SKYNET 4A R/B(PAM-D2)

SKYNET 4A R/B(PAM-D2) is a spent rocket body associated with United States, launched on 1990-01-01 from Cape Canaveral, Florida on the Skynet 4A launch. With over 36 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Medium Earth Orbit (MEO) at altitudes between 344 km and 31,987 km with an inclination of 21.5°. It travels at approximately 15,140 km/h (4.21 km/s), completing one full orbit every 9 hours 21 minutes — that’s roughly 2.56 orbits per day. Its orbital eccentricity of 0.7020 gives it a noticeably elliptical path, with significant altitude variation between perigee and apogee. Spent rocket bodies like SKYNET 4A R/B(PAM-D2) are among the largest pieces of uncontrolled space debris and are priority targets for collision avoidance manoeuvres and future active debris removal efforts.

SKYNET 4A R/B(PAM-D2) orbits at an average altitude of 16,166 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 SKYNET 4A R/B(PAM-D2)’s average altitude, there are currently 1 active payload and 7 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 21.5°, SKYNET 4A R/B(PAM-D2) passes over latitudes between 21.5°N and 21.5°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.