ISS Astronauts Set for Sunday Spacewalk

Astronaut Sunita Williams, Expedition 14 flight engineer, uses a pistol grip tool (PGT) as she participates in the first of three sessions of extravehicular activity (EVA) in nine days, as construction continues on the International Space Station on Jan. 31, 2007. CREDIT: NASA.

Astronauts aboard the International Space Station (ISS) have a long Super Bowl Sunday ahead as they prepare to venture outside the orbital laboratory for their second spacewalk in less than a week.

Expedition 14 commander Michael Lopez-Alegria and flight engineer Sunita Williams are expected to once more don their NASA spacesuits and begin the second of three planned spacewalks in nine days Sunday at 9:00 a.m. EST (1400 GMT) [image]. Their goal: the completion of an ISS cooling system overhaul that began during a nearly eight-hour excursion on Wednesday [video].

"That's Super Bowl Sunday," said Glenda Laws, NASA's lead Expedition 14 extravehicular activity (EVA) officer, of tomorrow's spacewalk. "We'll get that EVA out of the way though in plenty of time for everyone to watch the football game afterwards."

Laws said that the Expedition 14 spacewalkers will again take great care while handling ISS cooling lines to avoid leaks of the station's toxic ammonia coolant.

Lopez-Alegria and Williams are performing an unprecedented three EVAs in two weeks, and expect to spend around six hours working outside the ISS on Sunday. Lopez-Alegria is also expected to make a fourth, unrelated spacewalk on Feb. 22 with Russian cosmonaut and flight engineer Mikhail Tyurin.

The spacewalk marathon marks the most densely-packed series of EVAs without a visiting NASA space shuttle crew. Shuttle astronauts routinely make several spacewalks within days of one another while docked at the ISS on relatively short missions. But fatigue and wear are larger concerns for the long-duration astronauts assigned to station Expedition crews, NASA officials said.

During the Expedition 14 crew's spacewalk quartet, the astronauts are routinely discussing their energy levels and personal health with flight surgeons on Earth, mission managers said.

"The health of the crew, the stamina of the crew is something that we watch very closely," Derek Hassmann, NASA's lead ISS Expedition 14 EVA flight director, said after the Jan. 31 spacewalk.

Cooling system work awaits

Clad in bulky NASA spacesuits, Lopez-Alegria and Williams duties on Sunday are mostly a mirror image of their previous Jan. 31 spacewalk. As in that excursion, Lopez-Alegria will sport a spacesuit marked with red stripes while Williams' spacesuit will be white with no stripes [image].

"We're hoping that with everything that we learned about body positions and so on...that we'll be able to move through the operations on the [cooling] loop reconfig will go a bit smoother next time," Laws said.

During their Wednesday spacewalk, Lopez-Alegria and Williams switched the space station's Loop A cooling system from a temporary set up - which shed heat from a radiator on the outpost's mast-like Port 6 truss - to a permanent configuration that runs through heat exchangers in the station's U.S. Destiny module. On Sunday, the spacewalkers will tackle the second half of that cooling system, Loop B, while taking care to avoid any leaks of toxic ammonia coolant in a worksite renown for its tight squeezes and "Rat's Nest" of electrical and plumbing lines [image].

Once the cooling system work is complete, the Expedition 14 spacewalkers will watch over the remote-controlled retraction an aft-facing radiator on the Port 6 truss that is no longer required [image].

The astronauts also plan to retrieve the second of two fluid lines on an unneeded reservoir filled with ammonia coolant, photograph a solar array extending to starboard from the Port 6 truss, and wire up a power transfer system that will allow future NASA space shuttles to spend more time docked at the ISS by drawing on the outpost's power supply.

If any spare time remains, the spacewalkers could perform extra tasks -- known as get aheads -- which include taking snapshots of the station's shuttle docking port to determine if any corrosion or debris is responsible for spotty communication links between the ISS and visiting orbiters during recent NASA shuttle missions. But Laws stressed that completing the spacewalk's primary chores remain the Expedition 14 crew's top priority.

"We'll take our time, we'll do what it takes," Laws said after the Jan. 31 spacewalk. "We'll get to the get aheads when we get to the get aheads."

Sunday's planned Expedition 14 spacewalk is scheduled to begin at 9:00 a.m. EST (1400 GMT). NASA will begin broadcasting the space station crew's spacewalk activities live on NASA TV at 8:00 a.m. EST (1300 GMT).

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