The orbit decides almost everything about a satellite mission: which launcher can reach it, how long the satellite takes to circle the Earth and what it can see or connect to. Here is an overview of the orbits that matter most for operators, based on the definitions published by the European Space Agency.
Low Earth orbit (LEO)
Low Earth orbit lies below an altitude of 2,000 km. According to ESA, the practical lower limit is around 180 km. A satellite in LEO travels at about 7.8 km per second and completes one orbit in roughly 90 minutes. LEO is used by Earth observation satellites, communication constellations and the International Space Station. Because it is close to Earth, it is also the cheapest orbit to reach.
Polar orbit
Satellites in a polar orbit travel roughly from one pole to the other. ESA gives a typical altitude range of 200 to 1,000 km. As the Earth rotates underneath, a satellite in polar orbit can observe the whole planet over time.
Sun-synchronous orbit (SSO)
A sun-synchronous orbit is a special polar orbit, typically between 600 and 800 km according to ESA. Its key feature: the satellite passes over the same spot on Earth at the same local time every day. This gives constant lighting conditions, which is why SSO is the standard orbit for optical Earth observation. It is also the most common destination for small satellite rideshare missions.
Medium Earth orbit (MEO)
Medium Earth orbit covers the region between LEO and geostationary orbit. It is used by navigation satellites, including Europe's Galileo system.
Geostationary orbit (GEO)
A geostationary satellite orbits at 35,786 km above the equator. It needs 23 hours, 56 minutes and 4 seconds for one orbit, exactly as long as the Earth needs for one rotation. Seen from the ground, the satellite stays at a fixed point in the sky. This makes GEO ideal for television broadcasting, communications and weather satellites. Satellites usually reach GEO via a geostationary transfer orbit (GTO) and then raise their orbit with their own engines.
Lagrange points
Lagrange points L1 and L2 lie about 1.5 million km from Earth, roughly four times the distance to the Moon. Space telescopes use these points because they offer a stable position with a constant view.
What the orbit means for your launch
The higher and more inclined the target orbit, the more energy the launcher has to deliver, and the fewer kilograms it can carry. When you plan a mission, the target orbit is therefore the first parameter to define. On Carrier Space you can filter transport options by orbit.
Frequently asked questions
What is the difference between LEO, MEO and GEO?
According to ESA, low Earth orbit (LEO) lies below about 2,000 km, geostationary orbit (GEO) lies 35,786 km above the equator, and medium Earth orbit (MEO) covers the region in between.
How long does a satellite in low Earth orbit take to circle the Earth?
ESA states that satellites in LEO travel at approximately 7.8 km per second and complete an orbit in about 90 minutes. This means the International Space Station circles the Earth roughly 16 times a day.
Why do geostationary satellites appear fixed in the sky?
A GEO satellite needs 23 hours, 56 minutes and 4 seconds for one orbit, the same time the Earth needs for one rotation. Seen from the ground, it therefore stays at a fixed point.
How far away are the Lagrange points L1 and L2?
According to ESA, about 1.5 million km from Earth, roughly four times the distance to the Moon and about 1 percent of the distance from Earth to the Sun.
Related reading
- LEO, MEO and GEO Satellites Compared: Altitudes, Uses and Examples
- Sun-Synchronous Orbit Explained: Why Earth Observation Satellites Fly SSO
- Geostationary Transfer Orbit (GTO) Explained: How Satellites Reach GEO
Sources
- ESA, "Types of orbits": esa.int
Cover image: Sunrise over the Earth's horizon, photographed from the International Space Station on 22 February 2022. Image: NASA, images.nasa.gov.