Olivier Lardi`ere (University of Victoria), Rodolphe Conan (University of Victoria), Colin Bradley (University of Victoria), Kate Jackson (University of Victoria), Glen Herriot (NRCHerzberg Institute of Astrophysics)
Keywords: Adaptive Optics
Abstract:
Sodium laser guide stars (LGSs) allow, in theory, full sky coverage, but have their own limitations. Variations of sodium layer altitude, thickness and atom density profile induce changing errors on wavefront measurements (LGS aberrations), especially with ELTs for which the LGS spot elongation is larger. In the framework of the Thirty–Meter–Telescope project (TMT), the AO–Lab of the University of Victoria (UVic) built a LGS–simulator test bed in order to assess the performance of new centroiding algorithms for LGS Shack-Hartmann wavefront sensors (SH–WFS). The principle of the LGS–bench is briefly reviewed. The closed–loop performances of the matched filter (MF) algorithm on laboratory 29×29 elongated spot images are presented and compared with the centre of gravity (CoG). The ability of the MF to track the LGS aberrations is successfully demonstrated. The UVic LGS–bench is not limited to SH–WFS and can serve as a LGS–simulator test bed to any other LGS–AO projects for which sodium layer fluctuations are an issue.
Date of Conference: September 16-19, 2008
Track: Adaptive Optics