MDS 1

MDS 1 is an active satellite operated by Japan, launched on 2002-02-04 from TNSTA. With over 24 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Medium Earth Orbit (MEO) at altitudes between 275 km and 9,677 km with an inclination of 28.5°. It travels at approximately 21,337 km/h (5.93 km/s), completing one full orbit every 3 hours 21 minutes — that’s roughly 7.18 orbits per day. Its orbital eccentricity of 0.4143 gives it a noticeably elliptical path, with significant altitude variation between perigee and apogee. Orbital Radar tracks MDS 1 in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

MDS 1 orbits at an average altitude of 4,976 km in Medium Earth Orbit, the region between LEO and GEO (2,000–35,786 km). MEO’s higher altitude gives each satellite a much larger ground footprint than LEO, meaning fewer spacecraft are needed for global coverage — but signal latency is higher and radiation from the Van Allen belts is a significant design constraint. Within ±50 km of MDS 1’s average altitude, there are currently 1 active payload and 5 tracked debris or rocket body fragments. This is a relatively sparse altitude band, containing less than 1% of all active satellites. With an inclination of 28.5°, MDS 1 passes over latitudes between 28.5°N and 28.5°S, covering the tropical and temperate zones where most of the world’s population resides. Low-to-mid inclination orbits are efficient to reach from equatorial and mid-latitude launch sites. Japan operates approximately 189 active satellites in total.