It's the last spacewalk of the shuttle era. But it will be conducted by a pair of space station residents.
Astronauts Michael Fossum and Ronald Garan Jr. will venture out Tuesday to retrieve a broken ammonia pump outside the International Space Station. They will stow the pump aboard the docked shuttle Atlantis, so it can be returned to Earth for evaluation. The two will also install a robotic refueling experiment on the 245-mile (394-kilometer) -high outpost.
Only four astronauts are flying aboard 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 NASA's 30-year shuttle program.