HIPPARCOS : an Example of Astrophysical Uses of Astrometric Data.

Hipparcos will measure positions, proper motions and parallaxes for about 110,000 stars brighter than B = 13, with an expected mean error of 2×10^-3arcsec in positions and parallaxes and 2×10^-3arcsec/year in proper motions. The contents of the first provisional catalogue with respect to astrophysical problems is described, and the star distribution versus spectral type, magnitude and distance is given.