ARGOS the Advanced Rayleigh guided Ground layer adaptive Optics System for the LBT (Large Binocular Telescope) is built by a German-Italian-American consortium. It will be a seeing reducer correcting the turbulence in the lower atmosphere over a field of 2' radius. In such way we expect to improve the spatial resolution over the seeing of about a factor of two and more and to increase the throughput for spectroscopy accordingly. In its initial implementation, ARGOS will feed the two near-infrared spectrograph and imager - LUCI I and LUCI II. The system consist of six Rayleigh lasers - three per eye of the LBT. The lasers are launched from the back of the adaptive secondary mirror of the LBT. ARGOS has one wavefront sensor unit per primary mirror of the LBT, each of the units with three Shack-Hartmann sensors, which are imaged on one detector. In 2010 and 2011, we already mounted parts of the instrument at the telescope to provide an environment for the main sub-systems. The commissioning of the instrument will start in 2012 in a staged approach. We will give an overview of ARGOS and its goals and report about the status and new challenges we encountered during the building phase. Finally we will give an outlook of the upcoming work, how we will operate it and further possibilities the system enables by design.

We have created a new autonomous laser-guide-star adaptive-optics (AO) instrument on the 60-inch (1.5-m) telescope at Palomar Observatory called Robo-AO. The instrument enables diffraction-limited resolution observing in the visible and near-infrared with the ability to observe well over one-hundred targets per night due to its fully robotic operation. Robo-AO is being used for AO surveys of targets numbering in the thousands, rapid AO imaging of transient events and long-term AO monitoring not feasible on large diameter telescope systems. We have taken advantage of cost-effective advances in deformable mirror and laser technology while engineering Robo-AO with the intention of cloning the system for other few-meter class telescopes around the world.

From the ardent bucklers used during the Syracuse battle to set fire to Romans’ ships to more contemporary piezoelectric deformable mirrors widely used in astronomy, from very large voice coil deformable mirrors considered in future Extremely Large Telescopes to very small and compact ones embedded in Multi Object Adaptive Optics systems, this paper aims at giving an overview of Deformable Mirror technology for Adaptive Optics and Astronomy. First the main drivers for the design of Deformable Mirrors are recalled, not only related to atmospheric aberration compensation but also to environmental conditions or mechanical constraints. Then the different technologies available today for the manufacturing of Deformable Mirrors will be described, pros and cons analyzed. A review of the Companies and Institutes with capabilities in delivering Deformable Mirrors to astronomers will be presented, as well as lessons learned from the past 25 years of technological development and operation on sky. In conclusion, perspective will be tentatively drawn for what regards the future of Deformable Mirror technology for Astronomy.

In order to prepare for the construction phase of the two Deformable Mirrors (DMs), which will be used in the Thirty Meter Telescope (TMT) first light Adaptive Optics (AO) system, Cilas has advanced the design of these two large size piezo DMs and has manufactured and tested a scaled demonstration prototype. The work done allowed significant reduction of the risks related to the demanding specifications of the TMT DMs; the main issues were: (i) Large pupil (up to 370 mm) and high order (up to 74x74); (ii) Relatively low operational temperature (DMs working at -30°C); (iii) New piezo material. It is important to develop such a prototype to take into account these three specifications all together (dimension, low temperature and new piezo material). The new prototype is a 6x60 actuators and has the same characteristics as the future TMT DMs. In this paper, we give the conclusions of the work through the presentation of the following items: (i) Design and finite element analysis of the two DMs and prototype; (ii) Test results obtained with the prototype with validation of the finite element analysis and compliance with the TMT AO specifications; (iii) Special focus on thermal behavior, actuator reliability and shape at rest stability.

A low-cost silicon unimorph deformable mirror (DM) with 214 actuators is presented. The finite element simulation indicates that the designed DM has an excellent correction performance for both low order and high order aberrations. The experimental actuator deflection is about 2μm at 100V. This DM has the potential to be used for astronomical adaptive optics.

Recently, Adaptive Secondary Mirrors showed excellent on-sky results in the Near Infrared wavelengths. They currently provide 30mm inter-actuator spacing and about 1 kHz bandwidth. Pushing these devices to be operated at visible wavelengths is a challenging task. Compared to the current systems, working in the infrared, the more demanding requirements are the higher spatial resolution and the greater correction bandwidth. In fact, the turbulence scale is shorter and the parameter variation is faster. Typically, the former is not larger than 25 mm (projected on the secondary mirror) and the latter is 2 kHz, therefore the actuator has to be more slender and faster than the current ones. With a soft magnetic composite core, a dual-stator and a single-mover, VRALA, the actuator discussed in this paper, attains unprecedented performances with a negligible thermal impact. Pre-shaping the current required to deliver a given stroke greatly simplifies the control system, whose output supplies the current generator. As the inductance depends on the mover position, the electronics of this generator, provided with an inductance measure circuit, works also as a displacement sensor, supplying the control system with an accurate feed-back signal. A preliminary prototype, built according to the several FEA thermo-magnetic analyses, has undergone some preliminary laboratory tests. The results of these checks, matching the design results in terms of power and force, show that the the magnetic design addresses the severe specifications.

Adaptive Optics observations have dramatically improved the quality and versatility of high angular resolution measurements of the center of our Galaxy. In this paper, we quantify the quality of our Adaptive Optics observations and report on the astrometric precision for the young stellar population that appears to reside in a stellar disk structure in the central parsec. We show that with our improved astrometry and a 16 year baseline, including 10 years of speckle and 6 years of laser guide star AO imaging, we reliably detect accelerations in the plane of the sky as small as 70 μas yr^-2 (~2.5 km s^-1 yr^-1) and out to a projected radius from the supermassive black hole of 1."5 (~0.06 pc). With an increase in sensitivity to accelerations by a factor of ~6 over our previous efforts, we are able to directly probe the kinematic structure of the young stellar disk, which appears to have an inner radius of 0."8. We find that candidate disk members are on eccentric orbits, with a mean eccentricity of < e > = 0.30 ± 0.07. Such eccentricities cannot be explained by the relaxation of a circular disk with a normal initial mass function, which suggests the existence of a top-heavy IMF or formation in an initially eccentric disk.

The paper motivates the science requirements for high-contrast imaging illustrated by actual observation results. After an introduction to the high-contrast-imaging problem composed of extreme adaptive optics, coronagraphy, wave-front control an post-processing, the state-of-the-art will be reviewed putting emphasis on existing instruments and those that are near completion: LBT-FLAO, Magellan Mag AO, Palomar P3K / P1640, Subaru SCExAO, Gemini GPI, and VLT SPHERE.

Adaptive Optics systems, today available on 8-10m class telescopes are playing a significant role in the study of our solar system bodies. We describe three main science cases i) small solar system bodies ii) satellites of giant planets iii) giant planets atmospheres. We describe recent results acquired with these systems in these fields. We discuss the limitation and potential of AO systems for these studies, and address the problem of observability specific to moving targets. The potential for planetary science of future and improved AO systems is described.

Laser Guide Star (LGS) Adaptive Optics (AO) on large telescopes has recently become a very productive science tool for the astronomical community. Astronomical objects can now be observed at an unprecedented resolution over much of the sky. The science enabled by LGS AO and the capabilities and limitations of these systems will be discussed, along with the lessons learned that can be applied to LGS AO systems on existing and planned telescopes.

We present a summary update of sodium laser guidestar technology, including an overview of the results from a series of Laser Guidestar Workshops hosted by the Center for Adaptive Optics over the past few years. There has been considerable advancement in the understanding of laser light interaction with mesospheric sodium which has an impact on the choice of laser systems where the objective is to produce the best wavefront measurement with a minimum of laser power and expense. We will also summarize our efforts on an NSF funded MRI program to build a high-Strehl AO system for imaging and spectroscopy covering the near IR science bands from 0.9 to 2.2 micron wavelength. The system includes a new 10 watt pulsed fiber laser developed by Lawrence Livermore National Laboratory tuned in spectral and pulse format for optimum sodium return.

Large telescopes equipped with adaptive optics require 20-25W CW 589-nm sources with emission linewidths of ~5 MHz. These Guide Star (GS) lasers should also be highly reliable and simple to operate and maintain for many years at the top of a mountain facility. Under contract from ESO, industrial partners TOPTICA and MPBC are nearing completion of the development of GS lasers for the ESO VLT, with delivery of the first of four units scheduled for December 2012. We report on the design and performance of the fully-engineered Pre-Production Unit (PPU), including system reliability/availability analysis, the successfully-concluded qualification testing, long-term component and system level tests and long-term maintenance and support planning. The chosen approach is based on ESO's patented narrow-band Raman Fiber Amplifier (EFRA) technology. A master oscillator signal from a linearly-polarized TOPTICA 20-mW, 1178-nm CW diode laser, with stabilized emission frequency and controllable linewidth up to a few MHz, is amplified in an MPBC polarization-maintaining (PM) RFA pumped by a high-power 1120-nm PM fiber laser. With efficient stimulated Brillouin scattering suppression, an unprecedented 40W of narrow-band RFA output has been obtained. This is then mode-matched into a resonant-cavity doubler with a free-spectral-range matching the sodium D₂a to D₂b separation, allowing simultaneous generation of an additional frequency component (D₂b line) to re-pump the sodium atom electronic population. With this technique, the return flux can be increased without having to resort to electro-optical modulators and without the risk of introducing optical wave front distortions. The demonstrated output powers with doubling efficiencies >80% at 589 nm easily exceed the 20W design goal and require less than 700 W of electrical power. In summary, the fiber-based guide star lasers provide excellent beam quality and are modular, turn-key, maintenance-free, reliable, efficient, and ruggedized devices whose compactness allows installation directly onto the launch telescope structure.

We present laser results of OPS structures based on highly strained InGaAs quantum wells emitting at 1178nm and frequency doubled to produce high power, high beam quality laser radiation at 589nm. The laser architecture is the same as in our commercial offerings, allowing us to achieve the desired results with a system significantly simpler than alternative approaches.

Almost all sodium laser guide star (LGS) systems in the world are based on pulsed lasers. We review the relevant sodium physics and compare different laser pulse formats. Selected formats are discussed on the basis of numerical simulation results. One of the key findings is that the brightness of most existing LGS facilities could be boosted at, as we argue, reasonable expense. Recommendations are presented to enhance the LGS return flux and to design future LGS lasers, including those suitable for spot tracking in the mesosphere to mitigate the spot elongation problem.

GeMS, the Gemini Laser Guide Star Multi-Conjugate Adaptive Optics facility system, has seen first light in December 2011, and has already produced images with H band Strehl ratio in excess of 35% over fields of view of 85x85 arcsec, fulfilling the MCAO promise. In this paper, we report on these early results, analyze trends in performance, and concentrate on key or novel aspects of the system, like centroid gain estimation, on-sky non­ common path aberration estimation. We also present the first astrometric analysis, showing very encouraging results.

The ESO Adaptive Optics Facility (AOF) consists in an evolution of one of the ESO VLT unit telescopes to a laser driven adaptive telescope with a deformable mirror in its optical train. The project has completed the procurement phase and several large structures have been delivered to Garching (Germany) and are being integrated (the AO modules GRAAL and GALACSI and the ASSIST test bench). The 4LGSF Laser (TOPTICA) has undergone final design review and a pre-production unit has been built and successfully tested. The Deformable Secondary Mirror is fully integrated and system tests have started with the first science grade thin shell mirror delivered by SAGEM. The integrated modules will be tested in stand-alone mode in 2012 and upon delivery of the DSM in late 2012, the system test phase will start. A commissioning strategy has been developed and will be updated before delivery to Paranal. A substantial effort has been spent in 2011-2012 to prepare the unit telescope to receive the AOF by preparing the mechanical interfaces and upgrading the cooling and electrical network. This preparation will also simplify the final installation of the facility on the telescope. A lot of attention is given to the system calibration, how to record and correct any misalignment and control the whole facility. A plan is being developed to efficiently operate the AOF after commissioning. This includes monitoring a relevant set of atmospheric parameters for scheduling and a Laser Traffic control system to assist the operator during the night and help/support the observing block preparation.

CANARY is an on-sky demonstrator adaptive optics (AO) system that in 2010 provided the first on-sky demonstration of open-loop tomographic adaptive optics correction using natural guide stars (NGS). Phase B of the CANARY experiment aims to extend the instrument from its original configuration by also measuring wavefronts from four offaxis Rayleigh laser guide stars (LGS). This upgrade allows CANARY to perform tomographic wavefront sensing over a 2.5arcminute field of view using any mix of up to seven off-axis wavefront sensors (four LGS and three NGS) simultaneously. AO correction within CANARY is performed on-axis along a single line of sight using a 52-actuator deformable mirror being controlled in open-loop. Here we give an overview of the Phase B LGS system, discuss the calibration of a mixed NGS/LGS tomographic system and present the recent laboratory and on-sky results from the Phase B commissioning.

NACO is the famous and versatile diffraction limited NIR imager and spectrograph at the VLT with which ESO celebrated 10 years of Adaptive Optics. Since two years a substantial effort has been put in understanding and fixing issues that directly affect the image quality and the high contrast performances of the instrument. Experiments to compensate the non-common-path aberrations and recover the highest possible Strehl ratios have been carried out successfully and a plan is hereafter described to perform such measurements regularly. The drift associated to pupil tracking since 2007 was fixed in october 2011. NACO is therefore even more suited for high contrast imaging and can be used with coronagraphic masks in the image plane. Some contrast measurements are shown and discussed. The work accomplished on NACO will serve as reference for the next generation instruments on the VLT, especially the ones working at the diffraction limit and making use of angular differential imaging (i.e. SPHERE, VISIR, and possibly ERIS).

ESO's Multi-conjugate Adaptive-optics Demonstrator (MAD) was a prototype designed and built to demonstrate wide-field adaptive optics science on large telescopes. The outstanding results obtained during commissioning and guaranteed time observations (GTO) prompted ESO to issue and open call to the community for 23 science demonstration (SD) observing nights distributed in three runs (in order to provide access to the summer an winter skies). Thus, in total MAD was used for science for 33 nights including the 10 nights of GTO time. date, 19 articles in refereed journals (including one in Nature) have been published based fully or partially o MAD data. To the best of our knowledge, these are not only the first, but also the only scientific publication from MCAO instruments world-wide to date (at least in Astronomy). The scientific impact of these publication, as measured by the h-index, is comparable to that of other AO instruments on the VLT, although over the years these instruments have been allocated many more nights than MAD. In this contribution we present an overview of the scientific results from MAD and a more detailed discussion of the most cited papers.

We present the results from the commissioning of the Gemini South Adaptive Optics Imager (GSAOI). Capable of delivering diffraction limited images in the near-infrared, over an 85′′ ×85′′ square field-of-view, GSAOI was designed for use with the Gemini Multi-Conjugate Adaptive Optics (GeMS) system in operation at the Gemini South Observatory. The instrument focal plane, covered by an array of four HAWAII-2RG detectors, contains 4080×4080 pixels and has a plate scale of 0.02′′ – thus capitalizing on the superb image quality delivered by both the all-refractive optical design of GSAOI and the Gemini South MCAO system. Here, we discuss our preliminary findings from the GSAOI commissioning, concentrating on detector characterization, on-sky performance and system throughput. Further specifics about the Gemini MCAO system can be found in other presentations at this conference.

To image faint substellar companions obscured by the stellar halo and speckles, scattered light from the bright primary star must be removed in hardware or software. We apply the "locally-optimized combination of images" (LOCI) algorithm to 1-minute Keck Observatory snapshots of GKM dwarfs in the Hyades using source diversity to determine the most likely PSF. We obtain a mean contrast of 10^-2 at 0".01, 10^-4 at <1", and 10^-5 at 5". New brown dwarf and low-mass stellar companions to Hyades primaries are found in a third of the 84 targeted systems. This campaign shows the efficacy of LOCI on snapshot imaging as well as on bright wide binaries with off-axis LOCI, reaching contrasts sufficient for imaging 625-Myr late-L/early-T dwarfs purely in post-processing.

We present a ground-based technique to detect or follow-up long-period exoplanets via precise relative astrometry of host stars using Multi-Conjugate Adaptive Optics (MCAO) on 8 meter telescopes equipped with diffractive masks. MCAO improves relative astrometry by sharpening PSFs, reducing the star centroiding error, and by providing a spatially stable, more easily modeled PSF. However, exoplanet mass determination requires multi-year reference grid stability of ~10-100 uas or nanometer-level stability on the long-term average of out-of-pupil phase errors, which is difficult to achieve with MCAO. The diffractive pupil technique calibrates dynamic distortion via extended diffraction spikes generated by a dotted primary mirror, which are referenced against a grid of background stars. We calculate the astrometic performance of a diffractive 8-meter telescope with diffraction-limited MCAO in K using analytical techniques and a simplified MCAO simulation. Referencing the stellar grid to the diffraction spikes negates the cancellation of Differential Tip/Tilt Jitter normally achieved with MCAO. However, due to the substantial gains associated with sharper, more stable PSFs, diffractive 8-m MCAO reaches ~ 4-6 μas relative astrometric error per coordinate in one hour on a bright target star (K ~ 7) in fields of moderate stellar density (~10 stars arcmin^-2). Final relative astrometric precision with MCAO is limited by atmospheric differential tip/tilt jitter.

The purpose of this paper is to give an overview of the state of the art wavefront sensor detectors developments held in Europe for the last decade. The success of the next generation of instruments for 8 to 40-m class telescopes will depend on the ability of Adaptive Optics (AO) systems to provide excellent image quality and stability. This will be achieved by increasing the sampling, wavelength range and correction quality of the wave front error in both spatial and time domains. The modern generation of AO wavefront sensor detectors development started in the late nineties with the CCD50 detector fabricated by e2v technologies under ESO contract for the ESO NACO AO system. With a 128x128 pixels format, this 8 outputs CCD offered a 500 Hz frame rate with a readout noise of 7e-. A major breakthrough has been achieved with the recent development by e2v technologies of the CCD220. This 240x240 pixels 8 outputs EMCCD (CCD with internal multiplication) has been jointly funded by ESO and Europe under the FP6 programme. The CCD220 and the OCAM2 camera that operates the detector are now the most sensitive system in the world for advanced adaptive optics systems, offering less than 0.2 e readout noise at a frame rate of 1500 Hz with negligible dark current. Extremely easy to operate, OCAM2 only needs a 24 V power supply and a modest water cooling circuit. This system, commercialized by First Light Imaging, is extensively described in this paper. An upgrade of OCAM2 is foreseen to boost its frame rate to 2 kHz, opening the window of XAO wavefront sensing for the ELT using 4 synchronized cameras and pyramid wavefront sensing. Since this major success, new developments started in Europe. One is fully dedicated to Natural and Laser Guide Star AO for the E-ELT with ESO involvement. The spot elongation from a LGS Shack Hartman wavefront sensor necessitates an increase of the pixel format. Two detectors are currently developed by e2v. The NGSD will be a 880x840 pixels CMOS detector with a readout noise of 3 e (goal 1e) at 700 Hz frame rate. The LGSD is a scaling of the NGSD with 1760x1680 pixels and 3 e readout noise (goal 1e) at 700 Hz (goal 1000 Hz) frame rate. New technologies will be developed for that purpose: advanced CMOS pixel architecture, CMOS back thinned and back illuminated device for very high QE, full digital outputs with signal digital conversion on chip. In addition, the CMOS technology is extremely robust in a telescope environment. Both detectors will be used on the European ELT but also interest potentially all giant telescopes under development. Additional developments also started for wavefront sensing in the infrared based on a new technological breakthrough using ultra low noise Avalanche Photodiode (APD) arrays within the RAPID project. Developed by the SOFRADIR and CEA/LETI manufacturers, the latter will offer a 320x240 8 outputs 30 microns IR array, sensitive from 0.4 to 3.2 microns, with 2 e readout noise at 1500 Hz frame rate. The high QE response is almost flat over this wavelength range. Advanced packaging with miniature cryostat using liquid nitrogen free pulse tube cryocoolers is currently developed for this programme in order to allow use on this detector in any type of environment. First results of this project are detailed here. These programs are held with several partners, among them are the French astronomical laboratories (LAM, OHP, IPAG), the detector manufacturers (e2v technologies, Sofradir, CEA/LETI) and other partners (ESO, ONERA, IAC, GTC). Funding is: Opticon FP6 and FP7 from European Commission, ESO, CNRS and Université de Provence, Sofradir, ONERA, CEA/LETI and the French FUI (DGCIS).

This paper describes the design and testing of a prototype high frame rate CCD imager called the polar coordinate detector developed as part of a project led by the W. M. Keck Observatory (WMKO) and funded by the Adaptive Optics Development Program and the Thirty Meter Telescope (TMT) Project. The polar coordinate detector is designed to address the problem of adaptive optics (AO) laser guide star (LGS) spot image elongation in Shack Hartmann wavefront sensors for extremely large telescopes. The prototype detector, designated the CCID-61, was developed in collaboration with the MIT Lincoln Laboratory. The CCID-61 implements a detector for one quadrant (30 x 30 subapertures) of the planned 60 x 60 subaperture LGS wavefront sensors of the TMT early light AO system NFIRAOS. Testing of front illuminated, packaged detectors has been completed and performance results including read noise, readout speed, charge diffusion, and dark current are reported.

The Adaptive Optics Lucky Imager (AOLI) is a new instrument under development to demonstrate near diffraction limited imaging in the visible on large ground-based telescopes. We present the adaptive optics system being designed for the instrument comprising a large stroke deformable mirror, fixed component non-linear curvature wavefront sensor and photon-counting EMCCD detectors. We describe the optical design of the wavefront sensor where two photoncounting CCDs provide a total of four reference images. Simulations of the optical characteristics of the system are discussed, with their relevance to low and high order AO systems. The development and optimisation of high-speed wavefront reconstruction algorithms are presented. Finally we discuss the results of simulations to demonstrate the sensitivity of the system.

This paper summarizes the activities and the principal results achieved during the commissioning of the two Natural Guide Star (NGS) AO systems called FLAO#1 & 2 installed at the bent Gregorian focal stations of the 2x8.4m Large Binocular Telescope (LBT). The commissioning activities of FLAO#1 took place in the period February 2010 - October 2011, while FLAO#2 commissioning started in December 2011 and should be completed by November 2012. The main results of the commissioning campaign are presented in terms of the H-band Strehl Ratio values achieved under different observing conditions. We will also describe the automatic procedures to configure and set-up the FLAO systems, and in particular the modal gain optimization procedure, which has been proven to be a very important one in achieving the nominal performance. Finally, some of the results achieved in two science runs using the near infra-red camera PISCES are briefly highlighted.

LINC-NIRVANA will employ four wave front sensors to realize multi-conjugate correction on both arms of a Fizeau interferometer for LBT. Of these, one of the two ground-layer wave front sensors, together with its infrared test camera, comprise a stand-alone test platform for LINC-NIRVANA. Pathfinder is a testbed for full LINC-NIRVANA intended to identify potential interface problems early in the game, thus reducing both technical, and schedule, risk. Pathfinder will combine light from multiple guide stars, with a pyramid sensor dedicated to each star, to achieve ground-layer AO correction via an adaptive secondary: the 672-actuator thin shell at the LBT. The ability to achieve sky coverage by optically coadding light from multiple stars has been previously demonstrated; and the ability to achieve correction with an adaptive secondary has also been previously demonstrated. Pathfinder will be the first system at LBT to combine both of these capabilities. Since reporting our progress at A04ELT2, we have advanced the project in three key areas: definition of specific goals for Pathfinder tests at LBT, more detail in the software design and planning, and calibration. We report on our progress and future plans in these three areas, and on the project overall.

The Gemini Multi-Conjugate Adaptive Optics System (GeMS} began its on-sky commissioning in January 20ll. The system provides high order wide-field corrections using a constellation of five Laser Guide Stars. In December 20ll, commissioning culminated in images with a FWHM of 80±2mas at 1.65 microns (H band} over an 87 x 87 arcsccond field of view. The first images have already demonstrated the scientific potential of GeMS, and after more than a year of commissioning GeMS is finally close to completion and ready for science. This paper presents a general status of the GeMS project and summarizes the achievements made during more than a year of commissioning. The characterization of GeMS performance is presented in a companion paper: "GeMS on-sky results" , R.igaut ct al. Here we report on the sub-systems' performance, discuss current limitations and present proposed upgrades. The integration of GeMS into the observatory operational scheme is detailed. Finally, we present the plans for next year's operations with GeMS.

The heart of the 6.5 Magellan AO system (MagAO) is a 585 actuator adaptive secondary mirror (ASM) with <1 msec response times (0.7 ms typically). This adaptive secondary will allow low emissivity and high-contrast AO science. We fabricated a high order (561 mode) pyramid wavefront sensor (similar to that now successfully used at the Large Binocular Telescope). The relatively high actuator count (and small projected ~23 cm pitch) allows moderate Strehls to be obtained by MagAO in the “visible” (0.63-1.05 μm). To take advantage of this we have fabricated an AO CCD science camera called "VisAO". Complete “end-to-end” closed-loop lab tests of MagAO achieve a solid, broad-band, 37% Strehl (122 nm rms) at 0.76 μm (i’) with the VisAO camera in 0.8” simulated seeing (13 cm ro at V) with fast 33 mph winds and a 40 m Lo locked on R=8 mag artificial star. These relatively high visible wavelength Strehls are enabled by our powerful combination of a next generation ASM and a Pyramid WFS with 400 controlled modes and 1000 Hz sample speeds (similar to that used successfully on-sky at the LBT). Currently only the VisAO science camera is used for lab testing of MagAO, but this high level of measured performance (122 nm rms) promises even higher Strehls with our IR science cameras. On bright (R=8 mag) stars we should achieve very high Strehls (>70% at H) in the IR with the existing MagAO Clio2 (λ=1-5.3 μm) science camera/coronagraph or even higher (~98% Strehl) the Mid-IR (8-26 microns) with the existing BLINC/MIRAC4 science camera in the future. To eliminate non-common path vibrations, dispersions, and optical errors the VisAO science camera is fed by a common path advanced triplet ADC and is piggy-backed on the Pyramid WFS optical board itself. Also a high-speed shutter can be used to block periods of poor correction. The entire system passed CDR in June 2009, and we finished the closed-loop system level testing phase in December 2011. Final system acceptance (“pre-ship” review) was passed in February 2012. In May 2012 the entire AO system is was successfully shipped to Chile and fully tested/aligned. It is now in storage in the Magellan telescope clean room in anticipation of “First Light” scheduled for December 2012. An overview of the design, attributes, performance, and schedule for the Magellan AO system and its two science cameras are briefly presented here.

The first of a new generation of high actuator density AO systems developed for large telescopes, PALM-3000 is optimized for high-contrast exoplanet science but will support operation with natural guide stars as faint as V ~ 18. PALM-3000 began commissioning in June 2011 on the Palomar 200" telescope and has to date over 60 nights of observing. The AO system consists of two Xinetics deformable mirrors, one with 66 by 66 actuators and another with 21 by 21 actuators, a Shack-Hartman WFS with four pupil sampling modes (ranging from 64 to 8 samples across the pupil), and a full vector matrix multiply real-time system capable of running at 2KHz frame rates. We present the details of the completed system, and initial results. Operating at 2 kHz with 8.3cm pupil sampling on-sky, we have achieved a K-band Strehl ratio as high as 84% in ~1.0 arcsecond visible seeing.

Perturbations affecting image formation on ground-based telescopes are composed of signals that are not only generated by the atmosphere. They often include vibrations induced by wind excitation on the system's structure, or induced by other sources of excitation like cryo-coolers, shutters, etc. Using state-space control design techniques (e.g., LQG control), efficient perturbation compensation can be obtained in adaptive optics systems. This requires in return an accurate dynamical perturbation model with manageable complexity. The purpose of this paper is to investigate how tip/ tilt state-space models can be constructed and identified from wavefront sensor (WFS) measurements and used for tip/ tilt correction. Several off-the-shelf time-domain identification approaches are considered, ranging from techniques such as subspace identification to extended Kalman filter. Results are compared with controllers that do not account for vibrations, like an integrator or an MMSE reconstructor. Performance improvement is illustrated by replay with on-sky data sets from Gemini South (GeMS and Altair).

While it is attractive to integrate a deformable mirror (DM) for adaptive optics (AO) into the telescope itself rather than using relay optics within an instrument, the resulting large DM can be expensive, particularly for extremely large telescopes. A low-cost approach for building a large DM is to use voice-coil actuators, and rely on feedback from mechanical sensors to improve the dynamic response of the mirror sufficiently so that it can be used in a standard AO control system. The use of inexpensive voice-coil actuators results in many lightly- damped structural resonances within the desired control bandwidth. We present a robust control approach for this problem, and demonstrate performance in a closed-loop AO simulation, incorporating realistic models of low-cost actuators and sensors. The first contribution is to demonstrate that high-bandwidth active damping can be robustly implemented even with non-collocated sensors, by relying on the "acoustic limit" of the structure where the modal bandwidth exceeds the modal spacing. Next we introduce a novel local control approach, which significantly improves the high spatial frequency performance relative to collocated position control, but without the robustness challenges associated with a global control approach. The combination of these "inner" control loops results in DM command response that is demonstrated to be sufficient for integration within an AO system.

Reduction of tip and tilt vibrations at the Gemini South MCAO System (GeMS) is addressed in this paper. A frequency framework for the synthesis of controllers is described, with particular emphasis on the search for better closed-loop performances by minimizing a H₂ norm of the tilt residuals. Previous results have shown that modeling the turbulence via identification tools using standard AR or Laplace representations can lead to non-optimal solutions, resulting in excessive rejection of certain frequencies or an unbalanced residual spectrum due to poor modeling of vibrations. In this novel approach we reconstruct the open loop slopes (pseudo-open-loop) from on-sky data and then perform a fine tuning of the controller by finding the parameters that minimize the variance of residuals during a sequence of closed-loop runs with increasing controller complexity. Although the method is not optimal, it effectively rejects the main vibrations in the loop and it also improves the overall performance of the system. The method is compared to two standard integrators: one with fixed gain and the other with optimized integral gain. Results show substantial improvements of this new method when compared to the classical integrator.

In modern adaptive optics systems, lightly damped sinusoidal oscillations resulting from telescope structural vibrations have a significant deleterious impact on the quality of the image collected at the detector plane. Such oscillations are often at frequencies beyond the bandwidth of the wave-front controller that therefore is either incapable of rejecting them or might even amplify their detrimental impact on the overall AO performance. A technique for the rejection of periodic disturbances acting at the output of unknown plants, which has been recently presented in literature, has been adapted to the problem of rejecting vibrations in AO loops. The proposed methodology aims at estimating phase and amplitude of the harmonic disturbance together with the response of the unknown plant at the frequency of vibration. On the basis of such estimates, a control signal is generated to cancel out the periodic perturbation. Additionally, the algorithm can be easily extended to cope with unexpected time variations of the vibrations frequency by adding a frequency tracking module based either on a simple PLL architecture or on a classical extended Kalman filter. Oversampling can be also easily introduced to efficiently correct for vibrations approaching the sampling frequency. The approach presented in this contribution is compared against a different algorithm for vibration rejection available in literature, in order to identify drawbacks and advantages. Finally, the performance of the proposed vibration cancellation technique has been tested in realistic scenarios defined exploiting tip/tilt measurements from MACAO and NACO

LGS wavefront sensing is a topic of importance for future ELTs. However, the elongation effect makes this task particularly difficult on a large apertures, and require large format detectors. An alternative solution is to use quad-cell types wavefront sensors : either shack-hartmann, or pyramid (using only 4 pixels per phase measurement), or yaw (an optical differentiation wavefront sensor proposed recently, also using 4 pixels, like the pyramid). We compare the performance of these devices and we develop a common model of operation, so that their behavior can be directly compared and their differences easily enlightened.

High-contrast imaging is a growing observational technique aimed at discovering and characterizing extrasolar planets. The Gemini Planet Imager (GPI) is designed to achieve contrast ratios of 10^-6 - 10^-7 and requires unprecedented wavefront correction and coronagraphic control of diffraction. G PI is a facility instrument now undergoing integration and testing and is scheduled for first light on the 8-m Gemini South telescope towards the end of 2012. In this paper, we focus on the wavefront sensing and correction aspects of the instrument. To measure the wavefront, GPI combines a Shack-Hartmann wavefront sensor and a high-accuracy infrared interferometric wavefront calibration system. The Shack-Hartmann wavefront sensor uses 1700 subapertures to precisely sample the wavefront at 1.5 kHz and features a spatial filter to prevent aliasing. The wavefront calibration system measures the slower temporal frequency errors as well as non-common path aberrations. The wavefront correction is performed using a two-stage adaptive optics system employing a 9x9 piezoelectric deformable mirror and a 43x43 actuators MEMS deformable mirror operating in a woofer-tweeter configuration. Finally, an image sharpening technique is used to further increase the contrast of the final image. In this paper, we describe the three wavefront sensing methods and how we combine their respective information to achieve the best possible contrast.

Direct detection and spectral characterization of extra-solar planets is one of the most exciting but also challenging areas in modern astronomy. The challenge is due to the very large contrast between the host star and the planet at very small angular separations. SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research in Europe [1]) is a secondgeneration instrument for the ESO VLT dedicated to this scientific objective. It combines an extreme adaptive optics system [2], various coronagraphic devices and a suite of focal instruments providing imaging, integral field spectroscopy and polarimetric capabilities in the visible and near-infrared spectral ranges. The limitation of such a high contrast imaging system is mainly driven by the presence of intensity residual in the scientific focal plane, caused by uncorrected quasi-static optical aberrations upstream of the coronagraphic mask. The measurement and compensation of these aberrations is mandatory in order to reach the level of contrast requested by exoplanet imaging. We present in this paper the final experimental validation of the baseline method developed in the framework of SPHERE instrument for the conpensation of NCPA. The method is based on a differential measurement with phase diversity, and a compensation with an optimised modification of reference slopes.

We present the results of a sky source based, phase diversity experiment at the W. M. Keck Observatory to retrieve the global wavefront static aberration from the telescope primary mirror to the science imager (NIRC2). The context of this study is a point spread function reconstruct (PSF-R) project for the Keck-II and Gemini- North adaptive optics systems. We demonstrate that if we select couples of in/out-of-focus PSF with identical seeing (determined with a deformable mirror based seeing monitor), retrieving the global static wavefront from AO corrected sky images is indeed possible. A sensitivity analysis shows that the reconstructed wavefront accuracy is very sensitive to errors in the knowledge of the system's optical parameters, and an accuracy of less than 1% is required. Recommendations for an accurate sky-based phase diversity static wavefront reconstruction are given, as well as our plan for the next steps of this project at the W. M. Keck Observatory.

The GMT laser tomography adaptive optics (LTAO) system design has a truth sensor guiding on a natural guide star. The truth sensor is used to measure telescope segment piston errors and measure slowly varying non- common path aberrations. The challenge lies in measuring segment piston using faint natural guide stars and the wavefront delivered by the LTAO system. This requires a sensor that can make a direct phase measurement. It is demonstrated that an infrared, AO-corrected, unmodulated pyramid or roof wavefront sensor can make the required measurements at 10 Hz for stars brighter than magnitude 17 at H- or K-band.

Nowadays, the adaptive optics (AO) system is of fundamental importance to reduce the effect of atmospheric turbulence on the images formed on large ground telescopes. In this paper the AO system takes advantage of the knowledge of the current turbulence characteristics, that are estimated by data, to properly control the deformable mirrors. The turbulence model considered in this paper is based on two assumptions: considering the turbulence as formed by a discrete set of layers moving over the telescope lens, and each layer is modeled as a Markov-Random-Field. The proposed Markov-Random-Field approach is exploited for estimating the layers' characteristics. Then, a linear predictor of the turbulent phase, based on the computed information on the turbulence layers, is constructed. Since scalability and low computational complexity of the control algorithms are important requirements for real AO systems, the computational complexity properties of the proposed model are investigated. Interestingly, the proposed model shows a good scalability and an almost linear computational complexity thanks to its block diagonal structure. Performances of the proposed method are investigated by means of some simulations.

Adaptive optics (AO) systems of modern telescopes use laser guide stars, produced by resonant excitation of sodium atoms in the mesosphere at around 92 km. Wavefront sensor subapertures, if sufficiently far away from the primary mirror center, resolve the internal structure of the sodium layer. The variability of this structure is caused by the influence of gravity waves and wind shear turbulence. The relevance of such dynamics to AO has been investigated over the past four years. A high-resolution lidar system, employed at the 6-m liquid mirror telescope, which is located near Vancouver, Canada, has been used to study mesospheric dynamics, such as the temporal behavior of the mean altitude. The main results from this study have been published elsewhere and will be summarized here. Along with the temporal variability, the mean altitude on horizontal scales of order IOs of meters has been studied by introducing a tip/tilt stage in the experimental setup. This enables us to swap the laser pulse within a 1 arcmin field of view. The horizontal mean altitude structure function has been measured on 10 observing nights between July and August 2011. Results reveal severe structural differences and a strong horizontal anisotropy. Individual laser beacons in a laser guide star asterism will therefore have at the same time significantly different focus heights. By propagating this 2d structure function to the entrance pupil of a 39 m telescope, we derive a differential focus wavefront error map.

A lunar scintillometer, LuSci, is an inexpensive and robust instrument which deploys a linear array of photodiodes pointed toward the moon to measure scintillation produced by atmospheric turbulence. Covariances between the signals from the photodiodes are analyzed to derive estimates of the turbulence profile within a few hundred meters above the ground. Instrument parameters and phase of the moon are taken into account. This method has been used for site testing and monitoring. We present the development of a new LuSci instrument used to validate the ground-layer turbulence distribution measured from the laser wavefront sensor signals of the Ground Layer Adaptive Optics system at the MMT. The near-simultaneous measurements are used to characterize the performance of the GLAO system. We describe the instrument, its operation, approaches to data reduction, and use in performance characterization of a GLAO system.­

The problem of the wind prole restoration from Multi-Aperture Scintillation Sensor1 (MASS) scintillation indices was studied. We show that we are able to obtain wind proles on the standard MASS altitude grid with reasonable accuracy and altitudinal resolution. Online data processing is also available. Existing MASS data archives can be reprocessed using method of short exposure time.

We present in this paper an analysis of several tip-tilt on-sky data registered on adaptive optics systems installed on different telescopes (Gemini South, William Herschel Telescope, Large Binocular Telescope, Very Large Tele­ scope, Subaru). Vibration peaks can be detected, and it is shown that their presence and location may vary, and that their origin is not always easy to determine. Mechanical solution that have been realized to mitigate vibrations are presented. Nevertheless, residual vibrations may still affect the instruments' performance, ranging from narrow high frequency vibration peaks to wide low frequency windshake-type perturbations. Power Spectral Densities (PSDs) of on-sky data are presented to evidence these features. When possible, indications are given regarding the gain in performance that could be achieved with adequate controllers accounting for vibration mitigation. Two examples of controller identification and design illustrate their ability to compensate for various types of disturbances (turbulence, windshake, vibration peaks, ...),showing a significant gain in performance.

Advanced wide-field AO systems, such as Multi-Conjugate AO (MCAO) systems often require many static optical elements (mirror and lenses) in addition to the active ones (deformable mirrors). These static elements induce additional wave-front errors due to random fabrication errors such as polishing errors. For ELT-size AO systems, these optical elements can be very large, and thus their cost and availability critically depends on how of much fabrication error can be tolerated. Therefore, a rigorous tolerance analysis is absolutely critical. Requirements can, in principle be relaxed, on account that fabrication errors with spatial scales larger than the inter-actuator spacing of the deformable mirrors (DMs) can be corrected. However, this process is significantly complicated by the fact that these optical elements are often conjugated far away from the DMs, and therefore DM correction cannot be achieved over a wide field of view (FOV). In this paper, we present our tolerance analysis in the context of NFIRAOS, the first-light MCAO system for the Thirty Meter Telescope. We start from two top-level error budgets: the “on-axis” error budget, which specifies the acceptable residual wave-front error in the narrow 17”x17” science FOV; and the “off-axis” error budget, which specifies the acceptable residual wave-front error at the edge of the 2’ diameter technical FOV. The former directly relates to science image quality, whereas the latter directly relates to sky coverage. For different assumptions on the spatial power spectrum of the polishing errors, we derive the requirements on each optical element in NFIRAOS using a Monte-Carlo analysis of the predicted off-axis performance of the system with on axis AO correction.

The Subaru adaptive optics system (AO188) is a 188-element curvature sensor adaptive optics system that is operated in both natural and laser guide star modes. AO188 is installed at Nasmyth platform of the 8m Subaru telescope as a facility AO system. The laser guide star mode for AO188 has been commissioned and offered for use in science operation since 2011. The performance of AO188 in the laser guide star mode has been well verified from on-sky data obtained with the infrared camera and spectrograph (IRCS). In this paper, we describe the operation procedure and observing efficiency for the laser guide star mode. We also show the result of the on-sky performance evaluation of AO188 in the laser guide star mode and the characterization of the laser guide star, together with the obtained science results.

Ground-layer adaptive optics (GLAO) has the potential to dramatically increase the efficiency and capabilities of existing ground-based telescopes over a broad range of astronomical science. Recent studies of the optical turbulence above several astronomical sites (e.g. Mauna Kea, Paranal, and Antarctica) show that GLAO can be extended to fields of view of several tens of arcminutes in diameter, larger than previously thought, with angular resolutions close to the freeatmosphere seeing. This is a pivotal result since GLAO science cases benefit from the largest possible corrected fields of view. The corrected areal field of a GLAO system is potentially 2-3 orders of magnitude larger than has been demonstrated to date. The 'Imaka team is working toward an instrument that takes advantage of the one-degree field afforded by Mauna Kea. In this paper we summarize the design/simulation work to date along with our plan to develop an instrument that reaches for this wide field of view.

The Giant Magellan Telescope adaptive optics system will be an integral part of the telescope, providing laser guide star generation, wavefront sensing, and wavefront correction to most of the currently envisioned instruments. The system will provide three observing modes: Natural Guidestar AO (NGSAO), Laser Tomography AO (LTAO), and Ground Layer AO (GLAO). Every AO observing mode will use the telescope’s segmented adaptive secondary mirror to deliver a corrected beam directly to the instruments. High-order wavefront sensing for the NGSAO and LTAO modes is provided by a set of wavefront sensors replicated for each instrument and fed by visible light reflected off the cryostat window. An infrared natural guidestar wavefront sensor with open-loop AO correction is also required to sense tip-tilt, focus, segment piston, and dynamic calibration errors in the LTAO mode. GLAO mode wavefront sensing is provided by laser guidestars over a ~5 arcminute field of view, and natural guidestars over wider fields. A laser guidestar facility will project 120 W of 589 nm laser light in 6 beacons from the periphery of the primary mirror. An off-axis phasing camera and primary and secondary mirror metrology systems will ensure that the telescope optics remain phased. We describe the system requirements, overall architecture, and innovative solutions found to the challenges presented by high-order AO on a segmented extremely large telescope. Further details may be found in specific papers on each of the observing modes and major subsystems.

We provide an update on the development of the first light adaptive optics systems for the Thirty Meter Telescope (TMT) over the past two years. The first light AO facility for TMT consists of the Narrow Field Infra-Red AO System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). This order 60 × 60 laser guide star (LGS) multi-conjugate AO (MCAO) architecture will provide uniform, diffraction-limited performance in the J, H, and K bands over 17-30 arc sec diameter fields with 50 per cent sky coverage at the galactic pole, as is required to support TMT science cases. Both NFIRAOS and the LGSF have successfully completed design reviews during the last twelve months. We also report on recent progress in AO component prototyping, control algorithm development, and system performance analysis.

Adaptive optics systems based on sodium Laser Guide Stars may exploit Natural Guide Stars to solve intrinsic limitations of artificial beacons, such as tilt indetermination and, in the case of Multi-Conjugate Adaptive Optics, tilt anisoplanatism. Natural Guide Stars are also required to mitigate the impact of the sodium layer structure and variability: on a 40-meter class telescope, as a consequence of the perspective elongation effect and of the finite Laser Guide Star Wavefront Sensor field of view, spurious wavefront aberrations are generated. The sodium layer may also have transverse structures leading to significant differential effects among Laser Guide Stars. All these issues show up in MAORY, a concept of a Multi-Conjugate Adaptive Optics module for the European Extremely Large Telescope. Starting from the analysis of the input perturbations to be measured, we derive preliminary requirements for the Natural Guide Star Wavefront Sensor and describe its conceptual design. The Wavefront Sensor uses three natural stars; each wavefront sensor probe consists of a fast tip-tilt and focus channel and a slow channel for monitoring the aberrations induced by the sodium layer. The dual-channel design allows the efficient exploitation of the few natural stars typically available in the field of view, while providing a way to monitor the potential anisoplanatism due to the differential sodium effects among the LGSs.

The paper presents the preliminary design of theNat ural Guide Star Wavefront Sensor for the single conjugate AO system of the GMT telescope. The NGS Wavefront Sensor (NGWS), already identified as a pyramid sensor, will be in charge of the entire wavefront error measurement namely atmospheric turbulence and telescope aberrations, including the segment differential piston error. The paper describes the WFS opto-mechanical design with particular emphasis on the WFS board. Numerical simulations of the GMT NGS AO system are performed taking into account the main characteristics of the considered WFS unit. The simulations take into account correction of the atmospheric perturbation and control of the differential pistons of the GMT segments.

NFIRAOS is the first-light adaptive optics system planned for the Thirty Meter Telescope, and is being designed at the National Research Council of Canada's Herzberg Institute of Astrophysics. NFIRAOS is a laser guide star multiconjugate adaptive optics system - a practical approach to providing diffraction limited image quality in the NIR over a 30" field of view, with high sky coverage. This will enable a wide range of TMT science that depends upon the large corrected field of view and high precision astrometry and photometry. We review recent progress developing the design and conducting performance estimates for NFIRAOS.

Laser Tomographic systems, such as ATLAS, will rely on natural guide stars to sense low order aberrations. LIFT is a novel focal plane wavefront sensor (WFS), performing a maximum likelihood phase retrieval on a single image, with better sensitivity than a 2x2 Hartmann-Shack WFS. We first present a characterization of LIFT’s noise propagation performance and working domain by means of simulations. We then show the results of experiments on ONERA’s test bench for LIFT. These experiments validate the estimation of tip/tilt and focus, in monochromatic light and in large bandwidth (for a spectral resolution of 3), as well as the expected noise propagation. They also confirm the validity of the imaging models used for simulations. Finally, we focus on the preparation of an on-sky validation based on Gemini Multi-conjugate adaptive optics System (GeMS) calibration data at Gemini Southern Observatory.

With two to three deformable mirrors, three Natural Guide Stars (NGS) and five sodium Laser Guide Stars (LGS), the Gemini Multi-Conjugate Adaptive Optics System (Gemini MCAO a.k.a. GeMS) will be the first facility-class MCAO capability to be offered for regular science observations starting in 2013A. The engineering and science commissioning phase of the project was kicked off in January 2011 when the Gemini South Laser Guide Star Facility (GS LGSF) propagated its 50W laser above the summit of Cerro Pachón, Chile. GeMS commissioning has proceeded throughout 2011 and the first half of 2012 at a pace of one 6- to 10-night run per month with a 5-month pause during the 2011 Chilean winter. This paper focuses on the LGSF-side of the project and provides an overview of the LGSF system and subsystems, their top-level specifications, design, integration with the telescope, and performance throughout commissioning and beyond. Subsystems of the GS LGSF include: (i) a diode-pumped solid-state 1.06+1.32 micron sum-frequency laser capable of producing over 50W of output power at the sodium wavelength (589nm); (ii) Beam Transfer Optics (BTO) that transport the 50W beam up the telescope, split the beam five-ways and configure the five 10W beams for projection by the Laser Launch Telescope (LLT) located behind the Gemini South 8m telescope secondary mirror; and (iii) a variety of safety systems to ensure safe laser operations for observatory personnel and equipment, neighbor observatories, as well as passing aircrafts and satellites.

A microsecond pulsed sodium has been developed in TIPC laser physics research center, the power of this laser is around 20W and the length of the pulse is about 120 microseconds. In 2011, an experiment to project the TIPC prototype laser to the sky and measure the photon returns of the laser has been held on the 1.8 meter telescope in Yunnan observation site. During the sky test, an artificial sodium beacon has been successfully generated, and the brightness of the sodium beacon is around 8.7M in V Band. In the 2012 test campaign, the sodium column density facility has mounted on the telescope to test the local sodium density and structure and the sodium density test result is around 2.2x10¹³/m².

Laser-guide-star-based multi-conjugate adaptive optics (MCAO) systems require natural guide-stars to measure tilt and tilt-anisoplanatism modes. This paper focuses on the parameter optimisation of sub-optimal integrator-based controllers using a single and a double integrator (baseline option) to drive the low-order loop of NFIRAOS, the 1st light MCAO system for the Thirty-Meter Telescope. The minimum-variance (MV) controller is outlined, against which integrators are compared. Simulations using ~500 asterisms considered in sky-coverage simulations for the TMT show that the double integrator gives competitive results thoughout the range of asterisms and magnitudes considered. It is shown that using an optimal modal gain integrator can further improve the performance with respect to using an averaged gain for all of part of the modes. However, it is outperformed by the MV controller, in particular for asterisms with relatively dim stars (lower bound is magnitude 22 in H-band) requiring low temporal frame-rates (as low as 16Hz) to integrate more flux. Over all the cases tested, an average of ~100 nm rms (23 nm rms median) improvement can be achieved with the MV. The MV further increases by 15% the probability of working below the 50th-percentile residual of the double integrator.

Optimal control laws for new Adaptive Optics (AO) concepts in astronomy require the implementation of techniques intended for real time identification of the atmospheric turbulence. Contrary to the Optimized Modal Gain Integrator (OMGI), it has been proved that the Kalman Filter (KF) based optimal control law enables estimation and prediction of the turbulent phase from the measurements and corrects efficiently the different modes of this phase in the case of a wide field tomographic AO system. But using such kind of processes, for any Extremely Large Telescope (ELT), will be extremely difficult because of the numerical complexity of the computations involved in the matrices calculations as well as the recording of large covariance matrices. A new control law is proposed, based on the Ensemble Transform Kalman Filter (ETKF) and its efficient variation, Local ETKF (recently developed for geophysics applications), allowing to dramatically reduce the computation burden for an ELT implementation and also to deal with non stationary behaviors of the turbulence.

We explore the extension of predictive control techniques to multi-guide star, multi-layer tomographic wavefront measurement systems using a shift-and-average correction scheme that incorporates wind velocity and direction. In addition to reducing temporal error budget terms, there are potentially additional benefits for tomographic AO systems; the combination of wind velocity information and phase height information from multiple guide stars breaks inherent degeneracies in volumetric tomographic reconstruction, producing a reduction in the geometric tomographic error. In a tomographic simulation of an 8-meter telescope with 3 laser guide stars over 2 arcminute diameter, we find that tracking organized wind motion as it flows into metapupil regions sampled by only one guide star improves layer estimates beyond the guide star radius, allowing for an expansion of the field of view. For this case, we demonstrate improvement of layer phase estimates of 3% to 12%, translating into potential gains in the MOAO field of regard area of up to 40%. The majority of the benefits occur in regions of the metapupil sampled by only 1-2 LGS's downwind at high altitudes.

Wide Field Adaptive Optics (WFAO) concepts, such as Ground Layer AO (GLAO), Laser Tomography AO (LTAO) or Multi-Conjugate AO (MCAO) are currently under study in the perspective of future ELT instruments. In that context, the experimental validation of the various smart control solutions proposed by several teams in the past years is now essential. In this paper we present experimental validation and comparison of different control laws for LTAO concept from the simplest least-square to the optimal Linear Quadratic Gaussian solutions including Virtual DeformableMirror and Pseudo-closed loop approaches. This study is performed using the Onera WFAO facility (HOMER bench). The four control laws are tested and compared in terms of performance and robustness. In particular, low and high noise conditions are explored, for several different fields of views. We also highlight their experimental optimization by the tuning of parameters in control laws.

ELTs will offer angular resolution around 10mas in the near-IR and unprecedented sensitivity. While direct imaging of Earth-like exoplanets around Sun-like stars will stay out of reach of ELTs, we show that habitable planets around nearby M-type main sequence stars can be directly imaged. For about 300 nearby M dwarfs, the angular separation at maximum elongation is at or beyond 1 ë/D in the near-IR for an ELT. The planet to star contrast is 1e-7 to 1e-8, similar to what the upcoming generation of Extreme-AO systems will achieve on 8-m telescopes, and the potential planets are sufficiently bright for near-IR spectroscopy. We show that the technological solutions required to achieve this goal exist. For example, the PIAACMC coronagraph can deliver full starlight rejection, 100% throughput and sub-ë/D IWA for the EELT, GMT and TMT pupils. A closely related coronagraph is part of SCExAO on Subaru. We conclude that large ground-based telescopes will acquire the first high quality spectra of habitable planets orbiting M-type stars, while future space mission(s) will later target F-G-K type stars.

In 2009 our group started the integration of the SCExAO project, a highly flexible, open platform for high contrast imaging at the highest angular resolution, inserted between the coronagraphic imaging camera HiCIAO and the 188-actuator AO system of Subaru. In its first version, SCExAO combines a MEMS-based wavefront control system feeding a high performance PIAA-based coronagraph. This paper presents some of the images obtained during the first engineering observations conducted with SCExAO in 2011: diffraction limited imaging in the visible as well as PIAA coronagraphy in the near infrared; along with the wavefront control strategies to be tested on sky during the next round of SCExAO observations, scheduled in the Fall 2012.

Direct detection and spectral characterization of extra-solar planets is one of the most exciting and challenging areas in modern astronomy due to the very large contrast between the host star and the planet at very small angular separations. SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research in Europe) is a second-generation instrument for the ESO VLT dedicated to this scientific objective. It combines an extreme adaptive optics system, various coronagraphic devices and a suite of focal instruments providing imaging, integral field spectroscopy and polarimetry capabilities in the visible and near-infrared spectral ranges. The extreme Adaptive Optics (AO) system, SAXO, is the heart of the SPHERE system, providing to the scientific instruments a flat wavefront corrected from all the atmospheric turbulence and internal defects. We present an updated analysis of SAXO assembly, integration and performance. This integration has been defined in a two step process. While first step is now over and second one is ongoing, we propose a global overview of integration results. The main requirements and system characteristics are briefly recalled, then each sub system is presented and characterized. Finally the full AO loop first performance is assessed. First results demonstrate that SAXO shall meet its challenging requirements.

Project 1640, a high-contrast spectral-imaging effort involving a coordinated set of instrumentation and software, built at AMNH, JPL, Cambridge and Caltech, has been commissioned and is fully operational. This novel suite of instrumentation includes a 3388+241-actuator adaptive optics system, an optimized apodized pupil Lyot coronagraph, an integral field spectrograph, and an interferometric calibration wave front sensor. Project 1640 is the first of its kind of instrumentation, designed to image and characterize planetary systems around nearby stars, employing a variety of techniques to break the speckle-noise barrier. It is operational roughly one year before any similar project, with the goal of reaching a contrast of 10^-7 at 1 arcsecond separation. We describe the instrument, highlight recent results, and document on-sky performance at the start of a 3-year, 99-night survey at the Palomar 5-m Hale telescope.

We present a promising approach to the extremely fast sensing and correction of small wavefront errors in adaptive optics systems. As our algorithm's computational complexity is roughly proportional to the number of actuators, it is particularly suitable to systems with 10,000 to 100,000 actuators. Our approach is based on sequential phase diversity and simple relations between the point-spread function and the wavefront error in the case of small aberrations. The particular choice of phase diversity, introduced by the deformable mirror itself, minimizes the wavefront error as well as the computational complexity. The method is well suited for high­ contrast astronomical imaging of point sources such as the direct detection and characterization of exoplanets around stars, and it works even in the presence of a coronagraph that suppresses the diffraction pattern. The accompanying paper in these proceedings by Korkiakoski et al. describes the performance of the algorithm using numerical simulations and laboratory tests.

The direct imaging of planets around nearby stars is exceedingly difficult. Only about 14 exoplanets have been imaged to date that have masses less than 13 times that of Jupiter. The next generation of planet-finding coronagraphs, including VLT-SPHERE, the Gemini Planet Imager, Palomar P1640, and Subaru HiCIAO have predicted contrast performance of roughly a thousand times less than would be needed to detect Earth-like planets. In this paper we review the state of the art in exoplanet imaging, most notably the method of Locally Optimized Combination of Images (LOCI), and we investigate the potential of improving the detectability of faint exoplanets through the use of advanced statistical methods based on the concepts of the ideal observer and the Hotelling observer. We propose a formal comparison of techniques using a blind data challenge with an evaluation of performance using the Receiver Operating Characteristic (ROC) and Localization ROC (LROC) curves. We place particular emphasis on the understanding and modeling of realistic sources of measurement noise in ground-based AO-corrected coronagraphs. The work reported in this paper is the result of interactions between the co-authors during a week-long workshop on exoplanet imaging that was held in Squaw Valley, California, in March of 2012.

The adaptive optics (AO) simulations at the Thirty Meter Telescope (TMT) have been carried out using the efficient, C based multi-threaded adaptive optics simulator (MAOS, http://github.com/lianqiw/maos). By porting time-critical parts of MAOS to graphical processing units (GPU) using NVIDIA CUDA technology, we achieved a 10 fold speed up for each GTX 580 GPU used compared to a modern quad core CPU. Each time step of full scale end to end simulation for the TMT narrow field infrared AO system (NFIRAOS) takes only 0.11 second in a desktop with two GTX 580s. We also demonstrate that the TMT minimum variance reconstructor can be assembled in matrix vector multiply (MVM) format in 8 seconds with 8 GTX 580 GPUs, meeting the TMT requirement for updating the reconstructor. Analysis show that it is also possible to apply the MVM using 8 GTX 580s within the required latency.

Anisoplanatism is a primary source of photometric and astrometric error in single-conjugate adaptive optics. We present initial results of a project to model the off-axis optical transfer function in the adaptive optics system at the Keck II telescope. The model currently accounts for the effects of atmospheric anisoplanatism in natural guide star observations. The model for the atmospheric contribution to the anisoplanatic transfer function uses contemporaneous MASS/ DIMM measurements. Here we present the results of a validation campaign using observations of naturally guided visual binary stars under varying conditions, parameterized by the r₀ and θ₀ parameters of the C²_n atmospheric turbulence profile. We are working to construct a model of the instrumental field-dependent aberrations in the NIRC2 camera using an artificial source in the Nasmyth focal plane. We also discuss our plans to extend the work to laser guide star operation.

It is a widely accepted conjecture that the width of the incoherent halo in an adaptive optics point-spread function (PSF) should decrease with the level of correction. Using end-to-end simulations we prove that this is not the case and the halo is actually increasing in width, albeit at a decreasing overall brightness level as must be the case with increasing correction. The simulations span the cases of: seeing-limited, partial-, and high-order adaptive-optics (AO) correction. We show the relationship between the theory of partially-developed speckle and the observed statistical behavior of on-axis PSF intensity. Finally, we check the results of the simulations with real data obtained using the 3.5m Starfire Optical Range telescope located in New Mexico, US.

The thirty meter telescope (TMT) has the potential to find new planetary systems and to study them in greater details. It could also possibly image super-Earth planets around the closest stars or still accreting distant protoplanets around stars in very young star forming regions. Since no first generation dedicated exoplanet finding instrument has been selected for the TMT, initial direct exoplanet imaging will have to rely on the NFIRAOS facility adaptive optics (AO) system and IRIS spectro-imaging near-infrared (NIR) camera. End­ to-end Fresnel NFIRAOS simulations are presented using their current optical designs to evaluate the system multi-wavelength high-contrast imaging capabilities. Long exposures have been simulated using the expected AO-corrected phase screens and the estimated speckle lifetime. It is shown that NFIRAOS/IRIS may achieve contrasts close to the Gemini planet imager (GPI, an optimized NIR planet-finding instrument that will soon be installed on the Gemini South 8-m telescope), but needs to rely on multi-wavelength processing (by a factor 50) to achieve that goal, a challenging requirement. Without a coronograph and a better treatment of the in-band static speckle noise, it is unlikely that NFIRAOS/ IRIS will be able to achieve GPI-like contrasts at very small inner working angles, which is potentially accessible with a large 30-meter telescope. However, TMT, with its bigger aperture and better angular resolution, along with the current NFIRAOS/ IRIS designs, should be able to acquire higher SNR spectra and achieve three times better astrometric accuracy than GPI for medium to bright planets, resulting in better atmospheric characterization and faster orbital parameter determination of a sample of GPI planets.

Sparse Aperture-Mask Interferometry (SAM or NRM) behind Adaptive Optics (AO) has now come of age, with more than a dozen astronomy papers published from several 5-10m class telescopes around the world. I will describe the reasons behind its success in achieving relatively high contrasts ( 1000:1 at lambda/ D) and repeatable binary astronomy at the diffraction limit, even when used behind laser-guide star adaptive optics. Placed within the context of AO calibration, the information in an image can be split into pupil-plane phase, Fourier amplitude and closure-phase. It is the closure-phase observable, or its generalisation to Kernel phase, that is immune to pupil-plane phase errors at first and second-order and has been the reason for the technique's success. I will outline the limitations of the technique and the prospects for aperture-masking and related techniques in the future.

We discuss in this paper the last results of our adaptive optics point spread function reconstruction (PSF-R) project at theW. M. Keck Observatory. Objective of the project are recalled, followed by a short reintroduction of the basis of the method. Amongst the novelties, a method for a drastic reduction of the number of the so-called U_i,j functions for any pupil shape and an arbitrary number of actuators is presented, making the current PSF-R technique easily applicable to extremely large telescopes AO systems. Our success at reconstructing the PSF in bright natural guide star (NGS) conditions is revisited in details and confirmed. First results on PSF-R with faint NGS are presented and it is shown that our reconstructed PSF Strehl ratio drops with the NGS magnitude basically like the measured sky performance. These preliminary but encouraging results, in real conditions, can be considered as a validation of our PSF-R approach. Plans for the next steps of the project are discussed at the end of this progress report.

In adaptive optics systems employing laser guide stars, the tip/tilt contribution to the long exposure point spread function must be estimated separately from the high-order tip/tilt removed point spread function because this component is estimated separately from a single or multiple low-order natural guide star wavefront sensors. This paper investigates this problem for laser guide star multi conjugate adaptive optics. The approach is based on the scheme developed by Flicker in 2003 [1], and consists in post-processing the measurement covariance matrix of multiple low-order natural guide star wavefront sensors controlling tip/tilt and tilt anisoplanatism. An innovative simulation model based "balanced" algorithm is introduced to capture error terms not accounted for in Flicker's algorithm. Sample enclosed energy results for the Thirty Meter Telescope multi conjugate adaptive optics system demonstrate the superiority of the balanced method and call for further analytical work and experimental validation.

The identification of spatial covariance matrices is required in adaptive optics in order to perform tomographic reconstruction with optimal estimators. We use on-sky measurements from Canary, the on-sky demonstrator of MOAO for EAGLE, to study the statistical convergence of the spatial covariance of Shack-Hartmann measurements. We describe a new, faster, analytical approximated model for this spatial covariance, and finally bring into light a new procedure for model identification, reducing the tomographic error. We quantify the gain brought by the new approach on both numerical simulations and on-sky data.

The AO system calibration is usually done with a dedicated setup during daytime. Here we present results of two alternative techniques as the synthetic and the on-sky interaction matrix calibration. In both cases we created matrices controlling 400 modes of the LBT-FLAO system. We present here the performances reached on-sky at LBT compared with those obtained with the standard calibration. The described techniques allow calibrating the AO system without any dedicated hardware. This is particularly attractive for systems that require complex calibration setup such as those with a convex adaptive secondary like the MMT and the planned VLT AOF.

The adaptive optics (AO) on the European Extremely Large Telescope, as well as earlier pathfinders like the Adaptive Optics Facility, at the Very Large Telescope in 2014, will no longer be stationary systems. AO is no longer isolated on a bench; some elements are directly in the optical train of the telescope, suffering environment and constrains changes during the observations. To guarantee good performance at any observing time, we investigate a self-calibration strategy. We focus here on one of the most challenging aspects: the identification of system parameters during closed-loop observations without introducing any additional disturbance. Such problem is known in the identification theory to be difficult to solve. We have recently presented (Béchet et al., AO4ELT2 Conference, 2011) an identification method for this, with promising results obtained in simulations. To consolidate these advances, we come back in the present paper to the equations and provide a theoretical analysis to justify the choice of the algorithm. We highlight the benefit of using incremental data and commands to decorrelate the disturbance. We also present 2 implementations of the method, currently studied at the European Southern Observatory.

The AOF project will transform one of the VLT UT into an adaptive telescope. This configuration presents new challenges but also provides new opportunities for the integration of the Adaptive Optics in the global telescope control scheme and performance improvement. In particular the Interaction Matrix between the Deformable Mirror and Wavefront Sensor of the system cannot be measured on an artificial source, as there is no intermediate focal plane ahead of the Deformable Mirror. The baseline for the AOF is to use a Pseudo-Pynthetic IM, i.e. computer-generated but finetuned thanks to measured parameters of the system: Influence Functions, WFS characteristics, mis-alignments. This paper presents the control strategy of the AOF, the simulation code that will be used to generate the PSIM for the AOF, and the ideas for updating the Control Matrix depending on the estimation of the DM/WFS mis-registration.

Adaptive Optics Real-Time Control systems for next generation ground-based telescopes demand significantly higher processing power, memory bandwidth and I/O capacity on the hardware platform than those for existing control systems. We present a FPGA based high-performance computing platform that is developed at Dominion Radio Astrophysical Observatory and is very suitable for the applications of Adaptive Optics Real-Time Control systems. With maximum of 16 computing blades, 110 TeraMAC/s processing power, 1.8Terabyte/s memory bandwidth and 19.5 Terabit/s I/O capacity, this ATCA architecture platform has enough capacity to perform pixel processing, tomographic wave-front reconstruction and deformable mirror fitting for first and second generation AO systems on 30+-meter class telescopes. As an example, we demonstrate that with only one computing blade, the platform can handle the real time tomography needs of NFIRAOS, the Thirty-Meter Telescope first light facility Multi-Conjugate Adaptive Optics system. The High- Performance FPGA platform is integrated with Board Software Development Kit to provide a complete and fully tested set of interfaces to access the hardware resources. Therefore the firmware development can be focused on unique, userspecific applications.

This paper reflects, from a computational perspective, on the experience gathered in designing and implementing realtime control of the PALM-3000 adaptive optics system currently in operation at the Palomar Observatory. We review the algorithms that serve as functional requirements driving the architecture developed, and describe key design issues and solutions that contributed to the system’s low compute-latency. Additionally, we describe an implementation of dense matrix-vector-multiplication for wavefront reconstruction that exceeds 95% of the maximum achievable bandwidth on NVIDIA GeForce 8800GTX GPU.

The VLT Deformable secondary is planned to be installed on the VLT UT#4 as part of the telescope conversion into the Adaptive Optics test Facility (AOF). The adaptive unit is based on the well proven contactless, voice coil motor technology that has been already successfully implemented in the MMT, LBT and Magellan adaptive secondaries, and is considered a promising technical choice for the forthcoming ELT-generation adaptive correctors, like the E-ELT M4 and the GMT ASM. The VLT adaptive unit has been recently assembled after the completion of the manufacturing and modular test phases. In this paper, we present the most relevant aspects of the system integration and report the preliminary results of the electromechanical tests performed on the unit. This test campaign is a typical major step foreseen in all similar systems built so far: thanks to the metrology embedded in the system, that allows generating time-dependent stimuli and recording in real time the position of the controlled mirror on all actuators, typical dynamic response quality parameters like modal settling time, overshoot and following error can be acquired without employing optical measurements. In this way the system dynamic and some aspect of its thermal and long term stability can be fully characterized before starting the optical tests and calibrations.

Glassy thin shells are key components for the development of adaptive optics and are part of future and innovative projects such as ELT. However, manufacturing thin shells is a real challenge. Even though optical requirements for the front face - or optical face - are relaxed compared to conventional passive mirrors, requirements concerning thickness uniformity are difficult to achieve. In addition, process has to be completely re-defined as thin mirror generates new manufacturing issues. In particular, scratches and digs requirement is more difficult as this could weaken the shell, handling is also an important issue due to the fragility of the mirror. Sagem, through REOSC program, has recently manufactured different types of thin shells in the frame of European projects - E-ELT M4 prototypes and VLT Deformable Secondary Mirror (VLT DSM).

In ELTs the larger size of the aperture will translates into different categories of problems and different kind of solutions. The concept of Global Multi Conjugated Adaptive Optics is here introduced. In this, the wavefront sensing is extended to a much larger Field of View, practically limited by the telescope optics or optomechanics and by the limit given by the coverage of the metapupil at the highest altitude of interest. The correction of these layers is employed in a numerical fashion and the information is retrieved in order to compensate for a much limited Field of View. All this, being done in a layer oriented fashion, does allow for a simplified treatment of the Signal to Noise Ratio and to an estimate of the performances in the plot h vs. spatial scales where layers and the related Kolmogorov distributed turbulence are plotted. Once this information is retrieved it is fed back into the existing Deformable Mirror with a back-projection that allow for the most efficient way in terms of coverage of the spatial frequencies. The nature of the closed- vs open-loop of such an approach is also briefly discussed. The aim of a sky coverage and of performances getting closer or exceeding the ones provided by Laser Guide Stars can be at hands.

We present a wavefront sensor design for the purpose of measuring post-AO corrected light, especially in the cases of high-Strehl and when using natural guide stars. It is inspired by holographic design principles and oers approximately two orders of magnitude increase in sensitivity over a conventional Shack-Hartmann design. The theoretical design and that of a laboratory prototype are presented, together with simulation results for a case-study of sinusoidal phase and the corresponding results from a laboratory experiment.

A phase-shifting Zernike wavefront sensor has distinct advantages over other types of wavefront sensors. Chief among them are: 1) improved sensitivity to low-order aberrations and 2) efficient use of photons (hence reduced sensitivity to photon noise). We are in the process of deploying a phase-shifting Zernike wavefront sensor to be used with the real-time adaptive optics system for Palomar. Here we present the current state of the Zernike wavefront sensor to be integrated into the high-order adaptive optics system at Mount Palomar’s Hale Telescope.

We have constructed an adaptive optics system incorporating a holographic wavefront sensor with the autonomous closed-loop control of a MEMS deformable mirror (DM). HALOS incorporates a multiplexed holographic recording of the response functions of each actuator in a deformable mirror. On reconstruction with an arbitrary input beam, pairs of focal spots are produced. By measuring the relative intensities of these spots a full measurement of the absolute phase can be constructed. Using fast photodiodes, direct feedback correction can be applied to the actuators.

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.

The four meter Advanced Technology Solar Telescope (ATST) adaptive optics (AO) system will require at least twenty-four times the real time processing power as the Dunn Solar Telescope AO system. An FPGA solution for ATST AO real time processing is being pursued instead of the parallel DSP approach used for the Dunn AO76 system. An analysis shows FPGAs will have lower latency and lower hardware cost than an equivalent DSP solution. Interfacing to the proposed high speed camera and the deformable mirror will be simpler and have lower latency than with DSPs. This paper will discuss the current design and progress toward implementing the FPGA solution.

Robo-AO is the first astronomical laser guide star adaptive optics (AO) system designed to operate completely independent of human supervision. A single computer commands the AO system, the laser guide star, visible and near-infrared science cameras (which double as tip-tip sensors), the telescope, and other instrument functions. Autonomous startup and shutdown sequences as well as concatenated visible observations were demonstrated in late 2011. The fully robotic software is currently operating during a month long demonstration of Robo- AO at the Palomar Observatory 60-inch telescope.

We report recent development in real-time control system of 188-element Laser Guide Star Adaptive Optics for Subaru Telescope (Subaru LGSAO-188). The current status is reported, and plans for improvements to enhance the performance are reported as well. A major item is to invoke the optimum gain control, which is being implemented on the data handling system and to be attached to the real time control system. We also explain about other new features on the control system including general response acquisition system as an expansion of response matrix acquisition system.

SPARTA, the ESO Standard Platform for Adaptive optics Real Time Applications, is the high-performance, real-time computing platform serving three major 2nd generation instruments at the VLT (SPHERE, GALACSI and GRAAL) and possibly a fourth one (ERIS). SPARTA offers a very modular and fine-grained architecture, which is generic enough to serve a variety of AO systems. It includes the definitions of all the interfaces between those modules and provides libraries and tools for their implementation and testing, as well as a mapping to technologies capable of delivering the required performance. These comprise, amongst others, VXS communication, FPGA-aided wavefront processing, command time filtering and I/O, DSP-based wavefront reconstruction, DDS data distribution and multi-CPU number crunching, most of them innovative with respect to ESO standards in use. A scaled-down version of the platform, namely SPARTA-Light, will employ a subset of the SPARTA technologies to implement the AO modules for the VLT auxiliary telescopes (NAOMI) and is the baseline for a new VLTI instrument (GRAVITY). For the above instrument portfolio, SPARTA provides also a complete implementation of the AO application, with features customised to each instrument's needs and specific algorithms. In this paper we describe the architecture of SPARTA, its technology choices, functional units and test tools. End-to-end as well as individual module performance data is provided for the XAO system delivered to SPHERE. Initial performance results are presented for the GALACSI and GRAAL systems under development.

EDIFISE is a technology demonstrator instrument developed at the Institute of Astrophysics of the Canary Islands (IAC), intended to explore the feasibility of combining Adaptive Optics with attenuated optical fibers in order to obtain high spatial resolution spectra at the surroundings of a star, as an alternative to coronagraphy. A simplified version with only tip tilt correction has been tested at the OGS telescope in Observatorio del Teide (Canary islands, Spain) and a complete version is intended to be tested at the OGS and at the WHT telescope in Observatorio del Roque de los Muchachos, (Canary Islands, Spain). This paper describes the FPGA-based real time control of the High Order unit, responsible of the computation of the actuation values of a 97-actuactor deformable mirror (11x11) with the information provided by a configurable wavefront sensor of up to 16x16 subpupils at 500 Hz (128x128 pixels). The reconfigurable logic hardware will allow both zonal and modal control approaches, will full access to select which mode loops should be closed and with a number of utilities for influence matrix and open loop response measurements. The system has been designed in a modular way to allow for easy upgrade to faster frame rates (1500 Hz) and bigger wavefront sensors (240x240 pixels), accepting also several interfaces from the WFS and towards the mirror driver. The FPGA-based (Field Programmable Gate Array) real time controller provides bias and flat-fielding corrections, subpupil slopes to modal matrix computation for up to 97 modes, independent servo loop controllers for each mode with user control for independent loop opening or closing, mode to actuator matrix computation and non-common path aberration correction capability. It also provides full housekeeping control via UPD/IP for matrix reloading and full system data logging.

EAGLE is a proposed multi-IFU instrument for the E-ELT, with a full multi-object AO system. Current baseline designs for this MOAO system include up to six laser guide stars and five natural guide stars. Twenty science channels will be corrected using a corresponding number of independent 84x84 actuator deformable mirrors, though the applied corrections will not be observed by the wavefront sensors. In addition to this, the E-ELT M4 mirror is also part of the AO system, and will operate in closed loop. One possible design for a real-time control system for EAGLE is presented here, based on the Durham AO Real-time Control platform (DARC). Using hardware that we have available, we will present performance results based on the implementation of a sub-set of EAGLE, a single IFU channel. This can then be replicated twenty times to obtain a full EAGLE real-time control system, since each channel is independent. We also consider the implementation of real-time control systems for other ELT instruments, and how far our approach can take us.

The Adaptive Optics System at the Large Binocular Telescope Observatory consists of two Adaptive Secondary (ASM) mirrors and two Pyramid Wavefront sensors. The first ASM/Pyramid pair has been commissioned and is being used for science operation using the NIR camera PISCES on the right side of the binocular telescope. The left side ASM/Pyramid system is currently being commissioned, with completion scheduled for the Fall of 2012. We will discuss the operation of the first Adaptive Optics System at the LBT Observatory including interactions of the AO system with the telescope and its TCS, observational modes, user interfaces, observational scripting language, time requirement for closed loop and offsets and observing efficiency.

The interferometric imager LINC-NIRVANA will use pyramid wavefront-sensors for multi-conjugated adaptive optics (MCAO). A derotator will produce a static field on the pyramids, but a rotating pupil image on the CCD. For long exposure times, we have to take into account this effect to command the deformable mirror properly by changing the command matrix on the fly. We reproduce in a laboratory set-up this configuration to test different methods for compensating for this effect. We present the results obtained and the optimal solution we have selected.

Control software for adaptive optics systems is mostly custom built and very specific in nature. We have developed FOAM, a modular adaptive optics framework for controlling and simulating adaptive optics systems in various environments. Portability is provided both for different control hardware and adaptive optics setups. To achieve this, FOAM is written in C++ and runs on standard CPUs. Furthermore we use standard Unix libraries and compilation procedures and implemented a hardware abstraction layer in FOAM. We have successfully implemented FOAM on the adaptive optics system of ExPo - a high-contrast imaging polarimeter developed at our institute - in the lab and will test it on-sky late June 2012. We also plan to implement FOAM on adaptive optics systems for microscopy and solar adaptive optics. FOAM is available* under the GNU GPL license and is free to be used by anyone.

Many concepts of Wide Field AO (WFAO) systems are under development, especially for Extremely Large Tele­ scopes (ELTs) instruments. Multi-Object Adaptive Optics (MOAO) is one of these WFAO concepts, well suited to high redshifts galaxies observations in very wide Field of View (FoV). The E-ELT instrument EAGLE will use this approach. CANARY, the on-sky pathfinder for MOAO, has obtained the first compensated images on Natural Guide Stars (NGSs) at the William Herschel Telescope in September 2010. We present in this paper numerical and experimental validations of a Linear Quadratic Gaussian (LQG) control. This is an appealing strategy that provides an optimal control in the sense of minimum residual phase variance. It also provides a unified formalism that allows accounting for multi WaveFront Sensors (WFSs) channels, both on Laser Guide Stars (LGSs) and NGSs, and for various disturbance sources (turbulence, vibrations). We show how the specific MOAO CANARY configuration can be embedded in a state-space framework. We present experimental laboratory validations that demonstrate the gain brought by tomographic LQG control for CANARY, together with comparative simulations. Model identification necessary for a robust on-sky operation is discussed.

In the context of adaptive optics (AO), Linear Quadratic Gaussian (LQG) control uses the state-feedback of the atmospheric distortion wavefront estimate. Such estimate is obtained from a Kalman filter which incorporates a model of the atmospheric distortion wavefront. We analyze the performance and the robustness of LQG- based control compared to classic integral control, by the means of end-to-end simulations and by considering different levels of wavefront sensor (WFS) noise.

Diffraction limited resolution adaptive optics (AO) correction in visible wavelengths requires a high performance control. In this paper we investigate infinite impulse response filters that optimize the wavefront correction: we tested these algorithms through full numerical simulations of a single-conjugate AO system comprising an adaptive secondary mirror with 1127 actuators and a pyramid wavefront sensor (WFS). The actual practicability of the algorithms depends on both robustness and knowledge of the real system: errors in the system model may even worsen the performance. In particular we checked the robustness of the algorithms in different conditions, proving that the proposed method can reject both disturbance and calibration errors.

Control system design for adaptive optics is becoming more complex and sophisticated with increasing demands on the compensation of atmospheric turbulence. Contemporary controllers used in adaptive optics systems are optimised in the sense of a cost function (linear quadratic regulators) or to a worst case scenario (robust H_∞ controllers). Prediction, to some extent, can be incorporated into the controllers using the Kalman filter and a model of the atmospheric turbulence. Despite the growing number of publications on adaptive optics control systems, only the unconstrained case is usually considered. Accounting for the physical constraints of the adaptive optics system components, such as limited actuator stroke, still represents a problem. As a possible solution, one can consider constrained receding horizon control (RHC), also known as Model Predictive Control (MPC). The ability of RHC to handle constraints and make predictions of the future control signals makes it attractive for application in astronomical adaptive optics. The main potential difficulty with the application of RHC is its heavy computational load. This paper presents preliminary results on numerical simulations of an adaptive optics system controlled by constrained RHC. In particular, the case of output disturbance rejection is considered. The results of numerical simulations are provided. Finally, methods for improving the computational performance of constrained receding horizon controllers in adaptive optics are also discussed.

A modal control optimization method for adaptive optics on the tempo-spatial domain is presented. The spatial modes of the adaptive optics system can be obtained by the singular value decomposition of the response function matrix of the adaptive optics system. The number of correction modes is determined dynamically by the root mean square estimation of the residual aberration after the correction with different number of modes. A Smith compensator is designed to reduce the time delay effect on the closed-loop system. The modal optimization method is experimentally verified by compensating phase distortion produced by artificial atmospheric turbulence in laboratory. Experimental results show that the correction capability of the adaptive optics system can be greatly improved in comparison to that of the generic modal gain integrator approach with the fixed number of correction modes. The modal control optimization method is an attractive and practical alternative to adaptive optics control.

NFIRAOS Small meteors usually bum up near the bottom of the sodium layer. Meteor trails can lead to temporary dra­ matic changes in the altitude of the sodium layer. This altitude change is very rapid, typically over 1 second, and after some unpredictable period of 10-20 seconds, can transition back to the nominal mean altitude also in about 1 second. The altitude change is very drastic and can jump by up to 1 km which, on the face of it, would cause 4 micrometers defocus errors on LGS WFS measurements for a 30-m telescope, unless properly tracked. Measurements by the UBC Lidar detected 20 meteor trails I hour, and of these, 1-2 are significant events. We report on a full end-to-end Simulink simulation for TMT NFIRAOS including: meteor events measured by the UBC Lidar; on-instrument NGS focus sensor running at 90 Hz (median sky coverage frame rate); optimal temporal blending with LGS WFS focus measurements; LGS WFS centroiding matched filter update and Truth WFS update very 3s; full trombone servo model including non-linear focus range vs stage position. We optimized our control architecture and traded off motor power dissipation versus residual wavefront error and Shack-Hartmann spot displacement and found range tracking errors induce 12 nm WFE in normal conditions and brief (Is) jumps of 30-80 nm WFE at the beginning and ending of meteor transients.

A forecasting algorithm (FORS) based on Auto Regressive Moving Average (ARMA) processes was developed to correctly model stationary processes and was applied in simulations to the problem of improving the efficiency of an adaptive optics (AO) system. We present here a hardware demonstrator developed at the Solar Physics Laboratory of the University of Rome Tor Vergata where this algorithm has been implemented. An AO system has been deployed to test the efficiency of the algorithm, in which controlled aberrations are introduced in the system and the efficiency of the correction is measured. The demonstrator has proved that there is a significant performance gain by using the FORS algorithm.

GALACSI is one of the Adaptive Optics (AO) systems part of the ESO Adaptive Optics Facility (AOF). It will use the VLT 4-Laser Guide Stars system, high speed and low noise WaveFront Sensor cameras (<1e-, 1000Hz) the Deformable Secondary Mirror (DSM) and the SPARTA Real Time Computer to sharpen images and enhance faint object detectability of the MUSE Instrument. MUSE is an Integral Field Spectrograph working at wavelengths from 465nm to 930nm. GALACSI implements 2 different AO modes; in Wide Field Mode (WFM) it will perform Ground Layer AO correction and enhance the collected energy in a 0.2" by 0.2" pixel by a factor 2 at 750nm over a Field of View (FoV) of 1' by 1'. The 4 LGSs and one tip tilt reference star (R-mag <17.5) are located outside the MUSE FoV. Key requirements are to provide this performance and a very good image stability for a 1hour long integration time. In Narrow Field Mode (NFM) Laser Tomography AO will be used to reconstruct and correct the turbulence for the center field using the 4 LGSs at 15" off axis and the Near Infra Red (NIR) light of one reference star on axis for tip tilt and focus sensing. In NFM GALACSI will provide a moderate Strehl Ratio of 5% (goal 10%) at 650nm. The NFM hosts several challenges and many subsystems will be pushed to their limits. The opto mechanical design and error budgets of GALACSI is described here.

We recall the design and present the development status of GRAAL, the Ground-layer adaptive optics assisted by Laser, which will deliver wide-field (10 arcmin), enhanced images to the HAWK-I instrument on the VLT, with an improved seeing. GRAAL is an adaptive optics module, part of the Adaptive optics facility (AOF), using four Laser- and one natural guide-stars to measure the turbulence, and correcting for it by deforming the adaptive secondary mirror of a Unit telescope in the Paranal observatory. GRAAL is in the laboratory in Europe and the integration of its laser guide-star optics is completed. The first wave-front sensor camera will be ready for its integration in the coming weeks, allowing the first system tests to start.

The ESO Very Large Telescope Adaptive Optics Facility (VLT-AOF) will transform the VLT Unit Telescope 4 to an Adaptive Telescope. In absence of an intermediate focus before the Adaptive Secondary in this Ritchey–Chrétien type telescope and in order to reduce the testing and calibration of the system on-sky, ASSIST, The Adaptive Secondary Setup and Instrument STimulator, was developed. It provides an off-sky testing facility for the ESO AOF and will provide a full testing environment for three elements of the VLT Adaptive Optics Facility: the Deformable Secondary Mirror (DSM) and the AO modules for MUSE and HAWK-I (GALACSI and GRAAL). ASSIST was delivered to ESO Garching, where it was assembled and tested. Currently ASSIST is being integrated with the Deformable Secondary Mirror, the first step in the full system testing of the two AO systems for the VLT AOF on ASSIST. This paper briefly reviews the design and properties of ASSIST and reports on the first results of ASSIST in stand-alone mode.

SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) is a second generation instrument for the VLT optimized for very high-contrast imaging around bright stars. Its primary science goal is the detection and characterization of giant planets, together with observation of circumstellar environment. The infrared differential imager and spectrograph (IRDIS), one of the three science instruments for SPHERE, provides simultaneous differential imaging in the near infrared, among with long slit spectroscopy, classical imaging and infrared polarimetry. IRDIS is designed to achieve very high contrast with the help of extreme-AO (Strehl < 90%), coronography, exceptional image quality (including non-common-path aberrations compensation), very accurate calibration strategies and very advanced data processing for speckle suppression. In this paper, we report on the latest experimental characterizations of IRDIS performed with SPHERE/SAXO before the preliminary acceptance in Europe.

We present laboratory results of the closed-loop performance of the Magellan Adaptive Optics (AO) Adaptive Secondary Mirror (ASM), pyramid wavefront sensor (PWFS), and VisAO visible adaptive optics camera. The Magellan AO system is a 585-actuator low-emissivity high-throughput system scheduled for first light on the 6.5 meter Magellan Clay telescope in November 2012. Using a dichroic beamsplitter near the telescope focal plane, the AO system will be able to simultaneously perform visible (500-1000 nm) AO science with our VisAO camera and either 10 μm or 3-5 μm science using either the BLINC/MIRAC4 or CLIO cameras, respectively. The ASM, PWS, and VisAO camera have undergone final system tests in the solar test tower at the Arcetri Institute in Florence, Italy, reaching Strehls of 37% in i'-band with 400 modes and simulated turbulence of 14 cm r_o at v-band. We present images and test results of the assembled VisAO system, which includes our prototype advanced Atmospheric Dispersion Corrector (ADC), prototype calcite Wollaston prisms for SDI imaging, and a suite of beamsplitters, filters, and other optics. Our advanced ADC performs in the lab as designed and is a 58% improvement over conventional ADC designs. We also present images and results of our unique Calibration Return Optic (CRO) test system and the ASM, which has successfully run in closedloop at 1kHz. The CRO test is a retro reflecting optical test that allows us to test the ASM off-sky in close-loop using an artificial star formed by a fiber source.

The Gemini North (GN) AO system, Altair, has been routinely operating in LGS mode since 2007. Due to the initial optical design, the NGS field-of-view (FoV) is limited to a radius ~ 25" which limits the potential science. To improve this, we have tested the AO/LGS operation using a peripheral wavefront sensor (PWFS) whose patrol field is ~ 4'-7' from the target. This expanded NGS FoV permits greater sky coverage but with decreased resolution, FWHM ~ 0.1" - 0.2" making this mode very suitable for non-imaging spectrographic and integral field unit observations. We present the hardware and software upgrades to PWFS and Altair as well as the software necessary for making this observing mode a routine and integral part of GN operations. Characterization and performance of this new operation mode, known as LGS+P1, are presented.

Raven is a Multi-Object Adaptive Optics (MOAO) scientific demonstrator which will be used on-sky at the Subaru observatory. Raven is currently being built at the University of Victoria AO Lab. In this paper, we present an overview of the final Raven design and then describe lab tests involving prototypes of Raven subsystems. The final design includes three open loop wavefront sensors (WFSs), a laser guide star WFS and two figure/truth WFSs. Two science channels, each containing a deformable mirror (DM), feed light to the Subaru IRCS spectrograph. Central to the Raven MOAO system is a Calibration Unit (CU) which contains multiple sources, a telescope simulator including two rotating phase screens and a ground layer DM that can be used to calibrate and test Raven. We are working with the Raven CU and open loop WFSs to test and validate our open loop calibration and alignment techniques.

The Lick Observatory 3-meter telescope has a history of serving as a testbed for innovative adaptive optics techniques. In 1996, it became one of the first astronomical observatories to employ laser guide star (LGS) adaptive optics as a facility instrument available to the astronomy community. Work on a second-generation LGS adaptive optics system, ShaneAO, is well underway, with plans to deploy on telescope in 2013. In this paper we discuss key design features and implementation plans for the ShaneAO adaptive optics system. Once again, the Shane 3-m will host a number of new techniques and technologies vital to the development of future adaptive optics systems on larger telescopes. Included is a woofer-tweeter based wavefront correction system incorporating a voice-coil actuated, low spatial and temporal bandwidth, high stroke deformable mirror in conjunction with a high order, high bandwidth MEMs deformable mirror. The existing dye laser, in operation since 1996, will be replaced with a fiber laser recently developed at Lawrence Livermore National Laboratories. The system will also incorporate a high-sensitivity, high bandwidth wavefront sensor camera. Enhanced IR performance will be achieved by replacing the existing PICNIC infrared array with an Hawaii 2RG. The updated ShaneAO system will provide opportunities to test predictive control algorithms for adaptive optics. Capabilities for astronomical spectroscopy, polarimetry, and visible-light adaptive optical astronomy will be supported.

In 2009, A 127-element adaptive system had been manufactured and installed at the Coude room of the 1.8-meter telescope at the Gaomeigu site of Yunnan Astronomical Observatory, Chinese Academy of Sciences. A set of new adaptive optical system based on a 73-element deformable secondary mirror is being developed and will be integrated into the 1.8-meter telescope. The 73-element deformable secondary mirror with convex reflecting surface is designed to be compatible with the Cassegrain focus of the 1.8-meter telescope. Comparing with the AO system of Coude focus, the AO system on the deformable secondary mirror adopts much less reflections and consequently restrains the thermal noise and increases the energy transmitting to the system. The design and simulation results of this system will be described in this paper. Furthermore, the preliminary test result of the deformable secondary mirror in the lab is also presented.

The CHARA Array is a six telescope optical/IR interferometer run by the Center for High Angular Resolution Astronomy of Georgia State University and is located at Mount Wilson Observatory just to the north of Los Angeles California. The CHARA Array has the largest operational baselines in the world and has been in regular use for scientific observations since 2004. In 2011 we received funding from the NSF to begin work on Adaptive Optics for our six telescopes. Phase I of this project, fully funded by the NSF grant, consists of designing and building wavefront sensors for each telescope that will also serve as tip/tilt detectors. Having tip/tilt at the telescopes, instead of in the laboratory, will add several magnitudes of sensitivity to this system. Phase I also includes a slow wavefront sensor in the laboratory to measure non-common path errors and small deformable mirrors in the laboratory to remove static and slowly changing aberrations. Phase II of the project will allow us to place high-speed deformable mirrors at the telescopes thereby enabling full closed loop operation. We are currently seeking funding for Phase II. This paper will describe the scientific rational and design of the system and give the current status of the project.

We look back on two years of experience with the laboratory MCAO testbed for the GREGOR solar telescope. GREGOR’s MCAO features four adaptive mirrors, i. e. one tip-tilt mirror, and three DMs to compensate for turbulence around 0 km, 5 km, and 15.5 km above ground. Two different Hartmann-Shack wavefront sensor units are used for wavefront tomography. A sensor with a narrow field of view and smaller subapertures is dedicated to high-order aberrations on the optical axis. This sensor directly follows the pupil plane DM and does not see the high-altitude DMs. The second sensor features larger subapertures and 19 guide regions spread over a wide field of view for off-axis wavefront sensing. We show that high-altitude DMs cause rapidly changing pupil distortions and thus misregistration, which renders the interaction of a pupil-plane DM and a subsequent wavefront sensor non-linear. We rewrote the control software for cleaner and more flexible code, and we switched to modal wavefront reconstruction from direct reconstruction. The original digital interfacing of the DMs high-voltage electronics didn’t prove to be reliable. Thus, we developed a new interface board that is based on CameraLink/ChannelLink technology to transmit the DM commands from the control computer. In this paper we present the innovations and some of the first experimental performance measurements with two DMs. One DM failed before scientific grade data was recorded with three DMs. This DM will be replaced soon. We conclude that GREGOR’s MCAO system is now ready for first on-sky tests at the telescope.

The portable solar adaptive optics is a compact adaptive optics system that will be the first visitor solar instrument in the world. As so, it will be able to work with any solar telescope with a aperture size up to ~ 2.0 meters, which will cover the largest solar telescope currently operational. The portable AO features small physical size, high-flexibility and high-performance, and is a duplicable and affordable system. It will provide wave-front correction down to the 0.5-μm wavelength, and will be used for solar high-resolution imaging in the near infrared and the visible. It will be the first AO system that uses LabVIEW based high quality parallel and block-diagram programming, which fully takes advantage of today's multi-core CPUs, and makes a rapid development of an AO system possible. In this publication, we report our recent progress on the portable adaptive optics, which includes the laboratory test for performance characterization, and initial on-site scientific observations.

METIS, the Mid-infrared E-ELT Imager and Spectrometer is foreseen to be the third instrument on the European Extremely Large Telescope (E-ELT) and the only instrument to provide high sensitivity mid-IR imaging and spectroscopy to the E-ELT. In order to reach the maximum resolution and sensitivity, an adaptive optics system is required. Since the operational wavelength of METIS is the longest of all E-ELT instruments and the field is relatively small, the complexity of the AO system is significantly reduced, both in required speed as well as order of the AO system. Adaptive Optics has been demonstrated to deliver consistently high performance for the current generation of 6-10 meter class telescopes at mid-infrared wavelengths, and similar performance is expected for METIS on the E-ELT. But in order to provide a reliable system on the E-ELT, several effects which have a minor impact on 6-8 meter class telescopes will need to be investigated for their impact on METIS AO. These effects include refractivity, atmospheric composition variations, but also the operation in a complex operational environment given by both METIS as well as the E-ELT. In this paper we describe the scientific requirements on the METIS AO system, the specific issues related to Adaptive Optics in the mid-IR and expected performance of the METIS AO system on the E-ELT.

The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation instrument planned for the Very Large Telescope (VLT) and the Adaptive Optics facility (AOF). It is an AO assisted instrument that will make use of the Deformable Secondary Mirror and the new Laser Guide Star Facility (4LGSF), and it is planned for the Cassegrain focus of the telescope UT4. The project is currently in its Phase A awaiting for approval to continue to the next phases. The Adaptive Optics system of ERIS will include two wavefront sensors (WFS) to maximize the coverage of the proposed sciences cases. The first is a high order 40x40 Pyramid WFS (PWFS) for on axis Natural Guide Star (NGS) observations. The second is a high order 40x40 Shack-Hartmann WFS for single Laser Guide Stars (LGS) observations. The PWFS, with appropriate sub-aperture binning, will serve also as low order NGS WFS in support to the LGS mode with a field of view patrolling capability of 2 arcmin diameter. Both WFSs will be equipped with the very low read-out noise CCD220 based camera developed for the AOF. The real-time reconstruction and control is provided by a SPARTA real-time platform adapted to support both WFS modes. In this paper we will present the ERIS AO system in all its main aspects: opto-mechanical design, real-time computer design, control and calibrations strategy. Particular emphasis will be given to the system performance obtained via dedicated numerical simulations.

The two first light adaptive optics (AO) instruments for the European Extremely Large Telescope (E-ELT) will both rely on several Sodium Laser Guide Stars (LGS). In using this technology, the E-ELT diameter comes with new challenges mainly raised by spot elongation. Before the final design studies of the E-ELT instruments, a Sodium LGS wavefront sensing (WFS) on-sky experiment at this scale is mandatory to provide meaningful spatial and temporal measurement error and performance evaluation. For this purpose, we propose to use CANARY, the Multi-Object AO demonstrator installed at the WHT (4.2m). CANARY is now undergoing a Rayleigh LGS upgrade and also provides natural guide star WFS. It could easily be adapted to the Sodium LGS case. Additionally, a transportable laser system, such as the one developed at ESO, positioned at a varying distance from the WHT could be used to provide off-axis launching (up to 40m), simulating the whole range of spot elongations that will be obtained on the E-ELT. Full scale simulations of a Sodium LGS WFS on the E-ELT have guided us in the definition of the experiment we are proposing. Previous simulation results in the literature have stressed that an estimate of the Sodium profile is necessary to reduce measurement error to an affordable level. Hence parallel Sodium profiling is mandatory in the proposed experiment. In this paper, we present the simulation results as well as the specifications for both the Sodium LGS WFS and profiler to be used on Canary.

Innovative optical interferometry test setups and control software techniques have been proposed for the E-ELT M4 adaptive optics mirror. The system is composed of three sub-systems: a CGH-based optical test tower, delivering a 1.5- m collimated beam, for fast simultaneous acquisition of large areas; a stitching interferometer, to calibrate at higher spatial frequencies, on smaller areas; and an optical piston sensor to remove differential piston and tilt between adjacent mirror segments.

The Giant Magellan Telescope presents a unique optical design with seven 8.4 m diameter primary mirrors matched by seven adaptive secondary mirrors (ASM). The ASMs can be controlled in several dierent Adaptive Optics (AO) observing modes coupled to the telescope . One of these AO systems, the Laser Tomography Adaptive Optics (LTAO) system is currently in its preliminary design phase. The LTAO observing mode will provide a Strehl ratio in H band of at least 30% over more than 20% of the sky and an ensquared energy in K band of at least 40% in a 50 milli-arcsec spaxel over more than 50% of the sky. To achieve its performance requirements, the LTAO observing mode uses six 20W Laser Guide Stars (LGS) with six order-60x60 Shack-Hartmann wavefront sensors. The LGSs are launched from three locations at the periphery of the telescope primaries. A natural guide star (NGS) is used separately to measure tip-tilt, focus and low-bandwidth-low-order aberrations, as well as telescope segment piston. An open-loop controlled deformable mirror corrects the o-axis NGS infrared wavefront. We give an update on the design of the LTAO WFSs, the LGS facility, the on-instrument wavefront sensors and the tomography and control algorithms.

The Laser Tomographic Adaptive Optics system for Giant Magellan Telescope (GMT) uses a single conjugated deformable mirror, the segmented Adaptive Secondary Mirror (ASM), to correct atmospheric wavefront aberrations with the help of a constellation of six laser beacons equally spaced on the sky. We will present different approaches for the design of the Laser Guide Star (LGS) Wave Front Sensor (WFS) system for GMT to cover all sodium emission altitudes and telescope elevations, from 80 km to 200 km range and how the preliminary design was derived from these approaches. The designed LGS WFS system includes a defocus-compensation mechanism working with a simple zooming optics to achieve the pupil image with constant pupil size, nearly constant wavefront correction, as well as pupil distortion correction. Either a trombone-mirror structure or a direct LGS-WFS translation is used for the defocus compensation, when conjugating the LGS altitudes in the sky. In the designs, a zooming collimator images the ASM in the GMT at the exit pupil of the LGS WFS system, where the designed lenslet-array is tailored for the selected CCD format for the required plate scale on the sky. Additionally, we have proposed a novel and simple solution for pupilimage segmentation when working with smaller CCD arrays. This novel solution consists of a single multi-aperture blaze grating for pupil segmentation in the system.

The Giant Magellan Telescope is planning to provide adaptive wavefront correction of the low layers (<1 km) of atmospheric turbulence in support of wide-field instrumentation. This ground-layer adaptive optics (GLAO) mode will use the adaptive secondary mirrors to provide improved image quality over approximately 7 arcminutes FOV. We present a comparison between the use of a sodium laser guide star asterism plus three tip-tilt natural guide stars versus natural guide stars only on the average seeing width improvement. The layout and components of both (laser beacon based and natural star only based) GLAO concepts are described and the impact and interaction with other GMT subsystems is analyzed.

The 25 m Giant Magellan Telescope consists of seven circular 8.4 m primary mirror segments with matching segmentation of the Gregorian secondary mirror. Achieving the diffraction limit in the adaptive optics observing modes will require equalizing the optical path between pairs of segments to a small fraction of the observing wavelength. This is complicated by the fact that primary mirror segments are separated by up to 40 cm, and composed of borosilicate glass. The phasing system therefore includes both edge sensors to sense high-frequency disturbances, and wavefront sensors to measure their long-term drift and sense atmosphere-induced segment piston errors. The major subsystems include a laser metrology system monitoring the primary mirror segments, capacitive edge sensors between secondary mirror segments, a phasing camera with a wide capture range, and an additional sensitive optical piston sensor incorporated into each AO instrument. We describe in this paper the overall phasing strategy, controls scheme, and the expected performance of the system with respect to the overall adaptive optics error budget. Further details may be found in specific papers on each of the subsystems.

The Imaka project is a ground layer adaptive optics system proposed for the Canada-France-Hawaii Telescope. This paper presents the optical design of a Cassegrain mounted ground layer adaptive optics system with a 0.8 degree field of view for Imaka. The design incorporates a Takeshi concentric ADC and a f/8 to f/5.7 reducer. This is followed with a novel double pass system to image the pupil on a 300mm mildly concave deformable mirror and re-image the system on the detector. The design meets the required 0.15" 80% encircled energy image performance, including correction for atmospheric dispersion. The optical design is presented with the predicted imaging performance.

A wide-field adaptive optics system based on an adaptive secondary mirror (ASM) is one of a future plan for the next-generation Subaru adaptive optics system. The main application of ASM based AO will be a groundlayer adaptive optics (GLAO) with field-of-view larger than 10 arc minutes. The high Strehl-ratio of on-source correction by high-order ASM (expected to be about 1000) and the reduction of emissivity are also attractive points. In this paper, we report a preliminary result of simulations for the these applications of ASM to study conceptual design of the next-generation wide-field Subaru adaptive optics.

The Southern African Large Telescope (SALT), located at the South African Astronomical Observatory (SAAO) site near Sutherland, South Africa, is an 11-metre fixed-elevation telescope currently operating at UV-visible wavelengths (320-950 nm) with a near-infrared extension (850-1700 nm) due in the near future. SALT does not currently have an adaptive optics (AO) system and a feasibility study for adding one is under way. Using results from an on-going site monitoring campaign at the SAAO we have begun carrying out simulations to investigate how different AO systems might perform and could be optimized for SALT. We will present the parameters of an optimization study and performance results for a single on-axis natural guide star (NGS) AO system on SALT for operation at both visible (R) and near-IR (J and H) wavelengths.

Detection of exoplanets implies the measure of extremely weak signals, usually below intensity perturbations in the PSF caused by static aberrations. We have finished the construction of a new test bench called FFREE - Fresnel Free Experiment for EPICS. The scope of the FFREE experiment is the active speckles correction using off-line cancellation techniques: Electric Field Conjugation and Phase Diversity, in view of a future instrument EPICS for the telescope EELT (ESO). We will describe the system and discuss some characteristics like the chromatism and the environmental stability of the bench.

The linearity and accuracy of holography-based modal wavefront sensing (HMWS) is reduced when large aberrations are present in the incoming wavefront. In this contribution, a combination of HMWS and a low-resolution Shack- Hartmann sensor (LRSHS) is introduced to extend the dynamic range of HMWS via a compact holographic design. The typically dominating low-order modes in the incoming wavefront are first corrected by the LRSHS. The system then switches to HMWS after one or two corrections to obtain better sensor sensitivity and accuracy. First experimental results are shown for validating the method.

We present progress towards the development of a woofer-tweeter adaptive optics (AO) system using the first 37 actuators of a 91-actuator magnetic-liquid deformable mirror (MLDM) and a magnetic 97-actuator DM from ALPAO. The MLDM, which has both very large single-actuator and inter-actuator strokes, but a low bandwidth, is used as woofer, whereas the high bandwidth and lower stroke ALPAO DM is used as tweeter. The ALPAO DM should improve the bandwidth of the MLDM while the MLDM will allow correction of strong aberrations.

Multi-object adaptive optics requires a tomographic reconstructor to compute the AO correction for scientific targets within the field, using measurements of incoming turbulence from guide stars angularly separated from the science targets. We have developed a reconstructor using an artificial neural network, which is trained in simulation only. We obtained similar or better results than current reconstructors, such as least-squares and Learn and Apply, in simulation and also tested the new technique in the laboratory. The method is robust and can cope well with variations in the atmospheric conditions. We present the technique, our latest results and plans for a full MOAO experiment.

We are developing an adaptive optics system for earth observing remote sensing sensor. In this system, high spatial resolution has to be achieved by a lightweight sensor system due to the launcher’s requirements. Moreover, simple hardware architecture has to be selected to achieve high reliability. Image based AOS realize these requirements without wavefront sensor. In remote sensing, it is difficult to use a reference point source unless the satellite controls its attitude toward a star or it has a reference point source in itself. We propose the control algorithm of the deformable mirror on the basis of the extended scene instead of the point source. In our AOS, a cost function is defined using acquired images on the basis of the contrast in spatial or Fourier domain. The cost function is optimized varying the input signal of each actuator of the deformable mirror. In our system, the deformable mirror has 140 actuators. We use basis functions to reduce the number of the input parameters to realize real-time control. We constructed the AOS for laboratory test, and proved that the modulated wavefront by DM almost consists with the ideal one by directly measured using a Shack- Hartmann wavefront sensor as a reference.

The Magellan AO system combines a pyramid wavefront sensor and high-order adaptive secondary mirror, and will see first light on the Magellan Clay telescope in November 2012. With a 24 cm projected actuator pitch, this powerful system will enable good correction in the optical (0.5 to 1 μm). Realistic laboratory testing has produced Strehl ratios greater than 40% in i’ (0.765 μm) on bright simulated stars. On fainter stars our visible AO camera, VisAO, will work in the partially corrected regime with only short moments of good correction. We have developed a form of lucky imaging, called real time frame selection, which uses a fast shutter to block moments of bad correction, and quickly opens the shutter when the correction is good, enabling long integrations on a conventional CCD while maximizing Strehl ratio and resolution. The decision to open or shut is currently based on reconstructed WFS telemetry. Here we report on our implementation and testing of this technique in the Arcetri test tower in Florence, Italy, where we showed that long exposure i’ Strehl could be improved from 16% to 26% when the selection threshold was set to the best 10% of instantaneous Strehl.

There is analyzed the possibility the general tilt correction of the wave front on base of the laser guide star (LGS) signal. The calculation of the image motion of the spherical wave (that position the source of radiation also fluctuated) with random center is conducted. The exact formula for random vector defining the position of the image of the spherical wave in focal plane of the telescope is offered. The variance of residual fluctuations has been calculated. The variance behavior of this residual motion from optical experiment parameters are analyses. The similar problem under solution of the some practical tasks, including the possibility of the wave front "global" tilt correction with using single LGS, can be appeared.

Space debris in low Earth orbit below 1500km is becoming an increasing threat to satellites and spacecrafts. Radar and laser tracking are currently used to monitor the orbits of thousands of space debris and active satellites are able to use this information to manoeuvre out of the way of a predicted collision. However, many satellites are not able to manoeuvre and debris-on debris collisions are becoming a signicant contributor to the growing space debris population. The removal of the space debris from orbit is the preferred and more definitive solution. Space debris removal may be achieved through laser ablation, whereby a high power laser corrected with an adaptive optics system could, in theory, allow ablation of the debris surface and so impart a remote thrust on the targeted object. The goal of this is to avoid collisions between space debris to prevent an exponential increase in the number of space debris objects. We are developing an experiment to demonstrate the feasibility of laser ablation for space debris removal. This laser ablation demonstrator utilises a pulsed sodium laser to probe the atmosphere ahead of the space debris and the sun reflection of the space debris is used to provide atmospheric tip{tilt information. A deformable mirror is then shaped to correct an infrared laser beam on the uplink path to the debris. We present here the design and the expected performance of the system.

The plenoptic camera has been proposed as an alternative wavefront sensor adequate for extended objects within the context of the design of the European Solar Telescope (EST), but it can also be used with point sources. Originated in the field of the Electronic Photography, the plenoptic camera directly samples the Light Field function, which is the four - dimensional representation of all the light entering a camera. Image formation can then be seen as the result of the photography operator applied to this function, and many other features of the light field can be exploited to extract information of the scene, like depths computation to extract 3D imaging or, as it will be specifically addressed in this paper, wavefront sensing. The underlying concept of the plenoptic camera can be adapted to the case of a telescope by using a lenslet array of the same f-number placed at the focal plane, thus obtaining at the detector a set of pupil images corresponding to every sampled point of view. This approach will generate a generalization of Shack-Hartmann, Curvature and Pyramid wavefront sensors in the sense that all those could be considered particular cases of the plenoptic wavefront sensor, because the information needed as the starting point for those sensors can be derived from the plenoptic image. Laboratory results obtained with extended objects, phase plates and commercial interferometers, and even telescope observations using stars and the Moon as an extended object are presented in the paper, clearly showing the capability of the plenoptic camera to behave as a wavefront sensor.

A low-order solar adaptive optics (AO) system, which consists of a fine tracking loop with a tip/tilt mirror and a correlation tracker, and a high-order correction loop with a 37-element deformable mirror, a correlating Shack-Hartmann wavefront sensor and a high-order wavefront correction controller, had been successfully developed and installed at 1-m New Vacuum Solar Telescope of Full-shine Lake (also called Fuxian Lake) Solar Observatory. This system is an update of the 37-element solar AO system designed for the 26-cm Solar Fine Structure Telescope at Yunnan Astronomical Observatory in 2009. The arrangement of subapertures of the Shack-Hartmann wavefront sensor was changed from square to hexagon to achieve better compensation performance. Moreover, the imaging channel of the updated system was designed to observe the Sun at 710nm and 1555nm simultaneously. The AO system was integrated into the solar telescope in 2011, and AO-corrected high resolution sunspots and granulation images were obtained. The observational results show that the contrast and resolution of the solar images are improved evidently after the correction by the AO system.

The analysis of the laser behavior on sky and of the adaptive optics system of SINFONI is made systematically since a year. This campaign of measurements will continue during the first semester 2012. The analysis, the results and the proposed optimization will be presented in this proceeding.

Image quality analyzer (IQA) which used as device for efficiency analysis of adaptive optics application is described. In analyzer marketed possibility estimations quality of images on three different criterions of quality images: contrast, sharpnesses and the spectral criterion. At present given analyzer is introduced on Big Solar Vacuum Telescope in stale work that allows at observations to conduct the choice of the most contrasting images of Sun. Is it hereinafter planned use the analyzer in composition of the ANGARA adaptive correction system.

Solar adaptive optics (AO) systems are developed at the 60cm domeless solar telescope in the Hida Observatory, Japan. An AO system currently used has a deformable mirror with high-speed 97 electromagnetic actuators and a Shack- Hartmann wavefront sensor with a 10x10-microlens array and 4000fps-CMOS camera. Its control frequency is about 1100-1400 Hz, and hence the -3dB cutoff frequency of the system is theoretically above 100 Hz. In parallel to developing the system, a new full-scaled AO system is designed to be applicable to various observations, such as highdispersion spectroscopy and simultaneous wide-range spectroscopy. The new system will work as classical AO at first. The details of the current system, observational results using it, and the design of the new AO system are described.

LBT contactless, voice-coil actuators working point ranges from 10 to 100 μm, with a typical position noise of a few nm. To fully take advantage of such large working range in AO operations, an absolute calibration of their capacitive sensor is requested. We implemented and tested an optical calibration technique that is based on a fast interferometer detection of a differential piston superimposed to a low order mirror mode. This procedure has been tested in dome environment at the Large Binocular Telescope.

With the commencement of shared-risk science observations in May 2012, the Keck I laser guide star (LGS) adaptive optics (AO) system is the second LGS AO system to be commissioned at the W. M. Keck Observatory. This paper reports on the Keck I LGS AO system itself and some of the initial performance results. The Keck I system differs from the Keck II system primarily with regards to the laser and a beam transport system which projects the laser from behind the telescope’s secondary mirror. The existing OSIRIS science instrument has been integrated with the Keck I system.

The adaptive module of the 4-m SOAR telescope (SAM) has been tested on the sky by closing the loop on natural stars. Then it was re-configured for operation with low-altitude Rayleigh laser guide star in early 2011. We describe the performance of the SAM LGS system and various improvements made during one year of on-sky tests. With acceptably small LGS spots of 1.6′′ the AO loop is robust and achieves a resolution gain of almost two times in the I band, under suitable conditions. The best FWHM resolution so far is 0.25′′ over the 3′ field of the CCD imager.

The Laser Guide Star facility ARGOS will provide Ground Layer Adaptive Optics to the Large Binocular Telescope (LBT). The system operates three pulsed laser beacons above each of the two primary mirrors, which are Rayleigh scattered in 12km height. This enables correction over a wide field of view, using the adaptive secondary mirror of the LBT. The ARGOS laser system is designed around commercially available, pulsed Nd:YAG lasers working at 532 nm. In preparation for a successful commissioning, it is important to ascertain that the specifications are met for every component of the laser system. The testing of assembled, optical subsystems is likewise necessary. In particular it is required to confirm a high output power, beam quality and pulse stability of the beacons. In a second step, the integrated laser system along with its electronic cabinets are installed on a telescope simulator. This unit is capable of carrying the whole assembly and can be tilted to imitate working conditions at the LBT. It allows alignment and functionality testing of the entire system, ensuring that flexure compensation and system diagnosis work properly in different orientations.

Present and future adaptive optics systems aim for the correction of the atmospheric turbulence over a large field of view combined with large sky coverage. To achieve this goal the telescope is equipped with multiple laser beacons. Still, to measure tip-tilt aberrations a natural guide star is used. For some fields such a tilt-star is not available and a correction on the laser beacons alone is applied. For this method to work well the laser beacons must not be affected by telescope vibrations on their up-link path. For the ARGOS system the jitter of the beacons is specified to be below 0.05. To achieve this goal a vibration compensation system is necessary to mitigate the mechanical disturbances. The ARGOS vibration compensation system is an accelerometer based feed forward system. The accelerometer measurements are fed into a real time controller. To achieve high performance the controller of the system is model based. The output is applied to a fast steering mirror. This paper presents the concept of the ARGOS vibration compensation, the hardware, and laboratory results.

We are developing a sodium guide star adaptive optics system for the 1.8 meter telescope, which consists of three main parts: (i) 20W microsecond pulsed laser system, (ii) Φ200mm laser launch telescope and (iii) 37-elements adaptive optics system. All of these three parts are mounted on the 1.8 meter telescope which is located in Gaomeigu site of Yunnan Astronomical Observatory, Chinese Academy of Sciences. The pulsed laser system and the launch telescope are rotated with the azimuthal base of the telescope. A miniaturized 37-elements low-order adaptive optics system including a 37-elelment deformable mirror and a 6x6 array Hartmann-Shack wavefront sensor is mounted at the Cassegrain focus taking account of the pulsed laser mode. A separate tip-tilt correction loop is also integrated into the system. This paper describes the details of this system, the simulation result and the test result in the lab. After the indoor test, the whole system will be shipped to 1.8 meter telescope. The latest commissioning status and results is presented also in this paper.

Long pulse length sodium laser guide stars (LGS) are useful because they allow for Rayleigh blanking and fratricide avoidance in multiple LGS systems. Bloch equation simulations of sodium-light interactions in Mathematica show that certain spectral formats and pulse lengths, on the order of 30 microseconds, with high duty cycles (20-50%) should be able to achieve photon returns within 10% of what is seen from continuous wave (CW) excitation. In this work, we investigate the time dependent characteristics of sodium fluorescence, and find the optimal format for the new LGS that will be part of the upgraded AO system on the Shane 3 Meter telescope at Mt. Hamilton. Results of this analysis are discussed along with their general applicability to other LGS systems. The potential benefits of uplink correction are also considered.

The vast majority of large telescopes are now equipped with Adaptive Optics (AO) systems, and many use lasers to create artificial stars (laser guide stars, LGS). Despite the significant advances in the use of LGS for AO, some problems persist during the operations. In particular, achieving a satisfactory performance in terms of on-sky laser power and beam quality usually requires frequent and complex alignments of the laser system, beam transfer optics and launch telescope. To provide easier calibrations and faster pre-setting of the LGS facility during routine operations, we propose the introduction of active elements (deformable mirrors) in the laser beam before it is propagated to the sky. The paper studies an AO configuration with two deformable mirrors to correct for quasi-static and dynamic aberrations. The problem of determining the correction phases to apply to the deformable mirrors is particularly challenging due to the highly nonlinear problem and the possible appearance of branch points. We propose an iterative method based on a phase retrieval algorithm that uses a weighted least squares unwrapper to avoid branch points. Simulations are performed aiming to a future implementation in the Gemini Multi-conjugate-adaptive-optics System (GeMS). Results show that the technique is accurate and robust, with a reasonable convergence speed.

TNO has developed the Optical Tube Assemblies (OTAs) for the ESO VLT Four Laser Guide Star Facility. The OTAs are Galilean 20x beam expanders, expanding a ∅15 mm input beam (25W, 589 nm CW) to a steerable ∅300 mm output beam. TNO has recently successfully completed acceptance testing of the four units, showing compliance to the challenging requirements on output wavefront quality, thermally induced defocus under operational conditions, absolute pointing accuracy and polarization extinction ratio (PER). TNO applied its corrective polishing in combination with the NANOMEFOS measurement machine to produce the ∅380 mm aspherical output lens, resulting in 20 nm rms output wavefront quality. The thermal behaviour of the system has been analyzed by combining optical, lumped mass and FE analyses. A design that is passively athermalized over a large temperature range as well as under the influence of thermal gradients has been developed. Extensive thermal testing has shown a thermally induced defocus of less than 0.15 waves under the operational conditions of 0-15°C and upto -0.7°C/hr gradient. A custom tip-tilt mechanism was designed to steer the output beam over a 4.8 arcmin radius, with less than 0.1" (3σ) accuracy at 1 Hz update rate. The PER was also measured under operational (thermal and tilt) conditions and demonstrated to be well above 99%. This paper describes the design, modelling and analysis, and the test results of these instruments.

Almost all the scientific instruments foreseen to be installed on the European Extremely Large Telescope claim for the Sodium Laser Guide Stars for an effective adaptive correction, over a large fraction of the sky, of the wavefront aberrated by the atmospheric turbulence. These artificial sources present an elongated, irregular and time variable intensity profile due to the density variations of the Sodium layer, where they form. On the focal plane of a Shack- Hartmann wavefront sensor, the baseline sensor of the adaptive optics modules, the laser guide stars appear as elongated spots on the lenslet array focal plane. Thus the local wavefront measurements inside the sub-apertures require some investigations to evaluate the performance of advanced centroiding algorithms for the extended spots position measurement to reduce the residual wavefront error. The laboratory prototype presented in this paper reproduces the expected conditions, for an Extremely Large Telescope case, when measuring the wavefront of a Laser Guide Star by means of a Shack-Hartmann wavefront sensor. A simplified version of the prototype has been successfully integrated and tested in 2010. We describe the design of new components, that permit to achieve the following features: a programmable setting of the elongated source intensity profile, to be able to reproduce realistically the time variable Sodium layer density vertical profile; the simulation, one at a time, of a multiple laser guide stars launching system by means of an optical derotator that rotates the elongated spot pattern on the detector plane; the implementation of a two layers turbulence model that introduces a differential wavefront aberration according to the azimuth angle of the laser guide stars and simulates the time evolution of the turbulence. The scheduled test program is finally presented.

Laser guide stars created in the earth's sodium layer are the choice for all ELTs as adaptive optics reference. With the thickness of the sodium layer spanning up to 10km, the apparent image of the guide stars on the adaptive optics wavefront sensors is elongated. The further away sub-apertures of the WFS are from the guide star launch location, the more elongated the guide star appears on the sensor. To counteract the decreased signal from the elongation, usually an increased laser power is demanded or special format radial CCDs are proposed. Another known possibility is to utilize pulsed lasers and follow dynamically the propagating pulse on its way through the sodium layer, creating a sharp spot at the wavefront sensor location. Similar processes have been used for laser guide stars created with Rayleigh scattering in the lower atmosphere, increasing greatly the number of photons that can be received from the guide star. We present here the design and first laboratory tests of such a dynamically refocus device, based on membrane mirrors. Driven acoustically at high frequencies the stroke and phase of the mirror can be controlled. With a compact appearance the system seems to be easy to use and could enable precise wavefront control with lower power pulsed lasers at ELTs and other telescopes.

The Gemini Multi-Conjugate Adaptive Optics System (GeMS) began its on-sky commissioning in January 2011. The system provides high order wide field corrections using a constellation of five Laser Guide Stars. In December 2011, commissioning culminated in images with a FWHM of 80±2mas at 1.65 microns (H band) over an 87 x 87 arcsecond field of view. The first images have already demonstrated the scientific potential of GeMS, and after more than a year of commissioning GeMS is finally close to completion and ready for science. This paper presents a general status of the GeMS project and summarizes the achievements made during more than a year of commissioning. The characterization of GeMS performance is presented in a companion paper: “GeMS on-sky results”, Rigaut et al. Here we report on the sub-systems' performance, discuss current limitations and present proposed upgrades. The integration of GeMS into the observatory operational scheme is detailed. Finally, we present the plans for next year's operations with GeMS.

The astronomical community's use of high power laser guide star adaptive optics (LGS-AO) systems presents a potential hazard to aviation. Historically, the most common and trusted means of protecting aircraft and their occupants has been the use of safety observers (aka spotters) armed with shut-off switches. These safety observers watch for aircraft at risk and terminate laser propagation before the aircraft can be adversely affected by the laser. Efforts to develop safer and more cost-effective automated aircraft protection systems for use by the astronomical community have been inhibited by both technological and regulatory challenges. This paper discusses recent developments in these two areas. Specifically, with regard to regulation and guidance we discuss the 2011 release of AS-6029 by the SAE as well as the potential impact of RTCA DO-278A. With regard to the recent developments in the technology used to protect aircraft from laser illumination, we discuss the novel Transponder Based Aircraft Detection (TBAD) system being installed at W. M. Keck Observatory (WMKO). Finally, we discuss our strategy for evaluating TBAD compliance with the regulations and for seeking appropriate approvals for LGS operations at WMKO using a fully automated, flexibly configured, multi-tier aircraft protection system incorporating this new technology.

The Laser Traffic Control System (LTCS) is a software solution to the problem of laser beam avoidance, using priority based collision resolution and an optional built-in laser shutter command interface. LTCS uses static site survey information, dynamic telescope pointing and control data, and a configurable "rules" scheme, to monitor laser beam geometry (Rayleigh and LGS) and warn or prevent undesired emission at participating institutions. LTCS was developed for use on Mauna Kea in 2001, but through collaborative efforts with multiple institutions, has since been enhanced and installed at several sites around the world. Functional implementations, either operational or in prototype form, exist for Mauna Kea, La Palma, Cerro Pachon, Cerro Paranal, and Haleakala. Since the last LTCS SPIE update in 2006, many important features have been added. There has also been some new site testing activity that has resulted in lessons learned and the development of new analysis/test tools. Finally, an important lasing operations paradigm shift has emerged on Mauna Kea and is anticipated for Paranal. The trend is clearly away from static collision priority rule determination, toward dynamic "negotiated" priority determination. The implications of this paradigm shift, discussion of forced collision test results and lessons learned, and a status update on development activities since the last update will be presented in the paper.

MPIA leads the construction of the LINC-NIRVANA instrument, the MCAO-supported Fizeau imager for the LBT, serves as pathfinder for future ELT-AO imagers in terms of size and technology. In this contribution, we review recent results and significant progress made on the development of key items of our stratgey to achieve a piston stability of up to 100nm during a science exposure. We present an overview of our vibration control strategies for optical path and tip-tilt stabilization, involving accelerometer based real-time vibration measurements, vibration sensitive active control of actuators, and the development of a dynamical model of the LBT. MPIA also co-develops the E-ELT first-light NIR imager MICADO (both SCAO and MCAO assisted). Our experiences, made with LINC-NIRVANA, will be fed into the MICADO structural AO design to reach highest on-sky sensitivity.

We present our recently started eort to realize feedforward vibration control loops with a full adaptive optics (AO) testbed in the laboratory. A piezo-driven tip-tilt mirror unit introduces an arbitrary, but controllable, vibration power-spectrum to simulate telescope mirror vibrations of any kind on the wavefront sensor. Our ultimate goal is to demonstrate in realistic laboratory tests, how telescope vibrations faster than atmospheric tip-tilt can be measured by accelerometers, and controlled in real-time feedforward to allow for longer and more sensitive wavefront sensor (WFS) integrations.

In the framework of the European ELT design, partially open-loop MCAO systems, coupled with virtual DMs, have been proposed to achieve AO correction using solely NGSs, to be selected in a FoV as wide as allowed by the Telescope optical design. The conceptual design of a very compact wavefront sensor, exploiting the just mentioned concept and characterized by a dynamic range limited by the stroke of the Deformable Mirror and by a limiting magnitude performance typical of a closed loop coherent wavefront sensor, have been presented in the past. This concept was based on the usage of a very linear wavefront sensor, like a YAW sensor, but a DM having the actual shape known “a-priori” could simplify a lot the design of such a compact WFS. We investigate here the realm of possible opto-mechanical realization of a probe, capable to co-exist with the currently foreseen E-ELT LGS probes and giving the possibility to exploit the open loop wavefront sensing operation with the aim of reaching a preliminary design of such a system. Furthermore, we devise a conceptual opto-mechanical design of a precursor of such a system, which could exploit at the VLT Global MCAO correction on the lower part of the atmosphere.

DRAGON is be a new and in many ways unique visible light adaptive optics test bench. Initially, it will test new and existing concepts for CANARY, the laser guide star tomographic adaptive optics demonstrator on the WHT, then later it will be used to explore concepts for other existing and future telescopes. Natural and Laser Guide Stars (NGS and LGS) are emulated, where the LGSs exhibit the effects of passing up through turbulence and spot elongation. AO correction is performed by one high and one low order deformable mirror, allowing woofer-tweeter control, and multiple high and low order wave front sensors detect wave front error. The Durham Adaptive Optics Real-time Controller (DARC) is used to provide real-time control over various DRAGON configurations. DRAGON is currently under construction, with the turbulence simulator completed. Construction and alignment of the system is expected to be finished in the coming year, though first results from completed modules follow sooner.

For the last few years, LAM has been carrying out several R&D activities in Adaptive Optics (AO) instrumentation for Extremely Large Telescopes (ELTs). In the European ELT framework, a multi-purpose AO bench is developed to allow the experimental validation of new instrumental concepts dedicated to the next generation of ELTs. It is based on the use of a Shack-Hartmann wave-front sensor in front of a 140 actuators micro-deformable mirror (Boston Micromachines), dedicated to “low orders” modes, while a Pyramid wave-front sensor (PWFS) will be combined to a Liquid Crystal Spatial Light Modulator for “high orders” correction. Both systems could be merged in a two stages AO concept allowing to study the coupling of a telescope pre-correction using a dedicated large M4 deformable mirror and a post focal high order AO system. Analysis and optimisation of the spatial and temporal splits of the AO correction between the two systems is therefore essential. Finally, we will use the world’s fastest and most sensitive camera system OCAM (developed at LAM) coupled with the pyramid , to demonstrate the concept of a fast and hyper-sensitive PWFS (up to 100x100 sub-pupils) dedicated to the first generation instruments for ELTs.

This paper presents an update on the design and deployment of the HIA MCAO laboratory bench. This bench directly supports the development of NFIRAOS, the first light MCAO facility for the Thirty Meter Telescope. The bench implements a closed-loop MCAO system, with two magnetic DMs, four LGS Shack-Hartmann WFSs, two NGS T/T WFS, one NGS T/T/F WFS and one higher order Truth WFS, making up a scaled down version of NFIRAOS. The bench includes several artificial turbulence screens and reproduces realistic LGS spot elongations. It is driven by software in Matlab, frame-rates ranging from 1Hz to 15Hz. The goals of this bench are to anchor the NFIRAOS end-toend simulation tools; to exercise real-time LGS tomographic AO in a variety of well controlled conditions, such as faint and poorly corrected NGSs, non-uniformities in the sodium layer and field dependant Non-Common-Path Aberrations (NCPAs); develop and demonstrate calibration procedures, such as PSF reconstruction and tomographic reconstruction and correction of field dependant NCPAs; and to validate optimization methods that operate at 10+ second time scales, which is not tractable in a numerical simulation, such as matched filter update and Cn2 estimation using a SLODAR method.

ARGOS, the wide eld Laser Guide Stars adaptive optics system for the Large Binocular Telescope, is now entering its installation phase. In the meanwhile, we have started a test bench in order to integrate various Argos sub-systems and demonstrate its wavefront measurements. To this objective, we rst validate three key components of the Argos wavefront sensor which we then integrate together. The test bench therefore comprises the Argos wavefront camera system - including a large frame, fast framerate, high quantum eciency and low readout noise pnCCD -, the slope computer, and a optical gating unit. While we present here the demonstration of those three key components, it is also a step to their system level integration that enables us to validate the wavefront measurements in term of noises, timing and computation. In the near future, those system will be integrated to the wavefront sensor system of ARGOS.

Achieving the diffraction limit with the adaptive optics system of the 25m Giant Magellan Telescope will require that the 7 pairs of mirror segments be in phase. Phasing the GMT is made difficult because of the 30-40cm gaps between the primary mirror segments. These large gaps result in atmospheric induced phase errors making optical phasing difficult at visible wavelengths. The large gaps between the borosilicate mirror segments also make an edge sensing system prone to thermally induced instability. We describe an optical method that uses twelve 1.5-m square subapertures that span the segment boundaries. The light from each subaperture is mapped onto a MEMS mirror segment and then a lenslet array which are used to stabilize the atmospherically induced image motion. Centroids for stabilization are measured at 700nm. The piston error is measured from the fringes visible in each of the 12 stabilized images at 2.2 microns. By dispersing the fringes we can resolve 2π phase ambiguities. We are constructing a prototype camera to be deployed at the 6.5m Magellan Clay telescope.

Raven is a Multi-Object Adaptive Optics (MOAO) technical and scientific demonstrator which will be used on the Subaru telescope with the IRCS spectrograph. The optical and mechanical designs are finalised and the system is now being integrated in the lab at UVic. Raven features three open-loop wavefront sensors (WFS) patrolling a 3.5' field of regard, one on-axis LGS WFS, two science channels each equipped with a pick-off arm, an 11x11 actuator deformable mirror, a closed-loop WFS for calibration and performance comparison and an image rotator. This paper presents in detail the optical design and its performance, as well as the mechanical design.

INO has designed, assembled and tested the Raven Multi-Object Adaptive Optics demonstrator calibration unit. This sub-system consists in a telescope simulator that will allow aligning Raven's components during its integration, testing its Adaptive Optics performances in the laboratory and at the telescope, and calibrating the Adaptive Optics system by building the interaction matrix and measuring the non-common path aberrations. The system is presented with the challenges that needed to be overcome during the design and integration phases. The system test results are also presented and compared to the model predictions.

We are conducting AO development activities in Tohoku university targeting Multi-Object Adaptive Optics (MOAO) system for the next generation ground-based large telescopes. In order to evaluate the accuracy of the tomographic estimation, which is a key of an MOAO system, we assembled a test optical bench to simulate an MOAO system in our optical lab. The system consists with 1) four light sources with single-mode fibers simulating three guide stars and one target object, 2) multiple phase plates simulating atmospheric turbulence structure, and 3) 4 Shack-Hartmann wavefront sensors. Wavefront data from the sensors are reduced with the tomographic algorithm. The evaluation of the accuracy of the tomographic wavefront reconstruction is underway. Additionally, evaluation of an open-loop control of an AO system is underway using an independent module. Once the accuracy of the open-loop control is established, the module will be installed in the tomography test bench and the entire system will be evaluated as an MOAO system. In parallel, we are conducting a development of a large stroke (20μm) Micro Electro Mechanical Systems (MEMS) deformable mirror with large number of elements (<3000). Current status of the development is described.

This paper summarizes results received by authors for last decade on the problem of the atmospheric coherence turbulence. Also shows some new results of the unpublished researches. According to our data the coherent turbulence is the result of the self-organizing non-linear processes in continuous media, including in the atmospheric air. New theoretical and experimental data are considered, it confirm the effect of the decreasing of the optical waves fluctuations in the coherence turbulence.

New techniques of Adaptive Optics (AO), generically called Wide Field AO, have been developed in the frame of the design study for new instruments for Extremely Large Telescopes (ELI). Concepts such as Multi-Conjugate AO are based on a tomographic reconstruction of the turbulent volume followed by a projection onto DM(s) in order to ensure a good correction in a large Field of View. These systems require a 3D phase reconstruction and a statistical representation of the turbulent volume through the knowledge of the Cn² profile, which has a strong impact on performance. We focus our study on the analysis of the impact of the structure and the parameters, which define the Cn² profile, on the performance of a given tomographic system for an ELI. In this article, we perform simulation to emphasize the terms which are directly linked to the knowledge of the true input Cn² profile, which simulates the input turbulent perturbations, and to the Cn² profile which is used as a model in the reconstruction process. We determine and discuss the level of the accuracy needed on the Cn² profile to limit the tomographic error term and to ensure a good performance. We show that a good sampling of the input turbulence is required to ensure performance of the system.

The precise reconstruction of the turbulent volume is a key point in the development of new-generation Adaptive Optics systems. We propose a new C²_n profilometry method named CO-SLIDAR (COupled Slope and scIntillation Detection And Ranging), that uses correlations of slopes and scintillation indexes recorded on a Shack-Hartmann from two separated stars. CO-SLIDAR leads to an accurate C²_n retrieval for both low and high altitude layers. Here, we present an end-to-end simulation of the C²_n profile measurement. Two Shack-Hartmann geometries are considered. The detection noises are taken into account and a method to subtract the bias is proposed. Results are compared to C²_n profiles obtained from correlations of slopes only or correlations of scintillation indexes only.

We present very encouraging preliminary results obtained in the context of the MOSE project, an on-going study aiming at investigating the feasibility of the forecast of the optical turbulence and meteorological parameters (in the free atmosphere as well as in the boundary and surface layer) at Cerro Paranal (site of the Very Large Telescope - VLT) and Cerro Armazones (site of the European Extremely Large Telescope - E-ELT), both in Chile. The study employs the Meso-Nh atmospheric mesoscale model and aims at supplying a tool for optical turbulence forecasts to support the scheduling of the scientific programs and the use of AO facilities at the VLT and the E-ELT. In this study we take advantage of the huge amount of measurements performed so far at Paranal and Armazones by ESO and the TMT consortium in the context of the site selection for the E-ELT and the TMT to constraint / validate the model. A detailed analysis of the model performances in reproducing the atmospheric parameters (T, V, p, H, ...) near the ground as well as in the free atmosphere, is critical and fundamental because the optical turbulence depends on most of these parameters. This approach permits us to provide an exhaustive and complete analysis of the model performances and to better define the model operational application. This also helps us to identify the sources of discrepancies with optical turbulence measurements (when they appear) and to discriminate between different origins of the problem: model parameterization, initial conditions, ... Preliminary results indicate a great accuracy of the model in reproducing most of the main meteorological parameters in statistical terms as well as in each individual night in the free atmosphere and in proximity of the surface. The study is co-funded by ESO and INAF-Arcetri (Italy).

In the context of the MOSE project, in this contribution we present a detailed analysis of the Meso-NH mesoscale model performances and their dependency on the model and orography horizontal resolutions in proximity of the ground. The investigated sites are Cerro Parana!(site of the ESO Very Large Telescope- VLT) and Cerro Armazones (site of the ESO European Extremely Large Telescope- E-ELT), in Chile. At both sites, data from a rich statistical sample of different nights are available- from AWS (Automated Weather Stations) and masts - giving access to wind speed, wind direction and temperature at different levels near the ground (from 2 m to 30m above the ground). In this study we discuss the use of a very high horizontal resolution (Δ X=O.l km) numerical configuration that overcomes some specific limitations put in evidence with a standard configuration with Δ X=0.5 km. In both sites results are very promising. The study is co-funded by ESO and INAF.

In this paper, we present simulation work done on AO systems for the E-ELT. We study the influence of the number of Laser Guide Stars (LGS) on system performance. Then, we investigate the impact of the conjugation height of the M4 adaptive mirror on GL/LT/MC-AO. Finally, we compare the results of a Fourier code and end-to-end models on the position of the LGS in the field of view.

An MOAO corrected multi-IFU instrument, such as the EAGLE instrument proposed for the E-ELT has a deformable mirror correcting each IFU sub-field. Additionally, EAGLE will also use the E-ELT deformable M4 mirror to apply a global (closed-loop) MOAO correction. Here, we investigate the impact on MOAO performance if a global GLAO correction is applied across the whole field, rather than the optimised global MOAO correction (which may or may not be identical). The differences in M4 correction (between GLAO and optimal MOAO) will depend on the position of IFU pick-offs in the science field, and also on the turbulence, for example, MOAO DM stroke may be minimised if more than the ground layer is corrected by the M4 DM, depending on how fast turbulence decorrelates across the field of view. We consider the impact on MOAO DM stroke, the effect on performance, and study both tomographic and non-tomographic GLAO corrections. Such a situation may arise if for example a combined multi-object spectrograph and multi-IFU instrument is designed, such as would result from the integration of EAGLE with another proposed E-ELT instrument. We demonstrate here that performance of EAGLE will not be significantly affected by being placed behind another such instrument. The results presented will be obtained using full end-to-endMonte-Carlo simulations using the Durham AO Simulation Platform. We also present a number of algorithms which can be used to improve AO performance, both in pixel processing and multi-mirror control.

Multi-Object Adaptive Optics (MOAO) is an open loop aproach to wide field AO which uses measurements from multiple guide stars (GS) to compute an estimate of the atmospheric turbulence in any direction within the GS asterism. Rather than trying to extend correction over the entire field as in Multi-Conjugate AO (MCAO), MOAO seeks only to generate high quality correction in specific directions with multiple deformable mirrors (DM), each driving the correction for an individual direction. A tomographic reconstructor uses the slopes sensed by the GS WFSs to estimate the atmospheric turbulence in the science directions. Raven is a MOAO science and technology demonstrator which is currently under development; testing of tomography algorithms is being carried out in order to begin verifying that the results predicted in simulation will be achievable with the real system.

Error budgets are an indispensable tool for assuring that project requirements can be and are being met. An error budget will typically include terms associated with subsystems which are being designed by different teams of engineers, and fabricated by different vendors. It is a useful tool at all levels of design since it provides a means to negotiate design trades in the broadest possible context. Error budgeting is in many ways fundamental to the mission of systems engineering and of course to the overall project success. In this paper we will describe the GMT Adaptive Optics System flow down requirements and their integration with their wavefront error budgets. We will focus on the GMT Adaptive Optics wavefront error budgets for the following observing modes: Natural Guide Star Adaptive, Laser Tomography Adaptive Optics and Ground Layer Adaptive Optics. Finally, a description of the error budgets and the close link between the error budgets and other parameter such as sky coverage, zenith angle, etc., will be discussed in this paper.

The European Solar Telescope (EST) will be a 4-meter diameter world-class facility, optimized for studies of the magnetic coupling between the deep photosphere and upper chromosphere. It will specialize in high spatial resolution observations and therefore it has been designed to incorporate an innovative built-in Multi-Conjugate Adaptive Optics system (MCAO). It combines a narrow field high order sensor that will provide the information to correct the ground layer and a wide field low order sensor for the high altitude mirrors used in the MCAO mode. One of the challenging particularities of solar AO is that it has to be able to correct the turbulence for a wide range of observing elevations, from zenith to almost horizon. Also, seeing is usually worse at day-time, and most science is done at visible wavelengths. Therefore, the system has to include a large number of high altitude deformable mirrors. In the case of the EST, an arrangement of 4 high altitude DMs is used. Controlling such a number of mirrors makes it necessary to use fast reconstruction algorithms to deal with such large amount of degrees of freedom. For this reason, we have studied the performance of the Fractal Iterative Method (FriM) and the Fourier Transform Reconstructor (FTR), to the EST MCAO case. Using OCTOPUS, the end-to-end simulator of the European Southern Observatory, we have performed several simulations with both algorithms, being able to reach the science requirement of a homogeneous Strehl higher that 50% all over the 1 arcmin field of view.

FrIM-3D is a novel algorithm developed for high performance in Adaptive Optics (AO) on the Extremely Large Telescopes. It particularly solves the problem of the minimum-variance tomographic reconstruction involved in AO. Until recently however, it was missing an optimal projection of the reconstructed atmosphere on the space of deformable mirrors, to guarantee the best performance for every tomographic AO system. In this paper, we present a formal solution to this projection problem. For that, a formalism based on continuous functions and modeling of the AO is chosen, in order to clearly analyze the modeling approximations. The projector is defined as the solution of an optimization problem with respect to AO objectives, potentially different for every wide-field AO system. After the projector derivation, we describe a fast algorithm to apply it, and in particular how to handle the piston-removal computations. This algorithm is currently being implemented as part of FrIM-3D.

The Antarctic is an ideal place for optical and infrared astronomy observations. Chinese scientists are planning to build a 2.5m telescope in Dome A. The telescope will be built in a tower about 15 meters high to avoid the ground layer atmospheric turbulence. The Ground layer Adaptive Optics system (GLAO) will also be suggested to be installed to further reduce the seeing. The GLAO system with one laser guide star, one deformable mirror and one wide field Shack-Hartmann wavefront sensor is designed and simulated. The Strehl ratio has increased 2 to 3 times in visible and infrared band in 20 arc min field of view.

On the basis of 95500 MASS/DIMM measurements of optical turbulence profile obtained on Mt. Shatdzhatmaz in 2009-2011 we have constructed 2 atmosphere models for this summit: one consisting of 9 typical turbulence profiles, and other of 300 randomly selected profiles. Profiles represent Cn2 and wind speed values estimated at 13 standard MASS altitudes. We discuss advantages and disadvantages of these models from the point of view of AO simulation. We used these models as input parameters in analytical simulation (PAOLA tool) of AO system of future 2.5-m telescope of SAI. This simulation was used to estimate optimal parameters of this system and performance characteristics corresponding to these parameters. Second 300-profiles atmosphere model allowed to evaluate the performance in terms of statistical distributions of metrics. E.g. for subaperture size 0.35 m and optimizable exposure (lower limit 2 ms), the NGS AO system will deliver Strehl ratio more than 0.46 in R-band using R=13 guide star for 10% of time.

This paper presents the performance analysis based on numerical simulations of the Pyramid Wavefront sensor Module (PWM) to be included in ERIS, the new Adaptive Optics (AO) instrument for the Adaptive Optics Facility (AOF). We have analyzed the performance of the PWM working either in a low-order or in a high-order wavefront sensing mode of operation. We show that the PWM in the high-order sensing mode can provide SR > 90% in K band using bright guide stars under median seeing conditions (0.85 arcsec seeing and 15 m/s of wind speed). In the low-order sensing mode, the PWM can sense and correct Tip-Tilt (and if requested also Focus mode) with the precision required to assist the LGS observations to get an SR > 60% and > 20% in K band, using up to a ~16.5 and ~19.5 R-magnitude guide star, respectively.

ERIS is a new Adaptive Optics Instrument for the Adaptive Optics Facility of the VLT that foresees, in its design phase, a Pyramid Wavefront Sensor Module (PWM) to be used with the VLT Deformable Secondary Mirror (VLT-DSM) as corrector. As opposite to the concave secondary mirrors currently in use (e.g. at LBT), VLT-DSM is convex and calibration of the interaction matrix (IM) between the PWM and the DSM is not foreseen on-telescope during day-time. In this paper different options of calibration are evaluated and compared with particular attention on the synthetic evaluation and on-sky calibration of the IM. A trade-off of the calibration options, the optimization techniques and the related validation with numerical simulations are also provided.

New tomographic Adaptive Optics (AO) concepts require a good knowledge of the system geometry and characteristics. These parameters are used to feed the tomographic reconstructors. In this paper we present a method to precisely identify the parameters required to construct an accurate synthetic set of models such as inuence functions, mis-registrations, directions of analysis or altitude of the DMs. The method is based on a multiparameter t of the interaction matrix. This identication method nds also its application in high contrast AO systems, such as SPHERE : in that case it is used as a diagnostic tool in order to precisely realign the system. The method has been tested and successfully implemented on HOMER, SPHERE and GeMS. Experimental results for these three systems are presented.

The employment of adaptively controlled segmented mirror architectures has become increasingly common in the development of current astronomical telescopes. Optomechanical analysis of such hardware presents unique issues as compared to that of monolithic mirror designs. Performance analysis issues include simulation of adaptive control, execution of polynomial fitting, calculation of best fit rigid body motions, and prediction of line-of-sight error. The generation of finite element models of individual segments involves challenges associated with correctly representing the geometry of the optical surface. Design issues include segment structural design optimization and optimum placement of actuators. Manufacturing issues include development of actuation inputs during stressed optic polishing. Approaches to all of the above issues are presented and demonstrated by example with SigFit, a commercially available tool integrating mechanical analysis with optical analysis.

With the emergence of General Purpose computations on Graphic Processing Units (GP-GPUs) this architecture has become amazingly attractive for large scale applications such as numerical simulations of complex systems. While the number of degrees of freedom of an adaptive optics (AO) system scales with the square of the telescope diameter, the system model exhibits a rather high level of parallelism especially when simulating Shack-Hartmann (SH) wavefront sensors (WFS). The use of massively parallel devices such as GPUs to simulate next generation AO systems for the European Extremely Large Telescope (E-ELT) thus makes a lot of sense. Our team has developed such simulation tools and first results show that speeds of about a thousand of iterations per second were achievable on a single high-end GPU for an eXtreme (X)AO system such as SPHERE including a single layer turbulence model generated on-the-fly. These numerical models include all the operations executed by the real-time controller (RTC) of a real system. The achieved simulation speeds show that a single high-end GPU could drive a XAO system on the VLT and, depending on the centroiding algorithm and the control scheme chosen, could even drive a classical AO system on the E-ELT. While the main challenge resides in the data transfer speed to and from the GPU, developing and testing AO control algorithms for the simulation code on the same hardware as the system RTC would bring a lot of benefits. In this paper we present the simulation results as well as strategies to build GPU-powered AO systems.

Adaptive Optics systems for the new generation of extremely large telescopes require fast mathematical methods for the computation of the shape of the deformable mirrors. MCAO or MOAO systems use laser guide stars for the reconstruction of the turbulent atmosphere. However, measurements from laser guide stars contain no information on the tip/tilt of the incoming wavefronts. Assuming that additional tip/tilt measurements of wavefronts from natural guide stars are available, we present an iterative Kaczmarz reconstructor that computes the turbulent atmospheric layers from the wavefronts of both the laser and natural guide stars. We show in particular that the resulting algorithm meets the quality and speed requirements for ELTs.

The atmospheric optical turbulence profile, the strength of the turbulence as a function of altitude above the ground, can be used to determine the seeing statistics of a particular site. This information is useful for optimizing the tomographic process in Adaptive Optics systems and for characterizing the performance. In this paper, we describe a method to estimate the atmospheric turbulence profile based on the telemetry data coming out of GeMS, a Multi Conjugated Adaptive Optics (MCAO) instrument installed on the Gemini South telescope. The method is based on the SLODAR technique (SLOpe Detection and Ranging), where the wavefront slopes from two stars angularly separated on the sky are measured, and their cross-correlation is used to retrieve the atmospheric optical profile. We have modified the classical SLODAR method and adapted it for the closed loop, multiple laser guide stars case. In this paper we present our method, validation of it in simulation, and its application for on-sky data.

In an AO system the correction to be applied to the Deformable Mirror is computed at each loop cycle from the residual slopes on the Wavefront Sensor and the Interaction Matrix of the system DM/WFS. But the a posteriori analysis of the DM commands and WFS slopes can also provide a wealth of information on the closed loop behavior. In this paper we present a non-exhaustive list of what can be learned from such data. We base our analysis on simulated data, on data recorded on ESO’s PEACE test bench, and on data recorded on the NAOS instrument at the VLT during technical nights in 2010 and 2011, in the framework of the preparation of the algorithms for the AO Facility. The topics presented include the reconstruction of the input turbulence in the WFS domain (pseudo open-loop slopes), the estimation of the seeing, turbulence profile, coherence time, wind speed and direction, the measurement of LGS spot size, the detection of vibrations via modal transfer functions, the identification of DM/WFS mis-registration and the optimal loop gain computation.

Adaptive Optics (AO) images are characterized by structured Point Spread Function (PSF), with sharp core and extended halo, and by significant variations across the field of view. In order to enable the extraction of high-precision quantitative information and improve the scientific exploitation of AO data, efforts in the PSF modeling and in the integration of suitable models in a code for image analysis are needed. We present the current status of a study on the modeling of AO PSFs based on observational data taken with present telescopes (VLT and LBT). The methods under development include parametric models and hybrid (i.e. analytical / numerical) models adapted to various types of PSFs that can show up in AO images. The specific features of AO data, such as the mainly radial variation of the PSF with respect to the guide star position in single-reference AO, are taken into account as much as possible. The final objective of this project is the development of a flexible software package, based on the Starfinder code (Diolaiati et Al 2000), specifically dedicated to the PSF estimation and to the astrometric and photometric analysis of AO images with complex and spatially variable PSF.

The resolution of ground-based telescopes is dramatically limited by the atmospheric turbulence.. Adaptative optics (AO) is a real-time opto-mechanical approach which allows to correct for the turbulence effect and to reach the ultimate diffraction limit astronomical telescopes and their associated instrumentation. Nevertheless, the AO correction is never perfect especially when it has to deal with large Field of View (FoV). Hence, a posteriori image processing really improves the final estimation of astrophysical data. Such techniques require an accurate knowledge of the system response at any position in the FoV The purpose of this work is then the estimation of the AO response in the particular case of the MUSE [1] /GALACSI [2] instrument (a 3D mult-object spectrograph combined with a Laser-assisted wide field AO system which will be installed at the VLT in 2013). Using telemetry data coming from both AO Laser and natural guide stars, a Point Spread Function (PSF) is derived at any location of the FoV and for every wavelength of the MUSE spectrograph. This document presents the preliminary design of the MUSE WFM PSF reconstruction process. The various hypothesis and approximations are detailed and justified. A first description of the overall process is proposed. Some alternative strategies to improve the performance (in terms of computation time and storage) are described and have been implemented. Finally, after a validation of the proposed algorithm using end-to-end models, a performance analysis is conducted (with the help of a full end-to-end model). This performance analysis will help us to populate an exhaustive error budget table.

Images obtained with adaptive optics (AO) systems can be improved by using restoration techniques, the AO­ correction being only partial. However, these methods require an accurate knowledge of the system point spread function (PSF). Adaptive optics systems allow one to estimate the point spread function (PSF) during the science observation. Using data from the wave-front sensor (WFS), a direct estimation of the averaged parallel phase structure and an estimation of the noise on the measurements are provided. The averaged orthogonal phase structure (not seen by the system), and the aliasing covariance are estimated using an end-to-end AO simulation. Finally, the estimated PSF is reconstructed using the algorithm of Veran et al. (1997). 1 However, this reconstruction is non perfect. Several approximations are done (stationary resudual phase, gaussian phase, simulated aliasing, etc...) and can impact the optical transfer function (OTF) in the case of a rather poor correction. Our aim is to give an error budget for the whole PSF reconstruction process and to link this PSF reconstruction with a deconvolution algorithm that take into account this PSF variability. Indeed, a myopic deconvolution algorithm can be feed with a priori on the object and the PSF. The latter can be obtained by studying the PSF reconstruction error budget as follows in this paper. Finally, this work will lead to an estimation of the error on the deconvolved image allowing one to perform an accurate astrometry/ photometry on the observed objects and to strengthen the contrast in the images. We concluded that to neglect the global cross­ term or to estimate the aliasing on the measurements using simulations has no effect on the PSF reconstruction.

Knowledge of the statistical characteristics of the Strehl ratio is essential for the performance assessment of the existing and future adaptive optics systems. For full assessment not only the mean value of the Strehl ratio but also higher statistical moments are important. Variance is related to the stability of an image and skewness reflects the chance to have in a set of short exposure images more or less images with the quality exceeding the mean. Skewness is a central parameter in the domain of lucky imaging. We present a rigorous theory for the calculation of the mean value, the variance and the skewness of the Strehl ratio. In our approach we represent the residual wavefront as being formed by independent cells. The level of the adaptive optics correction defines the number of the cells and the variance of the cells, which are the two main parameters of our theory. The deliverables are the values of the three moments as the functions of the correction level. We make no further assumptions except for the statistical independence of the cells.

We show experimental results demonstrating the feasibility of an extremely fast sequential phase-diversity (SPD) algorithm for point sources. The algorithm can be implemented on a typical adaptive optics (AO) system to improve the wavefront reconstruction beyond the capabilities of a wavefront sensor by using the information from the imaging camera. The algorithm is based on a small-phase approximation enabling fast numerical implementation, and it finds the optimal wavefront correction by iteratively updating the deformable mirror. Our experiments were made at an AO-setup with a 37 actuator membrane mirror, and the results show that the algorithm finds an optimal image quality in 5–10 iterations, when the initial wavefront errors are typical non-common path aberrations having a magnitude of 1–1.5 rad rms. The results are in excellent agreement with corresponding numerical simulations.

Direct imaging and spectroscopy can advance our understanding of planet formation and migration through the detection and characterization of extrasolar planets on wide orbits. Accurate photometry and astrometry of detected companions are of crucial importance to derive the planet physical properties.We present an extension of the Locally optimized combination of images (LOCI) method to measure the highest-fidelity photometry as well as accurate astrometry of detected companions. This algorithm is also generalized to Integral-Field Spectrograph (IFS) data processing, giving advantages of a simultaneous angular and spectral differential imaging reduction, retrieving high-fidelity spectra from PSF-subtracted cubes.

A 40 meters class telescope does require adaptive optics to provide few milli arcseconds resolution images. In the current design of the E-ELT, M4 provides adaptive correction and has also to cancel part of telescope wind shaking and static aberrations. The 2.4 meters adaptive mirror will provide as well Nasmyth focus selection. We will present the main design drivers and the main specifications quaternary mirror will have to meet. We will discuss what the challenges are in term of stability and performance of the associated key technologies. We will finally describe the current baseline design and the required schedule and work plan to adequately manufacture the E-ELT quartenary mirror.

We report in this paper on the progress of numerical modeling and simulation studies of the M4 adaptive mirror, a representative of the "adaptive secondary mirrors" technology, for the European Extremely Large Telescope (E-ELT). This is based on both dedicated routines and the existing code of the Software Package CADS. The points approached are basically the specific problems encountered with this particular type of voice-coil adaptive mirrors on the E-ELT: (*) the segmentation of the adaptive mirror, implying a fitting error due also to the edges of its six petals, as well as possible co-phasing problems to be evaluated in terms of interaction with the wavefront sensor (a pyramid here); (**) the necessary presence of "master" and "slave" actuators which management, in terms of wavefront reconstruction, implies to consider different strategies. The on-going work being performed for the two above points is described in details, and some preliminary results are given.

In this paper we will describe the chopping capabilities of the Large Binocular Telescope adaptive secondary mirrors. The chopping testing procedure has been implemented at the Arcetri Test Tower in Florence, Italy, together with the optical testing set-up. The deformable mirror static figuring error, after the flattening calibration at both chopping positions (± 25 μm tilt with respect to the nominal position), is measured to be compatible to the figuring at the zero tilt position, i.e. 30 nm RMS. The figuring error measured at a +25 μm tilted position, while the mirror was chopping at 10Hz, is within requirements for seeing limited mode observations.

We have developed a new type of unimorph deformable mirror for the correction of low-order Zernike modes. The mirror features a clear aperture of 50 mm combined with large peak-to-valley amplitudes of up to 35 μm. Newly developed fabrication processes allow the use of prefabricated, coated, super-polished glass substrates. The mirror's unique features suggest the use in several astronomical applications like the compensation of atmospheric aberrations seen by laser beacons and the use in woofer-tweeter systems. Additionally, the design enables an efficient correction of the inevitable wave-front error imposed by the floppy structure of primary mirrors in future large space telescopes. We have modeled the mirror by using analytical as well as finite element models. We will present design, key features and manufacturing steps of the deformable mirror.

We characterize the performance of deformable mirrors for use in open-loop regimes. This is especially relevant for Multi Object Adaptive Optics (MOAO), or for closed-loop schemes that require improved accuracies. Deformable mirrors are usually characterized by standard parameters, such as influence functions, linearity, hysteresis, etc. We show that these parameters are insufficient for characterizing open-loop performance and that a deeper analysis of the mirror's behavior is then required. The measurements on the deformable mirrors were performed in 2007 on the AO test bench of the Meudon observatory, SESAME.

High-energy beams of X-rays used in studies of molecular structure typically have imperfect wavefront quality. Improved point-spread functions can in principle be made by adjustment of a deformable mirror (DM) in the beam train. Conventional DMs are unsuitable because they are not intended for use at the necessary grazing incidence angles, and the optical surface is not sufficiently stable. We describe the conceptual design for a new DM that addresses the requirements of this application. Our design draws on successful strategies employed in the adaptive secondary mirrors at the MMT and LBT telescopes, including the use of voice-coil actuators with collocated capacitive position sensors.

One of the first ELT AO systems to be deployed will be NFIRAOS of the Thirty Meter Telescope (TMT). NFIRAOS is currently being designed at the National Research Council of Canada's Herzberg Institute of Astrophysics (HIA). NFIRAOS incorporates deformable mirrors with much larger number of actuators than in current AO systems. To aid the procurement of electronics for NFIRAOS DMs, a reference design is under way at the HIA. We have designed the overall architecture, defined a command communication interface and developed a compact and cost-efficient high voltage amplifier suitable for duplicating in 7673 copies for driving the two NFIRAOS DMs.

Micro-Electro-Mechanical Systems (MEMS) deformable mirrors (DMs) are widely utilized in astronomical Adaptive Optics (AO) instrumentation. High precision open-loop control of MEMS DMs has been achieved by developing a high accuracy DM model, the Fast Iterative Algorithm (FIA), a physics-based model allowing precise control of the DM shape. Accurate open-loop control is particularly critical for the wavefront control of High- Contrast Imaging (HCI) instruments to create a dark hole area free of most slow and quasi-static speckles which remain the limiting factor for direct detection and imaging of exoplanets. The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system is one of these high contrast imaging instruments and uses a 1024-actuator MEMS deformable mirror (DM) both in closed-loop and open-loop. The DM is used to modulate speckles in order to distinguish (i) speckles due to static and slow-varying residual aberrations from (ii) speckles due to genuine structures, such as exoplanets. The FIA has been fully integrated into the SCExAO wavefront control software and we report the FIA’s performance for the control of speckles in the focal plane.

We present the study and results on automatic tuning and optimizing the closed-loop control gains of the Proportional Integral (PI) controller for the high-order adaptive optics (HOAO) system. The Ziegler-Nichols frequency response (ZNfr) method is examined using the Nyquist stability criterion to implement the automatic tuning of PI controller by determining the ultimate gain, Ku, and ultimate period, Tu, of a process model, which consists of components from adaptive optics (AO) system. The maximum magnitude criterion, 0.5 dB 2.3, is identified and considered as the optimization method, which also established the stability of the PI controller. MATLAB scripts are developed to execute iterative calculation of control algorithm, which automates real-time simulation of the Simulink high-order adaptive optics (Sim-HOAO) models. Simulink block diagrams are used to represent transfer functions, which described the frequency-domain behavior of the AO system.

The detector controller requirements for Adaptive Optics (AO) cameras presents numerous challenges in the design of the electronics, all of which have led to highly customized controller development in order to meet the requirements of high frame rate, low-noise and low image latency in a compact sized camera. This paper presents an overview of the ESO AOWFS camera and AONGC, the Adaptive Optics ESO's new detector controller; the challenges and excellent progress in achieving detector limited performance from the e2v EMCCD CCD220, along with test results demonstrating sub-electron read noise at frame rates in excess of 1500 Hz. Pre-series cameras have been delivered for use in 2nd Generation VLT instruments (AOF and SPHERE).

In this paper we present the integration status of the ARGOS wavefront sensor and the results of the closed loop tests performed in laboratory. ARGOS is the laser guide star adaptive optics system of the Large Binocular Telescope. It is designed to implement a Ground Layer Adaptive Optics correction for LUCI, an infrared imaging camera and multi-object spectrograph, using 3 pulsed Rayleigh beacons focused at 12km altitude. The WFS is configured as a Shack-Hartman sensor having a 15 x 15 subaspertures over the telescope pupil. In the WFS each LGS is independently stabilized for on-sky jitter and range-gated to reduce spot elongation. The 3 LGS are arranged on a single lenslet array and detector by the use of off-axis optics in the final part of the WFS. The units of WFS are in the integration and testing phase at Arcetri Observatory premises. We describe here the test aimed to demonstrate the functionality of the WFS in an adaptive optics closed loop performed using the internal light sources of the WFS and a MEMS deformable mirror.

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.

The devices and components of adaptive optical system ANGARA, which is developed for image correction in the Big solar vacuum telescope (BSVT) at Baykal astrophysical observatory are described. It is shown that the use of modernized adaptive system on BSVT not only reduces the turbulent atmospheric distortions of image, but also gives a possibility to improve the telescope developing new methods of solar observations. A high precision Shack-Hartmann wavefront (WF) sensor has been developed on the basis of a low-aperture off-axis diffraction lens array. The device is capable of measuring WF slopes at array sub-apertures of size 640X640 μm with an error not exceeding 4.80 arc.sec. Also the modification of this sensor for adaptive system of solar telescope using extended scenes as tracking objects, such as sunspot, pores, solar granulation and limb, is presented. The software package developed for the proposed WF sensors includes three algorithms of local WF slopes estimation (modified centroids, normalized cross-correlation and fast Fourier-demodulation), as well as three methods of WF reconstruction (modal Zernike polynomials expansion, deformable mirror response functions expansion and phase unwrapping), that can be selected during operation with accordance to the application.

LINC-NIRVANA is the Fizeau beam combiner for the LBT, with the aim to retrieve the sensitivity of a 12m telescope and the spatial resolution of a 22.8m one. Despite being only one of the four wavefront sensors of a layer-oriented MCAO system, the GWS, which is retrieving the deformation introduced by the lower atmosphere, known to be the main aberration source, reveals a noticeable internal opto-mechanical complexity. The presence of 12 small devices used to select up to the same number of NGSs, with 3 optical components each, moving in a wide annular 2'-6' arcmin Field of View and sending the light to a common pupil re-imager, and the need to obtain and keep a very good super-imposition of the pupil images on the CCD camera, led to an overall alignment procedure in which more than a hundred of degrees of freedom have to be contemporary adjusted. The rotation of the entire WFS to compensate for the sky movement, moreover, introduces a further difficulty both in the alignment and in ensuring the required pupil superposition stability. A detailed description of the alignment procedure is presented here, together with the lessons learned managing the complexity of such a WFS, which led to considerations regarding future instruments, like a possible review of numerical versus optical co-add approach, above all if close to zero read-out noise detectors will be soon available. Nevertheless, the GWS AIV has been carried out and the system will be soon mounted at LBT to perform what is called the Pathfinder experiment, which consists in ground-layer correction, taking advantage of the Adaptive Secondary deformable Mirror.

LINC-NIRVANA is a near infrared interferometric imager with a pair of layer-oriented multi-conjugate adaptive optics systems (ground layer and high layer) for the Large Binocular Telescope. To prepare for the commissioning of LINC-NIRVANA, we have integrated the high layer wavefront sensor and its associated deformable mirror (a Xinetics-349) in a laboratory, located at Max Planck Institute for Astronomy, in Heidelberg, Germany. Together with a telescope simulator, which includes a rotating field and phase screens that introduce the effects of the atmosphere, we tested the acquisition of multiple guide stars, calibrating the system with the push-pull method, and characterizing the wavefront sensor together with the deformable mirror. We have closed the AO loop with up to 200 Zernike modes and with multiple guide stars. The AO correction demonstrated that uniform correction can be achieved in a large field of view. We report the current status and results of the experiment.

A new technique for high resolution wavefront sensing has been introduced. It is based on the Optical Differentiation wavefront sensor, however its application has required the development of a diffractive element that provides four or five copies of the original wavefront. It some aspect the result is similar to that provide by the Pyramid sensor although from a theoretical point of view is more close to the Modified Hartmann sensor. Here we introduce the theoretical background and principles along with an example of phase derivative estimate based on a computer simulation. The technique looks very promising since it is simple, with high resolution, without moving parts and allows us an easy post processing to recover Zernike coefficients. Nevertheless, a lot of work has to be completed to a proper evaluation of its actual capabilities, noise, resolution, etc.

The pyramid wavefront sensor is an innovative device with the special characteristics of variable gain and adjustable sampling in real time to enable an optimum match of the system performance, which make it an attractive option for next generation adaptive optics system compared with the Shack-Hartmann. At present most of the pyramid wavefront sensor are used with modulation based on oscillating optical component in order to give a linear measurement of the local tilt, but the PWFS without modulation would greatly simplify the optical and mechanical design of the adaptive optics system and also give highest sensitivity as expected to be achieved. In this paper we describe the optical setup of our adaptive optics system with nonmudulated pyramid wavefront sensor. In this system, the pyramid wavefront sensor with 8×8 sub-apertures in the pupil diameter has been designed, and the deformable mirror with 61 actuators based on the liquid-crystal spatial light modulator is used to introduce aberrations into the system, as well as to correct them afterwards. The closed-loop correction results of single order Zernike aberrations and the Kolmogorov turbulence phase screen are given to show that the PWFS without modulation can work as expected for closed-loop system.

The Zernike phase contrast sensor has been studied in the framework of the Active Phasing Experiment in the laboratory and on sky at the Very Large Telescope. Atmospheric turbulence strongly affects the shape of the signal of the Zernike phase contrast sensor. The first part of these proceedings is dedicated to a study of the influence of atmospheric turbulence on the signal of the Zernike phase contrast sensor. The second part is dedicated to the phasing of segmented deformable mirrors. A new technology of segmented deformable mirrors for adaptive optics made from silicon wafers with bimorph piezoelectric actuation has been proven to work. A demonstrator with three hexagonal segments of 90 mm corner to corner has been built. The morphing capability of the segmented mirror has been studied and validated by simulations and on a test bench. In this paper, we demonstrate with simulations the phasing of the segmented bimorph mirror with the Zernike phase contrast method. Aspects such as phasing in the presence of segment aberrations have been investigated.

A novel and very simple technique has been developed for extracting absolute phase maps from laboratory Fizeau interferometers, and that technique is generalized here to applications in interferometry and adaptive optics. In the original implementation, the phase maps considered were those produced by an interferometer measuring the surface of a high-precision flat mirror. The phase or surface shape measured in such a configuration is known only with respect to the phase map of the interferometer's transmission flat, and so contains substantial errors when precise surfaces are being tested. By making two additional measurements with small lateral shifts of the surface under test, and differencing these, maps of absolute phase differences between neighboring points on the test surface can be made. From these, standard wavefront reconstruction can recover an absolute phase map. Examples of the technique are considered here, including a novel diagnostic of common-path errors in adaptive optics systems. For an architecture in which the common path and the wavefront-sensor path can be adjusted in relative shear, it is possible to apply the requisite transverse shifts and so derive an absolute phase map isolating embedded portions of the system optics.

A Shack-Hartmann wavefront sensor samples the wavefront in the pupil. The wavefront shape will be undersam­ pled, since although the wavefront average spatial spectrum is a rapidly decreasing function of spatial frequency, it contains frequencies higher than the Nyquist limit : this well-known phenomenon is known as aliasing. The impact of aliasing in adaptive optics is difficult to estimate. Some methods have been proposed, that aim at optically filter out high wavefront frequencies ; some authors gave an estimate of this error, but most of the time these estimations are based on Monte-Carlo simulations of wavefront sensor. We propose in this paper an analytical study of the aliasing effect, and study how the aliasing error distributes over temporal frequencies. An analytical expression of the temporal spectrum of the aliasing error maybe of importance for system modeling or performance prediction in adaptive optics.

A new image-based technique for measuring the complex field in the pupil of a telescope is presented. The simplest form of the method uses two point source images, one with a small modification introduced in the pupil. The processing of the images is very simple and non-iterative. The method is based on a specially-defined complex functional derivative of the OTF. This derivative is approximated empirically by the difference between the Fourier transforms of the two PSFs: the differential OTF or "dOTF." Due to the complex conjugate in the OTF, the dOTF includes two complex images of the complex pupil field overlapping at the point of pupil modification. By placing the modification near the edge of the pupil, the overlap region can be minimized. The overlap region is typically small, but can be eliminated altogether by using a second modification and a third image. The technique can use broadband light, but the result incurs a radial blurring proportional to the fractional bandwidth. This is also easily dealt with using another modification and image. Although the dOTF a poor match for high frame rate astronomical AO applications, it has many potential uses. Optical shop testing, non-common-path wavefront error estimation, alignment and vignetting, telescope segment phasing, general imaging system diagnostics and testing applications are considered. More advanced applications are possible with extensions to the theory, such as extended incoherence background scenes as sources instead of stars, and 3-D tomographic aberration and transmission mapping open up many new applications.

A new method to estimate the complex pupil-plane field from a functional derivative of the optical transfer function (OTF) has been described by Codona.1 It is in principle a diversity technique that uses two focal-plane images with a spatially localized difference introduced in the pupil. The difference can be in phase, amplitude, or both, and need not be well known provided that its spatial extent is small compared to the required resolution of the field. Unlike other diversity methods, however, the dOTF wavefront estimation algorithm is non-iterative and very fast. The technique may be exploited in a straightforward way for tomographic wavefront sensing from a random scene of unresolved sources whose angular extent exceeds the isoplanatic limit. A single camera is arranged to capture the whole scene. An exposure is recorded, a modification is made to the pupil, and a second exposure recorded. These two images are then sufficient to derive the 3D information to characterize the non-shift-invariant point-spread function over the full field. While offering nothing revolutionary in tomography, the technique is a simple way to characterize the aberrations in an optical system and localize them along the optical axis.

dOTF is an image-based non-iterative technique for measuring the complex pupil field. The technique relies on the difference between two PSF images when a small modification is introduced near the pupil's edge. The nature of the modification is of minor importance and can consist of a transmission blockage or a phase shift introduced by poking a single DM actuator. Even without calibration, dOTF yields an accurate estimate of the complex amplitude over the pupil plane. We experimentally evaluate the technique in several different optical systems, using both transmission and phase modifications to the pupil, monochromatic and broadband light sources, and different modification areas and poke depths.

We evaluate the performance of existing wavefront sensing and control techniques, including speckle nulling and electric field conjugation, and discuss their applicability to high-contrast imaging spectrographs such as the Gemini Planet Imager (GPI). These techniques can be highly useful in correcting system phase errors, and can potentially improve instrument operating efficiency by working in conjunction with the dedicated adaptive optics (AO) wavefront sensor. We discuss the specifics of our implementation of speckle suppression for GPI and present lab demonstrations with average contrast improvements from 5.7x10^-6 to 1.03x10^-6.

We propose a new approach for the joint estimation of aberration parameters and unknown object from diversity images with applications in imaging systems with extended objects as astronomical ground-based observations or solar telescopes. The motivation behind our idea is to decrease the computational complexity of the conventional phase diversity (PD) algorithm and avoid the convergence to local minima due to the use of nonlinear estimation algorithms. Our approach is able to give a good starting point for an iterative algorithm or it can be used as a new wavefront estimation method. When the wavefront aberrations are small, the wavefront can be approximated with a linear term which leads to a quadratic point-spread function (PSF) in the aberration parameters. The presented approach involves recording two or more diversity images and, based on the before mentioned approximation estimates the aberration parameters and the object by solving a system of bilinear equations, which is obtained by subtracting from each diversity image the focal plane image. Moreover, using the quadratic PSFs gives improved performance to the conventional PD algorithm through the fact that the gradients of the PSFs have simple analytical formulas.

In this paper we give a new wavefront estimation technique that overcomes the main disadvantages of the phase diversity (PD) algorithms, namely the large computational complexity and the fact that the solutions can get stuck in a local minima. Our approach gives a good starting point for an iterative algorithm based on solving a linear system, but it can also be used as a new wavefront estimation method. The method is based on the Born approximation of the wavefront for small phase aberrations which leads to a quadratic point-spread function (PSF), and it requires two diversity images. First we take the differences between the focal plane image and each of the two diversity images, and then we eliminate the constant object, element-wise, from the two equations. The result is an overdetermined set of linear equations for which we give three solutions using linear least squares (LS), truncated total least squares (TTLS) and bounded data uncertainty (BDU). The last two approaches are suited when considering measurements affected by noise. Simulation results show that the estimation is faster than conventional PD algorithms.

Phase-diversity methods allow to estimate both the wavefront disturbance as well as the object that is being imaged and that is extended in space. Hence, in principle, phase-diversity methods can be used for wavefront sensing as well, without the need to spill part of the observed light to wavefront sensing with a dedicated wavefront sensor. However, the use of phase-diversity in real-time applications is prevented by its high computational complexity, determined by the number of parameters quantifying the wavefront and the object. To reduce the computational complexity, metrics have been proposed that are independent of the object, that allow to only estimate the wavefront, but still yield a nonlinear inverse problem. To further reduce the computational complexity of the wavefront estimation methods we consider linear approximations of these metrics, that allow to update the estimate of the wavefront by solving a linear least squares problem. We study the estimation error w.r.t. the presence of noise and the spectral content of the extended object, and compare metrics presented in literature.

P1640 calibrator is a wavefront sensor working with the P1640 coronagraph and the Palomar 3000 actuator adaptive optics system (P3K) at the Palomar 200 inch Hale telescope. It measures the wavefront by interfering post-coronagraph light with a reference beam formed by low-pass filtering the blocked light from the coronagraph focal plane mask. The P1640 instrument has a similar architecture to the Gemini Planet Imager (GPI) and its performance is currently limited by the quasi-static speckles due to non-common path wavefront errors, which comes from the non-common path for the light to arrive at the AO wavefront sensor and the coronagraph mask. By measuring the wavefront after the coronagraph mask, the non-common path wavefront error can be estimated and corrected by feeding back the error signal to the deformable mirror (DM) of the P3K AO system. Here, we present a first order wavefront estimation algorithm and an instrument calibration scheme used in experiments done recently at Palomar observatory. We calibrate the P1640 calibrator by measuring its responses to poking DM actuators with a sparse checkerboard pattern at different amplitudes. The calibration yields a complex normalization factor for wavefront estimation and establishes the registration of the DM actuators at the pupil camera of the P1640 calibrator, necessary for wavefront correction. Improvement of imaging quality after feeding back the wavefront correction to the AO system demonstrated the efficacy of the algorithm.

In MCAO the correction of the wavefront for an extended Field of View is obtained at the expense of a stretching of the actual instantaneous meta-pupils over the high altitude layers, just to compensate their average curvature. While this effect does average out in long term exposures and is of secondary interest in compensated imaging, it gives the input for the idea of using MCAO-like information, collectable over a certain Field of View, to assess in a time resolved mode (not necessarily in real time) the actual geometrical light throughput in a given direction. In principle this would allow, with proper time tagging, to achieve high precision photometry, as part of the scintillation could be measured on line during the observation. Simple averaging of neighbor stars to flat field starlight, for example, represents the equivalent of this concept for the ground-layer correction only. It can be seen that, once a direction is defined, it is relevant only the derivative of the wavefront around or in the proximity of that edges, but the range at which this happen is a crucial parameter. However, the strong interest in high precision measurements of exoplanetary transits or asteroseismology could make this approach not as lunatic as it could sound. view