HIPPARCOS Satellite and the Organization of the Project

A sketch of the past and future development of the project is given. The resulting astrometric parameters and magnitudes of 100000 stars should be available circa 1993. The main features of the satellite are presented. The main limitations that have been identified are discussed: basic angle unstability, mechanical jitter, grid irregularity, diffraction chromatism, shape of the image dissector sensitivity profile. All these effects are taken into account when assessing a final accuracy of 0arcsec.002 for the astrometric parameters of a 9-th magnitude star.