Updated

Senators asked NASA to seek an outside analysis of the agency's plans to cancel a repair mission to the Hubble Space Telescope (search), a decision that would eventually lead to the loss of the orbiting observatory.

At a hearing of a Senate subcommittee on NASA and other federal agencies, Sen. Barbara A. Mikulski, D-Md., told NASA (search) administrator Sean O'Keefe (search) that she was "shocked and surprised" at his decision in January to abandon the Hubble and said that it is too drastic a step to take without further study.

The telescope has provided scientists a wealth of information on space and its far-flung galaxies. The Hubble was designed to be serviced by the space shuttle. Without a repair mission, the telescope will eventually fall out of orbit.

"Canceling the final servicing mission for Hubble is major surgery. Any prudent person would get a second opinion," Mikulski said. "That kind of decision should not be made by one person alone."

Mikulski said the Hubble "is not a piece of technojunk that is tattered and worn" and that a service mission to replace ailing equipment on the telescope could extend its life for years. Some of that equipment has already been built and astronauts have trained for the mission.

Mikulski and subcommittee chairman Christopher Bond, R-Mo., asked O'Keefe to request a study of the Hubble plan by the National Academy of Sciences. O'Keefe said he was already in discussions with the academy, an independent, non-government organization of prominent scientists and engineers.

O'Keefe said the decision to cancel the Hubble service mission was made in response to NASA's effort to follow the recommendations of the Columbia Accident Investigation Board (search). The board's report said that space shuttle flights to the International Space Station would provide a safe haven for astronauts if the space shuttle is damaged - as occurred during last year's Columbia mission, in which seven astronauts perished on re-entry because of damage the craft sustained during launch.

A trip to the Hubble, which is in a different orbit, would not afford this measure of safety.

President Bush has proposed that the space shuttle stop flying in 2010 and that the remaining shuttle flights concentrate on completion of the International Space Station (search). Bush has also proposed that NASA develop a new spacecraft capable of going to the moon and Mars, with a tentative first launch of 2014.

In a letter to Mikulski, Adm. Harold Gehman Jr., chairman of the CAIB, said that a Hubble repair mission would be "slightly more risky" for the space shuttle than a mission to the space station. He said the major risks of a space shuttle mission are during the launch and the landing. Where the craft goes once it is on orbit, he said, "makes little difference" in the risks.

"I suggest only a deep and rich study of the entire gain/risk equation can answer the question of whether an extension of the life of the wonderful Hubble telescope is worth the risks involved," Gehman said in the letter.

In a joint letter, Bond and Mikulski said that "further study and analysis by independent experts is required before a final decision is made to cancel" the servicing mission.

In his testimony, O'Keefe said he wants the analysis to look not only at the risks, but also other Hubble options, such as ways to extend battery life and perhaps using some robotic system to service the telescope.