On Wednesday, July 1, NASA astronauts Chris Cassidy and Robert Behnken will begin the 229th spacewalk in support of space station assembly, maintenance and upgrades. Astronauts Cassidy and Behnken will exit the station’s Quest airlock to replace aging nickel-hydrogen batteries for one of two power channels on the far starboard truss with new lithium-ion batteries that arrived on a Japanese cargo spacecraft last month. The spacewalk will begin at around 11:35 UTC, with an expected duration of 7 hours.