What is "space debris"

n. All the objects in orbit around the Earth that were created by human activity, but now have no useful purpose

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.

, more than 170 million debris smaller than , about 670,000 debris 1–10 cm, and around 29,000 larger debris are in orbit. , 19,000 debris over are tracked. Below 2000 km 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. 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).

For comparison, the International Space Station orbits in the range and the 2009 satellite collision and 2007 antisat test occurred at . The ISS has Whipple shielding, however known debris with a collision chance over 1/10000 are avoided by maneuvering the spacecraft.

The Kessler syndrome, a runaway chain reaction of collisions exponentially increasing the amount of debris, ensues beyond a critical density. This affects useful polar-orbiting bands, increases the cost of protection for missions and destroys live satellites. Whether it is already underway is debated. The measurement, mitigation and potential removal of debris are conducted by some participants in the space industry.