Spacewalking astronauts stashed an inspection boom to the outside of the International Space Station on Saturday to assure the next shuttle crew can scrutinize their ship for damage.
Typically, crews carry their own inspection gear to and from orbit, but the next load coming up to the station is so big there is no room in the shuttle for the sensor-studded 50-foot (15-metre) boom needed to check for heat shield damage.
Instead, the shuttle Discovery crew, which is expected to blast off on May 25 with Japan's 37-foot-long (11-metre-long) Kibo laboratory, will retrieve the boom from its temporary storage location on the outside of the station.
NASA has been flying the scanners since resuming flights after the fatal 2003 Columbia accident, which was triggered by undetected damage to the ship's wing.
Latching the boom to the outside of the station was the primary task of the fifth and final spacewalk conducted by the shuttle Endeavour crew, which arrived at the station on March 12.
During previous outings, astronauts installed a storage closet for Japan's Kibo complex and assembled a Canadian-built maintenance robot.
"I think you guys did a fantastic job and did even more than we expected out of the day," astronaut Richard Linnehan, who oversaw Saturday's spacewalk from inside Endeavour, told crewmates Robert Behnken and Michael Foreman, who wrapped up a six-hour outing at about 10:30 p.m. EDT (0230 GMT on Sunday).
Keeping sensors warm
Working well ahead of schedule throughout the spacewalk, Behnken and Foreman hooked up a power cord to keep the boom's delicate sensors warm during the planned two-month stay in orbit and then latched the ends of the pole into place along a piece of the station's truss.
After the beam slipped into position, the spacewalkers split up to tackle a handful of maintenance chores, including pinning a science experiment onto a fixture outside Europe's Columbus module. Astronauts had tried to attach the briefcase-sized experiment case during a spacewalk on Monday but were stymied by a misfit pin.
Behnken used a small hammer to knock the pins in place.
While Behnken worked with the science experiment, Foreman inspected a contaminated joint needed to rotate one of the station's solar panel wings. NASA last year discovered metal shavings inside the mechanism and is trying to trace the source of the contamination.
The wing has been locked in position to avoid damaging the joint further.
Foreman found rough patches, but no obvious sign of an orbital debris impact, which is one possible cause of the problem.
The power lost by clipping the wing in place, which prevents is from tracking the sun for power, 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 on Wednesday.