Tests of the PSF reconstruction algorithm for NACO/VLT

Abstract

We have developed an PSF reconstruction algorithm for the NAOS adaptive optics system that is coupled with CONICA at ESO/VLT. We have modified the algorithm of V'eran et al. (1997), originally written for PUEO at CFHT, to make use of the specific real-time wavefront-related data that observers with NACO receive together with their scientific images. In addition, we use the V ii algorithm introduced by Clénet et al. (2006) and Gendron et al. (2006) instead of the U ij algorithm originally used by V'eran et al. (1997). Until now, tests on NAOS has been undertaken during technical time thanks to the NACO team at Paranal. A first test has been successfully performed to calibrate the orientation of reconstructed PSFs with respect to NACO images. We have also obtained two sets of PSF reconstruction test data with NACO in November 2006 and September 2007 to reconstruct PSFs. Discrepancies exist between the observed and reconstructed PSFs: their Strehl ratios are ∼31% and ∼39%respectively in Nov. 2006, ∼31% and ∼19% respectively in Sept. 2007. These differences may be at least partly explained by reconstructions that either did not account for the aliasing contribution or poorly estimated the noise contribution with the available noise information at that time. We have additionally just started to test our algorithm using the AO bench S'esame, at LESIA. Results are promising but need to be extended to a larger set of atmospheric conditions or AO correction qualities. Keywords: Adaptive optics; NAOS-CONICA; PSF reconstruction; simulations; S'esame AO bench.