ABSTRACT

In the present earth particulate environment, for hazardous objects larger than 1mm, man-made space debris are already prevailing over the natural meteoroid and cosmic dust background. Most of these debris were caused by about 120 on-orbit fragmentations of upper stages of rockets, or by spacecraft break-ups. Following these events, some altitude regions have already attained critical concentrations which could ultimately trigger collision chain reactions and make portions of the near-earth space unsave for manned operations. This paper will describe concepts of the European Space Agency for the mitigation of space debris which could assist in the preservation or improvement of the space environment. The outline of ESA debris mitigation measures will cover the formulation of related design and operation policies for space systems under ESA control, and give examples of the implementation of such measures for the reorbiting of GEO spacecraft and for the passivation of Ariane upper stages after their mission completion.

INTRODUCTION

Currently, some 7,000 trackable space objects are orbiting the earth. This population is the remainder of a total of 22,000 objects which have been tracked operationally by NORAD and USSpaceCom (its successor for space surveillance) since Sputnik-1 was launched in 1957. The other 15,000 objects have mostly reentered and burnt up in the earth atmosphere, or have been retrieved by controlled reentry or by the Space Shuttle. Almost 50% of the observable space population can be correlated with more than 120 historic on-orbit fragmentation events, each of which typically generated 120 to 200 trackable debris objects.