SL-4 R/B

SL-4 R/B is a spent rocket body associated with Russia (CIS), launched on 2026-09-16 from Baikonur Cosmodrome, Kazakhstan on the Progress 7K-TGM No. 465 launch. As a relatively recent addition to the catalogue, its orbital elements are well-characterised. It orbits in Low Earth Orbit (LEO) at altitudes between 171 km and 194 km with an inclination of 51.7°. It travels at approximately 28,076 km/h (7.80 km/s), completing one full orbit every 88 minutes — that’s roughly 16.34 orbits per day. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is days to weeks — very low orbit, rapid decay. Spent rocket bodies like SL-4 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-4 R/B orbits at an average altitude of 183 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-4 R/B’s average altitude, there are currently 17 active payloads and 2 tracked debris or rocket body fragments — notable neighbours include STARLINK-1319, STARLINK-1724, STARLINK-1942. This is a relatively sparse altitude band, containing less than 1% of all active satellites. With an inclination of 51.7°, SL-4 R/B passes over latitudes between 51.7°N and 51.7°S, covering most populated land masses in both hemispheres. This mid-inclination band balances global coverage with efficient launch energy requirements. Russia (CIS) operates approximately 1,536 active satellites in total.