Theory / LEO, MEO and GEO
LEO, MEO and GEO: altitude changes everything
A satellite’s altitude decides what it sees, how long each lap takes and what it is good for.
| Orbit | Altitude | Period | Typical uses |
|---|---|---|---|
| LEO low | up to ~2,000 km | ~90 min to 2 h | Earth imaging, broadband, space station |
| MEO medium | ~2,000 to 35,786 km | ~2 h to 24 h | Navigation (GPS, Galileo) |
| GEO geostationary | 35,786 km, over the Equator | 23 h 56 min | TV, communications, weather |
The boundaries between bands are conventions, and sources vary a little, especially at the start of LEO (160 km to 200 km, depending on the definition).
LEO: close, fast and detailed
Low satellites are so close to Earth that they go around in about 90 minutes, at some 7.8 km/s. The proximity allows detailed images and a signal with little delay. The International Space Station orbits at about 400 km.
The trade-off: each satellite sees a small area and passes quickly over any point. Covering the whole planet takes many satellites, the constellations. Below a few hundred kilometers, the remnants of atmosphere slow the satellite down and force it to be re-boosted.
MEO: the navigation middle ground
Navigation satellites sit in MEO. GPS operates at about 20,200 km, with a period of roughly 12 hours and an inclination of 55°. At that height each satellite sees a large part of the planet, and a constellation of 24 satellites ensures a receiver has several of them in view at any moment.
The trade-off: MEO crosses the Van Allen radiation belts, which calls for hardened electronics.
GEO: parked in the sky
At 35,786 km over the Equator, the period equals the Earth’s rotation. The satellite follows the planet’s spin and looks motionless from the ground. That is why TV dishes can always point at the same spot, and a single satellite covers about a third of the surface.
The trade-off: the signal takes about 0.12 s just to travel up there, which causes noticeable delay in calls. The poles are poorly served, because GEO exists only over the Equator. And getting a satellite to that altitude costs more.
How altitude trades advantages for drawbacks
- Higher: more visible area, lower speed and longer period.
- Higher: more delay in the signal and higher launch cost.
- Lower: more detail in images, less delay, and less area at a time.
No orbit is better than the others. The choice depends on the mission.
Where this shows up in the games
In Sky Beacon, higher orbits see more of the ship’s horizon, and low ones move faster. In Last Transmission, you choose among the three lanes to reach the station in time. In Right Orbit, you pick the altitude yourself and see how it changes coverage.
Sources
ESA, “Types of orbits”. NASA, SCaN network glossary and the Earth Observatory orbit catalog. Maini, A. K.; Agrawal, V. Satellite Technology: Principles and Applications, 3rd ed., Wiley.