Television could not exist in its contemporary form without satellites. Since 10 July 1962, when NASA technicians in Maine transmitted fuzzy images of themselves to engineers at a receiving station in England using the Telstar satellite, orbiting communications satellites have been routinely used to deliver television news and programming between companies and to broadcasters and cable operators. And since the mid-1980s they have been increasingly used to broadcast programming directly to viewers, to distribute advertising, and to provide live news coverage.

Arthur C. Clarke, a British engineer turned author, is credited with envisioning the key elements of satellite communications long before the technical skill or political will to implement his ideas existed. In 1945 he published a plan to put electronic relay stations--a radio receiver and re-transmitter--into space at 23,000 miles above the earth's equator. At this altitude, the satellite must complete a full rotation around the earth every 24 hours in order to sustain orbit (countering the pull of the earth's gravity). Given the rotation of the earth itself, that keeps the satellite at the same relative position. This "geosynchronous orbit" is where several hundred communications satellites sit today providing telephone and data communications, but mostly, relaying television signals. Television is currently the largest user of satellite bandwidth.

An "uplink" transmitter on earth, using a "dish" antenna pointed toward the satellite, sends a signal to one of the satellite's "transponders." The transponder amplifies that signal and shifts it to another frequency (so as not to interfere with the incoming signal) to be transmitted back to earth. A "downlink" antenna and receiver on earth then captures that signal and sends it on its way. The essential advantage of the satellite is that the uplink and downlink may be 8000 miles apart. In practice, satellite communications is more efficient over a shorter distances than that, but the advantages over terrestrial transmissions--cable, fiber optics, and microwave--are profound, particularly across oceans. As with Direct Broadcast Satellites (DBS), satellites can transmit to an unlimited number of ground receivers simultaneously, and costs do not increase with distance.

Each satellite has a distinct "footprint," or coverage area, which is meticulously shaped and plotted. In 1971, the first communications satellites carrying "spot beam" antennas were launched. A spot beam antenna can be steered to focus the satellite's reception and transmission capabilities on a small portion of the earth, instead of the 40% of the earth's surface a wider antenna beam could cover. Spot coverage is crucial in international broadcasting, when neighboring countries may object to signal "spillover" into their territory.

Communications satellites since the 1960's have received uplink signals in a range of frequencies (or "bandwidth") near six GHz (gigahertz, or a billion cycles per second) and downlinked signals near four GHz. This range of frequencies is known as "C-band." Each range of frequencies is subdivided into specific channels, which, in the case of C-band, are each from 36 to 72 MHz wide. A single analog television transmission may occupy enough bandwidth to fully utilize a single 36 Mhz channel. Hundreds or thousands of voice or data signals requiring far less bandwidth would fit on the same channel. In the 1980s a new generation of satellites using bandwidths of 11 to 12 GHz (uplink) and 14 GHz (downlink) came into use. The "Ku-band" does not require as much power to be transmitted clearly, thereby permitting the use of small (and less expensive) earth stations for uplink and downlink. With the introduction of the Ku-band, television entered the era of live news--satellite news gathering (SNG)--as "Ku-band" satellites made it easy to uplink television signals with a portable dish from the scene of a breaking news story. Television news has also made some use of another satellite technology, remote sensing, using pictures taken by satellites to illustrate or verify news stories.

In the late 1970s, with the satellite distribution of Home Box Office, home satellite dishes, or "television receive only" (TVRO), became popular for people out of reach of cable television. Later, direct satellite broadcasting (DBS) to small home dishes became possible through the use of these higher frequencies. Since 1988 DBS has been heavily used in Europe, and it is rapidly gaining popularity in the United States. Overuse of the C and Ku bandwidths and the desire for even greater signal strength is leading to new satellites that use other areas of the radio spectrum. A typical communications satellite launched in the early 1990s has a mix of C and Ku-band transponders, and is capable of relaying over 30,000 voice or data circuits and four or more television transmissions. Telephony and television use roughly equivalent portions of available satellite capacity, but the demand for DBS has led to a number of satellites dedicated to TV transmission.

Like other communications technologies, the satellite industry has embraced digitalization and signal compression as a means of maximizing the use of limited bandwidth. By converting analog signals to digital signals, less bandwidth is required, and digital signals can be broken into smaller pieces for transmission through bits of available bandwidth, and reassembled at the point of reception. Compression eliminates otherwise redundant portions of a television transmission, allowing for a signal to be sent using far less bandwidth. Encryption, or scrambling, of satellite television signals is now becoming common to ensure that only customers who have bought or rented a decoder can receive transmissions. Even inter-company television feeds via satellite, such as daily feeds to broadcasters from television news agencies, are being encrypted to prevent unauthorized use. Typical television transmissions via satellite in the 1990s are digital, and are often compressed and encrypted. Compression technology is expected to considerably increase the number of DBS services available.

Some developing countries have demonstrated success in using satellite delivered television to provide useful information to portions of their populations out of reach of terrestrial broadcasting. In 1975, an experimental satellite communications project called SITE (Satellite Instructional Television Experiment) was used to bring informational television programs to rural India. The project led to Indian development of its own satellite network. China has also embarked on a ambitious program of satellite use for development, claiming substantial success in rural education.

STAR-TV, controlled by media mogul Rupert Murdoch, transmits television programming over much of Asia and has forced governments worldwide to reevaluate their stance on issues of national sovereignty and control of incoming information. STAR-TV reaches over 50 countries and potentially half of the world's population--far more than any other satellite television service (though it is technically not DBS, still requiring larger dishes). A slew of contentious political and cultural issues have resulted. Murdoch dropped BBC World Service Television from his STAR-TV program lineup as a concession to the Chinese government. Other governments have complained about the unrestricted importation of news presented from an Anglo-American viewpoint, though their concerns about political consequences are often couched in terms of protecting local culture. Reports of disruptions to local cultures stemming from international satellite broadcasting are widespread.

In all these instances satellite technology has called into question conventional notions of the nation state. Geographic borders may be insufficient definitions of culture and nationality in an era of electronic information, beamed from multiple sources into the sky, and down again into almost any location.

-Chris Paterson