Geostationary orbit
Published 19 October 2026 · All guides
In short: 35,786 km above the equator, a satellite goes round once for every turn of the Earth, so from the ground it seems to hang in one place. That makes it ideal for communications, weather pictures of a whole hemisphere and listening posts. It is too far away for detailed imaging, it cannot see the poles well, and keeping a satellite in its slot costs propellant every year.
Why that height
Higher orbits are slower (see orbital mechanics without the maths). At 35,786 km above the equator the period is 23 hours 56 minutes, exactly one rotation of the Earth relative to the stars. A satellite there moving eastward over the equator keeps pace with the ground beneath it. A satellite at the same height on a tilted orbit is merely geosynchronous: it traces a figure of eight in the sky each day instead of standing still.
The idea was popularised by Arthur C. Clarke in a 1945 article in Wireless World, proposing three relay stations to cover the world. Syncom 3, the first geostationary satellite, was launched in 1964 and relayed television of that year's Tokyo Olympics to the United States.
What it is for
- Communications and television. A dish on a roof can point at one spot and never move.
- Weather. Satellites such as the US GOES series and Europe's Meteosat watch the same disc of the Earth continuously, which is how forecasters follow a storm as it grows.
- Missile warning. Infrared satellites watch for the hot plume of a launch across a whole hemisphere.
- Listening. Large signals-intelligence satellites sit here to eavesdrop on a whole continent at once (see how spy satellites work).
Why it is no place for sharp pictures
Detail falls with distance. A Hubble-sized 2.4 m mirror that would resolve about 6 cm from 250 km resolves about 9 m from geostationary orbit. You can watch a weather system or a city's lights, but not read what is parked outside a building.
The other costs
- The poles are out of sight. From that height the Earth's edge is at about 81 degrees of latitude, and anything near the edge is seen at a grazing angle.
- Delay. A radio signal takes about a quarter of a second to go up and come back down, which is noticeable on a phone call.
- Upkeep. The pull of the Sun and Moon slowly tilts a geostationary orbit, and correcting it costs around 50 m/s of propellant a year. When the tank runs low, the satellite is raised a few hundred kilometres into a graveyard orbit to free its slot.
Neighbours watching neighbours
Because geostationary satellites are valuable and sit in fixed slots, they are watched. The US revealed its GSSAP inspection satellites, which drift along the belt photographing other spacecraft, in 2014. From 2015 Russia's Luch (Olymp-K) satellite drew public concern by parking close to commercial communications satellites, including several of Intelsat's.
Where Celestrike comes in
In Celestrike the NULLPOINT is the satellite that goes to geostationary height. It stares at one region continuously instead of passing over, and can be parked over almost anywhere on the globe, which the real physics would not allow cheaply, at a propellant cost the game shows before you commit. Celestrike is a free spy-satellite strategy game for iPhone and Android, played on real orbits — on the App Store and Google Play.