HIPPARCOS

HIPPARCOS is an active satellite operated by ESA (European Space Agency), launched on 1989-08-08 from Guiana Space Centre, Kourou. With over 37 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Medium Earth Orbit (MEO) at altitudes between 508 km and 35,732 km with an inclination of 7.4°. It travels at approximately 14,523 km/h (4.03 km/s), completing one full orbit every 10 hours 36 minutes — that’s roughly 2.26 orbits per day. Its orbital eccentricity of 0.7191 gives it a noticeably elliptical path, with significant altitude variation between perigee and apogee. It is part of the Geo Protected Plus constellation group. Orbital Radar tracks HIPPARCOS in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

HIPPARCOS operates in Medium Earth Orbit (MEO), the region between LEO and GEO spanning roughly 2,000 to 35,786 km altitude. MEO is home to navigation constellations (GPS at ~20,200 km, Galileo at ~23,222 km, GLONASS at ~19,130 km) and some communications systems. The higher altitude gives each satellite a much larger ground footprint than LEO, meaning fewer satellites are needed for global coverage, but signal latency is higher and radiation exposure — particularly from the Van Allen belts — is a significant design challenge.