This story was updated at 1:36 p.m. EDT.
Two astronauts put the finishing touches on a new six-pack of batteries for the International Space Station Friday during their mission's third and final spacewalk ? one that also sent them to the cargo bay of shuttle Atlantis for the last time.
Astronauts Michael Good and Garrett Reisman spent almost seven hours working in space to finish installing the six new solar array batteries ? each worth $3.6 million ? on the leftmost edge of the space station.
"The station has a new six-pack," NASA commentator Kyle Herring said from Mission Control.
Good and Reisman replaced two of six old solar array batteries during today's spacewalk. Four others were swapped out during a Wednesday excursion. The battery upgrade was one of the major goals for the Atlantis crew's mission as the shuttle flies what is expected to be its final spaceflight before being retired.
NASA wants to make sure the station is as up-to-date on equipment and spare parts before its space shuttle fleet retires. After this flight of Atlantis, which is due to land next Wednesday, May 26, only two more shuttle missions remain.
The nearly complete $100 billion space station, however, is expected to keep flying through at least 2020.
Atlantis up close
Reisman and Good also visited Atlantis' cargo bay for what is expected to be the final time during Friday's spacewalk to retrieve an attachment base for the station's robotic arm that is destined to be installed on the outpost's Russian segment.
Since this is Atlantis' last scheduled mission, today's spacewalk ? or extravehicular activity (EVA) in NASA parlance ? is expected to the last time astronauts work outside this particular shuttle.
"Thanks for being with us these last three EVAs. It was awesome," Reisman said as he thanked Mission Control and his crew's instructor team.
Atlantis pilot Dominic "Tony" Antonelli, who choreographed the spacewalk from inside the shuttle, asked the spacewalkers to pose while he took photos through an orbiter window.
The spacewalkers said they could easily spot their launch pad at NASA's Kennedy Space Center in Florida from space while working in Atlantis' 60-foot (18-meter) payload bay.
"Oh wow, that is cool," Good said. "I can see the [Shuttle Landing Facility]. I can see the two pads."
The astronauts said they could see the runway where plan to land next Wednesday.
"Houston copies, but we'd rather you not land just yet," radioed Mission Control lightheartedly.
Fresh batteries for space station
The new batteries replaced a set of 10-year-old ones that had outlived their designed lifetime on the station's oldest solar array. Another set of six other batteries was replaced last year on an earlier shuttle mission.
The station's batteries store the electricity generated by its expansive solar array. They are big and square ? about 3 feet (almost 1 meter) per side ? and weigh about 375 pounds (170 kg) a piece.
The astronauts also installed a liquid ammonia jumper hose for the station's cooling system among other tasks. They made sure to take time to soak in the view of Earth from space.
"I think I'm right about over the English Channel here," Reisman said as the station sailed over Europe. "Somebody swam that? That seems like a long way."
Friday's spacewalk was the third and final spacewalk Atlantis' STS-132 mission to the International Space Station. In all, the shuttle's three-man spacewalking team, working in pairs, spent 21 hours and 20 minutes outside Atlantis and the station during the three spacewalks this week.
The shuttle launched May 14 on a 12-day mission to deliver the station batteries, a new Russian research module and other spare parts.
For Reisman, the excursion marked his third career, giving him a total of 21 hours and 12 minutes of spacewalking time. It was the fourth overall spacewalk for Good, who ended with 29 hours and 53 minutes.
Friday's spacewalk was also the 146th spacewalk dedicated to space station assembly and maintenance since construction began on the outpost in 1998.
Atlantis' current mission is the 32nd spaceflight for the orbiter and the 132nd shuttle flight since the reusable space plane fleet began flying in 1981. Atlantis has been launching into space since it entered service in 1985.
NASA is retiring its three-orbiter fleet to make way for more ambitious technology and exploration programs aimed at sending astronauts to visit an asteroid and, eventually, Mars.
Atlantis will be prepared to serve as a standby rescue ship in support of NASA's final scheduled shuttle mission (Endeavour's STS-134 flight to launch no earlier than a Nov. 27).
Some members of Congress are lobbying to give Atlantis one final mission as a sendoff, but no funding for extra shuttle flights beyond the two scheduled after this one has been approved, NASA officials have said.
The crew of Atlantis will now prepare to leave the space station. On Saturday, the astronauts will pack a hefty cargo carrier back in the shuttle's cargo bay using the station's robotic arm. The shuttle is due to undock Sunday and land in Florida on Wednesday morning.
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SPACE.com is providing complete coverage of Atlantis' STS-132 mission to the International Space Station with Senior Writer Clara Moskowitz and Managing Editor Tariq Malik based in New York. Click here for shuttle mission updates and a link to NASA TV.