NASA, in collaboration with the European Space Agency (ESA), is undertaking a spacewalk to change a battery on the International Space Station. On Friday, Expedition 50 commander Shane Kimbrough joined ESA flight engineer Thomas Pesquet at 7.44 a.m. E.T. to begin a battery upgrade, replacing the older nickel hydrogen batteries in the outpost power system with lithium-ion ones.

The event is Pesquet’s first spacewalk, and is expected to last the standard six and a half hours. Prior to the walk, astronauts need to undertake around four hours of preparation, including safety checks and suiting up.

It’s the second battery replacement spacewalk this month. The first was conducted on January 6 by Kimbrough and NASA flight engineer Peggy Whitson. The walk was aimed at hooking up three new lithium-ion batteries delivered to the station on December 13 by a Japanese H-II Transfer Vehicle cargo ship. Also known as the “white stork” and the “golden treasure box,” the ship has the largest loading capacity in the world, at around six metric tons.

The team undertook some preliminary preparation for Friday’s walk with the help of a robot friend. The Dextre Special Purpose Dexterous Manipulator, operated by ground controllers, moved around the older nickel hydrogen batteries, so most of the team’s mission involves hooking up the batteries.

Kimbrough has red stripes on his suit, while Pesquet’s suit has no stripes.

Watch the event live here.

Photos via NASA