Census of the Galaxy: Challenges for Photometry and Spectrometry with GAIA: Proceedings of the Workshop held in Vilnius, Lithuania 2-6 July 2001

Astrometry from space was performed for the first time and with great success by the ESA Hipparcos satellite (1989-93). This mission was designed as an as­ trometry mission, but the use of a photon counting detector made it possible to produce very important photometric results: the most accurate astronomical pho­ tometry ever by the main Hipparcos mission in a very broad band of 120000 stars, and the two-colour Tycho-2 photometry of 2.5 million stars. The cornerstone ESA mission GAIA was a...