According to a fact sheet compiled by the International Telecommunications Union (ITU), over 500 satellites orbit the earth delivering broadcasting; voice, Internet and emergency communications; environmental and scientific monitoring; and global navigation and positioning systems for planes, ships and vehicles.
Most communication satellites are launched into an orbit 35,786km above the equator (Geostationary orbit, or GEO) and rotate with the earth, appearing motionless to an observer on the ground.
Medium earth orbit (MEO) satellite systems, positioned at altitudes ranging from 8,000 to 15,000km above the earth, require a larger constellation of spacecraft – typically 10 – 15
satellites – to maintain coverage of the earth.
Low Earth Orbit (LEO) satellites occupy orbits starting from a few hundreds of kilometres above earth to around 1,000km. LEO constellations need even larger numbers of satellites to provide constant earth coverage.
Space debris is a growing problem. Disused satellites, discarded launch systems and fragments caused by collisions are putting satellites at risk. At orbital speed, a
fragment measuring less than 1cm can knock out a satellite costing millions of dollars.
It takes about two years to build a satellite and costs hundreds of millions of dollars to build, launch and operate it. GEO satellites have a life span of about 15 years. Satellites transmit trillions of bits of data per second.
International cooperation and coordination is essential to ensure interference-free operation of satellites and their coexistence with ground-based services sharing the same radio frequency bands.
The ITU is the UN agency charged with the global management of spectrum and associated satellite orbits, including GEO slots, helping bring modern communications to communities worldwide.