Shuttle Endeavour astronauts embark on final spacewalk

HOUSTON -- Two shuttle Endeavour astronauts floated outside the International Space Station on Saturday to stow an inspection boom for the next shuttle crew and hook up a science experiment that bedeviled spacewalkers on a previous outing.

Clad in bulky, life-sustaining spacesuits, Robert Behnken and Michael Foreman opened the hatch from the station's airlock at about 3:30 p.m. to begin the fifth and final spacewalk of Endeavour's station construction and servicing mission.

The shuttle and seven astronauts arrived March 12 to deliver a storage room for Japan's upcoming Kibo laboratory and assemble a Canadian-built maintenance robot.

The first task of the 6.5-hour outing was to hook up an extension cord for heaters to keep sensors and cameras on a critical inspection boom warm for the next two months.

Typically, the 50-foot boom, which the crew uses to inspect their ship's heat shield for damage, rides to and from space on the shuttle. But the next load of cargo coming to the station is so big, there is no room for the boom.

Instead, the shuttle Discovery crew, which is expected to blast off May 25 with the tour bus-sized Kibo lab, will retrieve the boom from its temporary storage location on the outside of the station.

The boom, which is tipped with lasers, has been used by all shuttle crews since flights resumed after the 2003 Columbia disaster. Columbia disintegrated while returning to Earth because of undetected heat shield damage. All seven astronauts on board were killed.

CHORES

Once the boom is safely latched into place, Behnken and Foreman will tackle a variety of chores, including a second attempt to pin a case of sample materials onto a fixture outside Europe's Columbus laboratory. The first attempt during a spacewalk Monday was stymied by a misfit pin.

During Saturday's outing, Behnken had a variety of pins and tools to attach the briefcase-sized box. It is scheduled to stay outside the station for about a year to expose the sample materials to the harsh space environment.

NASA also wants Foreman to inspect a contaminated joint needed to rotate one of the station's solar wing panels like a Ferris wheel to track the sun for power.

The wing has been locked in position to avoid damaging the joint further. During earlier inspections, metal shavings were discovered inside the mechanism.

Engineers want to have a closer look at a small pitted area to determine if an orbital debris impact may be to blame for the problems.

The power loss by clipping the wing in place is not expected to affect station operations until next year when the crew size is scheduled to double to six members. NASA hopes to fix the problem well before then.

The space agency has 10 more construction and resupply flights to the station before the shuttles are retired in two years. A final mission to upgrade the Hubble Space Telescope later this year also is scheduled.

Endeavour is scheduled to end its 16-day spaceflight with a landing at the Kennedy Space Center in Florida Wednesday.

(Editing by Sandra Maler)

REUTERS