Published online by Cambridge University Press: 25 September 2002
GAIA will likely be a real milestone for asteroid science. Itsunprecedented astrometric accuracy can be exploited to compute orbitsbetter than those obtained by using the whole set of availableastrometric observations carried out from ground during the last 100 years. GAIA will make it possible to measure asteroid masses throughthe measurement of the tiny displacements caused by asteroid mutualencounters. This will be a major breakthrough for physical studies ofminor planets. Moreover, sizes will be also directly measured for abig sample of more than 1000 objects. From masses and sizes, estimatesof the average densities will be also obtained. The spectrophotometriccapability of GAIA will be used for purposes of taxonomicclassification, with important implications for surface mineralogicalcharacterization. Finally, GAIA will be an ideal platform to detectnear-Earth asteroids having orbits interior to that of the Earth.