Classification of Geostationary Objects

This paper lists all geostationary and near-geostationary objects contained in ESA's DISCOS database.     

International Practices to Protect the Geostationary Ring

Since more than 20 years reorbiting of geostationary satellites at the end of their mission is recommended and partially performed to protect the GEO environment. Now a worldwide accepted reorbiting altitude was defined by the Inter-Agency Space Debris Coordination Committee (IADC). Still only one-third of the aging satellites follow this IADC rule. Based on orbital data in the DISCOS database, the situation in the geostationary ring is analyzed. From 878 known objects, 305 are controlled inside their longitude slots, 353 are drifting above, below or through GEO, and 125 are in a libration orbit (status of January 2001). In the last four years (1997–2000) 58 spacecraft reached end-of-life. Twenty of them were reorbited in compliance with the IADC recommendations, 16 were reorbited below this recommendation and 22 were abandoned without any end-of-life disposal manoeuvre.     

Navigating BepiColombo during the weak-stability capture at Mercury

BepiColombo is scheduled for launch in August 2013 and to arrive after a nearly six-year long transfer at Mercury in June 2019. The trajectory has a number of challenging elements: a launch with Soyuz/Fregat into a geostationary transfer orbit, followed by a lunar flyby, long low-thrust arcs and five more planetary flybys (one at the Earth, two at Venus and two at Mercury). At arrival the low thrust arcs reduce the approach velocity so much that BepiColombo passes by the Sun–Mercury Lagrange points L₁ and L₂ and gets weakly captured in a highly eccentric orbit around Mercury in case the orbit insertion manoeuvre would fail.This paper describes the navigation strategy during the final phase. Five trajectory correction manouevres during the last 65 days requiring up to 20 m/s (3σ) are proposed. With this strategy it is possible to navigate BepiColombo safely through the weak-stability boundary of Mercury and to reach the target periherm with a precision of 11 km.