Sen. Barbara Mikulski (search) told scientists Friday that she refused to take "no" for an answer when NASA's chief decided not to service the Hubble Space Telescope (search). But she cautioned that telescope's future is not assured.

NASA (search) Administrator Sean O'Keefe at first denied her request to reconsider, she told scientists and staff at the Space Telescope Science Institute, which coordinates the use of the instruments aboard Hubble.

"Well, I don't take 'no' for an answer," said the feisty Maryland senator, the ranking Democrat on the Senate subcommittee that oversees NASA's budget.

O'Keefe relented and sent Mikulski a letter on Thursday saying that Adm. Hal Gehman, chairman of the board that investigated the Columbia shuttle breakup last year, will "review the (Hubble) matter and offer his unique perspective."

Mikulski, however, told the cheering scientists that she did not want to raise false hopes and would accept whatever recommendation Gehman gives on the safety of a Hubble servicing mission.

Scientists say the orbiting Hubble telescope has revolutionized the study of astronomy with its striking images of the universe. O'Keefe, however, had canceled a scheduled shuttle repair mission, citing the risk to the astronauts and President Bush's new focus for the space agency, including missions to the moon, Mars and beyond.

Without the service mission, which had been planned for 2006, scientists believe the orbiting telescope could stop working several years before its scheduled 2010 retirement.

O'Keefe's decision prompted letters from Mikulski and a joint letter from all members of Congress from Maryland, from where the orbiting platform is operated.

"The scientific returns we have received from Hubble's service thus far have exceeded our expectations. ... We believe that NASA should make every possible effort to retain this proven window on the universe," the letter said.

Hubble's fate has also become a cause for amateur and professional astronomers worldwide.

"It's been overwhelming. My e-mail is overflowing," said Steve Beckwith, director of the Space Telescope Science Institute.

"Every day, we've had offers of ideas, political support and even money," he said. "Every day, I get people who want to know how they can contribute to keeping Hubble alive."

NASA spokesman Robert Mirelson said Thursday that O'Keefe has not changed his decision but asked Gehman to give "his view on basically all the questions on the table," including safety, scheduling and the recommendations of the Columbia board.

Mikulski also said she supports the choice of Gehman for the review.

"He will know whether this is a smoke screen to get rid of Hubble for a lot of other reasons," she said.

Mikulski said Congress can appropriate money for the space telescope, but the safety aspects of the decision is in the hands of NASA. The telescope, however, is popular for more than merely scientific reasons, she said.

"Why do people want to save the Hubble? It's because of the story the Hubble tells," Mikulski told the packed auditorium. "It's about discovery ... This country exists because of discovery."