Space debris is any non-functional, human-made object in Earth orbit — from spent rocket stages and dead satellites to paint flecks and fragmentation shards. There are over 36,000 tracked objects larger than 10 cm and an estimated 130 million pieces larger than 1 mm, all travelling at speeds up to 28,000 km/h.
Understanding Space Debris
Where Does Debris Come From?
The majority of tracked debris originates from just a handful of catastrophic events. The 2007 Chinese anti-satellite test (Fengyun-1C) created over 3,500 trackable fragments. The 2009 Cosmos–Iridium collision — the first accidental hypervelocity collision between two intact satellites — added roughly 2,300 more. The 2021 Russian ASAT test (Kosmos-1408) generated over 1,500 fragments directly threatening the ISS crew. Additional sources include upper stages that were not passivated (drained of residual fuel), shedding thermal blankets, and even tools lost during EVAs.
Why Size Matters
| Size | Estimated Count | Trackable? | Impact Effect |
|---|---|---|---|
| > 10 cm | 36,500 | Yes (radar/optical) | Catastrophic — destroys satellite |
| 1–10 cm | 1,000,000 | Partially (Space Fence) | Catastrophic to mission-ending |
| 1 mm – 1 cm | 130,000,000 | No | Can penetrate shields, damage subsystems |
| < 1 mm | Trillions | No | Surface erosion, sensor degradation |
Mitigation and Removal
Debris mitigation follows the 25-year rule (increasingly being replaced by a 5-year target) and passivation requirements. For the existing population, active debris removal (ADR) missions — using robotic arms, nets, harpoons, or magnetic capture — are under development by companies like Astroscale and ClearSpace. The first demonstrator missions are already in orbit, targeting specific defunct objects for controlled deorbit.