NAVSTAR 55 (USA 178)

NAVSTAR 55 (USA 178) is an active satellite operated by U.S. Space Force (United States), launched on 2004-06-23 from Cape Canaveral, Florida. With over 22 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Medium Earth Orbit (MEO) at altitudes between 19,758 km and 20,607 km with an inclination of 54.9°. It travels at approximately 13,948 km/h (3.87 km/s), completing one full orbit every 11 hours 58 minutes — that’s roughly 2.01 orbits per day. It is part of the Gps Ops constellation group. Orbital Radar tracks NAVSTAR 55 (USA 178) in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

NAVSTAR 55 (USA 178) orbits at an average altitude of 20,183 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 NAVSTAR 55 (USA 178)’s average altitude, there are currently 103 active payloads and 13 tracked debris or rocket body fragments — notable neighbours include GPS BIIR-5 (PRN 22), GPS BIIR-8 (PRN 16), GPS BIIR-11 (PRN 19). With an inclination of 54.9°, NAVSTAR 55 (USA 178) passes over latitudes between 54.9°N and 54.9°S, covering most populated land masses in both hemispheres. This mid-inclination band balances global coverage with efficient launch energy requirements. United States operates approximately 12,360 active satellites in total, of which 43 share a similar altitude band with NAVSTAR 55 (USA 178).