EUROPEAN SPACE AGENCY
EUROPEAN SPACE OPERATIONS CENTRE
GROUND SYSTEMS ENGINEERING DEPARTMENT
Space Debris Office

CLASSIFICATION OF GEOSYNCHRONOUS OBJECTS
ISSUE 10
by R. Choc and R. Jehn
Produced with the DISCOS Database

February 2008
ESOC Robert-Bosch-Str. 5, 64293 Darmstadt, Germany

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 30 degrees

934 objects met these criteria as of 31 December 2007. 216 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 1150. They can be classified as follows:

• 365 are controlled (243 under longitude and inclination control),
• 462 are in a drift orbit,
• 148 are in a libration orbit,
• 99 are uncontrolled with no orbital elements available,
• 9 could not be classified (six of them were recently launched and are en route to their longitude slot).
• 67 are uncatalogued objects but which can be associated to a launch

Additionally we have orbits for 146 unidentified objects. Some of those belong to objects where no TLEs are available but which are already included in the total number of 1150.

Compared with the last issue of January 2007 the following changes can be observed: There were 24 new objects (22 payloads and 2 rocket bodies) launched into or near GEO during the last year. One object (68081J) was newly catalogued, one operational fragment (from launch 07054) was added and the three spacecraft from launch 06024 are included in the total count. Thus the total number of objects increased by 29 (from 1121 to 1150).

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. 8 were reorbited more than 290 km above GEO and therefore complied with the IADC reorbiting guidelines:

• Nato IV A (91001A, 530 x 600 km)
• Meteosat 5 (91015B, EUMETSAT, 490 x 550 km)
• Satcom C4 (92057A, UK, 340 x 370 km)
• DirecTV-2 (94047A, USA, 410 x 520 km)
• GOES 9 (95025A, USA, 410 x 430 km)
• Fengyun-2 1R (97029A, China, 800 x 1650 km)
• BSAT-1b (98024B, Japan, 295 x 340 km)
• Thuraya 1 (00066A, United Arab Emirates, 330 x 400 km)

3 spacecraft were reorbited into a graveyard orbit with a perigee between 250 and 270 km above GEO. A forward propagation over 200 years showed that they will not enter the 200-km protected zone around GEO. Therefore, they are also complying with the IADC guidelines.

• Hot Bird 1 (95016B, EUTELSAT) 258 x 283 km above GEO
• JCSat 3 (95043A, Japan) 265 x 372 km above GEO
• N-Star 2 (96007A, Japan) 255 x 318 km above GEO

1 spacecraft was reorbited too low:

• Gorizont 26 (92043A, Russia) 160 x 420 km above GEO

And 1 spacecraft seems to be abandoned and has started librating around the Eastern stable point:

• Raduga 30 (93062A, Russia)

There were two retirements of classified US satellites in the year 2006 which were not reported in the last issue. Both USA 65/DSP F15 (90065A) and USA 140/UFO F9 (98058A) were raised by more than 500 km.

This analysis has shown that in 2007, ten years after the IADC guidelines were established, the proper reorbiting of GEO spacecraft is becoming a standard procedure with less and less exceptions.

1. Samsom P., "Classification of Geostationary Objects", ESOC - MAS WP 420, 1999.

The authors thank Nicholas Johnson and Vladimir Agapov for their suggestions and valuable contributions.