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Conference papers

Discovery of an Ozone Layer on Venus by SPICAV on Venus Express

Abstract : The SPICAV instrument onboard the Venus Express spacecraft is a multi-channel suite covering the far ultraviolet to the mid-infrared. In this presentation, we will focus on the results obtained by the UV channel during stellar occultations observations. Stellar occultation technique possesses well-known advantages: self-calibration, low sensitivity to instrument aging, simple laws of radiative transfer. In addition, occultation with stars permit to cover a broad range of latitudes at any given season and they provide optimal geometrical registration. Since Venus Express orbit insertion, several hundreds of occultations have been performed by SPICAV, yielding profiles of atmospheric constituents between 80 and 140 km. In the SPICAV UV range, CO2 possesses a broad signature shortward of 200 nm which allows one to retrieve CO2 concentration and subsequently to deduce atmospheric pressure and temperature profiles in the upper mesosphere and in the thermosphere. The Venusian thermosphere shows excessive variability, with the equivalent of more than three scale heights change in density in less than a few days. No other spectral signature besides that of CO2 and haze particles was expected to appear in SPICAV ultraviolet spectra at this altitude range but a consistent search was undertaken, revealing the presence of ozone at 100 km (<108 cm-3) and of sulfur dioxide above 90 km at a concentration of 0.1 to 1 ppm.
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Submitted on : Monday, February 6, 2012 - 4:34:17 PM
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Franck Montmessin, Jean-Loup Bertaux, Franck Lefèvre, A. Vandaele, O. Korablev, et al.. Discovery of an Ozone Layer on Venus by SPICAV on Venus Express. 41st Annual Meeting of the Division for Planetary Sciences (DPS), Oct 2009, Puerto Rico, United States. ⟨hal-00667028⟩



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