Abstract 178

Submitted by Diethard PETER

Authors

D. Peter, W. Gaessler

Affiliations

MPIA

Abstract

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.