Gaia flight model during mass, CoG (Centre of Gravity) and inertia measurements at Intespace, Toulouse, France, 13 March 2013.

Gaia will create a three-dimensional map of the Milky Way, in the process revealing information about its composition, formation and evolution. The mission will perform positional measurements for about one billion stars in our Galaxy and Local Group with unprecedented precision, together with radial velocity measurements for the brightest 150 million objects. Gaia is scheduled to launch in 2013 for a nominal five-year mission, with a possible one-year extension.

The spacecraft will operate in a Lissajous orbit around the second Lagrange point of the Sun-Earth system (L2). This location in space offers a very stable thermal environment, very high observing efficiency (since the Sun, Earth and Moon are all behind the instrument FoV) and a low radiation environment. Uninterrupted mapping of the sky will take place during the operational mission phase.