A satellite earth station is also known as a ground station or earth terminal. It is a terrestrial radio station that is designed to communicate with spacecraft or reception of radio waves from astronomical radio sources.
Earth stations can be located either on the surface of the Earth or in its atmosphere. They can communicate with spacecraft by transmitting and receiving radio waves in the extremely high frequency or super high frequency bands. When a satellite earth station transmits radio waves to a spacecraft or spacecraft transmits radio waves to a ground station, it creates a telecommunication link.
Ground stations may have a fixed or itinerant position. They can be used to telecommunicate with satellites. Other types of ground stations can communicate with manned space stations or unmanned space probes. Earth station that receives telemetry data or follows a satellite, not in geostationary orbit, is known as a tracking station. When a satellite is within the line of sight of a ground station, the station can have a view of the satellite. It is generally possible for a satellite to connect with more than one earth station at a time. A pair of ground stations has a satellite in mutual view when the stations share synchronized and clear contact with the satellite.
If we explain in simple words, ground stations or earth stations are surfaced-based facilities designed to provide real-time communication with the satellite. The team member at these stations sends radio signals to the satellite, receive data transmission from the satellite and sometimes, serve as command as well as control centers for the satellite network. From the earth stations, data can be analyzed. The altitude as well as the movement of the satellite and information about its critical system can be observed and satellites can be controlled by decision makers.
If there is an issue with a satellite, the team member at these stations will be first to know. They work to figure out the source of the problem and devise a solution. In simple words, the earth station or ground station is the brain of the overall satellite network. The satellites themselves can work properly, but there is no use if there is no one down to put the data satellites collect and transmit to use and ensure that the overall system is working fine.
Satellite Earth Stations – Design Consideration
The type of equipment available in earth stations may vary depending on the type of satellite as well as the nature of the mission. However, there are some similarities in all stations. Some of the elements of a typical satellite earth station include:
- The system clock
- Antenna system
- Transmitting as well as receiving RF equipment
- Mission data recovery
- Data-user interface
- Station control center
- Telemetry, tracking and command equipment
You might think how do government-owned space agencies decide whether to build their satellite earth stations? Well, this is completely determined by the type of satellite being used, their orbital path and the required coverage. Mostly, the optimal locations for earth stations are not places where command and control are performed. That is why the mission data will have to communicate to other ground stations or directly to end users at their location.
Talking about design considerations, low earth orbit systems are challenging because of their high orbital speed. Typically, it makes a full orbit every 90-110 minutes due to which an earth station can only connect with it during the windows of time when it is above the station’s horizon plane.
