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Étude des nuages de Vénus par polarimétrie avec les données de l’instrument SPICAV-IR à bord de Venus Express

Loïc Rossi 1
1 IMPEC - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : Venus is quite similar to Earth in terms of mass and radius, but it appears to be a hellish planet with surface temperature reaching 700 K and pressions up to 92 bars. The atmosphere is mostly composed of carbon dioxyde and despite a slow retrograde rotating solid body, the atmosphere is in superrotation with a period of about four days and zonal winds reaching 100 m/s at cloud top level. In visible light, the surface is always hidden by thick decks of clouds mostly made of sulfuric acid. These clouds are very important in venusian climate as they play a key role in the radiative balance of the planet because of their opacity and their high albedo and also in the chemical cycles of sulfur especially. In orbit since 2006, the European space agency’s probe Venus Express had the objective to study the atmosphere and clouds of Venus. Amongst its instruments was the SPICAV spectrometer which infrared channel had the ability to measure the degree of linear polarisation from the light scattered by the clouds. This thesis aims to study these observations acquired by SPICAVIR until the end of the mission in 2014.We will introduce the planet Venus with a particular focus on the cloud layers. We will then cover the principles of the polarisation of light through scattering by cloud particles before we introduce the measurement of polarization by our instrument. We also introduce the radiative transfer model taking into account polarization and apply it to the observations of a phenomenon called glory which allows to characterize the properties of the cloud droplets. We will then invesigate the variability of the haze layers lying above the main cloud deck.
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https://hal-insu.archives-ouvertes.fr/tel-01327236
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Submitted on : Monday, June 6, 2016 - 3:18:41 PM
Last modification on : Friday, January 10, 2020 - 3:42:29 PM

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Loïc Rossi. Étude des nuages de Vénus par polarimétrie avec les données de l’instrument SPICAV-IR à bord de Venus Express. Physique Atmosphérique et Océanique [physics.ao-ph]. Université Versailles Saint-Quentin-En-Yvelines (UVSQ), 2015. Français. ⟨tel-01327236v1⟩

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