A geostationary orbit is a circular orbit about 35,786 kilometers above the equator, where a satellite circles Earth once per sidereal day and so appears to hang over one spot on the ground.
Geosynchronous orbit is the broader family. It covers any orbit with that same period, including tilted or elliptical ones, where the satellite traces a path across the sky each day. Geostationary is the equatorial, zero-tilt member of that family.
The figures on this page come from the European Space Agency, NASA, and simple arithmetic on their published numbers.
Geostationary Orbit Defined
A geostationary orbit (GEO) is a circular orbit 35,786 kilometers above the equator in which a satellite completes one orbit in 23 hours 56 minutes and 4 seconds. The European Space Agency (ESA) gives both figures and notes that this period equals one sidereal day. Since the satellite and the ground beneath it turn at the same rate, the satellite appears fixed over one spot.
Geosynchronous orbit uses the same period without requiring the orbit to be circular or to sit over the equator. NASA (National Aeronautics and Space Administration) defines a geosynchronous orbit as a prograde, low-inclination orbit about Earth with a period of 23 hours 56 minutes 4 seconds. NASA’s Earthdata orbit guide adds that a geosynchronous orbit directly over the equator is a geostationary orbit.
Terminology varies between sources. Some agencies say “geosynchronous” loosely when they mean geostationary. In strict usage, geosynchronous names the whole category, and geostationary names the subset with zero inclination and zero eccentricity.
Why the Altitude Is 35,786 Kilometers
The altitude of 35,786 kilometers is the height at which one orbit takes exactly one sidereal day. Orbital period depends on height, and ESA’s numbers show the spread. A low Earth orbit (LEO) below 2,000 kilometers takes about 90 minutes. GEO, at 35,786 kilometers, takes 23 hours 56 minutes and 4 seconds.
To match Earth’s rotation, a satellite has to sit far enough out that its period stretches to that full sidereal day. That is why the orbit is so high compared with the space station and imaging satellites in LEO.
The published numbers check out with simple arithmetic:
- NASA’s catalog of satellite orbits gives a geostationary radius of about 42,164 kilometers from Earth’s center.
- The circumference of that circle is 2 × π × 42,164 km, or about 264,900 kilometers.
- One sidereal day is 86,164 seconds (23 × 3,600 + 56 × 60 + 4).
- Dividing 264,900 kilometers by 86,164 seconds gives about 3.07 kilometers per second.
That result matches ESA’s stated GEO speed of about 3 kilometers per second.
Why the Orbit Sits over the Equator
A geostationary satellite has to fly above the equator to appear fixed over one spot. ESA states that GEO satellites fly above the equator and travel west to east, the same direction Earth turns, at about 3 kilometers per second.
Tilt the orbit and the period can stay at one sidereal day, but the satellite stops holding one spot. It traces a path across the sky instead. That tilted orbit is geosynchronous but not geostationary.
An elliptical orbit with the same period also lets the satellite trace a path instead of holding one spot. Only the circular, zero-inclination case holds still relative to the ground.
How Geosynchronous Orbits Differ from Geostationary Ones
Geosynchronous and geostationary orbits share the same period and differ in shape and tilt. The table sets out the differences using the NASA and ESA definitions above.
| Criterion | Geostationary | Geosynchronous (broader family) |
|---|---|---|
| Orbital period | 23 h 56 min 4 s | 23 h 56 min 4 s |
| Inclination (tilt) | Zero | May be tilted (NASA: low-inclination) |
| Shape | Circular (zero eccentricity) | May be elliptical |
| Position | Directly over the equator | Not required to be over the equator |
| View from the ground | Appears fixed over one spot | Traces a path |
Every geostationary orbit is geosynchronous. A geosynchronous orbit counts as geostationary only when both inclination and eccentricity are zero. Some agencies use “geosynchronous” loosely when they mean geostationary.
How Geostationary Orbit Compares with LEO and MEO
Geostationary orbit is higher and slower than low Earth orbit. Medium Earth orbit (MEO) sits between LEO and GEO, usually above the Van Allen radiation belts, according to ESA. ESA’s orbit page gives no numeric altitude range for MEO, so the table says “not stated” rather than guessing.
| Criterion | LEO | MEO | GEO |
|---|---|---|---|
| Altitude | About 180 to 2,000 km | Between LEO and GEO (ESA gives no range) | 35,786 km |
| Orbital period | About 90 minutes | Not stated by ESA | 23 h 56 min 4 s |
| Speed | About 7.8 km/s | Not stated by ESA | About 3 km/s |
| One-way signal trip | Shorter than GEO (the distance is smaller) | Shorter than GEO | About 0.12 s |
| Uses ESA lists | Earth imaging, the space station, communications and navigation constellations | Navigation, such as Galileo | Telecommunications, weather, data relay |
The LEO lower limit of about 180 kilometers exists because of atmospheric effects. A 90-minute orbit cannot match a sidereal day, so a LEO satellite moves relative to the ground. Our LEO satellites explainer covers that orbit in depth, and satellite constellations explained covers how operators group satellites. Our explainer on how GPS works covers satellite navigation.
What Geostationary Orbit Is Used For
Geostationary orbit serves jobs that need a satellite to stay over one place. ESA’s page names these uses:
- Telecommunications. Our guides to satellite communications and the fixed satellite service cover how that works in practice.
- Weather monitoring. A weather satellite in GEO can watch one region continuously. The joint NASA/NOAA GOES weather satellites fly in geostationary orbits above the equator, per NASA Earthdata.
- Data relay. ESA’s EDRS constellation of GEO satellites relays data for spacecraft in lower orbits.
On coverage, ESA states that three evenly spaced GEO satellites can provide near-global coverage.
The cost is signal delay. Radio travels at 299,792 kilometers per second, so one trip from the ground to a GEO satellite takes 35,786 ÷ 299,792, or about 0.12 second. A ground-to-satellite-to-ground hop takes about 0.24 second before any processing.
Limits of a Geostationary Satellite
A geostationary satellite trades some capabilities for its fixed position. The limits below follow directly from the orbit’s definition and the listed figures:
- It cannot sit over a spot away from the equator. Holding one position requires a zero-inclination orbit over the equator. A satellite on a tilted orbit traces a path instead.
- One satellite cannot cover the whole globe. ESA’s figure for near-global coverage is three evenly spaced satellites.
Galileo-type navigation satellites sit in MEO, Earth imaging in LEO, and telecom and weather satellites that need a fixed view in GEO. For spacecraft hardware, see our explainer on the satellite bus, and for orbits in general, how satellites work. Read our LEO satellites explainer next to see how a 90-minute orbit changes coverage and signal delay compared with geostationary orbit.