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Telstar, first telecom satellite, launched 50 years ago

Martyn Williams | July 11, 2012
Fifty years ago this week a Delta rocket roared into space carrying a payload that sparked a revolution in the way the world communicates.

Fifty years ago this week a Delta rocket roared into space carrying a payload that sparked a revolution in the way the world communicates. On board the rocket, launched on July 10, was Telstar, the first telecommunications satellite.

The story of Project Telstar can be traced back to 1955 when John Pierce, a researcher at AT&T's Bell Labs, began looking at the possibility of using space-based stations for communications.

Beginning in 1960, NASA and Bell Labs experimented with bouncing radio via large, metallic balloons and succeeded in sending a signal across the U.S. But engineers soon realized that the Project Echo technology didn't scale. The demands of television transmission required a balloon much larger than could be made at the time.

In stepped the much more sophisticated Telstar.

At about 34 inches (76.2 centimeters) in diameter, the roughly circular satellite (it actually had 72 sides) would spin on its axis in space as it orbited the Earth. Solar panels occupied most of the faces and charged 19 batteries, "of the type used in rechargeable flashlights but specifically designed for the space environment," read a Bell Labs paper of the time.

The electronics, housed in a 20-inch aluminium tube, consisted of an amplifier that would boost the received signal about ten billion times before it was retransmitted. Original plans called for the satellite to relay two channels of television, but weight restrictions of the Delta launch rocket meant this was cut back to a single channel.

It wasn't just the satellite that required significant engineering work.

Unlike today's communications satellites, which sit 36,000 kilometers, or about 22,400 miles, above the equator so that they appear stationary when viewed from Earth, Telstar was in a much lower orbit and appeared to move across the sky. A sensitive tracking antenna was needed to keep in contact with Telstar as it moved from horizon to horizon. The entire orbit took about two hours and 40 minutes, but the satellite was only in a position to relay signals between the U.S. and Europe for about 20 minutes during each of these orbits.

Bell Labs chose Andover, Maine, as the location for the U.S. tracking station, due to favorable terrain and a quiet radio spectrum. Ground stations were built at Goonhilly in the U.K. and Pleumeur-Bodou in France.

 

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