Status of the Hipparcos Data Reduction

Abstract

HIPPARCOS is now well settled on its 10h40m eccentric orbit and the data is received by three telemetry stations that are also transmitting commands: Odenwald (F.R.G.), Perth (Australia) and Goldstone (California). Although during about 80 to 90% of the time, data are recovered, in practice only the observations made from higher than the outer Van Allen belt are usable. Sometimes even at that height, on-board attitude determination does not converge due to the noise that covers the star mapper signal. Finally, about between 55 and 65% of the mission time is usable for reduction. The actual routine data recovery started on November 27, 1989.