Hipparcos project main reduction operations within the fast consortium

Abstract A brief overview of the HIPPARCOS data reduction software system operated at CNES for the FAST consortium is given /1/. The main function of this system is the scientific processing of the HIPPARCOS data, from the photon counts of the stars observed to the astrometric parameters with a very high accuracy of 0.002 arc sec. The major aspects of the cooperative development, the qualification and the operation of this reduction system are presented. This system was designed for the geostationary nominal mission. Its behaviour with respect to the real data of the revised mission, defined after the failure of the apogee boost motor, is analysed. A first evaluation of the usable data, available at the preprocessing level is proposed.