SL-3 R/B

SL-3 R/B is a spent rocket body associated with Russia (CIS), launched on 1977-06-29 from Baikonur, Kazakhstan on the Meteor-Priroda No. 2-2 launch. With over 49 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 419 km and 426 km with an inclination of 97.6°. It travels at approximately 27,576 km/h (7.66 km/s), completing one full orbit every 93 minutes — that’s roughly 15.48 orbits per day. Its near-polar, sun-synchronous orbit means it passes over any given point on Earth at approximately the same local solar time, ideal for consistent Earth observation lighting conditions. 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 ~1–3 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 423 km in a sun-synchronous orbit (SSO), a specialised subset of LEO where the orbital plane precesses to maintain a constant angle relative to the Sun. This provides consistent lighting conditions on every pass — essential for Earth observation, weather monitoring and environmental science. Within ±50 km of SL-3 R/B’s average altitude, there are currently 3,498 active payloads and 133 tracked debris or rocket body fragments — notable neighbours include STARLINK-1008, STARLINK-1012, STARLINK-1017. This makes it one of the more crowded altitude bands, containing roughly 20% of all active satellites. With an inclination of 97.6°, SL-3 R/B passes over latitudes between 97.6°N and 97.6°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 1,287 active satellites in total, of which 43 share a similar altitude band with SL-3 R/B.