TRACKING ORBIT ~40,000 tracked objects in orbit · source ESA Space Environment Report 2025 · as of 2025
ReentryOrbit, debris & frontier tech
Reentry

Satellite and rocket reentry

Everything in low orbit is slowly falling. This section covers how satellites and spent rocket stages come back through the atmosphere, what survives the trip, and the reentries worth remembering.

Where things orbit, and where they come down

The altitude ledger

Reentry is a question of altitude. Read this from the top down, from the high orbits where debris lingers for centuries to the reentry interface near 120 kilometers, where the atmosphere takes over.

35,786 km
Geostationary (GEO)

Communications satellites, and a graveyard orbit where retired ones are parked above the working belt.

2,000 km +
Medium Earth orbit

Navigation constellations such as GPS and Galileo. Debris here can persist for centuries.

~1,000 km
Upper low Earth orbit

The most crowded debris shells: defunct satellites and collision fragments that will not decay for decades.

~420 km
ISS orbit

The International Space Station and many crewed missions. Air drag here is real, so the station needs regular reboosts.

~200 km
Decay zone

Below this, air drag pulls objects down within days to weeks. Nothing stays up for long.

~120 km
Reentry interface

Where atmospheric heating begins in earnest. An object crossing this line is committed to coming down.

0 km
Surface

Most material burns up before here. Dense tanks and alloys sometimes reach the ground.

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