In satellite communications, the altitude of the satellite as well as its orbit is an essential characteristic for the satellite service. According to the three altitude ranges, a distinction is made between GEO satellites, MEO satellites and LEO satellites, as well as HEO satellites with elliptical orbits.
The satellites in geostationary orbit (GEO) are located at a distance of 35,786 km from the Earth's surface and 42,164 km from the center of the Earth. At this distance, the centrifugal force acting on the satellite is equal to the Earth's gravity. The velocity is such that the satellite's orbital period at the equator is exactly one day. Therefore, in relation to the Earth, geostationary satellites appear as if they were "positioned" in a fixed position above the equator line. Since they have no relative motion with respect to the Earth's rotation, they appear to be stationary. They are therefore also referred to as synchronous satellites. Unlike asynchronous satellites, which require the ground station 's satellite antenna to track the satellite, synchronous satellites allow the parabolic antennas to be permanently pointed at the satellite.
GEO satellites have a large footprint on the Earth's surface when their beams are not focused on specific regional areas. To ensure that the exact same hotspot is always illuminated, special antennas are used that are adjusted accordingly as the satellite rotates. These antennas are called despun antennas. Because of the exact stratification possibilities, GEO satellites are used for broadcasting services such as DVB Satellite( DVB-S) or Satellite DAB( S-DAB). They are unsuitable for telephone services because the delay times to and from the satellite and the propagation times in the transmitting and receiving facilities can total more than 300 ms and thus adversely affect voice communications. These high latency times also impair interaction when used as satellite Internet.
A global satellite network can already be established with just three GEO satellites. GEO satellites such as Astra or Eutelsat are used for broadcast services, for broadcasting radio and television programs.