SOLAR OCCULTATION BY TITAN MEASURED BY CASSINI/UVIS
Résumé
We present the first published analysis of a solar occultation by Titan’s atmosphere measured by the Ultraviolet Imaging Spectrograph on board Cassini. The data were measured during flyby T53 in 2009 April and correspond to latitudes between 21 deg and 28 deg south. The analysis utilizes the absorption of two solar emission lines (584 Å and 630 Å) in the ionization continuum of the N2 absorption cross section and solar emission lines around 1085 Å where absorption is due to CH4. The measured transmission at these wavelengths provides a direct estimate of the N2 and CH4 column densities along the line of sight from the spacecraft to the Sun, which we inverted to obtain the number densities. The high signal-to-noise ratio of the data allowed us to retrieve density profiles in the altitude range 1120–1400 km for nitrogen and 850–1300 km for methane. We find an N2 scale height of ∼76 km and a temperature of ∼153 K. Our results are in general agreement with those from previous work, although there are
some differences. Particularly, our profiles agree, considering uncertainties, with the density profiles derived from the Voyager 1 Ultraviolet Spectrograph data, and with in situ measurements by the Ion Neutral Mass Spectrometer with revised calibration.
Domaines
Planétologie et astrophysique de la terre [astro-ph.EP] Instrumentation et méthodes pour l'astrophysique [astro-ph.IM] Astrophysique stellaire et solaire [astro-ph.SR] Océan, Atmosphère Physique Atmosphérique et Océanique [physics.ao-ph] Analyse de données, Statistiques et Probabilités [physics.data-an] Instrumentations et Détecteurs [physics.ins-det]
Origine : Fichiers produits par l'(les) auteur(s)
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