DUPLEX

DUPLEX is an active satellite operated by United States, launched on 1998-11-20 from Baikonur, Kazakhstan on the 77KM No. 17501 launch. With over 28 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 377 km and 380 km with an inclination of 51.6°. It travels at approximately 27,665 km/h (7.68 km/s), completing one full orbit every 92 minutes — that’s roughly 15.63 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 months to ~1 year. Orbital Radar tracks DUPLEX in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

DUPLEX orbits at an average altitude of 379 km in the lower reaches of Low Earth Orbit, where atmospheric drag is significant and orbital lifetimes are measured in months to a few years. This is the busiest corridor in space — home to crewed spacecraft, rapid-revisit imaging satellites and the densest part of the Starlink constellation. Within ±50 km of DUPLEX’s average altitude, there are currently 1,285 active payloads and 61 tracked debris or rocket body fragments — notable neighbours include STARLINK-1008, STARLINK-1012, STARLINK-1020. This makes it one of the more crowded altitude bands, containing roughly 7.3% of all active satellites. With an inclination of 51.6°, DUPLEX passes over latitudes between 51.6°N and 51.6°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 12,413 active satellites in total, of which 1,146 share a similar altitude band with DUPLEX.