EXPLORER 27

EXPLORER 27 is an active satellite operated by GSFC (United States), launched on 1965-04-29 from Wallops Flight Facility / MARS, United States on the Beacon Explorer C launch. After more than 61 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 933 km and 1,294 km with an inclination of 41.2°. It travels at approximately 26,272 km/h (7.30 km/s), completing one full orbit every 108 minutes — that’s roughly 13.39 orbits per day. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~500–1,000 years. Orbital Radar tracks EXPLORER 27 in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

EXPLORER 27 orbits at an average altitude of 1,114 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 EXPLORER 27’s average altitude, there are currently 434 active payloads and 476 tracked debris or rocket body fragments — notable neighbours include ONEWEB-0041, ONEWEB-0250. With an inclination of 41.2°, EXPLORER 27 passes over latitudes between 41.2°N and 41.2°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 13,276 active satellites in total, of which 37 share a similar altitude band with EXPLORER 27.