EVA 21.

ISS035-E-040238 (11 May 2013) --- Expedition 35 Flight Engineers Chris Cassidy (pictured) and Tom Marshburn (out of frame) completed a space walk at 2:14 p.m. EDT May 11 to inspect and replace a pump controller box on the International Space Station's far port truss (P6) leaking ammonia coolant. The two NASA astronauts began the 5-hour, 30-minute space walk at 8:44 a.m.