TERRA

TERRA is an active satellite operated by Earth Sciences Enterprise (NASA) (United States), launched on 1999-12-18 from Vandenberg SFB, California. With over 27 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 688 km and 691 km with an inclination of 98.0°. It travels at approximately 27,049 km/h (7.51 km/s), completing one full orbit every 99 minutes — that’s roughly 14.61 orbits per day. Its near-polar, sun-synchronous orbit means it passes over any given point on Earth at approximately the same local solar time, ideal for consistent Earth observation lighting conditions. 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 TERRA in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

TERRA orbits at an average altitude of 690 km in a sun-synchronous orbit (SSO), a specialised subset of LEO where the orbital plane precesses to maintain a constant angle relative to the Sun. This provides consistent lighting conditions on every pass — essential for Earth observation, weather monitoring and environmental science. Within ±50 km of TERRA’s average altitude, there are currently 307 active payloads and 1,350 tracked debris or rocket body fragments — notable neighbours include AQUA, LANDSAT 9. With an inclination of 98.0°, TERRA passes over latitudes between 98.0°N and 98.0°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 12,360 active satellites in total, of which 70 share a similar altitude band with TERRA.