(CNN) — Early Friday, NASA astronauts Chris Cassidy and Robert Behnken began a spacewalk outside of the International Space Station to replace lithium ion batteries for one of the station’s power channels. It is expected to last for about seven hours.
Both astronauts are veteran spacewalkers. This will be Cassidy’s seventh venture outside and Behnken’s eighth. They will conduct a second similar spacewalk on July 1.
Behnken, along with NASA astronaut Doug Hurley, launched from the United States and joined Cassidy on the space station on May 31. They were aboard SpaceX’s Crew Dragon during the Demo-2 mission.
These spacewalks are the culmination of a series of power upgrades that began in January 2017 to replace nickel-hydrogen batteries with new lithium ion batteries. The new batteries arrived last month on a Japanese cargo ship.
These two spacewalks will focus on replacing batteries for one of the power channels on the far starboard truss of the station.