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Mission Analysis Office


by J.P. Arregui and R. Jehn

Produced with the DISCOS Database

February 2007
ESOC Robert-Bosch-Str. 5, 64293 Darmstadt, Germany

<<< Contents

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: o eccentricity smaller than 0.1 o mean motion between 0.9 and 1.1 revolution per sideral day, corresponding approxi mately to a semi-major axis of 42164 ± 2800 km o inclination lower than 20 degrees 911 objects met these criteria as of 31 December 2006. 210 more objects are also known to be in this orbital region although no orbital elements are available in DISCOS. Thus, the total number of known objects in the geostationary region is 1121.

They can be classified as follows:
  • 354 are controlled (238 under longitude and inclination control),
  • 448 are in a drift orbit,
  • 147 are in a libration orbit,
  • 97 are uncontrolled with no orbital elements available,
  • o 7 could not be classified (5 of them were recently launched and are en route to their longitude slot; the other 2 had a recent manoeuvre).
  • 68 are uncatalogued objects but which can be associated to a launch

Additionally we have orbits for 138 unidentified objects. Some of those probably belong to objects where no recent TLEs are available but which are already included in the total number of 1121.

Compared with the last issue of January 2006 the following changes can be observed: There were 28 new objects (26 payloads and 2 rocket bodies) launched into or near GEO during the last year. One object (77092K) was newly catalogued and three objects (72101B and two Meteosat 8 covers) were added. Thus the total number of objects increased by 32 (from 1089 to 1121).

16 spacecraft reached end of life as far as it can be inferred from the orbital elements stored in DISCOS or declared by spacecraft operators. 7 were reorbited more than 270 km above GEO complying with the IADC reorbiting guideline:
  • Intelsat 604 (90056A, 500 x 550 km)
  • Astra IB (91015A, 490 x 515)
  • Inmarsat 2-F3 (91084B, 1190 x 1255)
  • Galaxy IR-A (94013A, US, 290 x 310)
  • N-Star 1 (95044A, Japan, 300 x 350)
  • Raduga 1-6 (01045A, Russia, 650 x 800)
  • Ekspress AM-11 (04015A, Russia, 270 x 315)

7 spacecraft were reorbited into a graveyard orbit below the altitude recommended by IADC:
  • Spacenet 4 (91028A, US) 190 x 210 km above GEO
  • Gorizont 25 (92017A, Russia) 10 x 230 km above GEO
  • Hispasat IB (93048A, Spain) 130 x 180 km above GEO
  • Gorizont 31 (96005A, Russia) 10 x 200 km above GEO
  • Tempo 2 (97011A, US) 230 x 480 km above GEO
  • Thaicom 3 (97016A, Thailand) 60 x 810 km above GEO
  • Feng Yun 2 (00032A, China) 40 x 70 km above GEO

The disposal of Tempo 2 (DirecTV 6) encountered unforeseen difficulties. In August 2006 the spacecraft was raised in a series of four maneuvers to a proper disposal orbit of about 400 km above GEO. At that point the spacecraft still retained some residual propellant. To passivate the spacecraft fully the remaining propellant was burned in a manner which unintentionally resulted in a decrease of the orbital altitude.

2 spacecraft did not perform an end-of-life manouevre: Galaxy 3R (95069A) suffered a catastrophic failure and has started librating now around the Western libration point. Raduga 29 (93013A) was abandoned and librates now around the Eastern libration point.

Two rocket bodies were added to the GEO debris environment: A Proton-K fourth stage (06022D) is drifting 2.6 deg/day eastward in a -420 x 15 km GEO crossing orbit and the apogee kick motor (06053C) of Fengyun 2D is drifting 3.3 deg/day westward in a -195 x 710 km GEO crossing orbit.

This analysis has shown that in 2006, nine years after the IADC guidelines were established, still half of the spacecraft that have terminated their mission are not properly reorbited. It has to be noted though, that all spacecraft which were not properly reorbited (except Fengyun 2), were launched prior to the release of the IADC guidelines. However, the insertion of the Proton-K fourth stage in June 2006 and of the Fengyun 2D AKM is a clear non-compliance with the IADC guidelines.
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. They also thank Eduardo Bellido, Phillipe Cayeux and Franck Raballand for providing background information on individual satellites.

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