Understanding MEO
Why navigation systems choose MEO
MEO is a compromise between the two extremes of Earth orbit. A satellite in Low Earth Orbit sees only a small patch of the planet at once, so global coverage there demands hundreds or thousands of craft. A single geostationary satellite covers roughly a third of the globe but sits 35,786 km away, adding signal delay and leaving the poles poorly served. MEO threads the needle: from around 20,000 km each satellite views a large fraction of Earth, yet stays close enough for a usable signal. Two dozen satellites in a few inclined planes then guarantee that four or more are always above the horizon — the minimum a receiver needs to solve for its position and clock offset. A high inclination, such as GLONASS's 64.8°, further improves coverage at the high latitudes that equatorial GEO cannot reach.
The four GNSS constellations compared
All four global navigation systems occupy MEO, yet each chooses a slightly different altitude, inclination and number of orbital planes — trade-offs that reflect national coverage priorities and the physics of ground-track repetition. GLONASS's steep 64.8° inclination, for instance, favours Russia's high latitudes. BeiDou also flies geostationary and inclined-geosynchronous satellites for regional coverage; the table below shows only its MEO segment.
| System | Operator | Altitude | Orbital period | Inclination | Nominal MEO satellites |
|---|---|---|---|---|---|
| GPS | USA (Space Force) | ~20,200 km | ~11 h 58 min | 55° | 24 (6 planes) |
| GLONASS | Russia | ~19,100 km | ~11 h 15 min | 64.8° | 24 (3 planes) |
| Galileo | EU / ESA | ~23,222 km | ~14 h 05 min | 56° | 24 + spares (3 planes) |
| BeiDou | China | ~21,528 km | ~12 h 53 min | 55° | 24 (3 planes) |
Crossing the Van Allen belts
The chief engineering challenge of MEO is radiation. The Van Allen belts — two doughnut-shaped zones of charged particles trapped by Earth's magnetic field — bracket the navigation altitudes. The inner belt reaches up to somewhere between roughly 6,000 and 12,000 km (sources vary on where its edge lies) and the outer belt spans about 13,000 to 60,000 km, so a GPS or Galileo satellite at more than 20,000 km orbits well inside the outer belt and absorbs a far higher dose than a typical LEO craft. Electronics must be radiation-hardened and shielded, solar arrays degrade faster, and designers budget for the cumulative dose over a 12–15 year service life. Intense geomagnetic storms can temporarily swell the belts, which is one more reason navigation operators keep a close watch on space weather.
Beyond navigation: MEO communications
Although navigation dominates, MEO is not only for GNSS. SES operates the O3b and O3b mPOWER communications constellations in an equatorial MEO at about 8,000 km, delivering lower-latency broadband than a geostationary link to ships, islands, remote sites and mobile-network backhaul — without needing the thousands of satellites a LEO broadband fleet requires. A handful of scientific and military spacecraft round out the population. Even so, MEO stays sparsely populated next to LEO's tens of thousands of tracked objects; you can see the current catalogued count in our live satellite directory.