By Dr David Whitehouse
BBC News Online science editor
Nasa chief Sean O'Keefe, responding to criticism, has agreed to reconsider his decision to abandon the successful Hubble Space Telescope.
Shuttle visits are essential for Hubble
On 16 January, he said that because of astronaut safety there would be no more space shuttle missions to maintain and upgrade the orbiting telescope.
No more servicing would limit Hubble's life to approximately three more years.
Mr O'Keefe has now asked Harold Gehman, who led the Columbia accident inquiry, to look into the Hubble issue.
Following Mr O'Keefe's decision Senator Barbara Mikulski, whose home state of Maryland hosts the Hubble Space Telescope Science Institute, sent a letter asking him to reconsider his decision.
In reply, Mr O'Keefe wrote: "I have asked Admiral Hal Gehman, Chair of the Columbia Accident Investigation Board, to review the matter and offer his unique perspective.
"[He] has agreed to undertake this review and offer his view in a thoughtful and expeditious manner."
In a statement Senator Mikulski said: "When someone is told they need major surgery, any prudent person would get a second opinion.
"That's what I told Administrator O'Keefe and that's what he has agreed to do. Hubble has made so many extraordinary contributions to science, exploration, and discovery," she continued.
"We cannot prematurely terminate the last servicing mission without a rigorous review."
Inspect and repair
Mr O'Keefe made the controversial decision because he decided that flying the shuttle anywhere other than to the International Space Station (ISS) was too dangerous following the Columbia disaster.
If anything went wrong on a flight, the shuttle's astronauts would at least be able to wait on the ISS until a way was found to bring them down safely to Earth.
But astronomers pointed out that Nasa would also have to plan for a situation in which the space shuttle got into space but could not dock with the ISS.
In this scenario, Nasa would have to ensure that astronauts could inspect the shuttle, and perhaps repair it, without help from the ISS.
It follows, therefore, the astronomers argue, if the shuttle can go into space without visiting the ISS, it should also be able to visit the Hubble telescope as well.