Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: TUESDAY, May 29, 1990                   TAG: 9005290058
SECTION: NATIONAL/INTERNATIONAL                    PAGE: A3   EDITION: METRO 
SOURCE: Associated Press
DATELINE: CAPE CANAVERAL, FLA.                                LENGTH: Medium

GLITCH WON'T STOP SHUTTLE, NASA SAYS

"That's really our only problem. Everything else is going very smoothly," said NASA test director Al Sofge.

Columbia is scheduled to lift off at 12:38 a.m. EDT Wednesday carrying seven astronauts and a $150 million observatory known as Astro that will be used to study ultraviolet light and X-rays emitted by stars and other objects.

Officials of the National Aeronautics and Space Administration noticed Sunday that the so-called "head-up display," which projects an image of data needed by the shuttle's commander during landings, was displaying incorrect information. Technicians replaced the display, but that did not fix the problem.

Officials determined Monday that the unit's electronics package was at fault and began the eight-hour job of replacing it. The package is about the size of a videocassette recorder and is located in the shuttle's middeck.

The display unit will be tested for eight hours after the new device is installed.

"We can do it in parallel with all the other [countdown] activities without impacting those activities," Sofge said.

Air Force forecasters were predicting an 80 percent chance of favorable weather at launch time.

The nine- to 10-day mission - the first one in five years to be devoted entirely to scientific research - already has been delayed two weeks because of repairs to the shuttle's cooling system. Additional delays could mean even more changes to Astro's observing schedule.

Because of the delay, fewer observations are planned of Comet Austin, which is receding rapidly from Earth. The comet is believed to be on its first trip through the solar system.

"It's sort of fading quickly. We're hoping we can still get some observations in, but we're not as optimistic," said Arthur Davidsen, chief investigator for Astro's Hopkins Ultraviolet Telescope.

Jupiter and some stars cannot be studied now because they are too close to the sun, Davidsen said Monday. If Astro's three ultraviolet telescopes or one X-ray telescope point toward the sun, their instruments could be damaged.

One target - a quasar 10 billion light years from Earth - is in a better position now than it was a month ago, Davidsen said. The quasar will be the faintest object observed by Astro.

Astronomers expect Astro to complement the work of the Hubble Space Telescope, deployed last month in a 380-mile-high orbit during the last shuttle flight. The Hubble cannot detect X-rays and cannot see as much detail in ultraviolet images as Astro.

NASA program scientist Ed Weiler sees Hubble as a basic toolbox and Astro as extra tools.

"You can do most jobs at home with that basic toolbox. But there are always unique things you want to do which might require a ratchet wrench or a power drill," Weiler said Monday. "[Astro] is the ratchet wrench, the power drill."