While people back on Earth were celebrating New Year's Eve, a robot aboard the International Space Station (ISS) got on with the job of upgrading the station's solar power system. Under ground control, the Canadian-built Dextre Special Purpose Dexterous Manipulator robot moved on the outside of the orbiting space station, where it started swapping out old batteries dating from 1998 with new lithium-ion versions without the aid of spacewalking astronauts.

According to NASA, the exercise involved removing four old nickel-hydrogen batteries dating from the earliest days of the ISS and replaced them with three new lithium-ion batteries on the 3A power channel Integrated Electronics Assembly (IEA) pallet on the starboard 4 truss. Once the swap was complete, three of the old batteries were stowed on the temporary Japanese H-II Transfer Vehicle's external pallet while the fourth was stored on Dextre's work platform.

Though it looks as if Dextre is putting astronauts out of a job, on Friday, January 6, Expedition 50 Commander Shane Kimbrough and Flight Engineer Peggy Whitson of NASA will conduct spacewalks. In this one, Kimbrough and Whitson will install three adapter plates in slots on the IEA, where three of the dormant and disused old nickel-hydrogen batteries will be temporarily stowed.

After the Friday spacewalk, Dextre will install three more lithium-ion batteries in the 1A power channel IEA of the starboard truss to replace five nickel-hydrogen batteries. Eventually, all 48 of the station's original batteries will be replaced with 24 smaller and more efficient lithium-ion batteries. Meanwhile, when Japan's HTV cargo ship detaches from the ISS later this month, it will have nine of the old batteries stowed aboard, where they will burn up along with the craft when it deorbits over the South Pacific.

The new batteries are a vital part of the four giant solar arrays that power the space station. These panels rotate slowly to face the Sun as the ISS orbits the Earth, feeding electricity into the station's eight electrical buses. When the ISS passes into shadow, the batteries take over and continue to supply the station.

Dextre is a two-armed telemanipulator robot built by Canada's MacDonald Dettwiler (MDA) company and is the third Canadian robotic arm to be installed on the ISS. It was sent to the station in 2008 and entered service in 2011. With a vaguely humanoid appearance, it is equipped with manipulators, sockets for specialized tools, cameras, lights, and umbilicals to provide power, data, and video to payloads.

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