End-of-life disposal of geostationary satellites

For more than 25 years, the practice of reorbiting of a geostationary satellite at the end of its mission in order to protect the GEO environment has been recommended and performed by a number of operators. In recent years, an internationally recognised re-orbiting altitude has been defined by the Inter-Agency Space Debris Coordination Committee (IADC). Based on orbital data contained in the DISCOS database, the situation on the geostationary ring is analysed. In January 2005, from 1124 known objects passing through the geostationary region, 346 are controlled within their allocated longitude slots, 416 are drifting above, below or through GEO, and 143 are in a libration orbit. For 153 objects there is no orbital information available and for 60 uncatalogued objects orbital elements are derived from European measurements. In the eight years from 1997 to 2004, 117 spacecraft reached their end of life; 39 were reorbited in compliance with the IADC recommendation, 41 were reorbited below the minimum recommended altitude, and 37 were abandoned without any end-of-life disposal manoeuvre. Apart from these catalogued objects, the ESA 1-m telescope has observed many smaller debris (down to 10- 15 cm) in this orbital region representing a collision risk for GEO spacecraft which is difficult to quantify.