The Astronauts will be replacing a backup computer k**wn as a Multiplexer/Demultiplexer (MDM), which failed on April 11. It "provides telemetry and commands to truss systems, solar alpha rotary joints and the Mobile Transporter rail car which rides along the truss structure," according to NASA, and both of the computers have been at the International Space Station for more than 10 years Read more...