From observing the Earth to transmitting communications, different satellites are designed with different tasks in mind and each task requires a different type of orbit.
What is an orbit?
An orbit is the curved path an object in space takes around another object, like the Earth. Satellite orbits must be far enough from the surface of the Earth to avoid atmospheric drag, but the further out you go, the less detail you can see on the Earth and the longer it takes to complete a full orbit. Which orbit you choose depends on your mission.
What’s the best orbit?
Need high resolution images of the Earth? Then you want a low Earth orbit (LEO).
Have a constellation of satellites for GPS? Then a medium Earth orbit (MEO) places you close enough for easy and quick communication, but far enough to get global coverage.
Want to provide satellite communications for polar regions? A highly elliptical orbit (HEO) speeds through its closest approach, slowing down over high latitudes.
Need constant communication with a point on the Earth? Then a geostationary orbit (GEO) with an orbital period of one day will stay above the same spot on the equator.
Looking to map or study the entire planet? Then a polar orbit will pass from pole to pole while the Earth spins below, viewing the entire surface.
Need constant power and lighting conditions for weather observation or reconnaissance? A Sun synchronous orbit (SSO) is perfect.