NASA is moving up the first all-female spacewalk to this week because of a power system failure at the International Space Station.
Astronauts Christina Koch and Jessica Meir will now venture out Thursday or Friday, instead of next Monday, to deal with the problem. It will be the first spacewalk by only women in more than a half-century of spacewalking.
A critical battery power controller failed over the weekend, prompting the change, NASA officials said Monday. The women will replace the broken component, rather than install new batteries, which was their original job.
Last week, astronauts conducted two spacewalks to replace old batteries that make up the station's solar power network. They have three more spacewalks to go to finish the battery work. The next one was supposed to be Wednesday, but it's off for now.
Each of the new lithium-ion batteries needs a device to regulate the amount of charge going in and out. One of these charge regulators did not kick in Friday night, preventing one of the three newly installed batteries from working. Replacing one of these regulators is a generic job for which all potential spacewalkers train, officials said.
The orbiting lab and its six occupants remain safe, according to NASA, and science operations are unaffected.
NASA originally planned an all-female spacewalk last spring, but had to cancel it because of a shortage of readily available medium-size suits. Koch helped assemble an extra medium suit over the summer.
"Very good that we have 4 expert spacewalkers on board to shoulder this tough task. They are the A-team!" tweeted astronaut Anne McClain, who would have gone spacewalking with Koch in March if not for the suit-sizing issue.
Since the first spacewalk in 1965, there have been 227 spacewalkers, only 14 of them women. Meir, who is from Maine, will be making her first spacewalk and become No. 15. All but one of these women has been American.