The Low Order Wavefront Sensor (LOWFS) is a key component of the Active Optics System of the Daniel K Inouye Solar Telescope. It is designed to measure low order wavefront aberrations in the optical beam arising from gravitational and thermal flexure in the telescope as it moves through the sky during solar observations. These quasi-static aberrations are detrimental to the telescope image quality during seeing-limited observations. The LOWFS measures these quasistatic perturbations by averaging over the atmospheric turbulence. It sends its measurements to the Active Optics System, which computes a solution using the primary (M1) and secondary (M2) mirrors, and sends offsets to the M1 and M2 mirror control systems. The LOWFS is implemented using a 1k x 1k pixel Shack-Hartmann wavefront sensor coupled with a real-time cross correlating image processing engine running at 30 Hz. The real-time engine is implemented in C++ using the Armadillo linear algebra library, enabling equation-style programming with arrays and vectors, achieving essentially the same speed as hand coded loops over the same data structures. The cross correlation is implemented in the frequency domain leveraging the speed of the FFTW Fast Fourier Transform library. The entire realtime engine is embedded inside a DKIST Common Services Framework Controller, allowing for simple command and control of the wavefront sensor computations using the high-level Wavefront Correction Control System software. A Python-based script engine is used to implement various calibration tasks, allowing full access to the SciPy software stack for non-real-time scientific computations. This paper describes the design and implementation of the LOWFS and presents initial results from testing in the DKIST Wavefront Correction System Laboratory.
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.
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.
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.
The Daniel K. Inouye Solar Telescope (DKIST) is a 4-meter solar observatory under construction at Haleakala, Hawaii . The Visible Broadband Imager (VBI) is a first light instrument that will record images at the highest possible spatial and temporal resolution of the DKIST at a number of scientifically important wavelengths . The VBI is a pathfinder for DKIST instrumentation and a test bed for developing processes and procedures in the areas of unit, systems integration, and user acceptance testing. These test procedures have been developed and repeatedly executed during VBI construction in the lab as part of a "test early and test often" philosophy aimed at identifying and resolving issues early thus saving cost during integration test and commissioning on summit.
The VBI team recently completed a bottom up end-to-end system test of the instrument in the lab that allowed the instrument’s functionality, performance, and usability to be validated against documented system requirements. The bottom up testing approach includes four levels of testing, each introducing another layer in the control hierarchy that is tested before moving to the next level. First the instrument mechanisms are tested for positioning accuracy and repeatability using a laboratory position-sensing detector (PSD). Second the real-time motion controls are used to drive the mechanisms to verify speed and timing synchronization requirements are being met. Next the high-level software is introduced and the instrument is driven through a series of end-to-end tests that exercise the mechanisms, cameras, and simulated data processing. Finally, user acceptance testing is performed on operational and engineering use cases through the use of the instrument engineering graphical user interface (GUI).
In this paper we present the VBI bottom up test plan, procedures, example test cases and tools used, as well as results from test execution in the laboratory. We will also discuss the benefits realized through completion of this testing, and share lessons learned from the bottoms up testing process.
The Visible Broadband Imager (VBI) Blue and Red channels are the first Daniel K. Inouye Solar Telescope (DKIST) instruments that have been aligned and tested in a laboratory. This paper describes the optical alignment method of the VBI as performed in the laboratory. The objective of this preliminary alignment is to test and validate the optical alignment method that will be used during final alignment on the telescope, to measure the VBI performances and to verify that it meets specification. The optical alignment method is defined by three major steps. The first step is realized by combining the optical and mechanical models into the Spatial Analyzer (SA) software, and extracting the data serving as target values during alignment. The second step is the mechanical alignment and allows to accurately position the optics in the instrument coordinate system by using a Coordinate Measurement Machine (CMM) arm and a theodolite. This step has led to a great initial positioning and has allowed reaching an initial wavefront error before optical alignment close to the specification. The last step, performed by interferometry, allows fine alignment to compensate the residual aberrations created by misalignment and manufacturing tolerances. This paper presents also an alignment method to compute the shifts and tilts of compensating lenses to correct the residual aberrations. This paper describes first results of the VBI instruments performances measured in the laboratory and confirm the validity of the alignment process that will be reproduced during final alignment on the telescope.
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).
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.
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.
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.
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.
The Visible Broadband Imager (VBI) is one of several first-light instruments of the Daniel K. Inouye Solar Telescope (DKIST, formerly known as the Advanced Technology Solar Telescope (ATST)). Operating at discrete wavelengths within a range of 390-860 nm, the VBI will be capable of sampling the solar atmosphere in several layers at the diffraction limit of DKIST’s 4 meter aperture. The layers are selected by the peak wavelength and bandpass width of its interference filters that have to be manufactured to very tight specifications. We present the results of testing performed at the National Solar Observatory’s Dunn Solar Telescope (DST) to confirm that the requirements were met by the vendor.
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
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.
The Advanced Technology Solar Telescope (ATST), a 4 meter class telescope for observations of the solar
atmosphere currently in construction phase, will generate data at rates of the order of 10 TB/day with its
state of the art instrumentation. The high-priority ATST Visible Broadband Imager (VBI) instrument alone
will create two data streams with a bandwidth of 960 MB/s each. Because of the related data handling issues,
these data will be post-processed with speckle interferometry algorithms in near-real time at the telescope using
the cost-effective Graphics Processing Unit (GPU) technology that is supported by the ATST Data Handling
In this contribution, we lay out the VBI-specific approach to its image processing pipeline, put this into the
context of the underlying ATST Data Handling System infrastructure, and finally describe the details of how
the algorithms were redesigned to exploit data parallelism in the speckle image reconstruction algorithms. An
algorithm re-design is often required to efficiently speed up an application using GPU technology; we have chosen
NVIDIA's CUDA language as basis for our implementation. We present our preliminary results of the algorithm
performance using our test facilities, and base a conservative estimate on the requirements of a full system that
could achieve near real-time performance at ATST on these results.
The Advanced Technology Solar Telescope (ATST) is a 4 meter class telescope for observation of the solar atmosphere
currently in the construction phase. The Visible Broadband Imager (VBI) is a diffraction limited imaging instrument
planned to be the first-light instrument in the ATST instrumentation suite. The VBI is composed of two branches, the
"VBI blue" and the "VBI red", and uses state-of-the-art narrow bandwidth interference filters and two custom designed
high speed filter wheels to take bursts of images that will be re-constructed using a Graphics Processing Unit (GPU)
optimized near-real-time speckle image reconstruction engine. At first light, the VBI instrument will produce
diffraction-limited movies of solar activity at eight discrete wavelengths with a field of view of 2 arc minutes square. In
this contribution, the VBI design team will discuss the capabilities of the VBI and describe the design of the instrument,
highlighting the unique challenges faced in the development of this unique instrument.
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.
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.
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.
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.
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.
The largest solar telescope, the 1.6-m New Solar Telescope (NST) has been installed and is being commissioned
at Big Bear Solar Observatory (BBSO). It has an off-axis Gregorian configuration with a focal ratio of F/52.
Early in 2009, first light scientific observations were successfully made at the Nasmyth focus, which is located
on the east side of the telescope structure. As the first available scientific instruments for routine observation,
Nasmyth focus instrumentation (NFI) consists of several filtergraphs offering high spatial resolution photometry
in G-band 430 nm, Ha 656 nm, TiO 706 nm, and covering the near infrared 1083 nm, 1.6 μm, and 2.2 μm. With
the assistance of a local correlation tracker system, diffraction limited images were obtained frequently over a
field-of-view of 70 by 70 after processed using a post-facto speckle reconstruction algorithm. These data sets not
only serve for scientific analysis with an unprecedented spatial resolution, but also provide engineering feedback
to the NST operation, maintenance and optimization. This paper reports on the design and the implementation
of NFI in detail. First light scientific observations are presented and discussed.
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
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.
We present a speckle interferometry code for solar data taken with the help of an adaptive optics (AO) system.
As any AO correction is only partial there is a need to use post-facto reconstruction algorithms to achieve the
diffraction limit of the telescope over a large field of view most of the observational time. However, data rates of
current and future solar telescopes are ever increasing with camera chip sizes. In order to overcome the tedious
and expensive data handling, we investigate the possibility to use the presented speckle reconstruction program
in a real-time application at telescope sites themselves. The program features Fourier phase reconstruction
algorithms using either an extended Knox-Thompson or a triple correlation scheme. The Fourier amplitude
reconstruction has been adjusted for use with models that take the correction of an AO system into account.
The code has been written in the C programming language and optimized for parallel processing in a multi-processor
environment. We analyze the scalability of the code to find possible bottlenecks. Finally, the phase
reconstruction accuracy is validated by comparison of reconstructed data with satellite data. We conclude that
the presented code is capable to run in future real-time reconstruction applications at solar telescopes if care is
taken that the multi-processor environments have low latencies between the processing nodes.