SL-3 R/B

SL-3 R/B is a spent rocket body associated with Russia (CIS), launched on 1973-03-20 from Plesetsk Cosmodrome, Russia on the Meteor-M No. 29 launch. After more than 53 years in orbit, it is one of the longest-surviving objects in the space catalogue. It orbits in Low Earth Orbit (LEO) at altitudes between 832 km and 918 km with an inclination of 81.3°. It travels at approximately 26,701 km/h (7.42 km/s), completing one full orbit every 102 minutes — that’s roughly 14.05 orbits per day. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~100–500 years. Spent rocket bodies like SL-3 R/B are among the largest pieces of uncontrolled space debris and are priority targets for collision avoidance manoeuvres and future active debris removal efforts.

SL-3 R/B orbits at an average altitude of 875 km in the upper LEO band, where atmospheric drag is negligible and objects can persist for centuries to millennia. This altitude is used by broadband constellations like OneWeb and by scientific missions requiring stable orbits far from the densest debris bands. Within ±50 km of SL-3 R/B’s average altitude, there are currently 234 active payloads and 1,946 tracked debris or rocket body fragments — notable neighbours include NOAA 20. With an inclination of 81.3°, SL-3 R/B passes over latitudes between 81.3°N and 81.3°S, providing near-global coverage including the polar regions. Polar and near-polar orbits are used for reconnaissance, weather monitoring and Earth-observation missions that need to image every part of the planet. Russia (CIS) operates approximately 1,537 active satellites in total, of which 66 share a similar altitude band with SL-3 R/B.