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S122-E-008323 (13 Feb. 2008) --- Astronaut Rex Walheim, STS-122 mission specialist, participates in the mission's second scheduled session of extravehicular activity (EVA) as construction and maintenance continue on the International Space Station. During the six-hour, 45-minute spacewalk, among other tasks, Walheim and European Space Agency (ESA) astronaut Hans Schlegel (out of frame), mission specialist, worked to replace a nitrogen tank used to pressurize the station's ammonia cooling system.
