SCOUT X-4 R/B

SCOUT X-4 R/B is a spent rocket body associated with United States, launched on 1965-11-19 from Wallops Flight Facility / MARS, United States on the Solar Explorer A launch. After more than 61 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 654 km and 763 km with an inclination of 59.7°. It travels at approximately 27,013 km/h (7.50 km/s), completing one full orbit every 99 minutes — that’s roughly 14.55 orbits per day. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~25–100 years. Spent rocket bodies like SCOUT X-4 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 X-4 R/B orbits at an average altitude of 709 km in the mid-LEO band, where atmospheric drag is minimal but radiation exposure remains manageable. Objects at this altitude persist for decades to centuries, making debris mitigation critical. This regime is popular for remote sensing constellations and scientific instruments that need stable, long-duration orbits. Within ±50 km of SCOUT X-4 R/B’s average altitude, there are currently 282 active payloads and 1,668 tracked debris or rocket body fragments — notable neighbours include TERRA, AQUA, ONEWEB-0179. With an inclination of 59.7°, SCOUT X-4 R/B passes over latitudes between 59.7°N and 59.7°S, covering most populated land masses in both hemispheres. This mid-inclination band balances global coverage with efficient launch energy requirements. United States operates approximately 13,206 active satellites in total, of which 86 share a similar altitude band with SCOUT X-4 R/B.