Big Gamble in Space

By DICK THOMPSON GODDARD SPACE FLIGHT CENTER

For the beleaguered masters of America's sputtering space program, the word Hubble has been a synonym for trouble. Launched three years ago and billed as the most magnificent scientific instrument ever put into orbit, the Hubble Space Telescope quickly became known as the $1.5 billion blunder. The very first images from the telescope revealed that its primary mirror was deformed, leaving the instrument distressingly nearsighted.

While computer tricks have helped the Hubble get a good look at a distant supernova and storms on Saturn, the telescope's accomplishments have fallen far short of expectations, and its crippled condition has grown progressively worse. Two of the onboard computer's six memory banks have failed, flapping solar-energy panels have caused some pictures to be blurred, and an instrument that measures the velocity and chemistry of celestial objects has broken down. The latest setback involves the craft's gyroscopes, which enable Hubble to fix its gaze as it orbits. Three of them have failed, and if one more goes down, the telescope that was going to open a new era of astronomy will be scientifically useless.

Now, in a mission worthy of Luke Skywalker and Han Solo, NASA has laid elaborate plans to send a team of seven astronauts on the space shuttle to fix the Hubble in orbit. Set for a December launch, the $100 million effort will require more space walks and more heavy equipment than any other satellite- repair job in history. "This is the mother of all repair missions," says Frank Cepollina, who heads NASA's satellite-servicing program. "We're taking three to four tons of hardware into orbit and installing it over four days using two alternating crews. You're talking about a significant, exciting, pioneering mission."

The high-flying house call is intended to repair not just the Hubble but also the space agency's battered reputation -- a go-for-broke gambit that could backfire. Other efforts to repair satellites, from Solar Max in 1984 to Intelsat last year, have given NASA planners nasty surprises and mixed results. If the Hubble rescue fails, the space program will be piling a fiasco on top of a fiasco. "NASA's credibility is on the line," says Hubble project director Joseph Rothenberg.

So are the big bucks that NASA has long taken for granted. Desperate to attack the budget deficit, Congress is threatening to fire a laser cannon at Space Station Freedom, NASA's planned stepping-stone to the stars. Since the idea was first approved in 1984, its price tag has ballooned from $8 billion to $32 billion. Last week NASA said it was under White House orders to develop a much cheaper design for the space station. How, NASA's critics ask, can it build Freedom at a reasonable cost when its $8.3 million space-toilet program went 182% over budget? The Hubble mission may be the agency's last good chance to prove it can meet a formidable challenge -- within budget -- and to demonstrate the potential value of a work station in space.

Curing Hubble's myopia will require, in effect, giving the telescope a new pair of eyeglasses. Commercial-optics expert Murk Bottema came up with the idea of equipping Hubble with five pairs of quarter-size reflecting mirrors to compensate for the primary mirror's flaw. Mounted on mechanical arms inside a phone booth-size compartment, the new mirrors will collect and focus light on Hubble's instruments.

The most difficult part of fashioning the telescope's new glasses was deciding what prescription to use. How much correction was needed? The scientists studying this question were divided into two teams. The first group, known as the "phase retrieval" team, relied on the data streaming down from Hubble. By comparing images of stars with optical theory, the researchers could calculate the apparent distortion of Hubble's mirror. Their work was confirmed by the "fossil record" team, which went back to the source of the flawed mirror, a Connecticut plant now owned by Hughes Danbury Optical Systems. (At the time of the manufacturing mistake, the facility was part of Perkin-Elmer Corp.) Like archaeologists looking for the missing link, the optical sleuths pored over the blueprints and tools used to make the mirror. Eventually, they zeroed in on a complex device called an interferometer, which was used to measure the curve of the mirror's surface. They found that the instrument had been assembled incorrectly and that the mistake matched the error calculated by the other team: Hubble's main mirror was deformed by less than one-fiftieth the thickness of a human hair.

To ensure against more fumbles, NASA has subjected the Hubble rescue plan to an unprecedented eight mission-review panels, some internal and some outside the agency. "This time, we're doing sanity checks and double sanity checks," says NASA's John Wood, chief of Hubble's optics.

Despite the enormous complexity of mounting the new mirrors, replacing the solar-energy panels and making all the other necessary fixes on the Hubble, the space agency has several factors going in its favor. Unlike every other satellite NASA has flown to rescue, Hubble was designed to be serviced in orbit. Before it was launched, more than 16,000 photographs were taken of every square inch of the spacecraft to ensure that astronauts wouldn't be surprised once they started working. Handrails, footholds and handholds were strategically placed around Hubble, and every bolt was made the same size so that spacewalking mechanics wouldn't have to handle extra tools.

Still, if the replacement parts don't slide easily into place, or if the solar panels refuse to unfurl after the work is done, the Hubble could be worse off than before the mission. Says Princeton astronomer Edwin Turner: "It's a tremendous gamble. If it succeeds, it will be a really impressive feat. Or they could leave us with a nonfunctional spacecraft." And a sharply diminished faith in NASA's ability to explore the last frontier.

With reporting by Jerry Hannifin/Washington