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Hipparcos satellite survives the long eclipse season
4.1. HIPPARCOS SATELLITE SUWIVES THE LONG ECLIPSESEASON”’
The ESA astrometry satellite Hipparcos, which attracted great attention in August 1989 when it failed to reach its allocated geostationary orbit after launch, has emerged successfully from a further critical test of its on-board control systems. “Soon after the satellite became trapped in its highly elliptical transfer orbit, we realized that the power system would face a crucial test around mid-March, when the satellite would remain in the Earths shadow” said Dr Hamid Hassan, Hipparcos Project Manager. Indeed, during a three week period, the solar arrays were illuminated for a much shorter interval of time than had been foreseen in its nominal circular orbit, and the satellite had to survive long intervals each day solely on its battery power. As the maximum eclipse duration, of about 105 minutes on 16 March, approached, careful contingency plans were made at the ESA operations control centre at ESOC, near Darmstadt, FRG, to shut down elements of the payload so that the power drain on the batteries would not be excessive. The power margins on the spacecraft were such that the satellite passed the maximum eclipses with a margin of barely 5 minutes, allowing the scientific measurements to proceed without interruption and guaranteeing the continued operation of Hipparcos. The same week saw the coming on line of the fourth ground station to be included into the Hipparcos ground station tracking network. The NASA Goldstone station in the Mohave Desert, California, now supplements the operational stations at Darmstadt, Perth (Australia) and the CNES station at Kourou, French Guiana. ESA and NASA personnel gave high priority to the task of bringing the Goldstone station into the network two weeks before the original target date, thus improving the amount of useful data that can be collected from the satellite. The ESA Project Scientist, Dr M. Perryman, speaking from the Agency’s research centre in the Netherlands, remains cautiously optimistic that the Hipparcos project will be a success. “We have known since November that the technology and system concept underlying the Hipparcos mission has been fully demonstrated. With the successful emergence from the long eclipse season, and good prospects that the satellite can survive for another two and a half years, the original scientific goals of the mission may still be within our grasp”.
(‘)From ESA News Release No. 9,27 March 1990.
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The ESA astrometry satellite Hipparcos, which attracted great attention in August 1989 when it failed to reach its allocated geostationary orbit after launch, has emerged successfully from a further critical test of its on-board control systems. “Soon after the satellite became trapped in its highly elliptical transfer orbit, we realized that the power system would face a crucial test around mid-March, when the satellite would remain in the Earths shadow” said Dr Hamid Hassan, Hipparcos Project Manager. Indeed, during a three week period, the solar arrays were illuminated for a much shorter interval of time than had been foreseen in its nominal circular orbit, and the satellite had to survive long intervals each day solely on its battery power. As the maximum eclipse duration, of about 105 minutes on 16 March, approached, careful contingency plans were made at the ESA operations control centre at ESOC, near Darmstadt, FRG, to shut down elements of the payload so that the power drain on the batteries would not be excessive. The power margins on the spacecraft were such that the satellite passed the maximum eclipses with a margin of barely 5 minutes, allowing the scientific measurements to proceed without interruption and guaranteeing the continued operation of Hipparcos. The same week saw the coming on line of the fourth ground station to be included into the Hipparcos ground station tracking network. The NASA Goldstone station in the Mohave Desert, California, now supplements the operational stations at Darmstadt, Perth (Australia) and the CNES station at Kourou, French Guiana. ESA and NASA personnel gave high priority to the task of bringing the Goldstone station into the network two weeks before the original target date, thus improving the amount of useful data that can be collected from the satellite. The ESA Project Scientist, Dr M. Perryman, speaking from the Agency’s research centre in the Netherlands, remains cautiously optimistic that the Hipparcos project will be a success. “We have known since November that the technology and system concept underlying the Hipparcos mission has been fully demonstrated. With the successful emergence from the long eclipse season, and good prospects that the satellite can survive for another two and a half years, the original scientific goals of the mission may still be within our grasp”.
(‘)From ESA News Release No. 9,27 March 1990.
35