Crew prepares to take on Hubble trouble Mission to repair ailing telescope lifts off Dec. 1

THE BALTIMORE SUN

Tomorrow, submerged in an underwater tank in Houston, a team of astronauts will insert a telephone-booth-size device into a replica of the Hubble Space Telescope in a dress rehearsal of The Big Fix -- NASA's $251 million mission to service the space observatory and repair its flawed vision.

Dressed in 250-pound spacesuits, astronauts Kathryn C. Thornton and Tom Akers will take their turn in the buoyancy pool at the Johnson Space Center as part of a marathon, 59-hour simulation of the agency's most ambitious shuttle mission ever, a kind of mega-mile maintenance check of the four-story telescope that is orbiting 380 miles above the Earth.

It will be an often-practiced, well-choreographed preview of the main event -- an 11-day mission aboard the shuttle Endeavour, planned for a Dec. 1 liftoff from Cape Canaveral. The mission -- whose price tag doesn't even include the $378 million cost of launching the shuttle -- encompasses a record-breaking five spacewalks performed by four of the seven-member crew, among the country's most senior and experienced astronauts.

Planned as a routine servicing flight even before Hubble was launched into space April 24, 1990, the mission has become a crucible for the National Aeronautics and Space Administration, an exacting challenge to correct a colossal mistake in the $1.5 billion telescope that has kept the world-class observatory from doing all of the science it was designed to do.

The disappointment was felt strongly at the Space Telescope Science Institute, the center on the campus of Johns Hopkins University that coordinates the astronomical use of the observatory. But it also pushed the institute staff to develop a creative, innovative solution to the problem.

"Hubble is our eyes. It's how we are going to see back to the beginning of the universe," said Dr. Thornton, a 41-year-old physicistwho will be making her third space flight. "It's how we tell what's happened to us in the past and where our universe is going in the future."

Not only should the mission -- if successful -- prolong the life span of Hubble by replacing worn-out parts and expanding its astronomical repertoire, it should enhance NASA's record of space repairs. And it holds the potential to restore reputations that suffered when NASA revealed that Hubble's perfectly polished 8-foot primary mirror was misshapen.

"We know, whether we like it or not, this program will go down in history," said Edward J. Weiler, the chief Hubble program scientist at NASA. "This is the most aggressive and difficult mission NASA has ever tried with the space shuttle. We said we had a way to fix it, and we said we would go up in 1993 and do it . . . and we're going up and do it."

When NASA built Hubble, it envisioned just such missions to ensure the telescope's 15-year life span.

It was made to be touched by human hands -- although these will be in pressurized gloves. Astronauts who might one day blast off into space to fix it were consulted during design of

Hubble. This "user-friendly" telescope sports 225 feet of hand rails and 31 sites to attach foot restraints.

The telescope's tool box -- containing some 91 tools -- snaps into a wall of the shuttle bay for easy access during repairs. And, the astronauts will carry a kind of space tool belt attached to their chest. These space mechanics will be hoisted to those hard-to-reach places by a robotic arm, much like a utility worker in a cherry-picker.

"Although we are dealing with a very complex scientific instrument,our job as astronauts is not a very intellectual task," said astronaut Jeffrey A. Hoffman, 49, an astrophysicist whose first walk in space in 1985 involved rescuing a crippled satellite.

"The challenge has not been intellectually to develop some fundamentally new techniques of working with space physics or celestial dynamics. It's been very nitty-gritty, nuts-and-bolts type work, of trying to figure out how to do a lot of work in a limited amount of time using our mid-1990s spacewalking technology."

In some ways, the work seems the stuff of handymen: turning bolts with a power tool that resembles a cordless drill, removing blown fuses, cranking down on ratchets with wrenches. But make no mistake, the work will be time-consuming and tedious, choreographed in slow motion to protect against jostling sensitive equipment, and executed in weightless, frigid space.

It involves tasks no person has ever accomplished in space, repairs that come none too soon for the telescope's life's work -- peering into the solar system, singling out its so-called "black holes," photographing the cores of galaxies.

In one of the first space walks, Payload Commander F. Story Musgrave, 58, will crawl inside the guts of the telescope and squeeze behind a bank of internal components to replace a pair of Hubble's faulty gyroscopes -- instruments that allow the telescope to remain precisely fixed on an object.

"We lose one more gyro, and we're in a no-science mode," said Specialist Musgrave, who has clocked more than 598 hours in space.

Besides the flaw in the telescope's main mirror, the solar panels that produce electricity shake when Hubble passes from darkness to sunlight, and two of the memory units in the telescope's primary flight computer have failed.

To prepare for the mission, the seven astronauts have been training since March 1992. Beyond the 100 hours of classroom instruction, the crew members who will service the telescope spent a total of 400 hours in deep water tanks that simulate

weightlessness.

Among the key aspects of the mission are:

* Replace a pair of gyroscopes.

* Replace the Wide Field Planetary Camera -- a 610-pound instrument about the size of an office desk -- with an updated model that has been refitted with optics to correct the telescope's blurred vision.

* Remove a High Speed Photometer (which NASA contends has done less science than four other instruments on the telescope) and install the Corrective Optics Space Telescope Axial Replacement (COSTAR), the telephone-booth-size device designed at the Space Telescope Science Institute at Johns Hopkins University. Built by Ball Aerospace, COSTAR utilizes seven mirrors, some no bigger than a thumbnail, to cancel out the spherical aberration in Hubble's main mirror.

Other tasks include replacing the jittery solar panels, changing magnetometers and refitting the telescope's flight systems computer.

Despite the costly addition of corrective optics for Hubble, NASA kept the service mission within the budget originally allocated for it.

If either the planetary camera (known as WIFPIC2) or COSTAR can be installed, Hubble will regain its ability to see faint objects that are 10 billion to 12 billion light-years away and those that are close to one another. Without those features, the telescope has been able to do only a tenth of the projects planned for it.

While no one disputes the quality of the good science so far or the fact that the telescope has been busy, scientists across the globe anxiously await the Hubble repair mission.

"If we succeed in fixing it, it will be a vindication for the astronomical community. . . . We will win some honor back," said Holland C. Ford, a Hopkins astronomy professor who helped develop the COSTAR device.

NASA needs a boost. It's still smarting from the discovery of Hubble's flawed mirror -- a recent settlement with the mirror's manufacturer brought the space agency a mere $25 million. Then the Landsat 6 Earth imaging satellite turned up missing, and the Mars Observer spacecraft disappeared.

"All of us in the science community are very much hoping for success [with the Hubble mission]," said Glenn M. Mason, a physics professor at the University of Maryland at College Park.

"Hubble, as the premier science instrument launched in the last some years, is playing a critical role in the question of whether the agency can produce these billion-dollar-plus missions and have them operate as planned. I've got my fingers crossed."

In planning the service mission and designing corrective optics for the telescope, project officials have taken extra precautions to avoid the problems associated with the initial phase of Hubble. Nine independent reviews have been conducted of the design and construction of the corrective optics, Dr. Weiler said.

"All the NASA and contractor people have been fully communicating and discussing" all aspects of the project, said Robert R. Shannon, a University of Arizona astronomer and member of the Hubble review panel who also lent his expertise to this phase of the project. "I think NASA is trying, possibly even too hard, to make sure it all works."

Mindful of Murphy's Law, project officials have devised contingencies and backup plans, Dr. Weiler said. And as the astronauts practice in the deep water tank at the Johnson Space Center this week, they will be thrown curveballs. Equipment may even have been booby-trapped or purposely botched to prepare for surprises associated with a mission as complex as this.

"I'm as comfortable as anyone can humanly be that we can pull this off," said Dr. David S. Leckrone, the Goddard's senior scientist on the Hubble project.

Dr. Weiler added: "We want our kids to read about a great national comeback. . . . We're counting it down by days."

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