Gaia observations of Solar System objects: Impact on dynamics and ground-based observations

The Gaia mission will observe all asteroids and other small Solar System objects for 5 years, at a magnitude limit V ∼ 20. The expected precision for each observation is around 0.2 mas at V ∼ 15, or 2 mas at V ∼ 20. At this level, subtle dynamical effects due to mutual gravitational interactions or non-gravitational forces are measurable. In particular, several deflections of small asteroid trajectories due to close encounters with the largest masses in the belt will be detected. The deflection measurement is the main technique employed to derive asteroid masses by Earth-based observations. However, due to the high sensitivity of the Gaia astrometry, the simultaneous deviations due to several masses will be detected, and will require a specific method of investigation. The same applies to the Yarkovsky thermal effect measurements, that will be present in the observations and that demands specific orbital inversion algorithm to be taken into account. At the end of the mission, the knowledge of ∼100 masses at 10% level and several measurements of the Yarkovsky effect can be expected.