Source: http://proxy.osapublishing.org/oe/abstract.cfm?uri=oe-22-9-10948
Timestamp: 2019-04-20 15:20:37+00:00

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COupled SLope and scIntillation Detection And Ranging (CO-SLIDAR) is a recent profiling method of the vertical distribution of atmospheric turbulence strength ( Cn2 profile). It takes advantage of correlations of slopes and of scintillation, both measured with a Shack-Hartmann wavefront sensor on a binary star. In this paper, we present the improved CO-SLIDAR reconstruction method of the Cn2 profile and the first on-sky results of the CO-SLIDAR profiler. We examine CO-SLIDAR latest performance in simulation, taking into account the detection noise bias and estimating error bars along with the turbulence profile. The estimated Cn2 profiles demonstrate the accuracy of the CO-SLIDAR method, showing sensitivity to both low and high altitude turbulent layers. CO-SLIDAR is tested on-sky for the first time, on the 1.5 m MeO (Métrologie Optique) telescope at Observatoire de la Côte d’Azur (France). The reconstructed profiles are compared to turbulence profiles estimated from meteorological data and a good agreement is found. We discuss CO-SLIDAR’s contribution in the Cn2 profilers’ landscape and we propose some improvements of the instrument.
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Fig. 1 Example of simulated Shack-Hartmann turbulent and noisy images. (a) Full Shack-Hartmann long-exposure image. (b) Subaperture short-exposure image.
Fig. 2 Correlation maps from simulated slope and scintillation data. One pixel of these maps shows the correlation averaged over all pairs of subapertures with given separation. (a), (b), (c) Auto-correlation maps. (d), (e), (f) Cross-correlation maps. (a), (d) Correlations of x-slopes. (b), (e) Correlations of y-slopes. (c), (f) Correlations of scintillation.
Fig. 3 (a) ML reconstruction of the C n 2 profile from correlations of slopes only, of scintillation only and with the CO-SLIDAR method, in simulation. In all cases, the detection noise bias has been estimated jointly with the C n 2 profile. (b) Absolute error on the reconstruction.
Fig. 4 ML CO-SLIDAR reconstruction of the C n 2 profile, with joint estimation of the detection noise bias and with exclusion of the variances from the direct problem, in simulation.
Fig. 5 ML CO-SLIDAR reconstruction of the C n 2 profile, with joint estimation of the detection noise bias, and with the estimated 3σ error bars, in simulation.
Fig. 6 (a) ML and MAP CO-SLIDAR reconstructions of the C n 2 profile and comparison with the reconstruction from correlations of scintillation only, in simulation. (b) Absolute error on the reconstruction.
Fig. 7 Experimental Shack-Hartmann turbulent images, for a 3 ms exposure time. (a) Full Shack-Hartmann long-exposure image. (b) Subaperture short-exposure image.
Fig. 8 Correlation maps from experimental slope and scintillation data. (a), (b), (c) Autocorrelation maps. (d), (e), (f) Cross-correlation maps. (a), (d) Correlations of x-slopes. (b), (e) Correlations of y-slopes. (c), (f) Correlations of scintillation.
Fig. 9 ML reconstruction of the C n 2 profile from correlations of slopes only, of scintillation only and with the CO-SLIDAR method. 1 min dataset acquired around 01:00 UT, on May 15 th , 2012, with a 3 ms exposure time. In all cases, the detection noise bias has been estimated jointly with the C n 2 profile.
Fig. 10 ML CO-SLIDAR reconstruction of the C n 2 profile, with joint estimation of the detection noise bias and with exclusion of the variances from the direct problem. 1 min dataset from May 15 th , 2012, around 01:00 UT.
Fig. 11 ML and MAP CO-SLIDAR reconstructions of the C n 2 profile. 1 min dataset from May 15 th , 2012, around 01:00 UT.
Fig. 12 (a), (b), (c) MAP CO-SLIDAR reconstructions of the C n 2 profile with the estimated 3σ error bars, for three consecutive minutes of observation. Each profile corresponds to one minute of observation. Data from May 15 th , 2012, around 01:00 UT.
Fig. 13 MAP CO-SLIDAR reconstruction of the C n 2 profile. 1 min dataset from May 15 th , 2012, around 01:00 UT. Comparison with the free atmosphere profile at 00:00 UT and with the mean profile of May 2012, deduced from NCEP/NCAR Reanalysis.

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