DELTA 1 R/B(1)

DELTA 1 R/B(1) is a spent rocket body associated with United States, launched on 1977-08-25 from Cape Canaveral, Florida on the Sirio 1 launch. With over 49 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Medium Earth Orbit (MEO) at altitudes between 871 km and 2,074 km with an inclination of 27.1°. It travels at approximately 25,664 km/h (7.13 km/s), completing one full orbit every 115 minutes — that’s roughly 12.48 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(1) 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(1) orbits at an average altitude of 1,473 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 DELTA 1 R/B(1)’s average altitude, there are currently 314 active payloads and 249 tracked debris or rocket body fragments. With an inclination of 27.1°, DELTA 1 R/B(1) passes over latitudes between 27.1°N and 27.1°S, covering the tropical and temperate zones where most of the world’s population resides. Low-to-mid inclination orbits are efficient to reach from equatorial and mid-latitude launch sites. United States operates approximately 12,413 active satellites in total.