SCOUT D-1 R/B

SCOUT D-1 R/B is a spent rocket body associated with United States, launched on 1974-03-09 from Vandenberg Space Force Base, United States on the X-4 launch. After more than 52 years in orbit, it is one of the longest-surviving objects in the space catalogue. It orbits in Low Earth Orbit (LEO) at altitudes between 668 km and 817 km with an inclination of 97.8°. It travels at approximately 26,948 km/h (7.49 km/s), completing one full orbit every 100 minutes — that’s roughly 14.45 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 ~25–100 years. Spent rocket bodies like SCOUT D-1 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.

SCOUT D-1 R/B orbits at an average altitude of 743 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 SCOUT D-1 R/B’s average altitude, there are currently 414 active payloads and 2,033 tracked debris or rocket body fragments — notable neighbours include ONEWEB-0179, LANDSAT 9. With an inclination of 97.8°, SCOUT D-1 R/B passes over latitudes between 97.8°N and 97.8°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. United States operates approximately 13,206 active satellites in total, of which 173 share a similar altitude band with SCOUT D-1 R/B.