NASA/Goddard Space Flight Center
Expedition 35 Flight Engineers Chris Cassidy (pictured) and Tom Marshburn (out of frame) completed a spacewalk on May 11, 2013, to inspect and replace a pump controller box on the International Space Station. A leak of ammonia coolant from the area near or at the location of a Pump and Flow Control Subassembly was detected on Thursday, May 9, prompting engineers and flight controllers to begin plans to support the spacewalk. The device contains the mechanical systems that drive the cooling functions for the port truss. (Credit: NASA/Goddard Space Flight Center)
