Two astronauts completed a second of four scheduled space walks of the Endeavour shuttle's final mission to the International Space Station on Sunday, the US space agency said.
Drew Feustel and Mike Fincke wrapped up their eight-hour, seven-minute spacewalk at 1412 GMT after refilling radiators with ammonia, installing stowage beams near the middle of the main truss, lubricating a solar panel joint and parts of Dextre, one of the orbiting station's robotic arms.
Endeavour Mission Specialist Greg Chamitoff, who participated in the first spacewalk of the mission, coordinated communications between the spacewalkers and mission control in Houston and choreographed their activities from inside the ISS, according to NASA officials.
Greg Johnson and Expedition 27 crew member Cady Coleman operated the space shuttle and space station robotic arms in the later portion of the spacewalk.
During their first task, the spacewalking astronauts rerouted an ammonia jumper cable between cooling loops on port-side truss segments.
They then topped off off ammonia in a slowly leaking cooling loop.
Fincke later removed covers over the port solar alpha rotary joint, which allows the solar arrays to track the sun, in order to lubricate its race ring.
After a bolt holding the covers was lost, mission control ordered him to remove four of the covers instead of six as had been initially planned.
Flight controllers partially rotated the joint to spread the lubricant after Fincke completed the first of two planned lubrications of the race ring.
Feustel installed a camera cover on Dextre, operated remotely by Johnson and Coleman, and lubricated one of the Canadian robot's arms.
Coleman was working on her last full day at the ISS before her scheduled return to Earth on Monday with other Expedition 27 crewmembers.
Fincke installed two radiator grapple bar stowage beams on a truss segment before giving the solar array joint a second round of lubrication with Feustel.
The pair reinstalled three of the four joint covers, with the fourth due to be installed later.
Johnson put in around three hours of stowage, while Mission Specialist Roberto Vittori spent much of the afternoon transferring supplies and equipment between Endeavour and the station and stowage area.
The spacewalk was Feustel's fifth and the seventh for Fincke, the 157th in support of space station assembly and maintenance and the 246th conducted by US astronauts.
Endeavour blasted off on its final mission Monday with six astronauts on board -- five Americans and one Italian -- and docked at the ISS on Wednesday.
The Endeavour mission is being commanded by astronaut Mark Kelly, the husband of US Representative Gabrielle Giffords, who is recovering after being shot in the head at a January political meeting with local voters.
The shuttle will remain at the space station until May 30, returning to the United States on June 1.
The 30-year US space shuttle program formally ends later this year with the flight of Atlantis, leaving Russia's space capsules as the sole option for world astronauts heading to and from the orbiting research lab.
Explore further: Endeavour crew starts work at space station: NASA (Update)