OSCAR 15 (UOSAT 4)

OSCAR 15 (UOSAT 4) is an active satellite operated by United Kingdom, launched on 1990-01-22 from Guiana Space Centre, Kourou. With over 36 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 779 km and 793 km with an inclination of 98.8°. It travels at approximately 26,866 km/h (7.46 km/s), completing one full orbit every 101 minutes — that’s roughly 14.32 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 ~25–100 years. Orbital Radar tracks OSCAR 15 (UOSAT 4) in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

OSCAR 15 (UOSAT 4) orbits at an average altitude of 786 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 OSCAR 15 (UOSAT 4)’s average altitude, there are currently 418 active payloads and 2,232 tracked debris or rocket body fragments — notable neighbours include NOAA 20, ONEWEB-0179, ONEWEB-0455. With an inclination of 98.8°, OSCAR 15 (UOSAT 4) passes over latitudes between 98.8°N and 98.8°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 Kingdom operates approximately 720 active satellites in total, of which 6 share a similar altitude band with OSCAR 15 (UOSAT 4).