The NASA “astrosisters” were congratulated on the historic achievement by fellow astronaut Andrew Morgan. Astronauts on the ISS have to date completed a total of 220 service missions in the vacuum of space. Today’s spacewalk, however, marks the first all-woman crew to work on the space station.
Mr Morgan, who joined NASA’s astronaut class of 2013 alongside Mrs Koch and Ms Meir, congratulated his colleagues online.
The astronaut tweeted from space: “So proud of my astrosisters @Astro_Christina and @Astro_Jessica!
“We’ve been training together since our selection in 2013, and now they’re out on a history-making spacewalk! #AllWomanSpacewalk”
Watch the incredible moment both astronauts leave the ISS in the video above.
READ MORE: NASA’s best pictures of Earth from the International Space Station
NASA said: ‘The astronauts will replace a battery charge/discharge unit that failed to activate after new lithium-ion batteries were installed on the space station’s exterior structure on October 11.
Ms Meir, however, is experiencing the vacuum of space for the very first time.
NASA said: “The all-woman spacewalk wasn’t something we purposefully planned, though.
“It was bound to happen eventually because of the increasing number of female astronauts.
“Koch’s and Meir’s 2013 class of astronaut candidates was 50 percent women.”