Two of Discovery’s astronauts set out on their second spacewalk in three days early Monday, with the focus this time on the space station, not the shuttle.
According to BBC, Soichi Noguchi and Steve Robinson will open the airlock hatch and step into the void at about 0914 GMT (1014 BST).
Their main objective during the walk will be to remove and replace a failed control moment gyroscope on the International Space Station (ISS).
The orbiting platform has three gyroscopes that maintain its proper position relative to Earth.
Working together 370km (230 miles) above Earth, Noguchi and Robinson will remove control moment gyroscope (CMG) number one from its truss on the ISS.
Each CMG weighs 300kg (660lbs) and is about the size of a washing machine. The station currently needs only two of them to control its "attitude", or orientation, toward Earth; the third is there as back-up.
But if another were to fail, the ISS would need to use thrusters on the Russian section of the station to stop itself from becoming lopsided.
Shuttle managers are still deciding whether to send an astronaut to Discovery's underside to deal with material, or gap filler, that is sticking out between tiles in two places on the orbiter's underside.
"We have a team of folks working aggressively to go and make that gap filler safe if we decide it's an issue. We have a separate team looking at the effects of leaving that gap filler protruding," mission flight director Paul Hill was quoted as saying by BBC on Sunday.
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