ISS039-E-013244 (18 April 2014) --- NASA astronaut Rick Mastracchio, Expeditionn 39 flight engineer, replaces the Enhanced Input/Output Control Unit Circuit Card of the spare External Multiplexer/Demultiplexer (MDM), in preparation for an upcoming spacewalk. He will be joined by fellow NASA astronaut and Flight Engineer Steve Swanson on the spacewalk.
Photographer Steve Swanson
Date April 18, 2014