Space debris

Space debris, junk, waste, trash, or litter is the collection of defunct man-made objects in space – old satellites, spent rocket stages, and fragments from disintegration, erosion, and collisions – including those caused by debris itself. As of December 2016^[update] there were 5 satellite collisions with space waste.

As of July 2013^[update], more than 170 million debris smaller than 1 cm (0.4 in), about 670,000 debris 1–10 cm, and around 29,000 larger debris were estimated to be in orbit. As of 5 July 2016^[update], the United States Strategic Command tracked a total of 17,729 artificial objects, including 1,419 operational satellites. They cause damage akin to sandblasting, especially to solar panels and optics like telescopes or star trackers that can not be covered with a ballistic Whipple shield (unless it is transparent).

Below 2,000 km (1,200 mi) Earth-altitude debris are denser than meteoroids; mostly dust from solid rocket motors, surface erosion debris like paint flakes, and frozen coolant from RORSAT nuclear-powered satellites. For comparison, the International Space Station orbits in the 300–400 kilometres (190–250 mi) range and the 2009 satellite collision and 2007 antisat test occurred at 800 to 900 kilometres (500 to 560 mi) altitude. The ISS has Whipple shielding, however known debris with a collision chance over 1/10000 are avoided by maneuvering the spacecraft.

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