EUMETSAT’s satellites fly in two different types of orbit. The Meteosat satellites fly in a geostationary orbit (GEO), while the polar orbiting Metop satellites fly in a sun-synchronous low Earth orbit (LEO).

A geostationary satellite is positioned above the Equator and orbits the Earth at the same rotation speed as the Earth itself, making it appear stationary from the point of view of an observer on the Earth’s surface. It flies very high above the surface of the Earth, and thus is able to capture the whole Earth disc at once.

A polar orbiting satellite circles the Earth at a near-polar inclination, meaning that it always passes almost exactly above the poles. The satellite passes the equator and each latitude at the same local solar time each day, meaning the satellite passes overhead at essentially the same solar time throughout all seasons of the year. The low Earth orbit is much closer to Earth than a geostationary orbit, and thus can see a smaller part of the Earth below than a geostationary satellite, but in finer detail.

The two types of weather satellite, polar and geostationary, should be seen as complementary. Each type has advantages and disadvantages, and an ideal observing system combines both elements.

Geostationary Orbit Advantages:

• Satellite permanently visible from all points within a large coverage area (about a third of Earth's surface). Allows sampling as often as technically possible (every few minutes at best), enabling monitoring of rapidly-evolving events.
• Only one ground station needed for satellite monitoring.

Geostationary Orbit Disadvantages:

• Polar regions are not observed.
• Low ground spatial resolution. The high orbit imposes a limit of about 1 km at best with current instrument technology.

Polar Orbit Advantages:

• Global coverage.
• Good ground resolution because of low orbit.
• Sun-synchronism produces consistent illumination conditions for observed surfaces, with only seasonal changes.
• A solar energy supply is ensured by sun-synchronism, although the supply changes around the orbit.

Polar Orbit Disadvantages:

• Continuous observation of every point by one satellite is not possible. Each point on Earth's surface is observed at best every orbit (100 minutes) for polar regions, at worst twice per day for equatorial regions. Multi-satellite systems solve this problem.
• Continuous satellite monitoring would require several ground stations.