S122-E-008221 (13 Feb. 2008) --- European Space Agency (ESA) astronaut Hans Schlegel, STS-122 mission specialist, works on the new Columbus laboratory as he 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, Schlegel and NASA astronaut Rex Walheim (out of frame), mission specialist, worked to replace a nitrogen tank used to pressurize the station's ammonia cooling system.