Launching a satellite 22,000 miles into space orbit is an amazing technological feat – keeping it there requires more advanced systems engineering.
Nearly all missions, whether they be military, civil or commercial, use space ground systems for both launch and on-orbit operations.
Many would say that space ground systems are the workhorse for all satellites and manned spacecraft missions. In fact, according to the Delft University of Technology, space ground systems contribute over 5% of the total cost (more than $25 million for one small satellite) of the entire space system.
Working together to enable management of spacecraft, payload data and telemetry, ground control facilities may be located together in one area or expanded across the globe.
The components of a space ground system generally include:
· Ground stations
· Mission control centers
· Ground networks
· Remote infrastructure
· Launch facilities
Ground stations act as the central nerve system for a satellite mission. The main element of a satellite ground station is a large antenna that physically communicates data from orbiting satellites and then processes that data into actionable reports for human operators.
Typically, a satellite transmits telemetry data about its state or position to a ground station. The ground station will then transmit data back to the satellite with command and control instructions such as orbit corrections.
Ground stations never sleep. Operating 24 hours a day, they may be controlled and monitored remotely and can support multiple satellites, repositioning to communicate with each one.
Another important component in a space ground system is the mission control center (MCC).
The MCC takes over operations from the launch control center (LCC) once the satellite clears the tower during the launch process.
MCC’s determine how to process data received from the satellite and what data is transmitted back to the satellite. For example, a satellite reports the momentum of its reaction control wheels (RCWs) in telemetry data that is received by the Ground Station and transmitted to the MCC.
A reaction wheel is a device consisting of a spinning wheel attached to an electric motor (brushless DC), whose speed can be controlled by onboard computer, producing the required torque for attitude control. Making adjustments are crucial because in space there are disturbances like gravity gradient torque and solar radiation pressure torque that provide external torques(Ne) to the satellite which tend to destabilize it.
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