GAIA is an ESA mission building on the original work done by the Hipparcos mission in the 1990s. It is a five year mission from a satellite placed at the L2 Lagrangian point. Gaia will map a billion stars in the Milky Way with unprecedented precision and provide data about their size, luminosity and temperature. The 1Petabyte of data retrieved over five years will provide astronomers with more precise data than ever before on the positions, movement and origin of stars in our galaxy.
Visit the ESA pages from here>http://www.esa.int/Our_Activities/Space_Science/Gaia_overview