Etude des émissions de monoxyde d'azote (NO), observées en ultraviolet par SPICAV/Venus Express, en mode d'occultation stellaire

Emilie Royer 1
1 IMPEC - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : NO airglow is observable on each terrestrial planets surrounded by an atmosphere. On Venus, this emission have been identified in 1979. It is classicaly observed in ultraviolet, between 180 and 300 nm, but it is possible to detect it in infrared, between 1.2 and 1.3 μm too. NO nightglow is du to radiative recombinaison process occuring on the night side of the planet. Venus' atmosphere is essentially composed of CO2 and N2 and on the day side, solar radiations break this molecules and make the N and O atoms free. In the upper atmosphere, above 100 km, zonal winds transport these atoms to the night side where they recombine to form NO and emit an ultraviolet radiation. NO nightglow is thus a good tracer of this sub-solar/anti-solar circulation. The Venus Express mission, currently in orbit around Venus, possess the SPICAV instrument onboard. It is a spectrometer which is able to observe NO nightglow in ultraviolet. This thesis work is based on SPICAV observations realised in the stellar occultation mode. This data set, on which NO nightglow appears, allows to expand the data base on airglow and allows a complementary approach to limb observations. This work consist in the establishment of two NO nightglow data's inversion methods. The first method, called forward model, is a simulation of what it should be seen with SPICAV during stellar occultation. The second method, called algorithm of inversion, is a matricial inversion of the data. Both methods reach to the characteristics of the NO layer present in the atmosphere of Venus. Our results allow to better constrain the dynamical context of the Venusian atmosphere, at altitudes above 100 km.
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Emilie Royer. Etude des émissions de monoxyde d'azote (NO), observées en ultraviolet par SPICAV/Venus Express, en mode d'occultation stellaire. Astrophysique [astro-ph]. Université Pierre et Marie Curie - Paris VI, 2011. Français. ⟨tel-00595054⟩

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