Two NASA astronauts are poised to stepoutside the InternationalSpace Station (ISS) later today to make what will be the first of a seriesof spacewalks to overhaul the orbital laboratory's cooling system.
Clad inU.S. spacesuits, ISS Expedition 14 commanderMichael Lopez-Alegria and flightengineer Sunita Williams are expected to spend more than six hours outside switchinghalf of the cooling lines servicing the space station's Destinylaboratory into their permanent configuration [video].
"I can tellyou that the crew is focused," said Derek Hassman, NASA's lead ISS flightdirector for the extravehicular activity (EVA). "They're very well prepared."
Thespacewalk is due to begin at 10:00 a.m. EST (1500 GMT), with Lopez-Alegria in ared-striped spacesuit while Williams dons an all-white suit. Russiancosmonaut Mikhail Tyurin, a fellow Expedition 14 flight engineer, will helphis crewmates don and doff their spacesuits for today's EVA.
Because oftheir staggered arrival to the ISS, Lopez-Alegria and Williams have notrehearsed today's spacewalk together in its entirety since July 2006, saidHassman. Lopez-Alegria launchedto the ISS in September while Williams arrivedduring last month's STS-116shuttle mission, but both have spent the last few weeks studying up andpracticing elements in simulations aboard the ISS, he added.
Duringtheir primary tasks in today's spacewalk, Lopez-Alegria and Williams will workat 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 andfluid lines, a really tight space full of all kinds of things that you can gethung up on," NASA's lead Expedition 14 spacewalk officer Glenda Laws said of theworksite.
Once there,Lopez-Alegria and Williams will unplug one of two ammonia-fed cooling loopsfrom a temporary set up in 2001, when previous spacewalkers installed theDestiny lab, and then reattach them into a permanent configuration on the spacestation's backbone-like main truss.
Space shuttle astronautsactivated the station's primary cooling system in December during the STS-116mission.
"You canthink of it as a continuation of the work that the [STS-116] crew did on theirmission," Hassman said of today's spacewalk and the next few EVAs.
Today'sspacewalk is the first of three aimed primarily at revamping the space station'scooling system, a vital part of NASA's plan to complete assembly of the ISS by2010.
Anadditional Expedition 14 EVA is scheduled for Feb. 4 to complete the coolingsystem 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 seriesof EVAs planned for ISS astronauts without a visiting space shuttle crew.
The Expedition14 spacewalkers are trained to perform emergency decontamination and clean up proceduresin the event a toxic ammonia leak akin to that whichoccurred when the Destiny module's cooling lines were first installed duringNASA's STS-98mission in 2001.
"That's acontingency that we've worked and we've planned for," Hassman said. "We feel thatwe're ready to address it if it does come."
Laws saidLopez-Alegria and Williams do have a series of additional construction and maintenancetasks on tap for today's spacewalk, as well as some spare chores should theyhave extra time.
"We doexpect them to finish early," Laws said.
The firstof 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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