Orbital decay
Every satellite in low Earth orbit is slowly falling. The only question is how fast. Orbital decay is the process that drags spacecraft out of the sky — and it is happening to objects tracked in the catalogue right now.
What is orbital decay?
// the mechanicsOrbiting is really just falling sideways. A satellite stays up because it is moving sideways fast enough that its path curves around the Earth at the same rate it falls. The problem is that space is not quite empty: even at 400–800 km altitude, a few stray air molecules remain, and every pass through them steals a tiny amount of speed.
That drag is orbital decay. Lose speed and the orbit shrinks; shrink the orbit and the air gets denser, which steals more speed. The process feeds on itself. For a healthy satellite at 550 km, the effect is gentle — months or years to matter. For an object already low, it accelerates quickly toward the end.
The endgame is reentry. Eventually the drag becomes strong enough that the object stops circling and falls. Most spacecraft are designed to deorbit deliberately at end of life, firing to drop into the atmosphere over an ocean. Everything else reenters whenever physics decides — which is why tracking agencies and hobbyists watch decaying objects closely.
Why it matters now. With thousands of new satellites launched in recent years, the rate of reentry has climbed with it. The public catalogue records every object whose orbit is collapsing, and that is exactly the list below — updated from live TLE data.