Mission to Save Hubble Could Launch a Day Early

This story was updated at 2:00 p.m. EDT.

WASHINGTON - NASA ishoping to launch the space shuttle Atlantis on the last service call to theHubble Space Telescope a day earlier than planned to avoid schedule conflictsnear its Florida launch site, agency officials said Thursday.

The long-delayedHubble repair flight, which mission managers have now found to be lessrisky than initially thought, would lift off on May 11 at 2:01 p.m. EDT (1801GMT) if the earlier target is approved next week.

?I feelfairly confident that we can make a May 11 launch date,? said LeRoy Cain,NASA?s deputy shuttle program manager, during a series of mission briefings.Cain added that after further study, the riskof damage to Atlantis from space debris has fallen within tolerable limits.

Top NASAofficials will decide whether Atlantis and its crew of seven astronauts will beready to launch early. The mission was previouslyslated to launch on May 12 from NASA?s Kennedy Space Center in CapeCanaveral, Fla.

Launchdate shuffle

Veteranshuttle commander Scott Altman and his Atlantis crew initially planned tolaunch toward Hubble in October 2008, but NASA postponed theflight after a serious glitch popped up aboard the space telescope. The astronauts plan to perform fiveback-to-back spacewalks to install new instruments and make vital repairs toHubble, which celebrates its 19th birthday tomorrow. The upgrades are expectedto extend the space telescope?s operational life through at least 2014.

Cain toldreporters that by targeting an earlier liftoff, Atlantis would have at leasttwo more chances to launch on May 12 and May 13 before standing down due to aplanned military operation at the nearby Cape Canaveral Air Force Station.

If Atlantiscannot launch by May 13, NASA would have wait until May 22 to try again, Cainsaid.

PrestonBurch, NASA?s Hubble project manager, said engineers are working around theclock to pack Atlantis with the new instruments, tools and other gear tosupport the five spacewalks on tap to upgrade Hubble. But only time will tellif they can finish in time for May 11, he added.

?Everythingreally needs to go our way in terms of completing our installations andhookups,? Burch said. ?Really, our primarily goal is to get it right, to makesure we don?t mess anything up.?

Spacedebris risk revealed

NASAofficials initially said that Atlantis and its crew would face a higher thannormal risk of damage from space debris, about a 1-in-185 chance, because theshuttle must fly in a higher orbit than the International Space Station toreach the Hubble Space Telescope. Hubble orbits the Earth at about 300 miles (482km), while the space station flies about 220 miles (354 km) above the planet.

NASAguidelines call for no more than a 1-in-200 chance of damage from debris. Aftermore study, Cain said Thursday that NASA believes the risk to Atlantis islower, about a 1-in-221 chance, and within acceptable limits. Atlantis willalso be moved to a lower orbit soon after its crew releases Hubble back intospace in a move to further reduce the risk, he added.

Atlantisalso has another backup, the space shuttle Endeavour, which is currentlyperched atop a second launch pad and standing by to serve as a rescue ship ifneeded.

BecauseHubble flies in a higher orbit and different orbital inclination than theInternational Space Station, Atlantis astronauts will not be able to seekrefuge aboard the orbital laboratory like recent station-bound shuttle crews. Instead,NASA has primed Endeavour and a skeleton astronaut crew to launch arescue flight and retrieveAtlantis? crew within 25 days of an emergency.

Shuttleflight director Tony Ceccacci told reporters that NASA is confident it will notneed any such rescue mission, but will keep Endeavour and its four-man crew onstandby ?just in case.?

• New Video - Hubble Crew?s Rescue Mission Plan
• New Show: Hubble's Universe: The Final Shuttle Service Call
• Image Gallery - Hubble Photos: When Galaxies Collide