The Hubble Space Telescope pictured in orbit in February 1997 by the last Shuttle crew to make a service call. Photo: NASA/JSC

With the Hubble Space Telescope in scientific shutdown because of gyroscope failures, launch of the shuttle Discovery on an already planned four-spacewalk repair mission has taken on added urgency.

"This is a big hit for astronomy," said astronomer-astronaut John Grunsfeld, one of four spacewalkers assigned to the flight. "We need to get off the ground, go up and fix the telescope."

NASA originally intended to launch Hubble Servicing Mission 3 -- SM-3 -- next April to install six new gyroscopes, a new camera and a variety of other components to upgrade and refurbish the nine-year-old observatory. But last February, the U.S. space agency was forced to change its plans when the third of six stabilizing gyroscopes malfunctioned, leaving the telescope with the bare minimum needed - three - to conduct scientific observations.

Realizing a fourth gyro could fail at any time, putting Hubble into electronic hibernation, NASA managers decided to break up Servicing Mission 3 into two flights, Servicing Missions 3A and 3B, and to launch the SM-3A mission aboard shuttle Discovery as early as possible this fall.

"Obviously, it's such a unique observatory and the harvest from it has been so fantastic, [project scientists are] reluctant to have it in safe mode," William Readdy, NASA's shuttle operations manager in Washington, said at the time. "Understand, we can go get it and service it even if there are no gyros remaining. So it's not a question of the safety of the spacecraft. It's a question of losing science."

And that science is expensive: It costs NASA some $21 million a month to operate Hubble. More important, perhaps, Hubble is one of the crown jewels of America's space program, one that generates a steady stream of world-class science. Allowing such a national resource to sit idle, even briefly, was not a pleasant prospect.

"It's not just the astronomical community that loves it," said Grunsfeld. "I think everybody loves it. We regard this as a maintenance mission, but a very high profile one."