The construction of a diffraction limitable telescope as large as the ESO’s ELT is enabled by its embedded deformable quaternary mirror. Besides its essential function in the telescope control, M4 also contributes to compensating the free atmosphere aberrations for all post-focal AO applications. The paper presents how the telescope manages M4 to maintain its optical performance while offering to the instruments a clean wavefront interface, supporting the desired AO functionalities. The paper reviews the telescope strategy to derive its wavefront dynamic properties directly from the analysis of the control data collected in science mode, with the goal to minimize the observatory time spent on dedicated wavefront calibration tasks.
The Adaptive Optics Facility (AOF) is one of the most important ESO projects developed for the VLT programme in the last years. The AOF, currently still under commissioning, brings built-in AO capabilities (GLAO and LTAO) to one of the VLT 8m Telescopes (Yepun) that is now equipped with a deformable secondary mirror (DSM), four lasers guide stars (4LGSF) and two AO modules: GRAAL for the HAWK-I infrared imager and GALACSI for the MUSE 3D spectrograph. This paper describes the main aspects of the software responsible for the control and monitor of the two AO modules, as well as for the coordination of subsystems like the instruments and the telescope. Furthermore details of the strategy followed to minimize the impact on configuration control associated to several commissioning periods interleaved with normal operations will be given. The control software package consist of a set of modules based on the VLT Instrumentation Framework and on the VLT platform for AO Real-Time Applications (SPARTA). We will present the software and control design choices that have contributed to the successful commissioning and science verification of GALACSI Wide Field Mode (WFM) and the first verifications of GRAAL tip/tilt free mode covering the control of challenging devices such as the GRAAL Corotator or the GALACSI visible Field Selector together with the innovative and flexible implementation of the AO acquisition sequence and its seamless integration to the instrument observations, the handling of secondary loops and the development of health-check and commissioning scripts (templates) that automated the verification of the different observing modes.
For two years starting in February 2014, the AO modules GRAAL for HAWK-I and GALACSI for MUSE of the Adaptive Optics Facility project have undergone System Testing at ESO's Headquarters. They offer four different modes: NGS SCAO, LGS GLAO in the IR, LGS GLAO and LTAO in the visible. A detailed characterization of those modes was made possible by the existence of ASSIST, a test bench emulating an adaptive VLT including the Deformable Secondary Mirror, a star simulator and turbulence generator and a VLT focal plane re-imager. This phase aimed at validating all the possible components and loops of the AO modules before installation at the actual VLT that comprises the added complexity of real LGSs, a harsher non-reproducible environment and the adaptive telescope control. <p> </p>In this paper we present some of the major results obtained and challenges encountered during the phase of System Tests, like the preparation of the Acquisition sequence, the testing of the Jitter loop, the performance optimization in GLAO and the offload of low-order modes from the DSM to the telescope (restricted to the M2 hexapod). The System Tests concluded with the successful acceptance, shipping, installation and first commissioning of GRAAL in 2015 as well as the acceptance and shipping of GALACSI, ready for installation and commissioning early 2017.
GALACSI is the Adaptive Optics (AO) module that will serve the MUSE Integral Field Spectrograph. In Wide Field Mode it will enhance the collected energy in a 0.2”×0.2” pixel by a factor 2 at 750 nm over a Field of View (FoV) of 1’×1’ using the Ground Layer AO (GLAO) technique. In Narrow Field Mode, it will provide a Strehl Ratio of 5% (goal 10%) at 650 nm, but in a smaller FoV (7.5”×7.5” FoV), using Laser Tomography AO (LTAO). Before being ready for shipping to Paranal, the system has gone through an extensive testing phase in Europe, first in standalone mode and then in closed loop with the DSM in Europe. After outlining the technical features of the system, we describe here the first part of that testing phase and the integration with the AOF ASSIST (Adaptive Secondary Setup and Instrument Stimulator) testbench, including a specific adapter for the IRLOS truth sensor. The procedures for the standalone verification of the main system performances are outlined, and the results of the internal functional tests of GALACSI after full integration and alignment on ASSIST are presented.
Over the last decade, adaptive optics has become essential in different fields of research including medicine and industrial applications. With this new need, the market of deformable mirrors has expanded a lot allowing new technologies and actuation principles to be developed. Several E-ELT instruments have identified the need for post focal deformable mirrors but with the increasing size of the telescopes the requirements on the deformable mirrors become more demanding. A simple scaling up of existing technologies from few hundred actuators to thousands of actuators will not be sufficient to satisfy the future needs of ESO. To bridge the gap between available deformable mirrors and the future needs for the E-ELT, ESO started a development program for deformable mirror technologies. The requirements and the path to get the deformable mirrors for post focal adaptive optics systems for the E-ELT is presented.
The Multi-Conjugate Adaptive Optics module for the European Extremely Large Telescope has been designed to achieve uniform compensation of the atmospheric turbulence effects on a wide field of view in the near infrared. The design realized in the Phase A of the project is undergoing major revision in order to define a robust baseline in view of the next phases of the project. An overview of the on-going activities is presented.
This paper describes ESO’s surface measurement device for large image detectors in astronomy. The machine was equipped with a sub-micrometer laser displacement sensor and is fully automated with LabView. On the example of newly developed curved CCDs, which are envisaged for future astronomical instruments, it was demonstrated that this machine can exactly determine the topographic surfaces of detectors. This works even at cryogenic temperatures through a dewar window. Included is the calculation of curvature radii from these cold curved CCDs after spherical fitting with MATLAB. In addition (and interesting for calibration of instruments) the micro-movements of the detector inside the cryostat are mapped.
The Adaptive Optics Facility project is completing the integration of its systems at ESO Headquarters in Garching. The main test bench ASSIST and the 2<sup>nd</sup> Generation M2-Unit (hosting the Deformable Secondary Mirror) have been granted acceptance late 2012. The DSM has undergone a series of tests on ASSIST in 2013 which have validated its optical performance and launched the System Test Phase of the AOF. This has been followed by the performance evaluation of the GRAAL natural guide star mode on-axis and will continue in 2014 with its Ground Layer AO mode. The GALACSI module (for MUSE) Wide-Field-Mode (GLAO) and the more challenging Narrow-Field-Mode (LTAO) will then be tested. The AOF has also taken delivery of the second scientific thin shell mirror and the first 22 Watt Sodium laser Unit. We will report on the system tests status, the performances evaluated on the ASSIST bench and advancement of the 4Laser Guide Star Facility. We will also present the near future plans for commissioning on the telescope and some considerations on tools to ensure an efficient operation of the Facility in Paranal.
GALACSI is the Adaptive Optics (AO) modules of the ESO Adaptive Optics Facility (AOF) that will correct the wavefront delivered to the MUSE Integral Field Spectrograph. It will sense with four 40×40 subapertures Shack-Hartmann wavefront sensors the AOF 4 Laser Guide Stars (LGS), acting on the 1170 voice-coils actuators of the Deformable Secondary Mirror (DSM). GALACSI has two operating modes: in Wide Field Mode (WFM), with the four LGS at 64” off axis, the collected energy in a 0.2”×0.2” pixel will be enhanced by a factor 2 at 750 nm over a Field of View (FoV) of 1’×1’ using the Ground Layer AO (GLAO) technique. The other mode, the Narrow Field Mode (NFM), provides an enhanced wavefront correction (Strehl Ratio (SR) of 5% (goal 10%) at 650 nm) but in a smaller FoV (7.5”×7.5”), using Laser Tomography AO (LTAO), with the 4 LGS located closer, at 10” off axis. Before being shipped to Paranal, GALACSI will be first integrated and fully tested in stand-alone, and then moved to a dedicated AOF facility to be tested with the DSM in Europe. At present the module is fully assembled, its main functionalities have been implemented and verified, and AO system tests with the DSM are starting. We present here the main system features and the results of the internal functional tests of GALACSI.
The ESO Adaptive Optics Facility (AOF) consists in an evolution of one of the ESO VLT unit telescopes to a laser
driven adaptive telescope with a deformable mirror in its optical train.
The project has completed the procurement phase and several large structures have been delivered to Garching
(Germany) and are being integrated (the AO modules GRAAL and GALACSI and the ASSIST test bench). The 4LGSF
Laser (TOPTICA) has undergone final design review and a pre-production unit has been built and successfully tested.
The Deformable Secondary Mirror is fully integrated and system tests have started with the first science grade thin shell
mirror delivered by SAGEM. The integrated modules will be tested in stand-alone mode in 2012 and upon delivery of
the DSM in late 2012, the system test phase will start. A commissioning strategy has been developed and will be updated
before delivery to Paranal. A substantial effort has been spent in 2011-2012 to prepare the unit telescope to receive the
AOF by preparing the mechanical interfaces and upgrading the cooling and electrical network. This preparation will also
simplify the final installation of the facility on the telescope.
A lot of attention is given to the system calibration, how to record and correct any misalignment and control the whole
facility. A plan is being developed to efficiently operate the AOF after commissioning. This includes monitoring a
relevant set of atmospheric parameters for scheduling and a Laser Traffic control system to assist the operator during the
night and help/support the observing block preparation.
GALACSI is one of the Adaptive Optics (AO) systems part of the ESO Adaptive Optics Facility (AOF). It will use the
VLT 4-Laser Guide Stars system, high speed and low noise WaveFront Sensor cameras (<1e-, 1000Hz) the
Deformable Secondary Mirror (DSM) and the SPARTA Real Time Computer to sharpen images and enhance faint
object detectability of the MUSE Instrument. MUSE is an Integral Field Spectrograph working at wavelengths from
465nm to 930nm. GALACSI implements 2 different AO modes; in Wide Field Mode (WFM) it will perform Ground
Layer AO correction and enhance the collected energy in a 0.2" by 0.2" pixel by a factor 2 at 750nm over a Field of
View (FoV) of 1' by 1'. The 4 LGSs and one tip tilt reference star (R-mag <17.5) are located outside the MUSE FoV.
Key requirements are to provide this performance and a very good image stability for a 1hour long integration time. In
Narrow Field Mode (NFM) Laser Tomography AO will be used to reconstruct and correct the turbulence for the center
field using the 4 LGSs at 15" off axis and the Near Infra Red (NIR) light of one reference star on axis for tip tilt and
focus sensing. In NFM GALACSI will provide a moderate Strehl Ratio of 5% (goal 10%) at 650nm. The NFM hosts
several challenges and many subsystems will be pushed to their limits. The opto mechanical design and error budgets
of GALACSI is described here.
The ESO Adaptive Optics Facility (AOF) consists in an evolution of one of the ESO VLT unit telescopes to a laser
driven adaptive telescope with a deformable mirror in its optical train, in this case the secondary 1.1m mirror, and four
Laser Guide Stars (LGSs). This evolution implements many challenging technologies like the Deformable Secondary
Mirror (DSM) including a thin shell mirror (1.1 m diameter and 2mm thin), the high power Na lasers (20W), the low
Read-Out Noise (RON) WaveFront Sensor (WFS) camera (< 1e-) and SPARTA the new generation of Real Time
Computers (RTC) for adaptive control. It also faces many problematic similar to any Extremely Large Telescope (ELT)
and as such, will validate many technologies and solutions needed for the European ELT (E-ELT) 42m telescope. The
AOF will offer a very large (7 arcmin) Field Of View (FOV) GLAO correction in J, H and K bands (GRAAL+Hawk-I),
a visible integral field spectrograph with a 1 arcmin GLAO corrected FOV (GALACSI-MUSE WFM) and finally a
LTAO 7.5" FOV (GALACSI-MUSE NFM). Most systems of the AOF have completed final design and are in
manufacturing phase. Specific activities are linked to the modification of the 8m telescope in order to accommodate the
new DSM and the 4 LGS Units assembled on its Center-Piece. A one year test period in Europe is planned to test and
validate all modes and their performance followed by a commissioning phase in Paranal scheduled for 2014.
ASSIST: The Adaptive Secondary Setup and Instrument STimulator is the test setup for the verification and calibration
of three elements of the VLT Adaptive Optics Facility.; the Deformable Secondary Mirror (DSM) the AO system for
MUSE and HAWK-I (GALACSI and GRAAL). In the DSM testing mode the DSM will be tested using both
interferometry and fast wave front sensing. In full AO mode, ASSIST will allow testing of the AO systems under
realistic atmospheric conditions and optically equivalent to the conditions on the telescope. ASSIST is nearing its final
design review and in this paper we present the current optical and mechanical design of ASSIST. In this paper we
highlight some of the specific aspects of ASSIST that we are developing for ASSIST.
ESO has initiated in June 2004 a concept of Adaptive Optics Facility. One unit 8m telescope of the VLT is upgraded
with a 1.1 m convex Deformable Secondary Mirror and an optimized instrument park. The AO modules GALACSI and
GRAAL will provide GLAO and LTAO corrections forHawk-I and MUSE. A natural guide star mode is provided for
commissioning and maintenance at the telescope. The facility is completed by a Laser Guide Star Facility launching 4
LGS from the telescope centerpiece used for the GLAO and LTAO wavefront sensing. A sophisticated test bench called
ASSIST is being designed to allow an extensive testing and characterization phase of the DSM and its AO modules in
Europe. Most sub-projects have entered the final design phase and the DSM has entered Manufacturing phase. First light
is planned in the course of 2012 and the commissioning phases should be completed by 2013.
ASSIST - The Adaptive Secondary Setup and Instrument STimulator is a test setup to verify the operation of three
elements of the VLT Adaptive Optics Facility, namely the Deformable Secondary Mirror (DSM) and the two AO
systems using this DSM, the AO system for the visible light integral field spectrograph MUSE (GALACSI) and the AO
system for the IR wide field imager HAWK-I (GRAAL). To support the testing of these elements, ASSIST will provide
both an interferometry setup for testing the DSM as well as a full atmospheric turbulence simulator and star simulator to
mimic the conditions at the telescope. To test the instruments using the DSM, the output beam is matched the output
beam of the VLT telescope, including the correct exit-pupil and high-quality imaging and a similar hardware interface is
provided. Since one of the modes to be verified is nearly diffraction limited, also the thermal and vibrational stability
are very important, with strong constraints on both the mechanical as well as the optical design.
A comprehensive suite of Adaptive Optics systems and AO-assisted instruments is currently under development for the VLT and will be built around a hyperbolic convex adaptive Deformable Secondary Mirror (DSM). In telescopes with such a secondary mirror, test and calibration of both the DSM and the science instruments using it are notoriously expensive and time-consuming. The Adaptive Secondary Setup and Instrument Stimulator (ASSIST) is being developed to allow test and integration of three key elements of the future VLT Adaptive Telescope Facility: the DSM and 2 instrument-specific adaptive optics systems (GALACSI for MUSE and GRAAL for HAWK-I). The core of ASSIST is a standalone interferometric test setup for the DSM allowing its test at its center of curvature (significantly reducing the size of the classical hyperbole focii test configuration). This setup is completed by a star simulator for both natural and laser guide stars, a turbulence generator (for realistic AO performance measurements), a corrector system generating a VLT-like exit pupil and a Nasmyth rotator simulator interfacing with the two AO systems.
In this paper we present the optical architecture of ASSIST, detailing the current design of the different parts of the system, and discuss its projected performance and compliance with the test and calibration requirements.
Several designs of future Adaptive Optics (AO) systems propose to use a large Deformable Mirror (DM), regarding the size as well as the number of actuators. Most of the time, there is no focal plane upstream the DM. Therefore, the classical way of calibrating the interaction matrix on an artificial source cannot be applied. Furthermore, the requirements in terms of calibration error budget are tight and the high order modes of such DMs are stiff and hence they achieve only a small stroke. This is why novel ways to determine the system Interaction Matrix (IM) have to be investigated. Several paths have been studied. One solution would be to simulate a synthetic IM. However, calibration on sky is also an option. Different techniques were simulated, tested and optimized on real AO systems. The results are presented in this paper.
The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph under preliminary design study. MUSE has a field of 1x1 arcmin<sup>2</sup> sampled at 0.2x0.2 arcsec<sup>2</sup> and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The simultaneous spectral range is 0.465-0.93 μm, at a resolution of R~3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5x7.5 arcsec<sup>2</sup> field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to obtain diffraction limited data-cubes in the 0.6-0.93 μm wavelength range. Although the MUSE design has been optimized for the study of galaxy formation and evolution, it has a wide range of possible applications; e.g. monitoring of outer planets atmosphere, environment of young stellar objects, super massive black holes and active nuclei in nearby galaxies or massive spectroscopic surveys of stellar fields in the Milky Way and nearby galaxies.
In telescopes with a Deformable Secondary Mirror, the testing and calibration of both the DSM itself as well as the instruments using this DSM are expensive and time consuming processes. Especially in telescopes without an intermediate focus before the DSM, a number of calibrations can only be performed on a real star during night time. A full suite of Adaptive Optics systems and AO-assisted instruments is currently under development for the VLT, also know as the VLT Adaptive Telescope. ASSIST was developed to assist in the integration and testing of three elements of the VLT Adaptive Telescope Facility; the DSM; the MUSE AO system 'GALACSI' and the HAWK-I AO system 'GRAAL.' The core of ASSIST is a support infrastructure to integrate the DSM in a compact and stable test setup. A Nasmyth rotator simulator will be provided for attaching the two AO systems, while ASSIST will be fed by a star simulator and turbulence generator for realistic performance measurements of both the DSM as well as the AO system under test. An on-axis high-speed interferometer will be used for additional testing of the functional operation of the DSM. In this paper we present the requirements and design of ASSIST and the projected performance of the test bench for both the testing and calibration of the DSM as well as for the two AO systems under test.
The Adaptive Optics Facility is a project to convert one VLT-UT into a specialized Adaptive Telescope. The present
secondary mirror (M2) will be replaced by a new M2-Unit hosting a 1170 actuators deformable mirror. The 3 focal
stations will be equipped with instruments adapted to the new capability of this UT. Two instruments are in
development for the 2 Nasmyth foci: Hawk-I with its AO module GRAAL allowing a Ground Layer Adaptive Optics
correction and MUSE with GALACSI for GLAO correction and Laser Tomography Adaptive Optics correction. A
future instrument still needs to be defined for the Cassegrain focus. Several guide stars are required for the type of
adaptive corrections needed and a four Laser Guide Star facility (4LGSF) is being developed in the scope of the AO
Facility. Convex mirrors like the VLT M2 represent a major challenge for testing and a substantial effort is dedicated to
this. ASSIST, is a test bench that will allow testing of the Deformable Secondary Mirror and both instruments with
simulated turbulence. This article describes the Adaptive Optics facility systems composing associated with it.
ESO has initiated in June 2004 a feasibility study to investigate the possibility to retro-fit one of the VLT 8 m telescope with a deformable secondary mirror (DSM). The scope of this effort has been broadened to a concept of Adaptive Optics Facility (adaptive telescope with adapted instrument park). The feasibility study, conducted by MicroGate, ADS Intl and the INAF-Osservatorio Astrofisico di Arcetri, has been successful (no show stopper identified) and has provided an elegant design of an alternate M2-Unit for the VLT. It features a 1170 actuators DSM based on the voice coil force actuators coupled with capacitive sensors. An 80 kHz internal control loop allows implementing of electronic damping. The simulations performed have shown a fitting error of 62.5 nm rms (<i>r</i><sub>o</sub> = 12.1 cm @ 30 deg. zenith) with a 2mm thin shell and 1.5 kW of heat dissipation. The design shall provide a full stroke of ~50 μm and a rise time of < 1 msec. The DSM will be focused and "centered" by a Hexapod and a bi-positions electro-mechanism will allow switching from Nasmyth to Cassegrain focus configuration. Several features are planned to ease maintenance and diagnostic.
The adaptive optics MACAO has been implemented in 6 focii of the VLT observatory, in three different flavors. We present in this paper the results obtained during the commissioning of the last of these units, MACAO-CRIRES. CRIRES is a high-resolution spectrograph, which efficiency will be improved by a factor two at least for point-sources observations with a NGS brighter than R=15. During the commissioning, Strehl exceeding 60% have been observed with fair seeing conditions, and a general description of the performance of this curvature adaptive optics system is done.
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.
SINFONI is an Adaptive Optics assisted near infrared Integral Field Spectrometer, currently in the process of installation and commissioning at the Cassegrain focus of VLT Unit Telescope 4 (YEPUN) in Paranal (Chile). The focal plane instrument (SPIFFI) provides simultaneous spectra of 2048 contiguous spatial pixels covering a two dimensional field of view with almost 100% spatial fill factor and with a spectral resolution of ~3500 in the J, H and K bands. It is fed by the Adaptive Optics Module, a 60 elements bimorph deformable mirror technology / curvature sensing system, derived from MACAO and upgraded to Laser Guide Star operations. This papers reports on the Adaptive Optics Module first light (May 31st 2004). Performances in Natural Guide Star mode were validated during the first commissioning and tests were carried out in preparation to the Laser Guide Star mode. Combined operations of the AO-Module with SPIFFI will start during the second commissioning in July. SINFONI is scheduled to be offered to the community in Natural Guide Star mode in April 2005. The commissioning of the instrument in Laser Guide Star mode will take place in the course of 2005 after successful completion of the Laser Guide Star Facility commissioning.
MACAO-VLTI is a set of four adaptive optics systems dedicated to interferometry with the ESO 8 meter telescopes in Paranal, Chile. One of the most important requirements for the MACAO-VLTI is to keep the piston variations of the bimorph deformable mirror below 25 nm RMS in a time window of 48 msec. For this purpose, a piston removal algorithm has been developed, that uses a pre-calibrated set of voltages to compensate the natural piston of each influence function. This pre-calibration constitutes a critical laboratory measurement of the influence functions. Using Hadamard matrices, a (64 x 64) Shack-Hartman sensor and a capacitive sensor located at the center of the mirror (back-side), an accuracy better than 1% has been reached to characterize them. Various configurations were investigated to minimize the dynamical residual piston: the control matrix, the loop speed and the loop gain. Particular attention was paid to the influence functions non-linearities. An original indirect method was developed to measure the residual piston in real-time. We present here the methods and results obtained so far.
SINFONI is an adaptive optics assisted near-infrared integral field spectrometer for the ESO VLT. The Adaptive OPtics Module (built by the ESO Adaptive Optics Group) is a 60-elements curvature-sensor based system, designed for operations with natural or sodium laser guide stars. The near-infrared integral field spectrometer SPIFFI (built by the Infrared Group of MPE) provides simultaneous spectroscopy of 32 x 32 spatial pixels, and a spectral resolving power of up to 3300. The adaptive optics module is in the phase of integration; the spectrometer is presented tested in the laboratory. We provide an overview of the project, with particular emphasis on the problems encountered in designing and building an adaptive optics assisted spectrometer.
Over the past two years ESO has reinforced its efforts in the field of Adaptive Optics. The AO team has currently the challenging objectives to provide 8 Adaptive Optics systems for the VLT in the coming years and has now a world-leading role in that field. This paper will review all AO projects and plans. We will present an overview of the Nasmyth Adaptive Optics System (NAOS) with its infrared imager CONICA installed successfully at the VLT last year. Sodium Laser Guide Star plans will be introduced. The status of the 4 curvature AO systems (MACAO) developed for the VLT interferometer will be discussed. The status of the SINFONI AO module developed to feed the infrared integral field spectrograph (SPIFFI) will be presented. A short description of the Multi-conjugate Adaptive optics Demonstrator MAD and its instrumentation will be introduced. Finally, we will present the plans for the VLT second-generation AO systems and the researches performed in the frame of OWL.
MACAO stands for Multi Application Curvature Adaptive Optics. A similar concept is applied to fulfill the need for wavefront correction for several VLT instruments. MACAO-VLTI is one of these built in 4 copies in order to equip the Coude focii of the ESO VLT's. The optical beams will then be corrected before interferometric recombination in the VLTI (Very Large Telescope Interferometer) laboratory. MACAO-VLTI uses a 60 elements bimorph mirror and curvature wavefront sensor. A custom made board processes the signals provided by the wavefront detectors, 60 Avalanche Photo-diodes, and transfer them to a commercial Power PC CPU board for Real Time Calculation. Mirrors Commands are sent to a High Voltage amplifier unit through an optical fiber link. The tip-tilt correction is done by a dedicated Tip-tilt mount holding the deformable mirror. The whole wavefront is located at the Coude focus. Software is developed in house and is ESO compatible. Expected performance is a Strehl ratio sligthly under 60% at 2.2 micron for bright reference sources (star V<10) and a limiting magnitude of 17.5 (Strehl ~0.1). The four systems will be installed in Paranal successively, the first one being planned for June 2003 and the last one for June 2004.
The European Southern Observatory (ESO) and the Max Planck Institut fur extraterrestrische Physik (MPE) are jointly developing SINFONI, an Adaptive Optics (AO) assisted Near Infrared Integral Field Spectrometer, which will be installed in the first quarter of 2004 at the Cassegrain focus of YEPUN (VLT UT4). The Adaptive Optics Module, a clone of MACAO, designed and built by ESO, is based on a 60 elements curvature system. It feeds the 3D spectrograph, SPIFFI, designed and built by MPE, with higher than 50% K band Strehl for bright (V<12) on-axis Natural Guide Stars (NGS) and less than 35 mas/hour image motion. The AO-Module will be the first curvature AO system operated in Laser Guide Star (LGS) mode, using a STRAP system for the tip/tilt sensing. The Strehl performance in the LGS mode is expected to be better than 30% in K band.
The European Southern Observatory is developing a medium order curvature adaptive optics system designed to be operable with minimal modification at any focus of the Very Large telescope (VLT). The first application of this AO system (MACAO) is to equip all four VLT Unit Telescope (UT) Coude foci with 60 element AO systems capable of delivering to the VLT Interferometer (VLTI) > 50% K band Strehl. The AO system being used by an interferometer is constrained to introduce minimal piston and operating as a sub-system of a large and complex instrument to have a robust architecture and simple operation. Installation of the first AO system is scheduled to begin first Quarter 2002 with completion of all four UTs by early 2004. Other applications of the MACAO system will be for use by the CRIRES and SPIFFI spectrographs.