CAPE CANAVERAL, Fla. The last spacewalk of NASA's space shuttle era is under way nearly 250 miles above Earth.
Space station astronauts Michael Fossum and Ronald Garan Jr. ventured out Tuesday morning.
They'll retrieve a broken ammonia pump outside the International Space Station and pack it aboard the docked shuttle Atlantis. NASA wants the pump brought back so engineers can figure out why it failed last summer. The two will also set up a robotic refueling experiment.
Only four astronauts are flying Atlantis. It's the smallest crew in decades — too small, in fact, to have had time to train for this spacewalk. That's why the job was handed over to the space station crew.
The 13-day flight by Atlantis is the last for the shuttle program.