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.