| BEIJING, Nov. 2 (Xinhuanet) -- If a U.S. space shuttle lifts off headed for the Hubble Space Telescope as early as May 2008, it will be the heaviest mission ever launched (22,000 pounds of gear and hardware) and the most complex -- requiring spacewalking astronauts to remove 111 screws in 45 minutes to replace a spectograph. And that is just the fourth of five spacewalks required to repair and upgrade the telescope to six working instruments for the first time since 1993. The scheduled overhaul would add about five years to Hubble's life and enable it to perform science until at least 2013. Hubble chief scientist David Leckrone said astronaut training to replace the electronics board in the Space Telescope Imaging Spectrograph (STIS) may include watching NASCAR pit crews in action. STIS was installed in 1997 and quit operating in 2004. "We envision a NASCAR wheel-changing operation," he said. The mission had been cancelled in 2004 because of safety risks to the shuttle crew. But NASA has since flown three shuttle flights and decided to proceed with the servicing mission after all. "I didn't fully believe it until I heard the words come out of the administrator's mouth this morning (Tuesday) at the press conference," said Scott Altman, who commanded the most recent servicing mission to Hubble in 2002 and will also lead the upcoming mission. The mission is scheduled to last 11 days, but Discovery could stay in space for 25 days to wait for a rescue shuttle if it is damaged and cannot be repaired in orbit. The rescue shuttle will be on the other shuttle launch pad when Discovery lifts off. It would come near the ailing shuttle in space and the two would be joined by their robotic arms to allow Discovery's crew to transfer. But aside from the risks of such a rescue, having seven people in the cramped quarters of the shuttle for 25 days would be a challenge in itself. During his previous Hubble shuttle flight, Altman said he looked forward to sending two astronauts on spacewalks because it gave the other astronauts a little more breathing room. "It was always with a little bit of reluctance that we let them back in," Altman joked. Because the shuttle is already so cramped, NASA chief Mike Griffin decided not to take up a 'de-orbit' module that would steer the telescope to a crash landing in an unpopulated area sometime after 2025. "I was the one who took the de-orbit module off of this mission because I thought it was idiotic," he said, explaining that the weight saved allowed more science instruments to be taken up. Instead, Discovery will install a device that will allow other spacecraft, including the shuttle's successor, the Crew Exploration Vehicle, to grab onto it. That way, the telescope could either be upgraded once again or de-orbited.
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