DELTA 1 R/B

DELTA 1 R/B is a spent rocket body associated with United States, launched on 1972-12-11 from Vandenberg Space Force Base, United States on the Nimbus E launch. After more than 54 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 1,100 km and 1,515 km with an inclination of 99.8°. It travels at approximately 25,938 km/h (7.20 km/s), completing one full orbit every 112 minutes — that’s roughly 12.89 orbits per day. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is thousands of years. Spent rocket bodies like DELTA 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.

DELTA 1 R/B orbits at an average altitude of 1,308 km in the uppermost reaches of Low Earth Orbit. At this altitude, orbital decay is effectively zero without active deorbiting, and coverage footprints are significantly larger than lower LEO, though at the cost of higher latency. Within ±50 km of DELTA 1 R/B’s average altitude, there are currently 20 active payloads and 381 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 99.8°, DELTA 1 R/B passes over latitudes between 99.8°N and 99.8°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 8 share a similar altitude band with DELTA 1 R/B.