L2 - Gaia
Gaia will operate in the vicinity of the second Lagrange point (L2), approximately 1.5 million km from the Earth, along the Sun-Earth line in the direction opposite to the Sun. The region around L2 is a gravitational saddle point, where spacecraft can be maintained at roughly constant distance from the Earth for several years by small and cheap manoeuvres.
More information about the L2 orbit is available here.
copyright: François Mignard