ZK-1A R/B

ZK-1A R/B is a spent rocket body associated with China, launched on 2025-05-21 from Jiuquan, China on the Taijing 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 351 km and 440 km with an inclination of 97.4°. It travels at approximately 27,631 km/h (7.68 km/s), completing one full orbit every 92 minutes — that’s roughly 15.57 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 months to ~1 year. Spent rocket bodies like ZK-1A 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.

ZK-1A R/B orbits at an average altitude of 396 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 ZK-1A R/B’s average altitude, there are currently 1,286 active payloads and 88 tracked debris or rocket body fragments — notable neighbours include STARLINK-1008, STARLINK-1012, STARLINK-1020. This makes it one of the more crowded altitude bands, containing roughly 7.4% of all active satellites. With an inclination of 97.4°, ZK-1A R/B passes over latitudes between 97.4°N and 97.4°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. China operates approximately 1,221 active satellites in total, of which 41 share a similar altitude band with ZK-1A R/B.