Two astronauts are spacewalking Wednesday to replace batteries on the international space station, the National Aeronautics and Space Administration (NASA) said. The two astronauts left the station earlier on Wednesday for the third spacewalk in five days for the crew of space shuttle Endeavour. The spacewalkers will remove four old batteries from a solar-panel electrical assembly and plug in new ones that were brought by Endeavour. They are nickel-hydrogen batteries that weigh 168 kilograms (370 pounds) each. Two other batteries will be replaced on Friday. Endeavour's astronauts have been in orbit for a week and are scheduled to remain at the space station until Tuesday.
