When NASA planned a space shuttle mission to fix the Hubble Space Telescope -- the orbiting observatory hobbled by a defective mirror -- the agency chose its most experienced astronauts, trained them exhaustively for 11 months and gave them 200 custom-made tools to do the job.
But once the six-man, one-woman crew begins its mission -- liftoff is scheduled for early tomorrow -- their most sophisticated piece of equipment will be something that was not dreamed up in a NASA research center, industry think tank or university laboratory.
It was conceived in the shower of a German hotel room.
There, nearly three years ago, while preparing to ask a European Space Agency team if it had any idea how to fix the Hubble, NASA engineer James H. Crocker encountered a shower head that extended and adjusted to accommodate bathers of almost any height.
The invention it inspired -- specially ground mirrors on automated arms that reach into the space telescope's belly and flop into place like that adjustable shower head -- could do what once seemed impossible: install corrective optics to within a few millions of an inch inside an apparently inaccessible part of a satellite 300 miles above Earth.
So much for finding a solution. Now the contraption must be installed in the freezing void of space. Two teams of spacewalking astronauts will try to wrestle Mr. Crocker's phone booth-size optics package -- and another, equally bulky device -- into the 43-foot-long Hubble during the repair mission.
The 11-day flight -- which is scheduled to include five spacewalks, one more than has ever been attempted on any previous mission -- will be one of NASA's most ambitious adventures. It will also be one of its riskiest -- in terms of both the mission's success and NASA's status as a federal agency.
Although shuttle program managers downplay the need for an unalloyed success, congressional aides and other NASA watchers believe that the future of the space agency, and perhaps human space flight itself, may be at stake.
Success in repairing Hubble would help the National Aeronautics and Space Administration repolish its reputation, which has been tarnished by a string of high-profile failures, from the fatal Challenger disaster in 1986 to last summer's disappearance of Mars Observer to the building of the flawed Hubble telescope itself.
Failure to fix Hubble -- or, worse, to blind it by accident or by mistake -- could vaporize the space agency's credibility on Capitol Hill and almost certainly lead Congress to reassess NASA's ability to build the much-criticized Space Station.
"Admittedly, we all feel extra pressure," said Joseph H. Rothenberg, NASA's associate director of flight projects.
"We have had some of the most intensive and extensive training I have ever experienced in preparation for a spaceflight," said mission commander Richard O. Covey, an Air Force colonel who has flown on three other shuttle missions.
The highest-profile assignment for the shuttle crew is to correct the telescope's blurred vision, caused by a flaw in the 96-inch-wide main mirror.
When it left the Connecticut factory where it was prepared, the mirror was the smoothest ever made -- but, unknown to anyone, it was not ground to the proper curvature before being launched into space in April 1990.
This basic flaw has not rendered the space telescope useless, as a number of scientists had predicted at the time the defect was discovered. Indeed, Duccio Macchetta, the science program chief at the Space Telescope Science Institute in Baltimore, said that the Hubble already "has made enormous contributions to astrophysics."
However, Dr. Macchetta said its optical flaw has prevented the pursuit of about half the Hubble project's original scientific program. Delayed, for example, are observations designed to establish the precise size and age of the universe, as well as mapping the evolution of galaxies.