DELTA 4 R/B

DELTA 4 R/B is a spent rocket body associated with United States, launched on 2004-12-21 from Cape Canaveral, Florida on the HLV-OLDSP launch. With over 22 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Medium Earth Orbit (MEO) at altitudes between 18,889 km and 36,564 km with an inclination of 15.8°. It travels at approximately 12,309 km/h (3.42 km/s), completing one full orbit every 17 hours 25 minutes — that’s roughly 1.38 orbits per day. Its orbital eccentricity of 0.2592 gives it a noticeably elliptical path, with significant altitude variation between perigee and apogee. Spent rocket bodies like DELTA 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.

DELTA 4 R/B orbits at an average altitude of 27,727 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. With an inclination of 15.8°, DELTA 4 R/B passes over latitudes between 15.8°N and 15.8°S, concentrating coverage over equatorial and near-equatorial regions. Low-inclination orbits maximise revisit rates over specific tropical zones. United States operates approximately 12,413 active satellites in total.