SL-6 R/B(2)

SL-6 R/B(2) is a spent rocket body associated with Russia (CIS), launched on 1978-09-06 from PKMTR on the Oko launch. With over 48 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Medium Earth Orbit (MEO) at altitudes between 2,380 km and 38,240 km with an inclination of 65.8°. It travels at approximately 13,915 km/h (3.87 km/s), completing one full orbit every 12 hours 3 minutes — that’s roughly 1.99 orbits per day. Its orbital eccentricity of 0.6720 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 20,310 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 2 active payloads and 12 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 65.8°, SL-6 R/B(2) passes over latitudes between 65.8°N and 65.8°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 1,287 active satellites in total, of which 2 share a similar altitude band with SL-6 R/B(2).