A satellite is only as useful as the data it can bring down to Earth. The ground segment, meaning the antennas, networks and control centres on the ground, is therefore just as important as the spacecraft itself. For small satellite operators it is also one of the areas where the most can be outsourced.
What the ground segment does
- Telemetry, tracking and command: receiving health data from the satellite, determining its orbit and sending commands.
- Payload data downlink: transferring images, measurements or communications traffic to the ground, often at high data rates.
- Mission control: planning operations, scheduling contacts and processing the data for customers.
Why location matters
A satellite in low Earth orbit is only visible from a ground station for a few minutes per pass. Satellites in polar and sun-synchronous orbits pass over the polar regions on every orbit, which is why ground stations at high latitudes, for example in northern Norway, Sweden or on Svalbard, can contact them far more often than stations near the equator. For deep space missions the logic is different: NASA's Deep Space Network uses three complexes in California, Spain and Australia, spaced around the globe so that at least one of them can always see a distant spacecraft.
Own antennas or ground station as a service
Building a dedicated ground station network is expensive. Many operators therefore book antenna time from commercial providers, such as KSAT, SSC or AWS Ground Station, and pay per contact or per minute. This model lets a small team operate a satellite without owning any antenna.
Licensing
Ground stations need frequency licences in the countries where they operate, and the frequencies must match the satellite's ITU filing. Using an established provider usually simplifies this, because many of its stations are already licensed for common bands.
Planning tips
- Estimate the daily data volume early, since it determines the number of passes and the downlink band.
- Choose frequency bands that the intended ground station providers support.
- Plan the ground segment and the launch orbit together, because the orbit decides how often the satellite passes over each station.
Related reading
- Satellite Ground Systems: Ground Stations, Antennas and Network Infrastructure
- Launch Segment, Space Segment, Ground Segment: The Parts of a Space System
- Satellite Spectrum Licensing: How ITU Filings and National Licences Work
Sources
- NASA: Deep Space Network
- NASA Small Spacecraft Systems Virtual Institute: State of the Art of Small Spacecraft Technology
- KSAT: About us
- SSC: Ground Station Services
- AWS: What is AWS Ground Station?
Cover image: NASA's Deep Space Network Goldstone Complex in California. Credit: NASA/JPL-Caltech (PIA23214), public domain.