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Segment phasing experiments on the High Order Test bench.

Abstract 119

Submitted by Emmanuel ALLER


E. Aller, M. Kasper, P. Martinez.


European Southern Observatory


The segmented primary mirror of the E-ELT imposes particular requirements on an Extreme Adaptive Optics (XAO) system. At present, there are already several AO systems working on segmented telescopes but the achieved performances are too low to draw conclusions for XAO systems aiming at some 90% Strehl ratio in the NIR. On other hand, several analytical studies and simulations were done, but laboratory studies are required to confirm the corrections expected.

The goal of the present study is to determinate the capability of XAO systems to deal with the segmentation piston errors testing two types of wave front sensors: Shack-Hartmann and Pyramid. Among the large variety of tests done, the effects on the AO performance and the ability of the AO system to correct the segmentation piston errors were studied.

The experiments were carry out on the “High Order Test Bench” at ESO (Munich) under most realistic conditions with phase screens simulating atmospheric turbulence and segmentation piston errors. Segment geometry was chosen such that about 6 actuators of the XAO DM cover one segment representing the design of EPICS at the EELT.