Space Debris
Any human-made object in orbit that no longer serves a useful function, including defunct satellites, spent rocket stages, and fragments from collisions or breakups.
Explanation
Space debris ranges from paint flakes millimeters across to intact but inoperative satellites the size of a bus. The U.S. Space Surveillance Network tracks over 45,000 objects larger than 10 cm, while estimates for smaller debris (1-10 cm) exceed 500,000 pieces, and microdebris under 1 cm numbers in the hundreds of millions. The Kessler Syndrome — a cascade where collisions generate fragments that cause more collisions — is the worst-case scenario for debris proliferation. Major debris-generating events include the 2007 Chinese ASAT test, the 2009 Iridium-Cosmos collision, and the 2021 Russian ASAT test. Mitigation measures include post-mission disposal (PMD), passivation (venting stored energy), and design-for-demise. Active debris removal (ADR) missions are under development by agencies including ESA (ClearSpace-1) and JAXA (ELSA-d). The FCC now requires orbital debris mitigation plans for all U.S.-licensed satellite systems.
Why It Matters
Space debris threatens all space operations. A single collision can destroy an active satellite and create thousands of trackable fragments. Debris mitigation and removal are among the most pressing policy and engineering challenges in space today.
Concept Map
How Space Debris connects to other glossary terms:
Frequently Asked Questions
How much space debris is there?
Over 45,000 tracked objects larger than 10 cm, an estimated 500,000 pieces between 1-10 cm, and over 100 million particles smaller than 1 cm.
Can space debris be cleaned up?
Several active debris removal missions are in development. ESA's ClearSpace-1 plans to capture and deorbit a Vespa payload adapter. Commercial efforts like Astroscale's ELSA-d demonstrate rendezvous and capture technologies.
Sources
Last updated: July 1, 2026