3. The geostationary orbit
Geostationary orbits of 36,000km from the Earth's equator are best known for the many satellites used for various forms of telecommunication, including television. Signals from these satellites can be sent all the way round the world. Telecommunication needs to "see" their satellite all time and hence it must remain stationary in the same positions relative to the Earth's surface.
A stationary satellite provides the advantage for remote sensing that it always views the Earth from the same perspective, which means that it can record the same image at brief intervals. This arrangement is particularly useful for observations of weather conditions. One disadvantage of geostationary orbits is the great distance to the Earth, which reduces the achievable spatial resolution.