The U.S. Tracking and Data Relay Satellite System (TDRSS) is a network of American communications satellites and ground stations used by NASA for space communications. The system was designed to replace an existing network of ground stations that had supported all of NASA's crewed flight missions. The prime design goal was to increase the time spacecraft were in communication with the ground and improve the amount of data that could be transferred. Many Tracking and Data Relay Satellites were launched in the 1980s and 1990s with the Space Shuttle and made use of the Inertial Upper Stage, a two-stage solid rocket booster developed for the shuttle. Other TDRS were launched by Atlas IIa and Atlas V rockets.

A tracking and data relay satellite (TDRS) is a type of communications satellite that forms part of the Tracking and Data Relay Satellite System (TDRSS) used by NASA and other United States government agencies for communications to and from independent "User Platforms" such as satellites, balloons, aircraft, the International Space Station, and remote bases like the Amundsen-Scott South Pole Station. This system was designed to replace an existing worldwide network of ground stations that had supported all of NASA's crewed flight missions and uncrewed satellites in low-Earth orbits. The primary system design goal was to increase the amount of time that these spacecraft were in communication with the ground and improve the amount of data that could be transferred. These TDRSS satellites are all designed and built to be launched to and function in geosynchronous orbit, 35,786 km (22,236 mi) above the surface of the Earth.