TDRs constellation and ground station, 1980s.
© National Aeronautics & Space Administration / Science & Society
An artist's impresion of a Tracking and Data Relay Satellite System (TDRs) constellation over the Earth and a dedicated ground station. TDRs were geostationary satellites developed by the United States and used to receive data from low-flying satellites before then re-broadcasting the data to the ground. These satellites were launched throughout the 1980s and 1990s using Space Shuttles.