SL-16 R/B

SL-16 R/B is a spent rocket body associated with Russia (CIS), launched on 1999-07-17 from Baikonur, Kazakhstan on the Okean-O No. 1 launch. With over 27 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 614 km and 633 km with an inclination of 98.0°. It travels at approximately 27,176 km/h (7.55 km/s), completing one full orbit every 97 minutes — that’s roughly 14.82 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. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~10–25 years. Spent rocket bodies like SL-16 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-16 R/B orbits at an average altitude of 624 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-16 R/B’s average altitude, there are currently 840 active payloads and 795 tracked debris or rocket body fragments — notable neighbours include ONEWEB-0050, STARLINK-3055, STARLINK-3109. With an inclination of 98.0°, SL-16 R/B passes over latitudes between 98.0°N and 98.0°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 1,286 active satellites in total, of which 22 share a similar altitude band with SL-16 R/B.