
Gaia is the European space mission whose objective is to map the sky with an unprecedented precision of a few millionths of an arcsecond and a depth of up to magnitude 21. The PISI is responsible for two "Units of Coordination” of Gaia, and plays a key role in this project by coordinating the work of respectively 50 and 30 European scientists and engineers. The first three published star catalogs, including nearly 2 billion sources, have already enabled more than 12. 000 publications and important discoveries about our Galaxy, the solar system and nearby galaxies.