SOLAR-SYSTEM STUDIES IN THE INFRARED RANGE - RECENT DEVELOPMENTS AND FUTURE-PLANS

A large fraction of our knowledge about the structure and composition of planetary and cometary atmospheres has come from infrared spectroscopy. In the case of giant planets, information on the thermal structure and the abundances ratios of these objects was derived from ground-based IR spectroscopy and from the VOYAGER IRIS infrared data. Saturn's satellite Titan was mostly explored by the VOYAGER mission, and in particular the IRIS instrument. Terrestrial planets, although already investigated by in-situ means, have also recently benefited from near-infrared (NIR) imaging spectroscopy. Finally the study of comets has known a very important development over the past years with the increasing use of infrared and millimeter spectroscopy. Future progress can be foreseen, for both ground-based and space observations. Ground-based studies will benefit from the use of bidimensional near-infrared cameras and their coupling with high-resolution spectrometers. Another promising field of research should be associated with the use of millimeter interferometers, and the extension of heterodyne spectroscopy toward higher frequencies. In the case of space research, a significant improvement is expected from two Earth-orbiting missions: ISO, in the infrared range, and later FIRST, in the submillimeter region. More in-depth studies of specific objects will be performed with the infrared instruments on specific space probes: Mars Observer and MARS-94 for Mars, GALILEO for Jupiter, CASSINI for Saturn and Titan, and later ROSETTA for a long-term cometary exploration.