36th DPS Meeting, 8-12 November 2004
Session 22 Titan II: Chemistry
Oral, Wednesday, November 10, 2004, 10:30-12:00noon, Lewis

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[22.09] Ground-based observations of Titan's near-infrared windows

A. Negrão (LESIA, Paris-Meudon Observatory, France & Lisbon University, Portugal), A. Coustenis, E. Lellouch (LESIA, Paris-Meudon Observatory, France), P. Rannou (S. A., Univ. Paris 6 - Univ. de Versailles, France), J.P. Maillard (Institut d'Astrophysique de Paris, France)

Titan's surface is hidden under a veil of a thick global aerosol cloud. By applying spectroscopy and imaging from the ground in specific narrow absorption-free windows in the near-infrared, it has been possible to probe down to the lower atmosphere and the surface of Titan. We carried out several spectroscopic observations (between 1991 and 2002), between 0.8 and 2.5 micron, with the Fourier Transform Spectrometer (FTS) at the Canada France Hawaii Telescope (CFHT) and the Infrared Spectrometer And Array Camera (ISAAC) at the ESO Very Large Telescope (VLT). This data set allows us to explore six windows at 0.83, 0.94, 1.07, 1.28, 1.58 and 2 micron at different longitudes and resolutions. These observations complement data taken near the 3 micron window with ISO/SWS (Negrão et al., 2004; Coustenis et al., 2004) and the 5 micron window (Lellouch et al., 2003). These observations taken together give a strong insight on Titan's troposphere and surface. In order to characterize the lower atmosphere's profile and detect particular surface composition, we analysed the data by applying a microphysical and radiative transfer model, with fractal haze particles (Rannou et al., 2003) and varying several atmosphere and surface parameters. In view of upcoming Cassini-Huygens observations, such information from the ground is still very useful for completeness and interpretation of the mission's recordings. References: Negrão et al. (2004), 35th COSPAR C3.2/B0.8-0080-04; Coustenis et al. (2004), submitted to publication; Lellouch et al. (2003), Icarus 162, 125-142; Rannou et al. (2003), Planetary and Space Science 51, 963-976.

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