Space: A Cold Look At The Cosmos

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And problems heat up for the space shuttle Challenger

"The scientists are walking three feet in the air. They're absolutely ecstatic." So said a NASA spokesman last week as data began pouring down from one of the most unusual instruments ever launched into space. The cause of the jubilation is a one-ton cylindrical-shaped object called the Infrared Astronomical Satellite, or IRAS. A first of its kind, the solar-powered spy in the sky will literally show the universe in a new light.

Peering into the heavens from its orbital perch, the $180 million robot observatory "sees" infrared light, or heat waves, a form of radiation totally beyond the range of human vision (and that of most living things other than rattlesnakes). Even cold objects radiate some heat, making it possible for IRAS to sense celestial bodies that are all but undetectable in other parts of the electromagnetic spectrum.

Until now such observations have been made with extreme difficulty. Since water in the earth's atmosphere absorbs most infrared light, astronomers had to send up instrument-packed balloons and rockets, go aloft in specially equipped planes or perform infrared work in high-altitude observatories like the one atop Hawaii's 14,000-ft. Mauna Kea volcano. But thanks to some extremely innovative, indeed, out of this world, engineering, IRAS bypasses the obscuring atmosphere entirely.

To prevent its own heat, as well as that of space, from interfering with observations of far-off infrared sources, IRAS' sensitive electronic devices must be kept supercold. The telescope's array of detectors, plus its primary lens, a 22-in. mirror, are tucked inside a thermos bottle-like vessel filled with pressurized liquid helium, which keeps the entire mechanism at 4° above absolute zero (—459.7° F). The detectors are so responsive they could spot a tiny electric bulb on the planet Pluto, nearly 4 billion miles away.

Such sensitivity poses hazards. A fleeting, accidental glance at the sun or the earth could burn out the telescope. Even the strong reflected light of the moon or a bright planet like Jupiter would ruin the observations. For protection, IRAS has a highly polished gold-plated sun shield. But its main insurance is its precise course. Circling the earth once every 103 minutes at an altitude of 560 miles in an orbit that carries it from pole to pole, IRAS roughly follows the line on the earth's surface where day meets night. Along this pathway, the telescope can always face 90° away from the sun, yet catch rays of sunlight on its solar panels to make electricity to power itself.

A decade in the planning, the telescope was built and launched in the U.S., while the rest of the spacecraft comes from The Netherlands. Twice a day IRAS' recorded observations, stored on tape by its computers, are "dumped" in a burst of radio signals as it passes above a ground station at Chilton, England. The signals are retransmitted via a communications satellite to the Jet Propulsion Laboratory in California for detailed computer analysis.

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