SSTL S1-4

SSTL S1-4 is an active satellite operated by Surrey Satellite Technology Ltd. (United Kingdom), launched on 2018-09-16 from Satish Dhawan Space Centre, India on the PSLV Rideshare 12 launch. It orbits in Low Earth Orbit (LEO) at altitudes between 560 km and 577 km with an inclination of 97.5°. It travels at approximately 27,284 km/h (7.58 km/s), completing one full orbit every 96 minutes — that’s roughly 14.99 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 ~3–10 years. Orbital Radar tracks SSTL S1-4 in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

SSTL S1-4 orbits at an average altitude of 569 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 SSTL S1-4’s average altitude, there are currently 1,094 active payloads and 529 tracked debris or rocket body fragments — notable neighbours include ONEWEB-0050, STARLINK-3005, STARLINK-3055. This makes it one of the more crowded altitude bands, containing roughly 5.8% of all active satellites. With an inclination of 97.5°, SSTL S1-4 passes over latitudes between 97.5°N and 97.5°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 725 active satellites in total, of which 20 share a similar altitude band with SSTL S1-4.