Finding a Needle with a Haystack

In the autumn-foliaged town of Tyngsboro, Mass., the U.S. space program last week got a handsome present. It is the world's most sensitive radio antenna, a 120-ft. aluminum dish named Haystack for the New England hill on which it rests. Balanced like spokes on a bicycle wheel, protected from the weather by a golf-ball-looking dome that is the world's largest metal-frame radome, Haystack is now tuned and ready. Its tasks will range from radar tracking of a satellite 20,000 miles in space to holding a two-way radio conversation with a speeding space probe 100 million miles from earth.

Near-Perfect Parabola. Haystack is the property of the Air Force, was designed and built by M.I.T.'s Lincoln Laboratory and North American Aviation Inc. for $15 million. Of the total cost, $5,000,000 went in fees for computers, which designed and redesigned the antenna 42 times. The painstaking expense was worth it, producing an antenna that misses, by the thickness of a paper match, being a perfect parabola. Haystack can resolve objects down to 1/60th of a degree, could zero in on an area of the moon just 225 miles in diameter v. 4,500 miles for the bigger but less sensitive Jodrell Bank antenna in Britain. If the need ever rose, Haystack could track an object no bigger than a needle orbiting the earth 500 miles out in space. "Haystack has the same capacity for angular resolution as the human eye," says Project Engineer Herbert G. Weiss, 46. "For its size, it is the most precise movable instrument ever built by man."

To give the 171-ton Haystack its phenomenal accuracy required miracles of designed precision. The huge aluminum antenna floats, for instance, on a film of oil not much thicker than a human hair, moves on a 30-ton bearing with the ease of a ship's gyro. The oil bearing eliminates what engineers call "stiction," for static friction, enables the antenna to rotate through more than three degrees of arc in less than one second, make a complete 180-degree about-face in less than one minute. With such agility, Haystack can track anything that can be tossed into space, right down to a fast, low-altitude satellite put up by a hostile military power.

Magnetic Memory. Haystack's radio antenna will also be the most versatile anywhere in the free world. By changing transmitters and receivers it can be used as a superradar, radio telescope, or a radio transmitter to talk to and listen to communications satellites or spacecraft probing the planets. Haystack is so sensitive, and its tasks so enormous, that its operation could never be entrusted to mere men. The antenna beam will be pointed by a Univac 490, which will be able to call on a magnetic memory with a complete astronomical almanac for the sun, moon and eight planets. The computer transmits 250 instructions per second, has in its gigantic memory an incredible total of 28,000 different instructions it can give the antenna.

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