SCOUT X-4 R/B

SCOUT X-4 R/B is a spent rocket body associated with United States, launched on 1964-11-21 from Vandenberg Space Force Base, United States on the AD-B launch. After more than 62 years in orbit, it is one of the longest-surviving objects in the space catalogue. It orbits in Medium Earth Orbit (MEO) at altitudes between 522 km and 2,139 km with an inclination of 81.3°. It travels at approximately 25,899 km/h (7.19 km/s), completing one full orbit every 112 minutes — that’s roughly 12.83 orbits per day. Its orbital eccentricity of 0.1050 gives it a noticeably elliptical path, with significant altitude variation between perigee and apogee. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is thousands of 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 1,331 km in Medium Earth Orbit, the region between LEO and GEO (2,000–35,786 km). MEO’s higher altitude gives each satellite a much larger ground footprint than LEO, meaning fewer spacecraft are needed for global coverage — but signal latency is higher and radiation from the Van Allen belts is a significant design constraint. Within ±50 km of SCOUT X-4 R/B’s average altitude, there are currently 20 active payloads and 254 tracked debris or rocket body fragments. This is a relatively sparse altitude band, containing less than 1% of all active satellites. With an inclination of 81.3°, SCOUT X-4 R/B passes over latitudes between 81.3°N and 81.3°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 8 share a similar altitude band with SCOUT X-4 R/B.