The purpose of this paper is to report on new adaptive optics (AO) developments at the W. M. Keck Observatory since the 2002 SPIE meeting. These developments include continued improvements to the natural guide star (NGS) facilities, first light for our laser guide star (LGS) system and the commencement of several new Keck AO initiatives.

Three sets of sky tests have been conducted at the Starfire Optical Range with a continuous-wave, single-frequency, 20-W laser in preparation for a 50-W facility-class laser. Brightness measurements were made of the sodium guidestar produced with and without adaptive optics (AO) correction to the outgoing laser beam when it was either linearly or circularly polarized. Correcting for the transmission of our V filter at the sodium wavelength, a circularly polarized laser beam of 12 W out the telescope produced a guidestar of V=7.1 (1015 ph/s/cm² at the top of the telescope). In general, a circularly polarized beam produces a guidestar between 75 and 100% brighter than a linearly polarized beam, indicating a significant degree of optical pumping of the sodium D2-line magnetic sublevels. However, guidestars produced with beams launched with tip-tilt correction only were 11% brighter than with beams launched with full AO correction. From deconvolved images of the guidestar taken with the 3.5-m telescope, the smallest spot, produced from a beam with 8.5 W of power out the telescope, circular polarization, and launched closed loop, had a Gaussian FWHM of 0.85 arcsec, or 38 cm at an altitude of 92 km. This corresponds to a peak Gaussian intensity of 3.8 mW/cm².

The Multiple Mirror Telescope (MMT) adaptive optics system (MMT-AO) has been operated in a campaign mode for the last two years. In total seven runs, each lasting about two weeks, have been carried out. During these observational runs a large amount of data have been collected. These data allow us to draw some preliminary conclusions about the overall system performances. In this paper we discuss in detail the achieved performances of the MMT-AO system which is equipped with the first adaptive secondary ever developed. The performances are examined both in terms of number of corrected modes and control bandwidth achieved. We also discuss our attempts to improve the system calibration. This is done by modulating the internal slope offsets while the system is operating in closed loop on the sky.

Solar adaptive optics has become an indispensable tool at ground based solar telescopes. Over the last few years several solar adaptive optics systems have been deployed at major ground based solar telescopes. These systems enable diffraction limited observations of the sun for a significant fraction of the available observing time at these telescopes. New ground breaking scientific results have been achieved with solar adaptive optics. This paper summarizes the recent progress in the field of solar adaptive optics.

In April and August ’03 two MACAO-VLTI curvature AO systems were installed on the VLT telescopes unit 2 and 3 in Paranal (Chile). These are 60 element systems using a 150mm bimorph deformable mirror and 60 APD’s as WFS detectors. Valuable integration & commissioning experience has been gained during these 2 missions. Several tests have been performed in order to evaluate system performance on the sky. The systems have proven to be extremely robust, performing in a stable fashion in extreme seeing condition (seeing up to 3”). Strehl ratio of 0.65 and residual tilt smaller than 10 mas have been obtained on the sky in 0.8” seeing condition. Weak guide source performance is also excellent with a strehl of 0.26 on a V~16 magnitude star. Several functionalities have been successfully tested including: chopping, off-axis guiding, atmospheric refraction compensation etc. The AO system can be used in a totally automatic fashion with a small overhead: the AO loop can be closed on the target less than 60 sec after star acquisition by the telescope. It includes reading the seeing value given by the site monitor, evaluate the guide star magnitude (cycling through neutral density filters) setting the close-loop AO parameters (system gain and vibrating membrane mirror stroke) including calculation of the command-matrix. The last 2 systems will be installed in August ’04 and in the course of 2005.

We report here the preliminary results obtained with the multi-conjugate adaptive optics (MCAO) system at the Dunn Solar Telescope (DST/NSO MCAO) and the optical setup and performances are presented in more details in Moretto et al. in this proceeding. This system relies on the tomography technique, in which three WFS are used, each of them coupled to extended images of the Sun’s granulation and/or sunspots, to retrieve a 3D measurement of the turbulent volume in order to command the two DMs. We used a 5x5 subaperture Shack-Hartmann with cross correlation applied on three selected guiding regions - 18" wide- within the 1.25' full FOV. We also report on the estimation of turbulence distribution and the future MCAO performances based on a separate tomographic wavefront sensing experiment using the Dunn Solar Telescope adaptive optics system. In addition, we obtained estimates of the turbulence distribution. The results from this article provides an important step forward for building a full solar multi-conjugate adaptive optics system for the Dunn Solar Telescope and in the long term for the future 4 meter ATST telescope.

In this paper we evaluate the on-sky performance of Altair, the facility adaptive optics instrument at the Gemini North telescope. We describe the method for doing this on-sky evaluation, which includes: 1) the choice of suitable stellar fields for PSF observations that must cover a range of guide star magnitudes and angular separations from the guide star; 2) the observation strategy and data reduction pipeline; and 3) the PSF database from which the performance results are queried. The database stores observatory system parameters and performance observations such as FWHM, Strehl, encircled energy, wave front sensor flux, as well as coherence length (r_o) and outer scale (L_o) of the turbulence measured in closed loop and therefore coincident with the focal plane observations of the telescope. From the database we derive 20 to 24% Noll efficiency of the system and an estimated distribution of effective turbulence height above the summit to be 3.3 ± 0.6km. The performance evaluation strategy used on Altair is quite general and could be used for other adaptive optics systems.

NAOMI is the AO system of the 4.2-m William Herschel Telescope on La Palma. It delivers near-diffraction-limited images in the IR, and a significantly improved PSF at optical wavelengths. The science cameras currently comprise an IR imager (INGRID), an optical integral-field spectrograph (OASIS) and a coronagraph which may be placed in the light path to either instrument. 19 science programmes were observed during 2002-3. Observing overheads are small, with as much as 60% of the night spent integrating on science targets. In late 2004 this year, the WFS will be equipped with a low-noise L3 CCD, giving a gain of a factor of 2 in S:N for faint guide stars. A Rayleigh laser guide star is under development, with first light expected summer 2006, providing a unique facility: AO-corrected optical integral-field spectroscopy anywhere on the northern sky.

The UnISIS adaptive optics system is now completed and ready for science observations. We describe the experience we have gained in building and using the system, and we give a preview of one new science goal: the use of Gaussian aperture pupil masks for high-contrast imaging of companion objects near bright stars. A key aspect of the UnISIS design is the simultaneous use of two wavefront sensors, one for natural stars and the other for the laser guide star. We demonstrate the performance of this calibration system with results from on-the-bench tests. We describe several practical aspects of observing at Mt. Wilson including our ability to predict the nights of best seeing with weather data available on-line. We also show how the laser guide star return signal is enhanced by observing at large zenith angles and compare this to Rayleigh scattering models.

We present the status of the 1st generation of adaptive optics systems in operation and in construction at ESO. We introduce the 2nd generation of AO facilities planned to be developed in the coming years for the VLT and describe the corresponding enabling technology R&D program. The concept of an Adaptive facility with multi-LGS and a Deformable Secondary at one the VLT Unit Telescope is introduced. Status and roadmap of ESO simulation tools and preliminary concepts for OWL Adaptive Optics as well as preliminary R&D plan are given.

The Natural Guide Star (NGS) Adaptive Optics System at the MMT Telescope (MMTAO) on Mt. Hopkins in Southern Arizona is the first in the world to use the secondary mirror as the correcting deformable mirror. Its 2.0 mm thin shell mirror, whose shape is controlled by 336 voice coil actuators, allows for nearly maximum throughput of light into the science camera. With several more deformable secondary mirrors coming online in the next few years, the lessons learned building, characterizing and operating the MMT Adaptive Optic System has proven to be quite valuable. These lessons will be discussed as well as future plans for the MMTAO System.

High resolution spectroscopy made an important step ahead 10 years ago, leading for example to the discovery of numerous exoplanets. But the IR did not benefit from this improvement until very recently. CRIRES will provide a dramatic improvement in the 1-5 micron region in this field. Adaptive optics will allow us increasing both flux and angular resolution on its spectra. This paper describes the adaptive optics of CRIRES, its main limitations, its main components, the principle of its calibration with an overview of the methods used and the very first results obtained since it is installed in the laboratory.

The paper describes the single conjugate AO system called WLBT to be mounted at LBT in late summer 2004. The WLBT is part of the Acquisition, Guiding & Wavefront sensing unit (AGW) attached to the front bent Gregorian foci derotator. The two key features of this system are the use of a pyramid wavefront sensor with variable sampling between 30x30 and 5x5 sub apertures plus the use of an adaptive secondary mirror having 672 actuators as wavefront corrector. The AO system is mainly working as atmospheric disturbance correction system in the near infrared (J,H and K band). However due to the large number of actuators and sub apertures, it can obtain good performance even in R and I band. The paper reports about development and integration of the system final unit in the lab. Then some initial tests aimed to do a system characterization are reported. The results we obtained are used to give an estimation of the performance that the system can reach at the telescope in terms of limiting magnitude.

The European Southern Observatory together with external research Institutes is building a Multi-Conjugate Adaptive Optics Demonstrator (MAD) to perform wide field of view adaptive optics correction. The aim of MAD is to demonstrate on the sky the feasibility of the MCAO technique and to evaluate all the critical aspects in building such kind of instrument in the framework of both the 2nd generation VLT instrumentation and the 100-m Overwhelmingly Large Telescope (OWL). The MAD module will be installed at one of the VLT unit telescope in Paranal to perform on-sky observations. MAD is based on a two deformable mirrors correction system and on two multi-reference wavefront sensors capable to observe simultaneously some pre-selected configurations of Natural Guide Stars. MAD is expected to correct up to 2 arcmin field of view in K band. MAD has just started the integration phase which will be followed up by a long period of testing. In this paper we present the final design of MAD with a brief report about the status of the integration.

In this article, we present the VLT second generation instruments and we summarize the concept and capabilities of the Very Large Telescope (VLT) Adaptive Optics (AO) Facility. This Facility, composed mainly of a deformable secondary mirror and four laser guide stars (LGSs), aims at providing an adaptive optics infrastructure to feed multiple instruments. These instruments can range from wide or narrow field visible light correction (for example MUSE, X-Shooter) to wide field infra-red correction (Hawk-I, possibly K-MOS) and it could also provide a high Strehl mid-infrared system. In this article we analyze the performance of this AO facility in these various modes of operation.

We present the optical setup and properties of the second-generation adaptive optics (AO) for the 1.5 m solar telescope GREGOR. The system will consist of a high order AO system correcting about 200 degrees of freedom on-axis at a bandwith of 200 Hz and a multi-conjugate (MCAO) extension that uses one additional deformable mirror to correct the low-order aberrations across a field of one arcminute at a bandwidth of 50 Hz. Diffraction limited observations will be possible for seeing better than 1.2 arcsec. First light is expected in 2007.

We describe SPLASH (Sky Projected Laser Array Shack-Hartmann) which is a method of laser guide star (LGS) wavefront sensing with reduced focal anisoplanatism (FA). We present the results of a semi-theoretical analysis and a semi-geometrical simulation of SPLASH, allowing a direct comparison between SPLASH and a conventional laser guide star system. We show that SPLASH is significantly less susceptible to focal anisoplanatism than a conventional LGS.

We report in this paper on the current activities of the Laser Guide Star group at ESO. We are building the Laser Guide Star Facility on the VLT UT4, we are pushing new technologies in view of multiple LGS and future ELT LGS-AO systems. We are studying new LGS propagation/sensing schemes, to get rid of the LGS cone effect. We are also fostering in member states countries the development of fast sensors to deal with pulsed lasers atmospheric layer sensing.

The PARSEC laser system is designed for the VLT Laser Guide Star Facility to deliver a high power cw laser beam at 589nm, in order to create an artificial guide star in the mesospheric Sodium layer. The laser consists of a resonant, dye based power amplifier which is injection seeded with 589nm, single frequency radiation from a master oscillator. We report on the performance of the system both during the European Acceptance tests, and that which has been achieved in the laboratory. The maximum power we have obtained amounts to 20W cw laser light in a single mode and a single frequency at 589nm. With a beam quality of M² of 1.05-1.15 and a long term stability without manual intervention, the laser suits all the demands for operation at the VLT.

The next generation ground based telescopes deploy their full potential in terms of resolution only with Adaptive Optics (AO). A limiting factor for such systems is the sky coverage with natural guide stars. A way to overcome this problem is a artificial star, i.e. laser guide star (LGS) generated in the sodium layer of the mesosphere at an height of approximately 90km-100km. Sensing the wave front of such a LGS, whose photons are collected by a next generation ground based telescope up to 100m pupil diameter leads to new problems. They are related to the finite distance of the altitude where the artificial star forms with respect to the telescope entrance pupil. We present a new wave front sensing concept to overcome this problem and we show first results of an open loop experiment done on sky. Measurements have been carried out November 2003 with the Rayleigh laser of the University of Durham at the WHT in La Palma as a result of collaboration between MPIA and the AO group of the University of Durham. The geometry of the LGS created in 4km altitude with respect to the 4m aperture of the WHT scales by a factor 1:25 with a sodium LGS at 100km and a telescope with 100m entrance pupil diameter.

Coherent Technologies, Inc. (CTI) is developing the first commercial solid-state sodium beacon laser guidestar (LGS): a critical step towards addressing the need of the astronomy adaptive optics (AO) community for a robust turn-key commercial LGS that can be upgraded for different observatory facilities and for different AO formats - including multi-conjugate AO (MCAO) and future extra-large telescopes. The LGS that is currently being developed will be a 14 W single beacon system to be installed on the center section of the Gemini North telescope in Fall 2004. This paper describes the Gemini North LGS requirements, the design of the laser with design trades against other LGS architectures; the functionality of the automated remote laser control system; latest size, weight, power, and performance data; and the current status of the program.

We report on the development of a 50-W, continuous-wave, sodium wavelength guidestar excitation source for installation on the azimuth gimbal structure of the 3.5-m telescope at the Starfire Optical Range. The laser is an all solid-state design employing two diode-pumped Nd:YAG sources operating at 1064 and 1319 nm that are combined to generate 589-nm radiation using a lithium triborate non-linear crystal. Key features of the system include single-frequency, injection-locked high-power oscillators, a doubly resonant sum frequency generator cavity, a short-term 10 kHz wide 589 nm spectrum, excellent beam quality and power stability, and turn-key operation using computer control and diagnostics. The laser beam is projected from the side of the 3.5-m telescope. A novel elevation beam dither approach is employed to determine range to the centroid of the guidestar formed in the column of mesospheric sodium and maintain focus of the wave front sensor.

A demonstration of tomographic wavefront sensing has been designed, fabricated, and tested. The last of the initial testing of the dynamic refocus system at the 61" telescope on Mt. Bigelow, Arizona is presented, along with the first results from the system after its transfer to the 6.5 m MMT on Mt. Hopkins, Arizona. This system consists of a laser beam projector, and a wavefront sensor at the telescope's Cassegrain focus. The projector transmits 5 pulsed 532 nm beams in a regular pentagon of 2 arcminutes diameter from behind the telescope's secondary mirror that in good seeing can yield sub-arcsecond beacons over a 20-30 km altitude range. The wavefront sensor incorporates a dynamic refocus unit to track each returning laser pulse, and a multiple laser beacon Shack-Hartmann wavefront sensor using a novel substitute for the traditional lenslet array. A natural guide star wavefront sensor was also fielded to collect ground-truth data to compare with wavefronts reconstructed from the laser wavefront sensor measurements. All of the subsystems were shown to work, but bad weather ended the testing before the final data could be collected.

For applications like direct imaging detections of Exo-Planets from the ground e.g. in the CHEOPS project, extreme adaptive optics (XAO) systems using DMs with > 1000 actuators and correction frequencies of ~2kHz are proposed to be used in combination with coronographic devices. If the XAO and science channel work at the same wavelength it is a natural idea to combine the coronograph with the XAO's beam splitter (BS) to make use of the light that would otherwise just be lost. However, the location of the BS in the focal plane and the severe field limitation of the AO by a small (~0.3'') aperture in the focal plane imposes a spatial filtering on the wavefront sensor signal. In this paper, we examine the effect of the spatial filter on the "AO control radius" and the Strehl ratio provided by the system in a semi-analytical way, numerical simulations for various wavefront sensor types and a laboratory verification experiment.

Optimization of a Shack-Hartmann based WFS is proposed for XAO systems. Both aliasing effects and noise propagation issues is investigated in order to optimize the WFS device. In particular a new estimator of the spot position is proposed and characterized both analytically and using end-to-end simulations. Analytical expressions of the slope measurement errors is derived and the gain brought by our new Weighted Center of Gravity estimator is quantified.

The new L3 Technology CCDs from E2V combine sub-electron read noise with high pixel rates. This makes them ideal candidates for wavefront sensing. ING's NAOMI adaptive optics instrument is currently limited by the readout noise of its wavefront sensor CCDs. Upgrading to L3 detectors has the potential to give a large increase in performance; simulations suggest a 2 magnitude improvement to the guide star limit. At ING we have explored the behaviour of various L3 devices in applications ranging from fast photometry, fast spectroscopy through to wavefront sensing. The investigations have been done using our own cryogenic cameras containing L3 devices coupled to an SDSU controller. An integral Peltier packaged CCD60 has also been purchased specifically for the WFS upgrade. This paper describes the progress we have made to date on the L3 wavefront sensor upgrade and our future plans for its use with a Rayleigh laser beacon.

A new wavefront sensor based on the pyramid principle is being built at MPIA, with the objective of integration in the Calar Alto adaptive optics system ALFA. This sensor will work in the near-infrared wavelength range (J, H and K bands). We present here an update of this project, named PYRAMIR, which will have its first light in some months. Along with the description of the optical design, we discuss issues like the image quality and chromatic effects due to band sensing. We will show the characterization of the tested pyramidal components as well as refer to the difficulties found in the manufacturing process to meet our requirements. Most of the PYRAMIR instrument parts are kept inside a liquid nitrogen cooled vacuum dewar to reduce thermic radiation. The mechanical design of the cold parts is described here. To gain experience, a laboratory pyramid wavefront sensor was set up, with its optical design adapted to PYRAMIR. Different tests were already performed. The electronic and control systems were designed to integrate in the existing ALFA system. We give a description of the new components. An update on the future work is presented.

We present the development of silicon monolithic arrays of 60 photon-counters (SPADA, Single-Photon Avalanche Diode Array) for the visible. The SPADA system is suitable for state-of-the-art Adaptive Optics operations and Fast Transient image acquisitions, at quite a fraction of the current cost of imaging arrays. The fabricated solid-state photon counters are rugged, easy to be integrated in the optical system. They are free from readout noise and provide very fast frame-rates (>10kHz, for visible corrections) and nanosecond electronic gating (for ranging the up-going laser beam). The detection head has been integrated into an optomechanical system suitable for alignment and focusing in available astrophysics telescopes. The detection electronics includes an integrated Active Quenching Circuits for each pixel of the array. The real-time data-processing board is implemented into FPGA and DSP and is configurable for dealing with different applications: the extraction of the curvature wavefront for AO applications, and the acquisition and processing of two-dimensional images with fast frame rate. A remote host computer controls all the SPADA blocks and uploads the processed information and images. We report the optical and electrical characterization of the detectors and the associated electronics.

The Shack-Hartmann wavefront sensor operates by subdividing the complex field in the aperture plane of the telescope with a lenslet array and forming low resolution images of the object. An alternative wavefront sensing scheme can be derived from placing a lenslet array at the focal plane of the aperture and forming low resolution images of the aperture. This arrangement can be viewed as the generalisation of the pyramid sensor and enables direct comparisons of the pyramid sensor with the Shack-Hartmann sensor. In particular, in this paper the performance of the reconstructor of the two sensors is investigated. Simulation results demonstrate that the lenslet array at the focal plane has equivalent performance to the Shack-Hartmann sensor in open loop when no modulation is applied to the lenslet array. However, when the array is modulated in a manner akin to the pyramid sensor, subdivision at the focal plane provides a significantly better wavefront estimate than the Shack-Hartmann sensor.

It is shown that one can build a 100m-class wavefront sensing with today existing components and that 100m-scale wavefront sensing of layers in the atmosphere is also possible with today existing technology

In the framework of the Multi Conjugate Adaptive Optics technique several new ideas have been proposed in the last new years to improve the quality of the correction by using in the most possible efficient way the light coming from the references. The Layer Oriented approach, based on the usage of pupil plane wavefront sensors such as the pyramid, is using the superimposition of the light coming from several references at the level of the detector in order to increase the SNR and is using just the signal which is needed to drive loops indipendently tuned (in term of spatial and temporal sampling) to different altitudes. The Multiple Field of View technique proposes to increase the field of view of the detectors conjugated to altitudes close to the ground (where the pupil superimposition is high), thus increasing the probability to find suitable references and consequently the equivalent photon density on the metapupil. The Multiple Resolution technique is instead based on the idea of somehow increasing the depth of focus of the detectors in order to maximize the volume of atmosphere sensed by each detector even by using large Field of Views. Ground layer MCAO has also been proposed as a technique to accomplish only partial correction over a wide field of view and some on sky experiments are going to be exploited on the sky. From time to time there might be the impression that we arrived to a kind of a limit for the efficiency of the systems, considering that the light is limited by the FoV that cannot be increased indefinitely, but this might be a by product of the fact to look at the wavefront reconstruction in a linear fashion. In fact, it has been already shown in the past that it is possible to drive additional DMs by using the signal coming from detectors not conjugated to them, but this is accomplished by using a quadratic reconstruction. Furthermore, more recently, the idea of using the signal coming from an anular region surrounding the scientific field of view to improve the correction in the centre has also been suggested and again the signal has to be treated in a quadratic way. All these considerations suggest that there is still room for improvements at the expense of giving up on some conventional approaches to treat these problematics.

Current and future large telescopes depend critically on laser guide star adaptive optics (LGS AO) to achieve their scientific goals. However, there are still relatively few scientific results reported from existing LGS AO systems. We present some of the first science results from the Lick Observatory sodium beacon LGS AO system. We achieve high sensitivity to light scattered in the circumstellar enviroment of Herbig Ae/Be stars on scales of 100-200 AU by coupling the LGS AO system to a near-infrared (J,H,K_s bands) dual channel imaging polarimeter. We describe the design, implementation, and performance of this instrument. The dominant noise source near bright stars in AO images is a "seeing halo" of uncorrected speckles, and since these speckles are unpolarized, dual-channel polarimetry achieves a significant contrast gain. Our observations reveal a wide range of morphologies, including bipolar nebulosities with and without outflow-evacuated cavities and disk-mediated interaction among members of a binary. These data suggest that the evolutionary picture developed for the lower-mass T Tauri stars is also relevant to the Herbig Ae/Be stars, and demonstrate the ability of LGS AO systems to enhance the scientific capabilities of even modest sized telescopes.

In this paper we describe the operational strategy and performance of the Keck Observatory laser guidestar adaptive optics system, and showcase some early science verification images and results. Being the first laser guidestar system on an 8-10 m class telescope, the Keck laser guidestar adaptive optics system serves as a testbed for observing techniques and control algorithms. We highlight the techniques used for controlling the telescope focus and wavefront sensor reference centroids, and a wavefront reconstructor optimized for use with an elongated guidestar. We also present the current error budget and performance of the system on tip-tilt stars to magnitude R=17. The capability of the system to perform astronomical observations is finally demonstrated through multi-wavelength imaging of the Egg proto-planetary nebula (CRL 2688).

Sky coverage is an important item for a large number of techniques using stars as a reference, for example as guide stars for Adaptive Optics or for phase referencing in Interferometry. Models of the stellar distribution within our galaxy allow for reasonable estimates of the sky coverage under certain conditions, but these models do not give the detailed description that can only be obtained using observations. The newest generation star catalogues, like the USNO-B1.0 catalog in the visible wavelength band and the 2MASS catalog in the near-IR enable the exact determination of the sky coverage for a given requirement and location on the sky. Based on the above two catalogs the sky coverage as a function of parameters like limiting magnitude, number of guide stars and color was determined as a function of the location. In the context of the Multi Unit Spectroscopic Explorer (MUSE), a second generation instrument for the VLT which is currently being developed, the sky coverages for a number of potential targets--both progenitors of normal nearby galaxies at very high redshift, as found in deep fields like HDF-South and FORS deep field as well as nearby normal, starburst and interacting galaxies--were determined as illustrating examples.

Since the discovery of Dactyl orbiting around Ida by the Galileo spacecraft in 1993, over twenty-five binary asteroid systems have been discovered using radar, direct imaging and Adaptive Optics observations. Asteroidal moon discoveries dramatically increased with the advent of this last technique on ground based telescopes. Our group focuses on the search and study of double asteroids in the main-belt, in the Trojan population and beyond Neptune's orbit. We have been using several of the AO systems available (Lick-3m, Palomar-5m, VLT-8m, Keck-10m) and related techniques such as Appulse and Laser Guide Star observations to broaden the sample of asteroids observed from the main-belt out to the Kuiper Belt. We will present a quality comparison between various techniques and different AO systems with NGS and will detail our first successful observations with the Lick LGS system. Precise orbital elements of the secondary can be determined by multiple observations spanning large periods of time (several months). Our group developed a method to predict the ephemeris of a secondary companion. Without any assumptions, this method, tested successfully on 22 Kalliope and 121 Hermione binary systems, leads to the direct determination of important physical parameters of the targets, such as their mass and the interior structure, as well as gives direct insights on their formation processes that may be otherwise only be speculated on from spacecraft mission flybys.

The Natural Guide Star Adaptive Optics (NGS AO) system for the MMT Observatory is currently the only AO system in the world that uses a deformable secondary mirror to provide wavefront correction. This approach has unique advantages in terms of optical simplicity, high throughput and low emissivity. Here we present selected scientific results from the past year and a half of operation. Research with the AO system ranges from small scale structure around planetary nebulae, low mass stellar systems in the near IR, through to nulling interferometry in the mid infra-red.

As adaptive optics (AO) matures, it becomes possible to envision AO systems oriented towards specific important scientific goals rather than general-purpose systems. One such goal for the next decade is the direct imaging detection of extrasolar planets. An "extreme" adaptive optics (ExAO) system optimized for extrasolar planet detection will have very high actuator counts and rapid update rates - designed for observations of bright stars - and will require exquisite internal calibration at the nanometer level. In addition to extrasolar planet detection, such a system will be capable of characterizing dust disks around young or mature stars, outflows from evolved stars, and high Strehl ratio imaging even at visible wavelengths. The NSF Center for Adaptive Optics has carried out a detailed conceptual design study for such an instrument, dubbed the eXtreme Adaptive Optics Planet Imager or XAOPI. XAOPI is a 4096-actuator AO system, notionally for the Keck telescope, capable of achieving contrast ratios >10⁷ at angular separations of 0.2-1". ExAO system performance analysis is quite different than conventional AO systems - the spatial and temporal frequency content of wavefront error sources is as critical as their magnitude. We present here an overview of the XAOPI project, and an error budget highlighting the key areas determining achievable contrast. The most challenging requirement is for residual static errors to be less than 2 nm over the controlled range of spatial frequencies. If this can be achieved, direct imaging of extrasolar planets will be feasible within this decade.

The nascent field of planet detection has yielded a host of extra-solar planet detections. To date, these detections have been the result of indirect techniques: the planet is inferred by precisely measuring its effect on the host star. Direct observation of extra-solar planets remains a challenging yet compelling goal. In this vein, the Center for Adaptive Optics has proposed a ground-based, high-actuator density extreme AO system (XAOPI), for a large (~10 m) telescope whose ultimate goal is to directly evidence a specific class of these objects: young and massive planets. Detailed system wave-front error budgets suggest that this system is a feasible, if not an ambitious, proposition. One key element in this error budget is the calibration and maintenance of the science camera wave front with respect to the wave-front sensor which currently has an allowable contribution of ~ 5 nanometers rms. This talk first summarizes the current status of calibration on existing ground-based AO systems, the magnitude of this effect in the system error budget and current techniques for mitigation. Subsequently, we will explore the nature of this calibration error term, it’s source in the non-commonality between the science camera and wave front sensor, and the effect of the temporal evolution of non-commonality. Finally, we will describe preliminary plans for sensing and controlling this error term. The sensing techniques include phase retrieval, phase contrast and external metrology. To conclude, a calibration scenario that meets the stringent requirement for XAOPI will be discussed.

The proposed Giant Magellan Telescope (GMT) has a number of features that are well-suited to the task of imaging extrasolar planets in nearby star systems. The principal aid to this task is the large clear aperture segments which are relatively easy to apodize. This paper considers the methods currently envisaged to be of practical use for the task. In addition to star and planet fluxes, exoplanet imaging is dependent on aperture, throughput, bandwidth, beamwidth (FWHM), Strehl ratio (SR), and halo structure. Adaptive optics systems increase the SR, simultaneously dropping the residual scattered halo. This reveals the diffracted halo, which now becomes the limiting factor. Apodization reduces the diffracted halo, but at a cost in terms of throughput and a corresponding increase in photon noise. Since the best known ideal apodizations also have very low throughputs, they are not the best choices for ground-based exoplanet imaging. In addition, the ultra-low diffracted halos from these apodizations provide no benefit below the residual scattered halo, which is not helped by apodization. We consider instead a family of apodizations that have sufficiently dark diffracted halos, while retaining relatively high throughputs. One form of apodization can be applied to the GMT pupil using replicated apodization of individual segments, providing a low-halo survey mode that is high throughput and matched to the AO system. Since the reduced halo from the apodized segments only allows high-contrast detection to within a few λ/D_segment of the star, the single segment methods are limited by the segment size. We also consider the potential for apodizing the full aperture for high contrast at a few times λ/D_full through the use of an applied phase pattern, using either the adaptive secondary or a separate phase mask. We conclude that the phase mask method offers the best advantage for S/N since it does not lose light like the apodization schemes. However, it does have a restricted azimuthal search area, requiring multiple exposures to complete a survey. It appears to be the clearly best method for examining the exoplanet once discovered. It should be possible to apply offsets to the GMT's adaptive secondary to achieve constrasts of 10^-5 at 2xFWHM (27 mas at 1.65 μm, 80 mas at 5 μm) and 10^-6 at 3xFWHM (42 mas at 1.65 μm, 200 mas at 5 μm).

We discuss data reduction techniques and results from the Simultaneous Differential Imager (SDI) implemented at the VLT (Lenzen et al. 2004a) and the MMT. SDI uses a quad filter to take images simultaneously at 3 wavelengths surrounding the 1.62 μm methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be attenuated by a factor of >10². Non-trivial data reduction tools are necessary to pipeline the simultaneous differential imaging. Here we discuss a custom algorithm implemented in IDL to perform this reduction. The script performs basic data reduction tasks but also precisely aligns images taken in each of the filters using a custom shift and subtract routine. In our commissioning runs at the VLT and MMT, we achieved contrasts up to a factor of 45000 (ΔH=11.7) at a separation of 0.6" from the primary star. With this degree of attenuation, we should be able to image a 2-4 Jupiter mass planet at 5 AU around a 30 Myr star at 10 pc. We believe that our SDI images are the highest contrast astronomical images ever made from ground or space.

In PSFs obtained by AO systems, a cloud of speckles is surrounding the central diffraction core. These speckles don't average in time, and are extremely difficult to calibrate by the observation of a reference star. This "speckle noise" is setting the detection limit of faint companions around bright stars far above the photon noise. Speckles are coherent with the central diffraction core of the PSF, while a faint companion is not. By inducing interferences between the speckle cloud and a reference wave extracted from the central core of the PSF, it is possible to take advantage of this fundamental difference to identify and subtract the speckles. A time-variable phase delay is introduced in the reference wave in order to rapidly modulate the intensity of the speckles. The amplitude of this modulation leads to an accurate measure of the speckle intensity, which can then be subtracted to the image. This technique, which is compatible with spectroscopy, allows efficient detection of companions about 1000 times fainter than the speckles, and is especially attractive for exoplanet searches. The same technique can also be used on interferometers.

A end-to-end model of an Extreme Adaptive Optics system developed is the framework of the project VLT-PF is presented. The different components are exposed with their specificities. Several AO and XAO issues are discussed like scintillation, vibration and calibration effects among others. A full simulation of an XAO system coupled to a coronagraph and designed to detect faint companion in the vicinity of a bright star is shown.

This paper presents a series of studies of single conjugate adaptive optics systems that use numerical simulation to investigate aspects of system performance not addressed by traditional statistical metrics. These studies include investigations of temporal control loop dynamics and quantitative comparisons of system performance using different types of reconstructors.

We observe that a multi-conjugate adaptive optics (MCAO) system produces rapid fluctuations of irradiance of a few percent in the compensated focal plane when observing an extended target, such as the solar surface. Such fluctuations are absent in the uncompensated focal plane. The fluctuations are apparently correlated with the local curvature of deformable mirror in the plane conjugated to the high altitude turbulence layer. They can be explained by the field dependent change of effective focal length introduced by a high altitude turbulence layer, which is related to image distortion. Using a simple geometric model of the MCAO system, we are able to reproduce the observed irradiance effects. We propose to introduce a slightly undersized aperture stop at the location of the nominal exit pupil in order to remove the fluctuations in the compensated field.

The limit case of an infinite aperture adaptive optics (AO) system eliminates the modeling complications associated with aperture edge effects, and thereby enables the application of simplified methods for system performance evaluation in the spatial frequency domain. We review prior work in this field and describe a new approach that enables a wider range of error sources and AO options to be evaluated with a reduced number of approximations. These errors and AO options include: Fitting error and spatial aliasing for a Shack-Hartmann wavefront sensor (WFS) and one particular deformable mirror influence function; WFS noise; servo lag for a continuous temporal filter function; anisoplanatism in either a single evaluation direction or averaged over an extended field of view; piston removal within a finite aperture; minimum variance and modal wavefront reconstruction algorithms; and multi-conjugate AO. Laser guidestars, however, are excluded. A wide range of classical results for the independent effects of individual error sources can be immediately derived from this integrated model. Performance estimates for more complex problems involving the full range of first-order AO error sources are in good agreement with the results produced by more detailed Monte Carlo simulations.

We present recent developments of the CAOS "system", an IDL-based Problem Solving Environment (PSE) whose original aim was to define and simulate as realistically as possible the behavior of a generic adaptive optics (AO) system, from the atmospheric propagation of light, to the sensing of the wave-front aberratoins and the correction through a deformable mirror. The different developments made through the last 7 years result in a very versatile numerical tool complete of a global graphical interface (the CAOS Application Builder), and different specialized scientific packages: the original one designed for AO system simulations (the Software Package CAOS), an image reconstruction package with interferometric capabilities (the Software Package AIRY), and a more recent one being built and dedicated to multiconjugate AO (the Software Package MAOS). We present the status of the whole CAOS "system"/PSE, together with the most recent developments, including parallelization strategy considerations, examples of application, and plans for the next future.

In this paper, we summarize the analysis made on various Adaptive Optics (AO) modes (including Shack-Hartmann (SH) and Pyramid Wavefront Sensors (PWS)) for the OverWhelmingly Large telescope (OWL). We will show some early results of the performance to be expected with a first generation AO system, working in the infrared. Several telescope diameters were considered to see the variations as a function of telescope diameter. This is also compatible with the concept of "grow a telescope" where the telescope diameter of OWL grows from 60m to 100m as a function of time. In a first phase, to simplify the problem, the effects of the central obstruction were neglected. However, for the Shack-Hartmann (SH) simulations, additional simulations were carried out with a simulated OWL pupil, including segmentation errors. We show some early results for a ground-layer correction system, working with three natural guide stars (NGSs) and a single deformable mirror (DM). An MCAO system based on 2 DMs, 3 NGSs is also investigated. For the last two systems, our results are found to be in very good agreement with Cibola, an analytical AO modeling tool. We show that some outer scale of turbulence effects improve slightly the correction quality when going from a telescope diameter of 10m to 100m.

This paper contains a review of sparse matrix methods for open-loop wavefront estimation in astronomical adaptive optics systems with a large number of degrees of freedom. We address shortcomings of existing sparse methods for multiconjugate adaptive optics and propose some alternative approaches. We also review certain closed-loop control schemes, dubbed pseudo open-loop control (POLC), that make use of open-loop linear algebra, and we propose an extension of POLC that makes use of knowledge of atmospheric dynamics to carry out predictive estimation in closed loop.

We first recall in this paper the optimal closed loop control law for multiconjugate adaptive optics [MCAO]. It is based on a Kalman filter and a feedback control. The prior model on which is based the Kalman filter is developped in a state-space representation and the differences in the model between Star Oriented [SO] MCAO and Layer Oriented [LO] MCAO are presented. This approach allows to take into account the wavefront sensing noise, the turbulence profil model, the Kolmogorov statistics and a temporal model of the turbulence. Simulation results are given in SO MCAO and the Kalman based approach is compared to the more standard Optimized Modal Gain Integrator [OMGI].

The Adaptive Optics System of the Galileo Telescope (AdOpt@TNG) is the only adaptive optics system mounted on a telescope which uses a pyramid wavefront snesor and it has already shown on sky its potentiality. Recently AdOpt@TNG has undergone deep changes at the level of its higher orders control system. The CCD and the Real Time Computer (RTC) have been substituted as a whole. Instead of the VME based RTC, due to its frequent breakdowns, a dual pentium processor PC with Real-Time-Linux has been chosen. The WFS CCD, that feeds the images to the RTC, was changed to an off-the-shelf camera system from SciMeasure with an EEV39 80x80 pixels as detector. While the APD based Tip/Tilt loop has shown the quality on the sky at the TNG site and the ability of TNG to take advantage of this quality, up to the diffraction limit, the High-Order system has been fully re-developed and the performance of the closed loop is under evaluation to offer the system with the best performance to the astronomical community.

In this paper we present a solution to the MCAO reconstruction problem using multiple laser guide stars and show that it can be interpreted as a form of back-projection tomography. It is shown that a key intermediate step is to determine a minimum-variance estimate of the index variations over the atmospheric volume. We follow the idea of Tokovinin and Viard [JOSA-A, April 2001] in initially formulating the problem in the Fourier domain; we then extend the interpretation to the spatial domain. The former results were limited to the case of infinite aperture and plane wave beacons, and the statistically optimal wavefront solution was given for a single science direction. The new approach is more general and interpretable as tomographic back-projections, which gives rise to algorithms for the finite aperture, cone (laser) beams, and wide-science-field cases. A fortuitous consequence of this analysis is that a "fast" algorithm suitable for real-time implementation has become evident. The reconstruction requires only filtering and the inversion of small (dimension = number of guidestars) matrices. In simulations, we compare results with those of a spatial domain least-square matrix-inversion method.

This paper describes the current control system of the multi-conjugate adaptive optics (MCAO) test bench system that is being developed at the University of Victoria, BC, Canada. The design and analysis of a control system for an AO system employing a Micro-Electro-Mechanical-System (MEMS) based deformable mirror and a PI tilt mirror is presented. This paper focuses on modal control of one deformable mirror and a tilt mirror with a Shack-Hartmann wave front sensor. Diagrams of how all the components work together as a control system are given. Bandwidth measurements for a single delay integrator controller and for a matched delay integrator are presented. Analysis shows that matching the delays of the integrator to the delays of the optical feedback loop provides considerable improvement in bandwidth.

The Gemini North adaptive optics system Altair utilises five cooperative CPU's to perform all the associated real-time tasks. One, the reconstructor (RTC), manages all of the highest speed hard real-time duties. As well as the core, computationally intensive, wavefront reconstruction, this processor implements a number of algorithms providing control system support services. These include: the quad-cell centroid gain estimation, determination and subtraction of invisible modes on the deformable mirror, and the blending of tip, tilt and focus from the on instrument wavefront sensors (which exist on all facility Gemini instruments). These associated support tasks are critically important to ensure that the system always runs with an optimal bandwidth and produce stable images with no artefacts such as a waffle pattern or residual non-common path errors. We present the original algorithm that we have developed for the centroid gain estimate and discuss how it is efficiently and conveniently implemented on the hard real-time processor.