Spacewalkers to tackle leak at space station

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In this image made from video provided by NASA, astronauts Chris Cassidy, foreground, and Tom Marshburn prepare for a possible spacewalk from the International Space Station on Friday, May 10, 2013. NASA will decide later Friday if the two astronauts will step outside the station to work on a leaking coolant line. The line chills power systems but power was rerouted and is operating normally. The six-member crew is not in danger. (AP Photo/NASA)

CAPE CANAVERAL, Fla. (AP) — Two astronauts will venture outside the International Space Station on Saturday to tackle an ammonia leak in the power cooling system.

The leak was discovered Thursday and the repair job was quickly planned for the weekend.

Spacewalks usually aren't done on such short notice. But NASA wanted to try to fix the leak before all the ammonia escaped. The space agency also wanted to take advantage of a veteran spacewalker who is due to return home on Monday with two other astronauts.

The two spacewalkers — Americans Chris Cassidy and Tom Marshburn — will swap out a pump box on one of the eight solar panels that supply electricity to the station.

NASA says the station has plenty of power, and the six-man crew is not in danger.