Analysis of near-infrared spectra of Titan using a GCM model
Résumé
Titan was observed using the Fourier Transform Spectrometer (FTS) at the Canada France Hawaii Telescope (CFHT), between 1991 and 2002, in the 0.8-2.5 micron range at different longitudes and resolutions. The data in this region were complemented with observations taken with the Short Wave Spectrometer instrument on the Infrared Space Observatory, which was used to uncover the 3 micron methane window. Because in the near-infrared methane is the main absorber it is possible to take profit of its variable absorption in this region to probe different levels in Titan's atmosphere. The observational data set includes six methane windows at 0.94, 1.07, 1.28, 1.58, 2.0 and 2.75 micron where the methane absorption is negligible and the solar light reaches the surface. Using these two data sets, we retrieved some atmospheric characteristics and surface spectra of Titan using the haze vertical profile and optical characteristics predicted by a General Circulation Model (Rannou et al., 2004). These results were then compared with the ones obtained with a 1D plane parallel microphysics and radiative transfer model (Coustenis et al., 2005; Rannou et al., 2003, Toon et al., 1989). Finally the surface spectra obtained with the GCM, was then compared with the spectra of possible surface constituents.