ESSA 1 (OT-3)

ESSA 1 (OT-3) is an active satellite operated by ESSA (United States), launched on 1966-02-03 from Cape Canaveral Space Force Station, United States on the Tiros OT3 launch. After more than 60 years in orbit, it is one of the longest-surviving objects in the space catalogue. It orbits in Low Earth Orbit (LEO) at altitudes between 673 km and 789 km with an inclination of 97.8°. It travels at approximately 26,970 km/h (7.49 km/s), completing one full orbit every 99 minutes — that’s roughly 14.48 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 ESSA 1 (OT-3) in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

ESSA 1 (OT-3) orbits at an average altitude of 731 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 ESSA 1 (OT-3)’s average altitude, there are currently 404 active payloads and 2,017 tracked debris or rocket body fragments — notable neighbours include TERRA, AQUA, ONEWEB-0179. With an inclination of 97.8°, ESSA 1 (OT-3) passes over latitudes between 97.8°N and 97.8°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 13,279 active satellites in total, of which 172 share a similar altitude band with ESSA 1 (OT-3).