CAPE CANAVERAL, Fla. (AP) – Astronauts making the last spacewalk of NASA's space shuttle era on Tuesday retrieved a broken pump from the International Space Station and installed a fill-er-up experiment for a robot.The space station's two-armed robot Dextre won't tackle the $22.6 million playset – a fancy Fisher-Price toy as one astronaut describes it – until long after Atlantis departs and the shuttle program ends.But perhaps more than anything else on this final journey by a shuttle, the robotic demo illustrates the possibilities ahead for NASA: satellite-refueling stations in space run by robots.In a departure from previous shuttle visits, the spacewalking job fell to space station astronauts, Michael Fossum and Ronald Garan Jr., who teamed up for three spacewalks in 2008. The four-person Atlantis crew is the smallest in decades, and so the lone spacewalk of the mission was handed over to the full-time station residents.It was the 160th spacewalk in the 12-1/2-year life of the orbiting outpost, and the last one planned for Americans for more than a year."To see that we've really done it, it's just awe-inspiring," Fossum said of the completed space station and all the spacewalks that went into it. "Ron and I are honored to be a part of it, to help close out one of the final chapters."Fossum and Garan completed the two major chores – the pump removal and robotic test hookup – in just over 3 hours.