How Much Space
Junk Is Up There?

What is space debris?

Space debris — also called orbital debris or space junk — is any human-made object in Earth orbit that no longer serves a useful purpose. This includes defunct satellites, spent rocket stages, fragments from collisions and explosions, and even small items like tools and paint flakes lost during spacewalks.

The US Space Force tracks objects down to approximately 10cm in low Earth orbit (LEO) and 1 metre in geostationary orbit (GEO). Smaller fragments — estimated in the hundreds of millions — exist but cannot be tracked individually.

The Kessler Syndrome

In 1978, NASA scientist Donald Kessler described a scenario where the density of objects in low Earth orbit becomes high enough that collisions generate debris faster than it naturally deorbits. Each collision creates more fragments, which cause more collisions — a self-sustaining cascade.

This isn't science fiction. The 2009 Iridium-Cosmos collision and the 2007 Chinese ASAT test together added thousands of tracked objects and hundreds of thousands of untracked fragments to the LEO environment. Some of that debris will remain in orbit for decades.

Current models suggest certain orbital bands in LEO are already past the critical density threshold — meaning debris growth in those shells is now self-sustaining even with no new launches.

How fast does debris travel?

Objects in low Earth orbit travel at approximately 7–8 km/s (25,000 km/h). At those speeds, even a 1cm fragment carries the kinetic energy of a hand grenade. A 10cm object would be catastrophic to any spacecraft it struck.

The ISS performs regular debris avoidance manoeuvres — typically a few times per year — when tracked objects pass within a few kilometres. For untracked debris, the station's whipple shield provides some protection against fragments smaller than about 1cm.

Will it get worse?

The mega-constellation era has dramatically accelerated object counts. SpaceX Starlink alone has launched over 7,000 satellites, with plans for up to 42,000. Amazon Kuiper, China's Qianfan, and others plan thousands more. Most operate in LEO below 600km, where atmospheric drag naturally deorbits satellites within a few years — but the sheer number increases collision risk during operations.

Active debris removal remains largely at the research stage. ESA's ClearSpace-1 mission, targeting a single Vega rocket adapter piece, is the first contracted debris removal mission. At current launch rates, removal missions would need to dramatically outpace new object creation to meaningfully reduce debris density.

How is debris tracked?

The US Space Surveillance Network (SSN) operates a global network of radars and optical telescopes to track objects in Earth orbit. Data is maintained in the Space-Track catalogue, operated by the 18th Space Defense Squadron. The catalogue contains orbital elements for every tracked object, updated continuously.

OrbitalNodes uses this same Space-Track data to power its live satellite tracker. The pass predictions, constellation tracking, and reentry alerts on this site all derive from the same catalogue that the ISS uses for conjunction analysis.