Abstract
The GAIA astrometric mission of ESA will be very efficient in discovering binary and multiple stars with any orbital period, from minutes to millions of years. The main parameters of the revised mission design are presented. Next we estimate the fraction of binary stars discovered by means of astrometry, photometry and on-board spectroscopy. Finally we summarize observations that confirm the ability to measure physical parameters like masses, radii and spectroscopic distance from GAIA data alone. GAIA will fly only in 2010, but the radial velocity experiment (RAVE) has started this year. We show that its spectroscopic observations have the capacity to discover a large fraction of so far unknown binary systems.
