SL-6 R/B(2)

SL-6 R/B(2) is a spent rocket body associated with Russia (CIS), launched on 1977-07-20 from PKMTR on the Oko launch. With over 49 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Medium Earth Orbit (MEO) at altitudes between 572 km and 39,923 km with an inclination of 61.8°. It travels at approximately 13,931 km/h (3.87 km/s), completing one full orbit every 12 hours 1 minutes — that’s roughly 2.00 orbits per day. Its orbital eccentricity of 0.7392 gives it a noticeably elliptical path, with significant altitude variation between perigee and apogee. Spent rocket bodies like SL-6 R/B(2) are among the largest pieces of uncontrolled space debris and are priority targets for collision avoidance manoeuvres and future active debris removal efforts.

SL-6 R/B(2) orbits at an average altitude of 20,248 km in Medium Earth Orbit, the region between LEO and GEO (2,000–35,786 km). MEO’s higher altitude gives each satellite a much larger ground footprint than LEO, meaning fewer spacecraft are needed for global coverage — but signal latency is higher and radiation from the Van Allen belts is a significant design constraint. Within ±50 km of SL-6 R/B(2)’s average altitude, there are currently 9 active payloads and 19 tracked debris or rocket body fragments. This is a relatively sparse altitude band, containing less than 1% of all active satellites. With an inclination of 61.8°, SL-6 R/B(2) passes over latitudes between 61.8°N and 61.8°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 1,286 active satellites in total, of which 9 share a similar altitude band with SL-6 R/B(2).