Satellite communication system

Satellite Communication utilisation has become wide spread and ubiquitous throughout the country for such diverse applications like Television, DTH Broadcasting, DSNG and VSAT to exploit the unique capabilities in terms of coverage and outreach. The technology has matured substantially over past three decades and is being used on commercial basis for a large number of applications. Most of us are touched by satellite communication in more ways than we realise.

The potential of the technology for societal applications continue to fascinate ISRO and efforts are on to leverage the benefits of technology to the betterment of mankind. Important initiatives pursued by ISRO towards societal development include Tele-education, Tele-medicine, Village Resource Centre (VRC) and Disaster Management System (DMS) Programmes. The potential of the space technology for applications of national development is enormous.

In the U.S, domestic satellites were mainly used by television broadcasters. In the late 1970s and 1980s, new “satellite” networks such as Home Box Office and Turner Network Television emerged, using satellites to create at a low cost the kind of expensive land-based networks built earlier by NBC, ABC, and CBS. Ground stations operated by local cable companies receive these signals and retransmit them over coaxial cable to homes. Since the 1980s, many American consumers have turned to new satellites broadcasting services, which transmit directly to receiving “dish” antennas small enough to be mounted outside the home. This is possible because transmitters inside the satellites are much more powerful, and thus a smaller, less sensitive antenna can be used.

Beginning in 1961, NASA sponsored more advanced “active” telecommunication satellites containing electronic relays. The idea was to launch numerous satellites into orbit and build corresponding ground stations wherever they were needed. Telephone, television, facsimile, and data could then be efficiently transmitted anywhere at low cost. The first to be launched was AT&T’s Telstar I on 10 July 1962. Telstar I retransmitted TV signals from the U.S to a receiving station in France that same day. It was also the first satellite to use an important new type of microwave transmitting device called the traveling wave tube. This device became a common feature in later satellites.