Gaia: an unprecedented tool for Solar System Science
Résumé
Detailed investigations of the capabilities of the Gaia mission have revealed its strong potential for the exploration of scientific issues related to Solar System. This satellite will be placed in the Earth L2 and is expected to provide ˜ 70 observations (composed of ultra-precise astrometric measurements and magnitudes) of all the celestial bodies brighter than V 20, over 5 years of nominal operation. The observed objects will include ˜ 5x105 Main Belt Asteroids, ˜ 103 Near Earth Objects, the bright Trans-Neptunian Ojects, several comets, and many of the natural satellites of the major planets. Gaia observations will be characterized by an unprecedented astrometric accuracy (better than 1 mas per observation at V 15), the availability of multi-band photometry, and the virtually perfect knowledge of the attitude of the spaceraft relatively to a global astrometric reference. This points constitute the real strength of the mission, allowing to determine accurate sizes for ˜ 1000 asteroids and masses for > 100 objects, an improvement of a factor ˜ 100 in the orbital elements uncertainties, spin pole, shapes, and rotation periods for nearly all the observed objects, and a simultaneous determination of the PPN beta parameter and of the solar J2. The amount of physical data available, that will increase of several orders of magnitude relatively to the present situation, can be considered as a revolutionary step in Solar System science.