Towards a reliability assessment of the C²_Nand wind speed vertical profiles retrieved from GeMS

Abstract

The advent of a new generation of Adaptive Optics systems called Wide Field AO (WFAO) mark the beginning of a new era. By using multiple Guide Stars (GSs), either Laser Guide Stars (LGSs) or Natural Guide Stars (NGSs), WFAO significantly increases the field of view of the AO-corrected images, and the fraction of the sky that can benefit from such correction. Different typologies of WFAO have been studied over the past years. They all require multiple GSs to perform a tomographic analysis of the atmospheric turbulence. One of the fundamental aspects of the new WFAO systems is the knowledge of the spatio-temporal distribution of the turbulence above the telescope. One way to get to this information is to use the telemetry data provided by the WFAO system itself. Indeed, it has been demonstrated that WFAO systems allows one to derive the C 2 N and wind profile in the main turbulence layers (see e.g. Cortes et al. 2012 1 ). This method has the evident advantage to provide information on the turbulence stratification that effectively affects the AO system, property more difficultly respected by independently vertical profilers. In this paper, we compare the wind speeds profiles of GeMS with those predicted by a non-hydrostatical mesoscale atmospherical model (Meso-NH). It has been proved (Masciadri et al., 2013 2 ), indeed, that this model is able to provide reliable wind speed profiles on the whole troposphere and stratosphere (up to 20-25 km) above top-level astronomical sites. Correlation with measurements revealed to be very satisfactory when the model performances are analyzed from a statistical point of view as well on individual nights. Such a system appears therefore as an interesting reference to be used to quantify the GeMS wind speed profiles reliability.

Towards an automatic wind speed and direction profiler for Wide Field adaptive optics systems

“…GeMS is the first laser assisted MCAO system running on sky and this study proves, for the first time, that the SLO-DAR technique method for the wind estimate with multiple sources provides reliable results as in agreement with an independent reference previously validated. Besides that, the development of other WFAO systems is in progress for the 8-10 m class telescopes (among these we remind AOF 5 at For completeness we observe that in a couple of papers (Neichel et al 2014b;Masciadri et al 2016) some preliminary results of these study have been published. In the first one just some preliminary WS comparisons on a very small number of nights has been presented.…”

Towards an automatic system for monitoring of CN2and wind speed profiles with GeMS

“…We used the same model configuration used in Neichel et al [ 2 ] with three domains in grid-nesting configuration having resolution of 10 km, 2.5km and 0.5 km. We simulated 43 nights for which GeMS telemetry data were available.…”

“…In this contribution we performs the comparison between wind speed measured by GeMS and reconstructed by the atmospherical model at mesoscale Meso-Nh on a rich statistical sample of 43 nights with the goal to provide a more complete analysis with respect to Neichel et al 2014 [ 2 ] and we present preliminary results related to the wind direction. In a previous study, indeed, Masciadri et al, 2013Masciadri et al, , 2015 ] showed that the non-hydrostatical mesoscale atmospherical model Meso-Nh was able to provide reliable wind speed and direction profiles on the whole troposphere and stratosphere (up to 20-25 km) above top-level astronomical sites.…”

PEPITO: atmospheric Profiling from short-Exposure focal Plane Images in seeing-limiTed mOde

“…At present, profiling using AO instruments is performed from the cross-correlation of Wave-Front Sensor (WFS) measurements (Laidlaw et al 2018;Mazzoni et al 2016;Ono et al 2017;Martin et al 2016;Neichel et al 2014;Vidal et al 2010), with profile height limits of ∼ 10-20 km imposed principally by the telescope diameter, and then additionally the cone effect for laser-based AO (Foy 2000). However, such an approach is only available on multiple GSbased systems and can not be deployed to predict PSF variations on images delivered by single-conjugated AO systems.…”