ATS-6

ATS-6 (Applications Technology Satellite-6) was a NASA experimental satellite, built by Fairchild Space and Electronics Division It has been called the world's first educational satellite as well as world's first experimental Direct Broadcast Satellite as part of the Satellite Instructional Television Experiment between NASA and Indian Space Research Organisation (ISRO). It was launched May 30, 1974, and decommissioned July 1979. At the time of launch, it was the most powerful telecommunication satellite in orbit. ATS-6 carried no fewer than 23 different experiments, and introduced several breakthroughs. It was the first 3-axis stabilized spacecraft in geostationary orbit. It was also the first to use experimentally with some success electric propulsion in geostationary orbit. It also carried several particle physics experiments, including the first heavy ion detector in geostationary orbit.

During its five-year life, ATS-6 transmitted connection programming to various countries, including India, the United States and other regions. The vehicle also conducted air traffic control tests, was used to practice satellite-assisted search and rescue techniques, carried an experimental radiometer subsequently carried as a standard instrument aboard weather satellites, and pioneered direct broadcast TV.

ATS-6 was a precursor to many technologies still in use today on geostationary spacecraft: large deployable antenna, 3-axis attitude control with slewing capabilities, antenna pointing through RF sensing, electric propulsion, meteorological radiometer in geostationary orbit, and direct to home broadcasting. It is also possible that ATS-6 was a forerunner of the large ELINT satellites such as Mentor.