SL-3 R/B

SL-3 R/B is a spent rocket body associated with Russia (CIS), launched on 1971-04-07 from Plesetsk Cosmodrome, Russia on the Tselina-D launch. After more than 55 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 326 km and 337 km with an inclination of 81.2°. It travels at approximately 27,762 km/h (7.71 km/s), completing one full orbit every 91 minutes — that’s roughly 15.80 orbits per day. Its near-circular orbit (eccentricity close to zero) means it maintains a very consistent altitude throughout each revolution. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is months to ~1 year. 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 332 km in the lower reaches of Low Earth Orbit, where atmospheric drag is significant and orbital lifetimes are measured in months to a few years. This is the busiest corridor in space — home to crewed spacecraft, rapid-revisit imaging satellites and the densest part of the Starlink constellation. Within ±50 km of SL-3 R/B’s average altitude, there are currently 1,143 active payloads and 38 tracked debris or rocket body fragments — notable neighbours include STARLINK-1008, STARLINK-1012, STARLINK-1020. This makes it one of the more crowded altitude bands, containing roughly 6.1% of all active satellites. With an inclination of 81.2°, SL-3 R/B passes over latitudes between 81.2°N and 81.2°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 23 share a similar altitude band with SL-3 R/B.