was used for the Satellite Instructional Television Experiment (SITE)), and with a TWTA-based transmitter of 20 W in C-band (4 GHz). The antenna produced two spots on earth of each, in which the TV broadcast could be received with diameter antennas. This payload was first used over the United States for tele-education and tele-medicine experiments, from August 1974 to May 1975 as part of the HET, or Health, Education, Telecommunications experiment developed jointly by NASA and the US Department of Health, Education, & Welfare (now DHHS). The spacecraft was then moved over the geo-stationary arc from 94 °W to 35 °E, in collaboration with the Indian Space Agency (ISRO), who had deployed in India more than 2500 receive ground stations. The move of the satellite from 94 degrees West to 35 degrees East, a journey of , was actioned from the ground station at Rosman North Carolina This relocation involved 2 rocket burns of the onboard rocket motor. The 2nd burn lasting 5 hours 37 minutes and 17 seconds. The longest burn ever done by a chemical rocket in space at that time. A tele-education programme was started – Satellite Instructional Television Experiment or SITE – and run for one year. During the experiment, a receive station was offered by the Indian Government to Arthur C. Clarke, who was living in Sri Lanka. This experiment was highly successful, and encouraged ISRO to start building an operational program, with the Indian spacecraft INSAT IB (launched 1983). After the SITE experiment, the satellite was brought back over the United States, and served notably as a data-relay and tracking satellite for low-orbit spacecraft such as Nimbus 6, and for the Apollo-Soyuz flight. Particle physics experiments Several particle physics experiments were on board ATS-6. The most significant measured low energy protons (from 25 keV to 3.6 MeV), as well as detected heavy ions (up to 6 MeV). This latter experiment allowed to detect the first heavy ions (Z > 6) with an energy E > 4 MeV, in geostationary orbit. Propagation experiments Finally, ATS-6 embarked several radio beacons, which allowed to measure electromagnetic propagation properties of the atmosphere at 13, 18, 20 and 30 GHz. Decommissioning By June 30, 1979, only one of the four ATS-6 station keeping thrusters was working, and was showing signs of unreliability. This thruster was used to move ATS-6 out of geostationary orbit to an orbit several hundred kilometers