Mon, Jul 28, 2003 - Page 16 News List

Hubble's future up in the air

Launched in 1989, the space-based telescope is currently one of astrophysics' most valuable tools


The next and final astronaut visit to the telescope is scheduled for next year, but might not happen until 2005 or even 2006, depending on when the shuttles start flying again in the wake of the loss of the Columbia in February. On that occasion the telescope will be fitted with two new instruments, and astronomers say it should work well until the end of the decade.

The decision about what happens then has been complicated by the breakup of the Columbia. The telescope is too big to leave to fall out of orbit and crash uncontrollably to Earth on its own. NASA had originally planned to fetch it with the space shuttle and put it in the Smithsonian's Air and Space Museum, but that now seems "exceedingly unlikely," in Kinney's words. Such a mission would take the shuttle into an orbit in which it could not rendezvous with the space station if anything went wrong.

Instead NASA is studying the possibility that a robotic rocket could be sent to attach itself to the telescope and ease it out of orbit safely into the ocean. That would require developing new technology. If it seems feasible, Kinney explained, astronauts could add attachments for the rocket to hook onto during the upcoming service mission.

The telescope is in no imminent danger even if the next service mission is put off indefinitely. It is now in an orbit about 563km high. How long it could stay there depends on sunspot activity, which bloats the atmosphere, causing drag on the telescope. Even under the worst circumstances, Hubble would not fall until 2013, according to a NASA study. But with a series of small altitude boosts supplied by the shuttle in 2005 and 2009, it could stay up until 2020 or beyond.

Leading the charge for another extension are the astronomers of the Space Telescope Science Institute on the Johns Hopkins campus in Baltimore. In a policy statement full of statistics testifying to Hubble's dominance of contemporary astronomy, Steven V.W. Beckwith, the director of the institute, argued that as a result of the astronauts' service calls, Hubble had essentially been reborn every few years, allowing it to stay on top of its game.

"A servicing mission to Hubble is comparable in science value to the launch of a new satellite and should be judged as such," Beckwith wrote.

As a result, the number of scientific papers based on Hubble observations still grows every year.

Beckwith argued that sending astronauts to fit the telescope with a propulsion module would be less risky than trying to develop a robot. If such a trip was necessary, he said, the marginal cost of fixing it up for a few more years of science would be a bargain.

Kinney of NASA said the agency was merely following the wishes of the astronomical community itself, as expressed in a recent report prepared under the auspices of the National Academy of Sciences. That report listed what would become the Webb telescope, designed to probe early cosmic history when galaxies and stars were first forming, as the highest priority.

"We have to ask, what is the best research for the taxpayer's dollar?" she said.

Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics said in an e-mail message that he thought Hubble was working better than it ever had, "so the equation has changed." He said it would not be easy to decide how best to serve science.

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