EXPLORER 40 (INJUN-5)

EXPLORER 40 (INJUN-5) is an active satellite operated by NASA LaRC (United States), launched on 1968-08-08 from Vandenberg Space Force Base, United States on the AD-C launch. After more than 58 years in orbit, it is one of the longest-surviving objects in the space catalogue. It orbits in Medium Earth Orbit (MEO) at altitudes between 679 km and 2,475 km with an inclination of 80.7°. It travels at approximately 25,494 km/h (7.08 km/s), completing one full orbit every 118 minutes — that’s roughly 12.24 orbits per day. Its orbital eccentricity of 0.1130 gives it a noticeably elliptical path, with significant altitude variation between perigee and apogee. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is thousands of years. Orbital Radar tracks EXPLORER 40 (INJUN-5) in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

EXPLORER 40 (INJUN-5) orbits at an average altitude of 1,577 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 EXPLORER 40 (INJUN-5)’s average altitude, there are currently 37 active payloads and 317 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 80.7°, EXPLORER 40 (INJUN-5) passes over latitudes between 80.7°N and 80.7°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 13,279 active satellites in total, of which 2 share a similar altitude band with EXPLORER 40 (INJUN-5).