Glossary / Space
Geostationary orbit
A circular orbit about 36,000 km above the equator. It matches Earth's rotation, so a satellite there appears fixed in the sky.
In 1945, before he was known as a science-fiction writer, Arthur C. Clarke proposed in a radio magazine that three satellites at this altitude could relay radio signals over almost the whole planet[1].
Syncom 3 made it real in 1964, relaying the Tokyo Olympics across the Pacific. Communications, broadcasting and weather satellites still line this orbit, and slots are allocated internationally.
Related terms
- Kepler's lawsThree laws of planetary motion: planets move on ellipses with the Sun at one focus, sweep faster when closer to it, and have orbital periods tied to orbit size.
- Kessler syndromeThe prediction that as satellites and fragments multiply in orbit, debris from one collision will trigger more, possibly making the orbit unusable.
On the timeline
Sources
- A. C. Clarke, “Extra-Terrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage?,” Wireless World 51(10), 305–308 (1945).