The Hubble Space Telescope may have won a reprieve as Nasa has agreed to study ways to service it using robots.
By Dr David
BBC News Online science
In January, it said there would be no more risky astronaut visits to re-supply the telescope thereby limiting its life to only a few more years.
Responding to pressure from politicians and astronomers, Nasa has now agreed to have the National Academy of Sciences look at other upgrading possibilities.
Nasa says no promises are being made and the study may not alter its views.
The US space agency's administrator, Sean O'Keefe, is being cautious about the review.
O'Keefe's announcement on 16 January that for safety reasons he would not authorise a fourth shuttle mission to upgrade the observatory's instruments and replace faulty gyroscopes drew immediate objections from astronomers and politicians.
On Thursday, he told a news conference that even critics of his decision to abandon Hubble agreed that there should be no shuttle mission to the telescope that did not comply with safety recommendations of the Columbia Accident Investigation Board.
And he said it was "not likely" that such a mission would ever meet those safety criteria before Hubble stopped working around 2007.
"I'm still very much of the mind that unless the facts change substantially, my decision will stand," he said.
O'Keefe's comments came after he had appeared before the Senate Appropriations Subcommittee that oversees Nasa and agreed to a study of Hubble repair options.
The idea was proposed by Senator Barbara Mikulski who has taken up the cause of preserving the telescope.
Mikulski called the Nasa plan to cancel the servicing mission "major surgery" adding: "Any prudent person would get a second opinion. That kind of decision should not be made by one person alone."
Without the shuttle, Hubble will last only a few years
But following O'Keefe's press conference, Mikulski sent a letter to him saying she was disturbed by his comments that appeared to undercut the reason for the study - giving outside experts a chance to study the options for the telescope's future.
"...I understand that you later said that nothing would change your decision to cancel the final servicing mission," she wrote.
Mikulski said if O'Keefe disregarded Congressional concerns and did not plan for the manned service flight while the study proceeded, she would try to have financing for the mission specifically included in Nasa's forthcoming budget.
The options for unmanned servicing of the Hubble telescope include "autonomous robotic capabilities to provide a power generation capability that is capable of extending the operational life of the Hubble," O'Keefe said.
He added that in his view there were "very promising concepts on extension of power generation capabilities robotically".
Steven Beckwith is hopeful
Stephen Beckwith, director of the Hubble Space Telescope Science Institute, said he was cautiously optimistic.
He said a lot of people at his institution still believed a miracle could happen.
He revealed his team was assuming Hubble's operational life might be only a few years, and scientists were trying to develop ways to extend the telescope's life by using only two gyroscopes instead of three (the previously stated minimum).
If successful, this could allow Hubble to continue its operations to a time when a shuttle repair mission became feasible again.