Anisoplanatism effects in Shack-Hartmann wave front sensing with laser guide stars on the ELTs

Abstract

Laser Guide Stars aim at increasing the sky coverage, highly restricted when using Adaptive Optics with Natural Guide Stars. With such an artificial object, spot elongation may be a limitation for the measurement quality when using a Wave Front Sensor. In this document, we evaluate and discuss the effects of this limitation on wave front measurements, for a 40 m class telescope. We also explore the possibilities of taking these effects into account in the wave front reconstruction.