GP-B

GP-B is an active satellite operated by United States, launched on 2004-04-20 from Vandenberg SFB, California. With over 22 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 618 km and 620 km with an inclination of 89.8°. It travels at approximately 27,185 km/h (7.55 km/s), completing one full orbit every 97 minutes — that’s roughly 14.83 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 ~10–25 years. Orbital Radar tracks GP-B in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

GP-B orbits at an average altitude of 619 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 GP-B’s average altitude, there are currently 1,548 active payloads and 761 tracked debris or rocket body fragments — notable neighbours include ONEWEB-0050, STARLINK-3090, STARLINK-3077. This makes it one of the more crowded altitude bands, containing roughly 8.9% of all active satellites. With an inclination of 89.8°, GP-B passes over latitudes between 89.8°N and 89.8°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 1,060 share a similar altitude band with GP-B.