Hubble flies free after release from Columbia following a highly successful service call. Photo: NASA

Scientists around the world are standing in line for a chance to use the Hubble Space Telescope's new camera and other instruments. In fact, in recent months the Space Telescope Science Institute has been flooded with eight times as many observing proposals as the telescope can accommodate.

"Every year we look at a metric, a way of quantifying how the space science programs of NASA hold up in the whole world of science, all areas of science," said Hubble project scientist David Leckrone. "And by this metric, Hubble is the most productive space mission, science mission, and has had the highest impact of all NASA science missions in the history of this agency.

"Without the servicing that we've done and the refurbishment and the upgrades of the technology on Hubble that we've done, this would not continue to be the case," Leckrone said. "But it does continue to be the case, year after year. The current demand for the use of Hubble by astronomers all around the world exceeds our ability to satisfy that demand by a factor of eight.

"This factor of eight is a record, it's the highest it's ever been for Hubble and I attribute that to the eager anticipation the community has for using the Advanced Camera for Surveys. We can just hardly wait to get our hands on it."

Leckrone said Hubble's data output today, with its upgraded instruments and improved data management techniques, is 20 times higher than it was when the telescope was launched in 1990. After the next servicing mission in 2004, the telescope's monthly data output will jump to 44 times its original level.

"Hubble is the most frequently cited space mission in the scientific literature, it's also the most frequently cited space science mission in the media," Leckrone said. "It's a national icon."

The $75 million Advanced Camera for Surveys was installed by astronauts James Newman and Michael Massimino during a spacewalk Thursday, the fourth of five carried out by the shuttle Columbia's crew. Along with installing a new camera, the astronauts upgraded Hubble's electrical system and installed an experimental refrigerator in a bid to revive a dormant infrared camera-spectrometer known as NICMOS.

With their repair work complete, commander Scott Altman and his crewmates relaunched Hubble early today, leaving the 24,000-pound satellite on its own as engineers at the Goddard Space Flight Center begin the weeks-long process of fine tuning the new camera, testing the NICMOS cryocooler and recalibrating the telescope's orientation control system.

"We were a little sad to see the space telescope go," spacewalker John Grunsfeld told an interviewer this morning. "We spent five days out in the payload bay of Columbia doing our repairs. We installed a new power system on Hubble that will carry it into the next decade and installed an Advanced Camera for Surveys. It's the new eye of Hubble, it's a super camera ... that will allow us to see to the edge of the visible universe. The repairs were hard in some cases and some things went really smooth. We were just lucky to get it all done."

Mission manager Phil Engelauf agreed, saying we went into this flight saying this was one of the most challenging missions that we've ever undertaken and that it would be somewhat fortunate if we actually managed to accomplish all of the objectives."

"And yet here we stand today having accomplished virtually every task on the nominal mission list and one or two additional ones that we threw in," he said. "And the work, again, puts us in a good posture with the Hubble Space Telescope to continue its dramatic science."

With Hubble now on its own, the astronauts chatted with reporters this morning and enjoyed the prospect of a half day off Sunday to relax after a busy week in space. If all goes well, Columbia will return to Earth early Tuesday morning to close out one of the most challenging shuttle flights in history.

"We basically turn this orbiting spaceship into an aircraft again for the re-entry, and that takes about a day," Altman said. "And after nine days of hard work we actually get a little bit of time of, a half a day off tomorrow to take a break. We actually are able to do some live video links with our families."

Early Sunday, the astronauts will enjoy a formal ship-to-ship chat with the crew of the international space station, commander Yuri Onufrienko, Daniel Bursch and Carl Walz. This morning, the two crews tested the long-distance communications link and enjoyed a brief pre-chat chat.

"To the crew of Alpha from the crew of Columbia, a hearty hello and congratulations for all the success you're having on your mission," Altman radioed.

"Well thanks, we sure appreciate it," Walz replied from the station. "Yeah, we're just chugging along here, we just passed the three-month mark and congratulations to you all, that's a tremendous amount of work there, five EVAs in five days and now we have just a pretty much brand new Hubble up there. So that is just pretty much superb."

"It's just amazing when you look back on it," Altman said. "I can't believe how much those EVA guys got done. And we were thrilled to be here. I guess we're the sprint and you guys are the marathon. As always, I'm incredibly impressed."

Friday afternoon, Newman and Columbia's robot arm operator, Nancy Curry, caught sight of the space station up ahead of the shuttle in its lower orbit. Early today, Hubble program manager Preston Burch enjoyed a similar thrill, watching Columbia and the space telescope sail over the Johnson Space Center in tandem shortly after the observatory was released into open space.

"Today we said goodbye to Hubble with mixed emotions," he said. "We were glad that servicing mission 3B was successfully accomplished and that Hubble was now ready to go back to work to continue to expand our knowledge of the cosmos with its vastly increased capability. But we also had that empty feeling that one gets when saying goodbye to a friend or a relative after a visit of several days.

"The next servicing mission will be in about two years ... and all of us are looking forward to our next visit with Hubble. After we saw Hubble kind of disappear from view on the television coming down from the orbiter, it was a very stirring sight to go out into the parking lot and see Columbia fly overhead with Hubble in trail. It was a pretty amazing thing."