Direct Reception Systems
The direct reception systems, DRS, completed the vast network that was put in place for the SITE project. The development of the DRS was started in 1972 at the Electronics Systems Division of the Space Applications Center in Ahmedabad. The system had three main components: the antenna to receive the signals transmitted by the satellite, the front end converter to transform the signals into a form compatible with a normal television receiver, and a television receiver.
The antennas measuring ten feet in diameter, the front end converter, the most complex one in the assembly, and the television sets were first designed in the Space Application Center (SAC) in Ahmedabad. The prototypes were given to a public sector company, the Electronics Corporation of India Limited (ECIL), located in Hyderabad, for mass production. The television monitor itself was basically a commercial model slightly modified for community viewing and rural use. “Seven hundred of the 2400 sets were ‘ruggedized’ by using higher quality components, as a part of an ‘experiment-within-an-experiment’ to investigate the tradeoffs between initial cost and maintenance cost.”32 To facilitate transfer of ‘know-how’ and to expedite production, some ISRO engineers who had developed these units were posted to ECIL.33
The direct reception systems were deployed in selected villages and the districts of six states, namely, Andhra Pradesh, Bihar, Karnataka, Madhya Pradesh, Orissa, and Rajasthan. The villages were selected according to the criteria laid down by the Planning Commission of India. The criteria included availability of electricity, public buildings, low population, and so on. To carry out an organized effort of deployment, operation, and maintenance of these television sets, maintenance subcenters and a central cluster headquarters were established in each state. These cluster headquarters acted as nodes for the distribution and maintenance of the community reception system.
Before the SITE mission in India, the satellite was used to perform a variety of health and education television experiments via satellite in the Appalachian area, the Rocky Mountain Region, and Northwest United States including Alaska.34 In July 1975, while it was being shifted eastward along the equator for the SITE mission, the ATS-6 tracked the docked Apollo and Soyuz spacecraft as they orbited the Earth in the Joint US/USSR manned space mission (see chapter 7). It also relayed live television from these spacecraft to the Earth, thus becoming the first satellite to perform such a feat.35 After this it was positioned at 35,900 kilometers over east Africa and controlled from the Goddard Space Flight Center through a ground station in Spain. Since the downlink SITE frequency of 860 megahertz could interfere with terrestrial services in Europe, its antenna was pointed eastward toward India and away from Europe, thus avoiding interference with European surface broadcasts.