The term "space debris" in its largest sense includes all naturally occurring remains of solar and planetary processes: interplanetary dust, meteoroids, asteroids, and comets. Human-made space debris in orbit around Earth is commonly called orbital debris. Examples include dead satellites, spent rocket bodies, explosive bolt fragments, telescope lens covers, and the bits and pieces left over from satellite explosions and collisions.

Orbital debris is found wherever there are working satellites. Of the more than 9,000 objects larger than 10 centimeters (3.94 inches) in Earth orbit, 94 percent are debris. The densest regions are low Earth orbit (LEO), an altitude range from 400 to 2,000 kilometers (248.5 to 1,242.7 miles) above Earth; and geosynchronous Earth orbit (GEO) at 35,786 kilometers (22,300 miles), sometimes called the Clarke orbit, where the orbital period of a satellite is one day. More than 100,000 particles between 1 and 10 centimeters (0.39 and 3.94 inches) are thought to exist and probably tens of millions of times smaller...