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Comparaison des techniques d’analyse de surface d’onde en plan focal dédiées aux missions spatiales d’imagerie directe et de spectroscopie des planètes extrasolaires

Abstract : Understanding the formation, the evolution and the diversity of extrasolar planets is an important purpose in modern astrophysics. More than 4,000 objects have been discovered since the first discovery of an exoplanet orbiting a solar-type star in 1995. Knowledge about atmospheres of these planets is crucial to determine the conditions for the appearance of life. However, it remains unknown while direct imaging technique would be a powerfull technique to study their spectra.Exoplanet imaging is limited by the large contrast and the small distance which exists between exoplanets and stars. Techniques optimized for high-contrast imaging such as coronography are therefore essential. Coronographs attenuate the light of stars without affecting the fait signal of their circumstellar environments. However, atmospheric turbulence, as well as polishing defects, alignment errors and thermal expansions of telescopes which can vary over time still limit their performance. Techniques dedicated to active correction of aberrations relied on deformable mirrors and wavefront sensors will equip future high-contrast imaging facilities such as WFIRST, HaBEX or LUVOIR spacecrafts or the Extremely Large telescopes.The instrument Très Haute Dynamique 2 (THD2) located at Observatoire de Paris/LESIA is a testbed dedicated to such projects. During this PhD, several wavefront sensor and control algorithms, originally developed by different teams in Europe and the United-States, were tested and compared under the same environmental conditions on the THD2. During these tests, the pair-wise sensor combined with an electric field conjugation technique has also demonstrated excellent contrast performance under spatial conditions, without any modification of the instrument optical path. This method was then implemented on the high-contrast VLT/SPHERE instrument in which we performed improvements in contrast of several orders of magnitude with the calibration unit.
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Submitted on : Monday, July 5, 2021 - 2:20:13 PM
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2020UPSLO012_archivage.pdf
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  • HAL Id : tel-03065844, version 2

Citation

Axel Potier. Comparaison des techniques d’analyse de surface d’onde en plan focal dédiées aux missions spatiales d’imagerie directe et de spectroscopie des planètes extrasolaires. Instrumentation et méthodes pour l'astrophysique [astro-ph.IM]. Université Paris sciences et lettres, 2020. Français. ⟨NNT : 2020UPSLO012⟩. ⟨tel-03065844v2⟩

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