The second spacewalk in history to be conducted entirely by female astronauts got underway at the International Space Station on Wednesday morning.

NASA astronauts Jessica Meir and Christina Koch are scheduled to replace batteries on solar arrays on the outside of the International Space Station during the first spacewalk of 2020.

They are the same astronauts who made history after successfully completing the very first all-female spacewalk in October. That came months after a planned spacewalk with an all-women crew had to be canceled in March because of a lack of suitable spacesuits.

NASA said that Meir and Koch would be replacing nickel-hydrogen batteries with new lithium-ion batteries that store power generated by the solar arrays on the ISS’s port truss. They are scheduled to conduct a second spacewalk on Monday to finish the battery replacement.

These will be the second and third spacewalks for Meir and the fifth and sixth for Koch.

If the battery replacement work goes as planned, NASA astronaut Andrew Morgan and space station Commander Luca Parmitano from the European Space Agency will exit the station January 25, to finish installing the Alpha Magnetic Spectrometer’s (AMS) new cooling apparatus and lines begun in November and December, and verify they are ready for use.

The spectrometer is searching for dark matter and antimatter in the universe.

NASA said Wednesday’s spacewalk is the 225th conducted at the International Space Station.