Astronauts in space as NASA extends mission

Houston, June 12: Two astronauts ventured into space today to install a giant new piece on the International Space Station. On a mission NASA will extend to repair a rip in space shuttle Atlantis' heat shield.

Two days and an additional spacewalk will be added to a flight to fix the inches-long tear in an insulating blanket at the back of the shuttle, said deputy shuttle program manager John Shannon.

''It was 100 percent consensus that the unknowns in the engineering analysis and the potential damage ... was not acceptable and we wanted to go and fix it,'' he said in a briefing at Johnson Space Center.

The tear was not thought to be a catastrophic threat to the shuttle, Shannon said, but has nagged at NASA engineers since it was spotted shortly after launch from Florida on Friday.

If not fixed, it could cause heat damage to Atlantis when it returns to Earth on its new landing day, June 21, he said.

Shannon said there appeared to be no other significant problems with the shuttle's heat protection system.

NASA has treated heat shield issues with great caution since Columbia disintegrated during its return home in 2003 after its wing heat shield was damaged at launch by loose insulating foam from the fuel tank.

The seven astronauts on board were killed.

Out in space today, Atlantis astronauts James Reilly and John ''Danny'' Olivas floated out of the space station's airlock at 0138 IST to begin the first of what will now be four spacewalks for the mission.

The shuttle reached the space station, which is slightly more than halfway built and a project of 16 nations, on Sunday after a two-day orbital chase.

They spent much of the day installing on the station a 45-foot-(14-metre) long, 35,678-pound (16,183-kg) metal structure flown up by Atlantis.

The 367 million dollar unit includes a pair of wing-like, electricity-generating solar panels that were scheduled to be unfurled today.

NASA plans to make another 12 trips to the station to haul major components and laboratories before retiring the shuttles in 2010.

The U.S. space agency also would like to make two additional missions to stash spare parts on the outpost and make a final servicing call to the Hubble Space Telescope.

Eventually the station's backbone will span 365 feet (111 metres) and will support four massive U.S.-built solar wings that stretch out 240 feet (73 metres) from end to end.

The last set of panels, which are needed to power partner laboratories built by Europe and Japan, are scheduled to be flown to the station in late 2008 or early 2009.

The station's Russian segments, which include the crew's living quarters, have an independent power system.

Reuters

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