USA 55

USA 55 is an active satellite operated by DARPA / USN (United States), launched on 1990-04-05 from Vandenberg Space Force Base, United States on the Pegsat launch. With over 36 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 395 km and 465 km with an inclination of 94.1°. It travels at approximately 27,560 km/h (7.66 km/s), completing one full orbit every 93 minutes — that’s roughly 15.45 orbits per day. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~1–3 years. Orbital Radar tracks USA 55 in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

USA 55 orbits at an average altitude of 430 km in the core of Low Earth Orbit, the most heavily utilised altitude band. The balance of moderate drag (limiting debris accumulation) and short signal path (enabling low-latency links and high-resolution imaging) makes this regime the default for most commercial and government missions. Within ±50 km of USA 55’s average altitude, there are currently 7,127 active payloads and 122 tracked debris or rocket body fragments — notable neighbours include ISS (ZARYA), STARLINK-1017, STARLINK-1039. This makes it one of the more crowded altitude bands, containing roughly 37.6% of all active satellites. With an inclination of 94.1°, USA 55 passes over latitudes between 94.1°N and 94.1°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 13,340 active satellites in total, of which 6,882 share a similar altitude band with USA 55.