New results on a Cn2 profiler for GeMS

Abstract

The atmospheric optical turbulence profile, the strength of the turbulence as a function of altitude above the ground, can be used to determine the seeing statistics of a particular site. This information is useful for optimizing the tomographic process in Adaptive Optics systems and for characterizing the performance. In this paper, we describe a method to estimate the atmospheric turbulence profile based on the telemetry data coming out of GeMS, a Multi Conjugated Adaptive Optics (MCAO) instrument installed on the Gemini South telescope. The method is based on the SLODAR technique (SLOpe Detection and Ranging), where the wavefront slopes from two stars angularly separated on the sky are measured, and their cross-correlation is used to retrieve the atmospheric optical profile. We have modified the classical SLODAR method and adapted it for the closed loop, multiple laser guide stars case. In this paper we present our method, validation of it in simulation, and its application for on-sky data.