TOPSAT

TOPSAT is an active satellite operated by United Kingdom, launched on 2005-10-27 from PKMTR. With over 21 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 668 km and 689 km with an inclination of 98.3°. It travels at approximately 27,070 km/h (7.52 km/s), completing one full orbit every 98 minutes — that’s roughly 14.65 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. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~10–25 years. Orbital Radar tracks TOPSAT in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

TOPSAT orbits at an average altitude of 679 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 TOPSAT’s average altitude, there are currently 518 active payloads and 1,268 tracked debris or rocket body fragments — notable neighbours include TERRA, AQUA, LANDSAT 9. With an inclination of 98.3°, TOPSAT passes over latitudes between 98.3°N and 98.3°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 Kingdom operates approximately 720 active satellites in total, of which 3 share a similar altitude band with TOPSAT.