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Mission Analysis Office


by I. Serraller and R. Jehn

Produced with the DISCOS Database

January 2005
ESOC Robert-Bosch-Str. 5, 64293 Darmstadt, Germany

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7. Summary

All geostationary or near-geostationary objects catalogued in ESA's DISCOS Database (Database and Information System Characterising Objects in Space) are listed in this document. An object is considered as geostationary or near-geostationary if it meets the following criteria:
  • eccentricity smaller than 0.1
  • mean motion between 0.9 and 1.1 revolution per sideral day, corresponding approximately to a semi-major axis of 42164 ± 2800 km
  • inclination lower than 20 degrees
869 objects met these criteria as of 31 December 2004. 255 more objects are also known to be in this orbital region although no orbital elements are available in DISCOS. Thus, the total number of objects in the geostationary region is 1124. They can be classified as follows:

They can be classified as follows:
  • 346 are controlled (221 under longitude and inclination control),
  • 416 are in a drift orbit,
  • 143 are in a libration orbit,
  • 88 are uncontrolled with no orbital elements available,
  • 6 could not be classified (3 of them were recently launched and are en route to their longitude slot; the other 3 had a recent manoeuvre).
  • 65 are uncatalogued objects but which can be associated to a launch
  • 60 are unidentified objects

Compared with the last issue of January 2004 the following changes can be observed: There were 23 new objects (18 payloads and 5 rocket bodies) launched into or near GEO during the last year.

13 spacecraft reached end of life as far as it can be inferred from the orbital elements stored in DISCOS (or declared by spacecraft operators): five were reorbited more than 300 km above GEO: Astra 1A (88109B), GSTAR 4 (90100B, US), Insat II R (92010B, India, previously Arabsat 1C), GOES 8 (94022A, US) and PAS 6 (97040A, US). Five spacecraft were reorbited into a graveyard orbit below the altitude recommended by IADC:
  • Morelos 2 (85109B, Mexico) 180 x 220 km above GEO,
  • Brazilsat 2 (86026B, Brazil) 170 x 190 km above GEO,
  • Telecom 2B (92021A, France) 195 x 225 km above GEO,
  • Insat IIB (93048B, India) 9 x 160 km above GEO,
  • Galaxy 8-i (97078A, US) 145 x 180 km above GEO,

Comstar 4 (81018A, Tonga) and Zhongxing 6 (97021A, China) seemed to have been abandoned around the Eastern stable point last year. ACTS (93058B, US) was moved to 105° W already in August 2000 after it was realised that the propellant reserves revealed a much lower amount than expected. However, it was only decommisioned on 28 April 2004 (source: Orbital Debris Quaterly News, July 2004).

In 2004 five rocket upper stages were added to the GEO debris environment:
  • Three Russian Proton-K fourth stages: 04010F was left in an orbit -100 x 180 km passing through GEO, 04015D was left below GEO (-192 x -53 km) and 04043D was left very low above GEO (15 x80 km).
  • One Chinese apogee kick motor (04042C) was left in a -390 x -200 km orbit below GEO
  • One US upper stage (04004D) was launched towards GEO, but no orbit data is available.

This analysis has shown that the IADC reorbiting recommendations were only partially followed by the spacecraft operators. A more rigorous control of the reorbiting practices in GEO is required to preserve this unique resource.
8. References
1. Samsom P., "Classification of Geostationary Objects", ESOC - MAS WP 420, 1999.
9. Acknowledgements
The authors thank Nicholas Johnson and Vladimir Agapov for their suggestions and valuable contributions.

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