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Theses

Effet de la turbulence optique sur l'astrométrie solaire par imagerie

Abstract : The objective is to understand the effect of optical turbulence on ground-based solar radius measurements. The measurement of the solar radius with accuracy is important for models of solar and stellar structure and evolution. In addition solar activity has an evident influence on the terrestrial climate. The work focused on the calibration and exploitation of data obtained by two telescopes: SODISM2 dedicated to the measurement of the solar radius by full-disk imaging, and MISOLFA a turbulence monitor which allows to estimate the turbulence spatio-temporal parameters. The first measurements of MISOLFA show its capacity for the extraction of turbulence profiles and integrated parameters from the angle-of-arrival fluctuations observed on the solar edge. The spatial parameters estimated from the intensity fluctuations in the pupil plane show a good agreement with the parameters coming from the image plane. The first measurements of the angle-of-arrival characteristic time have also been obtained which give an average value of 5.3 ms over a year of measurements. SODISM2 is the qualification model of an instrument on board the PICARD satellite (2010-2014). The first measurements of this instrument show a high stability and a dispersion of the order of 200 mas (milli-arcseconds). A downward trend on the order of 12 mas/year was also observed but it is not significant given the dispersion of the measurements. A new method was developed for obtaining flat fields using contrast maps. Numerical simulations of imaging through turbulence show a systematic bias introduced by the effect of the turbulence parameters on the estimation of the radius and the limb width
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Rabah Ikhlef. Effet de la turbulence optique sur l'astrométrie solaire par imagerie. Autre. Université Côte d'Azur; Université M'hamed Bougara de Boumerdès (Algérie), 2016. Français. ⟨NNT : 2016AZUR4113⟩. ⟨tel-01493127⟩

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