This PDF file contains the front matter associated with SPIE Proceedings Volume 7015, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

High angular resolution imaging with adaptive optics (AO) has allowed significant progress in the study of disks and companions around stars over the past decades. This technique is also expected to lead to major breakthroughs in the next 10 years. We review the results obtained so far with AO and their impact on the understanding of how planetary systems form and evolve.

The W. M. Keck Observatory is designing a new adaptive optics system providing precision AO correction in the near infrared, good correction at visible wavelengths, and multiplexed spatially resolved spectroscopy. We discuss science cases for this Next Generation AO (NGAO), and show how the system requirements were derived from these science cases. Key science drivers include asteroid companions, planets around low-mass stars, general relativistic effects around the Galactic Center black hole, nearby active galactic nuclei, and high-redshift galaxies (including galaxies lensed by intervening galaxies or clusters). The multi-object AO-corrected integral field spectrograph will be optimized for high-redshift galaxy science.

The recent advent of laser guide star adaptive optics (LGS AO) on the largest ground-based telescopes has enabled a wide range of high angular resolution science, previously infeasible from ground- and/or space-based observatories. As a result, scientific productivity with LGS has seen enormous growth in the last few years, with a factor of ~10 leap in publication rate compared to the first decade of operation. Of the 54 refereed science papers to date from LGS AO, half have been published in the last ~2 years, and these LGS results have already made a significant impact in a number of areas. At the same time, science with LGS AO can be considered in its infancy, as astronomers and instrumentalists are only begining to understand its efficacy for measurements such as photometry, astrometry, companion detection, and quantitative morphology. We examine the science impact of LGS AO in the last few years of operations, largely due to the new system on the Keck II 10-meter telescope. We review currently achieved data quality, including results from our own ongoing brown dwarf survey with Keck LGS. We assess current and near-future performance with a critical eye to LGS AO's capabilities and deficiencies. From both qualitative and quantitative considerations, it is clear that the era of regular and important science from LGS AO has arrived.

We discuss the limits of ground-based astrometry with adaptive optics based on experiments using the core of the Galactic globular cluster M5. We have recently achieved ⪅ 100microarcsecond astrometric precision and accuracy at the Hale 200-inch telescope. Here we apply the same experimental design considerations and optimal estimation technique to explore the astrometric precision of the Keck II telescope. We find that high-precision astrometry at ≈ 50 microarcsecond level is possible at Keck in 20 seconds. We discuss the potential of differential astrometry for current and next generation large aperture telescopes based on these results.

We have demonstrated MOAO-type atmospheric compensation on a 10 meter telescope at visible wavelengths with the UCO/Lick MCAO/MOAO testbed in the Laboratory for Adaptive Optics at UCSC. We report Strehls of ~20% in R band (658 nm) on-axis and Strehls of ~15% off-axis 25" for a 3D Mauna Kea-type atmosphere with r0 = 15 cm and &Tgr;₀ = 3.5". We show that a tomographic MOAO approach with 5 LGS's in a 50" constellation is sufficient to realize good correction in the visible. Two major improvements to the testbed realized this gain: (1) An upgrade to 64x64 subapertures across a 10 meter pupil (2) and a predictor-corrector wind model. We discuss limitations to wide-field visible light AO on 8-10 meter class telescopes and stress that the tomographic error due to blind modes is frequently the largest field-dependent error. We use a predictor-corrector wind model (Wiberg et al. 2006) to take advantage of windlayer shearing in the atmosphere to reduce the tomographic error over a 50" diameter field. Depending on the validity of the Taylor frozen flow model for individual layers in the real atmosphere, this approach could be more effective than increasing the number of LGS's.

EAGLE is a multi-object 3D spectroscopy instrument currently under design for the 42-metre European Extremely Large Telescope (E-ELT). Precise requirements are still being developed, but it is clear that EAGLE will require (~100 x 100 actuator) adaptive optics correction of ~20 - 60 spectroscopic subfields distributed across a ~5 arcminute diameter field of view. It is very likely that LGS will be required to provide wavefront sensing with the necessary sky coverage. Two alternative adaptive optics implementations are being considered, one of which is Multi-Object Adaptive Optics (MOAO). In this scheme, wavefront tomography is performed using a set of LGS and NGS in either a completely open-loop manner, or in a configuration that is only closed-loop with respect to only one DM, probably the adaptive M4 of the E-ELT. The fine wavefront correction required for each subfield is then applied in a completely open-loop fashion by independent DMs within each separate optical relay. The novelty of this scheme is such that on-sky demonstration is required prior to final construction of an E-ELT instrument. The CANARY project will implement a single channel of an MOAO system on the 4.2m William Herschel Telescope. This will be a comprehensive demonstration, which will be phased to include pure NGS, low-order NGS-LGS and high-order woofer-tweeter NGS-LGS configurations. The LGSs used for these demonstrations will be Rayleigh systems, where the variable range-gate height and extension can be used to simulate many of the LGS effects on the E-ELT. We describe the requirements for the various phases of MOAO demonstration, the corresponding CANARY configurations and capabilities and the current conceptual designs of the various subsystems.

The Multi-Conjugate Adaptive Optics Demonstrator (MAD) built by ESO with the contribution of two external consortia is a powerful test bench for proving the feasibility of Multi-Conjugate (MCAO) and Ground Layer Adaptive Optics (GLAO) techniques both in the laboratory and on the sky. MAD is based on a two deformable mirrors correction system and on two multi-reference wavefront sensors (Star Oriented and Layer Oriented) capable to observe simultaneously some pre-selected configurations of Natural Guide Stars. MAD corrects up to 2 arcmin field of view in K band. After a long laboratory test phase, it has been installed at the VLT and it successfully performed on-sky demonstration runs on several astronomical targets for evaluating the correction performance under different atmospheric turbulence conditions. In this paper we present the results obtained on the sky in Star Oriented mode for MCAO and GLAO configurations and we correlate them with different atmospheric turbulence parameters. Finally we compare some of the on-sky results with numerical simulations including real turbulence profile measured at the moment of the observations.

The Lick Observatory is pursuing new technologies for adaptive optics that will enable feasible low cost laser guidestar systems for visible wavelength astronomy. The Villages system, commissioned at the 40 inch Nickel Telescope this past Fall, serves as an on-sky testbed for new deformable mirror technology (high-actuator count MEMS devices), open-loop wavefront sensing and control, pyramid wavefront sensing, and laser uplink correction. We describe the goals of our experiments and present the early on-sky results of AO closed-loop and open-loop operation. We will also report on our plans for on-sky tests of the direct-phase measuring pyramid-lenslet wavefront sensor and plans for installing a laser guidestar system.

The Victoria Open Loop Testbed (VOLT) serves as a demonstration of open loop control both on-sky (at the Dominion Astrophysical Observatory's 1.2m telescope) and in the lab in order to facilitate the future development of Multi-Object Adaptive Optics (MOAO). MOAO, when combined with multiple deployable integral field units, is a concept which promises to deliver near diffraction-limited images over a large field of view. Astronomers will be able to use the multiplex advantage of MOAO instruments to mount large, detailed surveys of galaxies and star formation regions. However, several challenges await MOAO instrument designers. The greatest of these is implementing open loop control in an astronomical adaptive optics (AO) system. Almost all astronomical AO systems to date have used some form of closed loop control, in which the wavefront sensors (WFSs) measure a residual wavefront error after the deformable mirror (DM) has taken on its commanded shape. WFSs in an open loop system can be spatially separated from the DM, but doing so creates new challenges, some known and some unknown. Uncertainties springing from open loop control pose the greatest risk to the design of a MOAO instrument. To mitigate this risk, we have designed and built VOLT, a simple on-axis open loop adaptive optics system. We describe several sources of open loop error, and our measurements of their expected contribution to the VOLT performance. Finally we present observations of a bright star, showing that VOLT, operating in open loop, was able to significantly improve the image quality from 2.5 arcseconds to 0.5 arcseconds in I-band, consistent with our estimates of the wavefront errors. We also present the open loop rejection transfer function for VOLT based on both on-sky and lab measurements.

The Layer Oriented Wavefront Sensor for MAD has been used in the sky to achieve science. The preliminary results from a six night run and the perspectives in terms of achieved performances and projections of sky coverage for slightly more sophisticated system like the Multiple Field of View one are shown indicating that the sensor is keeping its promises.

In this paper we review the current status of work in the sodium guidestar laser arena from the perspective of an astronomical AO system developer and user. Sodium beacons provide the highest and most useful guidestars for the 8m and larger class telescopes, but unfortunately sodium lasers are expensive and difficult to build at high output powers. Here we present highlights of recent advancements in the laser technology. Perhaps most dramatic are the recent theoretical and experimental efforts leading to better understanding the physics of coupling the laser light to the upper altitude sodium for best return signal. In addition we will discuss the key issues which affect LGS AO system performance and their technology drivers, including: pulse format, guidestar elongation, crystal and fiber technology, and beam transport.

We describe a new, improved approach for sodium guide-star lasers for the correction of atmospheric aberrations in telescopes, which satisfies all current requirements for advanced pulse burst waveforms. It makes use of sum frequency generation (SFG) of two pulsed, Q-switched, injection mode-locked Nd:YAG lasers, resulting in a macro-micro pulse-burst output, optimized in power and bandwidth to maximize the fluorescence from the high altitude sodium layer. The approach is robust and power scalable and satisfies the requirements for Multi Conjugate Adaptive Optics (MCAO) for current and future telescopes, including extremely large ground telescopes (ELTs). It is also adaptable for advanced design options. Here we describe the approach in detail, the results from critical design verification experiments, the current status and plans for further work required to demonstrate a complete sodium guide-star laser.

Using a stable single frequency (Δυ < 1 MHz) cw fasor we have characterized the guide star radiance under several conditions, including routinely measuring the radiance at various launch powers and simultaneously illuminating the same spot with a second fasor with a range of different frequency separations. Making use of sodium's hyperfine energy diagram and allowed transitions it is shown that some transitions do not contribute to the radiance after a short time period thus greatly reducing the number of states whose populations need to be tracked in a simple rate equation model. An offshoot of this view is the importance of the pump source's spectral content for efficient sodium scattering. Accounting for atomic recoil, which causes atoms to be Doppler shifted out of resonance, we obtain model curves for photon return flux versus launch power for both linear and circular polarization, both agree with measurements; the only free parameter being the sodium column density on the single night both sets of data were taken. We attempted to measure the sodium velocity distribution due to recoil using two Fasors in a pump-probe arrangement. We have measured some subtle phenomena that this simple model does not explain and these will be discussed. These may imply the importance of understanding the collision rates for sodium atoms to re-equilibrate through velocity changing collisions, spin relaxation and coherent beam propagation under various atmospheric conditions.

We describe a Monte Carlo code that includes the effects and optical pumping, radiation pressure and magnetic fields on the interaction between a laser beam and a sodium atom in the mesosphere. The code is sufficiently general that it can calculate the return for different types of laser. We find that conventional theory overestimates saturation and does not include the effect of optical down-pumping, which significantly reduces the population of sodium atoms available for excitation. We compare the theoretical returns for two types of laser and predict significant enhancements to the photon return/watt can be achieved with tailored spectral and temporal formats.

Lockheed Martin Coherent Technologies has developed 20 W and 50 W commercial solid-state sodium beacon Guidestar Laser Systems (GLS) for the Keck I and Gemini South telescopes, respectively. This work represents a critical step toward addressing the need of the astronomical adaptive optics (AO) community, including multi-conjugate AO and AO tomography for future extremely large telescopes. This paper describes the status of GLS for the Keck I and Gemini South telescopes. The design and experimental results of the laser oscillators, amplifiers and sum-frequency generator will be discussed.

We present the CILAS "Piezo Array" technology for Deformable Mirrors (DMs). Its main technical advantages are high order, large stroke, large bandwidth, high optical quality and very low dependence to temperature and environment. This technology can lead, on one hand, to very high order (several thousands), small inter-actuator spacing (1 mm range) DMs and, on the other hand, to large aperture DMs (2.5 m range). Both are needed for next generation of instrumentation and Extremely Large Telescopes (ELTs). A second family of DMs used for astronomy is the "Bimorph" technology. This piezo technology also allowed to obtain very good results on the most famous telescopes in the world.

A new prototype adaptive deformable mirror for future AO-systems is presented that consists of a thin continuous membrane on which push-pull actuators impose out-of-plane displacements. Each actuator has ±10μm stroke, nanometer resolution and only mW's heat dissipation. The mirror's modular design makes the mechanics, electronics and control system extendable towards large numbers of actuators. Models of the mirror are derived that are validated using influence and transfer function measurements. First results of a prototype with 427 actuators are also presented.

Atmospheric turbulence compensation via adaptive optics (AO) will be essential for achieving most objectives of the TMT science case. The performance requirements for the initial implementation of the observatory's facility AO system include diffraction-limited performance in the near IR with 50 per cent sky coverage at the galactic pole. This capability will be achieved via an order 60x60 multi-conjugate AO system (NFIRAOS) with two deformable mirrors optically conjugate to ranges of 0 and 12 km, six high-order wavefront sensors observing laser guide stars in the mesospheric sodium layer, and up to three low-order, IR, natural guide star wavefront sensors located within each client instrument. The associated laser guide star facility (LGSF) will consist of 3 50W class, solid state, sum frequency lasers, conventional beam transport optics, and a launch telescope located behind the TMT secondary mirror. In this paper, we report on the progress made in designing, modeling, and validating these systems and their components over the last two years. This includes work on the overall layout and detailed opto-mechanical designs of NFIRAOS and the LGSF; reliable wavefront sensing methods for use with elongated and time-varying sodium laser guide stars; developing and validating a robust tip/tilt control architecture and its components; computationally efficient algorithms for very high order wavefront control; detailed AO system modeling and performance optimization incorporating all of these effects; and a range of supporting lab/field tests and component prototyping activities at TMT partners. Further details may be found in the additional papers on each of the above topics.

A 42 meters telescope does require adaptive optics to provide few milli arcseconds resolution images. In the current design of the E-ELT, M4 provides adaptive correction while M5 is the field stabilization mirror. Both mirrors have an essential role in the E-ELT telescope strategy since they do not only correct for atmospheric turbulence but have also to cancel part of telescope wind shaking and static aberrations. Both mirrors specifications have been defined to avoid requesting over constrained requirements in term of stroke, speed and guide stars magnitude. Technical specifications and technological issues are discussed in this article. Critical aspects and roadmap to assess the feasibility of such mirrors are outlined.

EAGLE is a wide FoV (5 arcmin diameter), multi-objects (at least 20) integral-field spectrograph (R>4000) for the E-ELT. The top level requirements are to concentrate 30 to 40 % of the photons collected by the E-ELT in a focal area of 75x75 mas² in H band. This leads to the selection of the Multi Object Adaptive Optics in order to deliver such a performance in a so-large FoV. In this paper, we present a detailed analysis of the error budget for an MOAO system in EAGLE. It is based on numerical simulation results. The budget is splitted in LGS and NGS contributions. The analysis leads to share the specifications between low spatial frequencies and high spatial frequencies in the wave-front errors. Finally a preliminary conceptual design of the MOAO system is deduced including 9 LGS for tomography and a 9000 actuator deformable mirror per channel.

The multi-conjugate adaptive optics module for the European Extremely Large Telescope has to provide a corrected field of medium to large size (up to 2 arcmin), over the baseline wavelength range 0.8-2.4 μm. The current design is characterized by two post-focal deformable mirrors, that complement the correction provided by the adaptive telescope; the wavefront sensing is performed by means of a high-order multiple laser guide star wavefront sensor and by a loworder natural guide star wavefront sensor. The present status of a two years study for the advanced conceptual design of this module is reported.

The Gemini Multi-Conjugate Adaptive Optics project was launched in April 1999 to become the Gemini South AO facility in Chile. The system includes 5 laser guide stars, 3 natural guide stars and 3 deformable mirrors optically conjugated at 0, 4.5 and 9km to achieve near-uniform atmospheric compensation over a 1 arc minute square field of view. Sub-contracted systems with vendors were started as early as October 2001 and were all delivered by July 2007, but for the 50W laser (due around September 2008). The in-house development began in January 2006, and is expected to be completed by the end of 2008 to continue with integration and testing (I&T) on the telescope. The on-sky commissioning phase is scheduled to start during the first half of 2009. In this general overview, we will first describe the status of each subsystem with their major requirements, risk areas and achieved performance. Next we will present our plan to complete the project by reviewing the remaining steps through I&T and commissioning on the telescope, both during day-time and at night-time. Finally, we will summarize some management activities like schedules, resources and conclude with some lessons learned.

The Magellan Clay telescope is a 6.5m Gregorian telescope located in southern Chile at Las Campanas Observatory. The Gregorian design allows for an adaptive secondary mirror that can be tested off-sky in a straight-forward manner. We have fabricated a 85 cm diameter aspheric adaptive secondary with our subcontractors and partners. This secondary has 585 actuators with <1 msec response times. The chopping adaptive secondary will allow low emissivity AO science. We will achieve very high Strehls (~98%) in the Mid-IR AO (8-26 microns) with the BLINC/MIRAC4 Mid-IR science camera. This will allow the first "super-resolution" and nulling Mid-IR studies of dusty southern objects. We will employ a high order (585 mode) pyramid wavefront sensor similar to that used in the Large Binocular Telescope AO systems. The relatively high actuator count will allow modest Strehls to be obtained in the visible (~0.8μm). Our visible light AO (Vis AO) science camera is fed by an advanced ADC and beamsplitter piggy-backed on the WFS optical table. The system science and performance requirements, and an overview the design, interface and schedule for the Magellan AO system are presented here.

Deployed as a multi-user shared facility on the 5.1 meter Hale Telescope at Palomar Observatory, the PALM-3000 highorder upgrade to the successful Palomar Adaptive Optics System will deliver extreme AO correction in the near-infrared, and diffraction-limited images down to visible wavelengths, using both natural and sodium laser guide stars. Wavefront control will be provided by two deformable mirrors, a 3368 active actuator woofer and 349 active actuator tweeter, controlled at up to 3 kHz using an innovative wavefront processor based on a cluster of 17 graphics processing units. A Shack-Hartmann wavefront sensor with selectable pupil sampling will provide high-order wavefront sensing, while an infrared tip/tilt sensor and visible truth wavefront sensor will provide low-order LGS control. Four back-end instruments are planned at first light: the PHARO near-infrared camera/spectrograph, the SWIFT visible light integral field spectrograph, Project 1640, a near-infrared coronagraphic integral field spectrograph, and 888Cam, a high-resolution visible light imager.

The current status and recent results, since last SPIE conference at Orlando in 2006, for the laser guide star adaptive optics system for Subaru Telescope is presented. We had a first light using natural guide star and succeed to launch the sodium laser beam in October 2006. The achieved Strehl ratio on the 10th magnitude star was around 0.5 at K band. We confirmed that the full-width-half-maximum of the stellar point spread function is smaller than 0.1 arcsec even at the 0.9 micrometer wavelehgth. The size of the artificial guide star by the laser beam tuned at the wavelength of 589 nm was estimated to be 10 arcsec. The obtained blurred artificial guide star is caused by the wavefront error on the laser launching telescope. After the first light and first launch, we found that we need to modify and to fix the components, which are temporarily finished. Also components, which were postponed to fabricate after the first light, are required to build newly. All components used by the natural guide star adaptive optics system are finalized recently and we are ready to go on the sky. Next engineering observation is scheduled in August, 2008.

W. M. Keck Observatory (WMKO) is currently engaged in the design of a powerful new Adaptive Optics (AO) science capability providing precision correction in the near-IR, good correction in the visible, and faint object multiplexed integral field spectroscopy. Improved sensitivity will result from significantly higher Strehl ratios over narrow fields (< 30" diameter) and from lower backgrounds. Quantitative astronomy will benefit from improved PSF stability and knowledge. Strehl ratios of 15 to 25% are expected at wavelengths as short as 750 nm. A multi-object AO approach will be taken for the correction of multiple science targets over modest fields of regard (< 2' diameter) and to achieve high sky coverage using AO compensated near-IR tip/tilt sensing. In this paper we present the conceptual design for this system including discussion of the requirements, system architecture, key design features, performance predictions and implementation plans.

The first of the two Gregorian Adaptive Secondary Mirror (ASM) units for the Large Binocular Telescope (LBT) has been fully integrated and tested for laboratory acceptance. The LBT unit represents the most advanced ASM device existing in hardware. The unit has 672 electro-magnetic force actuators to change the shape of the 1.6mm-thick and 911mm-diameter Zerodur shell. The actuators control the mirror figure using the position feedback from the internal metrology provided by co-located capacitive sensors. The on-board real-time control electronics has a parallel computational power of 163Gflop/s providing not only the internal control of the unit with a 72kHz loop but also the wavefront reconstruction for the 1kHz Adaptive Optics loop. The paper describes the final configuration of the system and reports the results of the characterization and optimization process together with the results of the laboratory acceptance tests.

Laser guide star adaptive optics and interferometry are currently revolutionizing ground-based near-IR astronomy, as demonstrated at various large telescopes. The Large Binocular Telescope from the beginning included adaptive optics in the telescope design. With the deformable secondary mirrors and a suite of instruments taking advantage of the AO capabilities, the LBT will play an important role in addressing major scientific questions. Extending from a natural guide star based system, towards a laser guide stars will multiply the number of targets that can be observed. In this paper we present the laser guide star and wavefront sensor program as currently being planned for the LBT. This program will provide a multi Rayleigh guide star constellation for wide field ground layer correction taking advantage of the multi object spectrograph and imager LUCIFER in a first step. The already foreseen upgrade path will deliver an on axis diffraction limited mode with LGS AO based on tomography or additional sodium guide stars to even further enhance the scientific use of the LBT including the interferometric capabilities.

CAMERA is an autonomous laser guide star adaptive optics system designed for small aperture telescopes. This system is intended to be mounted permanently on such a telescope to provide large amounts of flexibly scheduled observing time, delivering high angular resolution imagery in the visible and near infrared. The design employs a Shack Hartmann wavefront sensor, a 12x12 actuator MEMS device for high order wavefront compensation, and a solid state 355nm ND:YAG laser to generate a guide star. Commercial CCD and InGaAs detectors provide coverage in the visible and near infrared. CAMERA operates by selecting targets from a queue populated by users and executing these observations autonomously. This robotic system is targeted towards applications that are diffcult to address using classical observing strategies: surveys of very large target lists, recurrently scheduled observations, and rapid response followup of transient objects. This system has been designed and costed, and a lab testbed has been developed to evaluate key components and validate autonomous operations.

We discuss our Polychromatic Laser Guide Star (PLGS) end-to-end model which relies on the 2-photon excitation of sodium in the mesosphere. We then describe the status of the setup at Observatoire de Haute- Provence of ELP-OA, the (PLGS) concept demonstrator. The PLGS aims at measuring the tilt from the LGS without any NGS. Two dye laser chains locked at 589 and 569nm are required. These chains, are similar to those of our PASS-2 experiment at Pierrelatte (1999). The two oscillators, preamplifiers and amplifiers are pumped with NdYAGs. Both beams are phase modulated with a double sine function. If required, a third stage can be added. It is expected that beams will deliver an output average power of 34W each, so that 22W will be deposited into the mesosphere. If it is not enough, there is enough power supply to twofold it. These lasers are being settled in the building of the OHP 1.52m telescope, partly at the first floor, and partly at the top of the North pillar. Beams will propagate from there to the launch telescope attached to the 1.52m one through a train of mirrors fixed with respect to the beam, so that incident angles are constant. The coudé focus of the 1.52m telescope will be equipped with an adaptive optics device, closely derived from the ONERA's BOA one. The Strehl ratio at 330nm for the differential tilt measurement channel is expected to be 30-40% for r₀ = 8 - 10cm. Telescope vibrations will be measured with pendular seismometers upgraded from Tokovinin's prototype. The full demonstrator is planned to run in 2010.

The Gemini Planet Imager (GPI) is a facility instrument under construction for the 8-m Gemini South telescope. It combines a 1500 subaperture AO system using a MEMS deformable mirror, an apodized-pupil Lyot coronagraph, a high-accuracy IR interferometer calibration system, and a near-infrared integral field spectrograph to allow detection and characterization of self-luminous extrasolar planets at planet/star contrast ratios of 10-7. I will discuss the evolution from science requirements through modeling to the final detailed design, provide an overview of the subsystems and show models of the instrument's predicted performance.

In July 2008, a new integral field spectrograph and a diffraction limited, apodized-pupil Lyot coronagraph was installed behind the adaptive optics system at the Hale 200-inch telescope at Palomar. This instrument serves as the basis of a long-term observational program in high-contrast imaging. The technical goal is to utilize the spectral nature of speckle noise to overcome it. The coronagraph alone will achieve an initial dynamic range of 10-5 at 1", with first light in mid-2008, without speckle noise suppression. Initial work indicates that spectral speckle suppression will provide a factor of 10 to 100 improvement over this. Such sensitivity provides detection and low resolution spectra of young planets of several Jupiter masses around young stars within 25 pc. The spectrograph obtains 32 images across the J and H bands (1.05 - 1.75 &mgr;m), with a spectral resolution of 30-100. The image plane is subdivided by a 200 x 200 element micro-lenslet array with a plate scale of 21 mas per lenslet, diffraction-limited at 1.0 &mgr;m. Data is collected with a 2048 x 2048 pixel Rockwell Hawaii-II HgCdTe infrared detector cooled with liquid Nitrogen. This system is the first of a new generation of apodized pupil coronagraphs combined with high-order adaptive optics and integral field spectrographs.

While more than 200 extrasolar planets have been discovered using indirect techniques, the direct detection of this class of object has remained at the sensitivity limits of ground based observatories. The development of improved adaptive optics systems and high contrast instruments has increased the sensitivity to extrasolar planets. We present high contrast results from the OSIRIS infrared lenslet-based integral field spectrograph (IFS) operating behind the Keck II adaptive optics (AO) system. OSIRIS spatially samples the Keck PSF at the diffraction limit, while providing a spectral resolution of 3800 for each spaxel. The OSIRIS integral field sampling simultaneously monitors the PSF over a broad band (20%), and this sampling is used to identify and suppress speckle diffraction features. The high-contrast sensitivity of Keck II AO near-infrared IFS (OSIRIS) and near-infrared imager (NIRC2) are compared.

The detection and characterization of extrasolar planets with SPHERE (Spectro Polarimetric High contrast Exoplanet REsearch) is challenging and in particular relies on the ability of a coronagraph to attenuate the diffracted starlight. SPHERE includes 3 instruments, 2 of which can be operated simultaneously in the near IR from 0.95 to 1.8 microns. This requirements is extremely critical for coronagraphy. This paper briefly introduces the concepts of 2 coronagraphs, the Half-Wave Plate Four Quadrant Phase Masks and the Apodized Pupil Lyot Coronagraph, prototyped within the SPHERE consortium by LESIA (Observatory of Paris) and FIZEAU (University of Nice) respectively. Then, we present the measurements of contrast and sensitivity analysis. The comparison with technical specifications allows to validate the technology for manufacturing these coronagraphs.

The SPHERE (Spectro-Polarimetry High-contrast Exoplanet Research) instrument is an ESO project aiming at the direct detection of extra-solar planets. It should equip one of the four VLT 8-m telescopes in 2010. The heart of the SPHERE instrument is its eXtrem Adaptive Optics (XAO) SAXO (SPHERE AO for eXoplanet Observation) subsystem that should deal with a tight error budget. To fulfil SAXO challenging requirements a mixed control law has been designed. It includes both an optimized modal gain integrator to control the Deformable Mirror (DM) and a Linear Quadratic Gaussian (LQG) control law to manage the tip-tilt (TT) mirror and filter possible vibrations. A specific scheme has been developed to optimize the correction provided by the DM and the TT while minimizing the coupling between both control loops. Actuator saturation and wind-up effects management are described. We describe the overall control architecture and focus on these main issues. We present expectable performance and also consider the interactions of the main control loop with other subsystems. PUBLISHER'S NOTE Sept. 9, 2010: Due to a production error, SPIE Paper 70151U was inadvertently published also as SPIE Paper 70151D. This has been corrected. This record contains the correct citation, abstract, and manuscript for paper 70151D.

We have recently proposed Predictive Fourier Control, a computationally efficient and adaptive algorithm for predictive wavefront control that assumes frozen flow turbulence. We summarize refinements to the state-space model that allow operation with arbitrary computational delays and reduce the computational cost of solving for new control. We present initial atmospheric characterization using observations with Gemini North's Altair AO system. These observations, taken over 1 year, indicate that frozen flow is exists, contains substantial power, and is strongly detected 94% of the time.

We address the problem of proper handling of deformable mirror (DM) dynamics in Adaptive Optical (AO) systems. We develop a state-space approach based on a continuous stochastic model of the atmospheric turbulence, which yields a fully optimal minimum mean-square error (mmse) solution in the form of a discrete-time Linear-Quadratic-Gaussian (LQG) regulator design. This optimal approach provides a reference point for assessing the performance of simpler suboptimal solutions used up to now. We show the significance of taking into account the DM dynamics, in particular for the upcoming secondary deformables.

Voltage saturation mechanisms are always present on deformable mirrors (DMs) used in adaptive optics (AO) systems, so as to prevent possibly irreversible degradation of the DM. This may happen most often in a strong turbulence context, where too high voltage values are computed by control algorithms trying to compensate for high phase shifts. In minimum variance control, it is well known that input saturation in linear systems destroys separation, leading to untractable optimal control problems. We show that, in the absence of DM's dynamics, separation and certainty equivalence hold in AO even when saturations are present on the system. The optimal control can then be computed by solving a constrained projection problem. As this is computationally intensive, we also propose a sub-optimal control with lower computational burden, which guarantees optimal estimation of the turbulent phase. Optimal and suboptimal controls show a dramatic improvement in performance (measured by the Strehl ratio) compared with those obtained with integral controllers equipped with adequate clipping and anti-wind-up mechanisms. All simulation results are obtained in bad seeing conditions using a VLT Paranal type configuration.

Adaptive Optics systems under study for the Extremely Large Telescopes gave rise to a new generation of algorithms for both wavefront reconstruction and the control law. In the first place, the large number of controlled actuators impose the use of computationally efficient methods. Secondly, the performance criterion is no longer solely based on nulling residual measurements. Priors on turbulence must be inserted. In order to satisfy these two requirements, we suggested to associate the Fractal Iterative Method for the estimation step with an Internal Model Control. This combination has now been tested on an end-to-end adaptive optics numerical simulator at ESO, named Octopus. Results are presented here and performance of our method is compared to the classical Matrix-Vector Multiplication combined with a pure integrator. In the light of a theoretical analysis of our control algorithm, we investigate the influence of several errors contributions on our simulations. The reconstruction error varies with the signal-to-noise ratio but is limited by the use of priors. The ratio between the system loop delay and the wavefront coherence time also impacts on the reachable Strehl ratio. Whereas no instabilities are observed, correction quality is obviously affected at low flux, when subapertures extinctions are frequent. Last but not least, the simulations have demonstrated the robustness of the method with respect to sensor modeling errors and actuators misalignments.

A new wavefront sensing scheme derived from curvature wavefront sensing is presented. Non-linear Curvature wavefront sensing (NLCWFS) is a scheme derived from conventional curvature wavefront sensing. NLCWFS uses four defocused pupil images and a non-linear wavefront reconstruction. NLCWFS is largely achromatic and does not require a flat (<1 rad RMS) wavefront to operate: it is therefore very robust, and is an attractive alternative to less efficient Shack-Hartmann wavefront sensing. For low order aberrations, sensitivity gains corresponding to 5 and 8 stellar magnitudes can be achieved over the conventional Shack-Hartmann sensor on respectively a 8-m telescope and a 30-m telescope.

Laser guide star wavefront sensors (WFS) using pulsed lasers can benefit from dynamic refocusing techniques which synchronously adjust the focus of the wavefront as the light returns from the scattering layer so as to maintain a constant axial image location. Existing techniques involve pulsating discrete mirrors and high-speed segmented MEMS in the WFS path. A different approach is presented here, which uses a pair of rotating phase plates with cylindrical or Alvarezlens- style tracks near the WFS pupil. Rotational speeds and disk sizes similar to that used for compact disc operation are proposed. The plates can be manufactured by numerical machining of transparent plastic materials or as diffractive components.

The current projects of Extremely Large Telescopes rely on adaptive optics systems using several sodium laser guide stars (LGSs). Because of the thickness of the sodium layer in the mesosphere, the subapertures of a Shack-Hartmann wavefront sensor will see the LGS all the more elongated as its position is distant from the launching point of the laser. This effect is significant and prompts the lasers to be launched from behind the secondary instead of from around the telescope. The elongations increase the centroiding errors and new smarter algorithms have been designed to mitigate this effect, but the loss of accuracy is still significant. Further, the measurement uncertainties are no more uniform across the pupil and correlations are introduced between the two coordinates of the gradients. From numerical simulations, we analyze the benefit of taking into account this structured correlations in wavefront reconstruction algorithms and compare the reconstruction accuracy when using least squares, weighted least squares, or minimum variance using von Karman turbulence priors. For a single LGS launched behind the secondary, numerical simulations show effective improvements when using both noise correlations and priors in wavefront reconstruction. When combining the measurements from several LGSs in a Ground Layer adaptive optics system, we show that taking into account the noise covariances yields better reconstructions when LGSs are launched from around the telescope than from behind the secondary. Further, results indicate that we could discard the measurements along the elongated direction where this elongation is greater than a given threshold.

In the last years an increasing consideration has been given to the study of Laser Guide Stars (LGS) for the measurement of the disturbance introduced by the atmosphere. Due to the finite distance of the artificial reference source and its vertical extension (the Sodium layer occurs at approximately 90 km, with a vertical thickness of about 10 km), the source itself looks elongated, when observed from the edge of a large aperture. On a 40 m class telescope, for instance, the maximum elongation varies between 4 and 6 arcseconds, depending on the Sodium layer properties and on the launching position. This spot elongation strongly limits the performance of the most common wavefront sensors. A straightforward solution for a Shack-Hartmann wavefront sensor is to increase the laser power, in order to balance the loss of centroiding accuracy due to the elongation. This solution, although appealing in principle, presents drawbacks related, for instance, to the availability of very powerful lasers. We propose in this paper a wavefront sensor concept that provides an optical solution to the perspective elongation problem. It is based on an array of bi-prisms placed in the focal plane of a lenslet array; each bi-prism is aligned to the elongated spot produced by the corresponding lenslet; the spot is split into two beams, that are re-imaged into two micro-images of the sub-aperture itself; the difference in the integrated intensity of these two micro-images is proportional to the local wavefront slope. This method is sensitive only to the slope information in the direction locally orthogonal to the bi-prisms (and to the elongation) and the full information has to be recovered by combining the signals coming from different LGSs launched from different positions at the telescope edge. The pros and cons of this technique, in terms of hardware requirements and photon budget, are discussed in this paper.

The paper presents a new technique to improve the wavefront sensing process when LGSs are used. The technique starting point is to shrink to LGS projected spot by using a low order AO system located at the laser projector. This AO system is used to pre-correct the beam so that LGS spot on the sodium layer can have a diffraction limited FWHM. In this case the reconstruction error due to photon noise and so the laser power is reduced by the square of the ratio between the uncorrected and corrected projected spot FWHMs. The paper analyzes the LGS spot dimension as seen from the main telescope to quantify the final gain in the wavefront sensing process of the main AO system. The following analysis is done for a Shack Hartmann sensor with 16x16 subapertures and correcting for 210 modes and for a Pyramid Sensor (PS) having 32x32 subapertures and correcting for 666 modes. The achieved results in term of laser power gain ranges between 1.5-3 and between 3-6 for the SH and PS respectively. These gains are achieved at the expenses of making the laser projector adaptive. Finally some discussion of the impact achieved using the considered technique and gains is presented at the end of the paper.

The detector is a critical component of any Adaptive Optics WaveFront Sensing (AO WFS) system. The required performance combination of fast frame rate, high quantum efficiency, low read noise and dark signal, number and size (24-50 μm) of pixels pushes detector technology to the edge such that in many cases custom detector developments are required. This paper examines the roadmap of optical and infrared detectors by reviewing; detectors that are currently available and/or are in use in current instruments, detectors that are under development and will be used in future instruments on existing telescopes, and the requirements and status of new detectors whose development are critical for the success of the next generation of extremely large telescopes (E-ELT, GMT, and TMT). In addition, the paper will report on the AO WFS detector development and testing programs currently under way at ESO.

Presently, dedicated instrument developments at large telescopes (SPHERE for the VLT, GPI for Gemini) are about to discover and explore self-luminous giant planets by direct imaging and spectroscopy. The next generation of 30m-40m ground-based telescopes, the Extremely Large Telescopes (ELTs), have the potential to dramatically enlarge the discovery space towards older giant planets seen in reflected light and ultimately even a small number of rocky planets. EPICS is a proposed instrument for the European ELT, dedicated to the detection and characterization of expolanets by direct imaging and spectroscopy. ESO recently launched a phase-A study for EPICS with a large European consortium which - by simulations and demonstration experiments - will investigate state-of-the-art diffraction and speckle suppression techniques to deliver highest contrasts. The final result of the study in 2010 will be a conceptual design and a development plan for the instrument. Here we present first results from the phase-A study and discuss the main challenges and science capabilities of EPICS.

The Gemini Planet Imager (GPI) is a future high-order coronagraphic adaptive optics system optimized for the search and analysis of Jupiter-like exoplanets around nearby young 10-1000Myr stars. In this paper, an on-axis Fresnel wavefront propagation model of GPI is presented. The main goal of this work is to confirm that the current GPI design will reach its 10^-7 contrast requirement. The model, assembled using the PROPER IDL library, is used to properly simulate out-of-pupil-plane and finite size optics. A spectral data cube at GPI spectral resolution R=45 in H-band is obtained to estimate the GPI contrast as a function of wavelength. This cube is then used to evaluate the speckle suppression performance of the Simultaneous Spectral Differential Imaging (SSDI) technique. It is shown that GPI should achieve a photon noise limited 10^-7 contrast when using a simple SSDI post-processing on an H=5 star and a 1h observing sequence. Finally, a long exposure data cube is obtained by combining the speckle contributions of an average atmosphere and GPI optics. That final long-exposure contrast as a function of wavelength can be used to estimate the GPI exoplanet characterization accuracy, and to evaluate, using Monte-Carlo simulations, the expected exoplanet survey performance.

Extreme adaptive optics system (SAXO) is the heart of the SPHERE instrument which aims at directly detect and characterize giant extra-solar planets from the ground. It should equip one of the four VLT 8-m telescopes at the end of 2010. We present a detailed design and architecture of the SAXO system. We focus on each critical point that has been solved during the preliminary design phase. It concerns the adaptive optics system itself but also the interaction with other SPHERE subsystems (such as coronagraphy) and focal plane instrumentation (dual band imager, integral field spectroscopy and polarimetric imager). Acceptance and integration tests of SAXO are discussed. Finally, detailed performance of the whole system and comparison to the science requirements are provided.

We present the coronagraphic and adaptive optics performance of the Gemini-South Near-Infrared Coronagraphic Imager (NICI). NICI includes a dual-channel imager for simultaneous spectral difference imaging, a dedicated 85-element curvature adaptive optics system, and a built-in Lyot coronagraph. It is specifically designed to survey for and image large extra-solar gaseous planets on the Gemini Observatory 8-meter telescope in Chile. We present the on-sky performance of the individual subsystems along with the end-to-end contrast curve. These are compared to our model predictions for the adaptive optics system, the coronagraph, and the spectral difference imaging.

Performance of wave-front control and coronagraphy are very critical for high contrast imaging on an ELT. Quasi-static aberrations will have a dramatic impact on the detection performance for the most demanding science objectives of EPICS, the direct imaging of exo-planets. The contribution of these systematic errors will have to be significantly lower than the overall residual halo level due to turbulence correction residual after coronagraphy. We present preliminary results of the strategy to measure wave front errors after the coronagraph with the goal of minimizing common path errors for the correction of static speckles. The development of two novel post-coronagraphic wave-front sensors is given.

This paper describes the modeling effort undertaken to derive the wavefront error (WFE) budget for the Narrow Field Infrared Adaptive Optics System (NFIRAOS), which is the facility, laser guide star (LGS), dual-conjugate adaptive optics (AO) system for the Thirty Meter Telescope (TMT). The budget describes the expected performance of NFIRAOS at zenith, and has been decomposed into (i) first-order turbulence compensation terms (120 nm on-axis), (ii) opto-mechanical implementation errors (84 nm), (iii) AO component errors and higher-order effects (74 nm) and (iv) tip/tilt (TT) wavefront errors at 50% sky coverage at the galactic pole (61 nm) with natural guide star (NGS) tip/tilt/focus/astigmatism (TTFA) sensing in J band. A contingency of about 66 nm now exists to meet the observatory requirement document (ORD) total on-axis wavefront error of 187 nm, mainly on account of reduced TT errors due to updated windshake modeling and a low read-noise NGS wavefront sensor (WFS) detector. A detailed breakdown of each of these top-level terms is presented, together with a discussion on its evaluation using a mix of high-order zonal and low-order modal Monte Carlo simulations.

We use physical optics to simulate LGS propagation and imaging in a Shack-Hartmann wavefront sensor (WFS). We model different launch telescope (LT) sizes and realistic LT aberrations, the turbulent atmosphere, a sodium layer of finite thickness, the downlink propagation of the return light, an 8m-telescope, and finally the planned Very Large Telescope (VLT) Adaptive Optics Facility 40×40 GRAAL WFS. We study both long-exposure and instantaneous images on the WFS and compute spot size statistics. The results agree with observations obtained in the VLT telescope guider camera and enable us to optimize the LT diameter and devise design rules.

A multi-laser adaptive optics system, at the 6.5 m MMT telescope, has been undergoing commissioning in preparation for wide-field, partially corrected as well as narrow-field, diffraction limited science observations in the thermal and near infrared. After several delays due to bad weather, we have successfully closed the full high order ground-layer adaptive optics (GLAO) control loop for the first time in February 2008 using five Rayleigh laser guide stars and a single tilt star. Characterization and automated correction of static aberrations such as non-common path errors were addressed in May 2008. Calibration measurements in preparation for laser tomography adaptive optics (LTAO) operation are planned for the fall of 2008 along with the start of shared-risk GLAO science observations. We present the results of GLAO observations with the PISCES imager, a 1 - 2.5 &mgr;m camera with a field of view of 110 arc seconds. The status of the remaining GLAO commissioning work is also reviewed. Finally, we present plans for commissioning work to implement the LTAO operating mode of the system.

GLAS is an upgrade of the William Herschel Telescope's existing natural-guide-star (NGS) AO system NAOMI to incorporate a 20-W Rayleigh laser guide star (LGS) projected to an altitude of 15 km. It is currently being commissioned on-sky, and we review here the current status of the project. GLAS/NAOMI delivers dramatic improvements in PSF in both the near-IR (AO-corrected FWHM close to the diffraction limit, >~ 0.15 arcsec) and in the optical (factor of ~ 2 reduction in FWHM). The performance is similar to that with NGS, and is consistent with predictions from modelling. The main advantage over NGS AO is the large gain in sky coverage (from ~ 1% to ~ 100% at galactic latitude 40°). GLAS provides the first on-sky demonstration of closed-loop ground-layer AO (GLAO), and is the first Rayleigh LGS AO system to be offered for general use, at any telescope.

ESO has initiated in June 2004 a concept of Adaptive Optics Facility. One unit 8m telescope of the VLT is upgraded with a 1.1 m convex Deformable Secondary Mirror and an optimized instrument park. The AO modules GALACSI and GRAAL will provide GLAO and LTAO corrections forHawk-I and MUSE. A natural guide star mode is provided for commissioning and maintenance at the telescope. The facility is completed by a Laser Guide Star Facility launching 4 LGS from the telescope centerpiece used for the GLAO and LTAO wavefront sensing. A sophisticated test bench called ASSIST is being designed to allow an extensive testing and characterization phase of the DSM and its AO modules in Europe. Most sub-projects have entered the final design phase and the DSM has entered Manufacturing phase. First light is planned in the course of 2012 and the commissioning phases should be completed by 2013.

A laser guide star (LGS) adaptive optics (AO) system generally requires additional tip/tilt information derived using a natural guide star (NGS), while multi-LGS systems will benefit from measurement of additional low-order wavefront modes using one or more NGS's. If we use AO sharpened NGS's, we can improve both the measurement accuracy and accessible sky fraction while also minimizing the observational overhead of faint NGS acquisition. Multi-object adaptive optics (MOAO) sharpening of NGS is possible where a good estimate of the NGS wavefront can be made, for example where tomographic wavefront information is available. We describe a new approach for high Strehl ratio sharpening, based on additional patrolling laser beacons, to eliminate generalized anisoplanatism and minimize tomography error in the NGS direction.

Reliable prediction of the image quality delivered by a ground-layer AO (GLAO) system can be made using several methods, given the parameters of the instrument and the statistics of the turbulence profile above the observatory. Extensive data accumulated over several years at different sites indicate that GLAO can bring a significant gain in performance for classical astronomical observations, and at visible wavelengths. This gain can become spectacular on nights with calm upper atmosphere that happen infrequently but regularly at all sites studied so far. Starting from an ideal GLAO system, the influence of various instrumental errors (wave-front sensing, time delay, tilt, optics ripple, etc.) is studied, leading to the formulation of an error budget for GLAO. As the performance metrics of GLAO and classical AO are very different, we propose a new criterion for balancing error contributions.

Multi-IFU spectrographs such as KMOS can observe considerably deeper if their fields are adaptively corrected. MOAO and segmented-MCAO are two techniques that have been proposed to adaptively correct large fields on future ELTs. Field Sampling Adaptive Optics (FSAO) provides a series of significant advantages over both these methods. FSAO is similar in application to MOAO where each IFU field has its own Deformable Mirror (DM). FSAO independently steers the pupil images of a few IFU fields onto a single DM, which would work in combination with a ground-layer conjugated DM on the telescope. Wavefront reference sources from LGSs and NGSs are used in open-loop in a similar manner to MOAO. Each FSAO DM corrects for more than one IFU field (as with segmented MCAO) but the corrected subfields of each DM can be positioned anywhere in the telescope field instead of being fixed, a critical advantage when all objects are concentrated in a small field. Another significant advantage of FSAO is that the conjugate altitude of the FSAO DM can easily be modified by adjusting pupil overlap. The advantages of FSAO and the critical method of superimposition of the different pupil images on the DM in terms of image quality, distortion, position and rotation will be discussed as well as how the advantages increase with the primary diameter from 5-m to 42-m telescopes.

We have developed an PSF reconstruction algorithm for the NAOS adaptive optics system that is coupled with CONICA at ESO/VLT. We have modified the algorithm of Véran et al. (1997), originally written for PUEO at CFHT, to make use of the specific real-time wavefront-related data that observers with NACO receive together with their scientific images. In addition, we use the Vii algorithm introduced by Clénet et al. (2006) and Gendron et al. (2006) instead of the Uij algorithm originally used by Véran et al. (1997). Until now, tests on NAOS has been undertaken during technical time thanks to the NACO team at Paranal. A first test has been successfully performed to calibrate the orientation of reconstructed PSFs with respect to NACO images. We have also obtained two sets of PSF reconstruction test data with NACO in November 2006 and September 2007 to reconstruct PSFs. Discrepancies exist between the observed and reconstructed PSFs: their Strehl ratios are ~31% and ~39% respectively in Nov. 2006, ~31% and ~19% respectively in Sept. 2007. These differences may be at least partly explained by reconstructions that either did not account for the aliasing contribution or poorly estimated the noise contribution with the available noise information at that time. We have additionally just started to test our algorithm using the AO bench Sésame, at LESIA. Results are promising but need to be extended to a larger set of atmospheric conditions or AO correction qualities.

In the context of the SPHERE planet finder project, we further develop a recently proposed method, based on detection theory, for the efficient detection of planets using angular differential imaging. The proposed method uses the fact that with the SPHERE instrument the field rotates during the night, and can additionally use the fact that at each acquisition time, two images are recorded by the IRDIS instrument in two different spectral channel. The method starts with the appropriate combination of images recorded at different times, and potentially in different spectral channels, into so-called pseudo-data. It then uses jointly all these pseudo-data in a Maximum-Likelihood (ML) framework to detect the position and amplitude of potential companions of the observed star, taking into account the mixture of photon and detector noises and a positivity constraint on the planet's amplitude. A reasonable detection criterion is also proposed; it is based on the computation of the noise propagation from the images to the estimated flux of the potential planet. The method is validated on data simulating realistic conditions of operation, including residual aberrations before and after the coronagraph, residual turbulence after adaptive optics correction, and noise.

We evaluate the performance of the Multi-conjugate Adaptive optics Demonstrator (MAD) from H and K_s imaging of 30 Doradus in the Large Magellanic Cloud. Maps of the full-width half maximum (FWHM) of point sources in the H and K_s images are presented, together with maps of the Strehl ratio achieved in the K_s-band observations. Each of the three natural guide stars was at the edge of the MAD field-of-view, and the observations were obtained at relatively large airmass (1.4-1.6). Even so, the Strehl ratio achieved in the second pointing (best-placed compared to the reference stars) ranged from 15% to an impressive 30%. Preliminary photometric calibration of the first pointing indicates 5σ sensitivities of K_s~21.75 and H~22.25 (from 22 and 12 min exposures, respectively).

As an astronomical image post-processing technique, deconvolution from wavefront sensing (DWFS) is a powerful and low cost method for adaptive optics (AO) images reduction. It is based on deconvolution of short exposure images and simultaneous measuring wavefront sensor data, both are provided by adaptive optics system to improve the quality of images. However, for extended or dim sources observing, limited precision of the Wave Front Sensor (WFS) will lead to inferior correction quality of AO images, also these can hardly enhanced by DWFS method. We show here a simple and efficient solution, which combines the DWFS method with a shift-and-add (SAA) image reconstruction technique, designed for reduction of astronomical data obtained with AO system, especially extended objects. This scheme has been applied to the upgraded 61-actuator Shack-Hartmann based adaptive optics system, partially primary corrected extended object images at Yunnan observatory 1.2m telescope for astronomical high resolution imaging. Experimental result of Mars was presented.

The adaptive optics can only partially compensate the image blurred by atmospheric turbulence due to the observing condition and hardware restriction. A post-processing method based on frame selection and multi-frames blind deconvolution to improve images partially corrected by adaptive optics is proposed. The appropriate frames which are suitable for blind deconvolution from the recorded AO close-loop frames series are selected by the frame selection technique and then do the multi-frame blind deconvolution. There is no priori knowledge except for the positive constraint in blind deconvolution. It is benefit for the use of multi-frame images to improve the stability and convergence of the blind deconvolution algorithm. The method had been applied in the image restoration of celestial bodies which were observed by 1.2m telescope equipped with 61-element adaptive optical system at Yunnan Observatory. The results show that the method can effectively improve the images partially corrected by adaptive optics.

An iterative deconvolution algorithm is presented in detail which utilizes regularization to combine maximum-likelihood (ML) estimate of convolution error and several physical constraints to build error function. The physical constraints used in this algorithm include positivity, band-limit information and the information of multiple frames. By minimizing the combined error metric of individual ones, the object can be expected to be recovered from the noisy data. In addition, numerical simulation of Phase Screen distorted by atmospheric turbulence following the Kolmogorov spectrum is also made to generate the PSFs which are used to simulate the degraded images.

There are many various applications in astronomy which are using the WFC or UWFC (Ultra Wide-Field Camera) systems. UWFC systems frequently have so called SV (Space Variant) properties. Images obtained in UWFC systems are distorted by high order optical aberrations and objects on ultra wide-field images are very small. If we define the PSF (Point Spread Function) of optical system then we can use some suitable methods for restoration of original image. How to define the point spread function of LSI (Linear Space Invariant) and LSV (Linear Space Variant) systems is one of the most challenging questions of this paper.

We have analyzed the application of frame selection ("lucky imaging") to adaptive optics (AO), short-exposure observations of faint companions. We have used the instantaneous Strehl ratio as an image quality metric. The probability density function (PDF) of this quantity can be used to determine the outcome of frame selection in terms of optimizing the Strehl ratio and the peak-signal-to-noise-ratio of the shift-and-add image. In the presence of static speckles, frame selection can lead to both: improvement in resolution--as quantified by the Strehl ratio, as well as faint signal detectability--given by the peak-signal-to-noise-ratio. This theoretical prediction is confirmed with real data from AO observations using Lick Observatory's 3m Shane telescope, and the Palomar Observatory's 5m Hale telescope. In addition, we propose a novel statistics-based technique for the detection of faint companions from a sequence of AO-corrected exposures. The algorithm, which we call stochastic speckle discrimination, utilizes the "statistical signature" of the centre of the point spread function (PSF) to discriminate between faint companions and static speckles. The technique yields excellent results even for signals invisible in the shift-and-add images.

We have recently demonstrated diffraction-limited resolution imaging in the visible on the 5m Palomar Hale telescope. The new LAMP instrument is a Lucky Imaging backend camera for the Palomar AO system. Typical resolutions of 35-40 mas with Strehls of 10-20% were achieved at 700nm, and at 500nm the FWHM resolution was as small as 42 milliarcseconds. In this paper we discuss the capabilities and design challenges of such a system used with current and near future AO systems on a variety of telescopes. In particular, we describe the designs of two planned Lucky Imaging + AO instruments: a facility instrument for the Palomar 200" AO system and its PALM3K upgrade, and a visible-light imager for the CAMERA low-cost LGS AO system planned for the Palomar 60" telescope. We introduce a Monte Carlo simulation setup that reproduces the observed PSF variability behind an adaptive optics system, and apply it to predict the performance of 888Cam and CAMERA. CAMERA is predicted to achieve diffraction-limited resolution at wavelengths as short as 350 nm. In addition to on-axis resolution improvements we discuss the results of frame selection with the aim of improving other image parameters such as isoplanatic patch sizes, showing that useful improvements in image quality can be made by Lucky+AO even with very temporally and spatially undersampled data.

We propose a new post-processing technique for the detection of faint companions and the estimation of their parameters from adaptive optics (AO) observations. We apply the optimal linear detector, which is the Hotelling observer, to perform detection, astrometry and photometry on real and simulated data. The real data was obtained from the AO system on the 3m Lick telescope¹. The Hotelling detector, which is a prewhitening matched filter, calculates the Hotelling test statistic which is then compared to a threshold. If the test statistic is greater than the threshold the algorithm decides that a companion is present. This decision is the main task performed by the Hotelling observer. After a detection is made the location and intensity of the companion which maximise this test statistic are taken as the estimated values. We compare the Hotelling approach with current detection algorithms widely used in astronomy. We discuss the use of the estimation receiver operating characteristic (EROC) curve in quantifying the performance of the algorithm with no prior estimate of the companion's location or intensity. The robustness of this technique to errors in point spread function (PSF) estimation is also investigated.

Astronomical adaptive optics (AO) data analysis requires the knowledge of the PSF associated to the AO run. With new AO modes soon to become available (LTAO, GLAO) there is a request from the AO users community for the development of new PSF reconstruction algorithms. Question is: what is the required accuracy on the quality of the reconstruction ? Guide-lines are needed in order to check the validity/usefulness of a given PSF reconstruction approach. LTAO/GLAO PSF reconstruction algorithms are being studied but are not available yet, so we propose to analyze this issue by simulating AO data with an AO modeling tool, and doing the data reduction using modeled AO PSF with an increased level of difference with the initial AO PSF, for parameters that have potentially a large impact on the PSF structure: the seeing angle, the C²_N vertical distribution, the residual tip-tilt, LGS altitude fluctuations, and off-axis PSF variation (anisoplanatic effects). Results are given in the context of data analysis of an LTAO mode mimicking the planned VLT/GALACSI system. We do not take into account any instrument mode, and the telescope is assumed without aberrations. The current study is focused on the most critical type of data reduction: deconvolution. Algorithms are reviewed, and it is shown that for most classical deconvolution methods, the main impact of PSF reconstruction errors can already be described using either the so-called residual filter (ratio of exact OTF over reconstructed OTF) or more simply the difference between the exact and the reconstructed PSF. Using these two metrics, we explore the consequences of uncertainties on the five parameters introduced above. It is found that (1) in general, the impact of PSF reconstruction errors, while noticeable, appears to be surprisingly low, relaxing apparently the need for highly sophisticated PSF reconstruction algorithms; (2) in the case of Winer-like deconvolution, tip-tilt uncertainty is the most critical parameter, and has a noticeable impact on the residual PSF wings - which can be a problem when looking for faints objects in the vicinity of a bright star; (3) in the case of source extraction (CLEAN-like algorithms), seeing error clearly dominates, and the other errors have basically the same impact; (4) the impact of numerical effects during PSF deconvolution or extraction (sub-pixel PSF positioning error) is of the same order of magnitude than the effect of AO PSF parameters uncertainties.

The performance of high-resolution imaging with large optical instruments is severely limited by atmospheric turbulence, and an image deconvolution is required for reaching the diffraction limit. A new astronomical image deconvolution algorithm is proposed, which incorporates dynamic support region and improved cost function to NAS-RIF algorithm. The enhanced NAS-RIF (ENAS-RIF) method takes into account the noise in the image and can dynamically shrink support region (SR) in application. In restoration process, initial SR is set to approximate counter of the true object, and then SR automatically contracts with iteration going. The approximate counter of interested object is detected by means of beamlet transform detecting edge. The ENAS-RIF algorithm is applied to the restorations of in-door Laser point source and long exposure extended object images. The experimental results demonstrate that the ENAS-RIF algorithm works better than classical NAS-RIF algorithm in deconvolution of the degraded image with low SNR and convergence speed is faster.

The Thirty Meter Telescope (TMT) will implement a Laser Guide Star Facility (LGSF), which will generate up to nine Na laser beams in at least four distinct asterisms. The TMT LGSF conceptual design is based upon three 50W solid state, continuous wave, sum frequency 589 nm lasers and conventional beam transport optics. In this paper, we provide an update to the TMT LGSF conceptual design. The LGSF top end and the beam transfer optics have been significantly redesigned to compensate for the TMT telescope top end flexure, to adapt for the new TMT Ritchey-Chretien optical design, to reduce the number of optical surfaces and to reduce the mass and volume. Finally, the laser service enclosure has been relocated within the telescope azimuth structure. This will permit the lasers to operate with a fixed gravity vector, but also requires further changes in the beam transport optical path.

The Laser Guide Star Facility (LGSF) is installed on the UT4 (Yepun) telescope at Paranal Observatory in Chile. On the same telescope, two instruments are equipped with adaptive optics: an infrared spectro imager (CONICA) below the adaptive optics module NAOS; and an integral field spectrograph (SINFONI). The LGSF is tuned to the sodium D2 line to generate an artificial reference star, for both CONICA and SINFONI. Although the LGSF is a complex laser system, rather different from the other instruments at Paranal, it has been designed to run remotely without any hand-on tuning for a period of one week. The LGSF system has now been in operation for several months, in conjunction with the Aircraft camera Avoidance System (AAS). In this article, we report on the technical performance achieved by the LGSF in operational conditions. We also provide a summary of the technical problems and operational constraints we have faced so far. We present the current operations and maintenance procedures implemented at Paranal. We also present the evolution of the human resources needed to operate and maintain the LGSF operational from commissioning to routine operations. Finally, we discuss possible improvements to reduce the workload to maintain and operate the LGSF.

The Gemini Observatory is in the final integration and test phase for its Multi-Conjugate Adaptive Optics (MCAO) project at the Gemini South 8-meter telescope atop Cerro Pachón, Chile. This paper presents an overview and status of the laser-side of the MCAO project in general and its Beam Transfer Optics (BTO), Laser Launch Telescope (LLT) and Safety Systems in particular. We review the commonalities and differences between the Gemini North Laser Guide Star (LGS) facility producing one LGS with a 10W-class laser, and its southern sibling producing five LGS with a 50W-class laser. We also highlight the modifications brought to the initial Gemini South LGS facility design based on lessons learned over 3 years of LGS operations in Hawaii. Finally, current integration and test results of the BTO and on-sky LLT performance are presented. Laser first light is expected in early 2009.

We describe the work that has gone into taking the sodium Laser Guide Star (LGS) program on the Palomar AO system from a successful experiment to a facility instrument. In particular, we describe the operation of the system, the BTO (beam transfer optics) system which controls the path of the laser in the dome, the aircraft safety systems and the optical systems which allow us to take advantage of the unique properties of the macro/micro pulse laser. In addition we present on sky performance results that demonstrate K-band Strehl ratios of up to 48%

Observatories using laser guide star (LGS) adaptive optics (AO) systems need to implement safety systems to protect aircraft from being illuminated by the lasers. These systems are made up of a combination of control measures and procedures. In the USA the Federal Aviation Administration (FAA) is responsible for protecting aircraft and issues a determination of no-objection to the use of lasers in the navigable airspace before operations can begin. To date, the FAA has required all observatories with LGS systems to use human aircraft spotters as part of the aircraft safety system. This paper discusses how we might go about developing an automated alternative that is more reliable and less expensive than using spotters and is also acceptable to the FAA. Specific challenges are identified and discussed. These challenges include understanding the FAA perspective on issues related to aircraft safety and lasers, understanding the FAA evaluation and approval process for specific control measures, safety systems and operational procedures, working with appropriate standards committees to develop requirements and performance validation plans which lead to quantifiable confidence. We would also like to solicit collaboration from within the Mauna Kea astronomy community and also the broader astronomical community.

In this contribution, we will present the approach used to manage the operational problems of the Laser Guide Star Facility (LGSF) installed in the Yepun telescope at La Silla Paranal Observatory. In this scope we will introduce the Paranal Problem Report System (PPRS) and the LGSF breakdown structure created to track and analyze the technical problems using the PPRS system. The early introduction of this tool has allowed us to accumulate enough data to review the evolution of the LGSF and its respective subsystem based on the problems reports frequency in a monthly basis. The analysis shows the frequency evolution over time considering the complete LGSF system and also the ratio of problems frequency to LGS usage per month. In addition, a cumulative approach is also used to provide information about the fraction of the problems originated by each subsystem since the beginning of the operations.

We analyze the image quality of an extraterrestrial object imaged by astronomical optical systems through the turbulent atmosphere. The relative increase of the Strehl parameter is calculated under adaptive corrections with laser guide star. We compare the efficiency of adaptive correction for different types of the guide sources. The calculations are performed for different models of the vertical distribution of the structural parameter of the refractive index of the turbulent atmosphere. A special wavefront sensor is applied, which operates with a full-aperture collimated laser beam as a reference wave. This layer-oriented wavefront sensor is used to reconstruct the continuous phase of the reference wave. Our results show that the parameters of the reconstructed field are quite close to that of a plane wave. A significant increase of the Strehl parameter indicates excellent correction of higher order modes, which are usually difficult to sense and correct with traditional LGS techniques using a focused laser beam. A comparative analysis of various atmospheric models revealed some noticeable differences in correlation radii for the plane and spherical waves.

In calculating the return flux of sodium laser guide stars (LGS), often only the best return conditions are assumed, relying on strong optical pumping with a circularly polarized laser. However, one can obtain this optimal return only along one specific laser orientation on the sky, depending on the direction of the geomagnetic field. Sodium atoms precess around magnetic field lines which cycles the magnetic quantum number, reducing the effectiveness of optical pumping. The risk is hence for the system designer to overestimate the effective return flux for a given laser power. In this paper we present calculations for the effect of the geomagnetic field on the return flux. Optical pumping actually produces little improvement in most observing directions. In addition, we find that at many observatory locations, the direction of optimal return flux is very close to the horizon, often below the observing limit.

The forthcoming Extremely Large Telescopes, and the new generation of Extreme Adaptive Optics systems, carry on a boost in the number of actuators that makes the real-time correction of the atmospheric aberration computationally challenging. It is necessary to study new algorithms for performing Adaptive Optics at the required speed. Among the last generation algorithms that are being studied, the Fourier Transform Reconstructor (FTR) appears as a promising candidate. Its feasibility to be used for Single-Conjugate Adaptive Optics has been extensively proved by Poyneer et al.^[1] As part of the activities supported by the ELT Design Study (European Community's Framework Programme 6) we have studied the performance of this algorithm applied to the case of the European ELT, in two different cases: single-conjugate and ground-layer adaptive optics and we are studying different approaches to apply it to the more complex multi-conjugate case. The algorithm has been tested on ESO's OCTOPUS software, which simulates the atmosphere, the deformable mirror, the sensor and the closed-loop control. The performance has been compared with other algorithms as well as their response in the presence of noise and with various atmospheric conditions. The good results on performance and robustness, and the possibility of parallelizing the algorithm (shown by Rodríguez-Ramos and Marichal-Hernández) make it an excellent alternative to the typically used Matrix-Vector Multiply algorithm.

Most computers in the past have been equipped with floating point processing capabilities, allowing an easy and brute-force solution for the machine computation errors, not requiring any specific tailoring of the computation in nearly hundred percent of situations. However, the computation needed for the adaptive optics real-time control in 30-50 meter telescopes is big enough to cause trouble to conventional von-Neumann processors, even if Moore's Law is valid for the next years. Field Programmable Gate Array (FPGAs) have been proposed as a viable alternative to cope with such computation needs^[1,2], but--at least today's chips--will require fixed-point arithmetic to be used instead. It is then important to evaluate up to what point the accuracy and stability of the control system will be affected by this limitation. This paper presents the simulation and laboratory results of the comparison between both arithmetics, specifically evaluated in an adaptive optics system. The real-time controller has been modeled as black box having as input the wavefront sensor camera digital output data, providing a digital output to the actuators of the deformable mirror, and with the task of internally computing all outputs from the inputs. MATLAB fixed-point library has been used to evaluate the effect of different precision lengths (5-10 fractional bits) in the computation of the Shack-Hartmann subaperture centroid, in comparison with the reference 64-bit floating-point arithmetic and with the noise floor of the real system, concluding that the effect of the limited precision can be overcome by adequately selecting the number of fractional bits used in the representation, and tailoring that number with the needs at every step of the algorithm.

ELTs laser guide stars wavefront sensors are planned to have specifically developed sensor chips, which will probably include readout logic and D/A conversion, followed by a powerful FPGA slope computer located very close to it, but not inside for flexibility and simplicity reasons. This paper presents the architecture of an FPGA-based wavefront slope computer, capable of handling the sensor output stream in a massively parallel approach. It will feature the ability of performing dark and flat field correction, the flexibility needed for allocating complex processing schemes, the capability of undertaking all computations expected to be performed at maximum speed, even though they were not strictly related to the calculation of the slopes, and the necessary housekeeping controls to properly command it and evaluate its behaviour. Feasibility using today's technology is evaluated, clearly showing its viability, together with an analysis of the amount of external memory, power consumption and printed circuit board space needed.

The Thirty Meter Telescope (TMT) will implement a first light facility Laser Guide Star Multi Conjugate Adaptive Optics System, NFIRAOS, which will feed three science instruments on the telescope Nasmyth platform. This system will include two deformable mirrors, six laser guide star wavefront sensors, and multiple tip/tilt/focus wavefront sensors located in the instruments. The Real Time Controller (RTC) is one of the most innovative and essential components of this first light AO system. In this paper, we provide an update on the NFIRAOS RTC overall requirements and challenges, and in particular, on the tomography and fitting wavefront reconstruction algorithms. Several implementations of a minimum variance reconstructor are presented together with their processing and memory requirements.

The Adaptive Optics Laboratory at the University of Victoria (Canada) and the Subaru Telescope NAOJ (Hawaii) are collaborating to develop a simple method allowing open-loop control of MEMS deformable mirrors. This method consists of an iterative algorithm based on 3 simple equations and 4 constants. The 4 constants are different for each mirror, therefore a characterization step is necessary to evaluate their values for a given mirror. In this paper we describe the model and the 3 equations it relies on. We also propose a characterization methodology and finally present the preliminary results respectively obtained on Victoria and Subaru test beds.

Hardware and software specialized for real time control reduce the timing jitter of executables when compared to off-the-shelf hardware and software. However, these specialized environments are costly in both money and development time. While conventional systems have a cost advantage, the jitter in these systems is much larger and potentially problematic. This study analyzes the timing characterstics of a standard Dell server running a fully featured Linux operating system to determine if such a system would be capable of meeting the timing requirements for closed loop operations. Investigations are preformed on the effectiveness of tools designed to make off-the-shelf system performance closer to specialized real time systems. The Gnu Compiler Collection (gcc) is compared to the Intel C Compiler (icc), compiler optimizations are investigated, and real-time extensions to Linux are evaluated.

The effects of a controller on the residual wavefront variance in an adaptive optics system can be represented by a discrete-time system. Consequently, the controller design is optimized by the solution of a discrete-time Linear- Quadratic-Gaussian (LQG) problem. This paper analyzes the structure of the LQG controller and the effects of varying loop delay and actuator lag on the controller. The loop delay is represented as a delay of actuator commands to emphasize the structure.

Specialized control structures can be used to reduce the computational burden of determining the control at each frame. The parameters that define these controllers are chosen to maximize performance. The optimization of the parameters is more efficient if gradient information is available. This paper presents the gradient calculation for an arbitrarily parameterized controller of an adaptive optics system. The gradients are then specialized to modal gain and proportional-plus-integral controllers.

All thing being equal, increasing the sampling rate of a computer-controlled feedback loop extends its effective bandwidth, and thus the achievable performance in terms of disturbance rejection. This applies to AO systems, where deformable mirror's (DM) control voltages are computed from wavefront sensor's (WFS) measurements. However, faster sampling, i.e. shorter exposure time for the WFS's CCD, results (especially for low-flux astronomical applications) in higher measurement noise, thereby degrading overall performance. A way to circumvent this limitation is to increase only the DM's control rate. However, standard integral AO control is inherently ill-suited for such multirate mode, because integrators require an uninterrupted measurement stream to maintain closed-loop stability. On the other hand, Linear Quadratic Gaussian (LQG) AO control, where DM controls are computed from explicit predictions of future values of the turbulent phase provided by a Kalman filter, can be easily adapted to multirate configurations where the WFS sampling period is a multiple of the DM's one, provided that a stochastic model of the turbulent phase at the fast (DM) rate is available. The Kalman filter, between two successive measurements, operates in (observer) open-loop mode, with predictions updated by extrapolating current trends in the turbulent phase's trajectory. Thus, while simple vector-valued AR(1) turbulence models are sufficient for single-rate LQG AO loops, more complex stochastic models are likely to be needed to achieve good performance in multirate configurations.

The CAFADIS camera is a new sensor patented by Universidad de La Laguna (Canary Islands, Spain): international patent PCT/ES2007/000046 (WIPO publication number WO/2007/082975). It can measure the wavefront phase and the distance to the light source at the same time in a real time process. It uses specialized hardware: Graphical Processing Units (GPUs) and Field Programmable Gates Arrays (FPGAs). These two kinds of electronic hardware present an architecture capable of handling the sensor output stream in a massively parallel approach. Of course, FPGAs are faster than GPUs, this is why it is worth it using FPGAs integer arithmetic instead of GPUs floating point arithmetic. GPUs must not be forgotten, as we have shown in previous papers, they are efficient enough to resolve several problems for AO in Extremely Large Telescopes (ELTs) in terms of time processing requirements; in addition, the GPUs show a widening gap in computing speed relative to CPUs. They are much more powerful in order to implement AO simulation than common software packages running on top of CPUs. Our paper shows an FPGA implementation of the wavefront phase recovery algorithm using the CAFADIS camera. This is done in two steps: the estimation of the telescope pupil gradients from the telescope focus image, and then the very novelty 2D-FFT over the FPGA. Time processing results are compared to our GPU implementation. In fact, what we are doing is a comparison between the two different arithmetic mentioned above, then we are helping to answer about the viability of the FPGAs for AO in the ELTs.

Telescopes of 8 meter class, like Large Binocular Telescope (LBT), are based on the concept of Deformable Secondary Mirror (DSM); in order to calculate the best DSM shape that correct the measured aberrations we need to calibrate the AO system, so we need a correlation between the DSM and the wave front sensor (WFS), i.e. we need the Interaction Matrix (IM). Usually we obtain the IM in laboratory or at the telescope using as source a reference fiber that illuminates both the deformable mirror and wave front sensor. But in case of LBT and all large telescopes, this technique can be very difficult or sometimes impossible, and calibration may be required to be performed on sky. So we need new calibration techniques, and we investigate about sinusoidal modulation one for LBT case. In the Arcetri solar tower (inside Arcetri Observatory) we recreated a set up environment similar to the telescope, and thanks to that we can test the calibration system in the same condition of the LBT. In preparation for the test some simulations of this sinusoidal modulation technique were needed, in order to choose the best parameters that increased SNR and reduced integration time. The paper will detail the simulation results of the calibration LBT system made with this new technique, and these results will be used to drive our tests in the tower.

ELT laser guide star wavefront sensors are planned to handle an expected amount of data to be overwhelmingly large (1600×1600 pixels at 700 fps). According to the calculations involved, the solutions must consider to run on specialized hardware as Graphical Processing Units (GPUs) or Field Programmable Gate Arrays (FPGAs), among others. In the case of a Shack-Hartmann wavefront sensor is finally selected, the wavefront slopes can be computed using centroid or correlation algorithms. Most of the developments are designed using centroid algorithms, but precision ought to be taken in account too, and then correlation algorithms are really competitive. This paper presents an FPGA-based wavefront slope implementation, capable of handling the sensor output stream in a massively parallel approach, using a correlation algorithm previously tested and compared to the centroid algorithm. Time processing results are shown, and they demonstrate the ability of the FPGA integer arithmetic in the resolution of AO problems. The selected architecture is based in today's commercially available FPGAs which have a very limited amount of internal memory. This limits the dimensions used in our implementation, but this also means that there is a lot of margin to move real-time algorithms from the conventional processors to the future FPGAs, obtaining benefits from its flexibility, speed and intrinsically parallel architecture.

This paper describes the recent upgrade performed on the W. M. Keck Observatory Adaptive Optics (AO) systems, in which the wavefront sensors and wavefront controllers were replaced with components based on new technology. The performance of the upgraded system has yielded an increase in limiting guide star magnitude, an increased Strehl ratio for both Laser Guide Star (LGS) and Natural Guide Star (NGS) modes, and has significantly improved reliability and maintainability compared to the original system. Moreover, the controller is scalable, allowing for future upgrades and improvements as needed. We present an overview of the project; describe the basic architecture of the new wavefront sensor and controller; discuss some of the unique features of the system, including the closed loop mirror positioning system, custom wavefront sensor optics, and full-frame-rate telemetry server; and conclude with results from engineering and science tests of the new controller on the Keck II AO system.

Performance of adaptive optics (AO) systems is limited by the tradeoff between photon noise at the wavefront sensor and temporal error from the duty cycle of the controller. Optimal control studies have shown that this temporal error can be reduced by predicting the turbulence evolution during the control cycle. We formulate a wind model that divides the wind into two components: a quasi-static layer and a wind-driven frozen-flow layer. Using this internal wind model, we design a computationally efficient controller that is able to estimate and predict the dynamics of a single windblown layer and simulate this controller using on-sky data from the Palomar Adaptive Optics system. We also present results from a laboratory implementation of multi-conjugate AO (MCAO) with multi-layer wind estimation in conjunction with tomographic reconstruction. The tomography engine breaks the atmosphere into discrete layers, each with its own wind estimator. The resulting MCAO control algorithm is able to track and predict the motion of multiple wind layers with wind estimates that update at every controller cycle. Once the wind velocities of each layer are known, the deformable mirror update speed is no longer limited by the wavefront sensor exposure time so it is possible to send multiple correction updates to the deformable mirror each control cycle in order to dynamically track wind layers across the telescope aperture. The result is better dynamics in the feedback control system that enables higher closed-loop bandwidth for a given wavefront sensor frame rate.

In this paper we will discuss the application of different optimal control techniques for the adaptive optics system of the LBT telescope which comprises a pyramid wavefront sensor and an adaptive secondary mirror. We have studied the application of both the Kalman and the H∞ filter to estimate the temporal evolution of the phase perturbations due to the atmospheric turbulence and the telescope vibrations. We have evaluated the performance of these control techniques with numerical simulations in preparation of the laboratory tests that will be carried out in the Arcetri laboratories.

The turbulent wavefront reconstruction step in an adaptive optics system is an inverse problem. The Mean-Square Error (MSE) assessing the reconstruction quality is made of two terms, often called bias and variance. The latter is also commonly referred as the noise propagation. The aim of this paper is to investigate the evolution of these two error contributions when the number of parameters to be estimated becomes of the order of 10 ⁴. Such dimensions are expected for the adaptive optics systems on the Extremely Large Telescopes. We provide an algebraic formalism to compare the MSE of Maximum Likelihood and Maximum A Posteriori linear reconstructors. A Generalized Singular Value Decomposition applied on the reconstructors theoretically enhances the differences between zonal and modal approaches, and demonstrates the gain in using Maximum A Posteriori method. Thanks to numerical simulations, we quantitatively study the evolution of the MSE contributions with respect to the pupil shape, to the outer scale of the turbulence, to the number of actuators and to the signal-to-noise ratio. Simulations results are consistent with previous noise propagation studies and with our algebraic analysis. Finally, using the Fractal Iterative Method as a Maximum A Posteriori reconstruction algorithm in our simulations, we demonstrate a possible reduction of the MSE of a factor 2 in large adaptive optics systems, for low signal-to-noise ratio.

We present a cost-effective scalable real-time wavefront control architecture based on off-the-shelf graphics processing units hosted in an ultra-low latency, high-bandwidth interconnect PC cluster environment composed of modules written in the component-oriented language of nesC. We demonstrate the architecture is capable of supporting the most computation and memory intensive wavefront reconstruction method (vector-matrix-multiply) at frame rates up to 2 KHz with latency under 250 &mgr;s for the PALM-3000 adaptive optics systems, a state-of-the-art upgrade on the 5.1 meter Hale Telescope that consists of a 64x64 subaperture Shack-Hartmann wavefront sensor and a 3368 active actuator high order deformable mirror in series with a 349 actuator "woofer" DM. This architecture can easily scale up to support larger AO systems at higher rates and lower latency.

We present the research status of a deformable mirror made of a magnetic liquid whose surface is actuated by a triangular array of small current carrying coils. We demonstrate that the mirror can correct a 11 μm low order aberrated wavefront to a residual RMS wavefront error 0.05 μm. Recent developments show that these deformable mirrors can reach a frequency response of several hundred hertz. A new method for linearizing the response of these mirrors is also presented.

We describe a compact integrated module implementing a low-cost adaptive optics system. It is targeted as a correction system for small telescopes with primary mirror diameter up to 1 m, operating on a natural guide star with magnitude at least 4 (for a 25 cm telescope). It is supposed to provide stable diffraction-limited imaging of stars, double stars, planets and artificial bodies in various seeing conditions. Besides, it allows correcting for static aberrations of the telescope, observer's ocular aberrations and fine adjustment of focus. The first on-sky tests have demonstrated closed-loop operation with correction for aberrations.

The Zonal Bimorph Deformable Mirror (ZBDM) is a new concept of adaptive mirror. It exploits the benefits normally associated with bimorph mirrors, namely simple rugged construction, low capacitance, and cost effectiveness, but in a significant departure from classical, edge supported bimorphs each element is supported from underneath. This results in a localised (zonal) response and enables the device to be scalable up to large aperture, multi-1000 element devices. Crucially, the combination of continuous support coupled with the use of flexi-circuit interconnect promotes the assembly of a high density 'tweeter' deformable mirror (DM) onto a lower density, high dynamic range 'woofer' DM to generate an integrated, dual-stage deformable mirror which can deliver both high resolution and high dynamic range simultaneously. Such a device has the potential to significantly simplify the design of astronomical adaptive optics (AO) systems. We present the progress made on the development of the ZBDM as part of a collaborative project funded by the newly formed UK Science and Technology Facilities Council.

Combining high-end sensor, display and field programmable gate array technologies a new combined optically addressable spatial light modulator device is developed, and built. Parallel, programmable hardware provides an efficient way to process the measured wavefront data. Using these data and appropriate phase modulation of the built in LCOS display a complete adaptive optic system can be implemented. As it is built from commercially available, sophisticated components it provides an affordable solution, without real compromise between the achievable resolution, speed and overall performance. Primarily, we intend to apply this device in solar telescopes, where high speed, high resolution, correlation based wavefront sensing is required.

The Gemini Planet Imager (GPI) is currently in production for the Gemini Telescope in Chile. This instrument will directly image young jovian exoplanets, aided by a micro-electrical mechanical systems (MEMS) deformable mirror (DM). Boston Micromachines MEMS mirrors operate thousands of actuators to provide a well-sampled correction at high spatial frequencies. However, because MEMS stroke alone is insufficient to fully correct the atmosphere in the near-IR on an 8-meter telescope, a dual-mirror system is planned for GPI: The MEMS is used as a 'tweeter' to correct the higher spatial frequencies while a separate 'woofer' DM will be used to correct the lower frequencies. During operation at GPI, any saturated actuators would scatter starlight into the dark hole instead of allowing it to be removed coronagraphically; thus, stroke saturation on the MEMS is tolerated only at the 5-sigma level. In the Laboratory for Adaptive Optics, we test the ability of the MEMS to counter atmospheric turbulence. The MEMS shape is set to random iterations of woofer-corrected Kolmogorov phase screens with varying woofer sizes. We find that, for r0 = 10 cm, saturation decreases from several percent to a few tenths of a percent (∼3-sigma) when using a 100cm-pitch woofer. The MEMS we tested has 0.2 &mgr;m inter-actuator stroke for a 200V-range. Nonetheless, saturation (when it occurs) appears to be due to low-order peak-to-valley stroke even in the woofer-corrected case. Gemini characteristically has r0 = 15 cm, so future work includes extrapolating to find where the 5-sigma saturation level occurs.

The ability to manufacture larger adaptive optics mirror rely also on the availability of metrology tools suitable for the purpose to validate the mirrors. In the framework of the ELT M4 adaptive, 2.5 m diameter, plane mirror we devised a series of tools able to certify that the plane wavefront is achieved and kept in place. A stitching series of small beams is conjugated with a whole image of the mirror thanks to a big, grazing incidence interferometric cavity. The set is completed by a novel piston sensing device which collate different segments of the (possibly) multiple mirror. We describe here the foreseen procedure and the status of the prototype realization.

The Adaptive Secondary Mirror (ASM) for LBT arrived in its final characterization phase. In order to use its large stroke performances and high order correction capability, we needed to develop a fast and accurate calibration procedure which use optical measurements and correlates them with signals of capacitive sensors co-located with the actuators. Each capacitive sensor gives a signal related to the local gap between the Reference Body and the Thin Shell of the ASM. The main issue in this implementation is the inverse relationship between mirror position (quantity to be measured) and capacitance (sensed quantity), and the evaluation of the effective reference and stray capacitance for each actuators that affects the calibration parameters. We developed a new method to correlate interferograms optically describing the mirror shape and the shell pistoning: moreover, with a non-linear data fit, we solved the unknown calibration parameters to find the linearization formula to be implemented in the system, giving a optimal solution to the capacitive sensor calibration problem.

Actual measurement of vibrating shape of a bimorph deformable mirror is presented to discuss the characteristics of resonance. Understanding the vibration properties of a bimorph deformable mirror is a key issue to overcome resonance problem, a major drawback of this type of deformable mirror, and to make full use of its advantages. Two-dimensional vibrating shape of the deformable mirror surface, not only at a point, is essential to figure out the resonance behavior. The results are informative for improvement of mechanical design or control software.

In the framework of the E-ELT Design Study financed by the European Community under OPTICON-FP6, the INAFAstronomical Observatory of Brera (INAF-OAB) has developed a technique for the manufacturing of thin optical segments. This study has the potential to fulfill the requirements of speed of production, contained costs and good optical quality for adaptive optics mirrors of the future. Following this approach these shells are produced by means of an hot slumping technique in which an initially flat thin Borofloat^TM glass sheet is placed onto a high quality ceramic mold, used as a master, to impart a precise shape to the glass by means of a thermal cycle. The thickness of these shells is of about 1.7 mm, making the optical surface very floppy and easy to be deformed. A previous investigation made on small size segments (diam. 130 mm) has shown quite encouraging results. The final goal of this study is to produce a concave spherical mirror prototype of 500 mm diameter. In this paper we report the last results of this effort in scaling-up the procedure and related problems concerning the optical testing.

This paper examines the possibility of constructing deformable mirrors for adaptive optics with a large number of degrees of freedom, by assembling segmented silicon mirrors with bimorph piezoelectric actuation. The production process relies on silicon wafers and thick film PZT deposition technology; it is able to lead to an actuation pitch of the order of 5 mm, and the manufacturing costs appear to grow only slowly (linearly or less) with the number of degrees of freedom in the adaptive optics.

A Deformable Mirror Controller (DMC) has been devised to overcome the open-loop nature of Multi Object Adaptive Optics (MOAO), in particular for AO systems with update rates of 1 ms or less. The system is based on a figure sensor, which uses a monochromatic illumination source and a Shack-Hartmann (SH) wavefront sensor (WFS) to obtain a fine sampling of DM's 3D surface. The sensor's beam is optically separated from the science path in order to not interfere with science observations. The DMC incorporates a real-time controller in charge of driving the DM. This controller runs in a dedicated Field-Programmable-Gate-Array (FPGA) based processor to keep up with stringent speed requirements. The DMC is being tested in the laboratory and is part of CANARY, an MOAO on-sky demonstrator to be installed at the William Hershel Telescope.

We are developing a normal incident EUV-telescope for a future space experiment, using an adaptive optics. The primary mirror and the secondary mirror were coated with Mo/Si multi-layers. The secondary mirror is a deformable mirror. The reference wave is produced with a 1 micro-m pin hole laser and its wave front shape is used for a correction of the EUV wave shape. The imaging experiments with optical was performed with the adaptive optics system. The imaging with 13.5nm EUV was also performed but without the adaptive optics system. The optical image is almost diffraction limited. A ray trace simulation was performed and a correction method in our system, where the EUV wave form is corrected using the optical reference lights, was investigated.

High-contrast imagers dedicated to the search for extrasolar planets are currently being developed for the VLT (SPHERE) and Gemini (GPI) observatories. A vital part of such a high-contrast imager is the extreme adaptive optics (XAO) system that very efficiently removes effects of atmospheric turbulence and instrument aberrations. The high order test bench (HOT) implements an XAO system under realistic telescope conditions reproduced by star and turbulence generators. New technological developments (32x32 actuator micro deformable mirror, read-noise free electron multiplying CCD60, SPARTA real time computer) are used to study and compare two potential XAO wave front sensors: The Pyramid- and the Shack-Hartmann wave front sensors. We will describe the overall design of HOT including the sub-systems. We will present the closed loop study results of the behavior of the Shack-Hartmann wave front sensor in terms of linearity, sensitivity to calibration errors, performance and other specific issues.

The Naval Research Laboratory (NRL) has been conducting research in novel portable adaptive optics systems for many years. These systems are tested exhaustively in a laboratory environment before being migrated to field experiments on astronomical telescopes. As part of the laboratory testing, an atmosphere simulator hardware testbed has been developed to provide a realization of atmospheric turbulence based on Kolmogorov statistics. In this testbed, a high-pixel count liquid crystal spatial light modulator induces the atmospheric turbulence through a series of computer calculated phase maps. User controls allow a wide range of telescope apertures and seeing conditions to be explored for testing the adaptive optics system. This paper explains and reports on the use of this dynamic and expandable system in characterizing the performance and optimization parameters of the adaptive optics systems at NRL.

VASAO is an ambitious project that explores new conceptual direction in the field of astronomical adaptive optics. In the era of 8 meter and larger telescopes, and their instrument costs and telescope time pressure, there is a natural niche for such ground-breaking conceptual development in the 4 meter class telescope. The aim of VASAO is to provide diffraction limited imaging in the visible with 100% sky coverage; the challenge (but potential rewards) arises from the simultaneity of these requirements. To this end, CFHT is conducting a feasibility study based on the polychromatic guide star concept (Foy et al., 1995 [4]) coupled with a high order curvature AO system, presented in this paper. A number of experiments have been started (or carried out) to study the challenges and limits of the techniques involved in an operational setting; these include the FlyEyes detector, and a polychromatic tip-tilt test on natural stars. Because such a project straddles such a fine line between facility instrument and experimental facility, careful thought has to be given to the balance between modes of operations and potential astrophysical targets.

Direct detection of exo-planets from the ground will become a reality with the advent of a new class of extreme-adaptive optics instruments that will come on-line within the next few years on 8-10 meters class telescopes. One major technical challenge in reaching the requisite high contrast at small angles is the sensing and control of wave front errors which becomes even more challenging in the case of the extremely large telescopes. Extensive computer simulations have shown the ability of such systems to deliver high Strehl ratio correction expected (within EPICS preliminary study for instance) but few experiments dedicated to ELTs have been realized so far. This paper will discuss the nature of this problem, and describe recent laboratory results from the LAM Extreme Adaptive Optics bench whose purpose is to provide validation of the numerical simulations as well as to be a testbed to develop concepts, architectures, and control algorithms for the future ELTs extreme adaptive optics systems. This test bench is optimized for ultra-high contrast applications requiring XAO with realistic telescope conditions reproduced by star and turbulence generators and including segmented primary mirror. We present here preliminary results, showing an RMS wavefront control at level smaller than 10 nm rms for static aberrations.

We attempt to linearize the output of the Shack-Hartmann wavefront sensor in the ViLLaGEs instrument. ViLLaGEs (Visible Light Laser Guidestar Experiments) is a MEMS-based Adaptive Optics system on the 1 - meter Nickel telescope at Lick Observatory meant to provide correction at visible wavelengths with a 9x9 subaperture Hartmann sensor. We estimate that the open-loop accuracy of ViLLaGEs is ~40 nm. We "calibrate" the Hartmann linearity by raster scanning a tip/tilt mirror downstream of an internal fiber and inverting the resulting signal, forming a lookup table of unbiased tilts. From this calibration, we conclude that nonlinearity is a minor effect in the open-loop operation of ViLLaGEs, on the order of ~15 nm. We show through simulations of Shack-Hartmann sensors that this error is likely due to an internal pupil mask not physically conjugate to the telescope pupil. We test the resulting lookup table on an internal "turbulator" in ViLLaGEs, or a rotating plate meant to simulate the wind-driven atmosphere, and find that the Strehls with and without the lookup table are indistinguishable.

Classic Adaptive Optics (AO) is now a proven technique to correct turbulence on earth based astronomical telescopes. The corrected field of view is however limited by the anisoplanatism effect. Multi-Conjugate AO (MCAO) aims at providing a wide field of view correction through the use of several deformable mirrors and of multi-guide-star wavefront sensing. However the performance optimization of such complex systems raises new questions in terms of calibration and control. We present our current developments on performance optimization of MCAO systems. We show that performance can be significantly improved with tomographic control based on Linear Quadratic Gaussian control, compared with more standard methods. An experimental demonstration of this new approach is going to be implemented on HOMER, the recent bench developed at ONERA devoted to MCAO laboratory research. We present here results in closed-loop in AO, GLAO and MCAO with an integrator control. This bench implements two deformable mirrors and a wide field Shack-Hartman wavefront sensor.

We have developed an improvement of the well-known SLODAR (Slope Detection and Ranging) technique which allows us to monitor the ground layer throughout the night with resolution of a few tens of meters. We will present data we have obtained during two one-week observing sessions at the Las Campanas Observatory, Chile. The first observing session we have often observed a persistent, low ground layer which dominates the seeing. The second observing session the free-atmosphere dominated the seeing. We will present the instrument design; real-time software; describe the observing sessions, the data and results.

In this paper we focus on wide Field of View (FoV) Adaptive Optics (AO) correction for the EAGLE instrument for the European Extremely Large Telescope (E-ELT). The main goal is to increase the Ensquared Energy (EE) so as to reach decent spectroscopic SNRs as well as achieving a good spatial resolution. This typically means that more than 40% of the PSF flux has to be gathered into a 75x75 mas² box. Moreover, for such an application, the correction does not have to be uniform over the whole 5 arcmin FoV but just has to be optimised in a few directions, i.e. the scientific targets. In that frame we study the performance of Multi-Object AO (MOAO) systems, where we focus on the influence of the Guide Star constellations and the consequences of using Laser Guide Stars (LGS) for wavefront sensing. Unfortunately, for such sources, low-order modes such as tip/tilt modes cannot be measured. We have therefore developed a new method allowing us to partially simulate such effects in analytical AO simulation codes, which is highly detailed in this paper. Thanks to this method, we have been able to derive preliminary results in terms of system design as well as sky coverage.

Adaptive optics systems based on laser guide stars still need a natural guide star (NGS) to correct for the image motion caused by the atmosphere and by imperfect telescope tracking. The ability to properly compensate for this motion using a faint NGS is critical to achieve large sky coverage. For the laser guide system (GLAS) on the 4.2 m William Herschel Telescope we designed and tested in the laboratory and on-sky a tip-tilt correction system based on a PC running Linux and an EMCCD technology camera. The control software allows selection of different centroiding algorithms and loop control methods as well as the control parameters. Parameter analysis has been performed using tip-tilt only correction before the laser commissioning and the selected sets of parameters were then used during commissioning of the laser guide star system. We have established the SNR of the guide star as a function of magnitude, depending on the image sampling frequency and on the dichroic used in the optical system; achieving a measurable improvement using full AO correction with NGSes down to magnitude range R=16.5 to R=18. A minimum SNR of about 10 was established to be necessary for a useful correction. The system was used to produce 0.16 arcsecond images in H band using bright NGS and laser correction during GLAS commissioning runs.

The SOAR Adaptive Module (SAM) will compensate ground-layer atmospheric turbulence, improving image resolution in the visible over a 3'x3' field and increasing light concentration for spectroscopy. Ground layer compensation will be achieved by means of a UV (355nm) laser guide star (LGS), imaged at a nominal distance of 10km from the telescope, coupled to a Shack-Hartmann wave front sensor (WFS) and a bimorph deformable mirror. Unique features of SAM are: access to a collimated space for filters and ADC, two science foci, built-in turbulence simulator, flexibility to operate at LGS distances of 7 to 14 km as well as with natural guide stars (NGS), a novel APD-based two-arm tip-tilt guider, a laser launch telescope with active control on both pointing and beam transfer. We describe the main features of the design, as well as operational aspects. The goal is to produce a simple and reliable ground layer adaptive optics system. The main AO module is now in the integration and testing stage; the real-time software, the WFS, and the tip-tilt guider prototype have been tested. SAM commissioning in NGS mode is expected in 2009; the LGS mode will be completed in 2010.

The Laser Guide Star commissioned in 2007 at the WHT on La Palma is based on Rayleigh backscattering of a 515 nm beam provided by a diode pumped Q-switched doubled frequency Yb:YAG laser launched from behind the WHT secondary mirror. At the time the laser beam is focused at a distance of 15km above the telescope ground and its power just under 20W. With such a pulsed laser, careful fine tuning of the range gate system is essential to isolate the most focused part of the LGS and eliminate parts of the laser plume which would degrade the Shack-Hartmann spots and consequently AO correction. This is achieved by an electro-optic shutter using Pockels cells, triggered by a delay generator synchronised on the laser pulses, and by spatial filters. Images of 0.15" resolution in J and H bands, very close to expected performance, have been routinely taken as soon as the third and fourth commissioning runs. Here we show the performance of the range gate system as measured and improved over the successive commissioning runs, as well as the off sky and on sky calibration procedures of the LGS AO system.

ASSIST: The Adaptive Secondary Setup and Instrument STimulator is the test setup for the verification and calibration of three elements of the VLT Adaptive Optics Facility.; the Deformable Secondary Mirror (DSM) the AO system for MUSE and HAWK-I (GALACSI and GRAAL). In the DSM testing mode the DSM will be tested using both interferometry and fast wave front sensing. In full AO mode, ASSIST will allow testing of the AO systems under realistic atmospheric conditions and optically equivalent to the conditions on the telescope. ASSIST is nearing its final design review and in this paper we present the current optical and mechanical design of ASSIST. In this paper we highlight some of the specific aspects of ASSIST that we are developing for ASSIST.

At Dome C, Antarctica, the whole turbulence is reduced to a boundary layer of about 50 meters. WHITE is a project of an infrared survey based on a 2-m telescope using a ground-layer adaptive-optics instrument to obtain high angular resolution on a wide field of view. Simulation results obtained both analytically and from a numerical end-to-end approach are presented and then compared.

The goal of this project is to achieve exquisite image quality over the largest possible field of view, with a goal of a FWHM of not more than 0.3" over a square degree field in the optical domain. The narrow PSF will allow detection of fainter sources in reasonable exposure times. The characteristics of the turbulence of Mauna Kea, a very thin ground layer with excellent free seeing allows very wide fields to be corrected by GLAO and would make such an instrument unique. The Ground Layer AO module uses a deformable mirror conjugated to the telescope pupil. Coupled with a high order WFS, it corrects the turbulence common to the entire field. Over such large fields the probability of finding sufficiently numerous and bright natural guide sources is high, but a constellation of laser beacons could be considered to ensure homogeneous and uniform image quality. The free atmosphere seeing then limits the image quality (50% best conditions: 0.2" to 0.4"). This can be further improved by an OTCCD camera, which can correct local image motion on isokinetic scales from residual high altitude tip-tilt. The advantages of the OTCCD are not limited to improving the image quality: a Panstarrs1 clone covers one square degree with 0.1" sampling, in perfect accordance with the scientific requirements. The fast read time (6 seconds for 1.4 Gpixels) also leads to an improvement of the dynamic range of the images. Finally, the guiding capabilities of the OTCCD will provide the overall (local and global) tip-tilt signal.

We describe the current status of the SLODAR optical turbulence monitors, developed at Durham University, for support of adaptive optics for astronomy. SLODAR systems have been installed and operated at the Cerro Paranal and Mauna Kea observatories, and a third will be deployed at the South African Astronomical Observatory in 2008. The instruments provide real-time measurements of the atmospheric turbulence strength, altitude and velocity. We summarize the capabilities of the systems and describe recent enhancements. Comparisons of contemporaneous data obtained with SLODAR, MASS and DIMM monitors at the ESO Paranal site are presented.

We have made high order (32x32 subaperture) Shack-Hartmann wavefront sensor observations of binary stars with separations of approximately 20 arcseconds using the University of Hawaii 2.2 m telescope. We present preliminary results of a Slope Detection and Ranging (SLODAR) analysis of the data yielding measurements of turbulence strength, wind velocity and velocity dispersion as a function of altitude, with approximately 500 m vertical resolution. The aim of the investigation is to explore the validity of the Taylor frozen flow approximation and the implications for layer-oriented predictive AO reconstruction algorithms.

GLAS (Ground-layer Laser Adaptive optics System) provides a Rayleigh Laser Guide Star (LGS) upgrade to the existing NAOMI AO system at the 4.2-m William Herschel Telescope on La Palma. Installation of the GLAS upgrades commenced in 2006 with on-sky commissioning taking place from May 2007. Commissioning was very successful and AO correction was first observed during the August 2007 observing run. Here we present an overview of the opto-mechanical systems that have been installed and commissioned, including the LGS launch system, LGS safety systems and LGS Wave Front Sensor, concentrating on the integration of the various optical and optoelectronic components.

The Multi-conjugate Adaptive optics Demonstrator (MAD) has been developed by ESO, and installed at the Nasmyth focal plane of the Very Large Telescope Melipal at Cerro Paranal in Chile. Thanks to the multi-dimensional sensing and correction of MAD, the measurements recorded while the system is performing MCAO can be analyzed to retrieve the instantaneous characteristics of the turbulence seen from the focal plane of the telescope: seeing and turbulence profile. In this paper those measurements will be compared to the ones given by other tools at disposition at the focal plane: the guide probe and the active optics sensor, and at another location on the Paranal platform: DIMM and MASS.

Wavefront sensing and control is required throughout the mission lifecycle of large space telescopes such as James Webb Space Telescope (JWST). When an optic of such a telescope is controlled with both surface-deforming and rigidbody actuators, the sensitivity-matrix obtained from the exit pupil wavefront vector divided by the corresponding actuator command value can sometimes become singular due to difference in actuator types and in actuator command values. In this paper, we propose a simple approach for preventing a sensitivity-matrix from singularity. We also introduce a new "minimum-wavefront and optimal control compensator". It uses an optimal control gain matrix obtained by feeding back the actuator commands along with the measured or estimated wavefront phase information to the estimator, thus eliminating the actuator modes that are not observable in the wavefront sensing process.

An optical aperture synthesis telescope such as the LBT will suffer from phase errors unless the apertures are aligned to within a small fraction of a wavelength. A phase diversity wave-front sensor can measure phase errors brought by a misaligned aperture synthesis telescope. The Phase Diversity is formulated in the context of nonlinear programming where a metric is developed and then minimized. We here introduce a novel Genetic Algorithms (GAs), evaluate the different Zernike coefficients to obtain the wave-front error. The results of the computer simulations performed with simulated data including the effects of noise are shown for the case of random misalignment phase errors on each of three sub-telescope.

The Adaptive Optics Laboratory of the University of Victoria has build a LGS SH-WFS test bench for the Thirty-Meter-Telescope project and its AO system, NFIRAOS. The UVic AOLab has recently shown the ability to track Na profile induced aberrations while correcting for turbulence aberrations. The UVic AOLab has started the second phase of development of its LGS SH-WFS test bench. This next step consists in adding the Truth WFSs into the current bench design and in modeling and implementing the algorithms which blends the data coming from the variousWFSs. This paper shows the various components of the control architecture of NFIRAOS LGS wavefront sensing process. A first simulation shows the stability of the proposed control architecture and demonstrates that the DM is kept away from reproducing the LGS aberrations.

Sodium laser guide stars (LGSs) allow, in theory, full sky coverage, but have their own limitations. Variations of sodium layer altitude, thickness and atom density profile induce changing errors on wavefront measurements (LGS aberrations), especially with ELTs for which the LGS spot elongation is larger. In the framework of the Thirty-Meter-Telescope project (TMT), the AO-Lab of the University of Victoria (UVic) built a LGS-simulator test bed in order to assess the performance of new centroiding algorithms for LGS Shack-Hartmann wavefront sensors (SH-WFS). The principle of the LGS-bench is briefly reviewed. The closed-loop performances of the matched filter (MF) algorithm on laboratory 29x29 elongated spot images are presented and compared with the centre of gravity (CoG). The ability of the MF to track the LGS aberrations is successfully demonstrated. The UVic LGS-bench is not limited to SH-WFS and can serve as a LGS-simulator test bed to any other LGS-AO projects for which sodium layer fluctuations are an issue.

Large-aperture segmented primary mirror has been widely used in high-resolution space telescopes. In this paper, we concentrate on the wavefront sensing and control (WFS&C) methods for a segmented primary mirror comprising a central octagon and eight surrounding petals. As the wavefront errors have a wide dynamic range in amplitude and spatial frequency, a multistage wavefront control algorithm is proposed. The control process is divided to five steps to reduce the wavefront errors gradually. A simulation toolbox integrating multi-disciplinary software has been developed to verify our WFS&C algorithms. Simulation results give a good demonstration of the feasibility of our algorithms.

We present observations of the high-speed variations of the altitude of the telluric sodium layer. In this experiment we observed the Gemini-North sodium laser guide star from approximately 80 meters off-axis using the UH-2.2m telescope on Mauna Kea, Hawaii. Observations were made using an electron-multiplying camera at a rate of about 100Hz. The temporal power spectrum of the layer centroid follows a power law between 0.001 and 1Hz and we find that the exponent of the power law (α=-1.8) is similar to that found at lower temporal frequencies from lidar experiments. This data set taken with the lidar results shows that the power spectrum of the sodium layer mean altitude follows a simple power law over 5 orders of magnitude from 10^-4.5 Hz to 1Hz. The approach taken in this experiment is difficult due to telescope jitter in any of the three telescopes (Gemini-N, Gemini-N LGS launch telescope, or from the observing UH2.2m) and atmospheric tip/tilt wave front aberrations. We circumvented these problems by analyzing the differential motion between two distinct features that appeared in the sodium layer during that night.

We present a concept to perform low-order wavefront sensing in multi-laser guide star adaptive optics systems operating using a large format NIR detector with windowing capability with near diffraction limited or partially corrected NGS tip-tilt stars with time varying Strehls. Most contemporary adaptive optics systems in development for large telescopes, viz., the next VLT adaptive optics facility that serves as a pathfinder to the European ELT, Gemini MCAO, W. M. Keck observatory's Next Generation Adaptive Optics (NGAO) System, The Large Binocular Telescope and the Thirty Meter Telescope's NFIRAOS are multi-laser guide star systems that provide AO correction over a large field. In such systems even faint tip-tilt (TT) stars image are characterized by either a well corrected (MOAO case) or at least a partially corrected (MCAO or GLAO case) diffraction limited core due to high order sharpening by the LGS WFS. In such a regime of low-order sensing one could envisage using pixels as field stops and choosing a appropriate plate scale to minimize the sky background. Simulations are used to predict the performance of such a sensor when guiding on point sources and on extended objects of varying brightness and for different levels of high order correction. The parameter space explored includes tip-tilt and tip-tilt, focus and astigmatism (TTFA) sensor performance for various plate scales, TT sensor performance vs. level of high order correction (TT star Strehl) and TT sensor performance vs. TT object size for a given detector noise, gain and a simple centroiding algorithm. Due to small sky noise contribution at plate-scales le 100 mas/pixel, the optimum low-order wavefront sensor plate scale is found to be 80-100 mas/pixel (3×-4× λ/d in J- and H- bands) for the Keck NGAO system.

We investigate the effect of atmospheric phase and scintillation anisoplanatism on the measurement of the local gradient of the wavefront using a Hartmann-Shack type wavefront sensor. This is accomplished by simulation of the imaging process, starting with 100 synthetic, anisoplanatic phase and scintillation screens that were computed for several viewing angles and that correspond to Fried parameters of 7 and 12 cm. The screens are calculated using the approximated turbulence profile at the site selected for the ATST, Haleakala on Maui, Hawaii, USA. Phase aberrations are propagated through the wavefront sensor, considering each viewing angle in each subaperture (of adjustable size) separately. The point spread functions (PSF) are calculated for the viewing directions as well as specified (and adjustable) pixel scale in the sensor camera. Subsequently, these PSFs are convolved with a typical wavefront sensor lock structure of solar AO systems, an image of solar granulation. The cross-correlation peak of the thus created anisoplanatic subimages is finally used to find the local gradients of the wavefront. We find that phase anisoplanatism contributes significantly to the measurement error of a Hartmann-Shack type wavefront sensor, whereas we cannot detect a notable increase thereof from scintillation anisoplanatism in the subaperture when using a cross-correlating algorithm to find the gradient of the incident wavefront.

Adaptive optics (AO) systems of next generation optical ground telescopes will employ laser guide stars (LGS) to achieve wide sky coverage. In these systems the mesospheric sodium layer at ~ 90 km height is excited by means of laser-induced fluorescence of the Na I D₂ resonance hyperfine transmission. The finite thickness of sodium layer, and temporal variations in its density structure, result in LGS that are elongated and have internal structure that varies with time. This degrades the performance of the AO system due to degeneracy between effects of atmospheric and sodium layer variations. In order to quantify this and assess the impact on future extremely large telescopes such as the Thirty-Meter Telescope (TMT), measurements are needed of the density distribution of the sodium layer with high spatial and temporal resolution. We describe the design of a new lidar experiment to investigate the spatio-temporal power spectra of the Na-variations at frequencies as high as 50 Hz. This system employs a 5 W pulsed laser and a 6 m liquid mirror telescope, which provide sufficient sensitivity for high-resolution studies. The transmitter is a YAG-pumped dye laser, with an optical collimation system that allows the beam divergence to be controlled over a range from diffraction-limited to several arcmin. This will also allow the investigation of saturation effects, important for the next generation high power LGS systems. Backscattered photons will be collected at the prime focus using four high-efficiency photomultiplier detectors and a fast counting system. The resulting system will provide vertical density profiles with a spatial resolution as small as 2 m.

A kind of Multiple-Detecting-Branch (MDB) Shack-Hartmann wavefront sensor (SHWFS) with extremely large number of subapertures, in which the pupil is split into spatially several branches by a beam splitter and each branch is detected by a SHWFS with less subapertures comparatively, is proposed to use for the wavefront sensing of the adaptive optics system for extremely large telescope. All the signals from the CCDs of SHWFS must be synchronized by the specially developed hardware system. There are the angular error of the beam splitter and the circum-optical-axis rotary of CCDs besides of the error of the conventional SHWFS. In this paper, the principle of the MDB SHWFS is introduced and its errors are analyzed. The simulation and experimental results show that this kind of MDB SHWFS can be used to measure effectively the wavefront aberration of the total pupil.