Understanding the numbers

What counts?

The count includes every human-made object in Earth orbit that is large enough to be tracked by the U.S. Space Surveillance Network — roughly anything larger than 10 cm. This includes working satellites, retired satellites, spent rocket stages, and fragments from collisions or deliberate destructions.

Objects too small to track — estimated at over 100 million pieces below 1 cm — are not included in this count, but they still pose significant collision risks at orbital speeds.

Why space debris matters

At orbital velocities, even a 1 cm paint flake carries the kinetic energy of a hand grenade. A collision between two large objects can create thousands of new fragments, each one a potential threat to other spacecraft.

That's how fast objects travel in low Earth orbit — roughly 7.8 km per second. At that speed, relative collision velocities can exceed 14 km/s, making even tiny fragments lethal to spacecraft.

How the count is measured

Orbital objects are tracked by the U.S. Space Force's 18th Space Defense Squadron (18 SDS) using a global network of ground-based radar and optical sensors, including the powerful Space Fence on Kwajalein Atoll.

This data is made publicly available through Space-Track.org and CelesTrak, maintained by Dr. T.S. Kelso. Our data is sourced from CelesTrak's satellite catalog, which is updated several times daily.

Limitations

This count represents publicly tracked, cataloged objects only. Some classified military satellites may not appear in the public catalog. Very small debris (under ~10 cm in LEO, or ~1 m in GEO) is generally too small to track and is not included. The true number of objects in orbit is significantly higher than what is shown here.