TOPO 1

TOPO 1 is an active satellite operated by USA ETL (United States), launched on 1970-04-08 from Vandenberg Space Force Base, United States on the Nimbus D launch. After more than 56 years in orbit, it is one of the longest-surviving objects in the space catalogue. It orbits in Low Earth Orbit (LEO) at altitudes between 1,082 km and 1,086 km with an inclination of 99.9°. It travels at approximately 26,324 km/h (7.31 km/s), completing one full orbit every 107 minutes — that’s roughly 13.47 orbits per day. Its near-circular orbit (eccentricity close to zero) means it maintains a very consistent altitude throughout each revolution. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~500–1,000 years. Orbital Radar tracks TOPO 1 in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

TOPO 1 orbits at an average altitude of 1,084 km in the upper LEO band, where atmospheric drag is negligible and objects can persist for centuries to millennia. This altitude is used by broadband constellations like OneWeb and by scientific missions requiring stable orbits far from the densest debris bands. Within ±50 km of TOPO 1’s average altitude, there are currently 308 active payloads and 544 tracked debris or rocket body fragments — notable neighbours include ONEWEB-0041. With an inclination of 99.9°, TOPO 1 passes over latitudes between 99.9°N and 99.9°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 13,276 active satellites in total, of which 43 share a similar altitude band with TOPO 1.