Lamy, P.; Leblanc,
J. M.; Llebaria, A.; Weinberg, J. L.
1986ESASP.250c.232L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Early resolved structures in the coma of Comet Halley
Authors: Dossin, F.; Guerin, P.; Koutchmy, S.; Lamy, P.; Malburet, P.
1986ESASP.250b.173D Altcode: 1986ehc2.conf..173D
Three high-resolution photographs of comet Halley were obtained on
September 12, 1985 with the Schmidt telescope operated by CNRS and
Liège University at the Observatoire de Haute-Provence on hypered
Kodak 2415 film and exposure times of 1 hour. The best image (FWHM
of 2 arcsec) has been analyzed in order to deduce the 2-dimensional
distribution of light presumably scattered by the dust. Two jet-like
structures are present in the near nuclear region, one extending outward
up to 15 arcsec. The total absolute magnitude has also been determined.
---------------------------------------------------------
Title: Book-Review - Properties and Interactions of Interplanetary
Dust
Authors: Giese, R. H.; Lamy, P.; Ingham, M. F.
1986Obs...106..130G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book-Review - Properties and Interactions of Interplanetary
Dust
Authors: Giese, R. H.; Lamy, P.
1986S&T....72Q..41G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Volume scattering function and space distribution of the
interplanetary dust cloud
Authors: Lamy, P. L.; Perrin, J. -M.
1986A&A...163..269L Altcode:
The Volume Scattering Function (VSF) and the spatial distribution of the
interplanetary dust cloud are examined by inversion of the brightness
integral of the F-corona and the zodiacal light. Intensity and
polarization observations are used to produce functional representations
in the plane of symmetry of the interplanetary cloud, in the meridian
plane, and at selected ecliptic latitudes. A modified fan model is
shown to be compatible with the brightness data at d = 1 and 0.3 AU,
and indicates that the VSF and the local polarization depend upon
the heliocentric distance of the observer, but are independent of the
latitude. The variations of the VSF and the polarization with respect
to the scattering angle may be explained by the preferential removal
of absorbing grains as beta-meteoroids.
---------------------------------------------------------
Title: Inner Coma Dust and Gas in Comet Halley as a Function of
Distance to the Nucleus: Measurements from GIOTTO
Authors: Levasseur-Regourd, A. -C.; Bertaux, J. L.; Dumont, R.;
Eichhorn, G.; Festou, M. C.; Giese, R. H.; Giovane, F.; Lamy, P.;
Leblanc, J. M.; Llebaria, A.; Weinberg, J. L.
1986BAAS...18..790L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Properties of Organic Interplanetary Grains
Authors: Lamy, P. L.; Perrin, J. M.
1986BAAS...18..820L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book-Review - Properties and Interactions of Interplanetary
Dust
Authors: Giese, R. H.; Lamy, P.
1986Sci...232.1654G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Optical probing of comet Halley from the Giotto spacecraft
Authors: Levasseur-Regourd, A. C.; Bertaux, J. L.; Dumont, R.; Festou,
M.; Giese, R. H.; Giovane, F.; Lamy, P.; Le Blanc, J. M.; Llebaria,
A.; Weinberg, J. L.
1986Natur.321..341L Altcode:
The Halley optical probe experiment (HOPE) aboard the Giotto spacecraft
has provided the first measurements of the optical properties of the
dust and of some gaseous species (CN, C<SUB>2</SUB>, CO<SUP>+</SUP> and
OH) from inside the coma of comet Halley. The dust spatial distribution,
inferred from sunlight scattering, obeys an r<SUP>-2</SUP> law for
distances from the nucleus r>=2,000 km. The more rapid increase of
dust density with distance observed in the innermost coma probably
reflects the presence of a jet, or a surge of activity within a few
hours before closest approach. The CN and OH signals increase more
slowly than the dust signals, but faster than predicted by a simple
model (of solar-excited resonance fluorescence) for the distribution
of these species<SUP>1</SUP>. This effect is probably caused in part
by the dust contribution, as well as by the production from parent
molecules of OH and CN in an excited state.
---------------------------------------------------------
Title: The Giotto optical probe experiment
Authors: Levasseur-Regourd, A. C.; Bertaux, J. L.; Dumont, R.; Festou,
M.; Giese, R. H.; Giovane, F.; Lamy, P.; Llebaria, A.; Weinberg, J. L.
1986gmis.rept..187L Altcode:
The Halley Optical Probe Experiment (HOPE) was designed to provide
in-situ photopolarimetric data on the dust cloud and the gaseous
atmosphere in Halley/s coma. The probe concept, instrumentation,
and possibilities for cross-correlation between the HOPE results and
those of other space and ground-based experiments are presented. The
instrument was turned on successfully on 13 September 1985.
---------------------------------------------------------
Title: Periodic Comet Halley (1982i)
Authors: Ney, E. P.; Knutson, A. G.; Wootten, Alyn; Loren, R.;
Koutchmy, S.; Lamy, P.
1986IAUC.4161....1N Altcode:
E. P. Ney and A. G. Knutson, University of Minnesota, report the
following infrared magnitudes measured with a 26" diaphragm at the
O'Brien Observatory: 1985 Dec. 12.08 UT, K = 6.8, L = 6.1, [8.6 micron]
= -0.5, N = -1.8, [12.5 micron] = -1.9, [18 micron] = -3.3; Dec. 14.00,
[8.6 micron] = 0.9, N = -0.8, [12.5 micron] = 0.0, [18 micron] = = -2.8;
Dec. 25.05, J = 6.8, K = 7.1, L = 5.2, M = 3.1, [8.6 micron] = -0.5,
N = -1.6, [12.5 micron] = -1.6, [18 micron] = -3.0; 1986 Jan. 1.0, N =
-1.4, [12.5 micron] = -0.9; Jan. 7.9, H = 6.0, K = 6.1, L = 3.9, M =
1.2, [8.6 micron] = -1.5, N = -2.8, [12.5 micron] = -2.6, [18 micron]
= -4.0. The silicate feature at 10 micron is ~ 0.5 mag above the
continuum. A. Wooten, National Radio Astronomy Observatory, reports:
"R. Loren, University of Texas, obtained spectra of P/Halley in the
region of the P(2,1) line of protonated water (H3O+) at 307.19241 GHz
on Jan. 6 with the 4.9-m telescope of the Millimeter Wave Observatory
at Fort Davis. No emission was detected, rms(TR*) = 0.85 placing a
preliminary upper limit of 5 x 10**-27 s**-1 for the H3O+ production
rate. Receiver tuning was verified through observation of CHEOH at
307.16594 GHz in OMC-1." S. Koutchmy, Institut d'Astrophysique, Paris;
and P. Lamy, Laboratoire d'Astronomie Spatiale, Marseilles, telex that
100 image-tube spectra (180 A/mm resolution, range 350-700 nm) were
obtained with the Haute Provence Observatory's 0.8-m telescope during
1985 Dec. 10-15. CN emission was detected, extending up to 2 deg away
from the sun, but no ions were noted until Dec. 12. From Dec. 13.8 UT
onward the N2+ (0,0) line at 391.4 nm was seen in the vicinity of the
coma and extending in the antisolar direction up to 2 deg. Observations
with the Marly spectrograph (range 326-526 nm, dispersion 80 A/mm,
slit width 50 micron, slit length projection 3'7, IIa-O hypered plates)
on the 1.20-m f/6 telescope during 1985 Dec. 2.76-2.98 and 3.72-3.97
UT revealed CN, C2 and C3 (all well observed); N2+ (0,0) extending
over 16"; CO+ (3,0) lines at 400.18 and 402.4 nm extending over 37"
and 14", respectively; CO2+ (0,1) at 367.4 nm was suspected; numerous
Fraunhofer absorption lines (including H and K and several Fe lines)
were also noted. Photographs (hypered IIIa-J and 2415 emulsions) of
the plasma tail with the 0.62-m f/3.5 and 0.30-m f/2 Schmidt telescopes
during Dec. 3- 15 revealed an inner part (extending < 1 deg from the
head) whose orientation oscillated about the antisolar direction with a
maximum deviation of + 5P and a characteristic time of one to two days.
---------------------------------------------------------
Title: Cometary dust: observational evidences and properties.
Authors: Lamy, P. L.
1986acm..proc..373L Altcode:
Cometary dust in both the coma and the tail is observed by its
scattered light and its thermal emission provided that they are
carefully separated from the emission lines. Color, phase function,
polarization and spectral signatures are the basic properties
which help in characterizing the dust grains. There do not appear
to be systematic differences among various comets as the reddening,
the strong forward scattering and the polarization behavior appear
to be wide-spread common features also shared by interplanetary dust
grains. The interpretation of some of these features in terms of rough,
slightly absorbing grains is discussed.
---------------------------------------------------------
Title: The Giotto Optical Probe Experiment.
Authors: Levasseur-Regourd, A. C.; Bertaux, J. L.; Dumont, R.; Festou,
M.; Giese, R. H.; Giovane, F.; Lamy, P.; Llebaria, A.; Weinberg, J. L.
1986ESASP1070..187L Altcode:
The Halley Optical Probe Experiment (HOPE) has been designed to
provide in-situ photopolarimetric data on both the dust cloud and the
gaseous atmosphere in Halley's coma. The Optical Probe's concept is
presented here, together with a description of the instrumentation
and the possibilities for cross-correlation between the HOPE results
and those of other space and ground-based-experiments. The instrument
was turned on successfully on 13 September 1985.
---------------------------------------------------------
Title: Periodic Comet Halley (1982i)
Authors: Jewitt, D.; Meech, K.; Ricker, G.; Lamy, P.; Koutchmy, S.;
Vial, J. C.
1985IAUC.4148....1J Altcode:
D. Jewitt, K. Meech, and G. Ricker, Massachusetts Institute of
Technology, communicate: "Observations from McGraw-Hill Observatory
on Kitt Peak over 4 nights show variable structures in the inner
coma of P/Halley. Images were taken through broad and narrowband
interference filters using the MIT 'MASCOT' CCD camera on the 1.3-m
telescope. Jet-like structures were observed in position angles 358
and 313 on Nov. 29 UT. The jets extended 10 000 km in the plane of
the sky and had widths comparable to the atmospheric seeing. The
jets were visible in both broad and narrowband continuum filters and
are probably dust features. The jets showed no variation in position
angle or brightness in an observing interval of > 3 hr but were
absent on the preceding and following nights." Meech and Jewitt also
report: "Observations of P/Halley with the Kitt Peak 0.61-/0.91-m
Schmidt telescope (with baked IIIa-J plates and exposure times
30-60 min) show that extensive tail development has occurred within
the past month. Observations on Nov. 6-9 showed only a transient,
faint anti-solar tail (length 20' on Nov. 6.20) which faded in <
1 day. Observations on Dec. 4-8 show a persistent plasma tail (length
> 2.5 deg) displaying a classical streamer morphology. We are able
to follow knots, kinks, and streamers in the tail for up to 6 hr. The
measured speeds of 3 tail knots are 190, 216, and 240"/hr (39, 45, and
50 +/- 5 km/s along the tail, km/s), considerably less than the solar
wind speed but similar to the speeds measured in the tails of other
comets. No evidence for acceleration of the features is seen. Two
episodes of ray formation have been seen in 25 hr of observation;
the rays form in ~ 1 hr and evolve over several hr, but fade in <
18 hr. The tail as a whole shows gross brightness changes from night
to night. No dust tail is seen." P. Lamy, Laboratoire d'Astronomie
Spatiale, Marseille, and S. Koutchmy, Institut d'Astrophysique, Paris,
telex: "Four consecutive 1-hr-exposure IIIa-J hypered plates obtained
between Dec. 6.79-6.96 UT by Koutchmy and J. C. Vial with the 0.62-m
f/3 Schmidt telescope of Haute Provence Observatory show a disturbed,
narrow, plasma tail of length > 2 deg. The tail's inner part
deviates southward from the anti-solar direction by 4.8 +/- 0.7 deg;
the outer part widens and nears the anti-solar direction. The point
of bifurcation seems to move radially outward with time."
---------------------------------------------------------
Title: Zodiacal Light and the Spatial Density of Interplanetary Grains
Authors: Lamy, P. L.; Perrin, J. M.
1985ASSL..119..239L Altcode: 1985piid.proc..239L; 1985IAUCo..85..239L
Using the Lamy and Perrin (1980) model of light scattering by large,
rough grains, the compatibility of the observed properties of the
zodiacal light with models of the spatial density of interplanetary
grains is investigated. The agreement is not yet satisfactory and
probably calls for further revision of the density distribution
function. The previous conclusion that submicronic grains gives a
nonnegligible contribution is confirmed.
---------------------------------------------------------
Title: Ground-based observations of the dust emission from comet
Halley
Authors: Lamy, P.
1985AdSpR...5l.317L Altcode: 1985AdSpR...5..317L
A preliminary analysis of the dust emission from comet Halley is
presented based on large scale observations of its dust tail. Selected
images obtained between February 22 and May 10, 1986 are compared to
synchrone-syndyne graphs to infer the history of the dust production
and the properties of the dust, at least qualitatively. Quantitative
modeling of the dust tall has also been initiated and preliminary
results are shown for the cases of isotropic and anisotropic (jet)
dust production.
---------------------------------------------------------
Title: The F-Corona and the Circum-Solar Dust Evidences and Properties
(ir)
Authors: Koutchmy, S.; Lamy, P. L.
1985ASSL..119...63K Altcode: 1985IAUCo..85...63K; 1985piid.proc...63K
This review deals with the main properties of the F-corona. Analysis
of its morphology and photometry allows to derive a new axisymmetric,
non-spherical model. Polarization, color and infra-red properties are
further considered. The authors suggest the existence of a variable
"local" component superimposed on a quasi-stationary "far" component.
---------------------------------------------------------
Title: In-situ photopolarimetric measurements of dust and gas in
the coma of Halley's comet
Authors: Levasseur-Regourd, A. -C.; Bertaux, J. -L.; Le Blanc, J. M.;
Weinberg, J. L.; Giovane, F.; Dumont, R.; Festou, M.; Giese, R. H.;
Lamy, P.; Llebaria, A.
1985AdSpR...5l.197L Altcode: 1985AdSpR...5..197L
The Halley Optical Probe Experiment (HOPE) on board the Giotto
spacecraft has provided the first in-situ measurements, both of the
dust and of some gaseous species, from inside the coma of the comet. The
instrument has already been described /1/, together with first results
/2/. The purpose of this note is to show how optical measurements can
lead to in-situ information, how those were obtained during the 13-14
march 1986 Halley fly-by, and what is the status of the data analysis.
---------------------------------------------------------
Title: Preliminary Results of a Dust Scattering Experiment
Authors: Bliek, P.; Lamy, P. L.; Courtes, G.
1985ASSL..119..231B Altcode: 1985IAUCo..85..231B; 1985piid.proc..231B
An experimental device of the nephelometer type for the study of the
scattering properties of dust particles is presented. A fluidized bed
generator produces a continuously flowing aerosol which is illuminated
by either a He-Ne laser or a Xenon arc lamp with interference
filters. The size of the dust particles ranges between 1 and 30
microns. The scattering properties of dust particles are measured in
the two directions of polarization. The first results are presented.
---------------------------------------------------------
Title: Properties and interactions of interplanetary dust
Authors: Giese, R. H.; Lamy, P.
1985ASSL..119.....G Altcode: 1985piid.proc.....G; 1985IAUCo..85.....G
The conference presents papers on zodiacal light and F-coronal
observations as well as space, ground, laboratory and optical
studies of interplanetary dust, the relationship between this dust
and comets, its interactions with plasma, its dynamics and spatial
distribution. Particular attention is given to ground-based observations
of near ecliptic zodiacal light brightness, the change in near-ecliptic
zodiacal light brightness with heliocentric distance, IRAS observations
of interplanetary dust emission, and observation of the F-corona radial
velocities field between 3 and 7 solar radii. Other topics include
orbits of interplanetary dust particles inside 1 AU as observed by
Helios, chemical and isotopic compositons of refractory elements in deep
sea spherules, optical models of the three dimensional distribution
of interplanetary dust, the particle-size-distribution function of
cometary dust, laboratory simulation of chemical interactions of
accelerated ions with dust and ice grains, and an analysis of IRAS'
solar system dust bands.
---------------------------------------------------------
Title: Doppler Shifts Measurements of the Zodiacal Light at the PIC
Midi Observatory
Authors: Robley, R.; Buecher, A.; Koutchmy, S.; Lamy, Ph.
1985ASSL..119...85R Altcode: 1985IAUCo..85...85R; 1985piid.proc...85R
The authors have started a program to observe the spectrum of the
zodiacal light in the region of the b absorption lines of Mg I. They
use a 1 meter spectrograph with a holographic grating followed by a
focal reducer to obtain a 19 Å/mm dispersion over the micro-channel
plate camera. Calibrated spectra obtained with an exposure time of 10
minutes systematically show earth atmospheric emission lines attributed
to both N I and OH. The temporal variability of these emissions
prevents an accurate determination of the line profiles. The authors
best processed measurements of Doppler shifts obtained during five
nights do not allow to discriminate between circular and hyperbolic
orbits of the interplanetary dust.
---------------------------------------------------------
Title: Optical Properties of Rough Grains: a Theoretical Study
Authors: Perrin, J. M.; Lamy, P. L.
1985ASSL..119..245P Altcode: 1985IAUCo..85..245P; 1985piid.proc..245P
Recent work on the light scattering by large rough particles has led
the authors to propose a model based on the high-energy approximation,
the laws of geometrical optics and a mathematical description of the
properties of the particle roughness. The influence of the various
parameters of the model including those characterizing the roughness
on the total intensity and the polarization is presented.
---------------------------------------------------------
Title: Some Remarks on the Density of Interplanetary Dust Grains
Authors: Lamy, P. L.
1985ASSL..119..137L Altcode: 1985piid.proc..137L; 1985IAUCo..85..137L
The relevance of the bulk density as a physical parameter characterizing
interplanetary dust grains is discussed. The various measurements which
lead to a determination of this parameter are reviewed. The specific
case of the collected interplanetary dust grains is considered.
---------------------------------------------------------
Title: A Coronascanner for a Sun Oriented Space Mission
Authors: Koutchmy, S.; Lamy, P. L.
1985ASSL..119..141K Altcode: 1985IAUCo..85..141K; 1985piid.proc..141K
No abstract at ADS
---------------------------------------------------------
Title: Photographic Observations of the Inner Zodiacal Light Aboard
Saliout 7
Authors: Nikolskii, G.; Koutchmy, S.; Lamy, P. L.; Nesmianovich, I. A.
1985ASSL..119....7N Altcode: 1985IAUCo..85....7N; 1985piid.proc....7N
Color photographs of the inner zodiacal light were obtained aboard
Salyut 7 with Kodak Ekta 400. Absolute calibrations were performed
in-flight with attenuated sunlight. The photometric analysis was carried
out in three colors and corrections were introduced for the O I emission
of the F layers. The brightness of the zodiacal light along the ecliptic
is found in good agreement with published data while its color is found
slightly redder than the sun. Its out-of-ecliptic variation coincides
neither with the fan nor the ellipsoidal model; the photometric axis
is found near the projection of the orbital plane of Venus.
---------------------------------------------------------
Title: Astrophysical and geophysical observations with piramig/salyut
7 experiment
Authors: Levasseur-Regourd, A. C.; Courtes, G.; Herse, M.; Koutchmy,
S.; Lamy, P.; Muliarchik, T. M.; Rocca-Volmerange, B.; Savchenko,
S. A.; Secher, B.; Tovmassian, H. M.; Beresovoy, A. N.; Chretien,
J. L.; Ivanchenkov, A. S.; Djanibekov, V. A.; Lebedev, V. V.; Popov,
L. I.; Savitskaya, S. E.; Serebrov, A. A.
1985AdSpR...5c..27L Altcode: 1985AdSpR...5...27L
The facility offered by the Salyut 7 vehicle has allowed
teams of scientists of 3 CNRS french laboratories to develop
an instrument optimized for several disciplines in astrophysics
and geophysics. P.I.R.A.M.I.G. (Photography Infra-Red Atmosphere,
Interplanetary Medium, Galaxies) is a wide field (10° and 40°) camera
devoted to high sensitivity photographic photometry. The spectral
range is limited to the visible and near-infrared (400-850 nm), the
main advantage being to observe above the absorving and emitting layers
of the atmosphere.
---------------------------------------------------------
Title: Electrostatic Charge of Interplanetary Dust Grains: New Results
Authors: Lamy, P. L.; Lefevre, J.; Millet, J.; Lafon, J. P.
1985ASSL..119..335L Altcode: 1985IAUCo..85..335L; 1985piid.proc..335L
A continuing program aimed at improving the determination of the charge
of interplanetary as well as cosmic grains is presented. Recent data
have been combined to generate two high-resolution solar spectra
corresponding to the maximum and minimum of activity. The energy
distribution of photoelectrons emitted by quartz grains under solar
irradiation is calculated using the new laboratory measurements of
Quemerais et al. (1986). Finally, the method of Lafon, Millet and Lamy
(1981) is used to find the electrostatic potential of these grains.
---------------------------------------------------------
Title: A spectral photopolarimeter for Giotto: Halley optical probe
experiment
Authors: Levasseur-Regourd, A. C.; Bertaux, J. L.; Dumont, R.;
Festou, M. C.; Giese, R. H.; Giovane, G.; Weinberg, J. L.; Lamy, P.;
Llebaria, A.
1984AdSpR...4i.287L Altcode: 1984AdSpR...4..287L
The Halley Optical Probe Experiment (HOPE) is designed to provide in
situ photopolarimetric data on both the dust cloud and the gaseous
atmosphere in Halley's coma. The optical probe concept is presented
here, together with a description of the instrumentation and with the
possibilities for cross-checks between HOPE results and those of other
space and ground-based experiments.
---------------------------------------------------------
Title: The Betelgeuse shell : CCD/Fabry-Perot surface brightness
photometry at K I lambda 7699A and mass loss.
Authors: Mauron, N.; Fort, B.; Querci, F.; Dreux, M.; Fauconnier,
T.; Lamy, P.
1984A&A...130..341M Altcode:
Surface brightness photometric measurements of the Betelgeuse
circumstellar shell at K I 7699 A were observed with a Fabry-Perot
etalon and a CCD camera. Emission strength decreased as r exp -3.5 +
or - 0.8, where r is the distance from the star. Also noted was that
the emission strength, related to the mass-loss rate, and the slope
of the decreasing intensity, related to the K I ionization and the
density distribution, did not agree with values obtained by Honeycutt et
al. (1980), but did concur with the model of Jura by Morris (1981). A
mass-loss rate of 4 x 10 to the -6th solar mass/year was presented and
the carbon scarcity in the shell was decreased to a factor of six. A
slight departure from symmetry was found and tentatively attributed
to photospheric brightness asymmetry.
---------------------------------------------------------
Title: Optical properties of cometary grains: a new model.
Authors: Lamy, P. L.; Perrin, J. M.
1983UppOR..25...49L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Nature, origin and evolution of interplanetary dust grains.
Authors: Lamy, P. L.
1983HiA.....6..427L Altcode:
The survey is based for the most part on studies carried out
in recent years at the Laboratoire d'Astronomie Spatiale, in
Marseille (France). The topics covered are the size distribution and
physical properties of interplanetary dust grains, collisions among
interplanetary dust grains, the implications for zodiacal light,
and mass flux at 1 AU. A summary is given of the work presented by Le
Sergeant d'Hendecourt and Lamy (1980). In discussing collisions among
interplanetary dust grains, it is noted that certain investigators
(Zook and Berg, 1975; Dohnanyi, 1976) have proposed that the population
'2' of small, essentially submicronic grains could be the fragments of
collisions between large grains ejected by radiation pressure, thereby
creating an outflow of what are called 'beta-meteoroids' as detected
by Pioneer 8 and 9. In another study by Le Sergeant d'Hendecourt and
Lamy (1981), this mechanism was examined, and it was concluded that
the calculated flux of fragments could not match by far the observed
flux of submicronic grains.
---------------------------------------------------------
Title: Optical properties of rough cometary grains
Authors: Lamy, Ph. L.; Perrin, J. M.
1983acm..proc..273L Altcode:
The authors use their new model of light scattering by large rough
particles to investigate the optical properties of cometary grains. The
efficiency factor for extinction increases rapidly with increasing
roughness while that for absorption remains fairly constant and while
the ratio of radiation pressure to gravity decreases.
---------------------------------------------------------
Title: Widefield Ultraviolet Observations of Comet Halley with the
FAUST SPACELAB-1 Instrument
Authors: Bowyer, S.; Courtes, G.; Kimble, R.; Deharveng, J. M.;
Malina, R. F.; Lamy, P.
1983rrsb.conf..207B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Large-scale Photographic Observations, Photometry, Colorimetry
and Polarimetry of Cometary Tails
Authors: Lamy, P. L.; Koutchmy, S.
1982ncgb.conf..243L Altcode: 1982gbhc.work..243L
The use of large-scale photographic observations to characterize
the dust tails of comets is discussed, with emphasis on plans being
developed for observing Halley's Comet in 1986. The techniques used to
investigate the geometric structure of the dust tail and its evolution
(including detached structures, bursts, striae, and large-scale
extensions), the integrated magnitude from blue to far IR, and color
and polarization parameters are reviewed and illustrated with data
and images from recent studies of other comets. The requirements
for a network of identical cameras for Halley observations are
examined: minimum 30-deg field of view, spectral coverage and filter
separation, polarizers, calibration, color emulsions, and data-reduction
schemes. Many of the problems inherent in ground observations programs
could be avoided by using a space instrument such as the very-wide-field
camera flown on the first Spacelab mission; this device is briefly
described.
---------------------------------------------------------
Title: Wide field ultraviolet observations of Comet Halley with the
FAUST Spacelab I instrument
Authors: Bowyer, S.; Kimble, R.; Malina, R. F.; Lamy, P.; Courtes,
G.; Deharveng, J. M.
1982AdSpR...2l.207B Altcode: 1982AdSpR...2..207B
The wide field (7.5°), arc minute imaging, and spectroscopic
capabilities of the Far Ultraviolet FAUST telescope which will be flown
on Spacelab I can provide valuable information on Comet Halley. The
use of the FAUST instrument in obtaining images of the hydrogen coma
at 1216 Å, and in obtaining objective grating spectroscopy from
1300-3300 Å of the comet and tail, are described. The FAUST images
would provide large field of view data that are required for model
calculations of gas production rates and the determination of scale
lengths and lifetimes of ion species.
---------------------------------------------------------
Title: A coronographic mode for large telescopes.
Authors: Courtes, G.; Lamy, P.; Mauron, N.; Saisse, M.
1982ASSL...92...73C Altcode: 1982IAUCo..67...73C; 1982ialo.coll...73C
Lyot's coronographic technique of stray-light reduction has been applied
to the Faint Object Camera of the Space Telescope. In addition, the
application of the coronographic mode to the design of the Mount Chiran
1-m and ESO 3.6-m Ritchey-Chretien telescopes has given new levels of
performance in the detection of faint features in stellar and planetary
observations. As an example, observations of a new satellite of Saturn,
1980 S10 (Dione B), are examined.
---------------------------------------------------------
Title: An Opportunity for the Observations of Comets with Widefield
Cameras Aboard the Salyut Space Station
Authors: Lamy, P. L.; Koutchmy, S.
1981motc.conf..190L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Collisional processes among interplanetary dust grains:
An unlikely origin for the β meteoroids
Authors: Le Sergeant Dhendecourt, L. B.; Lamy, P. L.
1981Icar...47..270L Altcode:
The question of the collisional production of the β meteoroids is
reexamined incorporating recent experimental results (A. Fugiwara,
G. Kamimoto, A. Tsukamoto, 1977, Icarus31, 277-288). The collisional
model yields a flux of fragments supported by the conservation of mass
flux which does not account by far for the observed flux of submicron
grains. Particles larger than about 100 μm will be destroyed by
collisions inside 1 AU, well before they can get near the Sun. The
existence of two independent populations of interplanetary dust grains
as proposed by L. B. Le Sergeant and Ph. L. Lamy (1978, Nature266,
822-824; 1980, Icarus43, 350-372) appears reinforced. It is proposed
that the bulk of submicron grains does not necessarily travel in
hyperbolic orbits and that β meteoroids may be a phenomenon—possibly
transitory—of limited importance.
---------------------------------------------------------
Title: Observations of Saturn's outer ring and new satellites during
the 1980 edge-on presentation
Authors: Lamy, P. L.; Mauron, N.
1981Icar...46..181L Altcode:
Observations of Saturn's satellites and external rings during the 1980
edge-on presentation were obtained with a focal coronograph. A faint
satellite traveling in the orbit of Dione and leading it by 72° has
been detected, together with the two inner satellites already suspected
(cf. J. W. Fountain and S. M. Larson, 1978,Icarus36, 92-106). The
external ring has been observed on both east and west sides; it may
extend up to ⋍8.3 Saturn radii, and appears structured.
---------------------------------------------------------
Title: Infrared Imaging and Speckle Observations with a TV Camera
Authors: Lamy, P.; Koutchmy, S.
1981Msngr..23....5L Altcode:
The lack of suitable two-dimensional detectors has been a major
problem for infrared imaging in astronomy, and most results so far have
been obtained by scanning the object with a single detector (e. g.,
Terrile and Westphal,lcarus, 30, 730, 1977). The relative merit of
both techniques was thoroughly investigated by Hall (Applied Optics,
10, 838, 1971) who concluded that, below about 2.5 ~lm, camera tubes
should be preferred to scanners. Besides, sufficiently long times
required by the scanning technique are not always available for some
astronomical applications. These considerations led us to acquire a
standard television camera equipped with an infrared vidicon tube N156
manufactured by Hamamatsu Co. (Japan).
---------------------------------------------------------
Title: Satellites of Saturn.
Authors: Lamy, P.
1981IAUC.3572....2L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Satellites of Saturn
Authors: Lamy, P.
1981IAUC.3574....2L Altcode:
P. Lamy, Laboratoire d'Astronomie Spatiale, Marseilles, telexes that
further examination of plates taken at the Haute Provence Observatory
(cf. IAUC 3463, 3491) reveals a new satellite, 1980 S 29, of mag ~
14.5 to 15. On 1980 Mar. 16.126 UT, 1980 S 29 was located 19".75 east
of Saturn. It may correspond to one or more of 1980 S 7, 1980 S 20,
1980 S 23, 1980 S 26 or 1980 S 27. In addition, 1980 S 3 was measured
at a position 22".7 west of Saturn on Mar. 16.9156.
---------------------------------------------------------
Title: Comets.
Authors: Festou, M. C.; Lamy, P.
1981Rech...12...46F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Halley Optical Probe Experiment
Authors: Levasseur-Regourd, A. C.; Weinberg, J. L.; Giovane, F.;
Schuerman, D. W.; Lamy, P.; Festou, M.; Bertaux, J. L.; Dumont, R.;
Llebaria, A.; Giese, R. H.
1981giot.proc..121L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the electrostatic potential of interplanetary grains -
Influence of the thermionic effect
Authors: Millet, J.; Lafon, J. P. L.; Lamy, P. L.
1980A&A....92....6M Altcode:
The general theory of the floating potential of a cosmic grain (Lafon
et al. 1980) was used to investigate the importance of the thermionic
emission for interplanetary iron and carbon grains in the vicinity of
the sun. This emission prevents the potential of carbon grains from
becoming strongly negative and allows small grains to exist in regions
where they would otherwise be destroyed.
---------------------------------------------------------
Title: On the size distribution and physical properties of
interplanetary dust grains
Authors: Le Sergeant D'Hendecourt, L. B.; Lamy, Ph. L.
1980Icar...43..350L Altcode:
This paper synthesizes information on the size distribution and
physical properties of interplanetary dust grains obtained from
analyses of lunar microcraters performed until 1979. The different
aspects of these analyses (counting methods, simulation, calibrations)
are summarized and a large amount of data is collected and discussed in
order to clarify past contradictions. The number of small microcraters
( D<SUB>c</SUB> < 5 μm) is found to be higher than previously
derived and the ratio P/ D<SUB>c</SUB> (depth to crater diameter) to
depend upon their sizes. All results converge to a two-component dust
population: Population 1 consists principally of large grains ( d >
2 μm) with density typical of silicates while Population 2 consists of
small grains ( d < 2 μm) with higher density typical of iron, with
a minor component of silicates. The conclusion appears to be further
supported by spatial measurements and collection experiments. Fluffy
grains of very low density (0.3 g/cm <SUP>3</SUP>) are probably not
present to a large extent.
---------------------------------------------------------
Title: Satellites of Saturn
Authors: Lamy, P.; Mauron, N.
1980IAUC.3491....3L Altcode:
P. Lamy and N. Mauron, Laboratoire d'Astronomie Spatiale, Marseilles,
send the following precise measurements of 1980 S 10 (cf. IAUC 3463)
with respect to the center and equatorial plane of Saturn: Mar. 15.9528
UT, +57".24 (east), -0".55 (south); 15.9851, +58".93, -0".38; 16.0236,
+60".40, -0".37; 16.0892, +61".45, -0".57; 16.126, +61".65, -0".67. They
also provide the measurements: 1966 S 2, Mar. 15.9851, 22".45 west;
1980 S 3, Mar. 16.126, 19".75 east. They add that orbital analysis
shows that 1980 S 10 (= 1980 S 6: cf. IAUC 3483) leads Saturn IV (Dione)
by 72o.0. 1980 S 13 could not be found on plates taken on Mar. 15.9528
and 16.962 on the assumption that it trails Saturn IV by 57o and was
brighter than magnitude 18.
---------------------------------------------------------
Title: The New Satellite Dione B and Outer Ring of Saturn.
Authors: Lamy, P. L.; Mauron, N.
1980BAAS...12R.728L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Satellites of Saturn
Authors: Lecacheux, J.; Laques, P.; Wierick, G.; Lelievre, G.; Smith,
B. A.; Blume, W. H.; Lamy, P.; Mauron, N.
1980IAUC.3483....1L Altcode:
J. Lecacheux, Observatoire de Meudon, reports the following analyses
and further electronographic observations by P. Laques at Pic du Midi
and by G. Wierick and G. Lelievre at Haute Provence of separations
of satellites (+ = east, - = west) from Saturn's center: 1966 S 2 =
1980 S 1 = 1980 S 2: Mar. 1.0488 UT, +22".16; 17.031, +21".83. Revised
elements from the data on IAUC 3470-3474: greatest eastern elongation
= 1980 Mar. 18.317 UT + light time + 0.0019 (U - 45o.6) + 0.69465
E. The identities with 1979 S 7 and 1979 S 1 are invalid, the orbital
longitude of 1966 S 2 at the time of the closest approach of Pioneer
11 having been L = 121o +/- 3o. [Editorial Note. It now seems probable
that the correct definition of 1966 S 2 is orbit 16 in the paper by
Aksnes and Franklin (1978, Icarus 36, 107); see also Fountain and
Larson (1978, ibid. 36, 92). The designation 1966 S 1 refers to
an orbit with period 0.75 day, and no object with this period is
now believed to exist.] 1980 S 3 = 1980 S 4 = 1980 S 5 = 1980 S 8
(observation on IAUC 3463 only) = 1980 S 11 = 1980 S 15 = 1980 S 16 =
1980 S 17 = 1980 S 19: Mar. 17.009 UT, -21".6; 18.040, +22".3. Elements
(fitting the indicated observations with a standard deviation of 0".5):
greatest eastern elongation = 1980 Mar. 18.645 UT + light time + 0.0019
(U - 45o.6) + 0.6939 E. Other published observations (i.e., 1979 S 7,
1980 S 7, 1980 S 9, 1980 S 18, 1980 S 20, 1980 S 21 and the IAUC 3466
observation attributed to 1980 S 8 [here redesignated 1980 S 23: Ed.] do
not fit any single circular solution. [Editorial Note. The suggestion
that there exists a second satellite essentialy in the orbit of 1966
S 2 and about 180o from it was privately made to the Central Bureau
by B. A. Smith, University of Arizona, early in March. It is quite
possible that 1980 S 3 = 1979 S 1, for which W. H. Blume has given the
time of greatest western elongation (at Saturn) as 1979 Aug. 31.997 +/-
0.004 UT. 1979 S 2 and 1979 S 4 can together presumably be related to
1966 S 2 and 1980 S 3.] 1980 S 6 = 1980 S 10 = 1980 S 12 = 1980 S 14:
Mar. 1.030 UT, +62".4; 1.049, +62".2; 1.099, +61".4; 1.131, +59".9
(refinement to IAUC 3457). [Editorial Note. The suggestion that 1980 S
6 = 1980 S 10 with period 2.75 days was included with the information
provided by P. Lamy and N. Mauron for publication on IAUC 3463. Both
Smith and Lecacheux have suggested that 1980 S 6 is associated with the
triangular libration point leading Saturn IV (Dione). It is possible
that 1980 S 13 is associated with the corresponding trailing point.]
---------------------------------------------------------
Title: Satellites of Saturn
Authors: Harris, A. W.; Gibson, J.; Lecacheux, J.; Fort, B.;
Fauconnier, T.; Dreux, M.; Vapillon, L.; Laques, P.; Auge, A.; Despiau,
R.; Lamy, P.; Mauron, N.
1980IAUC.3463....1H Altcode:
A. W. Harris, Jet Propulsion Laboratory, reports that observations
by J. Gibson and himself with the 2.5-m reflector at Mount
Wilson Observatory suggest that the satellite 1966 S 2 attained
its greatest elongations from Saturn around the following times:
Mar. 13.16 UT (west), 13.51 (east), 14.54 (west), 15.2 (west) and
17.32 (west). Several other condensations, some of them obviously
transient ring knots, were also noted. Three of them, each ~ 1 mag
fainter than 1966 S 2, were somewhat more persistent and showed motion
suggesting that they might be satellites. The designations, inferred
times of greatest elongations and separations of these objects from
Saturn were: 1980 S 7, Mar. 13.29, 23" east; 1980 S 8, Mar. 15.19, 24"
east; 1980 S 9, Mar. 15.27, 25" west (clear of rings). J. Lecacheux,
B. Fort, T. Fauconnier, M. Dreux and L. Vapillon, Meudon Observatory;
and P. Laques, A. Auge and R. Despiau, Pic du Midi Observatory,
communicate the following separations (uncertainty +/- 0".2) of 1966
S 2 east (+) or west (-) of Saturn's center: Feb. 29.022 UT, -20".09;
Mar. 1.0571, +21".76; 1.0575, +21".43; 1.0634, +20".78; 16.9439, +22";
17.9661, -22".20; 18.0401, -24".64; 18.0443, -23".90; 18.0494, -23".33;
18.1052, -17".74; 18.1065, -17".57. The observations were made using
a Lallemand electronographic camera and a CCD camera on the 1.05-m
Pic du Midi reflector. The best exposure (Mar. 18.0401) shows the
starlike object very clearly detached from the A ring, brighter than
Saturn VII (Hyperion) but fainter than Saturn I (Mimas); the inferred
time of greatest western elongation is Mar. 18.017 UT. The following
ephemeris has been deduced from these observations and those by Pascu
and by Smith et al. on IAUC 3454, 3456 and 3457: greatest eastern
elongation = 1980 Mar. 18.316 UT + light time + 0.0019 (U - 45o.6)
+ 0.69468 E. [Editorial Note. This formula is also in good agreement
with the above observations by Harris and Gibson. On the other hand,
it indicates a greatest eastern elongation on 1979 Dec. 9.3 UT,
rather than Dec. 9.5 UT; cf. the observation by Mulholland on IAUC
3430.] P. Lamy and N. Mauron, Laboratoire d'Astronomie Spatiale,
Marseilles, report that observations with the Chiran 1-m telescope
at the Haute Provence Observatory showed 1966 S 2 to be 24" west
of Saturn's center on Mar. 15.983 UT. A faint nebulosity (mag ~ 16),
possibly another satellite, was detected on several plates; this object,
designated 1980 S 10, attained a maximum elongation of 61".4 west of
Saturn's center on Mar. 16.024 UT (cf. 1980 S 6, IAUC 3457).
---------------------------------------------------------
Title: Collisions among Interplanetary Dust Grains
Authors: Le Sergeant, L. B.; Lamy, P. L.
1980IAUS...90..289L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Two-Dimensional Photographic Photometry of the Zodiacal Light
from Spatial Observations
Authors: Lamy, P. L.; Llebaria, A.; Koutchmy, S.
1980IAUS...90...37L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The electrostatic potential of interplanetary grains
Authors: Lafon, J. P. J.; Lamy, P. L.; Millet, J. M.
1980IAUS...90..303L Altcode:
The plasma sheath and its bulk velocity are included as parameters
for calculating the electrostatic potential of cosmic grains. The most
important effects determining the charge of the grain to be considered
in calculations are photoelectric emission and sticking of solar wind
electrons and ions, except at small heliocentric distances. The results
use parameters for two representative components of the solar wind and
include the influence of bulk velocity which is important through the
positive ions. The role of the solar wind appears clearly in the effect
of its bulk velocity on the potential. The electrostatic potential is
shown to increase slightly with increasing heliocentric distance and
levels off at 1 AU, although thermionic emission will come into play
and increase the potential.
---------------------------------------------------------
Title: Zodiacal light models with a bimodal population
Authors: Lamy, P. L.; Perrin, J. M.
1980IAUS...90...75L Altcode:
The compatibility of the observed properties of interplanetary
dust grains in zodiacal light with a model made of two populations
is investigated. Population 1 consists principally of large grains
(with radius s greater than 2 microns) of density typical of silicates
or chondritic materials in nearly circular orbit while Population 2
consists of small grains (s less than 2 microns) with typically metallic
densities (abt 8 g/cu cm) in hyperbolic orbits. The spatial densities
and volume scattering functions (VSF) of the two populations are
deduced from the observed brightness of the zodiacal light. Though no
clear-cut conclusions are reached, some general trends are detected: (1)
the VSF of the zodiacal light is entirely compatible with the spatial
density of grains obtained from lunar and space measurements. (2)
Under all circumstances, the contribution of Population 2 appears to
be non-negligible. (3) A minimum albedo of 0.5 (probably unrealistic)
is required in order to explain the observed VSF with Population 1 alone
on the basis of the model of Fresnel reflection plus an isotropic term.
---------------------------------------------------------
Title: 2-D observations of IR-stellar speckles.
Authors: Lamy, P.; Koutchmy, S.
1979JOpt...10..331L Altcode: 1979JOp....10..331L
The first observations of speckle images of Alpha Orionis as obtained
at the Cassegrain focus of the 193-cm Telescope of the Haute Provence
Observatory using an IR-TV camera are discussed. The specific nature
of the 2-micron images is outlined.
---------------------------------------------------------
Title: Radiation forces on small particles in the solar system
Authors: Burns, J. A.; Lamy, P. L.; Soter, S.
1979Icar...40....1B Altcode:
We present a new and more accurate expression for the radiation pressure
and Poynting-Robertson drag forces; it is more complete than previous
ones, which considered only perfectly absorbing particles or artificial
scattering laws. Using a simple heuristic derivation, the equation of
motion for a particle of mass m and geometrical cross section A, moving
with velocity v through a radiation field of energy flux density S, is
found to be (to terms of order v/c) m v˙ = ( SA/c)Q <SUB>pr</SUB>[(1
- ṙ/c) Ŝ - v/c] , where Ŝ is a unit vector in the direction of
the incident radiation, ṙ is the particle's radial velocity, and
c is the speed of light; the radiation pressure efficiency factor
Q<SUB>pr</SUB> ≡ Q<SUB>abs</SUB> + Q<SUB>sca</SUB>(1 - <cos
α>), where Q<SUB>abs</SUB> and Q<SUB>sca</SUB> are the efficiency
factors for absorption and scattering, and <cos α> accounts for
the asymmetry of the scattered radiation. This result is confirmed by a
new formal derivation applying special relativistic transformations for
the incoming and outgoing energy and momentum as seen in the particle
and solar frames of reference. Q<SUB>pr</SUB> is evaluated from Mie
theory for small spherical particles with measured optical properties,
irradiated by the actual solar spectrum. Of the eight materials studied,
only for iron, magnetite , and graphite grains does the radiation
pressure force exceed gravity and then just for sizes around 0.1 μm;
very small particles are not easily blown out of the solar system
nor are they rapidly dragged into the Sun by the Poynting-Robertson
effect. The solar wind counterpart of the Poynting-Robertson drag may
be effective, however, for these particles. The orbital consequences
of these radiation forces-including ejection from the solar system
by relatively small radiation pressures-and of the Poynting-Robertson
drag are considered both for heliocentric and planetocentric orbiting
particles. We discuss the coupling between the dynamics of particles
and their sizes (which diminish due to sputtering and sublimation). A
qualitative derivation is given for the differential Doppler effect,
which occurs because the light received by an orbiting particle is
slightly red-shifted by the solar rotation velocity when coming from
the eastern hemisphere of the Sun but blue-shifted when from the western
hemisphere; the ratio of this force to the Poynting-Robertson force is
( R <SUB>⊙</SUB>/r) <SUP>2</SUP>[( w <SUB>⊙</SUB>/n) - 1] , where
R<SUB>⊙</SUB> and w<SUB>⊙</SUB> are the solar radius and spin rate,
and n is the particle's mean motion. The Yarkovsky effect, caused by
the asymmetry in the reradiated thermal emission of a rotating body, is
also developed relying on new physical arguments. Throughout the paper,
representative calculations use the physical and orbital properties
of interplanetary dust, as known from various recent measurements.
---------------------------------------------------------
Title: Astronomical applications of infrared television imaging.
Authors: Lamy, P. L.; Nguyen-Trong, T.; Adjabschirzadeh, A.;
Koutchmy, S.
1979A&A....77..257L Altcode:
Infrared imaging between 1 and 2.4 microns was realized with a
television camera operated at the conventional video rate. A M2 star
of visual magnitude 5.6 was detected at 1.2 and 1.6 microns. Alpha
Ori was further observed at 2 microns and the corresponding smearing
function was found to improve with increasing wavelength. The image
structure (speckle) of Alpha Ori was visualized in the infrared and is
briefly characterized as compared to the visible. Solar observations
at 1.6 microns included direct imagery of sunspots and simultaneous
spectrography of the photosphere and sunspot umbra. The Zeeman splitting
of the 1.5648 microns Fe I line was observed and measurements are
shown to be possible on processed CRT pictures.
---------------------------------------------------------
Title: Comet West 1975n. I. Observations near and after perihelion
passage.
Authors: Koutchmy, S.; Coupiac, P.; Elmore, D.; Lamy, P.; Sevre, F.
1979A&A....72...45K Altcode:
Photographic observations of Comet West 1975n from a high altitude site
are reported. A small value of the absolute magnitude of the Comet 1.5
d after perihelion passage is deduced. Morphological characteristics
of the strongly structured dust tail are obtained, using a statistical
analysis based on the optical data processing of a transparency. The
deduced two-dimensional power spectrum is considered. The temporal
behavior of the main features of the tail is discussed using several
selected pictures.
---------------------------------------------------------
Title: Comet West 1975n part II: study of the striated tail.
Authors: Lamy, P. L.; Koutchmy, S.
1979A&A....72...50L Altcode:
The dynamical evolution of the striae in the tails of comet West
1975n is investigated. A synchrone-syndyne analysis of the overall
tail structure is attempted, but it is found that the classical
synchrone-syndyne description does not apply to the dynamical evolution
of the striae. A subsequent examination of the main properties of
the stria structure strongly suggests that all striae within a given
tail appear to originate from a synchronic edge. A scenario for
the formation of striae is proposed, according to which the bulk of
the dust constituting a tail is released at or around perihelion and
subsequently swept out under the influence of some unknown interaction
that organizes the dust into narrow streaks, or striae. It is concluded
that the unknown interaction involves the solar wind and a convected
magnetic field.
---------------------------------------------------------
Title: Cometary Dust - Importance of Large-Scale and In-Situ
Observations
Authors: Lamy, P. L.
1979comi.work..131L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interplanetary dust: are there two independent populations?
Authors: Le Sergeant, L. B.; Lamy, P. L.
1978Natur.276..800L Altcode:
A RE-EXAMINATION of the information on the size distribution and
physical properties of interplanetary dust grains as inferred from
space measurements, particularly lunar microcraters, leads to the
novel interpretation outlined here in terms of two independent
populations. This hypothesis still suffers from uncertainties in
existing data but should stimulate new experimental and theoretical
work.
---------------------------------------------------------
Title: Photon Counting and Analog Television Systems with Digital
Real Time Image Processing and Display
Authors: Cenalmor, V.; Lamy, Ph. L.; Perrin, J. M.; Nguyen-Trong, T.
1978A&A....69..411C Altcode:
Summary. For a photon counting television system (PCTS) and an analog
television system (ATS), we developed a common acquisition, real-time
processing and visualisation unit which is basically composed of a
random access memory of 64 kilowords of 16 bits, a microprocessor, a
television color display and a floppy disk recorder. Image processing is
performed either by the microprocessor or by a minicomputer connected
to the system. Preliminary results obtained at the telescope are
reported. Key words: television photon counting image processing
---------------------------------------------------------
Title: Photometrical analysis of the June 30, 1973 solar corona.
Authors: Koutchmy, S.; Stellmacher, G.; Koutchmy, O.; Dzubenko, N. I.;
Ivanchuk, V. I.; Popov, O. S.; Rubo, G. A.; Vsekhsviatskii, S. K.;
Lamy, P.
1978A&A....69...35K Altcode:
In order to deduce reliable values of the K and F coronal, a method
of photographic photometry has been applied to study compensated
high-resolution pictures obtained during the June 30, 1973, solar
total eclipse, including a color one. The correctly exposed images of
calibration stars are used to obtain intensities in units of the mean
brightness of the sun. An account is made, in both the blue and the
red spectral ranges, for the sky background as well as for the coronal
aureola effects. The N-polar and E-equatorial regions are shown to be
relatively homogeneous; their intensities are especially studied in
the radial direction and compared with published values of the K and F
coronae. No flattening and no color effect are found in the inner part
(distance less than 2.5 solar radii) of the F corona.
---------------------------------------------------------
Title: Propagating inhomogeneities in the dust tail of comet West 1975
Authors: Koutchmy, S.; Lamy, P.
1978Natur.273..522K Altcode:
COMET West has displayed some remarkable
properties. Sekanina<SUP>1</SUP> has studied the multiple splitting
of its nucleus and also discussed the strange structure of its
dust tail. This tail is characterised by a system of bright bands
which do not correspond to the true synchronous band<SUP>2</SUP> and
which are shown by very few comets. We call these striae (striated
tail) and to study them we have examined numerous original and
duplicate pictures, and selected four observations (Table 1) which
reveal that the morphology was relatively well conserved during the
evolution of the dust tail over a period of more than 4 days. We have
identified three striae (Fig. 1) which seem to propagate in space
while retaining their basic form. This phenomenon is not unusual in
plasmas, such as gas tails of comets<SUP>3</SUP> or streamers in the
solar K-corona<SUP>4,5</SUP>. However, this is apparently the first
time that it has been observed in dust `clouds'. These striae, which we
describe here, are made of dust grains which can be readily demonstrated
by the wide-field colour photographs made by comet observers: the gas
tail (type I) appears distinctly blue because of CN emission and is
directly in the anti-solar direction as well as being well separated
from the large dust tail (type II) which has a neutral colour.
---------------------------------------------------------
Title: Optical properties of silicates in the far ultraviolet
Authors: Lamy, P. L.
1978Icar...34...68L Altcode:
Near-normal incidence reflectance measurements in the interval 1026-1640
Å were performed on four silicates already studied in the visible and
infrared by Pollack et al. (1973). We use a Kramers-Kronig analysis
of these data to calculate the complex index of refraction m = n -
ik. New transmission measurements improve the determination of k in
the interval 2500-4500 Å, except for andesite, which is more opaque
than found by Pollack et al.
---------------------------------------------------------
Title: Workshop on cometary missions. ESOC Darmstadt, 17 - 19
April 1978. Chairmen's summaries and extended abstracts of invited
contributions.
Authors: Arpigny, C.; Bertaux, J. L.; Bodechtel, J.; Dalmann, B. -K.;
Fechtig, H.; Festou, M.; Giese, R. H.; Grün, E.; Haser, L.; Hughes,
D. W.; Ip, W. -H.; Jockers, K.; Keller, H. U.; Keppler, E.; Kissel,
J.; Koutchmy, S.; Krankowsky, D.; Lämmerzahl, P.; Lamy, P. L.;
Levasseur-Regourd, A. -C.; Lukoshhus, D.; Malaise, D.; Mariani, F.;
Michel, K. W.; Neukum, G.; Orfei, R.; Rosenbauer, H.; Röser, S.;
Schlude, F.; Schmidt, H. U.; Schubart, J.; Schwehm, G. H.; Sieber,
A.; Wänke, H.; Wallis, M. K.; Zerull, R. H.
1978wocm.book.....A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Radiation pressure and Poynting-Robertson drag for small
spherical particles.
Authors: Soter, S.; Burns, J. A.; Lamy, P. L.
1977cami.coll..121S Altcode: 1977IAUCo..39..121S
Robertson's expression for the velocity-dependent effect of solar
radiation on the motion of small particles is difficult because of its
dependence on relativistic considerations, and it is also deficient in
that it assumes perfectly absorbing particles. The present paper gives
a heuristic derivation of the Poynting-Robertson effect. Robertson's
expression for perfectly absorbing particles is obtained but on a
much simpler physical basis, and an expression is also obtained for a
particle that in general scatters, transmits, and absorbs light. Some
numerical results on the solar radiation forces felt by small particles
of cosmochemically important compositions are given.
---------------------------------------------------------
Title: Traitement des Images TÉLÉVISION - Application à une
CAMéRA Infra Rouge
Authors: Lamy, P. L.; Nguyen-Trong, T.; Perrin, J. M.
1977aaid.coll...17L Altcode: 1977IAUCo..40...17L
No abstract at ADS
---------------------------------------------------------
Title: A Corrected Derivation of the Poynting-Robertson Effect
Authors: Burns, J. A.; Soter, S.; Lamy, P. L.
1976BAAS....8..434B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Poynting-Robertson effect for small spherical particles.
Authors: Burns, J. A.; Soter, S.; Lamy, P. L.
1976BAAS....8..471B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Study of the Anti-Tail of Comet Kohoutek from an Observation
on 17 January 1974
Authors: Lamy, Ph. L.; Koutchmy, S.
1976LNP....48..343L Altcode: 1976IAUCo..31..343L
As part of our program of observation of Comet Kohoutek at Pic-du-Midi
observatory, we obtained, on January 17.8 UT, 1974 a photograph in
polarized light showing dramatically the (dust) antitail extending
for almost 1° from the Comet's head (reported in Sky and Telescope,
June 1974); indeed the comet is visible in polarized light further
away than in total light as noticed by Weinberg and Beeson (IAU
Colloquium No. 25, 1974) for Comet Ikeya-Seki. A photometric
and polarimetric study was performed (Bücher, A., Robley, R.,
and Koutchmy, S., 1975, Astron. Astrophys. 39, 289) showing that
the anti-tail is strongly polarized (up to 50 %). These large
degrees of polarization are of the same order of magnitude as those
reported for the tail of Comet Ikeya-Seki by Matjagin Sabitov and
Kharitonov (1967, Astron. Zh. 44, 1075) and by Weinberg and Beeson
(op. cit.). As discussed by these latter authors, particle alignment
is precluded as a significant contributor to polarization in the tail
of comets. Polarization by large spheres as obtained from the Fresnel
reflection coefficients applies only in the case of perfect surface,
a circumstance very unlikely in interplanetary space; the scattering
is in fact controlled by the surface microstructures (Van de Hulst,
private communication). Therefore we hypothesized that submicronic
grains should play an important role in the anti-tail. The classical
method of Finson and Probstein (1968, Astrophys. J. 154, 327, 353)
was used to draw the sky plane view of the syndynes for the day of
observation. Since the ratio β of the radiation pressure force to
the gravitational attraction is proportional to the third power of
the grains' radius s for ≲z 0.1 μ, submicronic grains with typical
radii of 0.02 μ may indeed be present in the anti-tail and provide a
straight-forward explanation of the observed polarization. This size
is of the same order of magnitude as that inferred for interstellar
grains which may well be embedded in the comet's nucleus as well as
meteorites for which there exists good evidence. Our conclusion does
not rule out the presence of millimeter-size grains as proposed by
Sekanina and Gary and O'Dell in their preliminary investigations (1974,
Icarus 23, 502, 519) which did not take into account the polarimetric
result; such grains may well coexist with the submicronic ones. Finally,
the line of maximum intensity is close to a synchrone corresponding to
a time of emission 100 days before perihelion passage. This supports
the synchronic formation of anomalous tails and possibly of tails as
proposed by Vsekhsvyatsky (1932, Astron. Zh. 9, 166).
---------------------------------------------------------
Title: Temperature Distribution and Lifetime of Interplanetary
Ice Grains
Authors: Lamy, P.; Jousselme, M. F.
1976LNP....48..443L Altcode: 1976IAUCo..31..443L
An improved solution for the temperature distribution of interplanetary
ice grains is presented using the refractive index measured at 100
K. The efficiency factors for absorption are obtained from Mie theory,
and the calculation is carried out for micron- and submicron-size
grains at 50, 100 and 150 K. Corresponding lifetimes are given.
---------------------------------------------------------
Title: Orbital Evolution of Circum-Solar Dust Grains
Authors: Lamy, P.
1976LNP....48..437L Altcode: 1976IAUCo..31..437L
The orbital evolution of circumsolar dust grains is obtained by
numerical integration of the equations of motion which includes
the grains' interactions with the solar radiation field and the
solar wind. A previous solution is improved by avoiding a classical
approximation for the Poynting-Robertson term, leading to an important
revision of the orbital behavior. Results are presented for obsidian
grains whose inward spiraling is stopped by the effect of sublimation.
---------------------------------------------------------
Title: Study of the Inner Satellites of Saturn by Photographic
Photometry
Authors: Koutchmy, S.; Lamy, P. L.
1975Icar...25..459K Altcode:
Good photographs of Saturn and its five inner satellites were obtained
on January 2, 1974 with the 105 cm telescope at Pic du Midi Observatory
with exposure times of 45 sec. The spread function is constant over the
field, and isotropic. The true photometric profiles of the satellites
are obtained after deriving a model for the stray light coming from the
rings. The magnitudes, computed by integration, are in good agreement
with published values except for Mimas, which is nearly one magnitude
fainter then previously believed.
---------------------------------------------------------
Title: On the dynamics of interplanetary dust grains
Authors: Lamy, Philippe Louis
1975PhDT.......173L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Dynamics of Interplanetary Dust Grains.
Authors: Lamy, P. L.
1975PhDT.........6L Altcode:
The interaction of spherical grains of various materials whose radii lie
in the micronic and submicronic range with the interplanetary medium
is solved. This includes: (1) interaction with the solar radiation
field which is solved using Mie scattering theory and taking into
account the precise dependence of optical properties upon wavelength;
(2) interaction with solar wind considering corpuscular tangential
drag; and (3) interaction with the interplanetary magnetic field in
terms of a diffusion or random walk through a series of electromagnetic
scatterings. Numerical results for these interactions span in the entire
solar system with elliptical orbits of grains of various materials and
sizes and provide a clear global picture of dust grain interactions
that includes grain dynamic considerations.
---------------------------------------------------------
Title: Interaction of interplanetary dust grains with the solar
radiation field.
Authors: Lamy, P. L.
1974A&A....35..197L Altcode:
The interaction of interplanetary dust grains with the solar radiation
field is investigated for micronic and submicronic spheres of quartz,
obsidian, andesite, ice, and iron. The dependence of the complex
indices of refraction on wavelength was taken into account using Mie
theory to obtain the efficiency factors for absorption and radiation
pressure. The temperature distributions differ markedly from past
results, and show that silicate grains can come very close to the sun,
thus justifying the existence of a dusty component of the solar corona
up to approximately 2 solar radii. Improved vapor pressure formulas
yield increased lifetimes for interplanetary grains. It is shown that
the onset of rapid destruction by sublimation is extremely sudden and
has a well-defined location which depends upon the absorption character
of the grains' material. The radiation pressure force never exceeds
the gravitational force for silicates and ice.
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Title: The Dynamics of Circum-solar Dust Grains
Authors: Lamy, Ph. L.
1974A&A....33..191L Altcode:
Summary. The inward spiraling of interplanetary dust grains under
the Poynting-Robertson and corpuscular pressure drags is shown to be
either counterbalanced or reduced by the effect of the net increase
of the radiation pressure force caused by the decrease of the grains'
radii when sublimating. Precise trajectories, obtained for the first
time, show that silicate grains remain in the vicinity of the Sun
where they describe an impressive number of orbits. Dynamical dust4ree
zones are clearly established and the location of regions of probable
concentration are predicted; infrared emission spectra show remarkable
features which can serve as signatures for the nature of the dust. It is
also concluded that grains whose radii are less than about 0.2 m play
a negligible r6le in the F-corona. Key words: interplanetary dust -
F-corona - circumstellar envelopes - infrared spectrum
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Title: Infrared Photometry of the Outer Corona.
Authors: Lamy, Ph. L.; Koutchmy, S.
1974BAAS....6..311L Altcode:
No abstract at ADS