(AP) -- Discovery's astronauts took one final spacewalk at the International Space Station on Wednesday to get the outpost squared away before the shuttle program ends.
Discovery is headed into retirement after this flight, and only two more shuttle trips remain, by Endeavour and then Atlantis.
Spacewalker Alvin Drew quickly headed to a broken pump and drained the last bit of ammonia left to make it safe for handling in case it's returned to Earth on the last shuttle mission this summer.
The toxic ammonia coolant - about 10 pounds' worth - was vented through a hose out to open space, away from the two spacewalkers. It took two minutes to empty the pump.
A few pieces of frozen ammonia appeared to float away. Mission Control asked if spacewalker Stephen Bowen encountered any of the bits of ice, and he replied that he had not. Controllers wanted to keep any ammonia residue from getting into the space station.
Drew was invigorated and working so fast that Mission Control cautioned him, barely an hour into the spacewalk, to slow down. He obliged as he carefully bagged the venting tool and then turned to other chores.
The two spacewalkers whittled down the to-do list, installing a rail car light and an outdoor robot's camera. They also removed an experiment platform and some insulation. It was a hodgepodge of relatively minor jobs that will leave the orbiting lab in the best possible condition once space shuttles stop flying.
They paused to snap pictures of NASA's launch site, as the shuttle-station complex sailed 220 miles above Cape Canaveral.
Overseeing the action from Mission Control was astronaut Timothy Kopra. He was supposed to be the lead spacewalker, but was hurt in a bicycle accident last month. Bowen replaced him.
"Tim, it is great to hear your voice," shuttle astronaut Michael Barratt called down.
"Likewise," replied Kopra, who hobbled into Mission Control on crutches.
The only problem cropped up just before Wednesday's spacewalk. A leak in Bowen's suit had to be fixed before the astronauts could venture out for the second time in three days.
Discovery will remain at the space station until Sunday. The shuttle astronauts are staying an extra day to help outfit the new storage room installed Tuesday.
A humanoid robot - the first one in space - was carried up in the storage unit. It will remain boxed up until May, then put through a series of tests to see if it might help the space station crew with simple chores.
Once Discovery's 12-day flight ends Tuesday, the shuttle will be decommissioned and sent to the Smithsonian Institution for display.
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More information: NASA: http://www.nasa.gov/mission-pages/shuttle/main/index.html