Author name code: woeger
ADS astronomy entries on 2022-09-14
author:"Woeger, Friedrich"
------------------------------------------------------------------------
Title: Ground-based instrumentation and observational techniques
Authors: Rimmele, Thomas; Kuhn, Jeff; Woeger, Friedrich; Tritschler,
. Alexandra; Lin, Haosheng; Casini, Roberto; Schad, Thomas; Jaeggli,
Sarah; de Wijn, Alfred; Fehlmann, Andre; Anan, Tetsu; Schmidt, Dirk
Bibcode: 2022cosp...44.2507R
Altcode:
We'll review the current state-of-the-art for ground-based
instrumentation and techniques to achieve high-resolution
observations. We'll use the 4m Daniel K. Inouye Solar Telescope
(DKIST), the European Solar Telescope (EST) and other ground-based
instrumentation as examples to demonstrate instrument designs
and observing techniques. Using adaptive optics and post-facto
image processing techniques, the recently completed DKIST provides
unprecedented resolution and high polarimetric sensitivity that
enables astronomers to unravel many of the mysteries the Sun presents,
including the origin of solar magnetism, the mechanisms of coronal
heating and drivers of flares and coronal mass ejections. Versatile
ground-based instruments provide highly sensitive measurements of solar
magnetic fields, that in the case of DKIST, also include measurements
of the illusive magnetic field of the faint solar corona. Ground-based
instruments produce large and diverse data sets that require complex
calibration and data processing to provide science-ready to a broad
community. We'll briefly touch on ongoing and future instrumentation
developments, including multi-conjugate adaptive optics.
Title: The Visible Spectro-Polarimeter of the Daniel K. Inouye
Solar Telescope
Authors: de Wijn, A. G.; Casini, R.; Carlile, A.; Lecinski, A. R.;
Sewell, S.; Zmarzly, P.; Eigenbrot, A. D.; Beck, C.; Wöger, F.;
Knölker, M.
Bibcode: 2022SoPh..297...22D
Altcode: 2022arXiv220300117D
The Daniel K. Inouye Solar Telescope (DKIST) Visible Spectro-Polarimeter
(ViSP) is a traditional slit-scanning spectrograph with the ability
to observe solar regions up to a 120 ×78 arcsec2 area. The
design implements dual-beam polarimetry, a polychromatic polarization
modulator, a high-dispersion echelle grating, and three spectral
channels that can be automatically positioned. A defining feature of
the instrument is its capability to tune anywhere within the 380 - 900
nm range of the solar spectrum, allowing for a virtually infinite number
of combinations of three wavelengths to be observed simultaneously. This
enables the ViSP user to pursue well-established spectro-polarimetric
studies of the magnetic structure and plasma dynamics of the solar
atmosphere, as well as completely novel investigations of the solar
spectrum. Within the suite of first-generation instruments at the DKIST,
ViSP is the only wavelength-versatile spectro-polarimeter available to
the scientific community. It was specifically designed as a discovery
instrument to explore new spectroscopic and polarimetric diagnostics
and test improved models of polarized line formation through high
spatial-, spectral-, and temporal-resolution observations of the Sun's
polarized spectrum. In this instrument article, we describe the science
requirements and design drivers of ViSP and present preliminary science
data collected during the commissioning of the instrument.
Title: Polarization modeling and predictions for DKIST, part 9:
flux distribution with FIDO
Authors: Harrington, David M.; Wöger, Friedrich; White, Amanda J.;
Sueoka, Stacey R.
Bibcode: 2021JATIS...7d8005H
Altcode:
Astronomical instruments greatly improve wavelength multiplexing
capabilities by using beam splitters. In the case of the 4-m National
Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) solar
telescope, over 70 W of optical power is distributed simultaneously to
four instruments, each with multiple cameras. Many DKIST observing cases
require simultaneous observations of many narrow bandpasses combined
with an adaptive optics system. The facility uses five dichroic optical
stations to allow at least 11 cameras and two wavefront sensors to
simultaneously observe ultraviolet to infrared wavelengths with flexible
reconfiguration. The DKIST dichroics required substantial development to
achieve very tight specifications over very large apertures of 290 mm
diameter. Coating spectral variation occurs over <1 nm wavelength,
comparable with instrument bandpasses. We measure retardance spectral
variation of up to a full wave and diattenuation varying over ±10 %
per nm. Spatial variation of Mueller matrix elements for coatings
in both transmission and reflection requires careful metrology. We
demonstrate coatings from multiple vendors exhibit this behavior. We
show achievement of 5-nm root mean square (RMS) reflected wavefront and
24-nm RMS power with coatings over 8 μm thick. We show mild impacts
of depolarization and spectral variation of polarization on modulation
efficiency caused by the dichroic coatings. We show an end-to-end
system polarization model for the visible spectropolarimeter instrument,
including the dichroics, grating, analyzer, and all coated optics. We
show detailed performance for all DKIST dichroics for community use
in planning future observations.
Title: The Daniel K. Inouye Solar Telescope (DKIST)/Visible Broadband
Imager (VBI)
Authors: Wöger, Friedrich; Rimmele, Thomas; Ferayorni, Andrew; Beard,
Andrew; Gregory, Brian S.; Sekulic, Predrag; Hegwer, Steven L.
Bibcode: 2021SoPh..296..145W
Altcode:
The Daniel K. Inouye Solar Telescope (DKIST) is a ground-based
observatory for observations of the solar atmosphere featuring an
unprecedented entrance aperture of four meters. To address its demanding
scientific goals, DKIST features innovative and state-of-the-art
instrument subsystems that are fully integrated with the facility
and designed to be capable of operating mostly simultaneously. An
important component of DKIST's first-light instrument suite is the
Visible Broadband Imager (VBI). The VBI is an imaging instrument that
aims to acquire images of the solar photosphere and chromosphere with
high spatial resolution and high temporal cadence to investigate
the to-date smallest detectable features and their dynamics in the
solar atmosphere. VBI observations of unprecedented spatial resolution
ultimately will be able to inform modern numerical models and thereby
allow new insights into the physics of the plasma motion at the smallest
scales measurable by DKIST. The VBI was designed to deliver images
at various wavelengths and at the diffraction limit of DKIST. The
diffraction limit is achieved by using adaptive optics in conjunction
with post-facto image-reconstruction techniques to remove residual
effects of the terrestrial atmosphere. The first images of the VBI
demonstrate that DKIST's optical system enables diffraction-limited
imaging across a large field of view of various layers in the solar
atmosphere. These images allow a first glimpse at the exciting
scientific discoveries that will be possible with DKIST's VBI.
Title: Solar Adaptive Optics
Authors: Rimmele, T.; Marino, J.; Schmidt, D.; Wöger, F.
Bibcode: 2021hai2.book..345R
Altcode:
No abstract at ADS
Title: The National Science Foundation's Daniel K. Inouye Solar
Telescope — Status Update
Authors: Rimmele, T.; Woeger, F.; Tritschler, A.; Casini, R.; de Wijn,
A.; Fehlmann, A.; Harrington, D.; Jaeggli, S.; Anan, T.; Beck, C.;
Cauzzi, G.; Schad, T.; Criscuoli, S.; Davey, A.; Lin, H.; Kuhn, J.;
Rast, M.; Goode, P.; Knoelker, M.; Rosner, R.; von der Luehe, O.;
Mathioudakis, M.; Dkist Team
Bibcode: 2021AAS...23810601R
Altcode:
The National Science Foundation's 4m Daniel K. Inouye Solar Telescope
(DKIST) on Haleakala, Maui is now the largest solar telescope in the
world. DKIST's superb resolution and polarimetric sensitivity will
enable astronomers to unravel many of the mysteries the Sun presents,
including the origin of solar magnetism, the mechanisms of coronal
heating and drivers of flares and coronal mass ejections. Five
instruments, four of which provide highly sensitive measurements
of solar magnetic fields, including the illusive magnetic field of
the faint solar corona. The DKIST instruments will produce large and
complex data sets, which will be distributed through the NSO/DKIST Data
Center. DKIST has achieved first engineering solar light in December
of 2019. Due to COVID the start of the operations commissioning phase
is delayed and is now expected for fall of 2021. We present a status
update for the construction effort and progress with the operations
commissioning phase.
Title: DKIST First-light Instrumentation
Authors: Woeger, F.; Rimmele, T.; Casini, R.; von der Luehe, O.; Lin,
H.; Kuhn, J.; Dkist Team
Bibcode: 2021AAS...23810602W
Altcode:
The NSF's Daniel K. Inouye Solar Telescope's (DKIST) four meter aperture
and state-of-the-art wavefront correction system and instrumentation
will facilitate new insights into the complexities of the solar
atmosphere. We will describe the details and status of the diverse
first light instruments, including the high order adaptive optics
system, that are being commissioned: The Visible Spectro-Polarimeter
(ViSP), the Visible Broadband Imager (VBI), the Visible Tunable Filter
(VTF), the Diffraction-Limited Spectro-Polarimeter (DL-NIRSP) and the
Cryogenic Spectro-Polarimeter (Cryo-NIRSP). We will present first data
demonstrating the telescope's instrument systems performance.
Title: First light with adaptive optics: the performance of the
DKIST high-order adaptive optics
Authors: Johnson, Luke C.; Johansson, Erik; Marino, Jose; Richards,
Kit; Rimmele, Thomas; Wang, Iris; Wöger, Friedrich
Bibcode: 2020SPIE11448E..0TJ
Altcode:
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) achieved first light in late 2019. The DKIST's design includes
a wavefront correction system, which incorporates Adaptive Optics (AO)
in order to feed a diffraction-limited beam to five of its first-light
science instruments. The first-light DKIST AO is a single-conjugate
system designed to achieve 0.3 Strehl at 500 nm observing wavelength
in our expected median seeing of r0 = 7 cm. The system incorporates a
1600-actuator Deformable Mirror (DM), a fast tip-tilt (FTT) corrector,
a low-latency hybrid Field Programmable Gate Array (FPGA) / Central
Processing Unit (CPU) real-time controller, and a correlating
Shack-Hartmann wavefront sensor with 1457 active subapertures. We
present results from the first light campaign of the DKIST, focusing
on AO system performance. We compare the on-sky AO performance to
the performance predicted through error-budget analysis and discuss
implications for ongoing operation of DKIST and the upgrade path to
DKIST multi-conjugate AO.
Title: The Daniel K. Inouye Solar Telescope - Observatory Overview
Authors: Rimmele, Thomas R.; Warner, Mark; Keil, Stephen L.; Goode,
Philip R.; Knölker, Michael; Kuhn, Jeffrey R.; Rosner, Robert R.;
McMullin, Joseph P.; Casini, Roberto; Lin, Haosheng; Wöger, Friedrich;
von der Lühe, Oskar; Tritschler, Alexandra; Davey, Alisdair; de Wijn,
Alfred; Elmore, David F.; Fehlmann, André; Harrington, David M.;
Jaeggli, Sarah A.; Rast, Mark P.; Schad, Thomas A.; Schmidt, Wolfgang;
Mathioudakis, Mihalis; Mickey, Donald L.; Anan, Tetsu; Beck, Christian;
Marshall, Heather K.; Jeffers, Paul F.; Oschmann, Jacobus M.; Beard,
Andrew; Berst, David C.; Cowan, Bruce A.; Craig, Simon C.; Cross,
Eric; Cummings, Bryan K.; Donnelly, Colleen; de Vanssay, Jean-Benoit;
Eigenbrot, Arthur D.; Ferayorni, Andrew; Foster, Christopher; Galapon,
Chriselle Ann; Gedrites, Christopher; Gonzales, Kerry; Goodrich, Bret
D.; Gregory, Brian S.; Guzman, Stephanie S.; Guzzo, Stephen; Hegwer,
Steve; Hubbard, Robert P.; Hubbard, John R.; Johansson, Erik M.;
Johnson, Luke C.; Liang, Chen; Liang, Mary; McQuillen, Isaac; Mayer,
Christopher; Newman, Karl; Onodera, Brialyn; Phelps, LeEllen; Puentes,
Myles M.; Richards, Christopher; Rimmele, Lukas M.; Sekulic, Predrag;
Shimko, Stephan R.; Simison, Brett E.; Smith, Brett; Starman, Erik;
Sueoka, Stacey R.; Summers, Richard T.; Szabo, Aimee; Szabo, Louis;
Wampler, Stephen B.; Williams, Timothy R.; White, Charles
Bibcode: 2020SoPh..295..172R
Altcode:
We present an overview of the National Science Foundation's Daniel
K. Inouye Solar Telescope (DKIST), its instruments, and support
facilities. The 4 m aperture DKIST provides the highest-resolution
observations of the Sun ever achieved. The large aperture of
DKIST combined with state-of-the-art instrumentation provide the
sensitivity to measure the vector magnetic field in the chromosphere
and in the faint corona, i.e. for the first time with DKIST we will
be able to measure and study the most important free-energy source
in the outer solar atmosphere - the coronal magnetic field. Over its
operational lifetime DKIST will advance our knowledge of fundamental
astronomical processes, including highly dynamic solar eruptions
that are at the source of space-weather events that impact our
technological society. Design and construction of DKIST took over two
decades. DKIST implements a fast (f/2), off-axis Gregorian optical
design. The maximum available field-of-view is 5 arcmin. A complex
thermal-control system was implemented in order to remove at prime
focus the majority of the 13 kW collected by the primary mirror and
to keep optical surfaces and structures at ambient temperature, thus
avoiding self-induced local seeing. A high-order adaptive-optics
system with 1600 actuators corrects atmospheric seeing enabling
diffraction limited imaging and spectroscopy. Five instruments, four
of which are polarimeters, provide powerful diagnostic capability
over a broad wavelength range covering the visible, near-infrared,
and mid-infrared spectrum. New polarization-calibration strategies
were developed to achieve the stringent polarization accuracy
requirement of 5×10−4. Instruments can be combined and
operated simultaneously in order to obtain a maximum of observational
information. Observing time on DKIST is allocated through an open,
merit-based proposal process. DKIST will be operated primarily in
"service mode" and is expected to on average produce 3 PB of raw
data per year. A newly developed data center located at the NSO
Headquarters in Boulder will initially serve fully calibrated data to
the international users community. Higher-level data products, such as
physical parameters obtained from inversions of spectro-polarimetric
data will be added as resources allow.
Title: Real-time speckle image processing with the DKIST
Authors: Beard, Andrew; Wöger, Friedrich; Ferayorni, Andrew
Bibcode: 2020SPIE11452E..1XB
Altcode:
We present an overview of the design and implementation of the real-time
speckle image processing pipeline for the National Science Foundation's
(NSF) Daniel K. Inouye Solar Telescope (DKIST) Visible Broadband Imager
(VBI) first light instrument. We begin by discussing our real-time
constraints, changes to our design over the course of development
and the current design and status of the project. We then present a
more detailed overview of the C++ pipeline implementation including
major components, functionality and usage. Finally, we present a
performance summary and a reconstruction obtained from DKIST first
light initiative data.
Title: Construction update of the Daniel K. Inouye Solar Telescope
project
Authors: Warner, Mark; Rimmele, Thomas R.; Martinez Pillet, Valentin;
Casini, Roberto; Berukoff, Steve; Craig, Simon C.; Ferayorni, Andrew;
Goodrich, Bret D.; Hubbard, Robert P.; Harrington, David; Jeffers,
Paul; Johansson, Erik M.; Kneale, Ruth; Kuhn, Jeff; Liang, Chen; Lin,
Haosheng; Marshall, Heather; Mathioudakis, Mihalis; McBride, William
R.; McMullin, Joseph; McVeigh, William; Sekulic, Predrag; Schmidt,
Wolfgang; Shimko, Steve; Sueoka, Stacey; Summers, Rich; Tritschler,
Alexandra; Williams, Timothy R.; Wöger, Friedrich
Bibcode: 2018SPIE10700E..0VW
Altcode:
Construction of the Daniel K. Inouye Solar Telescope (DKIST) is
well underway on the Haleakalā summit on the Hawaiian island of
Maui. Featuring a 4-m aperture and an off-axis Gregorian configuration,
the DKIST will be the world's largest solar telescope. It is designed
to make high-precision measurements of fundamental astrophysical
processes and produce large amounts of spectropolarimetric and
imaging data. These data will support research on solar magnetism
and its influence on solar wind, flares, coronal mass ejections,
and solar irradiance variability. Because of its large aperture, the
DKIST will be able to sense the corona's magnetic field—a goal that
has previously eluded scientists—enabling observations that will
provide answers about the heating of stellar coronae and the origins
of space weather and exo-weather. The telescope will cover a broad
wavelength range (0.35 to 28 microns) and operate as a coronagraph
at infrared (IR) wavelengths. Achieving the diffraction limit of
the 4-m aperture, even at visible wavelengths, is paramount to these
science goals. The DKIST's state-of-the-art adaptive optics systems
will provide diffraction-limited imaging, resolving features that are
approximately 20 km in size on the Sun. At the start of operations,
five instruments will be deployed: a visible broadband imager (VTF),
a visible spectropolarimeter (ViSP), a visible tunable filter (VTF),
a diffraction-limited near-IR spectropolarimeter (DLNIRSP), and a
cryogenic near-IR spectropolarimeter (cryo-NIRSP). At the end of
2017, the project finished its fifth year of construction and eighth
year overall. Major milestones included delivery of the commissioning
blank, the completed primary mirror (M1), and its cell. Commissioning
and testing of the coudé rotator is complete and the installation
of the coudé cleanroom is underway; likewise, commissioning of the
telescope mount assembly (TMA) has also begun. Various other systems and
equipment are also being installed and tested. Finally, the observatory
integration, testing, and commissioning (IT&C) activities have
begun, including the first coating of the M1 commissioning blank and
its integration within its cell assembly. Science mirror coating and
initial on-sky activities are both anticipated in 2018.
Title: Laboratory integration of the DKIST wavefront correction system
Authors: Johnson, Luke C.; Cummings, Keith; Drobilek, Mark; Johansson,
Erik; Marino, Jose; Rampy, Rachel; Richards, Kit; Rimmele, Thomas;
Sekulic, Predrag; Wöger, Friedrich
Bibcode: 2018SPIE10703E..0FJ
Altcode:
The Wavefront Correction (WFC) system for the Daniel K. Inouye Solar
Telescope (DKIST) is in its final stages of laboratory integration. All
optical, mechanical, and software components have been unit tested and
installed and aligned in our laboratory testbed in Boulder, CO. We
will verify all aspects of WFC system performance in the laboratory
before disassembling and shipping it to Maui for final integration
with the DKIST in early 2019. The DKIST Adaptive Optics (AO) system
contains a 1600-actuator deformable mirror, a correlating Shack-
Hartmann wavefront sensor, a fast tip-tilt mirror, and an FPGA-based
control system. Running at a nominal rate of 1975 Hz, the AO system
will deliver diffraction-limited images to five of the DKIST science
instruments simultaneously. The DKIST AO system is designed to achieve
the diffraction limit (on-axis Strehl > 0.3) at wavelengths up to
500 nm in median daytime seeing (r0 = 7 cm). In addition
to AO for diffraction-limited observing, the DKIST WFC system has a
low-order wavefront sensor for sensing quasi-static wavefront errors,
a context viewer for telescope pointing and image quality assessment,
and an active optics engine. The active optics engine uses inputs from
the low-order wavefront sensor and the AO system to actively correct
for telescope misalignment. All routine alignment and calibration
procedures are automated via motorized stages that can be controlled
from Python scripts. We present the current state of the WFC system as
we prepare for final integration with the DKIST, including verification
test design, system performance metrics, and laboratory test data.
Title: The DKIST low order wavefront sensor
Authors: Johansson, Erik; Cummings, Keith; Drobilek, Mark; Johnson,
Luke; Richards, Kit; Rampy, Rachel; Wöger, Friedrich
Bibcode: 2018SPIE10703E..5PJ
Altcode:
The Low Order Wavefront Sensor (LOWFS) is a key component of the
Active Optics System of the Daniel K Inouye Solar Telescope. It is
designed to measure low order wavefront aberrations in the optical beam
arising from gravitational and thermal flexure in the telescope as it
moves through the sky during solar observations. These quasi-static
aberrations are detrimental to the telescope image quality during
seeing-limited observations. The LOWFS measures these quasistatic
perturbations by averaging over the atmospheric turbulence. It sends
its measurements to the Active Optics System, which computes a solution
using the primary (M1) and secondary (M2) mirrors, and sends offsets
to the M1 and M2 mirror control systems. The LOWFS is implemented
using a 1k x 1k pixel Shack-Hartmann wavefront sensor coupled with
a real-time cross correlating image processing engine running at 30
Hz. The real-time engine is implemented in C++ using the Armadillo
linear algebra library, enabling equation-style programming with arrays
and vectors, achieving essentially the same speed as hand coded loops
over the same data structures. The cross correlation is implemented
in the frequency domain leveraging the speed of the FFTW Fast Fourier
Transform library. The entire realtime engine is embedded inside
a DKIST Common Services Framework Controller, allowing for simple
command and control of the wavefront sensor computations using the
high-level Wavefront Correction Control System software. A Python-based
script engine is used to implement various calibration tasks, allowing
full access to the SciPy software stack for non-real-time scientific
computations. This paper describes the design and implementation of the
LOWFS and presents initial results from testing in the DKIST Wavefront
Correction System Laboratory.
Title: Status of the Daniel K. Inouye Solar Telescope: unraveling
the mysteries the Sun.
Authors: Rimmele, Thomas R.; Martinez Pillet, Valentin; Goode, Philip
R.; Knoelker, Michael; Kuhn, Jeffrey Richard; Rosner, Robert; Casini,
Roberto; Lin, Haosheng; von der Luehe, Oskar; Woeger, Friedrich;
Tritschler, Alexandra; Fehlmann, Andre; Jaeggli, Sarah A.; Schmidt,
Wolfgang; De Wijn, Alfred; Rast, Mark; Harrington, David M.; Sueoka,
Stacey R.; Beck, Christian; Schad, Thomas A.; Warner, Mark; McMullin,
Joseph P.; Berukoff, Steven J.; Mathioudakis, Mihalis; DKIST Team
Bibcode: 2018AAS...23231601R
Altcode:
The 4m Daniel K. Inouye Solar Telescope (DKIST) currently under
construction on Haleakala, Maui will be the world’s largest solar
telescope. Designed to meet the needs of critical high resolution and
high sensitivity spectral and polarimetric observations of the sun,
this facility will perform key observations of our nearest star that
matters most to humankind. DKIST’s superb resolution and sensitivity
will enable astronomers to address many of the fundamental problems
in solar and stellar astrophysics, including the origin of stellar
magnetism, the mechanisms of coronal heating and drivers of the
solar wind, flares, coronal mass ejections and variability in solar
and stellar output. DKIST will also address basic research aspects of
Space Weather and help improve predictive capabilities. In combination
with synoptic observations and theoretical modeling DKIST will unravel
the many remaining mysteries of the Sun.The construction of DKIST is
progressing on schedule with 80% of the facility complete. Operations
are scheduled to begin early 2020. DKIST will replace the NSO
facilities on Kitt Peak and Sac Peak with a national facility with
worldwide unique capabilities. The design allows DKIST to operate as
a coronagraph. Taking advantage of its large aperture and infrared
polarimeters DKIST will be capable to routinely measure the currently
illusive coronal magnetic fields. The state-of-the-art adaptive optics
system provides diffraction limited imaging and the ability to resolve
features approximately 20 km on the Sun. Achieving this resolution
is critical for the ability to observe magnetic structures at their
intrinsic, fundamental scales. Five instruments will be available at
the start of operations, four of which will provide highly sensitive
measurements of solar magnetic fields throughout the solar atmosphere
- from the photosphere to the corona. The data from these instruments
will be distributed to the world wide community via the NSO/DKIST data
center located in Boulder. We present examples of science objectives
and provide an overview of the facility and project status, including
the ongoing efforts of the community to develop the critical science
plan for the first 2-3 years of operations.
Title: Influence of speckle image reconstruction on photometric
precision for large solar telescopes
Authors: Peck, C. L.; Wöger, F.; Marino, J.
Bibcode: 2017A&A...607A..83P
Altcode:
Context. High-resolution observations from large solar telescopes
require adaptive optics (AO) systems to overcome image degradation
caused by Earth's turbulent atmosphere. AO corrections are, however,
only partial. Achieving near-diffraction limited resolution over a
large field of view typically requires post-facto image reconstruction
techniques to reconstruct the source image.
Aims: This study
aims to examine the expected photometric precision of amplitude
reconstructed solar images calibrated using models for the on-axis
speckle transfer functions and input parameters derived from AO control
data. We perform a sensitivity analysis of the photometric precision
under variations in the model input parameters for high-resolution
solar images consistent with four-meter class solar telescopes.
Methods: Using simulations of both atmospheric turbulence and
partial compensation by an AO system, we computed the speckle transfer
function under variations in the input parameters. We then convolved
high-resolution numerical simulations of the solar photosphere with the
simulated atmospheric transfer function, and subsequently deconvolved
them with the model speckle transfer function to obtain a reconstructed
image. To compute the resulting photometric precision, we compared the
intensity of the original image with the reconstructed image.
Results: The analysis demonstrates that high photometric precision can
be obtained for speckle amplitude reconstruction using speckle transfer
function models combined with AO-derived input parameters. Additionally,
it shows that the reconstruction is most sensitive to the input
parameter that characterizes the atmospheric distortion, and sub-2%
photometric precision is readily obtained when it is well estimated.
Title: Critical Infrared Science with the Daniel K. Inouye Solar
Telescope
Authors: Schad, Thomas A.; Fehlmann, Andre; Jaeggli, Sarah A.; Kuhn,
Jeffrey Richard; Lin, Haosheng; Penn, Matthew J.; Rimmele, Thomas R.;
Woeger, Friedrich
Bibcode: 2017SPD....4811703S
Altcode:
Critical science planning for early operations of the Daniel K. Inouye
Solar Telescope is underway. With its large aperture, all-reflective
telescope design, and advanced instrumentation, DKIST provides
unprecedented access to the important infrared (IR) solar spectrum
between 1 and 5 microns. Breakthrough IR capabilities in coronal
polarimetry will sense the coronal magnetic field routinely for the
first time. The increased Zeeman resolution near the photospheric
opacity minimum will provide our deepest and most sensitive measurement
of quiet sun and active region magnetic fields to date. High-sensitivity
He I triplet polarimetry will dynamically probe the chromospheric
magnetic field in fibrils, spicules, and filaments, while observations
of molecular CO transitions will characterize the coolest regions
of the solar atmosphere. When combined with the longer timescales
of good atmospheric seeing compared with the visible, DKIST infrared
diagnostics are expected to be mainstays of solar physics in the DKIST
era. This paper will summarize the critical science areas addressed
by DKIST infrared instrumentation and invite the community to further
contribute to critical infrared science planning.
Title: Clear widens the field for observations of the Sun with
multi-conjugate adaptive optics
Authors: Schmidt, Dirk; Gorceix, Nicolas; Goode, Philip R.; Marino,
Jose; Rimmele, Thomas; Berkefeld, Thomas; Wöger, Friedrich; Zhang,
Xianyu; Rigaut, François; von der Lühe, Oskar
Bibcode: 2017A&A...597L...8S
Altcode:
The multi-conjugate adaptive optics (MCAO) pathfinder Clear
on the New Solar Telescope in Big Bear Lake has provided the
first-ever MCAO-corrected observations of the Sun that show a
clearly and visibly widened corrected field of view compared to
quasi-simultaneous observations with classical adaptive optics (CAO)
correction. Clear simultaneously uses three deformable mirrors, each
conjugated to a different altitude, to compensate for atmospheric
turbulence. While the MCAO correction was most effective over an
angle that is approximately three times wider than the angle that was
corrected by CAO, the full 53'' field of view did benefit from MCAO
correction. We further demonstrate that ground-layer-only correction
is attractive for solar observations as a complementary flavor of
adaptive optics for observational programs that require homogenous
seeing improvement over a wide field rather than diffraction-limited
resolution. We show illustrative images of solar granulation and
of a sunspot obtained on different days in July 2016, and present a
brief quantitative analysis of the generalized Fried parameters of
the images. The movies associated to Fig. 1 are available at http://www.aanda.org
Title: Daniel K. Inouye Solar Telescope: High-resolution observing
of the dynamic Sun
Authors: Tritschler, A.; Rimmele, T. R.; Berukoff, S.; Casini, R.;
Kuhn, J. R.; Lin, H.; Rast, M. P.; McMullin, J. P.; Schmidt, W.;
Wöger, F.; DKIST Team
Bibcode: 2016AN....337.1064T
Altcode:
The 4-m aperture Daniel K. Inouye Solar Telescope (DKIST) formerly
known as the Advanced Technology Solar Telescope (ATST) is currently
under construction on Haleakalā (Maui, Hawai'i) projected to
start operations in 2019. At the time of completion, DKIST will be
the largest ground-based solar telescope providing unprecedented
resolution and photon collecting power. The DKIST will be equipped
with a set of first-light facility-class instruments offering unique
imaging, spectroscopic and spectropolarimetric observing opportunities
covering the visible to infrared wavelength range. This first-light
instrumentation suite will include: a Visible Broadband Imager (VBI) for
high-spatial and -temporal resolution imaging of the solar atmosphere; a
Visible Spectro-Polarimeter (ViSP) for sensitive and accurate multi-line
spectropolarimetry; a Fabry-Pérot based Visible Tunable Filter
(VTF) for high-spatial resolution spectropolarimetry; a fiber-fed
Diffraction-Limited Near Infra-Red Spectro-Polarimeter (DL-NIRSP)
for two-dimensional high-spatial resolution spectropolarimetry
(simultaneous spatial and spectral information); and a Cryogenic Near
Infra-Red Spectro-Polarimeter (Cryo-NIRSP) for coronal magnetic field
measurements and on-disk observations of, e.g., the CO lines at 4.7
μm. We will provide an overview of the DKIST's unique capabilities
with strong focus on the first-light instrumentation suite, highlight
some of the additional properties supporting observations of transient
and dynamic solar phenomena, and touch on some operational strategies
and the DKIST critical science plan.
Title: Bottom-up laboratory testing of the DKIST Visible Broadband
Imager (VBI)
Authors: Ferayorni, Andrew; Beard, Andrew; Cole, Wes; Gregory, Scott;
Wöeger, Friedrich
Bibcode: 2016SPIE.9911E..06F
Altcode:
The Daniel K. Inouye Solar Telescope (DKIST) is a 4-meter solar
observatory under construction at Haleakala, Hawaii [1]. The Visible
Broadband Imager (VBI) is a first light instrument that will record
images at the highest possible spatial and temporal resolution of the
DKIST at a number of scientifically important wavelengths [2]. The VBI
is a pathfinder for DKIST instrumentation and a test bed for developing
processes and procedures in the areas of unit, systems integration,
and user acceptance testing. These test procedures have been developed
and repeatedly executed during VBI construction in the lab as part
of a "test early and test often" philosophy aimed at identifying and
resolving issues early thus saving cost during integration test and
commissioning on summit. The VBI team recently completed a bottom up
end-to-end system test of the instrument in the lab that allowed the
instrument's functionality, performance, and usability to be validated
against documented system requirements. The bottom up testing approach
includes four levels of testing, each introducing another layer in the
control hierarchy that is tested before moving to the next level. First
the instrument mechanisms are tested for positioning accuracy and
repeatability using a laboratory position-sensing detector (PSD). Second
the real-time motion controls are used to drive the mechanisms to verify
speed and timing synchronization requirements are being met. Next the
high-level software is introduced and the instrument is driven through
a series of end-to-end tests that exercise the mechanisms, cameras,
and simulated data processing. Finally, user acceptance testing is
performed on operational and engineering use cases through the use of
the instrument engineering graphical user interface (GUI). In this
paper we present the VBI bottom up test plan, procedures, example
test cases and tools used, as well as results from test execution in
the laboratory. We will also discuss the benefits realized through
completion of this testing, and share lessons learned from the bottoms
up testing process.
Title: Construction status of the Daniel K. Inouye solar telescope
Authors: McMullin, Joseph P.; Rimmele, Thomas R.; Warner, Mark;
Martinez Pillet, Valentin; Casini, Roberto; Berukoff, Steve; Craig,
Simon C.; Elmore, David; Ferayorni, Andrew; Goodrich, Bret D.;
Hubbard, Robert P.; Harrington, David; Hegwer, Steve; Jeffers, Paul;
Johansson, Erik M.; Kuhn, Jeff; Lin, Haosheng; Marshall, Heather;
Mathioudakis, Mihalis; McBride, William R.; McVeigh, William; Phelps,
LeEllen; Schmidt, Wolfgang; Shimko, Steve; Sueoka, Stacey; Tritschler,
Alexandra; Williams, Timothy R.; Wöger, Friedrich
Bibcode: 2016SPIE.9906E..1BM
Altcode:
We provide an update on the construction status of the Daniel
K. Inouye Solar Telescope. This 4-m diameter facility is designed to
enable detection and spatial/temporal resolution of the predicted,
fundamental astrophysical processes driving solar magnetism at
their intrinsic scales throughout the solar atmosphere. These data
will drive key research on solar magnetism and its influence on
solar winds, flares, coronal mass ejections and solar irradiance
variability. The facility is developed to support a broad wavelength
range (0.35 to 28 microns) and will employ state-of-the-art adaptive
optics systems to provide diffraction limited imaging, resolving
features approximately 20 km on the Sun. At the start of operations,
there will be five instruments initially deployed: Visible Broadband
Imager (VBI; National Solar Observatory), Visible SpectroPolarimeter
(ViSP; NCAR High Altitude Observatory), Visible Tunable Filter (VTF
(a Fabry-Perot tunable spectropolarimeter); Kiepenheuer Institute for
Solarphysics), Diffraction Limited NIR Spectropolarimeter (DL-NIRSP;
University of Hawaii, Institute for Astronomy) and the Cryogenic NIR
Spectropolarimeter (Cryo-NIRSP; University of Hawaii, Institute for
Astronomy). As of mid-2016, the project construction is in its 4th
year of site construction and 7th year overall. Major milestones in
the off-site development include the conclusion of the polishing of
the M1 mirror by University of Arizona, College of Optical Sciences,
the delivery of the Top End Optical Assembly (L3), the acceptance of
the Deformable Mirror System (Xinetics); all optical systems have been
contracted and are either accepted or in fabrication. The Enclosure
and Telescope Mount Assembly passed through their factory acceptance
in 2014 and 2015, respectively. The enclosure site construction
is currently concluding while the Telescope Mount Assembly site
erection is underway. The facility buildings (Utility and Support
and Operations) have been completed with ongoing work on the thermal
systems to support the challenging imaging requirements needed for the
solar research. Finally, we present the construction phase performance
(schedule, budget) with projections for the start of early operations.
Title: DKIST visible broadband imager alignment in laboratory:
first results
Authors: Sekulic, Predrag; Gregory, Scott B.; Hegwer, Steve L.;
Ferayorni, Andrew; Woeger, Friedrich
Bibcode: 2016SPIE.9908E..5AS
Altcode:
The Visible Broadband Imager (VBI) Blue and Red channels are the first
Daniel K. Inouye Solar Telescope (DKIST) instruments that have been
aligned and tested in a laboratory. This paper describes the optical
alignment method of the VBI as performed in the laboratory. The
objective of this preliminary alignment is to test and validate the
optical alignment method that will be used during final alignment on
the telescope, to measure the VBI performances and to verify that it
meets specification. The optical alignment method is defined by three
major steps. The first step is realized by combining the optical
and mechanical models into the Spatial Analyzer (SA) software, and
extracting the data serving as target values during alignment. The
second step is the mechanical alignment and allows to accurately
position the optics in the instrument coordinate system by using
a Coordinate Measurement Machine (CMM) arm and a theodolite. This
step has led to a great initial positioning and has allowed reaching
an initial wavefront error before optical alignment close to the
specification. The last step, performed by interferometry, allows fine
alignment to compensate the residual aberrations created by misalignment
and manufacturing tolerances. This paper presents also an alignment
method to compute the shifts and tilts of compensating lenses to correct
the residual aberrations. This paper describes first results of the
VBI instruments performances measured in the laboratory and confirm
the validity of the alignment process that will be reproduced during
final alignment on the telescope.
Title: Project management and control of the Daniel K. Inouye Solar
Telescope
Authors: McMullin, Joseph P.; McVeigh, William; Warner, Mark; Rimmele,
Thomas R.; Craig, Simon C.; Ferayorni, Andrew; Goodrich, Bret D.;
Hubbard, Robert P.; Hunter, Rex; Jeffers, Paul; Johansson, Erik;
Marshall, Heather; McBride, William R.; Phelps, LeEllen; Shimko,
Steve; Tritschler, Alexandra; Williams, Timothy R.; Wöger, Friedrich
Bibcode: 2016SPIE.9911E..0KM
Altcode:
We provide a brief update on the construction status of the Daniel
K. Inouye Solar Telescope, a $344M, 10-year construction project to
design and build the world's largest solar physics observatory. We
review the science drivers along with the challenges in meeting
the evolving scientific needs over the course of the construction
period without jeopardizing the systems engineering and management
realization. We review the tools, processes and performance measures
in use in guiding the development as well as the risks and challenges
as the project transitions through various developmental phases. We
elaborate on environmental and cultural compliance obligations in
building in Hawai'i. We discuss the broad "lessons learned". Finally,
we discuss the project in the context of the evolving management
oversight within the US (in particular under the NSF).
Title: Progress in multi-conjugate adaptive optics at Big Bear
Solar Observatory
Authors: Schmidt, Dirk; Gorceix, Nicolas; Marino, Jose; Berkefeld,
Thomas; Rimmele, Thomas; Zhang, Xianyu; Wöger, Friedrich; Goode, Phil
Bibcode: 2016SPIE.9909E..29S
Altcode:
The multi-conjugate adaptive optics (MCAO) system for solar observations
at the 1.6-meter clear aperture New Solar Telescope (NST) of the Big
Bear Solar Observatory (BBSO) in Big Bear Lake, California, enables us
to study fundamental design questions in solar MCAO experimentally. It
is the pathfinder for MCAO of the upcoming Daniel K. Inoyue Solar
Telescope (DKIST). This system is very flexible and offers various
optical configurations such as different sequencings of deformable
mirrors (DMs) and wavefront sensors (WFS), which are hard to simulate
conclusively. We show preliminary results and summarize the design, and
2016 updates to the MCAO system. The system utilizes three DMs. One of
which is conjugate to the telescope pupil, and the other two to distinct
higher altitudes. The pupil DM can be either placed into a pupil image
up- or downstream of the high-altitude DMs. The high-altitude DMs can
be separately and quickly conjugated to various altitudes between 2 and
8 km. Three Shack-Hartmann WFS units are available, one for low-order,
multi-directional sensing and two high-order on-axis sensing.
Title: A review of solar adaptive optics
Authors: Schmidt, Dirk; Rimmele, Thomas; Marino, Jose; Wöger,
Friedrich
Bibcode: 2016SPIE.9909E..0XS
Altcode:
Adaptive Optics (AO) that compensates for atmospheric turbulence is
a standard tool for high angular resolution observations of the Sun
at most ground-based observatories today. AO systems as deployed at
major solar telescopes allow for diffraction limited resolution in the
visible light regime. Anisoplanatism of the turbulent air volume limits
the effectivity of classical AO to a small region, typically of order 10
seconds of arc. Scientifically interesting features on the solar surface
are often larger thus multi-conjugate adaptive optics (MCAO) is being
developed to enlarge the corrected field of view. Dedicated wavefront
sensors for observations of solar prominences off the solar limb with
AO have been deployed. This paper summarizes wavefront sensing concepts
specific to solar adaptive optics applications, like the correlating
Shack-Hartmann wavefront sensor (SH-WFS), multi-directional sensing with
wide-field SH-WFSs, and gives a brief overview of recent developments.
Title: Status of the DKIST system for solar adaptive optics
Authors: Johnson, Luke C.; Cummings, Keith; Drobilek, Mark; Johansson,
Erik; Marino, Jose; Richards, Kit; Rimmele, Thomas; Sekulic, Predrag;
Wöger, Friedrich
Bibcode: 2016SPIE.9909E..0YJ
Altcode:
When the Daniel K. Inouye Solar Telescope (DKIST) achieves first
light in 2019, it will deliver the highest spatial resolution images
of the solar atmosphere ever recorded. Additionally, the DKIST will
observe the Sun with unprecedented polarimetric sensitivity and
spectral resolution, spurring a leap forward in our understanding
of the physical processes occurring on the Sun. The DKIST wavefront
correction system will provide active alignment control and jitter
compensation for all six of the DKIST science instruments. Five of
the instruments will also be fed by a conventional adaptive optics
(AO) system, which corrects for high frequency jitter and atmospheric
wavefront disturbances. The AO system is built around an extended-source
correlating Shack-Hartmann wavefront sensor, a Physik Instrumente fast
tip-tilt mirror (FTTM) and a Xinetics 1600-actuator deformable mirror
(DM), which are controlled by an FPGA-based real-time system running
at 1975 Hz. It is designed to achieve on-axis Strehl of 0.3 at 500
nm in median seeing (r0 = 7 cm) and Strehl of 0.6 at 630
nm in excellent seeing (r0 = 20 cm). The DKIST wavefront
correction team has completed the design phase and is well into the
fabrication phase. The FTTM and DM have both been delivered to the
DKIST laboratory in Boulder, CO. The real-time controller has been
completed and is able to read out the camera and deliver commands to
the DM with a total latency of approximately 750 μs. All optics and
optomechanics, including many high-precision custom optics, mounts,
and stages, are completed or nearing the end of the fabrication process
and will soon undergo rigorous acceptance testing. Before installing the
wavefront correction system at the telescope, it will be assembled as
a testbed in the laboratory. In the lab, performance tests beginning
with component-level testing and continuing to full system testing
will ensure that the wavefront correction system meets all performance
requirements. Further work in the lab will focus on fine-tuning our
alignment and calibration procedures so that installation and alignment
on the summit will proceed as efficiently as possible.
Title: Construction Status and Early Science with the Daniel K. Inouye
Solar Telescope
Authors: McMullin, Joseph P.; Rimmele, Thomas R.; Warner, Mark;
Martinez Pillet, Valentin; Craig, Simon; Woeger, Friedrich; Tritschler,
Alexandra; Berukoff, Steven J.; Casini, Roberto; Goode, Philip R.;
Knoelker, Michael; Kuhn, Jeffrey Richard; Lin, Haosheng; Mathioudakis,
Mihalis; Reardon, Kevin P.; Rosner, Robert; Schmidt, Wolfgang
Bibcode: 2016SPD....4720101M
Altcode:
The 4-m Daniel K. Inouye Solar Telescope (DKIST) is in its seventh
year of overall development and its fourth year of site construction
on the summit of Haleakala, Maui. The Site Facilities (Utility
Building and Support & Operations Building) are in place with
ongoing construction of the Telescope Mount Assembly within. Off-site
the fabrication of the component systems is completing with early
integration testing and verification starting.Once complete this
facility will provide the highest sensitivity and resolution for study
of solar magnetism and the drivers of key processes impacting Earth
(solar wind, flares, coronal mass ejections, and variability in solar
output). The DKIST will be equipped initially with a battery of first
light instruments which cover a spectral range from the UV (380 nm)
to the near IR (5000 nm), and capable of providing both imaging and
spectro-polarimetric measurements throughout the solar atmosphere
(photosphere, chromosphere, and corona); these instruments are being
developed by the National Solar Observatory (Visible Broadband Imager),
High Altitude Observatory (Visible Spectro-Polarimeter), Kiepenheuer
Institute (Visible Tunable Filter) and the University of Hawaii
(Cryogenic Near-Infrared Spectro-Polarimeter and the Diffraction-Limited
Near-Infrared Spectro-Polarimeter). Further, a United Kingdom consortium
led by Queen's University Belfast is driving the development of high
speed cameras essential for capturing the highly dynamic processes
measured by these instruments. Finally, a state-of-the-art adaptive
optics system will support diffraction limited imaging capable of
resolving features approximately 20 km in scale on the Sun.We present
the overall status of the construction phase along with the current
challenges as well as a review of the planned science testing and the
transition into early science operations.
Title: The DKIST Instrumentation Suite
Authors: Woeger, Friedrich
Bibcode: 2016SPD....4720102W
Altcode:
The Daniel K. Inouye Solar Telescope with its four meter diameter
aperture will be the largest telescope in the world for solar
observations when it is commissioned in the year 2019. In order to
harness its scientific potential immediately, DKIST will integrate
five instruments that each will provide unique functionality to
measure properties of the solar atmosphere at unprecedented spatial
resolution.In this paper we discuss the unique capabilities in the DKIST
instrument suite that consists of the Visible Broadband Imager (VBI),
the Visible Spectro-Polarimeter (ViSP), the Visible Tunable Filter
(VTF), the Diffraction-Limited Near-Infrared Spectro-Polarimeter
(DL-NIRSP), and the Cryogenic Near-Infrared Spectro-Polarimeter
(Cryo-NIRSP).In addition, we will explain the facility's approach to
supporting high spatial resolution data acquisition with multiple
instruments simultaneously by means of the Facility Instrument
Distribution Optics. This system of wavelength separating and
interchangeable beamsplitters will enable a variety of different
ways to optically configure the light beam to the instruments. This
approach ensures that the DKIST instruments can use their individual
advantages in a multitude of different observing scenarios. The DKIST
instrumentation suite will enable crucial new insights into complex
physical processes that occur on spatial scales that are smaller than
any solar structure observed in the past.
Title: High-cadence observations of spicular-type events on the Sun
Authors: Shetye, J.; Doyle, J. G.; Scullion, E.; Nelson, C. J.;
Kuridze, D.; Henriques, V.; Woeger, F.; Ray, T.
Bibcode: 2016A&A...589A...3S
Altcode: 2016arXiv160108087S
Context. Chromospheric observations taken at high-cadence and
high-spatial resolution show a range of spicule-like features,
including Type-I, Type-II (as well as rapid blue-shifted excursions
(RBEs) and rapid red-shifted excursions (RREs) which are thought to
be on-disk counterparts of Type-II spicules) and those which seem to
appear within a few seconds, which if interpreted as flows would imply
mass flow velocities in excess of 1000 km s-1.
Aims:
This article seeks to quantify and study rapidly appearing spicular-type
events. We also compare the multi-object multi-frame blind deconvolution
(MOMFBD) and speckle reconstruction techniques to understand if
these spicules are more favourably observed using a particular
technique.
Methods: We use spectral imaging observations taken
with the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1-m
Solar Telescope. Data was sampled at multiple positions within the Hα
line profile for both an on-disk and limb location.
Results: The
data is host to numerous rapidly appearing features which are observed
at different locations within the Hα line profile. The feature's
durations vary between 10-20 s and lengths around 3500 km. Sometimes,
a time delay in their appearance between the blue and red wings of
3-5 s is evident, whereas, sometimes they are near simultaneous. In
some instances, features are observed to fade and then re-emerge at
the same location several tens of seconds later.
Conclusions:
We provide the first statistical analysis of these spicules and suggest
that these observations can be interpreted as the line-of-sight (LOS)
movement of highly dynamic spicules moving in and out of the narrow 60
mÅ transmission filter that is used to observe in different parts of
the Hα line profile. The LOS velocity component of the observed fast
chromospheric features, manifested as Doppler shifts, are responsible
for their appearance in the red and blue wings of Hα line. Additional
work involving data at other wavelengths is required to investigate
the nature of their possible wave-like activity.
Title: Daniel K. Inouye Solar Telescope: Overview and Status
Authors: Rimmele, Thomas; McMullin, Joseph; Warner, Mark; Craig,
Simon; Woeger, Friedrich; Tritschler, Alexandra; Cassini, Roberto;
Kuhn, Jeff; Lin, Haosheng; Schmidt, Wolfgang; Berukoff, Steve; Reardon,
Kevin; Goode, Phil; Knoelker, Michael; Rosner, Robert; Mathioudakis,
Mihalis; DKIST TEAM
Bibcode: 2015IAUGA..2255176R
Altcode:
The 4m Daniel K. Inouye Solar Telescope (DKIST) currently under
construction on Haleakala, Maui will be the world’s largest solar
telescope. Designed to meet the needs of critical high resolution and
high sensitivity spectral and polarimetric observations of the sun,
this facility will perform key observations of our nearest star that
matters most to humankind. DKIST’s superb resolution and sensitivity
will enable astronomers to unravel many of the mysteries the Sun
presents, including the origin of solar magnetism, the mechanisms of
coronal heating and drivers of the solar wind, flares, coronal mass
ejections and variability in solar output. The all-reflecting, off-axis
design allows the facility to observe over a broad wavelength range and
enables DKIST to operate as a coronagraph. In addition, the photon flux
provided by its large aperture will be capable of routine and precise
measurements of the currently elusive coronal magnetic fields. The
state-of-the-art adaptive optics system provides diffraction limited
imaging and the ability to resolve features approximately 20 km on
the Sun. Five first light instruments, representing a broad community
effort, will be available at the start of operations: Visible Broadband
Imager (National Solar Observatory), Visible Spectro-Polarimeter (High
Altitude Observatory), Visible Tunable Filter (Kiepenheuer Institute,
Germany), Diffraction Limited NIR Spectro-Polarimeter (University
of Hawaii) and the Cryogenic NIR Spectro-Polarimeter (University of
Hawaii). High speed cameras for capturing highly dynamic processes
in the solar atmosphere are being developed by a UK consortium. Site
construction on Haleakala began in December 2012 and is progressing
on schedule. Operations are scheduled to begin in 2019. We provide an
overview of the facility, discuss the construction status, and present
progress with DKIST operations planning.
Title: DKIST: Observing the Sun at High Resolution
Authors: Tritschler, A.; Rimmele, T. R.; Berukoff, S.; Casini, R.;
Craig, S. C.; Elmore, D. F.; Hubbard, R. P.; Kuhn, J. R.; Lin, H.;
McMullin, J. P.; Reardon, K. P.; Schmidt, W.; Warner, M.; Woger, F.
Bibcode: 2015csss...18..933T
Altcode:
The 4-m aperture Daniel K. Inouye Solar Telescope (DKIST) formerly
known as the Advanced Technology Solar Telescope (ATST) and currently
under construction on Haleakalā (Maui, Hawai'i) will be the largest
solar ground-based telescope and leading resource for studying the
dynamic Sun and its phenomena at high spatial, spectral and temporal
resolution. Accurate and sensitive polarimetric observations at
high-spatial resolution throughout the solar atmosphere including the
corona is a high priority and a major science driver. As such the DKIST
will offer a combination of state-of-the-art instruments with imaging
and/or spectropolarimetric capabilities covering a broad wavelength
range. This first-light instrumentation suite will include: a Visible
Broadband Imager (VBI) for high-spatial and -temporal resolution
imaging of the solar atmosphere; a Visible Spectro-Polarimeter (ViSP)
for sensitive and accurate multi-line spectropolarimetry; a double
Fabry-Pérot based Visible Tunable Filter (VTF) for high-spatial
resolution spectropolarimetry; a fiber-fed 2D Diffraction-Limited Near
Infra-Red Spectro-Polarimeter (DL-NIRSP); and a Cryogenic Near Infra-Red
Spectro-Polarimeter (Cryo-NIRSP) for coronal magnetic field measurements
and on-disk observations of e.g. the CO lines at 4.7 microns. We
will provide a brief overview of the DKIST's unique capabilities to
perform spectroscopic and spectropolarimetric measurements of the solar
atmosphere using its first-light instrumentation suite, the status of
the construction project, and how facility and data access is provided
to the US and international community.
Title: The Daniel K. Inouye Solar Telescope: A Project Update.
Authors: Rimmele, T.; Berger, T.; McMullin, J.; Warner, M.; Casinsi,
R.; Kuhn, J.; Lin, H.; Woeger, F.; Schmidt, W.; Tritschler, A.;
Inouye, Daniel K.; Solar Telescope Team
Bibcode: 2014amos.confE..43R
Altcode:
The Advanced Technology Solar Telescope will be the largest solar
facility ever built. Designed and developed to meet the needs of
critical high resolution and high sensitivity spectral and polarimetric
observations of the sun, this facility will support key experiments
for the study of solar magnetism and its influence on the solar wind,
flares, coronal mass ejections and solar irradiance variability. The
4-meter diameter facility will operate over a broad wavelength range
(0.35 to 28 microns), using state-of-the-art adaptive optics systems to
provide diffraction limited imaging and the ability to resolve features
approximately 20 km on the Sun. Five first light instruments will be
available at the start of operations. Key subsystems have been designed
and fabrication is well underway, including the site construction,
which began in December 2012. We provide an update on the development
of the facilities both on site at the Haleakala Observatories in Maui
and the development of components around the world. We present the
overall construction and integration schedule leading to the start of
operations in mid-2019 and touch on operations aspects.
Title: Solar adaptive optics with the DKIST: status report
Authors: Johnson, Luke C.; Cummings, Keith; Drobilek, Mark; Gregory,
Scott; Hegwer, Steve; Johansson, Erik; Marino, Jose; Richards, Kit;
Rimmele, Thomas; Sekulic, Predrag; Wöger, Friedrich
Bibcode: 2014SPIE.9148E..1SJ
Altcode:
The DKIST wavefront correction system will be an integral part
of the telescope, providing active alignment control, wavefront
correction, and jitter compensation to all DKIST instruments. The
wavefront correction system will operate in four observing modes,
diffraction-limited, seeing-limited on-disk, seeing-limited coronal,
and limb occulting with image stabilization. Wavefront correction for
DKIST includes two major components: active optics to correct low-order
wavefront and alignment errors, and adaptive optics to correct wavefront
errors and high-frequency jitter caused by atmospheric turbulence. The
adaptive optics system is built around a fast tip-tilt mirror and a
1600 actuator deformable mirror, both of which are controlled by an
FPGA-based real-time system running at 2 kHz. It is designed to achieve
on-axis Strehl of 0.3 at 500 nm in median seeing (r0 = 7
cm) and Strehl of 0.6 at 630 nm in excellent seeing (r0 =
20 cm). We present the current status of the DKIST high-order adaptive
optics, focusing on system design, hardware procurements, and error
budget management.
Title: DKIST visible broadband imager interference filters
Authors: Wöger, Friedrich
Bibcode: 2014SPIE.9147E..9IW
Altcode:
The Visible Broadband Imager (VBI) is one of several first-light
instruments of the Daniel K. Inouye Solar Telescope (DKIST, formerly
known as the Advanced Technology Solar Telescope (ATST)). Operating
at discrete wavelengths within a range of 390-860 nm, the VBI will
be capable of sampling the solar atmosphere in several layers at the
diffraction limit of DKIST's 4 meter aperture. The layers are selected
by the peak wavelength and bandpass width of its interference filters
that have to be manufactured to very tight specifications. We present
the results of testing performed at the National Solar Observatory's
Dunn Solar Telescope (DST) to confirm that the requirements were met
by the vendor.
Title: Construction status of the Daniel K. Inouye Solar Telescope
Authors: McMullin, Joseph P.; Rimmele, Thomas R.; Martínez Pillet,
Valentin; Berger, Thomas E.; Casini, Roberto; Craig, Simon C.; Elmore,
David F.; Goodrich, Bret D.; Hegwer, Steve L.; Hubbard, Robert P.;
Johansson, Erik M.; Kuhn, Jeffrey R.; Lin, Haosheng; McVeigh, William;
Schmidt, Wolfgang; Shimko, Steve; Tritschler, Alexandra; Warner,
Mark; Wöger, Friedrich
Bibcode: 2014SPIE.9145E..25M
Altcode:
The Daniel K. Inouye Solar Telescope (DKIST, renamed in December 2013
from the Advanced Technology Solar Telescope) will be the largest
solar facility built when it begins operations in 2019. Designed
and developed to meet the needs of critical high resolution and high
sensitivity spectral and polarimetric observations of the Sun, the
observatory will enable key research for the study of solar magnetism
and its influence on the solar wind, flares, coronal mass ejections
and solar irradiance variations. The 4-meter class facility will
operate over a broad wavelength range (0.38 to 28 microns, initially
0.38 to 5 microns), using a state-of-the-art adaptive optics system to
provide diffraction-limited imaging and the ability to resolve features
approximately 25 km on the Sun. Five first-light instruments will be
available at the start of operations: Visible Broadband Imager (VBI;
National Solar Observatory), Visible SpectroPolarimeter (ViSP; NCAR High
Altitude Observatory), Visible Tunable Filter (VTF; Kiepenheuer Institut
für Sonnenphysik), Diffraction Limited Near InfraRed SpectroPolarimeter
(DL-NIRSP; University of Hawai'i, Institute for Astronomy) and the
Cryogenic Near InfraRed SpectroPolarimeter (Cryo-NIRSP; University of
Hawai'i, Institute for Astronomy). As of mid-2014, the key subsystems
have been designed and fabrication is well underway, including the
site construction, which began in December 2012. We provide an update
on the development of the facilities both on site at the Haleakalā
Observatories on Maui and the development of components around the
world. We present the overall construction and integration schedule
leading to the handover to operations in mid 2019. In addition, we
outline the evolving challenges being met by the project, spanning the
full spectrum of issues covering technical, fiscal, and geographical,
that are specific to this project, though with clear counterparts to
other large astronomical construction projects.
Title: The Daniel K. Inouye Solar Telescope first light instruments
and critical science plan
Authors: Elmore, David F.; Rimmele, Thomas; Casini, Roberto; Hegwer,
Steve; Kuhn, Jeff; Lin, Haosheng; McMullin, Joseph P.; Reardon, Kevin;
Schmidt, Wolfgang; Tritschler, Alexandra; Wöger, Friedrich
Bibcode: 2014SPIE.9147E..07E
Altcode:
The Daniel K. Inouye Solar Telescope is a 4-meter-class all-reflecting
telescope under construction on Haleakalā mountain on the island of
Maui, Hawai'i. When fully operational in 2019 it will be the world's
largest solar telescope with wavelength coverage of 380 nm to 28 microns
and advanced Adaptive Optics enabling the highest spatial resolution
measurements of the solar atmosphere yet achieved. We review the
first-generation DKIST instrument designs, select critical science
program topics, and the operations and data handling and processing
strategies to accomplish them.
Title: Prominence Science with ATST Instrumentation
Authors: Rimmele, Thomas; Berger, Thomas; Casini, Roberto; Elmore,
David; Kuhn, Jeff; Lin, Haosheng; Schmidt, Wolfgang; Wöger, Friedrich
Bibcode: 2014IAUS..300..362R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) is under construction
on Maui, HI. With its unprecedented resolution and photon collecting
power ATST will be an ideal tool for studying prominences and filaments
and their role in producing Coronal Mass Ejections that drive Space
Weather. The ATST facility will provide a set of first light instruments
that enable imaging and spectroscopy of the dynamic filament and
prominence structure at 8 times the resolution of Hinode. Polarimeters
allow high precision chromospheric and coronal magnetometry at visible
and infrared (IR) wavelengths. This paper summarizes the capabilities
of the ATST first-light instrumentation with focus on prominence and
filament science.
Title: Future Diagnostic Capabilities: The 4-meter Daniel K. Inouye
Solar Telescope
Authors: Berger, Thomas; Reardon, Kevin; Elmore, David; Woeger,
Friedrich; Tritschler, Alexandra; Rimmele, Thomas
Bibcode: 2014cosp...40E.294B
Altcode:
We discuss the observational capabilities of the Daniel K. Inouye
Solar Telescope (DKSIT), formerly known as the Advanced Technology
Solar Telescope (ATST), currently under construction on Haleakala
Mountain on the island of Maui, Hawaii, with first light anticipated
in mid-2019. The DKIST will be a 4-meter aperture Gregorian telescope
with advanced environmental control and adaptive optics capable of
producing diffraction-limited resolution in visible light of 0.03"
or about 20 km in the solar photosphere. The first light instrument
suite will include the Visible Broadband Imager (VBI), an interference
filter-based instrument capable of 30 Hz imaging of photospheric and
chromospheric magnetic structures in the 380 to 800 nm wavelength
range. All VBI images will be reconstructed in near-real-time using
the KISIP speckle reconstruction algorithm adapted to the DKIST
optical and AO configuration. The Visible Spectropolarimeter (ViSP)
instrument being fabricated by the High Altitude Observatory (HAO) will
enable high-precision slit-spectropolarimetery in any three spectral
regions from 380 to 900 nm. The ViSP instrument will be the highest
precision spectropolarimeter ever produced with a spatial resolution
of approximately 40 km at 600 nm and temporal resolution of 10s to
achieve 1e-03 polarimetric precision. The Visible Tunable Filter (VTF)
instrument under fabrication at the Kiepenheuer Institute for Solar
Physics (KIS) is a triple-etalon Fabry-Perot imaging spectropolarimeter
instrument capable of diffraction limited measurements of the Fe I
630.2 nm and Ca II 854.2 nm spectral lines for Doppler and magnetic
measurements in the photosphere and chromosphere, respectively. The
VTF will also enable the highest spatial and temporal resolution
observations yet achieved in the H-alpha line for detailed studies of
chromospheric dynamics in response to photospheric magnetic drivers. The
Diffraction-Limited Near-IR Spectropolarimeter (DL-NiRSP) and the
Cryogenic Near-IR Spectropolarimeter (Cryo-NiRSP) instruments, both
under fabrication at the University of Hawaii, will enable polarimetric
and spectroscopic investigations in the largely unexplored infra-red
spectral region. The DL-NiRSP will span 900 nm to 2.5 microns in
wavelength and include a novel fiber-optic "Integral Field Unit"
(IFU) for true imaging spectropolarimetry in three simultaneous
spectral regions over a variable field of view. This instrument
will enable revolutionary measurements of prominence magnetic fields
and will also, in the wider field mode, enable coronal polarimetric
studies. The Cryo-NiRSP instrument spans the 1--5 micron wavelength
range and will make near-diffraction limited 0.3" resolution slit-scan
measurements of the coronal magnetic field out to 1.3 solar radii
with temporal resolution measured in minutes. The DKIST facility
will undergo extensive polarimetric calibration to ensure that the
ultimate goal of 5e-04 polarimetic precision is obtainable under the
best conditions. All of the data from the DKIST will be transmitted
to the central DKIST data center in Boulder, Colorado where automated
reduction and calibration pipelines will rapidly provide the community
with calibrated data products for use in science investigations. The
DKIST will also be operated in a "Service Mode" access model in which
investigators will not be required to travel to the telescope to
accomplish their science observations.
Title: ATST and Solar AO state of art
Authors: Rimmele, Thomas; Woeger, Friedrich; Marino, Jose
Bibcode: 2013aoel.confE.108R
Altcode:
The 4 meter aperture Advanced Technology Solar Telescope (ATST) is
an ELT for solar astronomy, and as such will address a broad range
of science questions that require its AO system to operate in several
different observing scenarios. We review the science drivers that lead
to the most demanding ATST AO system requirements, such as high Strehl
ratios at visible wavelengths, MCAO correction, and photon starved,
extended FOV wavefront sensing using large, faint structures at the
limb of the Sun. Within the context of exisiting high-order AO systems
for solar telescopes we present an overview over the current ATST AO
system design and capabilities. Finally, we will describe the widely
used post-facto image processing techniques of AO corrected solar
imaging and spectroscopic data that are required to achieve the desired
spatial resolution especially at the short end (380 nm) of the visible
spectrum over ATST's full FOV. We will lay out how these techniques will
be supported in the AO system to help ATST achieve its scientific goals.
Title: The Advanced Technology Solar Telescope: Science Drivers and
Construction Status
Authors: Rimmele, Thomas; Berger, Thomas; McMullin, Joseph; Keil,
Stephen; Goode, Phil; Knoelker, Michael; Kuhn, Jeff; Rosner, Robert;
Casini, Roberto; Lin, Haosheng; Woeger, Friedrich; von der Luehe,
Oskar; Tritschler, Alexandra; Atst Team
Bibcode: 2013EGUGA..15.6305R
Altcode:
The 4-meter Advance Technology Solar Telescope (ATST) currently
under construction on the 3000 meter peak of Haleakala on Maui,
Hawaii will be the world's most powerful solar telescope and the
leading ground-based resource for studying solar magnetism. The
solar atmosphere is permeated by a 'magnetic carpet' that constantly
reweaves itself to control solar irradiance and its effects on Earth's
climate, the solar wind, and space weather phenomena such as flares and
coronal mass ejections. Precise measurement of solar magnetic fields
requires a large-aperture solar telescope capable of resolving a few
tens of kilometers on the solar surface. With its 4 meter aperture,
the ATST will for the first time resolve magnetic structure at the
intrinsic scales of plasma convection and turbulence. The ATST's
ability to perform accurate and precise spectroscopic and polarimetric
measurements of magnetic fields in all layers of the solar atmosphere,
including accurate mapping of the elusive coronal magnetic fields,
will be transformative in advancing our understanding of the magnetic
solar atmosphere. The ATST will utilize the Sun as an important astro-
and plasma-physics "laboratory" demonstrating key aspects of omnipresent
cosmic magnetic fields. The ATST construction effort is led by the US
National Solar Observatory. State-of-the-art instrumentation will be
constructed by US and international partner institutions. The technical
challenges the ATST is facing are numerous and include the design of the
off-axis main telescope, the development of a high order adaptive optics
system that delivers a corrected beam to the instrument laboratory,
effective handling of the solar heat load on optical and structural
elements, and minimizing scattered light to enable observations
of the faint corona. The ATST project has transitioned from design
and development to its construction phase. The project has awarded
design and fabrication contracts for major telescope subsystems. Site
construction has commenced following the successful conclusion of
the site permitting process. Science goals and construction status of
telescope and instrument systems will be discussed.
Title: The Visible Broadband Imager: The Sun at High Spatial and
Temporal Resolution
Authors: Wöger, F.; McBride, W.; Ferayorni, A.; Gregory, S.; Hegwer,
S.; Tritschler, A.; Uitenbroek, H.
Bibcode: 2012ASPC..463..431W
Altcode:
The Visible Broadband Imager (VBI) will be the primary first-light
instrument for the Advanced Technology Solar Telescope (ATST). It is
designed to observe the solar atmosphere at heights ranging from the
photosphere to chromosphere. High frame-rate detectors that sample
the FOV of up to 2.8 arcmin in diameter critically at the diffraction
limit of ATST's 4 meter aperture will provide near real-time speckle
reconstruction imaging. With its focus on high-spatial resolution, the
VBI will be addressing scientific questions related to the smallest
structures visible in the solar atmosphere with high photometric
precision. The capability to observe the solar atmosphere with a
cadence of about 3 seconds per reconstructed image will enable the VBI
to temporally resolve fast evolving structures. In this contribution we
present the major aspects of the current design of the VBI and highlight
some scientific questions related to fast evolving, small-scale features
within the solar atmosphere that the VBI will address.
Title: Construction of the Advanced Technology Solar Telescope
Authors: Rimmele, T. R.; Keil, S.; McMullin, J.; Knölker, M.; Kuhn,
J. R.; Goode, P. R.; Rosner, R.; Casini, R.; Lin, H.; Tritschler,
A.; Wöger, F.; ATST Team
Bibcode: 2012ASPC..463..377R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) will be the most
powerful solar telescope and the world's leading ground-based resource
for studying solar magnetism that controls the solar wind, flares,
coronal mass ejections and variability in the Sun's output. The
project has entered its construction phase. Major subsystems have
been contracted. As its highest priority science driver ATST shall
provide high resolution and high sensitivity observations of the
dynamic solar magnetic fields throughout the solar atmosphere,
including the corona at infrared wavelengths. With its 4m aperture,
ATST will resolve features at 0.″03 at visible wavelengths and
obtain 0.″1 resolution at the magnetically highly sensitive near
infrared wavelengths. A high order adaptive optics system delivers a
corrected beam to the initial set of state-of-the-art, facility class
instrumentation located in the Coudé laboratory facility. The initial
set of first generation instruments consists of five facility class
instruments, including imagers and spectro-polarimeters. The high
polarimetric sensitivity and accuracy required for measurements of
the illusive solar magnetic fields place strong constraints on the
polarization analysis and calibration. Development and construction
of a four-meter solar telescope presents many technical challenges,
including thermal control of the enclosure, telescope structure and
optics and wavefront control. A brief overview of the science goals
and observational requirements of the ATST will be given, followed by a
summary of the design status of the telescope and its instrumentation,
including design status of major subsystems, such as the telescope
mount assembly, enclosure, mirror assemblies, and wavefront correction
Title: 2nd ATST-EAST Workshop in Solar Physics: Magnetic Fields from
the Photosphere to the Corona
Authors: Rimmele, T. R.; Tritschler, A.; Wöger, F.; Collados Vera,
M.; Socas-Navarro, H.; Schlichenmaier, R.; Carlsson, M.; Berger, T.;
Cadavid, A.; Gilbert, P. R.; Goode, P. R.; Knölker, M.
Bibcode: 2012ASPC..463.....R
Altcode:
No abstract at ADS
Title: The Advanced Technology Solar Telescope: design and early
construction
Authors: McMullin, Joseph P.; Rimmele, Thomas R.; Keil, Stephen L.;
Warner, Mark; Barden, Samuel; Bulau, Scott; Craig, Simon; Goodrich,
Bret; Hansen, Eric; Hegwer, Steve; Hubbard, Robert; McBride, William;
Shimko, Steve; Wöger, Friedrich; Ditsler, Jennifer
Bibcode: 2012SPIE.8444E..07M
Altcode:
The National Solar Observatory’s (NSO) Advanced Technology Solar
Telescope (ATST) is the first large U.S. solar telescope accessible
to the worldwide solar physics community to be constructed in more
than 30 years. The 4-meter diameter facility will operate over a broad
wavelength range (0.35 to 28 μm ), employing adaptive optics systems to
achieve diffraction limited imaging and resolve features approximately
20 km on the Sun; the key observational parameters (collecting area,
spatial resolution, spectral coverage, polarization accuracy, low
scattered light) enable resolution of the theoretically-predicted,
fine-scale magnetic features and their dynamics which modulate the
radiative output of the sun and drive the release of magnetic energy
from the Sun’s atmosphere in the form of flares and coronal mass
ejections. In 2010, the ATST received a significant fraction of its
funding for construction. In the subsequent two years, the project has
hired staff and opened an office on Maui. A number of large industrial
contracts have been placed throughout the world to complete the detailed
designs and begin constructing the major telescope subsystems. These
contracts have included the site development, AandE designs, mirrors,
polishing, optic support assemblies, telescope mount and coudé
rotator structures, enclosure, thermal and mechanical systems, and
high-level software and controls. In addition, design development
work on the instrument suite has undergone significant progress;
this has included the completion of preliminary design reviews (PDR)
for all five facility instruments. Permitting required for physically
starting construction on the mountaintop of Haleakalā, Maui has also
progressed. This paper will review the ATST goals and specifications,
describe each of the major subsystems under construction, and review
the contracts and lessons learned during the contracting and early
construction phases. Schedules for site construction, key factory
testing of major subsystems, and integration, test and commissioning
activities will also be discussed.
Title: Accelerated speckle imaging with the ATST visible broadband
imager
Authors: Wöger, Friedrich; Ferayorni, Andrew
Bibcode: 2012SPIE.8451E..1CW
Altcode:
The Advanced Technology Solar Telescope (ATST), a 4 meter class
telescope for observations of the solar atmosphere currently in
construction phase, will generate data at rates of the order of 10
TB/day with its state of the art instrumentation. The high-priority
ATST Visible Broadband Imager (VBI) instrument alone will create two
data streams with a bandwidth of 960 MB/s each. Because of the related
data handling issues, these data will be post-processed with speckle
interferometry algorithms in near-real time at the telescope using
the cost-effective Graphics Processing Unit (GPU) technology that is
supported by the ATST Data Handling System. In this contribution, we
lay out the VBI-specific approach to its image processing pipeline,
put this into the context of the underlying ATST Data Handling System
infrastructure, and finally describe the details of how the algorithms
were redesigned to exploit data parallelism in the speckle image
reconstruction algorithms. An algorithm re-design is often required
to efficiently speed up an application using GPU technology; we have
chosen NVIDIA's CUDA language as basis for our implementation. We
present our preliminary results of the algorithm performance using our
test facilities, and base a conservative estimate on the requirements
of a full system that could achieve near real-time performance at ATST
on these results.
Title: ATST visible broadband imager
Authors: McBride, William R.; Wöger, Friedrich; Hegwer, Steve L.;
Ferayorni, Andrew; Gregory, B. Scott
Bibcode: 2012SPIE.8446E..1BM
Altcode:
The Advanced Technology Solar Telescope (ATST) is a 4 meter class
telescope for observation of the solar atmosphere currently in the
construction phase. The Visible Broadband Imager (VBI) is a diffraction
limited imaging instrument planned to be the first-light instrument in
the ATST instrumentation suite. The VBI is composed of two branches,
the "VBI blue" and the "VBI red", and uses state-of-the-art narrow
bandwidth interference filters and two custom designed high speed
filter wheels to take bursts of images that will be re-constructed
using a Graphics Processing Unit (GPU) optimized near-real-time speckle
image reconstruction engine. At first light, the VBI instrument will
produce diffraction-limited movies of solar activity at eight discrete
wavelengths with a field of view of 2 arc minutes square. In this
contribution, the VBI design team will discuss the capabilities of
the VBI and describe the design of the instrument, highlighting the
unique challenges faced in the development of this unique instrument.
Title: Characterization of an off-the-shelf detector for high-order
wavefront sensing in solar adaptive optics
Authors: Johnson, Luke C.; Richards, K.; Wöger, F.; Barden, Samuel;
Rimmele, T.
Bibcode: 2012SPIE.8447E..6DJ
Altcode:
When completed, the Advanced Technology Solar Telescope (ATST) will
be the largest and most technologically advanced solar telescope in
the world. As such, it faces many challenges that have not previously
been solved. One of these challenges is the high-order wavefront sensor
(HOWFS) for the ATST adaptive optics system. The HOWFS requires a 960 x
960 detector array that must run at a 2 kHz frame rate in order for the
adaptive optics to achieve its required bandwidth. This detector must
be able to accurately image low-contrast solar granulation in order to
provide usable wavefront information. We have identified the Vision
Research DS-440 as an off-the-shelf solution for the HOWFS detector
and demonstrate tests proving that the camera will be able to lock the
adaptive optics loop on solar granulation in commonly-experienced
daytime seeing conditions. Tests presented quantify the noise,
linearity, gain, stability, and well depth of the camera. Laboratory
tests with artificial targets demonstrate its ability to accurately
track low-contrast objects and on-sky demonstrations showcase the
camera's performance in realistic observing conditions.
Title: The adaptive optics and wavefront correction systems for the
Advanced Technology Solar Telescope
Authors: Richards, K.; Rimmele, T.; Hegwer, S. L.; Upton, R. S.;
Woeger, F.; Marino, J.; Gregory, S.; Goodrich, B.
Bibcode: 2010SPIE.7736E..08R
Altcode: 2010SPIE.7736E...6R
The high order adaptive optics (HOAO) system is the centerpiece of
the ATST wavefront correction system. The ATST wavefront correction
system is required to achieve a Strehl of S = 0.6 or better at
visible wavelength. The system design closely follows the successful
HOAO implementation at the Dunn Solar Telescope and is based on the
correlating Shack-Hartmann wavefront sensor. In addition to HOAO
the ATST will utilize wavefront sensors to implement active optics
(aO) and Quasi Static Alignment (QSA) of the telescope optics, which
includes several off-axis elements. Provisions for implementation of
Multi-conjugate adaptive optics have been made with the design of the
optical path that feeds the instrumentation at the coudé station. We
will give an overview of the design of individual subsystems of the
ATST wavefront correction system and describe some of the unique
features of the ATST wavefront correction system, such as the need
for thermally controlled corrective elements.
Title: Solar multiconjugate adaptive optics at the Dunn Solar
Telescope
Authors: Rimmele, T. R.; Woeger, F.; Marino, J.; Richards, K.; Hegwer,
S.; Berkefeld, T.; Soltau, D.; Schmidt, D.; Waldmann, T.
Bibcode: 2010SPIE.7736E..31R
Altcode: 2010SPIE.7736E.101R
Solar observations are performed over an extended field of view and
the isoplanatic patch over which conventional adaptive optics (AO)
provides diffraction limited resolution is a severe limitation. The
development of multi-conjugate adaptive optics (MCAO) for the next
generation large aperture solar telescopes is thus a top priority. The
Sun is an ideal object for the development of MCAO since solar structure
provides multiple "guide stars" in any desired configuration. At the
Dunn Solar Telescope (DST) we implemented a dedicated MCAO bench with
the goal of developing wellcharacterized, operational MCAO. The MCAO
system uses two deformable mirrors conjugated to the telescope entrance
pupil and a layer in the upper atmosphere, respectively. The high
altitude deformable mirror can be placed at conjugates ranging from
2km to 10km altitude. We have successfully and stably locked the MCAO
system on solar granulation and demonstrated the MCAO system's ability
to significantly extend the corrected field of view. We present results
derived from analysis of imagery taken simultaneously with conventional
AO and MCAO. We also present first results from solar Ground Layer AO
(GLAO) experiments.
Title: Analysis of adaptive optics control for the Advanced Technology
Solar Telescope
Authors: Marino, Jose; Wöger, Friedrich; Rimmele, Thomas
Bibcode: 2010SPIE.7736E..3EM
Altcode: 2010SPIE.7736E.114M
Large aperture solar telescopes, such as the 4 meter aperture Advanced
Technology Solar Telescope (ATST), depend on high order adaptive optics
(AO) to achieve the telescope's diffraction limited resolution. The
AO system not only corrects incoming distortions introduced by
atmospheric turbulence, its performance also plays a critical
role for the operation of other subsystems and affects the results
obtained by downstream scientific instrumentation. For this reason,
robust and optimal operation of the AO system is vital to maximize
the scientific output of ATST. In order to optimize performance, we
evaluate different strategies to obtain the control matrix of the AO
system. The dependency of AO performance on various control parameters,
such as different system calibration and reconstruction schemes, is
analyzed using an AO simulation tool. The AO simulation tool provides
a realistic solar AO system simulation and allows a detailed evaluation
of the performance achieved by different calibration and reconstruction
methods. The results of this study will guide the optimization of the
AO system during design and operations.
Title: Nasmyth focus instrumentation of the New Solar Telescope at
Big Bear Solar Observatory
Authors: Cao, Wenda; Gorceix, Nicolas; Coulter, Roy; Wöger, Friedrich;
Ahn, Kwangsu; Shumko, Sergiy; Varsik, John; Coulter, Aaron; Goode,
Philip R.
Bibcode: 2010SPIE.7735E..5VC
Altcode: 2010SPIE.7735E.194C
The largest solar telescope, the 1.6-m New Solar Telescope (NST) has
been installed and is being commissioned at Big Bear Solar Observatory
(BBSO). It has an off-axis Gregorian configuration with a focal ratio
of F/52. Early in 2009, first light scientific observations were
successfully made at the Nasmyth focus, which is located on the east
side of the telescope structure. As the first available scientific
instruments for routine observation, Nasmyth focus instrumentation
(NFI) consists of several filtergraphs offering high spatial resolution
photometry in G-band 430 nm, Ha 656 nm, TiO 706 nm, and covering the
near infrared 1083 nm, 1.6 μm, and 2.2 μm. With the assistance of
a local correlation tracker system, diffraction limited images were
obtained frequently over a field-of-view of 70 by 70 after processed
using a post-facto speckle reconstruction algorithm. These data sets
not only serve for scientific analysis with an unprecedented spatial
resolution, but also provide engineering feedback to the NST operation,
maintenance and optimization. This paper reports on the design and the
implementation of NFI in detail. First light scientific observations
are presented and discussed.
Title: The ATST visible broadband imager: a case study for real-time
image reconstruction and optimal data handling
Authors: Wöger, Friedrich; Uitenbroek, Han; Tritschler, Alexandra;
McBride, William; Elmore, David; Rimmele, Thomas; Cowan, Bruce;
Wampler, Steve; Goodrich, Bret
Bibcode: 2010SPIE.7735E..21W
Altcode: 2010SPIE.7735E..69W
At future telescopes, adaptive optics systems will play a role beyond
the correction of Earth's atmosphere. These systems are capable of
delivering information that is useful for instrumentation, e.g. if
reconstruction algorithms are employed to increase the spatial
resolution of the scientific data. For the 4m aperture Advanced
Technology Solar Telescope (ATST), a new generation of state-of-the-art
instrumentation is developed that will deliver observations of the solar
surface at unsurpassed high spatial resolution. The planned Visual
Broadband Imager (VBI) is one of those instruments. It will be able
to record images at an extremely high rate and compute reconstructed
images close to the telescope's theoretical diffraction limit using
a speckle interferometry algorithm in near real-time. This algorithm
has been refined to take data delivered by the adaptive optics system
into account during reconstruction. The acquisition and reconstruction
process requires the use of a high-speed data handling infrastructure
to retrieve the necessary data from both adaptive optics system and
instrument cameras. We present the current design of this infrastructure
for the ATST together with a feasibility analysis of the underlying
algorithms.
Title: A chromospheric dark-cored fibril in Ca II IR spectra
Authors: Beck, C.; Tritschler, A.; Wöger, F.
Bibcode: 2010AN....331..574B
Altcode:
We investigate the thermodynamical and magnetic properties of a
``dark-cored" fibril seen in the chromospheric Ca II IR line at 854.2
nm to determine the physical process behind its appearance. We analyse
a time series of spectropolarimetric observations obtained in the Ca
II IR line at 854.2 nm and the photospheric Fe I line at 630.25 nm. We
simultaneously invert the spectra in both wavelength ranges with the
SIR code to obtain the temperature and velocity stratification with
height in the solar atmosphere and the magnetic field properties in the
photosphere. The structure can be clearly traced in the line-of-sight
(LOS) velocity and the temperature maps. It connects from a small
pore with kG fields to a region with lower field strength. The flow
velocity and the temperature indicate that the height of the structure
increases with increasing distance from the inner footpoint. The Stokes
V signal of 854.2 nm shows a Doppler-shifted polarization signal with
the same displacement as in the intensity profile, indicating that the
supersonic flow seen in the LOS velocity is located within magnetized
plasma. We conclude that the chromospheric dark-cored fibril traces
a siphon flow along magnetic field lines, driven by the gas pressure
difference caused by the higher magnetic field strength at the inner
footpoint. We suggest that fast flows guided by the magnetic field lead
to the appearance of ``dark-cored" fibrils in intensity images. Although
the observations included the determination of the polarization signal
in the chromospheric Ca II IR line, the signal could not be analysed
quantitatively due to the low S/N. Chromospheric polarimetry will thus
require telescopes of larger aperture able to collect a sufficient
number of photons for a reliable determination of polarization in deep
and only weakly polarized spectral lines.
Title: Fast computation of 2D transfer functions from adaptive
optics data
Authors: Wöger, F.
Bibcode: 2010AN....331..662W
Altcode:
The use of atmospheric transfer functions is common in image
reconstruction techniques such as speckle interferometry to calibrate
the Fourier amplitudes of the reconstructed images. Thus, an accurate
model is needed to ensure proper photometry in the reconstruction. The
situation complicates when adaptive optics (AO) are used during data
acquisition. I propose a novel technique to derive two-dimensional
transfer functions from data collected using AO simultaneously with
the observations. The technique is capable to compute the relevant
transfer functions within a short time for the prevailing atmospheric
conditions and AO performance during data acquisition.
Title: Optical transfer functions derived from solar adaptive optics
system data
Authors: Wöger, Friedrich
Bibcode: 2010ApOpt..49.1818W
Altcode:
Adaptive optics (AO) systems installed at large ground-based telescopes
partially correct Earth's atmosphere, making post facto image
reconstruction techniques necessary to produce diffraction-limited
observations. To achieve accurate photometry in the reconstructed
images, some post facto techniques require knowledge of transfer
functions that describe the optical system. I present a new, fast
method for the estimation of the long-exposure and speckle transfer
functions from data gathered by a solar AO system simultaneously with
the observations. The results of the presented method are tested with
extensive analytical models, demonstrating that the estimation is robust
for situations where the AO system is performing with Strehl ratios
larger than 45%. Application to observations of solar granulation
produces reconstructed images that are photometrically in agreement
with earlier results.
Title: Solar Multi-Conjugate Adaptive Optics at the Dunn Solar
Telescope
Authors: Rimmele, T.; Hegwer, S.; Marino, J.; Richards, K.; Schmidt,
D.; Waldmann, T.; Woeger, F.
Bibcode: 2010aoel.confE8002R
Altcode:
Solar observations are performed over an extended field of view and
the isoplanatic patch over which conventional adaptive optics (AO)
provides diffraction limited resolution is a severe limitation. The
development of multi-conjugate adaptive optics (MCAO) for the next
generation large aperture solar telescopes is thus a top priority. The
Sun is an ideal object for the development of MCAO since solar structure
provides ,,multiple guide stars” in any desired configuration. At
the Dunn Solar Telescope (DST) we implemented a dedicated MCAO bench
with the goal of developing well-characterized, operational MCAO. The
MCAO system uses 2 deformable mirrors conjugated to the telescope
entrance pupil and a layer in the upper atmosphere, respectively. DM2
can be placed at conjugates ranging from 2km to 10km altitude. We have
successfully and stably locked the MCAO system on artificial objects
(slides), for which turbulence screens are generated directly in front
of the DMs, as well as solar structure. We present preliminary results
and discuss future plans.
Title: Recovering the line-of-sight magnetic field in the chromosphere
from Ca II IR spectra
Authors: Wöger, F.; Wedemeyer-Böhm, S.; Uitenbroek, H.; Rimmele, T.
Bibcode: 2010MmSAI..81..598W
Altcode: 2009arXiv0912.3467W
We propose a method to derive the line-of-sight magnetic flux density
from measurements in the chromospheric Ca II IR line at 854.2 nm. The
method combines two well-understood techniques, the center-of-gravity
and bisector method, in a single hybrid technique. The technique
is tested with magneto-static simulations of a flux tube. We apply
the method to observations with the Interferometric Bidimensional
Spectrometer (IBIS) installed at the Dunn Solar Telescope of the NSO/SP
to investigate the morphology of the lower chromosphere, with focus on
the chromospheric counterparts to the underlying photospheric magnetic
flux elements.
Title: Morphology and Dynamics of Photospheric and Chromospheric
Magnetic Fields
Authors: Wöger, F.; Wedemeyer-Böhm, S.; Rimmele, T.
Bibcode: 2009ASPC..415..319W
Altcode: 2009arXiv0912.3285W
We use joint observations obtained with the Hinode space observatory
and the Interferometric Bidimensional Spectrometer (IBIS) installed
at the DST of the NSO/SP to investigate the morphology and dynamics
of (a) non-magnetic and (b) magnetic regions in the fluctosphere. In
inter-network regions with no significant magnetic flux contributions
above the detection limit of IBIS, we find intensity structures with
similar characteristics as those seen in numerical simulations by
Wedemeyer-Böhm et al. (2008) The magnetic flux elements in the network
are stable and seem to resemble the spatially extended counterparts
to the underlying photospheric magnetic elements. We will explain
some of the difficulties in deriving the magnetic field vector from
observations of the fluctosphere.
Title: Service-Mode Observations for Ground-Based Solar Physics
Authors: Reardon, K. P.; Rimmele, T.; Tritschler, A.; Cauzzi, G.;
Wöger, F.; Uitenbroek, H.; Tsuneta, S.; Berger, T.
Bibcode: 2009ASPC..415..332R
Altcode: 2009arXiv0909.1522R
There are significant advantages in combining Hinode observations
with ground-based instruments that can observe additional spectral
diagnostics at higher data rates and with greater flexibility. However,
ground-based observations, because of the random effects of weather
and seeing as well as the complexities data analysis due to changing
instrumental configurations, have traditionally been less efficient
than satellite observations in producing useful datasets. Future large
ground-based telescopes will need to find new ways to optimize both
their operational efficiency and scientific output. We have begun
experimenting with service-mode or queue-mode observations at the Dunn
Solar Telescope using the Interferometric Bidimensional Spectrometer
(IBIS) as part of joint Hinode campaigns. We describe our experiences
and the advantag es of such an observing mode for solar physics.
Title: Morphology and Dynamics of the Low Solar Chromosphere
Authors: Wöger, F.; Wedemeyer-Böhm, S.; Uitenbroek, H.; Rimmele,
T. R.
Bibcode: 2009ApJ...706..148W
Altcode: 2009arXiv0910.1381W
The Interferometric Bidimensional Spectrometer (IBIS) installed at
the Dunn Solar Telescope of the NSO/SP is used to investigate the
morphology and dynamics of the lower chromosphere and the virtually
non-magnetic fluctosphere below. The study addresses in particular the
structure of magnetic elements that extend into these layers. We choose
different quiet-Sun regions inside and outside the coronal holes. In
inter-network regions with no significant magnetic flux contributions
above the detection limit of IBIS, we find intensity structures with the
characteristics of a shock wave pattern. The magnetic flux elements in
the network are long lived and seem to resemble the spatially extended
counterparts to the underlying photospheric magnetic elements. We
suggest a modification to common methods to derive the line-of-sight
magnetic field strength and explain some of the difficulties in deriving
the magnetic field vector from observations of the fluctosphere.
Title: Effect of anisoplanatism on the measurement accuracy of an
extended-source Hartmann-Shack wavefront sensor
Authors: Woeger, Friedrich; Rimmele, Thomas
Bibcode: 2009ApOpt..48A..35W
Altcode:
We analyze the effect of anisoplanatic atmospheric turbulence on the
measurement accuracy of an extended-source Hartmann-Shack wavefront
sensor (HSWFS). We have numerically simulated an extended-source
HSWFS, using a scenery of the solar surface that is imaged through
anisoplanatic atmospheric turbulence and imaging optics. Solar
extended-source HSWFSs often use cross-correlation algorithms in
combination with subpixel shift finding algorithms to estimate the
wavefront gradient, two of which were tested for their effect on
the measurement accuracy. We find that the measurement error of an
extended-source HSWFS is governed mainly by the optical geometry
of the HSWFS, employed subpixel finding algorithm, and phase
anisoplanatism. Our results show that effects of scintillation
anisoplanatism are negligible when cross-correlation algorithms
are used.
Title: Speckle interferometry with adaptive optics corrected
solar data
Authors: Wöger, F.; von der Lühe, O.; Reardon, K.
Bibcode: 2008A&A...488..375W
Altcode:
Context: Adaptive optics systems are used on several advanced solar
telescopes to enhance the spatial resolution of the recorded data. In
all cases, the correction remains only partial, requiring post-facto
image reconstruction techniques such as speckle interferometry
to achieve consistent, near-diffraction limited resolution.
Aims: This study investigates the reconstruction properties of
the Kiepenheuer-Institut Speckle Interferometry Package (KISIP)
code, with focus on its phase reconstruction capabilities and
photometric accuracy. In addition, we analyze its suitability for
real-time reconstruction.
Methods: We evaluate the KISIP
program with respect to its scalability and the convergence of
the implemented algorithms with dependence on several parameters,
such as atmospheric conditions. To test the photometric accuracy of
the final reconstruction, comparisons are made between simultaneous
observations of the Sun using the ground-based Dunn Solar Telescope and
the space-based Hinode/SOT telescope.
Results: The analysis shows
that near real-time image reconstruction with high photometric accuracy
of ground-based solar observations is possible, even for observations in
which an adaptive optics system was utilized to obtain the speckle data.
Title: Wavefront measurement error in a Hartmann-Shack-type wavefront
sensor due to field anisoplanatism
Authors: Wöger, Friedrich; Rimmele, Thomas
Bibcode: 2008SPIE.7015E..4XW
Altcode: 2008SPIE.7015E.133W
We investigate the effect of atmospheric phase and scintillation
anisoplanatism on the measurement of the local gradient of the wavefront
using a Hartmann-Shack type wavefront sensor. This is accomplished
by simulation of the imaging process, starting with 100 synthetic,
anisoplanatic phase and scintillation screens that were computed for
several viewing angles and that correspond to Fried parameters of 7
and 12 cm. The screens are calculated using the approximated turbulence
profile at the site selected for the ATST, Haleakala on Maui, Hawaii,
USA. Phase aberrations are propagated through the wavefront sensor,
considering each viewing angle in each subaperture (of adjustable
size) separately. The point spread functions (PSF) are calculated for
the viewing directions as well as specified (and adjustable) pixel
scale in the sensor camera. Subsequently, these PSFs are convolved
with a typical wavefront sensor lock structure of solar AO systems,
an image of solar granulation. The cross-correlation peak of the
thus created anisoplanatic subimages is finally used to find the
local gradients of the wavefront. We find that phase anisoplanatism
contributes significantly to the measurement error of a Hartmann-Shack
type wavefront sensor, whereas we cannot detect a notable increase
thereof from scintillation anisoplanatism in the subaperture when
using a cross-correlating algorithm to find the gradient of the
incident wavefront.
Title: KISIP: a software package for speckle interferometry of
adaptive optics corrected solar data
Authors: Wöger, Friedrich; von der Lühe, Oskar, II
Bibcode: 2008SPIE.7019E..1EW
Altcode: 2008SPIE.7019E..46W
We present a speckle interferometry code for solar data taken with the
help of an adaptive optics (AO) system. As any AO correction is only
partial there is a need to use post-facto reconstruction algorithms to
achieve the diffraction limit of the telescope over a large field of
view most of the observational time. However, data rates of current
and future solar telescopes are ever increasing with camera chip
sizes. In order to overcome the tedious and expensive data handling, we
investigate the possibility to use the presented speckle reconstruction
program in a real-time application at telescope sites themselves. The
program features Fourier phase reconstruction algorithms using either
an extended Knox-Thompson or a triple correlation scheme. The Fourier
amplitude reconstruction has been adjusted for use with models that take
the correction of an AO system into account. The code has been written
in the C programming language and optimized for parallel processing
in a multi-processor environment. We analyze the scalability of the
code to find possible bottlenecks. Finally, the phase reconstruction
accuracy is validated by comparison of reconstructed data with satellite
data. We conclude that the presented code is capable to run in future
real-time reconstruction applications at solar telescopes if care is
taken that the multi-processor environments have low latencies between
the processing nodes.
Title: Solar Chromospheric Dynamics: Onwards and Upwards
Authors: Cauzzi, G.; Reardon, K.; Rimmele, T.; Rutten, R.; Tritschler,
A.; Uitenbroek, H.; Woeger, F.
Bibcode: 2008AGUSMSP41B..03C
Altcode:
We present a study of chromospheric dynamics and its relation with the
driving photospheric magneto-convection in a variety of solar targets,
from quiet Sun to more active regions. To this end high resolution
observations were obtained in CaII 854.2 nm, Hα, and photospheric
FeI lines with the Interferometric BIdimensional Spectrometer (IBIS)
installed at the Dunn Solar Telescope of the NSO. The availability of
full spectroscopic information on extended fields of view allows us
to derive a comprehensive view of the intrinsically 3-D chromospheric
scene. A coherent picture is emerging that involves the propagation
and dissipation of photospheric acoustic waves into the chromospheric
layers, but selected and guided by the local and highly variable
magnetic topology. In particular, ubiquitous fibrilar structures,
apparently originating from even the smallest magnetic elements,
appear an integral part of the dynamic chromosphere.
Title: WHI Targeted Campaigns on Coronal Holes and Quiet Sun: High
Resolution Observations of the Lower Atmosphere With IBIS
Authors: Cauzzi, G.; Reardon, K. P.; Rimmele, T.; Tritschler, A.;
Uitebroek, H.; Woeger, F.; Deforest, C.; McIntosh, S.
Bibcode: 2008AGUSMSH51A..02C
Altcode:
The Interferometric BIdimensional Spectrometer (IBIS) is a dual
Fabry-Perot instrument installed at the Dunn Solar Telescope that allows
two-dimensional spectroscopic observations in a variety of spectral
lines. The IBIS/DST will participate in the WHI targeted campaigns
on coronal holes (April 3-9) and quiet Sun dynamics (April 10-16)
performing simultaneous high-resolution observations of the dynamics of
the photosphere and chromosphere in the coordinated targets. The aim is
to obtain insights on the role of the lower atmosphere's dynamics and
energetics into the structuring of the coronal plasma and, possibly,
into the origin of the solar wind. In this paper we will present the
observations obtained as well as first results, and attempt to relate
them with recent work performed on quiet Sun chromospheric dynamics.
Title: Simulations of Atmospheric Turbulence and Instrumentation on
Solar Observations
Authors: Weber, M.; Tritschler, A.; Woeger, F.
Bibcode: 2008AGUSMSP51B..08W
Altcode:
We investigate the influence of atmospheric turbulence and
instrumentation on solar observations. The focus of this study
is the determination of the amount of bias introduced in velocity
measurements by these effects. The magnetically insensitive Fe I
557.6 nm line is synthesized using three-dimensional simulations of
solar magneto-convection as an input model for a radiation transfer
code. The synthesized spectra are then subjected to different
atmospheric conditions characterized by the Fried parameters r0 = 7,
10, and 15 cm. To simulate realistic observations at NSO's Dunn solar
telescope (DST), we mimic the influence of a 0.76 m aperture telescope,
a high-order adaptive optics (AO) system and a tunable filtergraph on
the atmospherically distorted spectra.
Title: Small-scale structure and dynamics of the lower solar
atmosphere
Authors: Wedemeyer-Böhm, Sven; Wöger, Friedrich
Bibcode: 2008IAUS..247...66W
Altcode: 2007IAUS..247...66W; 2007arXiv0710.4776W
The chromosphere of the quiet Sun is a highly intermittent and dynamic
phenomenon. Three-dimensional radiation (magneto-)hydrodynamic
simulations exhibit a mesh-like pattern of hot shock fronts and
cool expanding post-shock regions in the sub-canopy part of the
inter-network. This domain might be called “fluctosphere”. The
pattern is produced by propagating shock waves, which are excited
at the top of the convection zone and in the photospheric overshoot
layer. New high-resolution observations reveal a ubiquitous small-scale
pattern of bright structures and dark regions in-between. Although it
qualitatively resembles the picture seen in models, more observations
e.g. with the future ALMA are needed for thorough comparisons
with present and future models. Quantitative comparisons demand
for synthetic intensity maps and spectra for the three-dimensional
(magneto-)hydrodynamic simulations. The necessary radiative transfer
calculations, which have to take into account deviations from local
thermodynamic equilibrium, are computationally very involved so
that no reliable results have been produced so far. Until this task
becomes feasible, we have to rely on careful qualitative comparisons
of simulations and observations. Here we discuss what effects have to
be considered for such a comparison. Nevertheless we are now on the
verge of assembling a comprehensive picture of the solar chromosphere
in inter-network regions as dynamic interplay of shock waves and
structuring and guiding magnetic fields.
Title: The solar chromosphere at high resolution with IBIS. I. New
insights from the Ca II 854.2 nm line
Authors: Cauzzi, G.; Reardon, K. P.; Uitenbroek, H.; Cavallini, F.;
Falchi, A.; Falciani, R.; Janssen, K.; Rimmele, T.; Vecchio, A.;
Wöger, F.
Bibcode: 2008A&A...480..515C
Altcode: 2007arXiv0709.2417C
Context: The chromosphere remains a poorly understood part of the solar
atmosphere, as current modeling and observing capabilities are still
ill-suited to investigating its fully 3-dimensional nature in depth. In
particular, chromospheric observations that can preserve high spatial
and temporal resolution while providing spectral information over
extended fields of view are still very scarce.
Aims: In this
paper, we seek to establish the suitability of imaging spectroscopy
performed in the Ca II 854.2 nm line as a means of investigating
the solar chromosphere at high resolution.
Methods: We utilize
monochromatic images obtained with the Interferometric BIdimensional
Spectrometer (IBIS) at multiple wavelengths within the Ca II 854.2 nm
line and over several quiet areas. We analyze both the morphological
properties derived from narrow-band monochromatic images and the
average spectral properties of distinct solar features such as network
points, internetwork areas, and fibrils.
Results: The spectral
properties derived over quiet-Sun targets are in full agreement with
earlier results obtained with fixed-slit spectrographic observations,
highlighting the reliability of the spectral information obtained
with IBIS. Furthermore, the very narrowband IBIS imaging reveals very
clearly the dual nature of the Ca II 854.2 nm line. Its outer wings
gradually sample the solar photosphere, while the core is a purely
chromospheric indicator. The latter displays a wealth of fine structures
including bright points akin to the Ca II H{2V} and K{2V} grains, and
as fibrils originating from even the smallest magnetic elements. The
fibrils occupy a large fraction of the observed field of view, even
in the quiet regions, and clearly outline atmospheric volumes with
different dynamical properties, strongly dependent on the local magnetic
topology. This highlights how 1D models stratified along the vertical
direction can provide only a very limited representation of the actual
chromospheric physics.
Conclusions: Imaging spectroscopy in the
Ca II 854.2 nm line currently represents one of the best observational
tools for investigating the highly structured and highly dynamical
chromospheric environment. A high-performance instrument such as IBIS
is crucial in achieving the necessary spectral purity and stability,
spatial resolution, and temporal cadence. Two movies are only
available in electronic form at http://www.aanda.org
Title: Solar Multi-Conjugate Adaptive Optics at the Dunn Solar
Telescope
Authors: Rimmele, T.; Hegwer, S.; Richards, K.; Woeger, F.
Bibcode: 2008amos.confE..18R
Altcode:
Solar adaptive optics has become an indispensable tool at ground
based solar telescopes. Driven by the quest for ever higher spatial
resolution observations of the Sun solar adaptive optics are now
operated routinely at major ground based solar telescopes. The current
high-resolution solar telescopes, such as the Dunn Solar Telescope
(DST), are in the one-meter class and utilize AO for >95 % of
the observing time to achieve the diffraction limit at visible and
NIR wavelengths. Solar AO [1,2] has revitalized ground-based solar
astronomy at existing telescopes. The development of high-order solar
AO that is capable of delivering high Strehl in the visible will
be absolutely essential for next generation solar telescopes, such
as the 4m aperture Advanced Technology Solar Telescope (ATST), which
undoubtedly will revolutionize solar astronomy [3]. Solar observations
are performed over an extended field of view. The limited size of
the isoplanatic patch, over which conventional adaptive optics (AO)
provides diffraction limited resolution is a severe limitation. Solar
science would benefit greatly from AO correction over large field of
views. A single sunspot typically has a size of about 30 arcsec; large
active regions often cover a field of 2-3 arcmin. Figure 1 shows an
image of solar granulation and embedded magnetic g-band bright points
observed near the limb of the sun. The field of view is approximately
120"x 80". This diffraction limited image was recorded at the Dunn
Solar Telescope with high order adaptive optics and post-processed
using speckle interferometry. Post-processing is required to achieve the
uniform, diffraction limited imaging over such an extended FOV. However,
speckle interferometry as well as other post facto restoration methods
typically rely on short exposure imaging, which in most cases can not be
deployed when quantitative spectroscopy and polarimetry is performed,
i.e., long exposures are required. Multi-conjugate adaptive optics
(MCAO) is a technique that provides real-time diffraction limited
imaging over an extended FOV [4]. The development of MCAO for existing
solar telescopes and, in particular, for the next generation large
aperture solar telescopes is thus a top priority. The Sun is an ideal
object for the development of MCAO since solar structure provides
"multiple guide stars" in any desired configuration. It is therefore
not surprising that the first successful on-the-sky MCAO experiments
were performed at the Dunn Solar Telescope and at a solar telescope
on the Canary Islands. However, further development is needed before
operational solar MCAO can be implemented at future large aperture
solar telescopes such as the ATST on Haleakala [5]. MCAO development
must progress beyond these initial proof-of-concept experiments and
should include laboratory experiments and on-sky demonstrations under
controlled or well characterized conditions as well as quantitative
performance analysis and comparison to model predictions. At the DST we
recently implemented a dedicated MCAO bench with the goal of developing
well-characterized, operational MCAO. The MCAO system uses 2 deformable
mirrors conjugated to the telescope entrance pupil and a layer in the
upper atmosphere, respectively. DM2 can be placed at conjugates ranging
from 2 km to 10 km altitude. For our initial experiments we have used
a staged approach in which the 97 actuator, 76 subaperture correlating
Shack-Hartmann solar adaptive optics system normally operated at the DST
is followed by the second DM and the tomographic wavefront sensor, which
uses three "solar guide stars". We use modal reconstruction algorithms
for both DMs. We have successfully and stably locked the MCAO system on
artificial objects (slides), for which 1 The National Solar Observatory
is operated by the Association of Universities for Research in Astronomy
under a cooperative agreement with the National Science Foundation,
for the benefit of the astronomical community turbulence screens are
generated directly in front of the DMs, as well as solar structure. We
varied the height of the upper conjugate between 2 km and 7 km. We
recorded strictly simultaneous images after the pupil DM and after
the upper layer DM. Comparing these images allows us to evaluate the
performance of the MCAO stage and directly compare to the conventional
AO. In addition we recorded wavefront sensor telemetry data for closed
and open loop. We present preliminary results and discuss future plans.
Title: Field dependent amplitude calibration of adaptive optics
supported solar speckle imaging
Authors: Wöger, Friedrich; von der Lühe, Oskar
Bibcode: 2007ApOpt..46.8015W
Altcode:
Adaptive optics supported solar speckle imaging requires the calibration
of the source's Fourier amplitudes with the transfer function of
atmosphere and optics. We present analytical models for the relevant
transfer functions of an adaptive optics systems. The models include
the effect of an arbitrary correction as well as anisoplanatism. The
proposed models have been compared with observational data using
measurements of α-Orionis and of the solar surface delivering both
a direct and indirect method (using the spectral ratio technique)
for validation. We find that measurements and model agree to a
satisfactory degree.
Title: High-resolution observations of the solar photosphere and
chromosphere
Authors: Wöger, Friedrich
Bibcode: 2007PhDT.........6W
Altcode:
Observations of the sun are almost always impaired by the turbulent
motion of air in Earth's atmosphere. The turbulence would limit the
theoretical resolution of modern large telescopes to that of amateur
telescopes without additional tools. Today however, high-resolution data
of the Sun are necessary to invesitgate its small-scale structure. This
structure is likely to be connected to the radially outward increasing
temparature distribution of the solar atmosphere. An introduction
into further details of this topic that has also been the motivation for
this work is presented in Chapt. 1. A theory of atmospheric turbulence
that builds the basis for several results of this work is described
in Chapt. 2. Here, two modern tools to enhance the resolution of
groundbased observations are reviewed, on the one hand adaptive optics
(AO) systems and on the other hand speckle interferometry. Until
recently, these two techniques were only used separately. In Chapt. 3
the necessary modifications for analytical models of transfer functions
are developed that include the changes made by an AO system to the
incoming wave front, thus making a combination of AO systems and speckle
interferometry possible. The models were compared to measured data
using different techniques, and a good agreement was found. In order
to apply speckle interferometry to the observational data acquired for
this work, a computer program package was developed that can reduce vast
amount of data within a reasonable time in a parallel way (App. 1). Speckle interferometry needs very shortly exposed data in order to
compute a reconstruction. However, a part of the data observed for
this work had to be exposed rather long because of technical problems,
making the use of this reconstruction technique impossible. This
motivated the development of an algorithm to estimate instantaneous
point spread functions from speckle reconstructions. The point spread
functions permit the deconvolution of the long exposed data making
use of well known techniques. The algorithm is developed in Chapt. 4,
along with a presentation of an examination of usability. In
Chapt. 5 the observational data that were reduced using the algorithms
developed in the course of this work were analyzed. It was found that
bright points within the chromospheric network are correlated both
spatially and temporally to those in the photospheric network. The
phenomena appear to overlay almost vertically. The ratio of their
sizes is <R_{chrom. BP}/R_{phot. BP}> = 3.0 with a standard
deviation of 0.7. The analysis of life times of structures within the
chromosphere revealed that network and inter-network regions can be
separated more accurately using a life time rather than the commonly
used intensity criterium. The combination of high spectral and spatial
resolution within this dataset revealed the existance of an up to now
undetected pattern of granular size in the chromspheric inter-network
that evolves too rapidly (with time scales of approx. 53s) to be
reversed granulation. This finding supports recent models of the
non-magnetic solar chromosphere that could explain this pattern as
signature of propagating and interacting shock waves that are excited
in the photosphere as an acoustic phenomenon. This is supported by the
detailed investigation of the solar oscillations in the chromospheric
network and inter-network that shows that the main contributions to
the 3min oscillations in the chromosphere can be attributed to the
inter-network. The chromospheric network mainly contributes to 5min
oscillations, which are typical for the photosphere.
Title: Adaptive Optics at the Big Bear Solar Observatory: Instrument
Description and First Observations
Authors: Denker, Carsten; Tritschler, Alexandra; Rimmele, Thomas R.;
Richards, Kit; Hegwer, Steve L.; Wöger, Friedrich
Bibcode: 2007PASP..119..170D
Altcode:
In 2004 January, the Big Bear Solar Observatory (BBSO) was equipped with
a high-order adaptive optics (AO) system built in collaboration with
the National Solar Observatory (NSO) at Sacramento Peak. The hardware is
almost identical to the AO system operated at the NSO Dunn Solar Tower
(DST), incorporating a 97 actuator deformable mirror, a Shack-Hartmann
wave-front sensor with 76 subapertures, and an off-the-shelf digital
signal processor system. However, the BBSO optical design is quite
different. It had to be adapted to the 65 cm vacuum reflector and
the downstream postfocus instrumentation. In this paper, we describe
the optical design, demonstrate the AO performance, and use image
restoration techniques to illustrate the image quality that can be
achieved with the new AO system.
Title: Advances, challenges and limitations of speckle reconstruction
and deconvolution
Authors: Mikurda, K.; von der Lühe, O.; Wöger, F.; Schmidt, W.
Bibcode: 2007msfa.conf..131M
Altcode:
This paper presents the experiences with speckle imaging and
deconvolution techniques we have made during the last five years at the
Kiepenheuer-Institut für Sonnenphysik. We discuss our implementation of
the above techniques, their tests and application ranges. In addition,
we summarize our efforts in applying speckle techniques to the data
taken with the support of the adaptive optics.
Title: High Resolution Time Series of Narrowband Ca IIK Images in
the Chromosphere
Authors: Wöger, F.; Wedemeyer-Böhm, S.; Schmidt, W.; von der
Lühe, O.
Bibcode: 2006ASPC..354..284W
Altcode:
We have observed a region of quiet Sun near disk center with the Vacuum
Tower Telescope (VTT) of the Kiepenheuer-Institut für Sonnenphysik at
the Observatorio del Teide, Tenerife, Spain in April 2005 in several
wavelengths. Observations were made at the Ca II K line at 393.3 nm,
using a Lyot filter with a bandwidth of 30 ± FWHM, centered at the
K_{2v} emission peak; at the Hα line at 656.3 nm, using a Lyot filter
(25 ± FWHM) centered at line core, and in the G-band (430.5 nm),
using an interference filter (1 nm FWHM). We acquired a two-hour long
sequence of images at a cadence of ten seconds and a spatial resolution
of about 0.3 arcsec. We present our Ca observations of excellent spatial
resolution which show morphological structures in internetwork regions
similar in form, size and lifetime to those present in recent numerical
models of the solar chromosphere.
Title: Observation of a short-lived pattern in the solar chromosphere
Authors: Wöger, F.; Wedemeyer-Böhm, S.; Schmidt, W.; von der
Lühe, O.
Bibcode: 2006A&A...459L...9W
Altcode: 2006astro.ph..9382W
Aims.In this work we investigate the dynamic behavior of inter-network
regions of the solar chromosphere.
Methods: .We observed the
chromosphere of the quiet Sun using a narrow-band Lyot filter centered
at the Ca II K2v emission peak with a bandpass of 0.3 Å. We achieved
a spatial resolution of on average 0.7 arcsec at a cadence of 10 s.
Results: .In the inter-network we find a mesh-like pattern that
features bright grains at the vertices. The pattern has a typical
spatial scale of 1.95 arcsec and a mean evolution time scale of 53 s
with a standard deviation of 10 s. A comparison of our results with a
recent three-dimensional radiation hydrodynamical model implies that
the observed pattern is of chromospheric origin. The measured time
scales are not compatible with those of reversed granulation in the
photosphere although the appearance is similar. A direct comparison
between network and inter-network structure shows that their typical
time scales differ by at least a factor of two.
Conclusions:
.The existence of a rapidly evolving small-scale pattern in the
inter-network regions supports the picture of the lower chromosphere
as a highly dynamical and intermittent phenomenon.
Title: High Resolution Spectropolarimetry of Penumbral Formation
with IBIS
Authors: Reardon, Kevin; Casini, R.; Cavallini, F.; Tomczyk, S.;
Rouppe van der Voort, L.; Van Noort, M.; Woeger, F.; Socas Navarro,
H.; IBIS Team
Bibcode: 2006SPD....37.3503R
Altcode: 2006BAAS...38..260R
We present the results of first spectropolarimetric observations
made with the Interferometric Bidimensional Spectrometer (IBIS)
at the NSO/Dunn Solar Telescope. The use of narrowband imaging and
post-facto reconstruction techniques allows for observations close
to the diffraction limit of the vector magnetic field. We will show
observations of the the formation of an individual penumbral filament
around a small pore. We measure the magnetic field and velocity field
of the forming penumbral filament. The spectropolarimetric mode of
IBIS will be available to the community in the fall of 2006.
Title: Comparison of Methods for Fried Parameter Estimation
Authors: Wöger, Friedrich; Berkefeld, Thomas; Soltau, Dirk
Bibcode: 2003ANS...324R..22W
Altcode: 2003ANS...324..C03W
No abstract at ADS
Title: Solar Imaging with an Extended Knox-Thompson Technique
Authors: Mikurda, K.; von der Lühe, O.; Wöger, F.
Bibcode: 2003ANS...324..112M
Altcode: 2003ANS...324..P18M
No abstract at ADS
Title: Adaptive optics and multi-conjugate adaptive optics with
the VTT
Authors: Soltau, D.; Berkefeld, Th.; von der Lühe, O.; Wöger, F.;
Schelenz, Th.
Bibcode: 2002AN....323..236S
Altcode:
We are currently developing adaptive optics (AO) system with a
multi-conjugate extension for the German solar vacuum tower telescope
(VTT) at the Teide Observatory on Tenerife. Multi-conjugate adaptive
optics (MCAO) is a technique for increasing the field of view by
compensating atmospheric turbulence along several, adjacent lines
of sight. A conventional AO system compensates only a single line of
sight in the direction of the lock point of its wavefront sensor. At
larger field angles, the light from the source transverses higher
layers of turbulence which are not sampled by the conventional
system. Measurements at the VTT indicate that full compensation
is typically restricted to a field of about 10 arcsec in diameter
at visible wavelengths. An MCAO uses (at least) a second deformable
mirror close to the focal plane of the telescope to compensate a larger
field. The sun is a privileged target for an MCAO because the wavefront
errors at larger field angles are easily measured. We intend to extend
our existing AO system with a second deformable mirror and a second
wavefront sensor which enables us to extend the compensated field by
a factor of three in diameter. We present and discuss our concept.