NASA Astronauts Steve Swanson and Rick Mastracchio completed a spacewalk today to replace a failed Multiplexer/Demultiplexer (MDM) back up computer, think of it as kind of a relay computer used to run some of the robotics on the spacecraft.
The problem was discovered during a routine check by Mission Control. This was a backup system and there was no problem with the primary system so there was never a danger to either the crew or the station. Still the back up is kind of an urgent need. The failed computer has been in place since April 2002 when is was delivered already installed on a station truss.
Hopefully we will hear of any forensic results concerning the failure; 12 years could be just old age. Still I’m curious.