mr-damon/space

If all goes well -- never a given 350 miles above Earth -- the astronauts will install a new camera and spectrograph and change out all the gyroscopes that keep it properly pointed and the batteries that keep it running. They are also planning to repair a broken spectrograph and the Hubble's workhorse, the Advanced Camera for Surveys, which had a severe short-circuit last winter and was pronounced at the time probably beyond repair.

Dramatic turnabouts have characterized the history of the Hubble telescope, which was hailed before its launching in April 1990 as the greatest advance in astronomy since Galileo invented the telescope.

In space, the Hubble would be able to discern details blurred by the turbulent murky atmosphere. But its 94-inch diameter mirror turned out to have been polished to the wrong shape, leaving it with what astronomers call a spherical aberration. The Hubble became branded as a "technoturkey."

In 1993, astronauts fitted the telescope with corrective lenses (at the cost of removing one of its five main instruments, a photometer), and the cosmos snapped into razorlike focus.

Three more visits by astronauts kept the Hubble running and, by replacing old instruments, actually made it more powerful. Along the way, the astronauts graduated from yanking equipment fitted with large astronaut-friendly handles to operating on instruments never meant to be repaired by people wearing the equivalent of boxing gloves in space.

In 2002, after an infrared camera named Nicmos unexpectedly ran out of coolant, the astronauts attached a mechanical refrigerator to run coolant through its pipes. A year later, the Hubble's astronomers used the rejuvenated camera along with the advanced survey camera to record the deepest telescopic views ever obtained of the universe. The images captured galaxies as they existed a few hundred million years after the beginning of time.

"When you have an instrument that reaches so far beyond what you've ever had before, you make discoveries that nobody ever thought of before," said John Grunsfeld, who will be the payload commander on the Atlantis mission. "And we see things that nobody ever saw before. As a result, you know, Hubble became not just an observatory, but an icon for all of science. And Hubble has become part of our culture."