STS-135 crew members Rex Walheim and Sandra Magnus during EVA TPS OPS at 1G Trainer at the NBL.

JSC2011-E-029049 (21 March 2011) --- NASA astronaut Rex Walheim (foreground), STS-135 mission specialist, participates in an extravehicular activity (EVA) hardware training session in the Neutral Buoyancy Laboratory (NBL) near NASA's Johnson Space Center. EVA instructor Art Thomason assisted Walheim. STS-135 is planned to be the final mission of the space shuttle program. Photo credit: NASA or National Aeronautics and Space Administration