1ANID Millennium Nucleus in Applied Control and Inverse Problems (ACIP) (Chile) 2Pontificia Univ. Católica de Chile (Chile) 3Univ. Lyon, Univ. Lyon1, ENS de Lyon, CNRS, Ctr. de Recherche Astrophysique de Lyon (France)
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Laser-based adaptive optics telemetry contains information about the atmospheric vertical profiles of turbulence strength (C2n), outer scale (L0) and wind speeds. Various techniques in the literature already process laser-based Shack-Hartmann telemetry and estimate the profiles out of cross-covariance maps from the slopes data. Building local derivative estimates out of the data (i.e. curvatures or even higher-order derivative estimates) is a possible mean to remove the large uncertainties existing on low-order modes in laser-based systems. The present study analyses this filtering strategies in a unified formalism. The modified shapes of the cross-covariance peaks are studied and compared. It explains how the sensitivity to the outer scale is strongly reduced by using such higher- order derivative estimates than slopes. The sharpened covariance peaks also simplify the layer detection problem in atmospheric profiling and may improve vertical resolution of SLODAR-based techniques. As a first application of this analysis, an automated algorithm for turbulence profiling is presented with results on simulated data and also on on-sky registered data from the Adaptive Optics Facility at Paranal Observatory.
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