Space debris

Space debris consists of nonfunctional human-made objects and fragments left in orbit around Earth or other celestial bodies. It ranges from intact spacecraft and rocket stages to fragments created by collisions or breakups.

Orbital debris collision: A collision between orbiting objects that can damage or destroy them and produce additional debris. Collisions can turn existing debris and active spacecraft into clouds of hazardous fragments.
Space situational awareness: The monitoring and interpretation of objects and activity in space to support safe operations. It combines debris observations with orbit prediction to inform spacecraft operators.
Sputnik 1: The first artificial Earth satellite, launched by the Soviet Union on October 4, 1957. Its launch began the era of sustained human activity that has populated Earth orbit with objects.
Active satellite: An artificial satellite that is operating or otherwise remains functional in orbit. An operational satellite is not debris, even when it occupies a crowded orbital region.
Satellite collision avoidance: The planning and execution of spacecraft maneuvers to reduce the risk of collision with another object. Debris warnings can force costly maneuvers and interrupt satellite operations.
Kessler syndrome: A proposed cascade in which collisions among orbiting objects generate enough debris to make further collisions increasingly likely. It describes how debris-producing collisions could compound in crowded orbital regions.
Space debris tracking: The observation and cataloging of debris objects to estimate their positions and orbits. Tracking supplies the measurements needed to assess conjunctions and characterize the debris population.
Kosmos 954: A Soviet nuclear-powered reconnaissance satellite that reentered over Canada in 1978, scattering radioactive debris. Its uncontrolled reentry exposed the environmental consequences of defunct spacecraft.
Meteoroid: A small natural object moving through interplanetary space, smaller than an asteroid. Meteoroids are natural impact hazards, unlike human-made orbital debris.
Satellite megaconstellation: A large network of satellites designed to provide broad coverage or frequent service from orbit. Large constellations increase the number of active objects requiring coordination with debris.

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