Geostationary satellites orbit at the same duration but are inclined 0˚ to the equatorial plane, meaning that they appear at a fixed point in the sky when observed from the Earth. Although they may move north and south very slightly, GEO orbits ensure that satellites can be ‘seen’ at all times by terrestrial user terminals.
GEO satellites are used for a range of services including telecommunications, TV signals, surveillance and weather monitoring. The first geostationary satellite, Syncom 3, was launched in August 1964 and was used to telecast the 1964 Tokyo Olympics across the Pacific to the United States. In April 1965, Intelsat 1 (Early Bird) was launched, becoming the first geostationary satellite for telecommunications across the Atlantic. VSAT (Very Small Aperture Terminal) satellites on all frequency bands operate in geostationary orbits, and are commonly used for maritime mobile communications.
Owing to their greater altitude, geostationary satellites tend towards higher latency with less spatial resolution of data when compared with NGSO (non-geostationary orbit) satellites. However, in a maritime context, a delay of milliseconds has little impact upon the transmission of certain applications, eg, ship condition reports and live engine data. And for land stations, the main advantage of GEO satellites is that they are always in the same position relative to the earth, meaning that antennas require no reorientation.
A number of new GEO High Throughput Satellites (HTS) have been launched over the course of the last few years. The Satsig.net website reports that as of April 2018, there are 450 active GEO satellites in operation.