1989: Rescuing satellites

The ESOC Flight Dynamics room in the early 1980s.
12 December 2007

The ABM firing - a routine job for ESOC staff - did not succeed. This was unprecedented. True, the GEOS-1 satellite had also failed to reach its geostationary orbit in 1977, but that was because the launcher had underperformed. Never before in ESA's history had an Apogee Boost Motor failed.


Excerpted from "How to Survive in Space: A light-hearted chronicle of ESOC," Vol. II 1963-1986 by Madeleine Schäfer. In Chapter 7, it's 1989, and Hipparcos - an ambitious mission aimed at mapping stars with unprecedented accuracy - suffers an on-board failure that taxes the ingeniuity of ESOC engineers.


Meteosat was successful, but Hipparcos soon proved to be a completely different kettle of fish. Hipparcos was launched together with the German TV-SAT II on 8th August 1989. In an article in the ESOC News a year after the event, Jozef van der Ha, the Hipparcos Ground Segment Manager, described the occasion:
The satellite operations during the Transfer Orbit phase went much more smoothly than during any of the pre-launch simulations and it seemed as if we could look forward to an extremely "smooth" mission.

Spirits were high in ESOC and everyone was happy that finally the many years of hard preparatory work came to fruition. On Thursday, 10th August, just after 14.00 hr (local), the Apogee Boost Motor (ABM) was to be fired to place Hipparcos in the geostationary orbit for which it had been designed.
The ABM firing - a routine job for ESOC staff - did not succeed.

Unprecedented motor failure calls for quick reaction

Artist's impression of Hipparcos mapping the stars

This was unprecedented. True, the GEOS-1 satellite had also failed to reach its geostationary orbit in 1977, but that was because the launcher had underperformed. Never before in ESA's history had an Apogee Boost Motor failed.

Five attempts were made to fire the ABM, but it remained obdurate. Now what? If there was to be the slightest chance of recouping at least a small percentage of the mission objectives, it was obvious that the satellite could not remain in its present transfer orbit.

It would be exposed to the radiation effects of the van Allen belts during parts of each orbit, which would degrade the solar arrays such that there would not be enough power for it to survive eclipses.

To cut a long story short, on 7th September the first of a series of manoeuvres was executed to raise the satellite's perigee to 500 km. The apogee remained at 36 000 km.

In a geostationary orbit Hipparcos would have been in continuous contact with its ground station in the Odenwald; now, with its elliptical orbit this was not possible. Auxiliary stations at strategic positions round the earth were required.

Hipparcos revised orbit (click for full view)

In what was perhaps ESOC's fastest station upgrading action since TD-1A in 1972, equipment for the stations at Perth and Kourou was procured, installed, tested and verified, and both stations were fully operational by mid-September and early November respectively.

Additional help came from NASA in the form of their ground station at Goldstone in the Mojave desert in California.

Things were looking up.

By March 1990 Hipparcos could be 'seen' almost 93% of its orbit, and it was possible to acquire data about 70% of the time.

Like some bored, petty dictator, it required of its attendants not only technical expertise but also a number of other, rather unusual, qualifications: ingenuity, a strong sense of humour, and patience, patience, patience.

ESOC gave birth to a small world, which was almost completely self-contained, and whose sole purpose in life was to dance attendance, day and night, on Hipparcos' needs.

To the outsider, this world assumed a dreamlike quality - the links to ESOC reality seemed tenuous.

Within this world, however, the ailing satellite was the be-all and end-all.

Like some bored, petty dictator, it required of its attendants not only technical expertise but also a number of other, rather unusual, qualifications: ingenuity, the ability to jump to attention at any time of night or day, a robotic capacity for extremely long shifts, a cast-iron stomach, a strong sense of humour, and, last but not least, patience, patience, patience.

The Hipparcos Mission ended in 1993 after over three years of highly successful operations.

Excerpted from:

"How to Survive in Space: A light-hearted chronicle of ESOC, Vol. II 1963-1986," Madeleine Schäfer (C) 1997 European Space Agency

Madeleine Schäfer joined ESDAC - the predecessor of ESOC - on 22 June 1964 as short-hand typist and secretary; there were just seven scientific and support staff at the time. She retired in 1997.

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