NBC NEWS — Two astronauts made history Friday morning as the first women to participate in an all-female spacewalk.
They will replace a faulty battery charge/discharge unit (BCDU) that failed to activate earlier this month when new lithium-ion batteries were installed on the station's exterior, according to NASA.
The discharge units regulate the amount of charge batteries collect from solar arrays while the station orbits Earth at nighttime, providing increased power, NASA says the failure has not affected station operations or crew safety. Still, NASA pushed the planned repair up from Oct. 21 to Friday.
NASA noted the "historical significance of the event."
NASA astronauts Jessica Meir, left, and Christina Koch are inside the Quest airlock preparing the U.S. spacesuits and tools they will use on their first spacewalk together on the International Space Station. NASA had planned an all-female spacewalk in March, but that event — which was to have involved Koch and NASA astronaut Anne McClain — was scrapped because there weren’t enough spacesuits of the right size available on the station.
NASA was criticized for not having enough uniforms for two women to participate in a spacewalk together.
It is Meir's first spacewalk and Koch's fourth, according to NASA. Both are on their first spaceflight after the were selected as astronaut candidates in 2013, as part of a class that was 50 percent women.
NASA plans to put the first woman on the moon by 2024.
Meir will be the 15th woman to spacewalk. Forty-three spacewalks have included a woman since 1984, when a Russian cosmonaut spacewalked in July of that year and a NASA astronaut did in October.
The all-female spacewalk will be the second of what NASA has called a “spacewalk bonanza,” with 10 outings scheduled through December.