15min:

V. BOUDON, Institut Carnot de Bourgogne, UMR 5209 CNRS-Université de Bourgogne, 9. Av. A. Savary, BP 47870, F-21078 Dijon Cedex, France; A. COUSTENIS, E. LELLOUCH, P. DROSSART, LESIA, Observatoire de Paris-Meudon, 5 Place Jules Jansen, F-92195 Meudon Cedex, France; A. NEGR AO, Observatorio Astronomico and Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal; C. A. GRIFFITH, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, 85721 USA.

The advent of the Cassini-Huygens mission studying Saturn's system and its largest moon Titan, has led to a renewed interest in reliable models of the absorption spectrum of methane. CH₄ is the main absorber in Titan's thick atmosphere. Although the models developed in the Dijon group still do not allow sufficently reliable simulations above 5000 cm^-1 to reproduce all the recent data (such as Huygens/DISR spectra, for instance), the methane coefficients in the 0--4800 cm^-1 region have contributed to a better understanding of various ground- and spaced-based data : ISO high-resolution data in the 3 µm region\footnoteA. Coustenis, A. Negrao, A. Salama et al.\/ Icarus\/ 180, 176--185 (2006)., near-infrared VLT data\footnoteA. Negrao, A. Coustenis, E. Lellouch et al.\/ Planet. Space Sci.\/ 54, 1225--1246 (2006). and 2 µm VLT data of the Huygens probe landing site\footnoteA. Negrao, M. Hirtzig, A. Coustenis et al.\/ J. Geophys. Res. Planets\/ 112, E02S92 (2007).. These coefficients have also contributed to the discovery of a polar ethane cloud on Titan\footnoteC. A. Griffith, P. Penteado, P. Rannou et al.\/ Science\/ 313, 1620--1622 (2006).. Models of CH₄ hot bands by the Dijon group are also of primary importance for fluorescence calculations observed at 3.3 µm with Cassini/VIMS. After a short review of these works, future prospects for line-by-line analyses of CH₄ spectra for planetary applications will also be discussed and compared to other approaches, such as the so-called band models or purely experimental approaches.