THE REFERENCE FRAMES IN THE DATA REDUCTION OFHIPPARCOS SATELLITE

The heliotropic, great-circle and Hipparcos telescope reference frames are explicitly defined in the light of the scanning law of Hipparcos satellite. The differences between the reference frames adopted by the two data reduction consortia, FAST and NDAC, are presented. The abscissas and ordinates of 50 stars in the FAST and NDAC great-circle reference frame are simulated and the reason for using two data reduction consortia in ESAare discussed.