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Caractérisation de la turbulence optique pour la Haute Résolution Angulaire: Étude de l'interaction entre la couche de surface et la coupole des grands télescopes de type E-ELT

Abstract : In order to improve the observation with High Angular Resolution the telescopes acquire diameters of considerable size. The optimization of these large telescopes like E-ELT requires a characterization of the site as well as the specification of their enclosure. Using an experimental study carried out in the site of the VLT (Paranal) we show that the vertical characterization of the turbulence given by the profiles of Cn2 and outer scale is more representative of the real conditions of observation. Knowing, that the site which will receive the future E-ELT is situated at only few kilometers of Paranal, these results will be used to define the specifications of the compensation systems planned for this new generation of large telescopes. This study also allowed the determination of the surface layer where we established an estimate of its altitude and energy. It has been shown that the surface layer contributes significantly to the degradation of the incoming wavefront. Its localization close to the ground raises questions about its interaction with the telescope's enclosure which are of the same size. LOTUCE a new instrument developed during this work was proposed to study the interaction of this surface layer with the enclosure. Using the measurement of the angles of arrival (AA) on different points of the wavefront, LOTUCE gives an estimate of the optical parameters of turbulence as the Fried parameter, the coherence time and the outer scale. The modelling of local turbulence is then possible by studying the curves of covariance of the AA in the two directions longitudinal and transverse. The last part of this work concerns the temporal evolution of optical turbulence. This study is based on the estimate of the coherence time determined from the statistical analysis of the fluctuations of AA. This method used by GSM was validated by a numerical simulation. These results show that this parameter is more sensitive to the conditions of measurements and the instrumentals constraints.
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Contributor : Wassila Dali Ali <>
Submitted on : Tuesday, November 5, 2013 - 4:20:55 PM
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Wassila Dali Ali. Caractérisation de la turbulence optique pour la Haute Résolution Angulaire: Étude de l'interaction entre la couche de surface et la coupole des grands télescopes de type E-ELT. Instrumentation et méthodes pour l'astrophysique [astro-ph.IM]. Université Nice Sophia Antipolis, 2011. Français. ⟨NNT : 20708008⟩. ⟨tel-00880253⟩

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