Un livre blanc Allianz : Space Risks : a new generation of challenges
"The space around our planet is becoming increasingly congested. Since the beginning of space exploration in 1957, mankind has been leaving behind debris that continuously collides, producing thousands of fragments. The amount of fragmented debris in Low Earth Orbits, or LEOs, is so dense that atmospheric erosion alone cannot solve the problem of overcrowding. For this reason, standard practice is now to deorbit all satellites at the end of their lives. But thousands of objects remain in these orbits, where they pose a serious collision threat to space missions. In 2010, and again in 2011, the crew of the International Space Station (ISS) was forced to evacuate on shortnotice when a piece of space debris came perilously close to colliding with the space station. On both occasions, the object was detected too late for the crew to perform an avoidance maneuver. The space station is in a LEO, an orbit around our planet just above the atmosphere (see diagram on page 10). At altitudes between 300 km and 2,000 km, the risk of collision is mostly due to man-made debris, particularly defunct satellites and decommissioned launch vehicles in upper LEO levels, which have not been deorbited. More than 12,000 debris objects measuring at least 10 cm across have been cataloged in this part of space. The number of smaller items is even greater but they are too small to observe or track, making them all the more dangerous."