Space debris

In low orbit, between 160 and 1800 kilometres from the Earth, there is a debris belt. Old satellites, parts of expended rocket stages, the remains after explosions and accidents make up a dangerous assemblage of debris.

Today, some 450 active satellites are in orbit around the Earth. They are outnumbered by the more than 7000 pieces of debris. Moreover, there are some 120,000 fragments of less than one centimetre circumference each. These small fragments can be scraps of paint, parts of solar panels, screws, nuts and other small items. Though small, these fragments pose a hazard, because they move at speeds of up to six kilometres a second.

Space debris often causes problems. Satellites can be damaged if hit by space debris. The same applies to launchers, manned spacecraft, and the space station. Recently the station had to make adjustments to its orbit to avoid being hit by debris.

Space debris is bothersome and dangerous. Worst yet, the amount of it is increasing at a rate of about five percent a year. We’ll probably never get rid of the debris now floating in space.

However, we now think more about the future, and we’re better at disposing of old satellites.

The best way to dispose of an old satellite is to guide it back toward Earth so it burns up in the atmosphere. But that requires propellant, and some old satellites have no more propellant.

An alternative for geostationary satellites is to direct them outward into a graveyard orbit, which is a debris belt more than 40,000 km above Earth. There, old and faithful satellites orbit for eternity, their transmitters off and their propellant tanks empty.