Astronauts Heidemarie Stefanyshyn-Piper (L) and Steve Bowen (R) work during the mission's third spacewalk cleaning and lubricating the International Space Station's starboard Solar Alpha Rotary Joint and replacing trundle bearing assemblies in this view from NASA TV Nov. 22, 2008. Inside the station, the crew continues to transfer equipment between the two spacecraft as ground experts troubleshoot an issue with the station's new Urine Processor Assembly (UPA), part of the system designed to process urine, perspiration and hygiene water into drinkable water.

WASHINGTON, Nov. 22 (Xinhua) -- Two astronauts on the U.S. space shuttle Endeavor completed the third and longest spacewalk of the mission Saturday, nearly wrapping up the lube job on the right-side solar panel joint outside the International Space Station, according to NASA TV.

Spacewalkers Heidemarie Stefanyshyn-Piper and Steve Bowen reentered the Quest airlock at 7:58 p.m. (0058 GMT Sunday). Their excursion was completely devoted to additional cleaning, lubricating and bearing-replacement of the massive, jammed joint.

This balky gear has had limited use since September 2007. The astronauts were told to clean up the metal debris inside the joint, grease the surface and replace the old bearings.

During the repair work, Piper reported finding a larger-than-expected buildup of metal debris. "It wasn't really a blob, it was really more of a pile," she said. Mission Control asked her to take a few photos of the spot before wiping it up with a mitten-like wipe cloth.

During the nearly seven-hour spacewalk, the duo swapped five bearings among a total of 12. Five others were replaced in earlier spacewalks, one was swapped out, and the last one had been cleaned, waiting for replacement during the fourth spacewalk set for Monday, mission managers said.

The solar array joint is a wagon-wheel-shaped joint on the station's truss that allows the electricity-generating solar arrays to rotate so that they always get as much sunshine as possible. U.S. space agency NASA will wait at least until Tuesday to test the gear's rotation to see the effects of their complicated repair.

As a precaution, astronauts will lubricate the left-side joint,which is currently running well, during the fourth spacewalk.

Inside the station, the rest of the shuttle and station crews continued transfers between the two spacecraft Saturday.

Endeavor arrived at the orbital outpost on Nov. 16. It is scheduled to leave on Nov. 27 and land at the Kennedy Space Center in Florida on Nov. 29.