Early Bird Aloft

The three-stage Douglas Delta rocket that rose above Cape Kennedy last week tossed its 85-lb. payload into a high elliptical orbit with neat precision. Early Bird, first satellite to be sent aloft by Comsat (Communications Satellite Corp.), climbed as high as 22,300 miles above the earth, then curved down as low as 776 miles. When this original orbit had been analyzed and Early Bird was at an apogee, a signal from the earth fired a small rocket motor to give just enough extra speed to put the satellite into a circular orbit that matched the earth's 24-hour period of rotation. In effect, the intricate electronic package put together by Hughes Aircraft picked a spot high above the equator between Brazil and Africa, and there it hovered, ready to begin its job of pointing the way toward a worldwide communications network.

Early Bird gets its electric power from 6,000 solar cells; its orbit is so far from the earth that the earth's shadow seldom forces it to depend on storage batteries. Its electronic equipment will pick up radio-telephone and TV signals from earth, amplify them and transmit them back to earth far beyond their normal range.

Even before Early Bird reached its final station, it went to work. American Telephone & Telegraph's great horn antenna at Andover, Me., which is now leased by Comsat, sent a television test pattern up to the satellite. Back the pattern came to Andover, its quality so good that Siegfried H. Reiger, Comsat's technical vice president, proudly told a press conference: "The television capability of the Early Bird satellite is established."

The Price of Altitude. The great advantage of a satellite on a synchronous orbit like the Early Bird's is its fixed position relative to points on the earth's surface. Ground stations that want to use it as a relay always know where to find it, and a single satellite has enough range to carry TV or telephone conversations among all the countries on both sides of the Atlantic. Three synchronous satellites will cover the entire earth, with the exception of small areas near each of the poles.

But a synchronous satellite has disadvantages too. Its great altitude exacts a high price in launching effort, and its signals are weakened significantly by the distance they must travel. The radio waves traveling up and back at the speed of light take about .24 sec. to make the round trip. This would have no effect on TV programs, which move in only one direction at a time, but telephone talkers may be bothered by the extra half-second delay between question and answer.

Comsat plans to station two more Early Birds over the Pacific and Indian oceans to cover the earth, but it is not about to count on synchronous satellites alone. It is also working on communications packages that will circle on lower orbits. They will have to be much more numerous, and ground stations will need a complicated system to keep track of their ever-changing positions, but there is a good chance that they may well prove more practical.

Blizzards from the Sun. Either way, there are problems ahead, especially during periods of sunspot activity, when the earth is frequently bombarded by blizzards of high-energy particles from the sun. But for the present, Comsat is riding high on top of the communications world. Early Bird is built to handle TV programs or 240 simultaneous telephone conversations. The five telephone cables that now cross the Atlantic can handle only 412. If all goes well with Early Bird, the satellite will start shuttling TV broadcasts between the U.S. and Europe on May 2, and commercial telephone service, with its built-in hesitations, will start in June. The "talking explosion" that has long been predicted by communications experts seems to have arrived at last.

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