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Jan 02

The six antennas of the Astra 3B carry television and the Internet to households from Ireland to Kazakhstan. But even a small error in the angle or contour of one of the dishes could translate into a large gap in coverage. So one of the steps in testing a satellite is to map the surfaces of the dishes with microwave-reflection scanners in an anechoic room lined with energy-absorbing foam cones.

Photo: Simon Norfolk





To the technological visionary Arthur C. Clarke, the potential for television to help to forge a “world society” just after World War II was obvious. Except for one little problem: Unlike, say, AM radio transmissions, which follow the curvature of Earth, television signals follow a straight line right out into space. TV can’t get a signal over the horizon.

In a 1945 article, Clarke outlined the problem and proposed what would become, 20 years later, the solution: a device parked over one spot on the globe, 36,000 kilometers above the equator, revolving with the same 24-hour period as Earth itself. Just three such geostationary satellites could channel TV and microwave signals to most of the populated world. Admittedly, Clarke imagined these as permanently crewed stations. (Someone had to replace the vacuum tubes!) But the groove inhabited today by these comsats is still sometimes called the Clarke Orbit.

A total of 288 active communications satellites circle the planet—including Astra 3B, owned by Luxembourg-based SES Astra. Launched on May 21, 2010, Astra 3B is designed to relay Internet and 500 channels of TV to most of Europe and the Middle East—on 10 kilowatts, about a tenth the broadcast power that WCCO-TV uses to cover Minneapolis. And if the availability of, say, Serbian MTV in Bosnia and Herzegovina has failed to bring about a peaceful world society, well, the fault is ours, not Clarke’s. Here we see for the first time the launch of the Astra 3B: its construction in Toulouse, France, its contact with Earth in Luxembourg, and its launch from the European space center in French Guiana.

Courtesy: http://www.wired.com/magazine/2010/12/ff_satellite/

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