Orbital pollution

A few estimates

At the moment, 12,000 bits of debris larger than 10 cm have been listed on different orbits by the American network. There were 9,100 in 2007. There are hundreds of thousands of pieces between 1 and 10 cm, tens of millions between 0.1 and 1 cm and particles below one millimetre are quite uncountable.

At an altitude of 940 km, debris with a diameter greater than 0.1 cm are responsible for more impacts than the meteorites found naturally in that environment. They are of much more danger to objects orbiting ‘up there’ than to anything ‘down here’ on Earth. In all, this collection of sundry objects weighs about 5,000 tonnes out of more than 20,000 tonnes originally launched.

30 years of examples, on the ground and ‘up there’

-24/01/1978: fall-back of the Russian satellite, Cosmos 954, which contained a nuclear reactor. Six hundred km² of Canada’s Far North were contaminated. Two more in the same series of satellites fell back in 1983 on South Africa and into the Indian Ocean.

-11/07/1979: atmospheric re-entry of the abandoned American Space laboratory, Skylab: about 20 tonnes of debris did not burn up and were scattered across several thousand kilometres of Australia.

- 1991: fall of the Russian Salyut 7 Space Station, of which a few pieces did not burn up and were found within a few hundred kilometres of Buenos Aires.

- 21/07/1996: the stabilisation mast of the Cerise satellite was sectioned by a piece of debris resulting from the explosion of an Ariane stage launched 10 years earlier. First official collision between an operating satellite and debris.

- 23/03/2001: controlled atmospheric re-entry of Russia’s MIR Space Station over the Pacific Ocean, above a maritime corridor 6,000 km long and 200 km wide.

- 11/01/2007: in a demonstration of force, China voluntarily destroyed one of its obsolete weather satellites with a ground-based missile. More than 1500 pieces of debris >10 cm catalogued.

- 17/02/2007: as the result of an engine failure, the upper stage of a Russian  Briz-M was unable to perform fluids passivation. Condemned to wander through Space with its reservoirs full, it exploded, perhaps caused by other debris. More than 1000 pieces of debris >10 cm catalogued. As the book Pollution spatiale sous surveillance puts it: “It is interesting to note that after inaccurate injection of the satellite, considerable efforts were made to de-orbit the Arabsat 4A satellite, that had become useless; these efforts, for the removal of a single object from Space, may be compared with the thousand-odd pieces of debris produced by simple negligence.”

- 10/02/2009: first collision between two satellites: an inactive Russian military satellite weighing 900 kg unfortunately crossed the path of an operating American telecommunications satellite weighing 560 kg. Close to 1000 pieces of debris >10 cm identified.

- 12/02/2009: when the risk of collision between the International Space Station and debris was identified too late for avoidance manoeuvres, the astronauts on board had to take temporary refuge in the Soyuz escape capsule.

- 24/02/2009: after the launch attempt was aborted, the third stage of the Taurus launcher containing the American CO₂ detection satellite fell back into the Arctic Ocean.

Near-Earth Objects (NEOs)

On Monday 2 March 2009, the asteroid 2009DD45 swept past the Earth at a distance of only 72,000 km, only one fifth of the distance between the Earth and the Moon. This is almost negligible when measured on an astronomical scale. Indeed, in 2004 a smaller ‘meteoroid’, 2004FU162, could have given us a friendly wave from only 6,500 km. If 2009DD45, estimated at between 21 and 47 metres across and travelling at 31,000 kph, had crashed into our planet it would have caused damage comparable to the catastrophe that occurred on 30 June 1908 in Siberia when a falling meteorite caused a gigantic explosion, with an energy equivalent to a thousand times the power of the bomb dropped on Hiroshima, destroying fauna and flora over 2000 km².

Les géocroiseurs, ces objets qui croisent la Terre

Lundi 2 mars 2009, l’astéroïde 2009DD45  a "frôlé" la surface de la Terre à quelques 72 000 km, soit seulement un cinquième de la distance Terre-Lune. A l’échelle astronomique, autant dire rien. Notons qu’en 2004, son compère 2004FU162 était passé dire bonjour à seulement 6 500 km. Avec un diamètre estimé entre 21 et 47 mètres, à une vitesse de 31 000 km/h, l’impact de 2009DD45  sur la planète aurait pu être comparable à la catastrophe du 30 juin 1908 en Sibérie. La chute d’une météorite avait alors causé une gigantesque explosion, dont l’énergie était équivalente à mille fois la puissance de la bombe tombée sur Hiroshima, ravageant faune et flore sur une surface de 2000 km².