Shuttle crew likely to fix Hubble, scientist says December mission will be ambitious

June 17, 1993|By Douglas Birch | Douglas Birch,Staff Writer

GREENBELT -- Astronauts have a 90 percent chance of fixing the Hubble Space Telescope's flawed vision and key flight hardware during their December shuttle mission, a ranking NASA scientist said yesterday. But, he estimated, they have only a 50-50 chance of finishing all the repairs on the 12-day flight's ambitious agenda.

"This is the most complex [spacewalk] mission that a shuttle crew has ever attempted," said Edward J. Weiler, Hubble Space Telescope program scientist, speaking to reporters attending the first day of a two-day conference on the Hubble repair mission at the Goddard Space Flight Center. The conference concludes today at the Space Telescope Science Institute in Baltimore, the center for Hubble research.

The National Aeronautics and Space Administration and its contractors recognize that the flight -- which is scheduled to include a record five spacewalks and may require seven -- is not just another shuttle launch, Dr. Weiler said.

"I think everybody has the feeling that, whether we like it or not, this program is going into the history books," he said. The success of the repair effort, he said, will determine whether Hubble is remembered as "a national disgrace or a great American comeback."

Dr. Story Musgrave, payload commander for the mission, called it "one of the most ambitious things that we have ever attempted to do."

But, he added: "I think we're going to get it all done."

Dr. Musgrave is the leader of a four-astronaut repair crew that is expected to perform 11 separate repair tasks during a series of six-hour spacewalks -- from replacing the Hubble's wing-like solar arrays to installing delicate equipment designed to compensate for the light-smearing flaw in the telescope's 94.5-inch main mirror.

To correct Hubble's vision, astronauts must perform two tasks.

First, they have to install toward the rear of the telescope a telephone-booth-sized box containing a Christmas tree of corrective lenses -- called the Corrective Optics Space Telescope Axial Replacement, or COSTAR. This unit will redirect light into three of the Hubble's scientific instruments.

Second, the astronauts have to replace a fourth instrument, the Wide Field Planetary Camera.

The new optical hardware will permit Hubble to glimpse objects 10 to 15 times more faint than it can now, NASA officials said. The telescope, they said, also should be able to make clear images of objects three to four times farther away -- extending its range from about 4 billion light-years to about 12 billion light-years. The universe is thought to be between 10 billion and 20 billion light-years across.

Replacing the solar arrays will make the spacecraft more stable during observations. Now, the arrays flap when they heat up and cool down every 96 minutes, as the orbiting spacecraft moves into and out of the Earth's shadow.

Installing more computer memory, replacing three of six gyroscopes and fixing other flight hardware will ensure that scientists can continue to steer and aim Hubble. And astronauts will try to repair the High Resolution Spectrograph, an instrument used for studying the skies.

The repair mission will sacrifice some scientific instruments now on board Hubble. A device called a High-Speed Photometer, for example, will be removed to make room for COSTAR. And while the old Wide Field Planetary Camera had eight separate cameras inside, the new one will have only four -- to make room for the corrective equipment.

A May 25 report by an independent task force said NASA might not have enough time to plan and train for the repairs, and fretted that pieces of hardware continue to fail at a "worrisome" rate.

The panel, led by Dr. Joseph F. Shea of the Massachusetts Institute of Technology, called on NASA to begin planning for a second repair mission to begin six months to a year after the December flight.

But Randy Brinkley, director of the shuttle repair mission, said yesterday that he and other NASA officials will decide whether to prepare for a second mission in October, after they review the results of months of rehearsals by astronauts working in water tanks to simulate the near zero-gravity of space.

He said NASA will consider the question again after astronauts complete their replacement and repair work during the first mission.

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