First results on a Cn2 profiler for GeMS

Abstract

GeMS (the Gemini MCAO System) is a facility instrument for the Gemini-South telescope. The system includes five laser guide stars, three natural guide stars, three deformable mirrors optically conjugated at 0, 4.5 and 9km and one tip-tilt mirror. Some of its unique features include an embedded Cn2 SLODAR profiler which is described in this paper. The Cn2 profile is reconstructed from the slopes seen by the 5 high order WFS, each one pointing in a laser guide star direction. Residuals from the 16×16 subapertures WFSs and DM commands are used to obtain pseudo-open loop data for SLODAR, allowing us to reconstruct up to 16 layers. The paper describes the results obtained from different validation steps followed during the development of the technique, namely: numerical simulations, artificially generated turbulence via DMs excitation and the use of on-sky data obtained from different commissioning nights. We also present results from a wind profiler that runs in parallel to SLODAR and finally compare the results to those from a nearby MASS/DIMM instrument. Show more