<title>PUEO: the Canada-France-Hawaii Telescope adaptive optics bonnette I: system description</title>

Abstract

The Canada.Fraxxe-Hawajj Telescope (GHT) is developing an Adaptive Optics Instrument Adaptor for general use at its 3.6 m telescope. It consists of a 19 electrode, bimcrph deformable mirror (1:6:12) used with a 19 sub-aperture, curvature wavefront sensor. The wavefront sensor optical gain is controlled by the amplitude of a vibrating membrane mirror, which produces a defocus in t1 pupil plane. The tip-tilt correction is accomplished separately from the high order correction by tI f/19.6 reimaging mirror of the adaptor. The optical design minimizes tI number of reflections by using off-axis mirrors. The whole assembly is contained in an aluminium casting 1 10 cm in diameter and 28 cm thick. The adaptive optics control system will provide a 90 Hz servo bandwidth and modal control. The Pegasus user interface will manage overall control of tl system by the observer. This user-friendly interface has been developed at FHT, tl goal being to allow non-specialists in adaptive optics to operate the instrument in an optimal fashion, given the numerous parameters such as: brightness of t.l reference source, iscplanatic angle between reference and scieree sources, speed of atmospheric turbuleixz, wavelength of observation etc. Various imaging detectors or more complex instruments can be mounted on this adaptive optics adaptor. in t1 initial stage, we plan to use a CU) camera and NICMOS (HgCdTe) array for imagery in tl visible and non-tlrmal infrared. An integral field spectrograph will be provided as well The latter will offer a great deal of observing mode flexibility; imagery and/or spectroscopy with various combinations ci spatial and spectral resolution. . PROJECF STATUSThe Canada-Fraixe-Hawajj Telescope has undertaken the development and fabrication of an Adaptive Optics Bxmnette (AOB) for its 3.6 m telescope on top of Mauna Kea (Hawaii). The "bomtte" will be installed at tl f/8 Cassegrain focus of tl telescope. Physically, the bonnette is an adaptor ring 1.1 m in diameter and 28 cm thick on which varions instruments (imagers, spectrographs) can be mounted. It will be a fiity instrument, offering varions backup modes to insure reliability frcxn an operational point of view. The user interface aims at being reasonably straightforward, offering a simple and restricted choice of parameters to tJ user.The design and fabrication tasks are shared between many institutes; the CFHT is managing tl project, issuing the specifications, supervising development and fabrication, performance modelling and realizing the general user interfe. The Dominion Astrophysical Observatory (DAO, Canada) has designed and is fabricating the opto-mechanical bench, and the wavefront sensor assembly (WFS). The optical design is from H. Richardson (U. of Victoria Canada) and DAO is subcontracting the fabrication of the optics to various companies in the US and Canada. The company Laserdot (Marcoussis, France) is providing the deformable mirror and the real-time control system. Laserdot is also providing some high level software tools. The fabrication o...

New algorithms for adaptive optics point-spread function reconstruction

“…Véran et al (1997) have been the first to develop such a PSF reconstruction algorithm. Implemented on the CFHT curvature sensing AO system PUEO (Arsenault et al 1994), it has been routinely delivering reconstructed on-axis PSFs for more than 8 years now. A first attempt to transpose this algorithm to the Shack-Hartmann (SH) wavefront sensor has been undertaken by Harder & Chelli (2000).…”

Monomorph deformable mirrors: from ground-based facilities to space telescopes

“…The first bimorph from CILAS operating on the sky was developed for the AO system known as "PUEO" [2]. It was installed on the 3.6-meter Canada-France-Hawaii Telescope (CFHT), located near the summit of Mauna Kea on Hawaii's Big Island at an altitude of 4,204 meters.…”

“…The first major success of this collaboration was obtained in 1989 with the first light of COME-ON (Cge, Observatoire de Meudon, Eso, ONera). The results obtained with this Adaptive Optics (AO) prototype constituted the first demonstration in astronomy of atmospheric turbulence real-time correction [2]. Such as many other AO systems from ESO (European Southern Observatory), this first system was equipped with a piezoelectric deformable mirror designed and manufactured by CILAS (formerly CGE).…”

“…These mirrors were dedicated to fast correction of atmospheric turbulences for ground-based telescopes (field of adaptive optics) but also for quasi-static correction of very low thermal drifts, for instance in high-power laser systems to optimize the focusing of the optical beams (field of active optics). Since 1996 and the first light of PUEO [2], CILAS is proposing a time-tested technology with performances meeting the requirements of these two fields of correction (active and adaptive optics): the bimorph technology and its most recent and most powerful generation, the monomorph. …”

PSF reconstruction for NAOS-CONICA

“…Véran et al (1997) have demonstrated that AO allows one to derive the PSF from wavefront-related data delivered by the AO RTC. They have been the first to develop such a PSF reconstruction algorithm and to implement it on an AO system: PUEO, the CFHT curvature AO system (Arsenault et al, 1994). Since then, the algorithm is routinely used to provide astronomers with the (on-axis) PSF associated to their observations.…”