Astronauts venture out for work on space station

CAPE CANAVERAL, Florida (Reuters) - A pair of high-tech construction workers ventured outside the International Space Station on Monday to hook up electrical connections on a massive girder that holds new solar panels needed to boost power on the orbital outpost.

Astronauts James Reilly and John "Danny" Olivas floated outside the space station's airlock at 4:08 p.m. EDT (2008 GMT) to begin the first of three outings planned during space shuttle Atlantis' week-long visit.

A fourth spacewalk may take place to repair a tear in Atlantis' heat protection system.

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.

Before Reilly and Olivas left the station, crewmates used its Canadian-built robot arm and computerized vision system to gently lower the new 45-foot-(14-metre) long, 35,678-pound (16,183-kg) metal structure into place on the starboard, or right-hand, side of the station. Automated latches and bolts then anchored the $367 million addition permanently in place.

The installation restored some symmetry to the $100 billion outpost, which was built up on its port side first. 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 meters) and will support four massive U.S.-built solar wings that stretch out 240 feet 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.

Reilly and Olivas were expected to spend about 6.5 hours spacewalking on Monday to hook up power cables on the new beam and opening latches and restraints so that the twin solar panels folded up inside can be unfurled on Tuesday.

THERMAL BLANKET DAMAGE

Atlantis' crew is scheduled to perform two more spacewalks to retract an old solar array and possibly repair a thermal blanket that peeled back slightly during Friday's launch.

The blanket protrusion exposed a few inches of underlying layers of the shuttle, which could lead to damage during the heat of re-entry, deputy shuttle manager John Shannon said.

He said the size and location of the problem meant any damage would not be catastrophic, but would require repair once Atlantis returns from its scheduled 11-day mission.

"I would just like to avoid that scenario altogether and tuck that blanket back down," Shannon said.

Fixing the blanket would be a simple chore that could be incorporated if time permits into the third spacewalk, scheduled for Friday. If not, it would mean a fourth spacewalk.

The shuttle Columbia disintegrated while returning to Earth in 2003 because of a break in the heat shield on its wing, caused by insulating foam flying off the fuel tank at takeoff. The seven astronauts on board were killed and NASA has since approached heat shield problems with great caution.

NASA said there appeared to be no other heat shield issues on Atlantis, save for a gap filler on the shuttle belly that photographs taken from the station showed protruding about three-quarters of an inch.