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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 coude rotator is complete and the installation of the coude 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.

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 Coude Lab beneath the telescope. At the Nasmyth focus, several filtergraphs already in routine operation have offered high spatial resolution photometry in TiO 706 nm, Hα 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 Coude 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-Perot 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 (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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.

The site survey for the Advanced Technology Solar Telescope concluded recently after more than two 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 day-time seeing is often very different between the actual telescope aperture (~30 m) and the ground. Two independent inversion codes have been developed to analyze simultaneously 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 May 2003, which 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)., To appear in the Publications of the Astronomical Society of the Pacific (PASP). Note: Figures are low resolution versions due to file size limitations

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.

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 014 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.

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 OpticsProject. In developing solar MCAO, we bear in mind its possible implementation into the proposed 4 m AdvancedTechnology Solar Telescope (ATST). Two possible relay optical designs feeding an MCAO section and the coude´section of a 4 m off-axis solar telescope, such as the proposed ATST, are presented and discussed here.1. INTRODUCTIONExtending the size of the corrected field of view (FOV) withrespect to the classical adaptive optics (AO) system FOV isone of several new challenges to improving the performanceof astronomical telescopes. Atmospheric turbulence tomogra-phy, which measures the wave front produced by discreteatmo-spheric layers when receiving light beams from several ref-erence sources, has been one of the techniques proposed(Tallon& Foy 1990) to approach such a challenge. Assuming linearaddition (Roddier 1981) of the phase conjugation produced byeach weak turbulent layer, the configuration of guide sources,and the altitudes of the layers, the phase at any given turbulentlayer can be reconstructed. Foy & Labeyrie (1985) proposedto correct each discrete equivalent turbulent layer individuallyby using multiple deformable mirrors (DMs). Such a conceptwas called multiconjugate adaptive optics (MCAO). Many pa-pers have discussed the problem of turbulence tomography(Tallon & Foy 1990; Ragazzoni et al. 1999; Fusco et al. 1999).Tomographic wave-front retrieval (using wave-front measure-ments from several positions in the FOV) has been numericallysimulated by Ellerbroek (1994) and Fusco (1999). More re-cently, experimental closed-loop correction has been demon-strated in the laboratory (Knutsson & Owner-Petersen 2003;Wallace et al. 2003; Langlois et al. 2004c) and at telescopesfor solar observations (Langlois et al. 2004b). In the case ofsolar MCAO, several guiding regions are selected within asingle wave-front sensor with a large FOV (1 –2 ), and thewave front is evaluated using cross-correlation on the subi-mages. This technique has been sucessfully implemented usingboth sunspots and solar granulations as guiding regions, asdiscussed in Langlois et al. (2004b). Figure 1 shows the images

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 4m Advance Technology Solar Telescope (ATST) will be 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, designs are complete, and fabrication has started. 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. 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 laboratory facility. The initial set of five first generation instruments consists of imagers and spectro-polarimeters. 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 status of the telescope, its instrumentation, and the construction of the facility.

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.

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 coude 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.

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.

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.

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.

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 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 coude 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 coude 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.

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.

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 coude 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

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.

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.

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 (

Quantifying the results for a multi-conjugate adaptive optics (MCAO) system is more complex than a traditional adaptive optics (AO) system. The complexity of analyzing a MCAO system stems from using multiple deformable mirrors (DMs) and quantifying the influence functions at the wavefront sensor (WFS). In this paper, analysis tools are developed to quantify MCAO performance. Influence functions from two deformable mirrors are propagated to a WFS using CODEV to simulate an MCAO design comparable to the Dunn Solar Telescope (DST). Using MATLAB, the propagated influence functions are mapped to the appropriate field positions, and reconstructor matrices are built using the mapped influence functions. Next, a correctability analysis was performed using theoretical random phase screens. The developed tools are versatile and useful as a system design tool and in a laboratory setting.

We compare the rms contrast in observed speckle reconstructed G-band images with synthetic filtergrams computed from two magneto-hydrodynamic 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 performance of the Adaptive Optics (AO) system at the DST to supply reliable photometry. We find a considerable discrepancy in 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., Comment: 16 pages, 8 figures

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.

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.

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.

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.

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.

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.

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 Coude section of a 4-M off-axis solar telescope, such as the proposed ATST, are presented and discussed here.

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.

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.

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.

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.

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.

A high-order Adaptive Optical (AO) system for the 65 cm vacuum telescope of the Big Bear Solar Observatory (BBSO) is presented. The Coude-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 2nd 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 × 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 × 1,024 pixel Complex Metal Oxide Semiconductor (CMOS) camera manufactured by Photobit camera. In the 4 × 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-Perot 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-Perot etalons covering a field-of-view (FOV) of about 180″ × 180″.

We present formalism and analysis of three active alignment reconstruction techniques applied to the Advanced Technology Solar Telescope. The three reconstructors generate optical control signals that are a matrix product of a wavefront-sensing signal and the reconstructors themselves. The optical control signals are fed to the six rigid body degrees of freedom of the telescope secondary mirror and the eight bending modes of the primary mirror. The resulting aligned state is a least-squares alignment of the telescope subject to perturbations that result from thermal and gravitational flexures. Two of the reconstructors utilize a single guide object in the telescope field of view and the third reconstructor utilizes three guide objects. One of the single-guide-object reconstructors is developed with an explicit minimum force constraint that minimizes the actuator forces exerted on the telescope primary mirror during active alignment. The force optimized reconstructor also achieves close to the minimum residual wavefront error. Simulation results, optical control analysis, and a discussion of the reconstructor methods and properties are presented.

We present a tracking system that stabilizes atmospheric and instrumental image motion in vacuum tower telescopes. The system is designed to lock on low contrast features, such as solar granulation or other small scale structure. A matrix diode array rapidly scans the scene of interest, usually with a field of 5 arcsec. Images are cross-correlated in real time with a previously recorded reference image of the same area. The drive signal for the image motion corrector, a small, articulated mirror, is generated by measuring the position of the cross correlation maximum. Reference pictures are updated every 30 s in order to adapt to the changing small scale solar features. Performance tests show that the residual image motion in the tracked image is 0.05 arcsec rms compared to a typical 0.5 arcsec rms for the untracked image. The system locks on any small scale structure anywhere on the sun. The bandwidth of the servo system is 40 Hz, or sufficient to stabilize image motion on a meter-class solar telescope.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.