ISS Contingency Spacewalk

Spacewalkers Peggy Whitson and Jack Fischer will venture outside the hatches of the International Space Station on Tuesday in a hurriedly planned EVA to replace a failed computer box on the Station's central truss segment. One of two External Control Zone Multiplexer/Demultiplexer units failed at 18:13 UTC on Saturday, May 20 - leaving ISS in a non-redundant configuration with only one working EXT MDM. A spare MDM was assembled and tested in orbit on Sunday and EVA procedures and equipment were readied on Monday to send the crew out the door on Tuesday on a short EVA of two hours. A second task added to the EVA timeline is the installation of a pair of wireless antennas on the Destiny Laboratory.