Author name code: rimmele
ADS astronomy entries on 2022-09-14
author:"Rimmele, Thomas"
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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: Lessons Learned Regarding Software Tools Used During the 1st
DKIST Operations Commissioning Call for Proposals
Authors: Alexov, Anastasia; Tritschler, Alexandra; Rimmele, Thomas
Bibcode: 2022ASPC..532..583A
Altcode: 2022adass..30..583A
The National Science Foundation's (NSF) Daniel K. Inouye Solar
Telescope's (DKIST) first Operations Commissioning Call for Proposals
was released on May 15, 2020, and open through August 14, 2020. We
will present the software tools used during the proposing phase
focusing on: Amazon Web Services for the Proposal Tools Web Interface,
Atlassian's Jira Service Desk for the Help Desk and Confluence for
the Knowledgebase, as well as Google Forms for surveying Proposers,
and Slack for quick communication and troubleshooting amongst
team members. We will discuss what software services and tools
worked well for our purposed process and where improvements could be
made. Furthermore, we will present some software-related lessons learned
based on initial feedback from participants in the Proposal Call.
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: Adding multi-conjugate adaptive optics to the Daniel K. Inouye
Solar Telescope
Authors: Schmidt, Dirk; Beard, Andrew; Ferayorni, Andrew; Gregory,
Scott; Johnson, Luke; Marino, Jose; Rimmele, Lukas; Rimmele, Thomas
Bibcode: 2021SPIE11448E..0FS
Altcode:
The 4-meter Daniel K. Inouye Solar Telescope will be upgraded with
multi-conjugate adaptive optics. Two high-altitude deformable mirrors
shall be added, and a multi-directional wavefront sensor system
and a real-time control computer cluster will replace the existing
counterparts of the operational first-light, classical adaptive optics
system in a few years. Herein we give a brief overview of the system. We
present the current status of the project including the prototyping
for the wavefront sensor system and the real-time control system.
Title: The Daniel K Inouye Solar Telescope and the Multi-Messenger ERA
Authors: Rimmele, Thomas
Bibcode: 2021cosp...43E.946R
Altcode:
The largest solar telescope ever built is in its final phase of
integration and commissioning on Maui, in Hawaii, and is already
acquiring images of the solar surface at unprecedented spatial
resolution. This year marks the start of operations of the US National
Science Foundation's Daniel K Inouye Solar Telescope (DKIST), designed
to meet the needs of critical high resolution and high sensitivity
spectral and polarimetric observations of the Sun. As we enter the
new multi-messenger era for inner heliospheric research marked by
DKIST, Solar Orbiter, and the Parker Solar Probe, DKIST provides a
transformative open-access facility with five diverse co-operating
first-light instruments spanning visible and infrared wavelengths. A
number of frontier diagnostic windows are enabled by DKIST for the
study of the heliospheric solar boundary, in particular within the
chromosphere and corona. We here review and assess the capabilities
of DKIST, present its current status and available data, and discuss
how the solar community can best take advantage of DKIST for critical
coordinated science.
Title: Preparing for the DKIST operations commissioning phase science
operations specialists' perspective
Authors: Parraguez, Andres; Alexov, Anastasia; Tritschler, Alexandra;
Rimmele, Thomas; Diaz Alfaro, Manuel; Gilliam, Doug; Head, Hillary;
Morris, David; Wright-Garba, Nuria
Bibcode: 2020SPIE11449E..2JP
Altcode:
The National Science Foundation's (NSF) Daniel K. Inouye Solar
Telescope (DKIST) is located on the island of Maui, Hawai'i. The DKIST
is a 4-meter clear-aperture solar telescope nearing the end of its
construction phase in 2021. Following construction there will be a one
year Operations Commissioning Phase (OCP). The OCP allows for early
observing opportunities, while at the same time, fine-tuning systems
and procedures, in preparation for DKIST steadystate operations in
2022. During the OCP, the DKIST Science Operations Specialists (SOSs,
a.k.a. Telescope Operators) will execute validated solar observing
programs as instructed by Resident Scientists while coordinating
with maintenance and engineering activities. DKIST maintenance
and engineering tasks are performed by the technical operations
staff sharing time during daylight with science operations, which
is an entirely different scenario than for nighttime ground-based
observatories. Presented here is a summary of the year leading up to
the OCP from the perspective of the DKIST SOS group. We present the
training planned for the current SOS group and how this folds into the
DKIST's still ongoing Integration, Testing and Commissioning phase. We
are developing an efficient training program to reduce the overall
training time. We also discuss the tools which assist the current SOS
group in writing and generating shift schedules, procedures, checklists,
and workflows.
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: An Overview of DKIST Operations Commissioning and Tools
Authors: Alexov, A.; Tritschler, A.; Rimmele, T.; Marshall, H.;
Parraguez, A.
Bibcode: 2020ASPC..527..435A
Altcode: 2020adass..29..435A
The Daniel K. Inouye Solar Telescope (DKIST) is a 4-meter clear aperture
solar telescope nearing the end of its construction on the summit
of Haleakalā on the island of Maui, Hawai'i. It will be the largest
solar telescope in the world when completed in summer 2020. We present
a condensed overview of the DKIST Operations Commissioning Phase (OCP)
which will start after the completion of construction. This Operations
Commissioning phase will allow for a manageable transition from the
end of construction into steady-state operations over the course of
approximately one year. During this phase, science operations will
specifically integrate, test and streamline its procedures by exercising
through all steps of the DKIST's Science Operations Lifecycle. We
will also briefly introduce software tools that are or will be used
by Science Operations, Technical Operations and the DKIST Data Center.
Title: Status of the Daniel K. Inouye Solar Telescope
Authors: Rimmele, Thomas R.
Bibcode: 2019AAS...23422601R
Altcode:
The construction of the 4m Daniel K. Inouye Solar Telescope (DKIST) on
Haleakala, Maui is in its final phase. The construction of the facility
is 90% complete. Operations are scheduled to begin in 2020. DKIST
was designed to meet the needs of critical high resolution and high
sensitivity spectral and polarimetric observations of the sun. The
design allows DKIST to operate as a coronagraph at infrared wavelengths
where the sky background is low and bright coronal emission lines
are available. 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. Five first light instruments
will be available at the start of operations. The data from these
instruments will be distributed to the community via the NSO/DKIST
data center located in Boulder. We will discuss the project status.
Title: From Clear to DKIST: advancing solar MCAO from 1.6 to 4 meters
Authors: Schmidt, Dirk; Marino, Jose; Gorceix, Nicolas; Rimmele,
Thomas; Johnson, Luke; Berkefeld, Thomas; Goode, Philip
Bibcode: 2018SPIE10703E..26S
Altcode:
The MCAO pathfinder Clear on the 1.6-meter Goode Solar Telescope
has been enabling us to advance solar MCAO from early conceptual
demonstrations to science grade wide-field image correction. We report
on recent improvements to the control loop and we comment on issues
such as the co-aligning of wavefront sensors and deformable mirrors and
the sensitivity of wavefront sensor gains. Further, we comment on the
challenges to wavefront sensing and the control system architecture
faced when scaling up to a 4-meter aperture. Finally, we present an
early concept of the future MCAO upgrade for the Daniel K. Inouye
Solar Telescope.
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: Wavefront sensing and adaptive optics for solar prominences
Authors: Schmidt, Dirk; Rimmele, Thomas; Gorceix, Nicolas
Bibcode: 2018SPIE10703E..5WS
Altcode:
We explore the feasibility of adaptive optics for observations
of prominences off the solar limb. We installed a wavefront sensor
prototype on the GST at the Big Bear Solar Observatory. This sensor is
used to conduct open and closed loop experiments to characterize the
limitations of this application following up on first demonstrations
at the DST. The sensor will enable us to optimize parameters and
algorithms for a potential future implementation on NSF's Daniel
K. Inouye Solar Telescope. Unlike the granular structure of the solar
photosphere that has served wavefront sensors in solar telescopes for
decades with useful reference structures, prominences are much more
challenging to use: they are faint and their fine structure is barely
visible at the short exposures needed for an AO wavefront sensor.
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: 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: 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: 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: Progress with multi-conjugate adaptive optics at the Big Bear
Solar Observatory
Authors: Schmidt, Dirk; Gorceix, Nicolas; Marino, Jose; Zhang, Xianyu;
Berkefeld, Thomas; Rimmele, Thomas R.; Goode, Philip R.
Bibcode: 2016SPD....47.0813S
Altcode:
The MCAO system at BBSO is the pathfinder system for a future system
at the 4-meter DKIST. It deploys three DMs, one in the pupil and two in
higher altitudes. The design allows to move the latter independently to
adapt to the turbulence profile within about 2-9 km.The optical path has
been improved in 2015, and has shown satisfying solar images. The MCAO
loop was able to improve the wavefront error across the field slightly
compared to classical AO.We will report on the latest improvements,
on-Sun results and motivate the design of the system.
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: Daniel K. Inouye Solar Telescope Science Operations
Authors: Tritschler, Alexandra; Rimmele, Thomas R.; Berukoff, Steven
Bibcode: 2016SPD....47.0406T
Altcode:
The Daniel K. Inouye Solar Telescope (DKIST) is a versatile high
resolution ground-based solar telescope designed to explore the
dynamic Sun and its magnetism throughout the solar atmosphere from
the photosphere to the faint corona. The DKIST is currently under
construction on Haleakala, Maui, Hawai'i, and expected to commence
with science operations in 2019. In this contribution we provide an
overview of the high-level science operations concepts from proposal
preparation and submission to the flexible and dynamic planning and
execution of observations.
Title: Multi-conjugate Adaptive Optics at Big Bear Solar Observatory
Authors: Schmidt, Dirk; Gorceix, Nicolas; Zhang, Xianyu; Marino,
Jose; Goode, Phil; Rimmele, Thomas; Goode, Phil
Bibcode: 2015aoel.confE..33S
Altcode:
No abstract at ADS
Title: Next-generation solar data and data services from the Daniel
K. Inouye Solar Telescope
Authors: Berukoff, S.; Reardon, K.; Rimmele, T.
Bibcode: 2015ASPC..495...91B
Altcode: 2015adass..24...91B
The Daniel K. Inouye Solar Telescope (DKIST), when completed, will
be the largest, most capable solar telescope in the world. Currently
under construction on the summit of Haleakala on Maui, the DKIST will
enable foundational insights into the physics of the Sun's photosphere,
chromosphere, and corona. Its suite of first-light instruments will
produce approximately 25TB of raw and processed data per day, with
bursts up to 50TB. These data rates will require a scalable, flexible
data and computing architecture that enables and promotes inquiry and
discovery. We describe the challenges faced by managing DKIST data
and provide an overview of the proposed data center architecture
and resources that will allow users to fully exploit this unique
world-class facility.
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: Performance Testing of an Off-Limb Solar Adaptive Optics System
Authors: Taylor, G. E.; Schmidt, D.; Marino, J.; Rimmele, T. R.;
McAteer, R. T. J.
Bibcode: 2015SoPh..290.1871T
Altcode: 2015arXiv150801826T; 2015SoPh..tmp...54T
Long-exposure spectro-polarimetry in the near-infrared is a preferred
method to measure the magnetic field and other physical properties of
solar prominences. In the past, it has been very difficult to observe
prominences in this way with sufficient spatial resolution to fully
understand their dynamical properties. Solar prominences contain
highly transient structures, visible only at small spatial scales;
hence they must be observed at sub-arcsecond resolution, with a high
temporal cadence. An adaptive optics (AO) system capable of directly
locking on to prominence structure away from the solar limb has the
potential to allow for diffraction-limited spectro-polarimetry of solar
prominences. We show the performance of the off-limb AO system and its
expected performance at the desired science wavelength Ca II 8542 Å.
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 DKIST Operations Lifecycle: From Proposal Preparation
to Completion
Authors: Tritschler, A.; Berukoff, S. J.; Rimmele, T. R.
Bibcode: 2014AGUFMSH41C4161T
Altcode:
The 4-m aperture Daniel Ken Inouye Solar Telescope (DKIST), formerly
known as the Advanced Technology Solar Telescope (ATST), will be the
largest ground-based solar telescope when construction is completed
in 2019. Community access to the facility and its high-resolution
optical and infrared instrumentation suite will be provided through a
proposal merit and approval process, optimizing DKIST for high-impact
scientific use and emphasizing a high operational efficiency of the
facility. In this presentation we provide a high-level overview of,
and guide through, the planned phases of the operations lifecycle
relevant to anyone wishing to make use of this facility. The lifecycle
is initiated by the preparation and submission of scientific proposals
by Principal Investigators, and concluded by the successful execution of
all observations relevant to an approved proposal, as well as storage
and management of acquired data and metadata.
Title: Next-generation Solar Data and Data Services from the Daniel
K. Inouye Solar Telescope
Authors: Berukoff, S. J.; Reardon, K.; Rimmele, T.
Bibcode: 2014AGUFMSH41C4162B
Altcode:
The Daniel K. Inouye Solar Telescope (DKIST), when completed in
2019, will be the largest, most capable, solar telescope in the
world. Currently under construction on the summit of Haleakalā on Maui,
the DKIST will enable foundational insights into the physics of the
Sun's photosphere, chromosphere, and corona. Its suite of first-light
instruments will produce approximately 25 TB of raw data per day,
with occasional bursts of 50TB per day. These high data rates will
require a scalable, flexible data and computing architecture that
enables and promotes scientific inquiry and discovery. We briefly
describe the DKIST data stream and then provide an overview of the
proposed data-center architecture and resources that will allow users
to fully exploit this world-class facility.
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: AO-308: the high-order adaptive optics system at Big Bear
Solar Observatory
Authors: Shumko, Sergey; Gorceix, Nicolas; Choi, Seonghwan; Kellerer,
Aglaé; Cao, Wenda; Goode, Philip R.; Abramenko, Volodymyr; Richards,
Kit; Rimmele, Thomas R.; Marino, Jose
Bibcode: 2014SPIE.9148E..35S
Altcode:
In this paper we present Big Bear Solar Observatory's (BBSO) newest
adaptive optics system - AO-308. AO-308 is a result of collaboration
between BBSO and National Solar Observatory (NSO). AO-308 uses a 357
actuators deformable mirror (DM) from Xinetics and its wave front sensor
(WFS) has 308 sub-apertures. The WFS uses a Phantom V7.3 camera which
runs at 2000 Hz with the region of interest of 416×400 pixels. AO-308
utilizes digital signal processors (DSPs) for image processing. AO-308
has been successfully used during the 2013 observing season. The system
can correct up to 310 modes providing diffraction limited images at
all wavelengths of interest.
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: 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: Optical design of the Big Bear Solar Observatory's
multi-conjugate adaptive optics system
Authors: Zhang, Xianyu; Gorceix, Nicolas; Schmidt, Dirk; Goode,
Philip R.; Cao, Wenda; Rimmele, Thomas R.; Coulter, Roy
Bibcode: 2014SPIE.9148E..50Z
Altcode:
A multi-conjugate adaptive optics (MCAO) system is being built for the
world's largest aperture 1.6m solar telescope, New Solar Telescope,
at the Big Bear Solar Observatory (BBSO). The BBSO MCAO system employs
three deformable mirrors to enlarge the corrected field of view. In
order to characterize the MCAO performance with different optical
configurations and DM conjugated altitudes, the BBSO MCAO setup also
needs to be flexible. In this paper, we present the optical design of
the BBSO MCAO system.
Title: The multi-conjugate adaptive optics system of the New Solar
Telescope at Big Bear Solar Observatory
Authors: Schmidt, Dirk; Gorceix, Nicolas; Zhang, Xianyu; Marino,
Jose; Coulter, Roy; Shumko, Sergey; Goode, Phil; Rimmele, Thomas;
Berkefeld, Thomas
Bibcode: 2014SPIE.9148E..2US
Altcode:
We report on the multi-conjugate adaptive optics (MCAO) system of
the New Solar Telescope (NST) at Big Bear Solar Observatory which
has been integrated in October 2013 and is now available for MCAO
experiments. The NST MCAO system features three deformable mirrors (DM),
and it is purposely flexible in order to offer a valuable facility for
development of solar MCAO. Two of the deformable mirrors are dedicated
to compensation of field dependent aberrations due to high-altitude
turbulence, whereas the other deformable mirror compensates field
independent aberrations in a pupil image. The opto-mechanical design
allows for changing the conjugate plane of the two high-altitude DMs
independently between two and nine kilometers. The pupil plane DM can
be placed either in a pupil image upstream of the high-altitude DMs or
downstream. This capability allows for performing experimental studies
on the impact of the geometrical order of the deformable mirrors and
the conjugate position. The control system is flexible, too, which
allows for real-world analysis of various control approaches. This
paper gives an overview of the NST MCAO system and reveals the first
MCAO corrected image taken at Big Bear Solar Observatory.
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: Challenges for the DKIST Data Center
Authors: Reardon, Kevin P.; Rimmele, Thomas R.
Bibcode: 2014AAS...22421843R
Altcode:
Processing the large volumes of complex, multi-instrument, ground-based
data generated at the DKIST will require implementation of algorithms
and tools at a level not previously achieved for high-resolution,
ground-based solar telescopes. We discuss some the goals of the
data reduction pipelines for DKIST, including the different types
of calibrations that would (optimally) be applied to the acquired
data. We highlight some of the particular challenges for ground-based
data, including seeing effects, atmospheric dispersion, and rapid
changes in instrumental calibrations. We will describe a possible
software framework for the implementation of the pipelines, as well
as point out some areas for community input or VSO integration in the
development process.
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 Construction Status
Report
Authors: McMullin, Joseph P.; Rimmele, T. R.; Warner, M.; Berger,
T.; Keil, S. L.
Bibcode: 2013SPD....4440001M
Altcode:
The Advanced Technology Solar Telescope (ATST) will provide observing
capabilities in the visible through infrared wavelengths with
unprecedented resolution and sensitivity. Designed to study solar
magnetism that controls the solar wind, flares, CMEs and variability in
the Sun's output, the ATST will be capable of detecting and spatially
resolving the fundamental astrophysical processes at their intrinsic
scales throughout the solar atmosphere. The 4-m class facility is
currently under construction in Maui, HI on the Haleakala Observatories
site with a scheduled completion of July 2019. Since the start of
site construction in December of 2012, significant progress has been
made toward the development of the observatory buildings (excavation,
foundations, working towards the steel erection). In addition, off-site,
the major subsystems of the telescope have been contracted, designs are
complete and fabrication is underway. We review the science drivers,
design details, technical challenges, and provide a construction status
update on the subsystems and their integration.
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: Active Optical Control of Quasi-Static Aberrations for ATST
Authors: Johnson, L. C.; Upton, R.; Rimmele, T. R.; Hubbard, R.;
Barden, S. C.
Bibcode: 2012ASPC..463..315J
Altcode:
The Advanced Technology Solar Telescope (ATST) requires active control
of quasi-static telescope aberrations in order to achieve the image
quality set by its science requirements. Four active mirrors will
be used to compensate for optical misalignments induced by changing
gravitational forces and thermal gradients. These misalignments
manifest themselves primarily as low-order wavefront aberrations that
will be measured by a Shack-Hartmann wavefront sensor. When operating
in closed-loop with the wavefront sensor, the active optics control
algorithm uses a linear least-squares reconstructor incorporating
force constraints to limit force applied to the primary mirror
while also incorporating a neutral-point constraint on the secondary
mirror to limit pointing errors. The resulting system compensates for
astigmatism and defocus with rigid-body motion of the secondary mirror
and higher-order aberrations with primary mirror bending modes. We
demonstrate this reconstruction method and present simulation results
that apply the active optics correction to aberrations generated by
finite-element modeling of thermal and gravitational effects over
a typical day of ATST operation. Quasi-static wavefront errors are
corrected to within limits set by wavefront sensor noise in all cases
with very little force applied to the primary mirror surface and
minimal pointing correction needed.
Title: Solar Limb Adaptive Optics: A Test of Wavefront Sensors
and Algorithms
Authors: Taylor, G. E.; Rimmele, T. R.; Marino, J.; Tritschler, A.;
McAteer, R. T. J.
Bibcode: 2012ASPC..463..321T
Altcode:
In order to advance our understanding of solar prominences, we need
to be able to observe them at high spatial, spectral and temporal
resolution. In order to determine physical properties of these cool
and faint coronal structures, however, one is forced to use long
exposure times, particularly in spectroscopic and spectropolarimetric
applications. It is thus crucial that image stabilization is provided,
preferrably in form of an adaptive optics (AO) system that is capable
to lock onto the off-limb prominence structure, potentially providing
diffraction limited imaging. We investigate the preliminary design
of such a solar-limb AO system based on a correlating Shack-Hartmann
sensor. As an alternative we also studied a solar-limb AO wavefront
sensor using a phase-diverse approach.
Title: Construction of the Advanced Technology Solar Telescope -
A Progress Report.
Authors: Rimmele, T. R.; Keil, S.; McMullin, J.; Goode, P. R.;
Knoelker, M.; Kuhn, J. R.; Rosner, R.; ATST Team
Bibcode: 2012IAUSS...6E.206R
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 ATST
will 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 4 m aperture, ATST will
resolve magnetic features at their intrinsic scales. A high order
adaptive optics system delivers a corrected beam to the initial set of
five state-of-the-art, facility class instrumentation located in the
coude laboratory facility. Photopheric and chromospheric magnetometry
is part of the key mission of four of these instruments. Coronal
magnetometry and spectroscopy will be performed by two of these
instruments at infrared wavelengths. The ATST project has transitioned
from design and development to its construction phase. Site construction
is expected to begin in the first half of 2012. The project has awarded
design and fabrication contracts for major telescope subsystems. A
robust instrument program has been established and all instruments
have passed preliminary design reviews or critical design reviews. A
brief summary of the science goals and observational requirements of
the ATST will be given, followed by a summary of the project status of
the telescope and discussion of the approach to integrating instruments
into the facility.
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: Expected Performance of Adaptive Optics in Large Aperture
Solar Telescopes
Authors: Marino, J.; Rimmele, T. R.
Bibcode: 2012ASPC..463..329M
Altcode:
Solar adaptive optics has become an indispensable tool for high
resolution solar observations. New generation solar telescopes, such
as the 4 m aperture Advanced Technology Solar Telescope, introduce
a new set of challenges to solar adaptive optics correction. Larger
aperture sizes are more susceptible to the effects on AO correction
performance of the extended field-of-view of the cross-correlating
Shack-Hartmann wavefront sensor. Observations at large zenith angles
further enhance these field-of-view effects and can introduce more
performance reductions due to atmospheric dispersion. We study the
expected correction performance of solar adaptive optics systems in
large aperture solar telescopes using an end-to-end adaptive optics
simulation package.
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: Quasi-static wavefront control for the Advanced Technology
Solar Telescope
Authors: Johnson, Luke C.; Upton, R.; Rimmele, T.; Barden, S.
Bibcode: 2012SPIE.8444E..3OJ
Altcode:
The Advanced Technology Solar Telescope (ATST) requires active control
of quasi-static telescope aberrations in order to meet image quality
standards set by its science requirements. Wavefront control is managed
by the Telescope Control System, with many telescope subsystems
playing key roles. We present the design of the ATST quasi-static
wavefront and alignment control architecture and the algorithms used to
control its four active mirrors. Two control algorithms are presented,
one that minimizes force on M1 actuators and another that employs
a neutral-pointing constraint on M2 to reduce pointing error. We
also present simulations that generate typical daily active mirror
trajectories which correct optical misalignments due to changing
gravitational and thermal loads.
Title: Ziegler-Nichols frequency response method for high-order
adaptive optics system of the Advanced Technology Solar Telescope
Authors: Curamen, Joseph; Johnson, Luke; Rimmele, Thomas
Bibcode: 2012SPIE.8447E..69C
Altcode:
No abstract at ADS
Title: The wavefront correction control system for the Advanced
Technology Solar Telescope
Authors: Kinney, Ellyne K.; Richards, Kit; Johnson, Luke; Rimmele,
Thomas R.; Barden, Samuel C.
Bibcode: 2012SPIE.8447E..2MK
Altcode:
The ATST Wavefront Correction Control System (WCCS) is the high-level
control software for the Wavefront Correction (WFC) system to be
employed in the new Advanced Technology Solar Telescope. The WFC is
comprised of a set of subsystems: the high-order adaptive optics
system for correction of wavefront aberrations, an active optics
system that calculates corrections for low-order distortions caused by
optical misalignments, a context viewing camera to provide quick-look
quality analysis data, and a limb guider for positioning an occulting
mask on the solar disk. The operation and configuration of the WFC
is determined by the operational modes set by the operator. The
Telescope Control System (TCS) sends these operational modes to the
WCCS, which is the interface between the telescope and the WFC. The
WCCS adopts a modular approach to the organization of the software. At
the top-level there is a high-level management controller which is the
interface to the TCS. This management controller is responsible for the
validation of commands received from the TCS and for the coordination
and synchronization of the operation of the WFC subsystems. Separate
subsystem controllers manage the functional behavior of each WFC
subsystem. In this way the WCCS provides a consistent interface to
the TCS for each subsystem while synchronizing and coordinating the
components of the Wavefront Correction system.
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: Advanced Technology Solar Telescope Construction: Progress
Report
Authors: Rimmele, Thomas R.; McMullin, J.; Keil, S.; Goode, P.;
Knoelker, M.; Kuhn, J.; Rosner, R.; ATST Team
Bibcode: 2012AAS...22012202R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) on Haleakala 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 ATST will 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 4
m aperture, ATST will resolve magnetic features at their intrinsic
scales. A high order adaptive optics system delivers a corrected
beam to the initial set of five state-of-the-art, facility class
instrumentation located in the coude laboratory facility. Photopheric
and chromospheric magnetometry is part of the key mission of four
of these instruments. Coronal magnetometry and spectroscopy will be
performed by two of these instruments at infrared wavelengths. The
ATST project has transitioned from design and development to its
construction phase. Site construction is expected to begin in April
2012. The project has awarded design and fabrication contracts for major
telescope subsystems. A robust instrument program has been established
and all instruments have passed preliminary design reviews or critical
design reviews. A brief overview of the science goals and observational
requirements of the ATST will be given, followed by a summary of the
project status of the telescope and discussion of the approach to
integrating instruments into the facility. The National Science
Foundation (NSF) through the National Solar Observatory (NSO) funds
the ATST Project. The NSO is operated under a cooperative agreement
between the Association of Universities for Research in Astronomy,
Inc. (AURA) and NSF.
Title: Solar Adaptive Optics
Authors: Rimmele, Thomas R.; Marino, Jose
Bibcode: 2011LRSP....8....2R
Altcode:
Adaptive optics (AO) has become an indispensable tool at ground-based
solar telescopes. AO enables the ground-based observer to overcome the
adverse effects of atmospheric seeing and obtain diffraction limited
observations. Over the last decade adaptive optics systems have
been deployed at major ground-based solar telescopes and revitalized
ground-based solar astronomy. The relatively small aperture of solar
telescopes and the bright source make solar AO possible for visible
wavelengths where the majority of solar observations are still
performed. Solar AO systems enable diffraction limited observations
of the Sun for a significant fraction of the available observing time
at ground-based solar telescopes, which often have a larger aperture
than equivalent space based observatories, such as HINODE. New ground
breaking scientific results have been achieved with solar adaptive
optics and this trend continues. New large aperture telescopes
are currently being deployed or are under construction. With the
aid of solar AO these telescopes will obtain observations of the
highly structured and dynamic solar atmosphere with unprecedented
resolution. This paper reviews solar adaptive optics techniques and
summarizes the recent progress in the field of solar adaptive optics. An
outlook to future solar AO developments, including a discussion of
Multi-Conjugate AO (MCAO) and Ground-Layer AO (GLAO) will be given.
Title: The Advanced Technology Solar Telescope - Constructing The
World's Largest Solar Telescope
Authors: Rimmele, Thomas R.; Keil, S.; Wagner, J.; ATST Team
Bibcode: 2011SPD....42.0801R
Altcode: 2011BAAS..43S.0801R
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 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 4 m 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 five state-of-the-art, facility class
instrumentation located in the coude laboratory facility. Coronal
magnetometry and spectroscopy will be performed by two of these
instruments at infrared wavelengths. In January 2010 the ATST
project transitioned from design and development to the construction
phase. The project has awarded contracts for major subsystems, including
the 4m primary mirror, architectural and engineering services related to
the Support Facilities, Enclosure construction design, Telescope Mount
Assembly, and Facilities Thermal System construction design. The State
of Hawai'I Board of Land and Natural Resources approved the Conservation
District Use Permit submitted by the University of Hawai'I at their
December 6, 2010 meeting in Honolulu, HI. A brief overview of
the science goals and observational requirements of the ATST will be
given, followed by a summary of the project status of the telescope and
discussion of the approach to integrating instruments into the facility.
Title: Solar Limb AO: Seeing the Hidden Detail in Solar Prominences
Authors: Taylor, Gregory; Rimmele, T.; Marino, J.; McAteer, J.
Bibcode: 2011SPD....42.1509T
Altcode: 2011BAAS..43S.1509T
In order to understand Solar Prominences, we need to observe them
at sub-arcsecond resolution, with a sub-second cadence. Present
image reconstruction techniques, such as Speckle Interferometry, are
capable of delivering high resolution images, but at a slow cadence. We
propose the design for a Solar Limb Adaptive Optics system that would
allow images to be captured at sub-second cadence with sub-arcsecond
resolution. The challenge, with Solar Limb AO, is the use of faint Hα
prominence structure near the limb, to derive wavefront measurements
at hight speed. Regular, on-disk Solar Adaptive Optics have sufficient
photon flux available, for the subaperture based wavefront sensor. In
contrast, a Shack Hartmann wave- front sensor, which uses faint Hα
prominence structure as its reference, is photon starved. Full aperture
sensor concepts, such as Phase Diversity, may have to be considered. It
is hoped that such a system, if successful, would be implemented on
the upcoming Advanced Technology Solar Telescope.
Title: The Visible Broadband Imager: The Sun at High Spatial and
Temporal Resolution
Authors: Friedrich, Woeger; Tritschler, A.; Uitenbroek, H.; Rimmele, T.
Bibcode: 2011SPD....42.2001F
Altcode: 2011BAAS..43S.2001F
The Visible Broadband Imager (VBI) will be the first of the five
first-light instruments for the Advanced Technology Solar Telescope
(ATST). It is designed to observe the solar atmosphere at heights
ranging from photosphere to chromosphere. High frame-rate detectors
that sample the FOV of up to 2.8 arcmin in diameter critically near or
at the diffraction limit of ATST's 4 meter aperture will facilitate 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 today 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 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: Solar Polarization Workshop 6
Authors: Kuhn, J. R.; Harrington, D. M.; Lin, H.; Berdyugina, S. V.;
Trujillo-Bueno, J.; Keil, S. L.; Rimmele, T.
Bibcode: 2011ASPC..437.....K
Altcode:
No abstract at ADS
Title: ATST: The Largest Polarimeter
Authors: Keil, S. L.; Rimmele, T. R.; Wagner, J.; Elmore, D.; ATST Team
Bibcode: 2011ASPC..437..319K
Altcode:
The Advanced Technology Solar Telescope's large collecting area,
combined with diffraction limited images delivered by adaptive optics,
will give it the ability to measure solar magnetic fields down to
scales of a few 20-30 km in the solar photosphere and the ability to
measure chromospheric and coronal magnetic fields.
Title: Stellar Imager (SI): developing and testing a predictive
dynamo model for the Sun by imaging other stars
Authors: Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska,
Margarita; Kraemer, Steve; Lyon, Richard; Mozurkewich, David;
Airapetian, Vladimir; Adams, John C.; Allen, Ronald J.; Brown, Alex;
Bruhweiler, Fred; Conti, Alberto; Christensen-Dalsgaard, Joergen;
Cranmer, Steve; Cuntz, Manfred; Danchi, William; Dupree, Andrea; Elvis,
Martin; Evans, Nancy; Giampapa, Mark; Harper, Graham; Hartman, Kathy;
Labeyrie, Antoine; Leitner, Jesse; Lillie, Chuck; Linsky, Jeffrey L.;
Lo, Amy; Mighell, Ken; Miller, David; Noecker, Charlie; Parrish, Joe;
Phillips, Jim; Rimmele, Thomas; Saar, Steve; Sasselov, Dimitar; Stahl,
H. Philip; Stoneking, Eric; Strassmeier, Klaus; Walter, Frederick;
Windhorst, Rogier; Woodgate, Bruce; Woodruff, Robert
Bibcode: 2010arXiv1011.5214C
Altcode:
The Stellar Imager mission concept is a space-based UV/Optical
interferometer designed to resolve surface magnetic activity and
subsurface structure and flows of a population of Sun-like stars,
in order to accelerate the development and validation of a predictive
dynamo model for the Sun and enable accurate long-term forecasting of
solar/stellar magnetic activity.
Title: Active reconstruction and alignment strategies for the Advanced
Technology Solar Telescope
Authors: Upton, Robert; Rimmele, Thomas
Bibcode: 2010SPIE.7793E..0EU
Altcode: 2010SPIE.7793E..11U
The Advanced Technology Solar Telescope (ATST) is a 4m off-axis
telescope with a Gregorian front end. At the time of its construction
it will be the world's largest solar astronomical telescope. During
scientific operations the ATST mirrors and structure will be deformed
due to thermal and gravitational loading. The ATST team has developed
a quasi-static alignment scheme that utilizes the wavefront sensing
signals from at least one and as many as three wavefront sensors in
the telescope science field of view, and active figure control of
the primary mirror and rigid body control of the secondary mirror to
achieve least-squares optical control of the telescope. This paper
presents the quasi-static alignment model for the ATST, and three
different active alignment schemes that are the damped least-squares
control, force optimized control that defines a least-squares aligned
state of the telescope subject to minimum primary actuator force,
and pivot-point control of the secondary mirror. All three strategies
achieve the desired minimum RMS wavefront error, but demonstrate
different optimized states of the telescope.
Title: Force-optimized alignment for optical control of the Advanced
Technology Solar Telescope
Authors: Upton, Robert; Cho, Myung; Rimmele, Thomas
Bibcode: 2010ApOpt..49G.105U
Altcode:
No abstract at ADS
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: Advanced Technology Solar Telescope project management
Authors: Wagner, J.; Hansen, E.; Hubbard, R.; Rimmele, T. R.; Keil, S.
Bibcode: 2010SPIE.7738E..0QW
Altcode: 2010SPIE.7738E..22W
The Advanced Technology Solar Telescope (ATST) has recently received
National Science Foundation (NSF) approval to begin the construction
process. ATST will be the most powerful solar telescope and the world's
leading resource for studying solar magnetism that controls the solar
wind, flares, coronal mass ejections and variability in the Sun's
output. This paper gives an overview of the project, and describes the
project management principles and practices that have been developed
to optimize both the project's success as well as meeting requirements
of the project's funding agency.
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: The Advanced Technology Solar Telescope: beginning construction
of the world's largest solar telescope
Authors: Rimmele, T. R.; Wagner, J.; Keil, S.; Elmore, D.; Hubbard,
R.; Hansen, E.; Warner, M.; Jeffers, P.; Phelps, L.; Marshall, H.;
Goodrich, B.; Richards, K.; Hegwer, S.; Kneale, R.; Ditsler, J.
Bibcode: 2010SPIE.7733E..0GR
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 successfully passed its final design review and the Environmental
Impact Study for construction of ATST on Haleakala, Maui, HI has
been concluded in December of 2009. The project is now entering
its construction phase. 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 4 m 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 spectropolarimeters. 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 fourmeter 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: The Advanced Technology Solar Telescope coude lab thermal
environment
Authors: Phelps, Leellen; Rimmele, Thomas; Hubbard, Robert P.;
Elmore, David
Bibcode: 2010SPIE.7733E..3UP
Altcode: 2010SPIE.7733E.120P
The ATST scientific instruments are located on benches installed on
a large diameter rotating coud lab floor. The light path from the
telescope to the instruments is greater than 38 meters and passes from
external ambient conditions to the 'shirt-sleeve' environment of the
coudé lab. In order to minimize any contribution to local seeing or
wavefront distortion, two strategies are implemented. First, an air
curtain is installed where the beam passes from ambient conditions
to the lab space and second, the coudé lab environmental conditions
are tightly controlled. This paper presents the design parameters
of the environmental conditions, the basis of each design parameter,
an overview of the equipment and components of the system planned to
control those conditions, and the thermal and computational fluid
dynamic analyses that have been performed in support of the system
as designed.
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: Advanced Technology Solar Telescope: A status report
Authors: Keil, S. L.; Rimmele, T. R.; Wagner, J.; ATST Team
Bibcode: 2010AN....331..609K
Altcode:
Magnetic fields control the inconstant Sun. The key to understanding
solar variability and its direct impact on the Earth rests with
understanding all aspects of these magnetic fields. The Advanced
Technology Solar Telescope (ATST) has been design specifically for
magnetic remote sensing. Its collecting area, spatial resolution,
scattered light, polarization properties, and wavelength performance
all insure ATST will be able to observe magnetic fields at all heights
in the solar atmosphere from photosphere to corona. After several
years of design efforts, ATST has been approved by the U.S. National
Science Foundation to begin construction with a not to exceed cost cap
of approximately $298M. Work packages for major telescope components
will be released for bid over the next several months. An application
for a building permit has been submitted.
Title: Scientific instrumentation for the 1.6 m New Solar Telescope
in Big Bear
Authors: Cao, W.; Gorceix, N.; Coulter, R.; Ahn, K.; Rimmele, T. R.;
Goode, P. R.
Bibcode: 2010AN....331..636C
Altcode:
The NST (New Solar Telescope), a 1.6 m clear aperture, off-axis
telescope, is in its commissioning phase at Big Bear Solar Observatory
(BBSO). It will be the most capable, largest aperture solar telescope
in the US until the 4 m ATST (Advanced Technology Solar Telescope)
comes on-line late in the next decade. The NST will be outfitted with
state-of-the-art scientific instruments at the Nasmyth focus on the
telescope floor and in the Coudé Lab beneath the telescope. At the
Nasmyth focus, several filtergraphs already in routine operation
have offered high spatial resolution photometry in TiO 706 nm,
H\alpha 656 nm, G-band 430 nm and the near infrared (NIR), with the
aid of a correlation tracker and image reconstruction system. Also,
a Cryogenic Infrared Spectrograph (CYRA) is being developed to supply
high signal-to-noise-ratio spectrometry and polarimetry spanning
1.0 to 5.0 μm. The Coudé Lab instrumentation will include Adaptive
Optics (AO), InfraRed Imaging Magnetograph (IRIM), Visible Imaging
Magnetograph (VIM), and Fast Imaging Solar Spectrograph (FISS). A 308
sub-aperture (349-actuator deformable mirror) AO system will enable
nearly diffraction limited observations over the NST's principal
operating wavelengths from 0.4 μm through 1.7 μm. IRIM and VIM are
Fabry-Pérot based narrow-band tunable filters, which provide high
resolution two-dimensional spectroscopic and polarimetric imaging in
the NIR and visible respectively. FISS is a collaboration between BBSO
and Seoul National University focussing on chromosphere dynamics. This
paper reports the up-to-date progress on these instruments including an
overview of each instrument and details of the current state of design,
integration, calibration and setup/testing on the NST.
Title: FIRS: a new instrument for photospheric and chromospheric
studies at the DST.
Authors: Jaeggli, S. A.; Lin, H.; Mickey, D. L.; Kuhn, J. R.; Hegwer,
S. L.; Rimmele, T. R.; Penn, M. J.
Bibcode: 2010MmSAI..81..763J
Altcode:
The simultaneous observation of select spectral lines at optical and
infrared wavelengths allows for the determination of the magnetic
field at several photospheric and chromospheric heights and thus
the 3D magnetic field gradient in the solar atmosphere. The Facility
Infrared Spectropolarimeter (FIRS) is a newly completed, multi-slit,
dual-beam spectropolarimeter installed at the Dunn Solar Telescope
(DST) at Sacramento Peak (NSO/SP). Separate optics and polarimeters
simultaneously observe two band-passes at visible and infrared
wavelengths with a choice of two modes: the Fe I 6302 Å and 15648 Å
lines in the photosphere; or the Fe I 6302 Å and He I 10830 Å line
in the photosphere and high chromosphere, respectively. FIRS can also
operate simultaneously with a white light camera, G-band imager, and
the Interferometric Bi-dimensional Spectrometer (IBIS) observing the
mid-chromospheric Ca II 8542 Å line. The instrument uses four parallel
slits to sample four slices of the solar surface simultaneously to
achieve fast, diffraction-limited precision imaging spectropolarimetry,
enabling the study of MHD phenomena with short dynamic time scales.
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: The Advanced Technology Solar Telescope: Science Goals,
Design and Project Status. (Invited)
Authors: Rimmele, T.; Keil, S. L.; Wagner, J.
Bibcode: 2009AGUFMSH53B..10R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) on Haleakala will be
the most powerful solar telescope and the world’s leading resource
for studying solar magnetism that controls the solar wind, flares,
coronal mass ejections and variability in the Sun’s output. The
project is about to enter the construction phase and is expected to
be fully commissioned in 2017. 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
will during which the technical and engineering challenges the ATST
project faces will be discussed. ATST will provide high resolution and
high sensitivity observations of the dynamic solar magnetic fields
throughout the solar atmosphere, including the corona. With its 4 m
aperture, ATST will resolve features at 0.”03 (20km on the sun)
at visible wavelengths. The science requirement for polarimetric
sensitivity (10-5 relative to intensity) and accuracy (5x10-4
relative to intensity) place strong constraints on the polarization
analysis and calibration units. 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 Coude lab facility. A
few examples of the many unique science capabilities of the 4m ATST
will be discussed. The initial set of first generation instruments
includes: 1: the Visible Broadband Imager will provide images at
the highest possible spatial and temporal resolution at a number
of specified wavelengths in the range from 390 nm to 860 nm. 2:
the Visible Spectro-Polarimeter will provide precision vector field
measurements simultaneously at diverse wavelengths in the visible
spectrum and thus deliver quantitative diagnostics of the magnetic
field vector as a function of height in the solar atmosphere, along
with the associated variation of the thermodynamic properties. 3: the
Diffraction-Limited Near-Infrared Spectro-Polarimeter will record with
high temporal cadence the full polarization state of spectral lines
in the near infrared wavelength regime from 900 nm to 2300 nm. 4:
the Cryogenic Near Infrared-Spectro-Polarimeter will measure solar
magnetic fields over a large field-of-view at infrared wavelengths
from 1000 nm to 5000 nm in the solar corona. 5: the Visible Tunable
Filter will provide two-dimensional spectroscopy and polarimetry
by recording diffraction-limited narrow-bandpass images with high
temporal resolution.
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: First Results from a Novel Magnetograph (SHAZAM)
Authors: DeForest, Craig; Rimmele, T.; Berger, T.; Peterson, J.
Bibcode: 2009SPD....40.3301D
Altcode:
The magnetic energy flux through the Sun's surface is dominated by small
features at all currently observable spatial scales; hence there is a
strong need to improve the spatial resolution of magnetic measurements,
which are increasingly photon starved as telescopes improve. The Solar
High-speed Zeeman Magnetograph (SHAZAM) is a line-of-sight magnetograph
based on the principle of spectral stereoscopy. It is designed to
acquire magnetograms quickly enough to beat image fluctuations due
to both solar evolution and terrestrial seeing, even on scales under
100 km on the Sun. It is over 100x more photon efficient than existing
quantitative magnetographs such as SOHO/MDI. We present first results
from an observing run at the National Solar Observatory's Dunn Solar
Telescope in May 2009, hopefully including near-diffraction-limited,
time resolved magnetogram sequences with better than 150km resolution
on the surface of the Sun.
Title: Advanced Technology Solar Telescope
Authors: Keil, Stephen L.; Rimmele, Thomas R.; Wagner, Jeremy
Bibcode: 2009EM&P..104...77K
Altcode: 2008EM&P..tmp...37K
High-resolution studies of the Sun’s magnetic fields are needed for a
better understanding of the fundamental processes responsible for solar
variability. The generation of magnetic fields through dynamo processes,
the amplification of fields through the interaction with plasma flows,
and the destruction of fields are poorly understood. There is incomplete
insight into physical mechanisms responsible for chromospheric and
coronal structure and heating, causes of variations in the radiative
output of the Sun, and mechanisms that trigger flares and coronal mass
ejections. Progress in answering these critical questions requires
study of the interaction of the magnetic field and convection
with a resolution sufficient to observe scale fundamental to these
processes. The planned 4 m aperture ATST will be a unique scientific
tool, with excellent angular resolution, a large wavelength range,
and low scattered light. With its integrated adaptive optics, the
ATST will achieve a spatial resolution nearly 10 times better than
any existing solar telescope. The ATST design and development phase
began in 2001 and it is now ready to begin construction in 2009.
Title: Generation, Evolution and Destruction of Solar Magnetic Fields
Authors: Keil, Stephen; Rimmele, Thomas; DeForest, Craig
Bibcode: 2009astro2010S.153K
Altcode:
No abstract at ADS
Title: Status of the Advanced Technology Solar Telescope
Authors: Rimmele, T.; Keil, S.; Wagner, J.; Atst Team
Bibcode: 2008ESPM...12..6.2R
Altcode:
The 4m ATST is scheduled to be commissioned within the next decade
and will replace current major NSO facilities with the most powerful
solar telescope and the world's leading resource for studying solar
magnetism that controls the solar wind, flares, coronal mass ejections
and variability in the Sun's output. As its highest priority science
driver ATST shall provide high resolution and high sensitivity
observations of the highly dynamic solar magnetic fields throughout
the solar atmosphere, including the corona. After a brief overview of
the science goals and unique observational capabilities of the ATST
a summary of the design of the telescope and its powerful first-light
instrumentation as well as the project status will be given.
Title: Assessment of local seeing within a telescope lab environment
Authors: Biérent, Rudolph; Rimmele, Thomas; Marino, Jose
Bibcode: 2008SPIE.7012E..34B
Altcode: 2008SPIE.7012E.107B
Turbulence, which may exist along an optical path inside a telescope
or laboratory setup such as the Dunn Solar Telescope observing room,
can negatively impact the imaging performance at the final detector
plane. In order to derive requirements and error budget terms for the
Advanced Technology Solar Telescope (ATST) we performed interferometric
measurements with the goal to determine the amount of aberrations
introduced by the air mass through which the beam propagates and
characterize temporal and spatial frequencies of these aberrations. We
used a He-Ne laser interferometer to measure aberrations along a 50m
and 33m, collimated 150mm diameter laser beam. The experiments were
performed with both vertical and horizontal beam propagation. We
investigated the impact on the amount of self-induced turbulence of
the difference in temperature between the top and the bottom of the
optical laboratory, the impact of heat sources, such as electronics
racks, and the effect of a laminar air flow applied to parts of the
beam path. The analysis of the interferograms yields values of the rms
wave front aberrations excluding tip/tilt in the range of 1.45nm/m -
2nm/m (@632nm) for the vertical beam propagation and between 0.8nm/m -
1.6nm/m for the horizontal beam. The spatial spectrum of the turbulence
tends to decay faster than Kolmogorov turbulence. This is true, in
particular, for the horizontal beam path. The temporal frequencies
are on the order of a few Hz (<10Hz).
Title: The unique scientific capabilities of the Advanced Technology
Solar Telescope
Authors: Rimmele, T. R.; ATST Team
Bibcode: 2008AdSpR..42...78R
Altcode:
The 4 m Advance Technology Solar Telescope (ATST) will be the most
powerful solar telescope and the world's leading resource for studying
solar magnetism that controls the solar wind, flares, coronal mass
ejections and variability in the Sun's output. We provide an overview of
the science goals and observational requirements of the ATST and a brief
summary of the design status of the telescope and its instrumentation.
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: Advanced Technology Solar Telescope: a progress report
Authors: Wagner, J.; Rimmele, T. R.; Keil, S.; Hubbard, R.; Hansen,
E.; Phelps, L.; Warner, M.; Goodrich, B.; Richards, K.; Hegwer, S.;
Kneale, R.; Ditsler, J.
Bibcode: 2008SPIE.7012E..0IW
Altcode: 2008SPIE.7012E..16W
The four-meter Advanced Technology Solar Telescope (ATST) will be the
most powerful solar telescope and the world's leading resource for
studying solar magnetism that controls the solar wind, flares, coronal
mass ejections and variability in the Sun's output. Development of a
four-meter solar telescope presents many technical challenges (e.g.,
thermal control of the enclosure, telescope structure and optics). We
give a status report of the ATST project (e.g., system design reviews,
PDR, Haleakalä site environmental impact statement progress) and
summarize the design of the major subsystems, including the telescope
mount assembly, enclosure, mirror assemblies, wavefront correction,
and instrumentation.
Title: High resolution observations using adaptive optics:
Achievements and future needs
Authors: Sankarasubramanian, K.; Rimmele, T.
Bibcode: 2008JApA...29..329S
Altcode: 2008arXiv0801.3125S
Over the last few years, several interesting observations were
obtained with the help of solar Adaptive Optics (AO). In this paper,
few observations made using the solar AO are enlightened and briefly
discussed. A list of disadvantages with the current AO system are
presented. With telescopes larger than 1.5 m expected during the
next decade, there is a need to develop the existing AO technologies
for large aperture telescopes. Some aspects of this development are
highlighted. Finally, the recent AO developments in India are also
presented.
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: The Facility IR Spectropolarimeter for the Dunn Solar Telescope
Authors: Jaeggli, S. A.; Lin, H.; Mickey, D. L.; Kuhn, J. R.; Hegwer,
S. L.; Rimmele, T. R.; Penn, M. J.
Bibcode: 2008AGUSMSH31A..11J
Altcode:
The Facility IR Spectropolarimeter(FIRS) is a multi-slit
spectropolarimeter designed for the Dunn Solar Telescope (DST) at the
National Solar Observatory on Sacramento Peak (NSO/SP) in New Mexico to
study magnetism on the solar surface. The instrument samples adjacent
slices of the solar surface using four parallel slits to achieve high
cadence, diffraction-limited, precision imaging-spectropolarimetry. Due
to the versatile, multi-armed design of the spectrograph, up to
four spectral lines at visible and infrared wavelengths, covering
four different heights in the solar atmosphere, can be observed
simultaneously. In this poster-paper we will describe the design,
capabilities, and performance of the instrument.
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: On the Relation between Umbral Dots, Dark-cored Filaments,
and Light Bridges
Authors: Rimmele, T.
Bibcode: 2008ApJ...672..684R
Altcode:
We present high-resolution observations of the complex active region AR
0484 observed close to disk center with the Dunn Solar Telescope. The
field of view (FOV) contains several interesting features, including a
number of umbral fragments, light bridges of varying width, umbral dots,
and dark-cored penumbral filaments. A time sequence of reconstructed
G-band images and adaptive optics-corrected UBF filtergrams was analyzed
with the goal of comparing observations with recent simulations and
models of sunspot fine structure. In an umbral fragment in which the
field strength is relatively weak, we find a large number of umbral
dots. We were able to resolve dark substructure within bright umbral
dots that in some cases resembles the dark lanes recently predicted
by magnetohydrodynamic (MHD) simulations. Umbral dot substructure
is also clearly revealed in images of spectral line parameters. We
compare line parameters for dark-cored penumbral filaments, dark lanes
observed in light bridges, and the dark umbral dot substructure. We
find evidence that all of these structures are elevated above the
formation height of the continuum. We observe dynamic proper motion of
umbral dots, including motion along a narrow lane that occurs within
an umbral fragment and shows similarity to the proper motion observed
in narrow light bridges. Furthermore, we study the temporal variation
of spectral line parameters such as the integrated line absorption of
the temperature-sensitive Fe I λ5434 line. The computed power maps
show features closely related to sunspot fine structure.
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: Real-time processing for the ATST AO system
Authors: Richards, K.; Rimmele, T.
Bibcode: 2008amos.confE..26R
Altcode:
The real-time processing requirements for the four meter Advanced
Technology Solar Telescope extended source high order adaptive
optics system will be approximately 15 times that of the Dunn Solar
Telescope AO systems on which the ATST AO system is based. The ATST AO,
with its approximately 1232 subapertures, will use massively parallel
processing and is based on Analog Devices TigerSHARC DSPs as the central
processing units. We will discuss the requirements for processing and
data handling and the architecture of the correlating Shack-Hartmannn
and reconstructor processing unit and present the results of bench-mark
testing of the DSP hardware that was selected for the ATST AO system.
Title: The Discrepancy in G-Band Contrast: Where is the Quiet Sun?
Authors: Uitenbroek, H.; Tritschler, A.; Rimmele, T.
Bibcode: 2007ApJ...668..586U
Altcode: 2007arXiv0704.3637U
We compare the rms contrast in observed speckle reconstructed G-band
images with synthetic filtergrams computed from two magnetohydrodynamic
simulation snapshots. The observations consist of 103 bursts of 80
frames each, taken at the Dunn Solar Telescope (DST), sampled at twice
the diffraction limit of the telescope. The speckle reconstructions
account for the actions of the adaptive optics (AO) system at the DST in
order to supply reliable photometry. We find a considerable discrepancy
between the observed rms contrast of 14.1% for the best reconstructed
images and the synthetic rms contrast of 21.5% in a simulation snapshot
thought to be representative of the quiet Sun. The areas of features
in the synthetic filtergrams that have positive or negative contrast
beyond the minimum and maximum values in the reconstructed images have
spatial scales that should be resolved. This leads us to conclude that
there are fundamental differences in the rms G-band contrast between
observed and computed filtergrams. On the basis of the substantially
reduced granular contrast of 16.3% in the synthetic plage filtergram,
we speculate that the quiet Sun may contain more weak magnetic field
than previously thought.
Title: Diffraction-limited Spectropolarimetry At The Dunn Solar
Telescope
Authors: Tritschler, Alexandra; Sankarasubramanian, K.; Rimmele, T.;
Gullixson, C.; Fletcher, S.
Bibcode: 2007AAS...210.2603T
Altcode: 2007BAAS...39R.323T
The combination of high spectral and angular resolution is of vital
importance for an accurate characterization of the magnetic field
vector and the thermal and kinematic conditions in the magnetized
atmosphere utilizing inverion techniques. The Diffraction-Limited
Spectro-Polarimeter (DLSP) operated at the NSO Dunn Solar Telescope
is an innovative grating polarimeter specifically designed to meet the
high requirements pursued in solar spectropolarimetry. To demonstrate
the scientific potential of observations obtained with the DLSP and
its support devices we present an overview of questions that have been
recently addressed with the DLSP. Furthermore, we discuss the latest
modifications related to instrument control and data acquisition
pipeline implemented to improve its performance and pave the way to
the realm of queque observing at the DST in preparation for ATST.
Title: On The Relation Between Umbral Dots, Dark-cored Filaments
And Light Bridges
Authors: Rimmele, Thomas R.
Bibcode: 2007AAS...21012002R
Altcode: 2007BAAS...39..245R
We present high resolution observations of the complex active region
AR0484 observed close to disk center at the Dunn Solar Telescope. The
field of view contains several interesting features including a number
of umbral fragments, light bridges of varying width, umbral dots and
dark-cored penumbral filaments. A time sequence of reconstructed g-band
images and adaptive optics corrected UBF filtergrams were analyzed
with the goal to compare observations with recent model predictions for
sunspot fine-structure. In an umbral fragment where the field strength
is relatively weak we find a large number of umbral dots. We were able
to resolve substructure within umbral dots that in some cases resembles
the dark lanes recently predicted by MHD simulations by Schuessler
and Voegler 2006. Umbral dot substructure is also clearly revealed
in images of spectral line parameters. We compare line parameters for
dark-cored penumbral filaments, dark lanes observed in light bridges
and the umbral dot substructure. We observe dynamic proper motion of
umbral dots, including motion along a narrow lane that occurs within
an umbral fragment and shows similarity to the proper motion observed
in narrow light bridges. Furthermore, we study the temporal variation
of spectral line parameters such as the integrated line absorption of
the temperature sensitive FeI 5434 A line.
Title: Long Exposure Point Spread Function Estimation Adaptive Optics
Loop Data: Results and Validation
Authors: Marino, Jose; Rimmele, T.
Bibcode: 2007AAS...210.2601M
Altcode: 2007BAAS...39..134M
Current work in Solar Physics requires high resolution observations
from ground based telescopes. However, the performance of any ground
based telescope is ultimately limited by optical aberrations produced
by atmospheric turbulence. Adaptive Optics (AO) is a powerful tool that
aims to correct these aberrations in real time considerably improving
image quality. We present a method to estimate the long exposure
PSF of the AO corrected solar image using AO loop data. Wavefront sensor
and mirror data produced by the AO system during normal operation
contain information about uncorrected residuals aberrations that
define the shape of the long exposure point spread function (PSF). The
estimated long exposure PSF is used to improve image quality through
post-processing techniques. Post-processed images produce more reliable
quantitative measurements of physical parameters. Results obtained
by applying the method to actual solar and star observations captured at
the Dunn Solar Telescope will be shown. The accuracy of the estimated
PSFs is tested with observations of the star Sirius which produce a
direct measurement of the system's PSF.
Title: Acoustic Shocks in the Quiet Solar Chromosphere
Authors: Cauzzi, G.; Reardon, K. P.; Vecchio, A.; Janssen, K.;
Rimmele, T.
Bibcode: 2007ASPC..368..127C
Altcode:
We exploit the two-dimensional spectroscopic capabilities of the
Interferometric BIdimensional Spectrometer (IBIS) to study the
chromospheric Ca II 854.2 nm line and its temporal evolution in a quiet
region at the center of the solar disk. The Ca II 854.2 profiles in the
internetwork portion of the field of view clearly indicate the presence
of hydrodynamic shocks, occurring at frequencies above the acoustic
cut-off. The location and strength of such shocks perfectly map
the areas where large velocity power is found at frequencies of 5.5-8
mHz in a standard Fourier analysis. The shocks locations evidence a
sharp partition of the quiet area in regions of very distinct dynamical
behavior, highlighting the role of the local magnetic topology in
structuring the lower chromosphere. The portions of the field of view
where the photospheric field is very weak, and that are presumably
connected to distant magnetic structures (or open to the interplanetary
field), are the site of frequent shock occurrence. On the contrary, in
regions neighboring the magnetic network and harboring a more horizontal
configuration of the chromospheric magnetic field, shocks are heavily
suppressed, even if the photospheric field is essentially absent in
these areas as well. These latter regions, with much reduced velocity
power at frequencies of 5.5-8 mHz \citep[the ``magnetic shadows'' first
described in][]{gc-judge_01}, are spatially coincident with fibrilar
structures visible in the Ca II 854.2 line core intensity maps. We
finally argue that areas within and immediately surrounding the magnetic
network also display evidence of chromospheric shocks, but occurring at
periodicities of 4-6 minutes. Such slow shocks are stronger than those
occurring in field-free areas, as evidenced by the strong emission
in the inner blue-wing of the line. This is in agreement with recent
results claiming that magneto-acoustic shocks can develop in inclined
magnetic structures, acting as `portals' through which the powerful
low-frequency photospheric oscillations can leak into the chromosphere.
Title: What Makes The Advanced Technology Solar Telescope (ATST)
So Advanced?
Authors: Kuhn, Jeffrey R.; Rimmele, T.; ATST Design Team
Bibcode: 2007AAS...210.6701K
Altcode: 2007BAAS...39..175K
-- Its the science! While its true that we haven't advanced ground-based
solar astronomy by a leap as big as this since Galileo, its the
qualitatively new insights that we expect with ATST that drive its
design. ATST isn't so much a telescope as much as it is a sensitive
magnetometer, and a high dynamic range imaging spectropolarimeter. In
this talk we'll try to draw the lines between the questions you've
always wanted to ask about the Sun, and this unique optical and
infrared instrument.
Title: Comparison of Ca II K and Ca II 8542 Å Images
Authors: Reardon, K. P.; Cauzzi, G.; Rimmele, T.
Bibcode: 2007ASPC..368..151R
Altcode:
We compare a time sequence of filtergrams obtained in the Ca II K line
with a series of spectrally resolved images obtained simultaneously
with the IBIS instrument in the Ca II 8542 Å line. Using the
narrowband IBIS images and a synthetic filter profile, we construct
simulated 8542 filtergrams that mimic the observed K2V
filtergrams. We observe that these filtergrams appear to contain
elements corresponding to both photospheric and chromospheric
structures. Intermediate scale patterns seen in the filtergrams may
simply be the result of the combination of a variety of structures
from different atmospheric levels. We analyze the Fourier power
spectra of the filtergrams and note that at frequencies well above
the acoustic cut-off value the observed power in the K2V
filtergrams seems to be predominantly photospheric in origin. The use
of Ca II H and K filtergrams to study the chromospheric behavior thus
may be inherently problematic. Narrowband images in the Ca II 8542 Å
line might provide a better source of information about chromospheric
behavior with little loss in spatial or temporal resolution.
Title: Detection of opposite polarities in a sunspot light bridge:
evidence of low-altitude magnetic reconnection
Authors: Bharti, Lokesh; Rimmele, Thomas; Jain, Rajmal; Jaaffrey,
S. N. A.; Smartt, R. N.
Bibcode: 2007MNRAS.376.1291B
Altcode: 2007astro.ph..1674B; 2007MNRAS.tmp..160B
A multiwavelength photometric analysis was performed in order to study
the sub-structure of a sunspot light bridge in the photosphere and
the chromosphere. Active region NOAA 8350 was observed on 1998 October
8. The data consist of a 100 min time series of 2D spectral scans of
the lines FeI 5576 Å, Hα 6563 Å, FeI 6302.5 Å, and continuum images
at 5571 Å. We recorded line-of-sight magnetograms in 6302.5 Å. The
observations were taken at the Dunn Solar Telescope at US National Solar
Observatory, Sacramento Peak. We find evidence for plasma ejection
from a light bridge followed by Ellerman bombs. Magnetograms of the
same region reveal opposite polarity in light bridge with respect to
the umbra. These facts support the notion that low-altitude magnetic
reconnection can result in the magnetic cancellation as observed in
the photosphere.
Title: Field-Dependent Adaptive Optics Correction Derived with the
Spectral Ratio Technique
Authors: Denker, C.; Deng, N.; Rimmele, T. R.; Tritschler, A.;
Verdoni, A.
Bibcode: 2007SoPh..241..411D
Altcode:
In this empirical study, we compare high-resolution observations
obtained with the 65-cm vacuum reflector at Big Bear Solar Observatory
(BBSO) in 2005 and with the Dunn Solar Telescope (DST) at the National
Solar Observatory/Sacramento Peak (NSO/SP) in 2006. We measure the
correction of the high-order adaptive optics (AO) systems across
the field of view (FOV) using the spectral ratio technique, which
is commonly employed in speckle masking imaging, and differential
image motion measurements. The AO correction is typically much larger
(10'' to 25'') than the isoplanatic angle and
can be described by a radially symmetric function with a central core
and extended wings. The full-width at half-maximum (FWHM) of the core
represents a measure of the AO correction. The average FWHM values
for BBSO and NSO/SP are 23.5'' and 18.2'',
respectively. The extended wings of the function show that the
AO systems still contribute to an improved speckle reconstruction
at the periphery of the 80''×80'' FOV. The
major differences in the level of AO correction between BBSO and
NSO/SP can be explained by different contributions of ground-layer-
and free-atmosphere-dominated seeing, as well as different FOVs of
the wavefront sensors. In addition, we find an anisotropic spectral
ratio in sunspot penumbrae caused by the quasi-one-dimensional nature
of penumbral filaments, which introduces a significant error in the
estimation of the Fourier amplitudes during the image restoration
process.
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: Solar atmospheric oscillations and the chromospheric magnetic
topology
Authors: Vecchio, A.; Cauzzi, G.; Reardon, K. P.; Janssen, K.;
Rimmele, T.
Bibcode: 2007A&A...461L...1V
Altcode: 2006astro.ph.11206V
Aims:We investigate the oscillatory properties of the quiet solar
chromosphere in relation to the underlying photosphere, with particular
regard to the effects of the magnetic topology.
Methods: For the
first time we perform a Fourier analysis on a sequence of line-of-sight
velocities measured simultaneously in a photospheric (Fe I 709.0 nm)
and a chromospheric line (Ca II 854.2 nm). The velocities were obtained
from full spectroscopic data acquired at high spatial resolution with
the Interferometric BIdimensional Spectrometer (IBIS). The field of
view encompasses a full supergranular cell, allowing us to discriminate
between areas with different magnetic characteristics.
Results: We
show that waves with frequencies above the acoustic cut-off propagate
from the photosphere to upper layers only in restricted areas of
the quiet Sun. A large fraction of the quiet chromosphere is in fact
occupied by “magnetic shadows”, surrounding network regions, that
we identify as originating from fibril-like structures observed in
the core intensity of the Ca II line. We show that a large fraction
of the chromospheric acoustic power at frequencies below the acoustic
cut-off, residing in the proximity of the magnetic network elements,
directly propagates from the underlying photosphere. This supports
recent results arguing that network magnetic elements can channel
low-frequency photospheric oscillations into the chromosphere, thus
providing a way to input mechanical energy in the upper layers.
Title: Ground-based solar facilities in the U.S.A.
Authors: Denker, C.; Gary, D. E.; Rimmele, T. R.
Bibcode: 2007msfa.conf...31D
Altcode:
In this review, we present the status of new ground-based facilities
for optical and radio observations of the Sun in the United States. The
4-meter aperture Advanced Technology Solar Telescope (ATST) under the
stewardship of the National Solar Observatory (NSO) has successfully
completed its design phase and awaits funding approval. The 1.6-meter
aperture New Solar Telescope (NST) at Big Bear Solar Observatory
(BBSO) is currently under construction. Complementing these optical
telescopes is the Frequency Agile Solar Radiotelescope (FASR)
an instrument for dynamic broadband imaging spectroscopy covering
a multitude of radio frequencies from 50 MHz to 20 GHz. Imaging
spectroscopy and polarimetry are common features of these telescopes,
which will provide new insight regarding the evolution and nature of
solar magnetic fields. High-resolution observations of solar activity,
bridging the solar atmosphere from the photosphere to the corona, will
be obtained with a dedicated suite of instruments. Special emphasis
of this review will be put on the interplay between instrumentation
and scientific discovery.
Title: Multiwavelength Study of Flow Fields in Flaring Super Active
Region NOAA 10486
Authors: Deng, N.; Xu, Y.; Yang, G.; Cao, W.; Liu, C.; Rimmele, T. R.;
Wang, H.; Denker, C.
Bibcode: 2006AGUFMSH31B..06D
Altcode:
We present high resolution observations of horizontal flow fields
measured by Local Correlation Tracking from intensity images in three
wavelengths, i.e., G-Band (GB), White-Light (WL), and Near InfraRed
(NIR). The observations were obtained on 2003 October~29 within
the flaring super active region NOAA~10486, which was the source of
several X-class flares, including an X10 flare that occurred near
the end of the observing run. The data were obtained at National
Solar Observatory/Sacramento Peak (NSO/SP) using the newly developed
high-order Adaptive Optics (AO) system. We also use Dopplergrams
and magnetograms from MDI on board SOHO to study the line-of-sight
flow and magnetic field. We observe persistent and long-lived (at
least 5 hours) strong horizontal and vertical shear flows (both in
the order of 1 km s-1) along the magnetic Neutral Line (NL) until
the X10 flare occurred. From lower photospheric level (NIR), the
direction of the flows does not change up to the upper photosphere
(GB), while the flow speeds in the shear motion regions decrease and
on the contrary those in regions without shear motions increase with
increasing altitude. Right after the X10 flare, the magnetic gradient
decreased, while both horizontal and vertical shear flows dramatically
enhanced near the flaring NL. Our results suggest that photospheric
shear flows and local magnetic shear near the NL can increase after
the flare, which may be the result of shear release in the overlying
large-scale magnetic system or the reflection of a twisted or sheared
flux emergence carrying enough energy from subphotosphere.
Title: The Diffraction Limited Spectro-Polarimeter
Authors: Sankarasubramanian, K.; Lites, B.; Gullixson, C.; Elmore,
D.; Hegwer, S.; Streander, K.; Rimmele, T.; Fletcher, S.; Gregory,
S.; Sigwarth, M.
Bibcode: 2006ASPC..358..201S
Altcode:
The Diffraction Limited Spectro-Polarimeter (DLSP) is a
collaboration between the National Solar Observatory (NSO) and the
High Altitude Observatory (HAO) to provide a stable instrument
for precision measurements of solar vector magnetic fields at high
angular resolution. The DLSP is integrated with the new high-order
Adaptive Optics (HOAO) system at the Dunn Solar Telescope (DST)
and provides Stokes spectra of the Fe I 630 nm lines approaching the
0.2 arcs3c diffraction limit of the DST. It is configured as a fixed,
well-calibrated instrument that may be used simultaneously with G-band
(1 nm bandpass) and a Ca K imagers (0.1 nm bandpass). The 2K×2K G-band
imager allows fast frame selection and includes a burst mode for speckle
imaging. The setup of DLSP and its imagers require only about 10 min of
preparation before start of observations. This fixed setup facilitates
standardized data reduction. The DLSP permits observations with 0.09
arcsec sampling in high resolution mode. In wide-field mode, the 0.27
arcsec sampling allows one to map regions about 3 arcmin on a side. The
achieved continuum S/N is 500 (1500) in high resolution (wide-field)
mode for a 4 s integration. It is possible to achieve higher S/N by
integrating longer. Data reduction routines are now available in IDL
for post-observation processing, and parallel analysis routines in
FORTRAN 77 are being developed to allow ``on-the-fly'' data reduction
and inversion.
Title: Intensity and Velocity Oscillations in Magnetic Flux
Concentrations (P9)
Authors: Bharti, L.; Rimmele, Thomas
Bibcode: 2006ihy..workE.101B
Altcode:
We analyzed intensity and velocity oscillations in magnetic network
using high-resolution 2D spectral scan images from Interferometric
Bi- dimensional Spectrometer (IBIS). In photosphere, oscillations in
intensity and velocity in 2-5.2 mHz band shows reduced amplitude while
at higher frequencies 5.2-7.0 mHz and 7.3-25.8 mHz band oscillations
amplitude enhance in line core intensity and shows reduced amplitude
in line core velocity however in chromosphere the oscillations
have different character, we found higher power in 2-5.2 mHz,
5.2-7.0 mHz and 7.3-25.8 mHz band in core velocity compared to core
intensity. Amplitude variation with height is also inferred from our
analysis. These findings are manifestation of high frequencies halos
around strong flux concentrations (pores) in intermediate field strength
network and mode conversion of solar p-modes in magnetic fields.
Title: The Evershed Flow: Flow Geometry and Its Temporal Evolution
Authors: Rimmele, T.; Marino, J.
Bibcode: 2006ApJ...646..593R
Altcode:
A diffraction-limited 120 minute time sequence of Evershed flows along
penumbral filaments was obtained using high-order adaptive optics
in conjunction with postprocessing. We observe individual Evershed
flow channels and study their evolution in time. The vast majority of
flow channels originate in bright, inner footpoints of size 0.2"-0.4"
with an upflow. The upflow turns into a horizontal outflow along a
dark penumbral filament within fractions of 1" (300-500 km). The time
sequence clearly shows that both (bright) upflow and (dark) horizontal
flow move around and evolve as a unit, indicating that they are part of
the same feature. The inner footpoints are brighter than the average
quiet photosphere and move inward at 0.5-1 km s-1. Our
observations provide strong evidence that penumbral grains are the
inner footpoints of Evershed flows where a hot upflow occurs. We
observe an Evershed flow channel as it appears to emerge near the
outer penumbra and track the flow over a period of about 100 minutes
as it moves toward the penumbra-umbra edge, where it disappeared. We
observe a steep decline (<=0.2") of the velocity at outer end of
individual flow channels, even for flow channels that end well within
the penumbra. This sharp outer edge of the flow channels is also
observed to move inward toward the penumbra-umbra boundary. Flows in
dark-cored penumbral filaments appear to be produced by the Evershed
effect. We discuss our observational results in the context of models
of the Evershed effect. Some aspects of our observations provide strong
support for the moving tube model of the Evershed flow.
Title: Progress with solar multi-conjugate adaptive optics at NSO
Authors: Rimmele, Thomas; Richards, Kit; Roche, Jacqueline; Hegwer,
Steve; Tritschler, Alexandra
Bibcode: 2006SPIE.6272E..06R
Altcode: 2006SPIE.6272E...5R
We have implemented a MCAO experiment at the Dunn Solar Telescope. The
MCAO system uses 2 deformable mirrors, one conjugated to the telescope
entrance pupil and other one conjugated to a layer in the upper
atmosphere. 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 used three
"solar guide stars". We have successfully and stably locked the MCAO
system on solar structure. We varied the height of the upper conjugate
between 3km and 9 km. A large number of images were recorded in order
to evaluate the performance of the system. The data analysis is still
ongoing. We present preliminary results and discuss future plans.
Title: The wavefront correction system for the Advanced Technology
Solar Telescope
Authors: Rimmele, T.; Richards, K.; Roche, J. M.; Hegwer, S. L.;
Hubbard, R. P.; Hansen, E. R.; Goodrich, B.; Upton, R. S.
Bibcode: 2006SPIE.6272E..12R
Altcode: 2006SPIE.6272E..33R
An important part of a large solar telescope is the ability to correct,
in real time, optical alignment errors caused by gravitational bending
of the telescope structure and wavefront errors caused by atmospheric
seeing. The National Solar Observatory is currently designing the 4
meter Advanced Technology Solar Telescope (ATST). The ATST wavefront
correction system, described in this paper, will incorporate a number
of interacting wavefront control systems to provide diffraction limited
imaging performance. We will describe these systems and summarize the
interaction between the various sub-systems and present results of
performance modeling.
Title: Long exposure point spread function estimation from adaptive
optics loop data: validation and results
Authors: Marino, Jose; Rimmele, Thomas; Christou, Julian
Bibcode: 2006SPIE.6272E..3WM
Altcode: 2006SPIE.6272E.124M
Adaptive Optics systems have revolutionized ground based astronomy by
providing real time correction for atmospheric aberrations. However,
due to limited temporal and spatial bandwidth the correction provided is
not perfect. With knowledge of the Point Spread Function correction can
be further improved. The lack of point sources in Solar observations
makes a direct measurement of the PSF impossible. We present a
method to obtain a PSF estimate from the Adaptive Optics system loop
telemetry. Using this method we can obtain a PSF for each captured AO
corrected image and correct each image individually. We applied this
method to a long time series of Solar data obtaining satisfactory
results. Also in an attempt to validate this method we successfully
observed the star Sirius with the Dunn Solar Telescope. The AO corrected
star images provide a direct measurement of the PSF that can be compared
to our estimates obtained from the AO telemetry data.
Title: High-Resolution Studies of Complex Solar Active Regions
Authors: Deng, Na; Wang, H.; Liu, C.; Yang, G.; Xu, Y.; Tritschler,
A.; Cao, W.; Rimmele, T. R.; Denker, C.
Bibcode: 2006SPD....37.3401D
Altcode: 2006BAAS...38..258D
Most Flares and CMEs occur or originate in solar active regions,
typically in sunspots with complex magnetic fields such as
delta-spots. Rapid and substantial changes of the sunspot structure have
been discovered to be associated with flares/CMEs. Rapid penumbral decay
and umbral enhancements are intensity changes, which are interpreted as
signatures of magnetic reconnection during the flare. The magnetic field
lines switch from an inclined to a more vertical orientation. Strong and
long-lived shear flows near the flaring magnetic inversion line have
been detected using Local Correlation Tracking (LCT) techniques based
on multi-wavelength high resolution observations. A newly observed and
important phenomenon is the increased local shear flow and magnetic
shear right after the flare in spite of theoretical models requiring
an overall decrease in the magnetic free energy. The emergence of a
twisted or pre-sheared flux rope near the neutral line is a possible
interpretation. Using high-order adaptive optics combined post-facto
speckle masking image reconstruction, we can obtain time-series with
highly improved image quality and spatial resolution in the order of
0.14" or about 100 km on the solar surface. We combine the observed
longitudinal Dopplergrams obtained with two-dimensional imaging
spectrometer and transverse LCT flow maps derived from time-series
of speckle reconstructed images to create real local 3D flow maps
(view from above). Using these precise 3D flow maps observed in a
typical sunspot in the course of its center to limb disc passage,
we observe distinct division line between radially inward and outward
flow in the penumbra and its evolution during the decaying phase of
the sunspot. The inclination angles of penumbral flow channels are
also calculated.Acknowledgments: This work is supported by NSF under
grant ATM 03-42560, ATM 03-13591, ATM 02-36945, ATM 05-48952, and MRI
AST 00-79482 and by NASA under grant NAG 5-13661.
Title: Active optical alignment of the Advanced Technology Solar
Telescope
Authors: Upton, Robert; Rimmele, Thomas; Hubbard, Robert
Bibcode: 2006SPIE.6271E..0RU
Altcode: 2006SPIE.6271E..27U
The Advanced Technology Solar Telescope (ATST) is a complex off-axis
Gregorian design to be used for solar astronomy. In order the counteract
the effects of mirror and telescope structure flexure, the ATST requires
an active optics alignment strategy. This paper presents an active
optics alignment strategy that uses three wavefront sensors distributed
in the ATST field-of-view to form a least-squares alignment solution
with respect to RMS wavefront error. The least squares solution is
realized by means of a damped least squares linear reconstructor. The
results of optical modelling simulations are presented for the ATST
degrees-of-freedom subject to random perturbations. Typical results
include residual RMS wavefront errors less than 20 nm. The results
quoted include up to 25 nm RMS wavefront sensor signal noise, random
figure errors on the mirrors up to 500 nm amplitude, random decenter
range up to 500 μm, and random tilts up to 10e - 03 degrees (36
arc-secs) range.
Title: The Interferometric Bidimensional Spectrometer (IBIS)
Authors: Cauzzi, Gianna; Cavallini, F.; Reardon, K.; Berrilli, F.;
Rimmele, T.; IBIS Team
Bibcode: 2006SPD....37.0608C
Altcode: 2006BAAS...38..226C
The Interferometric Bidimensional Spectrometer (IBIS) is an advanced
instrument for imaging spectroscopy installed at the Dunn Solar
Telescope at NSO/Sacramento Peak. The instrument has been constructed by
a consortium of italian institutes and allows for observations of the
photosphere and chromosphere at high spatial, spectral, and temporal
resolution. Such observations are essential for performing spatial
and spectral comparisons with numerical simulations. We will present
some of the performance characteristics of the instrument and show some
examples of the IBIS data. We will also show some initial results of the
recently tested polarimetric mode. IBIS is available for community use
as a facility instrument of NSO.IBIS has been funded by the Italian
Research Ministry (MIUR), the Italian Institute for Astrophysics
(INAF), and the Universities of Florence and Rome. Additional support
is provided by the National Solar Observatory.
Title: Multiwavelength Study of Flow Fields in Flaring Super Active
Region NOAA 10486
Authors: Deng, Na; Xu, Yan; Yang, Guo; Cao, Wenda; Liu, Chang; Rimmele,
Thomas R.; Wang, Haimin; Denker, Carsten
Bibcode: 2006ApJ...644.1278D
Altcode:
We present high-resolution observations of horizontal flow fields
measured by local correlation tracking from intensity images in three
wavelengths, i.e., G band (GB), white light (WL), and near-infrared
(NIR). The observations were obtained on 2003 October 29 within
the flaring super active region NOAA 10486, which was the source of
several X-class flares, including an X10 flare that occurred near
the end of the observing run. The data were obtained at National
Solar Observatory/Sacramento Peak (NSO/SP) using the newly developed
high-order adaptive optics (AO) system. We also use Dopplergrams
and magnetograms from MDI on board SOHO to study the line-of-sight
flow and magnetic field. We observe persistent and long-lived (at
least 5 hr) strong horizontal and vertical shear flows (both in the
order of 1 km s-1) along the magnetic neutral line (NL)
until the X10 flare occurred. From lower photospheric level (NIR),
the direction of the flows does not change up to the upper photosphere
(GB), while the flow speeds in the shear motion regions decrease and,
on the contrary, those in regions without shear motions increase with
increasing altitude. Right after the X10 flare, the magnetic gradient
decreased, while both horizontal and vertical shear flows dramatically
enhanced near the flaring NL. Our results suggest that photospheric
shear flows and local magnetic shear near the NL can increase after
the flare, which may be the result of shear release in the overlying
large-scale magnetic system or the reflection of a twisted or sheared
flux emergence carrying enough energy from the subphotosphere.
Title: Advanced Technology Solar Telescope: a progress report
Authors: Wagner, J.; Rimmele, T. R.; Keil, S.; Barr, J.; Dalrymple,
N.; Ditsler, J.; Goodrich, B.; Hansen, E.; Hegwer, S.; Hill, F.;
Hubbard, R.; Phelps, L.; Price, R.; Richards, K.; Warner, M.
Bibcode: 2006SPIE.6267E..09W
Altcode: 2006SPIE.6267E...9W
The four-meter Advanced Technology Solar Telescope (ATST) will be
the most powerful solar telescope and the world's leading resource
for studying solar magnetism that controls the solar wind, flares,
coronal mass ejections and variability in the Sun's output. Development
of a four-meter solar telescope presents many technical challenges
(e.g., thermal control of the enclosure, telescope structure and
optics). We give a status report of the ATST project (e.g., system
design reviews, instrument PDR, Haleakala site environmental impact
statement progress) and summarize the design of the major subsystems,
including the telescope mount assembly, enclosure, mirror assemblies,
wavefront correction, and instrumentation.
Title: Controlling wavefront distortions across a thermal boundary
Authors: Hubbard, Robert; Rimmele, Thomas; Schoening, William;
Dalrymple, Nathan; Poczulp, Gary; Warner, Mark
Bibcode: 2006SPIE.6267E..22H
Altcode: 2006SPIE.6267E..66H
We present the details of an experimental apparatus built to explore
wavefront distortion and its mitigation when an optical beam passes
from one thermal environment into another. The experiment simulates
a situation within the Advanced Technology Solar Telescope (ATST)
baseline design where the beam travels from an ambient-temperature
environment into a thermostatically controlled "room temperature"
environment. We found that an 8°C temperature difference between the
two environments introduces about 125 nm rms of wavefront distortion. A
double air curtain (one on each side of the boundary) reduces this to
about 30 nm rms. We also showed that the high-order (>1300 DoF)
adaptive optics system which is integral to the ATST design will be
able to further reduce this to about 5 nm rms, well within our initial
error budget.
Title: Site testing for the Advanced Technology Solar Telescope
Authors: Hill, F.; Beckers, J.; Brandt, P.; Briggs, J.; Brown, T.;
Brown, W.; Collados, M.; Denker, C.; Fletcher, S.; Hegwer, S.; Horst,
T.; Komsa, M.; Kuhn, J.; Lecinski, A.; Lin, H.; Oncley, S.; Penn,
M.; Radick, R.; Rimmele, T.; Socas-Navarro, H.; Streander, K.
Bibcode: 2006SPIE.6267E..1TH
Altcode: 2006SPIE.6267E..59H
The Advanced Solar Technology Telescope (ATST) is a 4-m solar telescope
being designed for high spatial, spectral and temporal resolution,
as well as IR and low-scattered light observations. The overall
limit of performance of the telescope is strongly influenced by the
qualities of the site at which it is located. Six sites were tested
with a seeing monitor and a sky brightness instrument for 1.5 to 2
years. The sites were Big Bear (California), Haleakala (Hawaii), La
Palma (Canary Islands, Spain), Panguitch Lake (Utah), Sacramento Peak
(New Mexico), and San Pedro Martir (Baja California, Mexico). In this
paper we will describe the methods and results of the site survey,
which chose Haleakala as the location of the ATST.
Title: The unique scientific capabilities of the Advanced Technology
Solar Telescope
Authors: Rimmele, T.; Keil, S.; Wagner, J.
Bibcode: 2006cosp...36.3186R
Altcode: 2006cosp.meet.3186R
The 4m Advance Technology Solar Telescope ATST will be the most powerful
solar telescope and the world s leading resource for studying solar
magnetism that controls the solar wind flares coronal mass ejections
and variability in the Sun s output An overview of the science goals
and observational requirements of the ATST and a brief summary of the
design status of the telescope and its instrumentation will be given As
its highest priority science driver ATST shall provide high resolution
and high sensitivity observations of the highly dynamic solar magnetic
fields throughout the solar atmosphere including the corona With its 4 m
aperture ATST will resolve features at 0 03 20km on the sun at visible
wavelengths The science requirement for polarimetric sensitivity 10 -5
relative to intensity and accuracy 5 times 10 -4 relative to intensity
place strong constraints on the polarization analysis and calibration
units 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 Coude lab facility We will emphasize the science that
the unique capabilities of the ground-based ATST will enable For
example the prospect of highly sensitive polarimetric observations in
the near-infrared and at longer infrared wavelengths at high spatial
resolution 0 08 1 6 micron that can be achieved from the ground in a
consistent manner over long periods of time is particularly exciting
Instruments can also be mounted at the Nasmyth focus For example
Title: Solar Site Survey for the Advanced Technology Solar
Telescope. I. Analysis of the Seeing Data
Authors: Socas-Navarro, H.; Beckers, J.; Brandt, P.; Briggs, J.;
Brown, T.; Brown, W.; Collados, M.; Denker, C.; Fletcher, S.; Hegwer,
S.; Hill, F.; Horst, T.; Komsa, M.; Kuhn, J.; Lecinski, A.; Lin, H.;
Oncley, S.; Penn, M.; Rimmele, T.; Streander, K.
Bibcode: 2005PASP..117.1296S
Altcode: 2005astro.ph..8690S
The site survey for the Advanced Technology Solar Telescope concluded
recently after more than 2 years of data gathering and analysis. Six
locations, including lake, island, and continental sites, were
thoroughly probed for image quality and sky brightness. The present
paper describes the analysis methodology employed to determine the
height stratification of the atmospheric turbulence. This information
is crucial, because daytime seeing is often very different between the
actual telescope aperture (~30 m) and the ground. Two independent
inversion codes have been developed to simultaneously analyze
data from a scintillometer array and a solar differential image
monitor. We show here the results of applying them to a sample subset
of data from 2003 May that was used for testing. Both codes retrieve a
similar seeing stratification through the height range of interest. A
quantitative comparison between our analysis procedure and actual in
situ measurements confirms the validity of the inversions. The sample
data presented in this paper reveal a qualitatively different behavior
for the lake sites (dominated by high-altitude seeing) and the rest
(dominated by near-ground turbulence).
Title: Advanced Technology Solar Telescope: a progress report
Authors: Rimmele, T. R.; Keil, S.; Wagner, J.; Dalrymple, N.; Goodrich,
B.; Hansen, E.; Hill, F.; Hubbard, R.; Phelps, L.; Richards, K.;
Warner, M.
Bibcode: 2005SPIE.5901...41R
Altcode:
The four-meter Advanced Technology Solar Telescope (ATST) will be
the most powerful solar telescope and the world's leading resource
for studying solar magnetism that controls the solar wind, flares,
coronal mass ejections and variability in the Sun's output. Development
of a four-meter solar telescope presents many technical challenges,
which include: thermal control of optics and telescope structure;
contamination control of the primary mirror to achieve low scattered
light levels for coronal observations; control of instrumental
polarization to allow accurate and precise polarimetric observations of
solar magnetic fields; and high-order solar adaptive optics that uses
solar granulation as the wavefront sensing target in order to achieve
diffraction limited imaging and spectroscopy. We give a status report
of the ATST project focusing on the substantial progress that has been
made with the design of the ATST. We summarize the design of the major
subsystems, including the enclosure, the primary and secondary mirror
assemblies, the coude and Nasmyth focal stations, adaptive optics and
instrumentation. The site selection has been successfully concluded
and we discuss areas where the site selection impacts the design.
Title: The ATST Site Survey
Authors: Hill, F.; Beckers, J.; Brandt, P.; Briggs, J. W.; Brown, T.;
Brown, W.; Collados, M.; Denker, C.; Fletcher, S.; Hegwer, S.; Horst,
T.; Komsa, M.; Kuhn, J.; Lecinski, A.; Lin, H.; Oncley, S.; Penn, M.;
Radick, R.; Rimmele, T.; Socas-Navarro, H.; Soltau, D.; Streander, K.
Bibcode: 2005AGUSMSP34A..04H
Altcode:
The Advanced Technology Solar Telescope (ATST) will be the world's
largest aperture solar telescope, and is being designed for high
resolution, IR, and coronal research. It must be located at a site that
maximizes the scientific return of this substantial investment. We
present the instrumentation, analysis and results of the ATST site
survey. Two instrumentation sets were deployed at each of six sites to
measure seeing as a function of height, and sky brightness as a function
of wavelength and off-limb position. Analysis software was developed
to estimate the structure function Cn2 as a function of height near
the ground, and the results were verified by comparison with in-situ
measurements. Additional software was developed to estimate the sky
brightness. The statistics of the conditions at the sites were corrected
for observing habits and the annualized hours of specific observing
conditions were estimated. These results were used to identify three
excellent sites suitable to host the ATST: Haleakala, Big Bear and La
Palma. Among them, Haleakala is proposed as the optimal location of
the ATST, La Palma and Big Bear being viable alternative sites.
Title: On the Relation Between Flow Fields and Magnetic Field
Evolution in Flare Productive NOAA Active Region 10486
Authors: Deng, N.; Xu, Y.; Yang, G.; Cao, W.; Rimmele, T. R.; Wang,
H.; Denker, C.
Bibcode: 2005AGUSMSP51C..05D
Altcode:
We present high resolution observations of flow fields within solar NOAA
active region 10486 before an X10 flare on October 29, 2003. From 2003
October 28 to November 4, a complex δ-sunspot located in NOAA 10486
produced dramatic flare activities in the descending phase of the solar
cycle 23. The flow fields are measured by local correlation tracking
(LCT) based on speckle masking white-light images, near-infrared (NIR)
continuum images at 1.56 μm, and G-band images obtained with the Dunn
Solar Telescope (DST) of the National Solar Observatory/Sacramento Peak
(NSO/SP). NSO's newly developed high-order adaptive optics system at
the DST was used to achieve diffraction-limited imaging with a high
signal-to-noise ratio. The spatial resolution of the images approaches
the diffraction limit of the 76 cm aperture DST of about 0.14 ″ at
527 nm. In addtion, we use longitudinal magnetograms from the Michelson
Doppler Imager (MDI) on board the Solar and Heliospheric Observatory
(SoHO) to study the evolution of photospheric magnetic field and
its correlation with flow fields in this flare productive active
region. We link strong magnetic shear and fast emergence of magnetic
flux to photospheric flows, which might trigger the flares. Our result
suggests that the time-series analysis of the photospheric flow fields
is a critical observational diagnostic for the evolution of magnetic
fields in solar active regions. This work was supported by NSF under
grant ATM 03-42560, ATM 03-13591, ATM 02-36945, and MRI AST 00-79482
and by NASA under grant NAG 5-13661.
Title: Design of the Advanced Technology Solar Telescope
Authors: Wagner, J.; Rimmele, .; Keil, S.
Bibcode: 2005AGUSMSP34A..02W
Altcode:
The ATST is a 4-m aperture, off-axis solar telescope with integrated
adaptive optics, low-scattered light, infrared, coronagraphic,
and polarimetric capabilities. We present an overview of the ATST
design. The ATST design has progressed in to the point where the project
is ready to lead contracts for construction of major subsystems. These
subsystems include the enclosure, the telescope mount assembly, and
the primary and secondary mirror assemblies. We summarize the design
concepts of the major telescope components. Thermal control of telescope
structure and optical components to ambient temperature has been a
major design focus. Where applicable, the conditions at the selected
site, Haleakala, have been worked into the designs. The design of the
wavefront control system that integrates telescope alignment functions,
active control of the primary and high order adaptive optics will be
summarized. A vigorous systems engineering approach has been implemented
to ensure that the telescope will deliver the diffraction limited
imaging performance specified in the Science Requirements Document.
Title: First-Light Instrumentation for the Advanced Technology
Solar Telescope
Authors: Rimmele, T.; Balasubramaniam, K.; Berger, T.; Elmore, D.;
Gary, A.; Keller, C.; Kuhn, J.; Lin, H.; Mickey, D.; Pevtsov, A.;
Robinson, B.; Sigwarth, M.; Soccas-Navarro, H.
Bibcode: 2005AGUSMSP34A..03R
Altcode:
The 4m Advanced Technology Solar Telescope (ATST) is the next
generation ground based solar telescope. In this paper we provide
an overview of the ATST post-focus instrumentation. The majority of
ATST instrumentation is located in an instrument Coude lab facility,
where a rotating platform provides image de-rotation. A high order
adaptive optics system delivers a corrected beam to the Coude lab
facility. Alternatively, instruments can be mounted at the Nasmyth
focus. For example, instruments for observing the faint corona
preferably will be mounted at Nasmyth where maximum throughput
is achieved. In addition, the Nasmyth focus has minimum telescope
polarization and minimum stray light. We give an overview of the
initial set of first generation instruments: the Visible-Light
Broadband Imager (VLBI), the Visible Spectro-Polarimeter (ViSP),
the Near-IR Spectro-Polarimeter (NIRSP), which includes a coronal
module, and the Visible Tunable Filter. We also discuss the unique and
efficient approach to the ATST instrumentation, which builds on the use
of common components such as detector systems, polarimetry packages
and various opto-mechanical components. For example, the science
requirement for polarimetric sensitivity (10-5 relative to intensity)
and accuracy (5'10-4 relative to intensity) place strong constraints
on the polarization analysis and calibration units. Consequently,
these systems are provided at the facility level, rather than making
it part of the requirement for each instrument.
Title: Overview and Status Report on the Advanced Technology Solar
Telescope
Authors: Keil, S. L.; Rimmele, T.; Wagner, J.; ATST Team
Bibcode: 2005AGUSMSP34A..01K
Altcode:
The ATST is a 4-m aperture, off-axis solar telescope with integrated
adaptive optics, low-scattered light, infrared, coronagraphic, and
polarimetric capabilities. It will resolve the essential, fine-scale
magnetic features and their dynamics that dictate the varying release
of energy from the Sun's atmosphere. The ATST design is optimized in
terms of throughput, scattered light, and instrumental polarization
properties to perform precision vector magnetic field measurements down
to its diffraction limit (0.03 arcsec at 500 nm) and throughout the
solar atmosphere. Its collecting area, which is a factor of 16 greater
than today's solar telescopes, will provide the sensitivity to measure
both weak fields and rapidly evolving stronger fields. It has a factor
of 64 greater collecting area than the largest existing coronagraph,
and will provide the sensitivity and coronagraphic capability needed
to measure the weak, fine-scale coronal magnetic fields. With adaptive
optics and a set of facility class instrumentation the ATST will be
the worlds leading resource for studying solar magnetism. ATST will
be the successor to the solar telescopes built in the 1960s and 1970s,
and is a natural complement to planned space missions. Starting in late
2001, ATST began a design and development phase. To date the D&D
phase has produced and refined a science requirements document and a
conceptual design that would meet those requirements. A conceptual
design review was held in August of 2003. Following the review, a
construction proposal, including a complete work breakdown structure
and cost, was submitted in early 2004 and was successfully peer
reviewed. NSF astronomy is now in the process of submitting ATST to
the NSF Major Research Equipment and Facilities Construction program
review process. During the D&D phase, a thorough site survey was
also conducted resulting in Haleakala as the site best able to fulfill
the ATST science requirements. We present a brief overview of the ATST
program, how it fits into the broader picture of solar facilities and
capabilities, and discuss the current status of the ATST project and
plans for constructing and commissioning the ATST.
Title: Long Exposure Point Spread Function Estimation from Adaptive
Optics Loop Data
Authors: Marino, J.; Rimmele, T.; Christou, J.
Bibcode: 2005AGUSMSP51A..01M
Altcode:
Current work in Solar Physics requires high resolution observations
from ground based telescopes. However, the performance of any ground
based telescope is ultimately limited by optical aberrations produced
by atmospheric turbulence. Adaptive Optics (AO) is a powerful tool
that artially corrects for these optical aberrations in real time,
considerately improving the image quality. Wavefront sensor and mirror
data produced by the AO system during closed loop operation contains
information about correction performance and seeing conditions. We
present a method to estimate the Long Exposure Point Spread Function
(LEPSF) of the AO corrected image using AO loop data. This estimation
can then be used to improve image quality using deconvolution
post-processing techniques. In Solar Physics observations seeing
conditions are highly variable. Thus, an estimation of the LEPSF is only
useful if it corresponds to the exact time an image was taken. LEPSFs
produced by this method are simultaneous with the captured AO corrected
image. We will apply this method to time series of intensity images,
velocity maps and line of sight magnetic field of sunspots and
pores. Obtaining high resolution AO and post-facto corrected data with
homogeneous image quality and more reliable quantitative measurements.
Title: High-Spatial-Resolution Imaging Combining High-Order Adaptive
Optics, Frame Selection, and Speckle Masking Reconstruction
Authors: Denker, Carsten; Mascarinas, Dulce; Xu, Yan; Cao, Wenda;
Yang, Guo; Wang, Haimin; Goode, Philip R.; Rimmele, Thomas
Bibcode: 2005SoPh..227..217D
Altcode:
We present, for the first time, high-spatial-resolution observations
combining high-order adaptive optics (AO), frame selection, and
post-facto image correction via speckle masking. The data analysis is
based on observations of solar active region NOAA 10486 taken with the
Dunn Solar Telescope (DST) at the Sacramento Peak Observatory (SPO) of
the National Solar Observatory (NSO) on 29 October 2003. The high Strehl
ratio encountered in AO corrected short-exposure images provides highly
improved signal-to-noise ratios leading to a superior recovery of the
object's Fourier phases. This allows reliable detection of small-scale
solar features near the diffraction limit of the telescope. Speckle
masking imaging provides access to high-order wavefront aberrations,
which predominantly originate at high atmospheric layers and are only
partially corrected by the AO system. In addition, the observations
provided qualitative measures of the image correction away from the
lock point of the AO system. We further present a brief inspection
of the underlying imaging theory discussing the limitations and
prospects of this multi-faceted image reconstruction approach in
terms of the recovery of spatial information, photometric accuracy,
and spectroscopic applications.
Title: Photospheric Shear Flows along the Magnetic Neutral Line of
Active Region 10486 prior to an X10 Flare
Authors: Yang, Guo; Xu, Yan; Cao, Wenda; Wang, Haimin; Denker, Carsten;
Rimmele, Thomas R.
Bibcode: 2004ApJ...617L.151Y
Altcode:
We present high spatial resolution observations of proper motions in
the solar NOAA Active Region 10486 using a high-order adaptive optics
system, frame selection, and speckle-masking image reconstruction. The
data were obtained with the Dunn Solar Telescope of the National Solar
Observatory/Sacramento Peak on 2003 October 29. The resolution of the
images approaches the diffraction-limited resolution of the Dunn Solar
Telescope of about 0.14" at 527 nm. We analyzed a 2 hr time series with
a 1 minute cadence prior to an X10 white-light flare. Local correlation
tracking was used to measure the photospheric proper motions. We find
specific evidence of strong shear flows along the magnetic neutral line;
these shear flows are well defined and correlated with white-light
flare kernels in the visible and infrared. The speed along the flow
channels can reach up to 1.6 km s-1, and the separation of
channels with head-on flows can be less than 1". Counterstreaming and
complex flow patterns have been distinguishing characteristics of this
extraordinarily flare-productive active region.
Title: Solar multiconjugate adaptive optics at the Dunn Solar
Telescope: preliminary results
Authors: Langlois, Maud; Moretto, Gil; Richards, Kit; Hegwer, Steve;
Rimmele, Thomas R.
Bibcode: 2004SPIE.5490...59L
Altcode:
We report here the preliminary results obtained with the multi-conjugate
adaptive optics (MCAO) system at the Dunn Solar Telescope (DST/NSO
MCAO) and the optical setup and performances are presented in more
details in Moretto et al. in this proceeding. This system relies on
the tomography technique, in which three WFS are used, each of them
coupled to extended images of the Sun"s granulation and/or sunspots,
to retrieve a 3D measurement of the turbulent volume in order to
command the two DMs. We used a 5x5 subaperture Shack-Hartmann with
cross correlation applied on three selected guiding regions - 18"
wide- within the 1.25' full FOV. We also report on the estimation of
turbulence distribution and the future MCAO performances based on a
separate tomographic wavefront sensing experiment using the Dunn Solar
Telescope adaptive optics system. In addition, we obtained estimates
of the turbulence distribution. The results from this article provides
an important step forward for building a full solar multi-conjugate
adaptive optics system for the Dunn Solar Telescope and in the long
term for the future 4 meter ATST telescope.
Title: Optical set-up and design for solar multiconjugate adaptive
optics at Dunn Solar Telescope/NSO
Authors: Moretto, Gil; Langlois, Maud; Richards, Kit; Hegwer, Steve;
Gilliam, Doug; Rimmele, Thomas R.
Bibcode: 2004SPIE.5490..905M
Altcode:
The Sun is an ideal target for the development and application of
Multi-Conjugate Adaptive Optics (MCAO). A solar MCAO system is being
developed by the National Solar Observatory, Adaptive Optics Project,
with the purpose of extending the corrected science field of view to
1.25Arcmin. A detailed optical set-up, design and optical performance
for such a system is presented and discussed here. The preliminary
results for this first MCAO/DST run, are presented in more details by
Langlois et al [1] at this conference.
Title: Long-exposure point spread function estimation from adaptive
optics loop data
Authors: Marino, Jose; Rimmele, Thomas R.; Christou, Julian C.
Bibcode: 2004SPIE.5490..184M
Altcode:
Adaptive Optics (AO) systems provide real time correction for
atmospherical aberrations. They have become an indispensable tool
for ground based astronomical observations. However, correction
provided by AO is only partial. Further correction can be achieved
using post-processing techniques. Post-processing techniques such as
deconvolution rely on a good estimation of the long exposure Point
Spread Function (PSF). In the case of Solar Physics obtaining a
long exposure PSF can be particularly difficult due to the lack of
point sources in the field of view and the highly variable seeing
conditions. We present a method to estimate the long exposure PSF
of an AO corrected image using AO loop data. AO closed loop data
provides enough information about the residual aberrations that were
not corrected by the system and about the seeing conditions present
at a certain time. With this information an estimated long exposure
PSF can be constructed for each captured image. The PSF can be used to
deconvolve the images. We will be presenting first results of applying
this method to solar images.
Title: Advanced Technology Solar Telescope: conceptual design
and status
Authors: Keil, Stephen; Oschmann, Jacobus M., Jr.; Rimmele, Thomas R.;
Hubbard, Rob; Warner, Mark; Price, Ron; Dalrymple, Nathan; Goodrich,
Bret; Hegwer, Steven; Hill, Frank; Wagner, Jeremy
Bibcode: 2004SPIE.5489..625K
Altcode:
The Advance Technology Solar Telescope (ATST) has finished its
conceptual design stage, submitted a proposal for construction funding
and is working towards a system level preliminary design review later
this year. The current concept (including integrated adaptive optics
and instrumentation) will be reviewed with concentration on solutions
to the unique engineering challenges for a four meter solar telescope
that have been previously presented. The overall status will be given
with a concentration on near term milestones and impact on final
completion targeted in 2012.
Title: Solar site testing for the Advanced Technology Solar Telescope
Authors: Hill, Frank; Beckers, Jacques; Brandt, Peter; Briggs, John;
Brown, Timothy; Brown, W.; Collados, Manuel; Denker, Carsten; Fletcher,
Steven; Hegwer, Steven; Horst, T.; Komsa, Mark; Kuhn, Jeff; Lecinski,
Alice; Lin, Haosheng; Oncley, Steve; Penn, Matthew; Rimmele, Thomas
R.; Socas-Navarro, Hector; Streander, Kim
Bibcode: 2004SPIE.5489..122H
Altcode:
The location of the Advanced Technology Solar Telescope (ATST) is a
critical factor in the overall performance of the telescope. We have
developed a set of instrumentation to measure daytime seeing, sky
brightness, cloud cover, water vapor, dust levels, and weather. The
instruments have been located at six sites for periods of one to two
years. Here we describe the sites and instrumentation, discuss the
data reduction, and present some preliminary results. We demonstrate
that it is possible to estimate seeing as a function of height near the
ground with an array of scintillometers, and that there is a distinct
qualitative difference in daytime seeing between sites with or without
a nearby lake.
Title: Recent advances in solar adaptive optics
Authors: Rimmele, Thomas R.
Bibcode: 2004SPIE.5490...34R
Altcode:
Solar adaptive optics has become an indispensable tool at ground
based solar telescopes. Over the last few years several solar
adaptive optics systems have been deployed at major ground based solar
telescopes. These systems enable diffraction limited observations of
the sun for a significant fraction of the available observing time
at these telescopes. New ground breaking scientific results have been
achieved with solar adaptive optics. This paper summarizes the recent
progress in the field of solar adaptive optics.
Title: Optical design for a Fabry-Perot image interferometer for
solar observations
Authors: Moretto, Gilberto; Gary, G. Allen; Balasubramaniam, K. S.;
Rimmele, Thomas R.
Bibcode: 2004SPIE.5492.1773M
Altcode:
We outline here a preliminary optical design study for a telecentric
tunable Fabry-Perot etalon system. The first result of the optical
optimization into a design, which delivers performance image quality
and telecentricity, is presented here. Bearing in mind the possible
use of such a study design - as a possible instrument for the Advanced
Technology Solar Telescope (ATST) - we also show that a hybrid design
strategy delivers a compact design that will fit inside the ATST's
Coude optical tables.
Title: Instrumentation for the Advanced Technology Solar Telescope
Authors: Rimmele, Thomas R.; Hubbard, Robert P.; Balasubramaniam,
K. S.; Berger, Tom; Elmore, David; Gary, G. Allen; Jennings, Don;
Keller, Christoph; Kuhn, Jeff; Lin, Haosheng; Mickey, Don; Moretto,
Gilberto; Socas-Navarro, Hector; Stenflo, Jan O.; Wang, Haimin
Bibcode: 2004SPIE.5492..944R
Altcode:
The 4-m aperture Advanced Technology Solar Telescope (ATST) is the
next generation ground based solar telescope. In this paper we provide
an overview of the ATST post-focus instrumentation. The majority of
ATST instrumentation is located in an instrument Coude lab facility,
where a rotating platform provides image de-rotation. A high order
adaptive optics system delivers a corrected beam to the Coude lab
facility. Alternatively, instruments can be mounted at Nasmyth or
a small Gregorian area. For example, instruments for observing the
faint corona preferably will be mounted at Nasmyth focus where maximum
throughput is achieved. In addition, the Nasmyth focus has minimum
telescope polarization and minimum stray light. We describe the set of
first generation instruments, which include a Visible-Light Broadband
Imager (VLBI), Visible and Near-Infrared (NIR) Spectropolarimeters,
Visible and NIR Tunable Filters, a Thermal-Infrared Polarimeter &
Spectrometer and a UV-Polarimeter. We also discuss unique and efficient
approaches to the ATST instrumentation, which builds on the use of
common components such as detector systems, polarimetry packages and
various opto-mechanical components.
Title: Diagnostic spectroscopy of G-band brightenings in the
photosphere of the sun
Authors: Langhans, K.; Schmidt, W.; Rimmele, T.
Bibcode: 2004A&A...423.1147L
Altcode:
A detailed analysis of high-resolution spectra obtained in three
different wavelength regions (at 430 nm, 526 nm and 569 nm) of G-band
bright points in the solar photosphere is presented. They show an
average intensity contrast of 11% with respect to the ``quiet'' sun
reference. The CH lines are weakened in the bright point interior. The
atomic lines, too, e.g. the Fe I line at 569.15 nm, weaken in the bright
point interior. In contrast thereto, the absorption line of single
ionized iron at 526.48 nm remains almost constant between bright point
interior and the immediate surroundings. Line-of-sight velocities show a
stronger downflow within bright points than in the close environment. A
net downflow relative to the intergranular surroundings of around 80
m/s is measured. Filling factors are calculated from a comparison with
synthesized spectra for different flux tube models and are used to
estimate the ``true'' velocity in bright points with respect to their
immediate surroundings. We obtain up- and downflows in the order of one
km s-1, in agreement with the magneto-convective picture of
the formation and dispersal of magnetic flux tubes. From the different
behavior of the metallic lines and the CH lines we conclude that the
line-weakening process that leads to the G-band bright points is mainly
due to hot-wall radiation. This confirms that these bright points are
indeed magnetic flux elements.
Title: Evaluation of Seeing-Induced Cross Talk in Tip-Tilt-Corrected
Solar Polarimetry
Authors: Judge, Philip G.; Elmore, David F.; Lites, Bruce W.; Keller,
Christoph U.; Rimmele, Thomas
Bibcode: 2004ApOpt..43.3817J
Altcode:
We reanalyze the effects of atmosphere-induced image motions on the
measurement of solar polarized light using a formalism developed by
Lites. Our reanalysis is prompted by the advent of adaptive optics (AO)
systems that reduce image motion and higher-order aberrations, by the
availability of liquid crystals as modulation devices, and by the need
to understand how best to design polarimeters for future telescopes
such as the Advanced Technology Solar Telescope. In this first attempt
to understand the major issues, we analyze the influence of residual
image motion (tip-tilt) corrections of operational AO systems on the
cross talk between Stokes parameters and present results for several
polarization analysis schemes. Higher-order wave-front corrections are
left for future research. We also restrict our discussion to the solar
photosphere, which limits several important parameters of interest,
using some recent magnetoconvection simulations.
Title: Latest Results from the ATST Site Survey
Authors: Hill, F.; Collados, M.; Navarro, H.; Beckers, J.; Brandt,
P.; Briggs, J.; Brown, T.; Denker, C.; Hegwer, S.; Horst, T.; Komsa,
M.; Kuhn, J.; Lin, H.; Oncley, S.; Penn, M.; Rimmele, T.; Soltau,
D.; Streander, K.
Bibcode: 2004AAS...204.6909H
Altcode: 2004BAAS...36..795H
We present the latest results and current status of the site survey
portion of the Advanced Technology Solar Telescope (ATST) project. The
ATST will provide high resolution solar data in the visible and IR. The
site is a major factor determining the performance of the telescope. The
most critical site characteristics are the statistics of daytime seeing
quality and sky clarity. These conditions are being measured by a suite
of instruments at three sites (Big Bear, Haleakala, La Palma). These
sites were chosen from a set of six that have been tested starting in
November 2001. The instrumentation includes a solar differential image
motion monitor, an array of scintillometers, a miniature coronagraph,
a dust monitor, and a weather station. The analysis of the data provides
an estimate of the seeing as a function of height near the ground. We
will present the latest results of the analysis of the survey data set.
Title: High resolution flare observations using adaptive optics
Authors: Rimmele, T.; Sankarasubramanian, K.
Bibcode: 2004AAS...204.2701R
Altcode: 2004BAAS...36..693R
We present a time sequence of a flare observed on October 23, 2003
in active region NOAA 0486 near the east limb. The same active region
produced the huge flare on October 29, 2003. The Universal Birefringened
Filter (UBF) was used to record narrow band filtergrams in H-α and
the iron line FeI 5434. The Diffraction-Limited Spectro- Polarimeter
(DLSP) performed vector magnetic field measurements before and after
the flare. The high order adaptive optics system provided diffraction
limited imaging during a large fraction of the time during which
the flare was observed. The dynamic H-α core flare sequence,
during which a super-penumbral loop system erupts, will be shown. We
were able to resolve finestructure in the flare ribbons at scales of
0.2". Footpoints of loops as well as individual loop tops are seen to
brighten as the loop system erupts. To our knowledge for the first time
we observe flare structure at spatial scales of 0.2" - the diffraction
limit of the DST. H-α wing dopplergrams show structure on similar
spatial scales. The signature of the flare is also seen in the core of
the line FeI 5434 Å, which forms in the upper photosphere. Comparing
DLSP vector magnetograms before and after the flare we find evidence
of flux cancellation at small spatial scales.
Title: Diffraction Limited Spectro-Polarimetry at the Dunn Solar
Telescope
Authors: Sankarasubramanian, K.; Rimmele, T. R.; Lites, B. W.
Bibcode: 2004AAS...204.2006S
Altcode: 2004BAAS...36..686S
The Diffraction Limited Spectro-Polarimeter (DLSP) is a collaborative
project between the National Solar Observatory (NSO) and the
High-Altitude Observatory (HAO). This new instrument, along with the
high-order Adaptive Optics (AO-76) system (which is being developed
at the NSO) has been used to measure magnetic fields on the solar
photosphere at the highest spatial resolution (0.2 arcsec which is
the diffraction limit of the DST at the 630.0nm wavelength). A few
preliminary results obtained from the first observing run with this
instrument are, (1) The fine structures present inside the sunspot
umbra (like the umbral dots) show upflows and reduced field strengths
compared to the surrounding umbra. (2) The sizes of these umbral
fine structures goes down to the diffraction limit of the DST (about
0.2 arcsec). This result confirms that the instrument did achieve
its full capability. (3) There are small-scale convective up and
down flows in the light bridges. The strength of these flow is about
a km/sec. The field strengths are smaller in these regions compared to
the surrounding umbra. At some places in the light bridges, the field
strengths are as small as half of the umbral field strength. (4)
There are small-scale upflows in the inner penumbra of the observed
sunspot. These regions coincide with the inner foot-point of the bright
penumbral filaments as seen in the continuum intensity map. Some of
these upflow regions also show a reduced field strength.
Title: Multiconjugation Optical Relay for an Off-Axis Solar Telescope
Authors: Moretto, Gil; Langlois, Maud; Rimmele, Thomas R.
Bibcode: 2004PASP..116..441M
Altcode:
The Sun is an ideal object for the development and application of
multiconjugate adaptive optics (MCAO). An effort to develop solar
MCAO is pursued by the National Solar Observatory (NSO) Adaptive
Optics Project. In developing solar MCAO, we bear in mind its possible
implementation into the proposed 4 m Advanced Technology Solar Telescope
(ATST). Two possible relay optical designs feeding an MCAO section
and the coudé section of a 4 m off-axis solar telescope, such as the
proposed ATST, are presented and discussed here.
Title: High-Spatial Resolution Observations of Flow Fields in Solar
Active Region NOAA 10486
Authors: Yang, G.; Xu, Y.; Cao, W.; Wang, H.; Denker, C.; Rimmele,
T. R.
Bibcode: 2004AAS...204.0210Y
Altcode: 2004BAAS...36..669Y
We present high-spatial resolution observations of proper motions in
solar active region NOAA 10486 using the newly developed high-order
adaptive optics (AO) system at the Dunn Solar Telescope (DST) of the
National Solar Observatory/Sacramento Peak (NSO/SP) on 2003 October
29. The images were obtained with high-order AO, frame selection, and
speckle masking image reconstruction. We analyze a two hour time series
with 1-minute cadence in the context of an X10 white-light flare. Local
correlation tracking (LCT) was used to measure the horizontal proper
motions in the photosphere and relate them to the strong shear observed
in the magnetic field configuration.
Title: Plasma Flows Observed in Magnetic Flux Concentrations and
Sunspot Fine Structure Using Adaptive Optics
Authors: Rimmele, Thomas R.
Bibcode: 2004ApJ...604..906R
Altcode:
We present diffraction-limited observations of magnetic flux
concentrations and penumbral and umbral fine structure within an
active region observed at disk center. We recorded G-band images,
magnetograms, Dopplergrams, and narrowband filtergrams, using the
Universal Birefringent Filter (UBF) at the Dunn Solar Telescope
(DST). The National Solar Observatory (NSO) adaptive optics system at
the DST was used to achieve diffraction-limited long-exposure imaging
with a high signal-to-noise ratio. The main results can be summarized
as follows: Strong and spatially narrow downflows are observed at
the edge of magnetic structures, such as small flux concentrations
(sometimes also referred to as flux tubes), pores, a light bridge,
and the sunspot umbrae. For the particular sunspot observed, we find
strong evidence for what appear to be vigorous, small-scale convection
patterns in a light bridge. We observe extremely narrow (<0.2")
channels or sheets of downflowing plasma. Flux concentrations as seen in
intensity expand from a height close to where the continuum is formed
to the height of formation for the G band. These observations indicate
that the G band forms in the mid-photosphere. We are able to identify
individual penumbral fibrils in our data and find a bright (hot) upflow
and a more vertical field structure at the filament footpoint near
the umbral boundary. The observations are consistent with a filament
geometry in which the field and flow turn to a nearly horizontal, dark
structure over a distance of about 0.2". In the deep photosphere we
observe strong upflows of the order of 1 km s-1 in umbral
dots. We compare our results with theoretical model predictions.
Title: The Diffraction Limited Spectro-Polarimeter: a new instrument
for high-resolution solar polarimetry
Authors: Sankarasubramanian, K.; Gullixson, Craig; Hegwer, Stephen;
Rimmele, Thomas R.; Gregory, Scott; Spence, Tony; Fletcher, Stephen;
Richards, Kit; Rousset, Emilie; Lites, Bruce; Elmore, David; Streander,
Kim; Sigwarth, Michael
Bibcode: 2004SPIE.5171..207S
Altcode:
The National Solar Observatory in collaboration with the High-Altitude
Observatory is developing a new solar polarimeter, the Diffraction
Limited Spectro-Polarimeter. In conjunction with a new high-order
adaptive optics system at the NSO Dunn Solar Telescope, the DLSP
design facilitates very high angular resolution observations of
solar vector magnetic fields. This project is being carried out in two
phases. As a follow-on to the successful completion of the first phase,
the ongoing DLSP Phase II implements a high QE CCD camera system,
a ferro-electric liquid crystal modulator, and a new opto-mechanical
system for polarization calibration. This paper documents in detail the
development of the modulator system and its performance, and presents
preliminary results from an engineering run carried out in combination
with the new NSO high-order AO system.
Title: Advanced Technology Solar Telescope: a progress report
Authors: Oschmann, Jim; Dalrymple, Nathan; Warner, Mark; Price, Ron;
Hill, Frank; Hubbard, Rob; Rimmele, Thomas R.; Keller, Christoph U.;
Keil, Stephen
Bibcode: 2004SPIE.5171..160O
Altcode:
The 4m ATST will be the most powerful solar telescope in the world,
providing a unique scientific tool to study the Sun and other
astronomical objects. The design and development phase for the Advance
Technology Solar Telescope (ATST) is progressing. The conceptual design
review (CoDR) for the ATST is scheduled for August 2003. We present a
brief description of the science requirements of ATST, and remind the
reader of some of the technical challenges of building a 4-m solar
telescope. We will discuss some of the design strategies that will
allow us to achieve the required performance specifications, present
conceptual designs for the ATST, and summarize the results of trades
we have made on our path to the CoDR. The thermal impacts to local,
self-induced seeing with respect to some of our system level trades
that have been completed will be discussed.
Title: Development of SCIDAR for solar observations
Authors: Beckers, Jacques M.; Rimmele, Thomas R.
Bibcode: 2004SPIE.5171..195B
Altcode:
In nighttime astronomy Vernin and co-workers have proposed and
subsequently developed the so-called SCIDAR (SCIntillation Detection
And Ranging) technique to probe Cn2(h). It makes
use of the double shadow band (or scintillation) pattern formed on
a telescope aperture by the two components of a binary star. We are
developing a variant of this technique for solar astronomy. It uses
pairs of small apertures on the solar image with diameters smaller
than the isoplanatic patch ("artificial double stars"). Within
the isoplanatic patch the complex amplitude (intensity and phase)
of the atmospheric wavefront disturbances is constant. Solar SCIDAR
(or S-SCIDAR) makes use of this. We will present the results of the
first (inconclusive) experiments of this S-SCIDAR technique as used on
the 76 cm aperture Dunn Solar Telescope (DST) and the 152 cm aperture
McMath-Pierce facility (McM-P) of the US National Solar Observatory. It
uses a 45 x 45 lenslet array placed in the solar image. The size of
the lenslets corresponds to 2.25 x 2.25 arcsec at the DST and 1.67 x
1.67 arcsec at the McM-P; the separation of lenslet pairs on the DST
(and hence of the separations of the artificial double stars) ranges
from 2.25 arcsec to 140 arcsec. The lenslet array forms an array of
pupil images on a CCD detector.
Title: Multi-Conjugate Adaptive Optics - relay optical designs for
a 4-m off-axis solar telescope
Authors: Moretto, Gilberto; Rimmele, Thomas R.; Langlois, Maud
Bibcode: 2004SPIE.5171..171M
Altcode:
The Sun is an ideal object for the development and application of
Multi-Conjugate Adaptive Optics (MCAO). An effort to develop solar MCAO
is pursued by the NSO"s Adaptive Optics Project. In developing solar
MCAO we bear in mind its possible implementation into the proposed
4-M Advanced Technology Solar Telescope (ATST). Two possible relay
optical designs feeding a MCAO section and the Coudé section of a
4-M off-axis solar telescope, such as the proposed ATST, are presented
and discussed here.
Title: First results from the NSO/NJIT solar adaptive optics system
Authors: Rimmele, Thomas R.; Richards, Kit; Hegwer, Stephen; Fletcher,
Stephen; Gregory, Scott; Moretto, Gilberto; Didkovsky, Leonid V.;
Denker, Carsten J.; Dolgushin, Alexander; Goode, Philip R.; Langlois,
Maud; Marino, Jose; Marquette, William
Bibcode: 2004SPIE.5171..179R
Altcode:
The National Solar Observatory and the New Jersey Institute of
Technology have developed two 97 actuator solar adaptive optics
(AO) systems based on a correlating Shack-Hartmann wavefront sensor
approach. The first engineering run was successfully completed
at the Dunn Solar Telescope (DST) at Sacramento Peak, New Mexico
in December 2002. The first of two systems is now operational at
Sacramento Peak. The second system will be deployed at the Big Bear
Solar Observatory by the end of 2003. The correlating Shack-Hartmann
wavefront sensor is able to measure wavefront aberrations for
low-contrast, extended and time-varying objects, such as solar
granulation. The 97-actuator solar AO system operates at a loop
update rate of 2.5 kHz and achieves a closed loop bandwidth (0dB
crossover error rejection) of about 130 Hz. The AO system is capable
of correcting atmospheric seeing at visible wavelengths during median
seeing conditions at both the NSO/Sacramento Peak site and the Big Bear
Solar Observatory. We present an overview of the system design. The
servo loop was successfully closed and first AO corrected images were
recorded. We present first results from the new, high order AO system.
Title: High speed low latency solar adaptive optics camera
Authors: Richards, Kit; Rimmele, Thomas R.; Hill, Reuben; Chen, Jianxin
Bibcode: 2004SPIE.5171..316R
Altcode:
This paper describes a versatile camera designed to operate at high
frame rates of > 2kHz. Such high frame rates are required to reduce
the latency, i.e., achieve high bandwidth in a solar adaptive optics
application. The camera was designed around a 1280x1024 pixel CMOS
10-bit sensor with a readout rate of 2 microseconds per row. The
output is switchable between a standard Camera Link interface with
four 10-bit ports (standard camera mode) and a non-standard Camera
Link interface with twelve 8-bit ports (adaptive optics mode). The
programmable camera interface maps blocks of pixels to output ports
enabling multiple regions of interest. This mode is of particular
interest for solar multi-conjugate adaptive optics (MCAO). The speed
of the camera is determined by the number of rows of pixels needed
in the application. For example, a 200x200 pixel sub-array that is
needed for the 97-actuator solar adaptive optics system at the Dunn
Solar Telescope can be read out at a rate of 2.5kHz. Camera design
and performance will be discussed.
Title: Three-dimensional high-order wavefront sensing, anisoplanatism,
and evaluation of the feasibility of solar MCAO
Authors: Langlois, Maud; Rimmele, Thomas R.; Moretto, Gilberto
Bibcode: 2004SPIE.5171..187L
Altcode:
Multiconjugate adaptive optics has been proposed in order to
extend the size of the corrected field of view with respect to
the classical AO field of view. In order to achieve this, a three
dimensional measurement of the turbulent volume is needed to collect
the information to command the several deformable mirrors. This can
be done by using tomography, in which several WFS are used, each
of them coupled to a sky region. Here we report the experimental
demonstration of such evaluation for solar observations. In addition,
we confront these results on turbulence distribution with a study of
AO corrected images by using multi point large field of view wavefront
sensing with the new Dunn Solar Telescope adaptive optics system. This
yields to information on the AO system performances and provide useful
estimate of the PSF variation across the field. The results from this
article provides an important step forward for building a full solar
multi-conjugate adaptive optics system for the Dunn Solar Telescope
and in a longer term for the future 4 meter ATST telescope.
Title: Science Goals and Development of the Advanced Technology
Solar Telescope
Authors: Keil, S. L.; Rimmele, T. R.; Oschmann, J.; Hubbard, R.;
Warner, M.; Price, R.; Dalrymple, N.; Atst Team
Bibcode: 2004IAUS..223..581K
Altcode: 2005IAUS..223..581K
The Advanced Technology Solar Telescope (ATST) will perform
high-resolution studies of the Sun's magnetic fields needed to
understand their role in the fundamental processes responsible for solar
variability. The generation of magnetic fields through dynamo processes,
the amplification of fields through the interaction with plasma flows,
and the destruction of fields remain poorly understood. There is
incomplete insight as to what physical mechanisms are responsible for
heating the corona, what causes variations in the radiative output
of the Sun, and what mechanisms trigger flares and coronal mass
ejections. Progress in answering these critical questions requires
study of the interaction of the magnetic field and convection with a
resolution sufficient to observe scales fundamental to these processes.
Title: Properties of Magnetic and Velocity Fields in and around
Solar Pores
Authors: Sankarasubramanian, K.; Rimmele, Thomas
Bibcode: 2003ApJ...598..689S
Altcode:
We studied the magnetic and velocity fields of four pores situated
close to the disk center and its surrounding regions. We find the
following results from our analysis: The velocity inside the pore
is very close to zero, whereas there is a strong and narrow downflow
around the pore. The vertical velocity gradient observed at the edge of
the pore is stronger than the velocity gradient seen in intergranular
lanes. Immediately surrounding these narrow downflows, normal granular
convection is observed. This observation is consistent with the
theoretical picture of an isolated flux tube embedded in a quiet region
surrounded by a downflow driven by radiative energy losses. Needle-like
structures were seen around the pore, with the head of the needle
showing an upflow. The needle tail ends in the downflow surrounding
the pore. Assuming the flow is horizontal in the body of the needle,
the needle-like structures would represent a possible signature of
circular flow system surrounding the pore. The radial extent of this
observed flow system (which likely feeds the downflow around the pore)
is about 10". A pore with relatively large fill fraction shows a small
upflow in the center surrounded by the downflow, whereas a pore with
small fill fraction shows downflows throughout the pore. The asymmetries
of the observed Stokes V profiles and their temporal variations are
studied. We find temporal variations of V-profile asymmetries observed
within pores on timescales of 5 minutes.
Title: Annular Downflow Around a Solar Pore
Authors: Tritschler, K.; Schmidt, W.; Rimmele, T.
Bibcode: 2003ANS...324Q..54T
Altcode: 2003ANS...324b..54T; 2003ANS...324..P07T
No abstract at ADS
Title: Advanced Technology Solar Telescope - Approach to a Four-meter
Diffraction Limited Solar Telescope
Authors: Keil, S.; Rimmele, T.; Oschmann, J.; Warner, M.; Dalrymple,
N.; Hubbard, R.; Price, R.; Goodrich, B.; Keller, C.; ATST Team
Bibcode: 2003SPD....34.2019K
Altcode: 2003BAAS...35..847K
The Advanced Technology Solar Telescope (ATST) is intended to be
the next major step in ground based solar observatories. The ATST
will provide a laboratory for ultra high resolution, polarimetric
measurements of all layers of the solar atmosphere. Currently the
project is preparing a conceptual design to fulfill this mission,
including plans for the design, development, construction and operation
of this facility. Given the nearly three-fold increase in aperture
size over the largest existing solar facilities, our approach combines
techniques from the newest solar facilities with lessons from recent
nighttime telescope designs. This approach insures the ATST will meet
the scientific goals that include diffraction-limited performance in
the optical for high spatial resolution solar observations and very
low scattered light to advance coronal observation capabilities. The
current telescope design incorporates the latest active optics
techniques, fast focal ratios for the primary optics, an open design
for ventilation of locally produced seeing, an un-obscured off-axis
pupil and a very high order adaptive optics system built into the
telescope from the beginning. Examples of some of the current design
concepts for the telescope structure, optics, thermal management,
scattered light control, upgrade paths to multi-conjugate adaptive
optics, software and facilities to support future potential upgrades
and instrumentation are given along with some of the key challenges
that lie ahead. The National Solar Observatory is sponsored and
supported by the National Science Foundation.
Title: Diffraction limited observations of flux concentrations and
sunspot finestructure using adaptive optics
Authors: Rimmele, T. R.
Bibcode: 2003SPD....34.1104R
Altcode: 2003BAAS...35..827R
We present diffraction limited observations of magnetic flux
concentrations and penumbral and umbral fine structure within an
active region observed at disk center. We recorded g-band images,
magnetograms, dopplergrams and narrow-band filtergrams using the
Universal Birefringened Filter (UBF) at the Dunn Solar Telescope
(DST). The adaptive optics system at the DST was used to achieve
diffraction limited long exposure imaging with high signal-to-noise. The
main results can be summarized as follows: Strong and spatially
narrow downflows are observed at the edge of magnetic structures
such as flux tubes, pores and the sunspot umbra. Flux concentrations
observed as bright points in intensity expand by about 30-40% from
a height close to where the continuum is formed and the height of
formation for the g-band. For the particular sunspot observed and at
a low altitude in the photosphere we find strong evidence for what
appears to be vigorous, small-scale convection patterns in parts of
the umbra and a light bridge. We observe extremely narrow (<0.2")
channels or sheets of downflowing plasma. We are able to identify
individual penumbral fibrils in our data and find a small bright (hot)
upflow and a more vertical field structure at the filament "head" near
the umbral boundary. The field and flow turn to a nearly horizontal,
dark structure within only about 0.2 arcsec. We compare our results
with theoretical model predictions.
Title: A Single-Mode Fiber Interferometer for the Adaptive Optics
Wave-Front Test
Authors: Ren, D.; Rimmele, T. R.; Hegwer, S.; Murray, L.
Bibcode: 2003PASP..115..355R
Altcode:
A new and innovative single-mode fiber interferometer is proposed for
the wave-front test of the adaptive optics (AO) system. It is based
on a modified Mach-Zehnder interferometer with the two arms replaced
by optical fibers. It avoids the difficulty of fringe interpretation
of the conventional Mach-Zehnder interferometer. As fibers are used,
the whole instrument is compact, flexible, and suitable for the AO
on-site test. Furthermore, as minimum optical components are used,
the interferometer is free of calibration and has high measurement
accuracy. The operation of the interferometer is also very simple,
and wave front can be tested quickly. We discuss the working principle,
experiment setup, fringe analysis, and its application for an existing
AO system. The interferometer can also be used to test wave aberrations
of a single lens or an optical system.
Title: Optical design of high-order adaptive optics for the NSO Dunn
Solar Telescope and the Big Bear Solar Observatory
Authors: Ren, Deqing; Hegwer, Steven L.; Rimmele, Thomas; Didkovsky,
Leonid V.; Goode, Philip R.
Bibcode: 2003SPIE.4853..593R
Altcode:
The National Solar Observatory (NSO) and the New Jersey Institute of
Technology are jointly developing high order solar Adaptive Optics (AO)
to be deployed at both the Dunn Solar Telescope (DST) and the Big Bear
Solar Telescope (BBST). These AO systems are expected to deliver first
light at the end of 2003. We discuss the AO optical designs for both
the DST and the BBST. The requirements for the optical design of the
AO system are as follows: the optics must deliver diffraction-limited
imaging at visible and near infrared over a 190"×190" field of
view. The focal plane image must be flat over the entire field of view
to accommodate a long slit and fast spectrograph. The wave-front sensor
must be able to lock on solar structure such as granulation. Finally,
the cost for the optical system must fit the limited budget. Additional
design considerations are the desired high bandwidth for tip/tilt
correction, which leads to a small, fast and off-the-shelf tilt-tip
mirror system and high throughput, i.e., a minimal number of optical
surfaces. In order to eliminate pupil image wander on the wave-front
sensor, both the deformable mirror and tip-tilt mirror are located on
the conjugation images of the telescope pupil. We discuss the details
of the optical design for the high order AO system, which will deliver
high resolution image at the 0.39 - 1.6 μm wavelength range.
Title: Design and development of the Advanced Technology Solar
Telescope (ATST)
Authors: Keil, Stephen L.; Rimmele, Thomas; Keller, Christoph U.;
Hill, Frank; Radick, Richard R.; Oschmann, Jacobus M.; Warner, Mark;
Dalrymple, Nathan E.; Briggs, John; Hegwer, Steven L.; Ren, Dauxing
Bibcode: 2003SPIE.4853..240K
Altcode:
High-resolution studies of the Sun's magnetic fields are needed for
a better understanding of solar magnetic fields and the fundamental
processes responsible for solar variability. The generation of magnetic
fields through dynamo processes, the amplification of fields through
the interaction with plasma flows, and the destruction of fields
are still poorly understood. There is still incomplete insight as
to what physical mechanisms are responsible for heating the corona,
what causes variations in the radiative output of the Sun, and what
mechanisms trigger flares and coronal mass ejections. Progress in
answering these critical questions requires study of the interaction
of the magnetic field and convection with a resolution sufficient to
observe scales fundamental to these processes. The 4m aperture Advanced
Technology Solar Telescope (ATST) will be a unique scientific tool,
with excellent angular resolution, a large wavelength range, and low
scattered light. With its integrated adaptive optics, the ATST will
achieve a spatial resolution nearly 10 times better than any existing
solar telescope. Building a large aperture telescope for viewing the
sun presents many challenges, some of the more difficult being: · Heat
control and rejection · Contamination and scattered light control ·
Control of telescope and instrument polarization · Site selection
This talk will present a short summary of the scientific questions
driving the ATST design, the design challenges faced by the ATST, and
the current status of the developing design and siting considerations
Title: Diffraction limited spectro-polarimeter - Phase I
Authors: Sankarasubramanian, Kasiviswanathan; Elmore, David F.; Lites,
Bruce W.; Sigwarth, Michael; Rimmele, Thomas R.; Hegwer, Steven L.;
Gregory, Scott; Streander, Kim V.; Wilkins, Lawrence M.; Richards,
K.; Berst, C.
Bibcode: 2003SPIE.4843..414S
Altcode:
A diffraction limited spectro-polarimeter is under construction at the
National Solar Observatory in collaboration with the High Altitude
Observatory. The scientific objective of the project is to measure
the magnetic fields on the Sun up to the diffraction limit of the Dunn
Solar Telescope. The same instrument would also measure the magnetic
field of large sunspots or sunspot groups with reasonable spatial
resolution. This requires a flexible image scale which cannot be
obtained with the current Advanced Stokes Polarimeter (ASP) without
loosing 50% of the light. The new spectro-polarimeter is designed
in such a way that the image scale can be changed without loosing
much light. It can work either in high-spatial resolution mode (0.09
arcsec per pixel) with a small field of view (FOV: 65 arcsec) or in
large FOV mode (163 arcsec) with low-spatial resolution (0.25 arcsec
per pixel). The phase-I of this project is to design and build the
spectrograph with flexible image scale. Using the existing modulation,
calibration optics of the ASP and the ASP control and data acquisition
system with ASP-CHILL camera, the spectrograph was tested for its
performance. This paper will concentrate on the performance of the
spectrograph and will discuss some preliminary results obtained with
the test runs.
Title: Solar adaptive optics: a progress report
Authors: Rimmele, Thomas R.; Richards, Kit; Hegwer, Steven L.; Ren,
Deqing; Fletcher, S.; Gregory, Scott; Didkovsky, Leonid V.; Denker,
Carsten J.; Marquette, William; Marino, J.; Goode, Philip R.
Bibcode: 2003SPIE.4839..635R
Altcode:
We present a progress report of the solar adaptive optics (AO)
development program at the National Solar Observatory (NSO) and the
Big Bear Solar Observatory (BBSO). Examples of diffraction-limited
observations obtained with the NSO low-order solar adaptive optics
system at the Dunn Solar Telescope (DST) are presented. The design
of the high order adaptive optics systems that will be deployed at
the DST and the BBSO is discussed. The high order systems will provide
diffraction-limited observations of the Sun in median seeing conditions
at both sites.
Title: Technical challenges of the Advanced Technology Solar Telescope
Authors: Rimmele, Thomas R.; Keil, Stephen L.; Keller, Christoph
U.; Hill, Frank; Briggs, John; Dalrymple, Nathan E.; Goodrich, Bret
D.; Hegwer, Steven L.; Hubbard, Rob; Oschmann, Jacobus M.; Radick,
Richard R.; Ren, Deqing; Wagner, Jeremy; Wampler, Stephen; Warner, Mark
Bibcode: 2003SPIE.4837...94R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) will be the most
powerful solar telescope in the world, providing a unique scientific
tool to study the Sun and possibly other astronomical objects, such
as solar system planets. We briefly summarize the science drivers and
observational requirements of ATST. The main focus of this paper is on
the many technical challenges involved in designing a large aperture
solar telescope. The ATST project has entered the design and development
phase. Development of a 4-m solar telescope presents many technical
challenges. Most existing high-resolution solar telescopes are designed
as vacuum telescopes to avoid internal seeing caused by the solar heat
load. The large aperture drives the ATST to an open-air design, similar
to night-time telescope designs, and makes thermal control of optics
and telescope structure a paramount consideration. A heat stop must
reject most of the energy (13 kW) at prime focus without introducing
internal seeing. To achieve diffraction-limited observations at visible
and infrared wavelengths, ATST will have a high order (order 1000
DoF) adaptive optics system using solar granulation as the wavefront
sensing target. Coronal observations require occulting in prime focus,
a Lyot stop and contamination control of the primary. An initial set of
instruments will be designed as integral part of the telescope. First
telescope design and instrument concepts will be presented.
Title: High-order adaptive optical system for Big Bear Solar
Observatory
Authors: Didkovsky, Leonid V.; Dolgushyn, Alexander; Marquette,
William; Nenow, Jeff; Varsik, John; Goode, Philip R.; Hegwer, Steven
L.; Ren, Deqing; Fletcher, Steve; Richards, Kit; Rimmele, Thomas;
Denker, Carsten J.; Wang, Haimin
Bibcode: 2003SPIE.4853..630D
Altcode:
We present a high-order adaptive optical system for the 26-inch vacuum
solar telescope of Big Bear Solar Observatory. A small elliptical
tip/tilt mirror is installed at the end of the existing coude
optical path on the fast two-axis tip/tilt platform with its resonant
frequency around 3.3 kHz. A 77 mm diameter deformable mirror with 76
subapertures as well as wave-front sensors (correlation tracker and
Shack-Hartman) and scientific channels for visible and IR polarimetry
are installed on an optical table. The correlation tracker sensor
can detect differences at 2 kHz between a 32×32 reference frame
and real time frames. The WFS channel detects 2.5 kHz (in binned
mode) high-order wave-front atmosphere aberrations to improve solar
images for two imaging magnetographs based on Fabry-Perot etalons in
telecentric configurations. The imaging magnetograph channels may work
simultaneously in a visible and IR spectral windows with FOVs of about
180×180 arc sec, spatial resolution of about 0.2 arc sec/pixel and
SNR of about 400 and 600 accordingly for 0.25 sec integration time.
Title: Design and development of the Advanced Technology Solar
Telescope
Authors: Keil, S.; Rimmele, T.; Keller, C.; ATST Team
Bibcode: 2003AN....324..303K
Altcode:
Led by the National Solar Observatory, plans have been made to design
and to develop the Advanced Technology Solar Telescope (ATST). The ATST
will be a 4-m general-purpose solar telescope equipped with adaptive
optics and versatile post-focus instrumentation. Its main aim will be
to achieve an angular resolution of 0.03 arcsec (20 km on the solar
surface). The project and the telescope design are briefly described.
Title: Velocity Measurements of Umbral Dots
Authors: Hartkorn, K.; Rimmele, T.
Bibcode: 2003ASPC..286..281H
Altcode: 2003ctmf.conf..281H
No abstract at ADS
Title: Statistical Properties of Asymmetries in and around Sunspots
Authors: Sankarasubramanian, K.; Rimmele, T.
Bibcode: 2003ASPC..286..243S
Altcode: 2003ctmf.conf..243S
No abstract at ADS
Title: Residual Intensity and Velocity Measurements of Bright Points
Authors: Hartkorn, K.; Rimmele, T.
Bibcode: 2003ASPC..286..193H
Altcode: 2003ctmf.conf..193H
No abstract at ADS
Title: Seeing Characteristic at a Lake-Site Observatory
Authors: Denker, C.; Didkovsky, L.; Marquette, W. H.; Goode, P. R.;
Venkateswaran, K.; Rimmele, T. R.
Bibcode: 2003ASPC..286...23D
Altcode: 2003ctmf.conf...23D
No abstract at ADS
Title: First Results from the HAO/NSO Diffraction-Limited
Spectro-Polarimeter
Authors: Lites, B. W.; Elmore, D. F.; Streander, K. V.;
Sankarasubramanian, K.; Rimmele, T. R.; Sigwarth, M.
Bibcode: 2003ASPC..307..324L
Altcode:
No abstract at ADS
Title: Science Objectives and Technical Challenges of the Advanced
Technology Solar Telescope (Invited review)
Authors: Rimmele, T.; Keil, S. L.; Keller, C.; Hill, F.; Penn, M.;
Goodrich, B.; Hegwer, S.; Hubbard, R.; Oschmann, J.; Warner, M.;
Dalrymple, N.; Radick, R.; Atst Team
Bibcode: 2003ASPC..286....3R
Altcode: 2003ctmf.conf....3R
No abstract at ADS
Title: Long Exposure Point Spread Function Estimation using Wavefront
Sensor Data
Authors: Marino, J.; Rimmele, T.; Tatulli, E.
Bibcode: 2003ASPC..286...69M
Altcode: 2003ctmf.conf...69M
No abstract at ADS
Title: High-order adaptive optical system for Big Bear Solar
Observatory
Authors: Didkovsky, L. V.; Denker, C.; Goode, P. R.; Wang, H.; Rimmele,
T. R.
Bibcode: 2003AN....324..297D
Altcode:
A high-order Adaptive Optical (AO) system for the 65 cm vacuum telescope
of the Big Bear Solar Observatory (BBSO) is presented. The Coudé-exit
of the telescope has been modified to accommodate the AO system and two
imaging magnetograph systems for visible-light and near infrared (NIR)
observations. A small elliptical tip/tilt mirror directs the light into
an optical laboratory on the observatory's 2mathrm {nd}
floor just below the observing floor. A deformable mirror (DM) with
77 mm diameter is located on an optical table where it serves two
wave-front sensors (WFS), a correlation tracker (CT) and Shack-Hartman
(SH) sensor for the high-order AO system, and the scientific channels
with the imaging magnetographs. The two-axis tip/tilt platform has a
resonance frequency around 3.3 kHz and tilt range of about 2 mrad,
which corresponds to about 25'' in the sky. Based on
32 x 32 pixel images, the CT detects image displacements between a
reference frame and real-time frames at a rate of 2 kHz. High-order
wave-front aberrations are detected in the SH WFS channel from slope
measurements derived from 76 sub-apertures, which are recorded with
1,280 x 1,024 pixel Complex Metal Oxide Semiconductor (CMOS) camera
manufactured by Photobit camera. In the 4 x 4 pixel binning mode,
the data acquisition rate of the CMOS device is more than 2 kHz. Both
visible-light and NIR imaging magnetographs use Fabry-Pérot etalons in
telecentric configurations for two-dimensional spectro-polarimetry. The
optical design of the AO system allows using small aperture prefilters,
such as interference or Lyot filters, and 70 mm diameter Fabry-Pérot
etalons covering a field-of-view (FOV) of about 180''
x 180''.
Title: Velocity and Magnetic Fields in and around Pores
Authors: Sankarasubramanian, K.; Rimmele, T.
Bibcode: 2003ASPC..286..291S
Altcode: 2003ctmf.conf..291S
No abstract at ADS
Title: Downflows around a solar pore
Authors: Tritschler, A.; Schmidt, W.; Rimmele, T.
Bibcode: 2002ESASP.506..477T
Altcode: 2002svco.conf..477T; 2002ESPM...10..477T
We used the Fabry-Perot interferometer TESOS to observe a solar
pore near disk center in two photospheric spectral lines (Fe I 557.6
nm and Fe I 569.1 nm) which correspond to different heights in the
atmosphere. The measurements were made during the joint campaign with
the NSO/Sacramento-Peak adaptive optics system installed at the German
Vacuum Tower Telescope (VTT). The Doppler-velocity measurements show an
annular downflow around the outer edge of the pore. This downflow is
persistent during the whole observation period, which is demonstrated
in the time-averaged Dopplergrams and the corresponding azimuthally
integrated and time-averaged radial velocity profiles.
Title: Spectroscopic observations of G-band bright points
Authors: Langhans, K.; Schmidt, W.; Rimmele, T.
Bibcode: 2002ESASP.506..397L
Altcode: 2002ESPM...10..397L; 2002svco.conf..397L
Imaging in the G-band is commonly used to investigate the morphological
properties of small magnetic field concentrations in the solar
photosphere. However the physical background, explaining the brightness
of these structures, has remained unclear. Our observations add the
spectroscopic point of view to this discussion. The observations at
high spatial resolution are obtained with the horizontal spectrograph
at the Dunn Solar Telescope of the National Solar Observatory, USA. We
scanned across a pore within an active region and took spectra in three
different wavelength regions (430 nm, 526 nm, 569 nm) simultaneously
to G-band and broadband continuum images. We present the results and
discuss the spectroscopic bright point properties in comparison to
former observations and synthetic data.
Title: On the V-profile asymmetries in sunspots
Authors: Sankarasubramanian, K.; Rimmele, Thomas
Bibcode: 2002ESASP.505..571S
Altcode: 2002IAUCo.188..571S; 2002solm.conf..571S
We studied the statistical properties of V-profile asymmetries in and
around several sunspots situated at different position on the solar
disk. The asymmetries formed at different regions of the sunspot
(like the umbra, penumbra etc.) are clearly separated. Each of
the sunspot showed similar relation between the area and amplitude
asymmetries. A bi-modal distribution was seen in the plot between the
area and amplitude asymmetries. The sunspot umbra showed very little
area and amplitude asymmetries. The penumbral region showed larger
area asymmetries compared to the amplitude asymmetries whereas the
light-bridge and small-scale fields showed larger amplitude asymmetries
compared to the area asymmetries. These asymmetries were compared with
the velocity gradients and showed good correlation between the two,
suggesting that the asymmetries were produced due to the gradients in
the velocity. The results are compared with the results obtained with
the SIR-inversion code and found good agreement.
Title: Bisector Analysis of Stokes Profiles: Effects Due to Gradients
in the Physical Parameters
Authors: Sankarasubramanian, K.; Rimmele, Thomas
Bibcode: 2002ApJ...576.1048S
Altcode:
The asymmetry of Stokes V profiles of the spectral lines λ6301.5 and
λ6302.5 was utilized to systematically study a sunspot observed close
to the disk center. The Stokes spectra were taken with the National
Solar Observatory (NSO)/High Altitude Observatory Advanced Stokes
Polarimeter (ASP). The NSO low-order adaptive optics system was
used to record a data set of consistently high resolution. We find
the following results from this analysis: (1) a strong correlation
between the center-of-gravity (COG) velocity derived from the intensity
profiles with the V-profile asymmetry; (2) the amplitude asymmetry
is much more sensitive to changes in the COG velocity than the area
asymmetry; and (3) plotting area versus amplitude asymmetry for the
entire active region results in a bimodal distribution. Different
areas within the active region, such as penumbra, umbra, light bridge,
and small-scale fields outside the sunspot, are clearly separated
in this plot. The light bridges and the small-scale magnetic fields
surrounding the observed sunspot show larger amplitude asymmetry
compared to the area asymmetry, whereas the penumbra shows larger
area asymmetry. In comparison, the Stokes V spectra measured in
the umbra show little area and amplitude asymmetry. In this paper,
we use bisector analysis of the V intensity profile as a new tool to
determine the gradients in the physical parameters in a more direct
way. The gradients derived from the bisector method provide further
and more direct evidence for the physical picture derived from the
study of the asymmetries. For light bridges we find that the data is
consistent with a picture of small convective cells confined to lower
layers of the atmosphere. Asymmetries in the penumbra are caused by
steep vertical gradients in the Evershed velocities in combination with
the gradient in the line-of-sight inclination angle, confirming the
earlier observations. For small-scale fields, the picture is consistent
with the canopy effect. We also compare the average velocity and the
magnetic field strength derived from this bisector analysis with the
velocity and magnetic field strength derived from the ASP inversion and
find excellent agreement between these independent methods. Apart from
these asymmetries, we also observe extremely asymmetric V profiles, such
as one-lobed profiles and multiple reversals, mostly at the edges of the
limb-side penumbra. In these regions, we also find differences in the V
profiles of λ6301.5 and λ6302.5 that suggest steep gradients in the
physical parameters. The asymmetries derived from a single scan match
well with the ones derived from the time-averaged properties obtained by
averaging 14 such scans separated by 7.5 minutes. This suggests that,
in a statistical sense, the Stokes V asymmetries do not vary with time
and describe a global/general property of magnetic features found in
regions such as light bridge, umbra, penumbra, and small-scale fields.
Title: Small-scale topology of solar atmospheric dynamics. V. Acoustic
events and internetwork grains
Authors: Hoekzema, N. M.; Rimmele, T. R.; Rutten, R. J.
Bibcode: 2002A&A...390..681H
Altcode:
We use high-quality observations from the Dunn Solar Telescope
at NSO/Sacramento Peak to study spatio-temporal co-location of
acoustic flux events in the photosphere and internetwork grains
in the chromosphere. The events are diagnosed as sites with excess
upward-propagating five-minute waves measured from Dopplergrams. The
grains are repetitive bright internetwork features in simultaneous
\CaII \KtwoV filtergrams. We find that the largest-flux sites in
the granulation have appreciably larger than random probability to
co-locate with exceptionally bright chromospheric internetwork grains,
at an average delay of about two minutes which is likely to represent
sound travel time to the chromosphere. This finding strengthens the
case for acoustic grain excitation.
Title: The Advanced Technology Solar Telescope
Authors: Keller, C. U.; Rimmele, T. R.; Hill, F.; Keil, S. L.;
Oschmann, J. M.; ATST Team
Bibcode: 2002AN....323..294K
Altcode:
The Advanced Technology Solar Telescope is the largest solar optical
facility currently under development. The National Solar Observatory
and its partners have just started the design and development phase
with first light being planned for late this decade. The 4-m telescope
will provide an angular resolution down to 0.025 arcsec, a large photon
flux for precise magnetic and velocity field measurements, and access
to a broad set of diagnostics from 0.3 to 28 mu m. We summarize the
currently envisioned scientific capabilities of the telescope and its
suite of instruments along with a glimpse at some of the early concepts.
Title: The Advanced Technology Solar Telescope
Authors: Rimmele, T. R.; Keil, S. L.; Keller, C. U.; Hill, F.;
Oschmann, J. M.; Warner, M.; Dalrymple, N. E.; ATST Team
Bibcode: 2002AAS...200.3408R
Altcode: 2002BAAS...34..691R
The 4m aperture Advance Technology Solar Telescope (ATST) will be the
most powerful solar telescope in the world and a unique scientific tool
to study the Sun and other astronomical objects, such as planets. The
ATST will replace major existing national solar facilities at the end
of this decade. The ATST project has entered the design and development
phase. We present an overview of the ATST science drivers and discuss
preliminary design concepts and technical challenges. The ATST science
goals lead to the following general requirements for the ATST facility:
- Diffraction limited angular resolution in the visible and infrared
to study fundamental astrophysical processes with unprecedented
resolution enabling verification of model predictions. - A high photon
flux for accurate measurements of physical parameters throughout
the solar atmosphere, such as magnetic strength and direction,
temperature and velocity. - Access to a new diagnostics at relatively
unexplored infrared wavelength. - Low scattered light to enable
coronal observations. - Low instrumental polarization for accurate
measurements of magnetic fields. Development of a 4m solar telescope
presents many technical challenges. The large aperture drives the ATST
to an open-air design and makes thermal control of optics and telescope
structure a paramount consideration. To achieve diffraction-limited
observations at visible and infrared wavelength ATST will have a high
order solar adaptive optics system. Coronal observations require,
occulting in prime focus, a Lyot stop and contamination control of the
primary. An initial set of instruments will be designed as integral
part of the telescope. Preliminary telescope and instrument concepts
will be discussed.
Title: Solar Seeing Seven Ways From Sunday
Authors: Hill, F.; Balasubramaniam, K. S.; Beckers, J. M.; Briggs,
J. W.; Hegwer, S.; Radick, R. R.; Rimmele, T. R.; Richards, K.;
Denker, C.
Bibcode: 2001AGUSM..SP21B03H
Altcode:
The Advanced Technology Solar Telescope (ATST) site survey will be
carried out with a Solar Differential Image Motion Monitor (S-DIMM)
and a six-scintillometer SHAdow BAnd Ranging (SHABAR) array. This
device will provide estimates of the Fried parameter, R0,
derived from the differential motion measurements of two images of the
same cut across the solar limb formed by two 45 mm diameter telescope
apertures 225 mm apart, and an estimate of the height dependence of the
index of refraction structure parameter, Cn2, from
the co-variance of the signals from an array of 6 scintillometers with
15 baseline separations. It will also provide a cloud cover measurement
and RMS scintillation signal. In preparation for the survey, we compare
estimates of daytime solar seeing obtained simultaneously from seven
different instruments. The observations were made at NSO/Sacramento
Peak during the period January 26 - February 5, 2001 under a variety of
seeing and transparency conditions ranging from poor to excellent. The
seven instruments were: 1. a S-DIMM/SHABAR mounted at the top of
the Dunn Solar Tower (DST) 2. an identical S-DIMM/SHABAR mounted at
ground level 3. the NSO/SP Adaptive Optics wavefront sensor providing
subaperature image motion measurements 4. a Dalsa camera providing
bursts of high-speed images for spectral ratio seeing estimates 5. a
Xedar camera obtaining granulation images for contrast and differential
stretching measurements 6. a Seykora scintillometer mounted in the
DST 7. a video camera recording a movie of the visual quality of the
image The analysis of this data set will provide the first direct
comparison of this many simultaneous solar seeing measurements, test
the ATST site survey system, and verify the SHABAR measurement of the
seeing height profile.
Title: The Advanced Technology Solar Telescope -- Science Goals and
Instrument Description.
Authors: Rimmele, T. R.; Keil, S. L.; Keller, C. U.; Hill, F.
Bibcode: 2001AGUSM..SH31D08R
Altcode:
High-resolution studies of the Sun's magnetic fields are needed for
a better understanding of solar magnetic fields and the fundamental
processes responsible for solar variability. The generation of magnetic
fields through dynamo processes, the amplification of fields through
the interaction with plasma flows, and the destruction of fields are
still poorly understood. There is still incomplete insight as to what
physical mechanisms are responsible for heating the corona, what causes
variations in the radiative output of the Sun, and what mechanisms
trigger flares and coronal mass ejections. Progress in answering
these critical questions requires study of the interaction of the
magnetic field and convection with a resolution sufficient to observe
physical scales fundamental to these processes. The 4m aperture ATST
will be a unique scientific tool, with excellent angular resolution,
a large wavelength range, and low scattered light. With its integrated
adaptive optics, the ATST will achieve a spatial resolution nearly 10
times better than any existing solar telescope. The ATST will provide:
Unprecedented angular resolution of 0.03 arcsec in the visible and
0.08 arcsec at 1.6 microns to enable us to clearly resolve and study the
fundamental astrophysical processes on their intrinsic scales and to
verify model predictions. A high photon flux for accurate and precise
measurements of physical parameters, such as magnetic field strength
and direction, temperature and velocity, on the short time scales
involved. Access to a broad set of diagnostics, from visible to thermal
infrared wavelengths. Low scattered light observations and coronagraphic
capabilities in the infrared, allowing measurements of coronal magnetic
fields. The ATST has been highly ranked by the latest Decadal Survey
of Astronomy and Astrophysics and the NAS/NRC study of ground-based
solar astronomy. A large part of the solar community will participate
in the design and development of the ATST. A strawman telescope design,
design challenges and instrument concepts will be discussed. Examples
of recent high resolution observations with adaptive optics, that
demonstrate the potential of this new technology will be shown.
Title: Spectroscopic Observation of G-Band Bright Points
Authors: Langhans, K.; Schmidt, W.; Rimmele, T.; Sigwarth, M.
Bibcode: 2001ASPC..236..439L
Altcode: 2001aspt.conf..439L
No abstract at ADS
Title: The Advanced Technology Solar Telescope
Authors: Keil, S. L.; Rimmele, T. R.; Keller, C. U.; Atst Team
Bibcode: 2001ASPC..236..597K
Altcode: 2001aspt.conf..597K
No abstract at ADS
Title: A new Stokes Polarimeter for the Dunn Solar Telescope
Authors: Sigwarth, M.; Berst, C.; Gregory, S.; Hegwer, S.; Richards,
K.; Rimmele, T.; Wilkins, L.; Lites, B. W.; Elmore, D. F.; Streander,
K. V.
Bibcode: 2001ASPC..236...57S
Altcode: 2001aspt.conf...57S
No abstract at ADS
Title: The Advanced Technology Solar Telescope: Science Goals and
Instrument Description
Authors: Rimmele, T.; Keller, C.; Keil, S.; Hill, F.; Atst Team
Bibcode: 2001AGM....18S1006R
Altcode:
High-resolution studies of the Sun's magnetic fields are needed for
a better understanding of solar magnetic fields and the fundamental
processes responsible for solar variability. For example, the
generation of magnetic fields through dynamo processes is still poorly
understood. There is still incomplete insight as to what physical
mechanisms are responsible for heating the corona, what causes
variations in the radiative output of the Sun. Progress in answering
these critical questions requires study of the interaction of the
magnetic field and convection with a resolution sufficient to observe
scales fundamental to these processes. The 4m aperture ATST will be
a unique scientific tool, which will provide unprecedented angular
resolution, high photon flux, access to a broad set of diagnostics,
from visible to thermal infrared wavelengths, and low scattered light
observations and coronagraphic capabilities in the infrared. Development
of a 4-m solar telescope presents several technical challenges. The
large heat flux makes thermal control of optics and telescope structure
a paramount consideration. To achieve diffraction-limited performance,
a powerful solar adaptive optics system is required. Low scattered
light is essential for observing the corona but also to accurately
measure the physical properties of small structures in, for example,
sunspots. Contamination control of the primary and secondary mirrors
must therefore be addressed. An initial set of instruments will be
designed as integral part of the telescope during the upcoming design
and development phase. A strawman telescope design and instrument
concepts will be discussed.
Title: The Advanced Solar Telescope
Authors: Keil, S. L.; Rimmele, T. R.; Keller, C.; Hill, F.
Bibcode: 2000AAS...197.1710K
Altcode: 2000BAAS...32.1433K
The planned Advanced Technology Solar Telescope (ATST) will be a 4-m
aperture general-purpose solar telescope with integrated adaptive
optics and versatile post focus instrumentation. The ATST will achieve
an angular resolution of 0.03 arcsec (20 km on the solar surface)
in the visible, which is almost an order of magnitude better than
what is achieved with current solar telescopes. This will make it
possible to resolve the fundamental astrophysical hydrodynamic and
magnetohydrodynamic processes and structures in the solar atmosphere
such as the building blocks of solar magnetic fields that are believed
to be responsible for solar irradiance variations and the heating of the
outer solar atmosphere. The ATST will cover the wavelength range from
0.35 to 35 ?m and minimize scattered light. The initial set of post
focus instruments will exploit the unique capabilities of the ATST to
study magnetic fields at the highest spatial resolution in the visible
and near-infrared parts of the spectrum. The ATST was highly recommended
by the recent Decadal Study. A proposal for a four-year Design and
Development phase has just been submitted to the NSF. Construction is
expected to start in FY2005. The National Solar Observatory is operated
by the Associated Universities for Research in Astronomy and is funded
by the National Science Foundation under a cooperative agreement.
Title: Solar adaptive optics
Authors: Rimmele, Thomas R.
Bibcode: 2000SPIE.4007..218R
Altcode:
High resolution observations of the Sun are of key importance
in understanding fundamental astrophysical processes. Adaptive
optics (AO) is an important tool that allows solar astronomers to
achieve diffraction limited observations from existing ground based
telescopes. AO is also a key technology required for a future 4m-class
Advanced Solar Telescope (AST) that the international community of solar
astronomers is planning to build. The history of the development of
solar AO is reviewed and results from recent successful demonstrations
of solar AO systems are presented. The main difference between solar
AO and night time AO is the different, and more elaborate wavefront
sensing technique that has to be applied in order to measure wavefront
aberrations using solar granulation as a target. Different approaches
to this problem are discussed. Multi-conjugate AO has been proposed as a
technique to achieve diffraction limited resolution over a field-of-view
(FOV) significantly larger than the isoplanatic patch. The Sun is an
ideal object for the development and application of MCAO.
Title: The Dynamics of the Excitation of Solar Oscillations
Authors: Strous, Louis H.; Goode, Philip R.; Rimmele, Thomas R.
Bibcode: 2000ApJ...535.1000S
Altcode:
We investigate seismic events, bursts of seismic waves that are
generated locally just below the solar surface and that we detect
traveling up through the photosphere. We identify a few thousand
seismic events by their traveling wave character and find that they
are associated with continuum darkening and downflow and have an
extent of on average about 10-15 minutes and 1 Mm. Their birth rate
is about 8×10-16 m-2 s -1. The
observed upwardly traveling seismic flux in the average event
(as derived from velocities in the p-mode region of k-ω space) is
followed after about 3 minutes by some reflected downward flux. Only
a small fraction of the energy generated in the hypocenter of the
event below the surface travels straight up for us to see. The bulk
of the generated energy is directed or reflected downward, and is
eventually transformed into p-modes. The seismic events at the surface
contain about 1.5×1019 J of seismic energy each, which
corresponds to an average flux level of about 8.5 kW m-2
over the whole surface. The total energy flow is likely more than an
order of magnitude greater, and is then in the same ballpark as the
estimate of Libbrecht for the power required to sustain the p-mode
spectrum. We find a roughly linear relation between the peak seismic
flux and the peak downward convective velocity associated with each
seismic event, which does not fit the highly nonlinear relations found
theoretically by Lighthill and Goldreich & Kumar for stochastic
excitation by turbulent convection, but does fit the monopole source
deduced by Nigam & Kosovichev from a study of the p-mode spectrum.
Title: High resolution spectroscopy of active regions with adaptive
optic
Authors: Sigwarth, M.; Rimmele, T. R.
Bibcode: 2000SPD....31.0304S
Altcode: 2000BAAS...32R.834S
With the NSO low-order adaptive optic system at the NSO Dunn Solar
Telescope it is now possible to perform spectroscopic measurements
at high angular resolution and high signal-to-noise level. The
performance of the AO system for spectroscopic investigations will be
demonstrated. By using a dual Fabry-Perot spectrometer we obtained
spectral line scans of active regions with a spatial resolution
of 0.3 arcsec at 557nm. We use these data to adress questions of
magnetoconvection in active regions. This work is supported by NSO/AURA
Title: Evolution of small-scale magnetic fields from combined adaptive
optics and phase-diverse speckle imaging
Authors: Keller, C. U.; Rimmele, T. R.; Paxman, R. G.; Seldin, J. H.;
Carrara, D.; Gleichman, K.
Bibcode: 2000SPD....31.0301K
Altcode: 2000BAAS...32..833K
We have obtained movies of the photospheric magnetic field at a
sustained resolution of 0.2 arcsec by combining the adaptive optics
system at the Dunn Solar Telescope with the Zurich Imaging Polarimeter I
(ZIMPOL) and processing the data with Phase-Diverse Speckle Imaging and
speckle deconvolution. The adaptive optics was correcting the low-order
aberrations with an update rate of about 1.5 kHz and fed a narrow-band
channel through the Universal Birefringent Filter in the wing of the CaI
610.3 nm line and two white-light channels that were used to obtain one
in-focus and one out-of-focus image for the phase-diversity processing,
which removes the remaining aberrations. All three channels were
equipped with ZIMPOL I cameras running simultaneously at 5 frames
per second. The narrow-band intensity and magnetogram images were
reconstructed using speckle deconvolution. This combined attack to
obtain the best magnetogram movies of the solar surface was very
successful and led to spectacular time sequences with a consistent
spatial resolution of better than 0.2 arcsec. We will present the
first scientific results on the evolution of the small-scale magnetic
fields in an active region. This work was supported by the National
Science Foundation.
Title: Deconvolution of narrowband solar images using aberrations
estimated from phase-diverse imagery
Authors: Seldin, John H.; Paxman, Richard G.; Carrara, David A.;
Keller, Christoph U.; Rimmele, Thomas R.
Bibcode: 1999SPIE.3815..155S
Altcode:
Phase-Diverse Speckle (PDS) is a short-exposure data- collection and
processing technique that blends phase- diversity and speckle-imaging
concepts. PDS has been successfully used for solar astronomy to achieve
near diffraction-limited resolution in ground-based imaging of solar
granulation. Variants of PDS that involve narrow-band, spectroscopic,
and polarimetric data provide more information observations. We
present results from processing data collected with the 76-cm Richard
B. Dunn Solar Telescope (DST) on Sacramento Peak, NM. Three-channel
data sets consisting of a pair of phase-diverse images of the solar
continuum and a narrow-band image were collected over spans of 15 - 20
minutes. Point-spread functions that are estimated from the PDS data are
used in a multi-frame deconvolution algorithm to correct the narrow-band
imagery. The data were processed into a number of time series. A rare,
short-lived continuum bright point with a peak intensity at a factor
of 2.1 above the mean intensity in the continuum was observed in one
such sequence. The field of view spans multiple isoplanatic patches,
and strategies for processing these large fields were developed. We will
discuss these methods along with other techniques that were explored
for accelerating the processing. Finally, we show the first PDS
reconstruction of adaptive-optics (AO) compensated solar granulation
taken at the DST. As expected, we find that these data are less
aberrated and, thus, the use of AO in future experiments is planned.
Title: The NSO Solar Adaptive Optics Program: First Results.
Authors: Rimmele, T. R.; Radick, R. R.; Richards, K.; Dunn, R. B.
Bibcode: 1999AAS...19410307R
Altcode: 1999BAAS...31Q1002R
The National Solar Observatory is developing solar adaptive optics at
the R.B. Dunn Solar Telescope (DST). The project recently achieved
a key milestone when the atmospheric control loop was closed at the
DST. The system currently compensates about 20 spatial modes with a
loop bandwidth of about 30 Hz. A 97-actuator deformable mirror is used
for wavefront correction. A correlating Shack-Hartmann wavefront sensor
provides real-time estimates of the wavefront errors using arbitrary
scenes, such as solar granulation and small pores, as the wavefront
sensing target. We will describe the system design and present results
from first engineering runs at the DST.
Title: The Granular Magnetic Fields of the Quiet Sun
Authors: Lin, Haosheng; Rimmele, Thomas
Bibcode: 1999ApJ...514..448L
Altcode:
We report new observations that combine high-precision infrared
polarimetry and high-resolution imagery in the visible to demonstrate
that most of the quiet solar surface contains a measurable
magnetic field. We found that when observed at 1 arcsec2
resolution, 68% of the observed area contains magnetic flux higher
than 5×1015 Mx (corresponding to an apparent average field
of 1 G). The majority of these magnetic features have magnetic flux
below 5×1016 Mx. Their magnetic field strengths range
from below 200 to 1000 G, which means that their filling factors
are on the order of 1%. The spatial distribution and time evolution
of these magnetic features are closely associated with the solar
granulation. The properties of these weak granular magnetic features
we observed differ from those of the intranetwork fields described in
earlier observations. We also observed the formation and disappearance
of a kilogauss magnetic feature associated with the development of
intergranular lanes, which may be evidence of convective collapse.
Title: High Resolution Solar Physics: Theory, Observations, and
Techniques
Authors: Rimmele, T. R.; Balasubramaniam, K. S.; Radick, R. R.
Bibcode: 1999ASPC..183.....R
Altcode: 1999hrsp.conf.....R
No abstract at ADS
Title: Solar Adaptive Optics at the National Solar Observatory
Authors: Rimmele, T.; Dunn, R.; Richards, K.; Radick, R.
Bibcode: 1999ASPC..183..222R
Altcode: 1999hrsp.conf..222R
No abstract at ADS
Title: The Excitation of Solar Oscillations -- Observations and
Simulations
Authors: Goode, P.; Strous, L.; Rimmele, T.; Stein, R.; Nordlund, Å.
Bibcode: 1999ASPC..183..456G
Altcode: 1999hrsp.conf..456G
No abstract at ADS
Title: The Excitation of Solar Oscillations
Authors: Strous, Louis H.; Goode, Philip R.; Rimmele, Thomas R.
Bibcode: 1999soho....9E..81S
Altcode:
We investigate seismic events, bursts of seismic waves that are
generated locally just below the solar surface and that we detect
travelling up through the photosphere. We identify 646 seismic events,
which are associated with intergranular lanes and have an extent
of on average about 10 minutes and 3 Mm. Their birth rate is about
10-16 m-2 s-1. The observed upwardly travelling seismic flux in the
average event (as derived from velocities in the p-mode region of
k-omega space) is followed after about 5 minutes by some reflected
downward flux. Only some of the energy generated in the hypocenter of
the event below the surface travels up for us to see. We propose that
this energy is converted into surface (f-mode-like) waves, while the
unseen, initially downward going energy is eventually transformed
into p-modes. The seismic events at the surface contain about 5 *
1019 J of seismic energy each, which corresponds to an average
flux level of about 4 kW/m2 over the whole surface. The initially
downward directed energy flow is likely substantially greater, and
is then in the same ballpark as the estimate of Libbrecht (1988) for
the power required to sustain the p-mode spectrum. We find a roughly
linear relation between the peak seismic flux and the peak downward
convective velocity associated with each seismic event, which is
not equal to the v8 relation found theoretically by Lighthill (1952)
for stochastic excitation by turbulent convection.
Title: Nineteenth NSO/SP International Workshop on High-Resolution
Solar Physics:Theory, Observations, and Techniques
Authors: Rimmele, Thomas; Balasubramaniam, K. S.; Radick, Richard
Bibcode: 1999PASP..111..127R
Altcode:
No abstract at ADS
Title: Image improvement program at the NSO/SP Vacuum Tower Solar
Telescope
Authors: Radick, Richard R.; Rimmele, Thomas R.; Dunn, Richard B.
Bibcode: 1998SPIE.3353..621R
Altcode:
Over the past several years, a number of steps have been taken to
improve the optical performance of the Vacuum Tower Solar Telescope at
Sacramento Peak. We believe that the optical system of the telescope
is now corrected to better than 1/10 wave rms after these improvements.
Title: Deconvolving solar images using a Shack-Hartmann wavefront
sensor
Authors: Rimmele, Thomas R.; Radick, Richard R.
Bibcode: 1998SPIE.3353.1014R
Altcode:
Deconvolution from wavefront sensing (DWFS) is an image reconstruction
technique that can be used as an alternative to phase diversity
or speckle reconstruction techniques for observations of extended
objects. A correlating Shack- Hartmann wavefront sensor was used to
measure the instantaneous wavefront. The wavefront information was then
used to deconvolve simultaneously taken solar images. The main objective
of this experiment was to validate the correlating Shack-Hartmann
wavefront sensor approach for solar adaptive optics. Several series
of short exposure images and simultaneous wavefront sensor data were
collected at the Vacuum Tower Telescope at Sacramento Peak. We produced
a series of reconstructions of solar features, including granulation,
pores and sunspots. We show that consistent result can be achieved
using DWFS. Reconstructed images of the same object but observed at
slightly different times, i.e. different atmospheric realizations,
are nearly identical.
Title: Solar adaptive optics at the National Solar Observatory
Authors: Rimmele, Thomas R.; Radick, Richard R.
Bibcode: 1998SPIE.3353...72R
Altcode:
The National Solar Observatory at Sacramento Peak is developing adaptive
optics (AO) for solar astronomy. We are currently implementing a low
order adaptive optics system that will correct approximately 20 Zernike
modes. The system design permits future expansion future expansion
to about 80 Zernike modes. We are using a correlating Shack-Hartmann
wavefront sensor. Since a point source is generally not available on
the sun, wavefront tilts have to be derived by applying correlation
techniques to images of extended objects, such as granulation, probes
and sunspots.
Title: EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO -
II. Velocities and Line Profiles
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
Bibcode: 1998SoPh..179..279B
Altcode:
We have studied the dynamics in the sunspot transition region between
the chromosphere and the corona and investigated the extension of
the flow field into the corona. Based on EUV spectra of a medium size
sunspot and its surroundings, NOAA 7981, observed with CDS and SUMER
on SOHO, we derive line-of-sight velocities and study the line profiles
for a series of emission lines.
Title: Extreme-Ultraviolet Sunspot Plumes Observed with SOHO
Authors: Maltby, P.; Brynildsen, N.; Brekke, P.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Wikstøl, Ø.; Rimmele, T.
Bibcode: 1998ApJ...496L.117M
Altcode: 1998astro.ph..1144M
Bright EUV sunspot plumes have been observed in five out of nine sunspot
regions with the Coronal Diagnostic Spectrometer on the Solar and
Heliospheric Observatory. In the other four regions, the brightest line
emissions may appear inside the sunspot but are mainly concentrated in
small regions outside the sunspot areas. These results are in contrast
to those obtained during the Solar Maximum Mission but are compatible
with the Skylab mission results. The present observations show that
sunspot plumes are formed in the upper part of the transition region,
occur in both magnetic unipolar and bipolar regions, and may extend
from the umbra into the penumbra.
Title: EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO -
I. Line Emission and Time Dependence
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
Bibcode: 1998SoPh..179...43B
Altcode:
EUV spectra of a medium-size sunspot and its surroundings, NOAA 7981,
were obtained on 2 August 1996 with the Coronal Diagnostic Spectrometer
(CDS) and the Solar Ultraviolet Measurements of Emitted Radiation
(SUMER) on the Solar and Heliospheric Observatory (SOHO). The spectral
lines formed in the transition region and corona show considerable
structure and large deviations from a uniform spatial distribution over
the active region. Enhanced EUV emissions in transition region lines
are concentrated in small regions outside the umbra of the sunspot
throughout most of the observing sequence. Only during a short,
active period do we find an enhanced line emission that reaches into
the umbra. Preliminary values for the umbral intensity are given.
Title: On the Origin of Solar Oscillations
Authors: Goode, Philip R.; Strous, Louis H.; Rimmele, Thomas R.;
Stebbins, Robin T.
Bibcode: 1998ApJ...495L..27G
Altcode: 1998astro.ph..1008G
We have made high-resolution observations of the Sun in which we
identify individual sunquakes and see power from these seismic events
being pumped into the resonant modes of vibration of the Sun. A typical
event lasts about 5 minutes. We report the physical properties of
the events and relate them to theories of the excitation of solar
oscillations. We also discuss the local seismic potential of these
events.
Title: Three Dimensional EUV Imaging of Sunspot Regions Observed
with SOHO
Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe,
O.; Maltby, P.; Harrison, R. A.; Rimmele, T.; Wilhelm, K.
Bibcode: 1998ASPC..155..171B
Altcode: 1998sasp.conf..171B
No abstract at ADS
Title: Evidence for Magnetoconvection in a Sunspot Light Bridge
Authors: Rimmele, Thomas R.
Bibcode: 1997ApJ...490..458R
Altcode:
We study a time sequence of the velocity field measured in a sunspot
light bridge classified as photospheric. The data provide clear
evidence for a convective origin of the photospheric light-bridge
phenomenon. Furthermore, the data strongly indicate that a form of
oscillatory magnetoconvection is the physical process responsible
for the formation of the observed light bridge. We observe umbral
dots and find in them a very small upward velocity of order 50 m
s-1. Both the intensity and the velocity signal vary in
time. Some umbral dots fade over a period of about 15-20 minutes and
then reappear at the same location. In the particular sunspot observed,
umbral dots give the impression of being aligned in lanes that appear
to separate individual flux fragments within the umbra.
Title: High Resolution Solar Observations from the Ground
Authors: Rimmele, T.; Beckers, J.; Dunn, R.; Radick, R.; Roeser, M.
Bibcode: 1997hrsa.rept.....R
Altcode:
We describe an ongoing effort to improve the capabilities for achieving
spectroscopic and imaging observations at the highest spatial resolution
at the Sacramento Peak Vacuum Tower Telescope of the National Solar
Observatory. We report on improvements of the optical performance of the
VTT/SP and describe results from the first solar active optics system,
which was recently successfully tested at the VTT/SP. Our final goal is
the implementation of solar adaptive optics at the VTT/SP. We describe
progress and future plans of the adaptive optics program.
Title: Progress in Active Optics at the NSO/SP Vacuum Tower Telescope
Authors: Radick, Richard R.; Rimmele, Thomas R.
Bibcode: 1997SPD....28.1504R
Altcode: 1997BAAS...29..919R
About a year ago, NSO/SP and PL/GPSS jointly began the development
of an active optics system for the Vacuum Tower Telescope at Sac
Peak. Although the immediate objective of this project is to provide a
system for sensing and correcting the slowly varying aberrations in the
optical system of the VTT/SP, the system is also intended to provide
a platform for further development of low order adaptive optics and
ultimately a full atmospheric compensation system for use in solar
imaging. A correlating Shack-Hartmann wavefront sensor, capable of
using solar granulation as its target, and a 97-actuator deformable
mirror, manufactured by Xinetics, Inc., are the key components of
the new system. During March, 1997, the control loop was closed for
the first time at the VTT, and the ability of the wavefront sensor to
function using both small sunspots and granulation was successfully
demonstrated. Further performance and optimization tests at the VTT
are scheduled for May. We will report the results.
Title: High Resolution Observations of Magnetic Elements in the
Visible and the Infrared
Authors: Rimmele, T.; Lin, H.
Bibcode: 1997SPD....28.0248R
Altcode: 1997BAAS...29..901R
High resolution observations of magnetic elements in the visible and
infrared. We report on multi-wavelength observations of plage regions
obtained at the Vacuum Tower Telescope at NSO/Sac-Peak . The data
set includes high resolution images in the G-band (0.43 mu ), the
visible (0.69 mu ) continuum and the infrared (1.6 mu ) continuum. In
addition, deep integration full Stokes vector measurements in the FeI
1.56 mu lines, as well as, Ca-K slit jaw images were obtained. G-band
bright points, which are observed mostly in supergranular lanes, are
also visible as bright points in the visible continuum. Although the
infrared observations are limited in spatial resolution to about 0."4
(the diffraction limit of the VTT/SP), the data indicates that G-band
bright points are also bright in the infrared (1.6 mu ). We also discuss
and compare properties of magnetic knots and small pores. Magnetic
knots, which recently also have been referred to as azimuth centers
(Lites et al. 1994), by definition show no darkening in individual
continuum images. However, in the time-averaged imaging data, and in
particular in the infrared, azimuth centers appear as dark features,
which are clearly distinguishable from the quiet sun background. In
the infrared most azimuth centers are visible as dark features even
in individual snapshots. Many azimuth centers as well as some small
pores are surrounded by a highly structured bright ring, which becomes
more apparent with increasing height of formation. Results of the
polarization analysis in the FeI 1.56 mu lines, including measurements
of weak fields, are presented as well.
Title: The Non-Uniformity in the Sunspot Transition Region
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Rimmele, T.;
Wilhelm, K.
Bibcode: 1997ESASP.404..257B
Altcode: 1997cswn.conf..257B
No abstract at ADS
Title: Transition Region Velocities and Line Profiles in the Sunspot
Region 7981
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T. Thompson, W. T.; Wilhelm, K.
Bibcode: 1997ESASP.404..251B
Altcode: 1997cswn.conf..251B
No abstract at ADS
Title: EUV Line Emission and Time Dependence in the Sunspot Region
NOAA 7981
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
Bibcode: 1997ESASP.404..245B
Altcode: 1997cswn.conf..245B
No abstract at ADS
Title: Limitations Placed on the Time Coverage, Isoplanatic Patch
Size and Exposure Time for Solar Observations Using Image Selection
Procedures in the Presence of Telescope Aberrations
Authors: Beckers, J. M.; Rimmele, T. R.
Bibcode: 1996AAS...189.4209B
Altcode: 1996BAAS...28.1325B
Image selection, adaptive optics and post-facto image restoration
methods are all techniques being used for diffraction limited imaging
with ground-based solar and stellar telescopes. Often these techniques
are used in a hybrid form like e.g. the application of adaptive optics
and/or post-facto image restoration in combination with already good
images obtained by image selection in periods of good seeing. Fried
(JOSA 56, 1372, 1966), Hecquet and Coupinot (J. Optics/Paris 16, 21,
1985) and Beckers ("Solar and Stellar Granulation", Kluwer, Rutten
& Severino Eds, 55, 1988) already discussed the usefulness of
image selection, or the "Lucky Observer" mode, for high resolution
imaging. All assumed perfect telescope optics. In case of moderate
telescope aberrations image selection can still lead to diffraction
limited imaging but only when the atmospheric wavefront aberration
happens to compensate that of the telescope. In this "Very Lucky
Observer" mode the probability of obtaining a good image is reduced
over the un-aberrated case, as are the size of the isoplanatic patch
and the exposure time. We describe an analysis of these effects for
varying telescope aberrations. These result in a strong case for the
removal of telescope aberrations either by initial implementation or
by the use of slow active optics.
Title: Image Quality Improvements at the NSO/Sacramento Peak Vacuum
Tower Telescope
Authors: Radick, R. R.; Dunn, R. B.; Rimmele, T. R.; Stauffer, F. R.;
Wilkins, L. M.
Bibcode: 1996AAS...188.8503R
Altcode: 1996BAAS...28..961R
Recently, an effort has been underway at NSO/Sacramento Peak to improve
the imaging performance of the vacuum tower solar telescope (VTT) by
identifying, characterizing, and correcting optical problems in the
system. Considerable attention has been given to thermal control of
the entrance window to alleviate focus changes and other time-varying
aberrations in the wavefront, and development of a second generation
solar correlation tracker, based on commercially available components,
to eliminate tip-tilt image motion. We are also refiguring one of the
45deg turning flats in the telescope turret, primarily to eliminate
a turned edge that introduces astigmatism. In the next year, we
plan to implement a low-bandwidth active optics system, based on
a workstation-hosted Shack-Hartmann wavefront sensor, generalized
to operate using solar granulation as its target, and a 97 element
deformable mirror, recently purchased from Xinetics Inc. with Air
Force and NSO funds, to correct any remaining residual aberrations in
the VTT optical system.
Title: Wavefront Sensing for Solar Adaptive Optics
Authors: Rimmele, T. R.; Dunn, R. B.; Radick, R. R.
Bibcode: 1996AAS...188.8504R
Altcode: 1996BAAS...28..962R
The National Solar Observatory is developing an adaptive optics
system with the goal to correct atmospheric aberrations in real time
and allow for diffraction limited observations of solar features. A
key component of the AO system is the wavefront sensor (WFS). The Sun
presents unusual problems for wavefront sensing. Unlike the nighttime
sky, the Sun does not provide natural, high-contrast point sources,
and creation of laser beacons bright enough to be visible against the
solar disk poses major technical and operational problems. Wavefront
sensing at arbitrary locations on the Sun requires a sensor capable of
using the solar granulation as its target. We discuss two approaches
to the solar wavefront sensing problem: (a) a modified Shack-Hartmann
sensor, which is based on correlation tracking on images formed by
an array of subapertures , and (b) an amplitude modulation or spatial
filtering procedure, understandable in terms of the classic Foucault
knife-edge test. We compare measurements of atmospheric wavefront
distortions performed simultaneously with a Shack-Hartmann WFS and a
knife-edge WFS. We discuss the performance, limitations and practical
considerations of the two wavefront sensor concepts.
Title: Using Scintillation Measurements to Achieve High Spatial
Resolution in Photometric Solar Observations
Authors: Coulter, R.; Kuhn, J. R.; Rimmele, T.
Bibcode: 1996SoPh..163....7C
Altcode:
The RISE/PSPT (`Radiative Inputs from the Sun to the Earth/Precision
Solar Photometric Telescopes') experiment will attain high differential
photometric precision in full-disk solar images with 1 arc sec
pixels. To achieve this spatial resolution it will be necessary to
use frame selection techniques to minimize the effects of atmospheric
`seeing'. We report here on experiments to use a simple scintillation
monitor as a trigger or `veto' for imaging observations.
Title: Evidence for thin elevated evershed channels.
Authors: Rimmele, T. R.
Bibcode: 1995A&A...298..260R
Altcode:
We report on analysis of sunspot observations carried out with a narrow
band (20mA) filter and present evidence that the Evershed effect is
confined to thin loop-like structures which are elevated above the
continuum height over most parts of the penumbra. The vertical extent
of these loop structures is limited to approximately one photospheric
scale height. The footpoints of these loop structures become visible
in the velocity maps representing the deep photosphere and their
sizes are <=0.5". The position of Evershed velocity filaments
are well correlated with dark filaments seen in intensity maps,
provided intensity and velocity signals compared originate from
the same height in the photosphere. The continuum intensity and
the velocity derived from the core shift of lines formed in the low
photosphere show a significant correlation. However, no significant
correlation is found between the continuum intensity and the velocity
derived from the core shift of spectral lines of medium strength (FeI
5576 A) formed in the upper photosphere. The line profiles measured in
Evershed velocity filaments show enhanced equivalent width and enhanced
full-width-at-half-maximum (FWHM), indicating that a significant amount
of microturbulence is present. We observe systematic differences in
the inclination angle of the magnetic field vector between dark and
bright filaments. Dark filaments are nearly horizontal while in bright
filaments the field vector is more vertical with respect to the solar
surface. The magnetic field strength shows little variation between
dark and bright filaments. In penumbral grains, we observe a small
upward motion on the order 100-200m/s. The line profile in bright
penumbral structures is nearly symmetric, in contrast to the strongly
asymmetric profile found in dark filaments.
Title: Dark Lanes in Granulation and the Excitation of Solar
Oscillations
Authors: Rimmele, T. R.; Goode, P. R.; Strous, L. H.; Stebbins, R. T.
Bibcode: 1995ESASP.376b.329R
Altcode: 1995help.confP.329R; 1995soho....2..329R
No abstract at ADS
Title: Dark Lanes in Granulation and the Excitation of Solar
Oscillations
Authors: Rimmele, Thomas R.; Goode, Philip R.; Harold, Elliotte;
Stebbins, Robin T.
Bibcode: 1995ApJ...444L.119R
Altcode:
We made simultaneous, high-resolution observations of the Sun's
granulation and solar acoustic events in the photosphere. We find that
the acoustic events, which are a local by-product of the excitation
of solar oscillations (Goode, Gough, & Kosovichev 1992), occur
preferentially in the dark, intergranular lanes. At the site of
a typical acoustic event the local granulation becomes darker over
several minutes leading up to the event with a further, abrupt darkening
immediately preceding the peak of the event. Further, the stronger
the acoustic event the darker the granulation. Thus, the excitation of
solar oscillations seems more closely associated with the rapid cooling
occurring in the upper convection layer, rather than the overshooting of
turbulent convection itself. We find no substantial role for so-called
'exploding' granules in the excitation of solar oscillations.
Title: Sun Center Observations of the Evershed Effect
Authors: Rimmele, Thomas R.
Bibcode: 1995ApJ...445..511R
Altcode:
Results of observations of the Evershed effect for a round sunspot
at disk center are presented. Using the 20 mA UBF/FP filter at the
VTT of NSO/Sacramento Peak we recorded a 2 hr time sequence of Fe I
5576.099 A velocity maps, Mn I 5394.675 A core intensity maps, and
white-light images. By computing the 2 hr time average we were able to
filter out the vertical Evershed component of a few hundred m/s from
the background of oscillatory and granular velocities, which dominate
individual images. The averaged velocity fields show distinct filaments
which extend beyond the white-light boundary of the sunspot by as far as
10,000 km. The velocity profile along these filaments is consistent with
the picture of an arched magnetic loop carrying the Evershed flow. These
loops reach their maximum elevation at less than 300 km above continuum
height. The portions of the loops seen in velocity maps have a length
of up to 20,000 km. Within the penumbra the velocity filaments are
correlated with dark filaments observed in the core intensity map of
the temperature-sensitive Mn I line. However, beyond the penumbral
boundary the same velocity filaments coincide with enhanced brightness,
relative to the photospheric intensity, suggesting that the gas in
the downstream legs of the loop is at a higher temperature than the
surrounding photospheric material. The temperature excess in the
downstream legs is of the order of 200 K. A possible explanation is
a standing tube shock that occurs in the downstream legs and near the
penumbral boundary as modeled by Montesinos & Thomas (1993). Some
velocity filaments end in pore-like features which are 5%-10% darker
than the average photosphere and reveal a pronounced redshift.
Title: Restored Solar Velocity Measurements Obtained from the May 10,
1994 Annular Solar Eclipse
Authors: Keil, S. L.; Balasubramaniam, K. S.; Ljungberg, S. K.;
Smaldone, L. A.; Rimmele, T. R.
Bibcode: 1995SPD....26..202K
Altcode: 1995BAAS...27..951K
No abstract at ADS
Title: CLEAR : A Concept for a "Coronagraph and Low Emissivity
Astronomical Reflector" for Solar and Nighttime Observations
Authors: Beckers, J. M.; Kuhn, J.; Neidig, D.; Rabin, R.; Rimmele,
T.; Smartt, R. N.
Bibcode: 1995SPD....26..722B
Altcode: 1995BAAS...27..971B
No abstract at ADS
Title: Photospheric Wave Behavior
Authors: Stebbins, R. T.; Rimmele, T. R.; Goode, P. R.
Bibcode: 1995ASPC...76..354S
Altcode: 1995gong.conf..354S
No abstract at ADS
Title: Observations of Evolving Solar Magnetic Features in the
Infrared and Visible Spectrum
Authors: Rimmele, T.; Schmidt, W.
Bibcode: 1995itsa.conf..363R
Altcode:
No abstract at ADS
Title: On the temporal behaviour of the Evershed effect.
Authors: Rimmele, T. R.
Bibcode: 1994A&A...290..972R
Altcode:
We present the results of high resolution observations of the Evershed
effect, with emphasis on the variation of the Evershed velocities in
time. Using a tunable narrow band filter we recorded time sequences of
the two dimensional penumbral velocity field. The Evershed velocities
are clearly non-stationary. Velocity packets are observed propagating
radially outward towards the penumbral boundary and into the adjacent
quiet photosphere. The propagation speed ranges from 2 to 5.5km/s, with
an average of 3.2+/-1.1km/s. This pattern repeats in a quasi periodic
way on a time scale of order 15 min. Subsequent velocity packets are
separated in space by =~2000-3000km in the radial direction. At a
photospheric height of =~160km we measure an average maximum Doppler
velocity of 4.7+/-0.6km/s. The Doppler velocity seems to have less
variance than propagation speed of the moving velocity features. Both
wave phenomena and transient siphon flows are discussed as possible
explanations for the observed time dependence of the Evershed effect. On
a time scale of 1h we find no observational evidence for the proposed
interchange convection process.
Title: The Evershed effect: a wave phenomenon?
Authors: Rimmele, T.
Bibcode: 1994smf..conf..176R
Altcode:
No abstract at ADS
Title: High Resolution Observations with NSO/KIS Correlation Tracker
Authors: Rimmele, T.; Kentischer, T.; Wiborg, P.
Bibcode: 1993rtpf.conf...24R
Altcode:
No abstract at ADS