CNES OPERATIONAL PRACTICES FOR SPACE DEBRIS RISK LIMITATION AND PROTECTION

The question of debris becomes a more and more important problem for t he the space activity. III tile future, the limitation of debris produ ction will be obtained, not only through tile design of the spacecraft s,but also through operational practices, until now. there is no ''rul es of the road'' ill space but operational practices are discussed at international level and give birth to recommandations: some of these p ractices are already studied and implemented at CNES for tile control of satellites. One important source of debris production in space come s from tile potential collisions between satellites or between a satel lite and a debris. This risk is managed at different levels: during th e operational life time, the problem is twofold: first it is necessary to avoid collisions of an operational satellite with any object in sp ace. these objects. space debris, operational or dead satellites, are registered in data bases. Secondly it is often necessary to share the useful orbit between several satellites. It's the case in geostationar y orbit, where telecommunication or television missions require that s everal satellites are kept on station at the same longitude: this impl ies adapted manoeuvres strategics to keep tile satellites in the same window, at short distances, but without any risk of collision. It's al so tile case for the SPOT family of Earth observation satellites shari ng the same heliosynchronous orbit. at the end of life, as the operati onal useful orbits are overcrowded, the practice is to put the satelli te out of these orbits, in order to let the place free for the new sat ellites to be launched. In geostationary orbit this is done by moving the satellites on a graveyard orbit above the geostationary altitude. In the contrary, for low Earth orbits which is the case of observation satellites, the objective is to lower the altitude to use the atmosph eric drag which will induce the destructive re-entry of the satellite in the atmosphere. This paper presents the main theoretical studies on the subject, the description of the operations already performed on s atellites controlled by CNES and the main results. (C) 1997 Internatio nal Astronautical Federation. Published by Elsevier Science Ltd.