Satellites are usually grouped by the altitude of their orbit: low Earth orbit (LEO), medium Earth orbit (MEO) and geostationary orbit (GEO). Each orbit has its own strengths, and the choice decides how many satellites a service needs, how large the ground antennas must be and which launch is required. This guide compares the three orbits and shows what they are used for.
Overview: LEO vs MEO vs GEO
- LEO: according to ESA, below about 2,000 km. Satellites generally do not fly below about 180 km because of atmospheric drag.
- MEO: the wide range between LEO and GEO, usually above the Van Allen radiation belts.
- GEO: 35,786 km above the equator, where a satellite circles the Earth once per sidereal day and appears fixed in the sky.
Low Earth orbit (LEO): uses and examples
LEO is the closest and easiest orbit to reach. It is used for Earth observation, science missions, crewed spaceflight and large broadband constellations. The International Space Station, shown on the cover image, orbits about 260 miles, or roughly 420 km, above the Earth. Sun-synchronous orbits, a special type of LEO popular for Earth observation, usually lie between 600 and 800 km, according to ESA. Because each LEO satellite only sees a small part of the Earth, continuous services need many satellites.
What is MEO and what is it used for?
ESA describes medium Earth orbit as covering a wide range of altitudes between LEO and GEO. MEO is very commonly used for satellite navigation, but also for communications:
- Galileo: Europe's navigation satellites fly in MEO at an altitude of 23,222 km, according to ESA.
- GPS: the US navigation satellites fly in MEO at approximately 20,200 km and circle the Earth twice a day, according to the US government's GPS website.
- O3b mPOWER: SES operates this communications system in MEO about 8,000 km above the Earth.
MEO offers a middle ground: each satellite covers a much larger area than in LEO, so fewer satellites are needed, while the distance to the ground is still much shorter than in GEO.
Geostationary orbit (GEO): uses and examples
At 35,786 km, a GEO satellite travels at about 3 km per second and keeps pace with the Earth's rotation. According to ESA, this makes GEO ideal for telecommunication satellites, because antennas on the ground can stay pointed at one fixed position. Weather satellites also use GEO to observe the same region continuously. The drawbacks are the high launch energy required and the long signal path.
LEO vs GEO: which orbit is better?
There is no single best orbit. LEO suits missions that need detailed images, low latency or low launch costs per satellite, but it requires many satellites for continuous coverage. GEO suits broadcasting and regional services with a small number of large satellites. MEO sits between the two and is the standard choice for global navigation.
What this means for launch planning
- LEO satellites can often fly on rideshare missions.
- MEO constellations usually need dedicated launches to reach their planes.
- GEO satellites are typically released into a geostationary transfer orbit and raise their orbit themselves. Read more in our guide to the geostationary transfer orbit.
Sources
- ESA: Types of orbits
- ESA: Galileo, a constellation of navigation satellites
- GPS.gov: Space Segment
- SES: SES's O3b mPOWER System Starts Providing High-performance Connectivity Services
Cover image: A roll-out solar array held by the Canadarm2 robotic arm on the International Space Station, which orbits in LEO, June 2021. Credit: NASA (iss065e116519), public domain.