Delbo, M. ; Tanga, P. ; Mignard, F. ; Carry, B. ; Dell'Oro, A. ; Hestroffer, D. ; Granvik, M. ; Muinonen, K. ; Pauwels, T. ; Petit, J.-M. ; Thuillot, W.

published in IAU General Assembly, 22, pp. 2255084 (2015)

Abstract: The astrometric mission Gaia of the European Space Agency (ESA) was launched in December 2013 and started the scientific phase of its 5-years-long, whole-sky survey in July 2014. Gaia characterise all astrophysical sources with V=20, by measuring their position, motion and spectral properties. The high-precision astrometry (~25 micro-arcsec at V=15) is the unbeatable science driver of Gaia, promising a revolution in astrophysics, with the first data release in 2016.Solar system objects are serendipitously observed in the visible light by Gaia wide-field telescopes, with these observations providing astrometry and colour photometry for ~250,000 asteroids.Here, we report on the analysis of Gaia observations performed by the Data Processing and Analysis Consortium (DPAC). Regarding astrometry, the most important products are epoch positions of minor bodies and the stellar catalogue that will be used to improve the orbits of virtually all observed solar system bodies.We will detail how, from measurements of the orbital gravitational perturbations on small asteroids that have close encounters with more massive ones, Gaia data will allow the determination of the masses of about 150 of the largets asteroids, with important repercussion on dynamical and physical models of our solar system.Furthermore, Gaia is observing several near-Earth asteroids. For those with the longest arc, Gaia observations could help the detection of the drift in orbital semi-major axis due to the Yarkovsky effect. Beyond the Gaia observations themselves, one of the most important improvements for solar system science will be the Gaia stellar catalogue. This will allow recalibrating all astrometric (and photometric) measurements of solar system minor bodies obtained so far, with important improvements in the measurements of drift of the orbital semi-major axes of asteroids, in the modelling of the spreading of asteroid families, and in the ephemeris of the planets.

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