Launch and Mission Operations Phase

The satellite, launched from Kourou, French Guyana, into a geostationary transfer orbit on 8 August 1989, failed to reach its nominal geostationary orbit after failure of its apogee boost motor. Following the revised mission implementation, however, further operations proceeded nominally, although major revisions in the operational procedures had to be developed and implemented by the ESOC operations control centre. The satellite was eventually tracked by three ground stations - Odenwald (Germany), Perth (Australia) and the NASA Goldstone station (USA) - compared with the single ground-station originally foreseen. Details of the post-launch operations have been published in ESA Bulletin 64 and in Volume 2 of The Hipparcos and Tycho Catalogues.

Major effort was devoted at ESOC to the smooth running of the Hipparcos satellite, maximising its scientific return, and developing contingency procedures to overcome anomalies that occurred during the satellite operations. The satellite remained fully functional in the revised orbit for more than three years after launch. Progressive deterioration of certain satellite subsystems, due to radiation damage in the highly elliptical orbit, led to several months of operations using only two of the three intended gyroscopes. Plans were in hand to operate the satellite without gyroscopes, on the basis of an ambitious redesign of the on-board and on-ground systems, but eventual loss of communication with the on-board computer finally led to the termination of satellite operations on 15 August 1993.

A full description of the Hipparcos satellite operations is given in Volume 2 of The Hipparcos and Tycho Catalogues, which gives background information on the satellite and payload, in addition to describing the interfaces with the Scientific Consortia, payload and spacecraft performances, and real-time attitude control and determination.