A Cold Look At The Cosmos

By Frederic Golden

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 4DEG above absolute zero (--459.7DEG 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 90DEG 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.

In orbit since Jan. 25, the satellite became operational last week when, on command from the British tracking station, the telescope's cover was successfully exploded away. Two quick test scans produced such a flood of data that cheering broke out in the Chilton control room. Said Caltech's Gerry Neugebauer, IRAS' co-chief scientist: "Everything is going even better than we thought it would."

This week IRAS begins the first formal infrared survey of the entire sky, which should become an important guide for future observations. Before it exhausts its helium supply, the telescope is expected to spot as many as a million heavenly objects. IRAS will observe young cool stars now hidden behind veils of tiny dust particles that block ordinary light. It will also study old stars near the end of their lives. Such observations could help clarify the mysteries of stellar birth and death. Closer to home, it may spot the long-sought Planet X, which some astronomers suspect is lurking beyond Pluto.

The orbiting eye should also help establish the true size of our Milky Way Galaxy and discover distant galaxies and quasars. By identifying unknown sources of energy and adding data on the universe's mass, IRAS may help settle the grandest question of all: whether the universe will expand indefinitely or collapse upon itself under the remorseless tug of its own gravity.

Even while it took pride in the performance of the infrared telescope, NASA last week was confronted by new difficulties with the troubled space shuttle Challenger. Standing forlornly on its Florida pad since Nov. 30, the gleaming $1 billion orbiter will probably not be launched before mid-March at the earliest, two months late. Reason: a hazardous hydrogen leak required the removal last week of one of Challenger's three main rocket engines, a task never before attempted while a shuttle was still on the pad.

Using special sensors that can "sniff" the chemical signature of a gas, technicians traced the leak to a 3/4-in.-long crack in the hot-gas manifold, where hydrogen and oxygen are gathered under high pressure (4,400 Ibs. per sq. in.) before combustion. Undiscovered, the leak might have caused an explosion. This week technicians hope to install a new engine, trucked from the National Space Technology Laboratories in Bay St. Louis, Miss.

NASA last week decided to forgo a test firing of the new $30 million engine. Two other test firings, at $1.5 million each, have already taken place. But the space agency still must weigh new quality-control procedures. The crack that ultimately caused the leak was discovered during the engine's manufacture at Rockwell International's Rocketdyne plant in Canoga Park, Calif. The crack was welded, but it was not considered necessary to take the additional step of hardening the weld (cost: about $200,000). Now the space agency faces extra bills totaling about $4 million, to say nothing of irritated customers waiting impatiently on the sidelines for Challenger's liftoff.

--By Frederic Golden. Reported by Bob Buderi/San Francisco and Jerry Hannifin/Washington

With reporting by Bob Buderi, Jerry Hannifin This file is automatically generated by a robot program, so viewer discretion is required.