The Tracking and Data Relay Satellite (TDRS) system represents a new era in tracking Earth-orbiting spacecraft, including the Space Shuttle, and transmitting their data back to Earth. The TDRS concept was conceived following early 1970s studies which showed that a system of orbiting telecommunications satellites, operated from a single ground terminal link, could more effectively support Space Shuttle, scientific and other NASA mission requirements than the nearly 25-year-old tracking and communications network of ground stations located worldwide. Flight 2 was destroyed on STS-51L (Challenger).
