Discovery spacewalker Danny Olivas at work during the STS-128 mission’s first spacewalk. During the six-hour, 35-minute spacewalk, Olivas and astronaut Nicole Stott, removed an empty ammonia tank from the station’s truss and temporarily stowed it on the station’s robotic arm. Olivas and Stott also retrieved the European Technology Exposure Facility and Materials International Space Station Experiment from the Columbus laboratory module and installed them on Discovery’s payload bay for return. Credit: NASA