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low Earth orbit

Low Earth orbit, the region up to roughly 2,000 kilometres above the Earth's surface where the great majority of active satellites operate, has become noticeably more crowded over the past decade, driven largely by the rapid deployment of large satellite constellations. Alongside those active satellites sits a much larger population of debris: spent rocket stages, defunct satellites, fragments from past collisions and anti-satellite weapons tests, and small pieces of hardware shed during normal operations. Tracking agencies catalogue tens of thousands of objects large enough to monitor individually, and estimate a far larger population of untracked fragments too small to follow reliably but still large enough to destroy a functioning satellite on impact.

• Roughly 30,000-plus objects are large enough (generally above about ten centimetres) to be individually tracked and catalogued.
• Untrackable fragments below that threshold are estimated to number from the hundreds of thousands into the millions.
• A 2007 Chinese anti-satellite weapons test and a 2009 collision between an active and a defunct satellite each generated large, long-lived debris fields still being tracked today.
• Large satellite constellations have substantially increased the number of active objects sharing low Earth orbit and, correspondingly, the number of collision-avoidance manoeuvres operators must perform.