In a letter to NASA Administrator Sean O'Keefe, Mikulski asked that an independent panel be formed to review issues concerning a shuttle mission to Hubble.
NASA last week said it was calling off scheduled shuttle flights to the space-based telescope as the agency starts the process of retiring the shuttle fleet. President Bush's recently announced plans for space exploration did not include a shuttle program.
Astronauts have visited the Hubble three times -- the last in March 2002 -- since the instrument was placed in space in April 1990. A servicing mission was scheduled for this year, but that was before last year's shuttle Columbia accident. O'Keefe said the mission was being canceled because of safety concerns.
The Hubble Space Telescope is run by NASA's Goddard Space Flight Center, which is just outside Washington in Maryland, where Mikulski is seeking a fourth term as senator.
Mikulski asked that the proposed panel report to Congress to assess any risks to astronauts.
"Hubble has become the most successful NASA program since Apollo," Mikulski wrote. "It can not be terminated prematurely by the stroke of a pen without a rigorous review while planning, preparation and training activities continue."
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