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PSF-reconstruction for the GLAO system ARGOS

Abstract 178

Submitted by Diethard PETER


D. Peter, W. Gaessler




Present and future adaptive optics systems aim for the correction of the atmospheric turbulence over a large field of view combined with large sky coverage. Thus they use multiple laser beacons on sky. For many applications a correction as uniform as possible over the whole field is desired. Still there will always be variations in the shape of the PSF with field angle. To overcome this drawback, a good knowledge of the PSF over the field is desired. In the past, several algorithms of PSF retrieval have been proposed and tested. This includes on-axis PSF retrieval from wavefront sensor data as well as a correction over the field using a reference PSF. The schemes have been set up for both an AO system using a single natural guide star as well as a system using a laser beacon. For these algorithms to work, a detailed knowledge of the atmospheric structure, i.e. Cn2 profile, is crucial. The ARGOS system, a GLAO system proposed for the LBT, will use three Rayleigh laser beacons per eye of the telescope. The beacons are positioned at an height of 12 km and on a circle with radius 2 arcmin. We show how the usage of multiple lasers can be used to retrieve the atmospheric profile and how the conventional PSF-retrieval algorithms must be changed to make up for the difference between the multiple beacon GLAO used in ARGOS and the typical single source on-axis schemes.