Towards a reliability assessment of the Cn2 and wind speed vertical profiles retrieved from GeMS

摘要

The advent of a new generation of Adaptive Optics systems called Wide FieldAO (WFAO) mark the beginning of a new era. By using multiple Guide Stars (GSs),either Laser Guide Stars (LGSs) or Natural Guide Stars (NGSs), WFAOsignificantly increases the field of view of the AO-corrected images, and thefraction of the sky that can benefit from such correction. Different typologiesof WFAO have been studied over the past years. They all require multiple GSs toperform a tomographic analysis of the atmospheric turbulence. One of thefundamental aspects of the new WFAO systems is the knowledge of thespatio-temporal distribution of the turbulence above the telescope. One way toget to this information is to use the telemetry data provided by the WFAOsystem itself. Indeed, it has been demonstrated that WFAO systems allows one toderive the Cn2 and wind profile in the main turbulence layers (see e.g. Corteset al. 2012). This method has the evident advantage to provide information onthe turbulence stratification that effectively affects the AO system, propertymore difficultly respected by independently vertical profilers. In this paper,we compare the wind speeds profiles of GeMS with those predicted by anon-hydrostatical mesoscale atmospherical model (Meso-NH). It has been proved(Masciadri et al., 2013), indeed, that this model is able to provide reliablewind speed profiles on the whole troposphere and stratosphere (up to 20-25 km)above top-level astronomical sites. Correlation with measurements revealed tobe very satisfactory when the model performances are analyzed from astatistical point of view as well on individual nights. Such a system appearstherefore as an interesting reference to be used to quantify the GeMS windspeed profiles reliability.