Astronauts have left the station on numerous occasions to work in space, including to replace the nickel-hydrogen batteries with new lithium-ion batteries.

American astronauts Chris Cassidy and Bob Behnken from ISS Expedition 63 perform a spacewalk outside the station as they plan to upgrade its power system. The operation is expected to last seven hours and will be the final part of the 3.5-year-long ISS power system modernisation.

Cassidy, who is currently the head of the expedition, arrived on the ISS at the beginning of April as part of the Soyuz MS-16 space mission, while Behnken recently joined the crew on board the first space flight from US soil since 2011, launched by NASA and SpaceX.