STEX

STEX is an active satellite operated by United States, launched on 1998-10-03 from Vandenberg SFB, California. With over 28 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 712 km and 727 km with an inclination of 85.0°. It travels at approximately 26,992 km/h (7.50 km/s), completing one full orbit every 99 minutes — that’s roughly 14.52 orbits per day. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~25–100 years. Orbital Radar tracks STEX in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

STEX orbits at an average altitude of 720 km in the mid-LEO band, where atmospheric drag is minimal but radiation exposure remains manageable. Objects at this altitude persist for decades to centuries, making debris mitigation critical. This regime is popular for remote sensing constellations and scientific instruments that need stable, long-duration orbits. Within ±50 km of STEX’s average altitude, there are currently 283 active payloads and 1,684 tracked debris or rocket body fragments — notable neighbours include TERRA, AQUA, LANDSAT 9. With an inclination of 85.0°, STEX passes over latitudes between 85.0°N and 85.0°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 12,339 active satellites in total, of which 76 share a similar altitude band with STEX.