ISS Astronauts Poised for Wednesday Spacewalk

Two NASA astronauts are poised to step outside the International Space Station (ISS) later today to make what will be the first of a series of spacewalks to overhaul the orbital laboratory's cooling system.

Clad in U.S. spacesuits, ISS Expedition 14 commander Michael Lopez-Alegria and flight engineer Sunita Williams are expected to spend more than six hours outside switching half of the cooling lines servicing the space station's Destiny laboratory into their permanent configuration [video].

"I can tell you that the crew is focused," said Derek Hassman, NASA's lead ISS flight director for the extravehicular activity (EVA). "They're very well prepared."

The spacewalk is due to begin at 10:00 a.m. EST (1500 GMT), with Lopez-Alegria in a red-striped spacesuit while Williams dons an all-white suit. Russian cosmonaut Mikhail Tyurin, a fellow Expedition 14 flight engineer, will help his crewmates don and doff their spacesuits for today's EVA.

Because of their staggered arrival to the ISS, Lopez-Alegria and Williams have not rehearsed today's spacewalk together in its entirety since July 2006, said Hassman. Lopez-Alegria launched to the ISS in September while Williams arrived during last month's STS-116 shuttle mission, but both have spent the last few weeks studying up and practicing elements in simulations aboard the ISS, he added.

During their primary tasks in today's spacewalk, Lopez-Alegria and Williams will work at a site on the space station's central Z1 truss -- known as the "Rat's Nest" -- that serves as a sort of hub for electrical and thermal control lines [image].

"It's full of cables and fluid lines, a really tight space full of all kinds of things that you can get hung up on," NASA's lead Expedition 14 spacewalk officer Glenda Laws said of the worksite.

Once there, Lopez-Alegria and Williams will unplug one of two ammonia-fed cooling loops from a temporary set up in 2001, when previous spacewalkers installed the Destiny lab, and then reattach them into a permanent configuration on the space station's backbone-like main truss.

Space shuttle astronauts activated the station's primary cooling system in December during the STS-116 mission.

"You can think of it as a continuation of the work that the [STS-116] crew did on their mission," Hassman said of today's spacewalk and the next few EVAs.

Today's spacewalk is the first of three aimed primarily at revamping the space station's cooling system, a vital part of NASA's plan to complete assembly of the ISS by 2010.

An additional Expedition 14 EVA is scheduled for Feb. 4 to complete the cooling system work. A third is set for Feb. 8 to be followed by a fourth, Russian-controlled spacewalk slated for Feb. 22 to complete the densest series of EVAs planned for ISS astronauts without a visiting space shuttle crew.

The Expedition 14 spacewalkers are trained to perform emergency decontamination and clean up procedures in the event a toxic ammonia leak akin to that which occurred when the Destiny module's cooling lines were first installed during NASA's STS-98 mission in 2001.

"That's a contingency that we've worked and we've planned for," Hassman said. "We feel that we're ready to address it if it does come."

Laws said Lopez-Alegria and Williams do have a series of additional construction and maintenance tasks on tap for today's spacewalk, as well as some spare chores should they have extra time.

"We do expect them to finish early," Laws said.

The first of the upcoming four Expedition 14 spacewalks is scheduled begin at 10:00 am. EST (1500 GMT) on Wednesday, Jan. 31 and will be broadcast live on NASA TV.

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