WASHINGTON -- Two days after U.S. President George W. Bush unveiled a new NASA vision requiring a shift in the space agencys spending priorities, NASA announced that it was curtailing any further space shuttle missions to the Hubble Space Telescope.
Launched aboard the space shuttle in 1990, Hubble has been serviced by astronauts four times since then. The last such mission was in 2002.
NASA had planned to visit Hubble one last time in 2006 to change out instruments and replace its gyroscopes with the intent of keeping the telescope in service until at least 2011, when its heir apparent, the James Webb Space Telescope, is expected to launch.
Scrapping the final servicing mission raises the likelihood that Hubble will fail before Webb is on orbit. NASA officials said the cancellation of the Hubble servicing mission was driven by concerns about astronaut safety -- heightened in the wake of the Columbia disaster -- not budget issues.
NASA chief scientist John Grunsfeld said conducting the Hubble servicing mission without violating the safety mandates issued by the Columbia Accident Investigation Board would have required the development of potentially costly inspection and repair techniques not otherwise needed.
Because a shuttle visiting the Hubble could not reach the International Space Station if something went wrong, Grunsfeld said NASA would have to have a second shuttle on the launch pad and ready to conduct an orbiter-to-orbiter rescue in an emergency.
Grunsfeld said the decision, announced by NASA Administrator Sean OKeefe on Friday, was driven in part by the need to make tough choices in light of the presidents new vision.
"If we had plans to fly the space shuttle for another 15 years, this is an investment that we might have made to develop for all those rescue scenarios," Grunsfeld said.
Bush stated that all human spaceflight would be directed to support the effort of putting people on the Moon and Mars. The shuttle, which is the only means by which NASA could service Hubble, is to be devoted to finishing construction of the space station.
Astronomers had been concerned since Bush's speech that there "wasn't much wiggle room" to allow for further servicing of Hubble given the new vision, as one astronomer put it.
Kevin Marvel, an official with the American Astronomical Society, confirmed that the NASA chief had decided to cancel Hubble Servicing Mission 4 and had held a meeting with NASA employees today to announce that decision.
Marvel also said that Steve Beckwith, director of the Space Telescope Science Institute, which operates Hubble, held a meeting with his staff at about 3 p.m. EST (2000 GMT) Friday to tell them of O'Keefe's decision.
Marvel said the servicing mission would have prolonged Hubble's life and enhanced its capability with the addition of two instruments.
"Our situation as the [American] Astronomical Society is that we're concerned with the decision," Marvel said. "We haven't taken a position at this point but we're actively trying to learn the details."
Marvel added: "Without extending Hubble's lifetime the science that's currently being done and planned to be done with the new instruments would obviously not be achievable, and that would be an impact on the astronomy community."
Grunsfeld, a left-handed astronaut who earned the nickname "southpaw savante" for the hand he had in the 2002 Hubble servicing mission, said the decision not to return to the telescope was the right choice to make in light of NASA's new mandate.
But that does not make it any easier to let go, he said.
"I have been described by someone as a Hubble hugger because quite literally I have hugged the Hubble, so this is a hard one," Grunsfeld said.
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