MOS 1B (MOMO 1B)

MOS 1B (MOMO 1B) is an active satellite operated by Japan, launched on 1990-02-07 from TNSTA. With over 36 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 903 km and 912 km with an inclination of 99.2°. It travels at approximately 26,641 km/h (7.40 km/s), completing one full orbit every 103 minutes — that’s roughly 13.96 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 ~100–500 years. Orbital Radar tracks MOS 1B (MOMO 1B) in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

MOS 1B (MOMO 1B) orbits at an average altitude of 908 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 MOS 1B (MOMO 1B)’s average altitude, there are currently 214 active payloads and 1,250 tracked debris or rocket body fragments. With an inclination of 99.2°, MOS 1B (MOMO 1B) passes over latitudes between 99.2°N and 99.2°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. Japan operates approximately 189 active satellites in total, of which 2 share a similar altitude band with MOS 1B (MOMO 1B).