So far, I have explained what LEO and MEO stand for. This time, let’s take a look at the acronym GEO. It’s an acronym for another type of orbit. But how is it different from the other orbits? Let’s find out.
We’ll start with the acronym itself. GEO stand for Geostationary Orbit.
What is a geostationary orbit?
First, a little review. A Low Earth Orbit (LEO) is between ~160 km and ~2000 km above the surface. Orbits between ~2000 km and 35780 km are called Medium Earth Orbits (MEO).
A geostationary orbit is a circular orbit at an altitude of 35786 km above the Earth’s surface. It has an inclination of 0°, which means it is above the equator.
In this orbit, it takes a satellite 23 hours 56 minutes and 4 seconds to orbit the Earth once. This is precisely the time it takes the Earth to complete one revolution. To an observer on the ground, the satellite doesn’t appear to be moving at all.
But what about other orbits at this altitude, are they not called geostationary orbits? No. Let’s take a look at them.
What’s the difference between a geosynchronous orbit and a geostationary orbit?
Geosynchronous orbits are all orbits at an altitude of 35786 km above Earth’s surface. So, the geostationary orbit is a special type of geosynchronous orbit. For geosynchronous orbits, the inclination and eccentricity can vary. A geostationary orbit is always a circular orbit above the equator. This is why, it is also called a geosynchronous equatorial orbit.
As mentioned above, to an observer on the ground, a satellite in a geostationary orbit doesn’t move at all. A satellite in a geosynchronous orbit appears to move in a figure-eight pattern. How much it moves horizontally depends on the eccentricity of the orbit. How much it moves vertically depends on the inclination of the orbit.
| Geosynchronous Orbit | Geostationary Orbit | |
| Height above the surface of Earth | 35786 km | 35786 km |
| Orbital period | 23 hours 56 minutes 4 seconds | 23 hours 56 minutes 4 seconds |
| Inclination | -90° to 90° | 0° |
| Eccentricity | 0 to less than 1 | 0 |
Satellites using these orbits
So, what kind of satellites use geostationary orbits? First, satellites that want to observe a large area of the Earth’s surface from the same point of view. For example, weather satellites, that constantly monitor how the weather is changing in the same region of the Earth.
For the same reason, communications satellites are paced in geostationary orbits. This includes TV broadcasting satellites. What about you? Do you have a satellite dish on your roof? It’s great, that the satellite doesn’t seem to move, isn’t it?
Do you want to know more about acronyms in space? Check out other acronyms.