The fate of what some scientists dub "the people's telescope" is again up in the air as NASA decides soon whether to squeeze in a last astronaut repair mission to extend the life of the Hubble Space Telescope.
On Friday, NASA engineers will debate the safety of sending a fifth and final manned space shuttle flight to the 16-year-old telescope, probably in 2008. Soon afterward, NASA Administrator Michael Griffin will make the final call.
His decision could prolong Hubble's ability to capture some of the most spectacular images of the universe well into the next decade or allow the telescope to deteriorate into oblivion by 2009 or 2010.
Griffin worked on Hubble earlier in his career and recently described it as "one of the great scientific instruments of all time." Unlike his predecessor, he has expressed a willingness to repair it.
"If we can do it safely, we want to do it," Griffin said. "But we have new constraints onâ¦ the space shuttle system. We have a new understanding of its fragility and vulnerability."
The final Hubble repair mission was cancelled by former NASA Administrator Sean O'Keefe 2Â½ years ago after the space shuttle Columbia disasterthat killed seven astronauts in 2003. The decision was roundly criticized by scientists and politicians, but O'Keefe cited the risk to astronauts and the need to use the remaining shuttle flights to finish building the International Space Station.
O'Keefe had proposed using a robot to service Hubble, but a scientific advisory panel said the chance of completing such a mission on time was remote and that a manned mission had better odds of succeeding. The committee also said the risks of flying to Hubble were not much greater than going to the space station.
Squeezing in a mission
The primary concern lies with astronaut safety. If the astronauts go to Hubble, they will not be able to seek refuge at the space station should there be a catastrophic problem like the one that doomed Columbia.
"That's a real comfort to know that if you have a problem, you have a place to hang out," said astronaut Joe Tanner, who flew on a Hubble servicing mission in 1997 and was part of the Atlantis crew that flew to the space station last month.
The remaining 14 shuttle flights are dedicated to completing the space station by the time the fleet is grounded in 2010. If a Hubble servicing mission is approved, it would have to be squeezed into the space station construction schedule sometime in early 2008.
NASA also would have another shuttle on the launch pad, ready to make an emergency rescue trip if there were a catastrophic problem.
"I'd tell them to go ahead and do it, but don't grit your teeth," said Howard McCurdy, a space policy expert at American University. "And this is going to be a teeth-gritting mission."
On the list of Hubble repairsis replacement of aging batteries, guidance sensors and gyroscopes.
Among the Hubble's many scientific accomplishments, the telescope has enabled direct observation of the universe as it was 12 billion years ago, discovered black holes at the centre of many galaxies, provided measurements that helped establish the size and age of the universe and offered evidence that the expansion of the universe is accelerating. But the telescope also has popularized astronomy by producing countless wondrous images.
"For many people, it is a symbol of some of the best things about the space program," said Henry Lambright, a space policy expert at Syracuse University. "It reaches the average citizen in the way a lot of space projects, including the space station, do not."