This story was updated at 11:37 a.m. ET.
Astronauts are gearing up for a spacewalk Saturday to prepare a new Japanese research porch to be installed on the space station.
In the first spacewalk of the shuttle Endeavour's STS-127 mission, NASA astronauts Dave Wolf and Tim Kopra are due to step out into space at 11:58 a.m. EDT (1558 GMT). During the planned six-and-a-half hour activity, the two spacewalkers will unberth the porch - a platform to expose science experiments to the space environment - from the shuttle's cargo bay and prepare its attachment site at the station's massive Japanese Kibo laboratory.
"The time critical task that Tim and I will do on the first spacewalk of the mission, Day 4, is to get that exposed facility, the Japanese 'Jeff' exposed facility, ready to be unberthed robotically out of the payload bay," Wolf said in a preflight interview. "This is a choreography between the spacewalk crew, of course the ground and the robotics arm operators."
The two spacewalkers began preparing for today's event by camping out in the station's Quest airlock overnight, where the pressure was lowered to prepare their bodies for wearing the spacesuits today.
Wolf, a veteran astronaut with four spacewalks under his belt, will wear a spacesuit marked with a red stripe. Kopra, making his spacewalking debut, will wear an all-white suit.
"I'm really excited," Kopra said of his first spacewalk experience. "It's going to be great. You know, both doing the spacewalk and being able to work the robotic arms on space station are very exciting components of our mission for, for astronauts, and I think that?s going to be quite an event."
While those two are working outside, shuttle commander Mark Polansky, pilot Doug Hurley and mission specialists Julie Payette and Koichi Wakata will operate the shuttle and station robotic arms to transfer the Japanese Exposed Facility to its new home on Kibo.
"I'm amazed by the operations team and the crew and the complexity of the missions we're operating now," NASA shuttle program manager John Shannon said Friday. "The robotics required to support those spacewalks is as complicated as we've ever done. We are very excited to get this flight kicked off."
The two spacewalkers will also work to deploy two spare part platforms on the station's backbone-like truss. The platforms serve as a sort of exposed storage shed for vital station spare parts.
One of the platforms was previously attached during the STS-119 shuttle mission in March, but a jammed pin kept the platform from unfolding as it was meant to. Wolf and Kopra will give it another try today.
Endeavour astronauts plan to perform five tricky spacewalks during their mission. This trip is only the second time that so many spacewalks will be conducted on a space station shuttle mission.
The space shuttle docked at the International Space Station Friday to begin a two-week visit, boosting the population onboard the orbital outpost to a record high of 13. Endeavour launched July 15 after more than a month of delays on the ground.
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SPACE.com is providing continuous coverage of STS-127 with reporter Clara Moskowitz and senior editor Tariq Malik in New York. Click here for mission updates and SPACE.com's live NASA TV video feed.