On Thursday, April 17, 2014 3:10:14 PM UTC-4, JF Mezei wrote:
They speak of a backup *computer*. Why would a backup computer be
outdoors ? I can understand a failed power controller, but the use of
the term "computer" puzzles me.


This item is properly referred to as a "multiplexer/de-multiplexer" which is just a fancy way of saying coverts from a multipurpose data stream to a single purpose data stream. But it can be thought of in terms of a special-purpose computer, not a general purpose one like a PC but more like a dedicated device controller, like the computer in your car for example. It has been designed from the get-go to withstand the rigors of the space environment it is in.
That is not to say of course that it will never fail. According to the writeup in NASASpaceFlight.com this particular unit is 13 years old having been brought up with the S0 Truss on STS-110 in April 2002.

A fairly detailed explanation can be found he

http://www.nasaspaceflight.com/2014/...m-failure-iss/

Dave



It is also disapointing that the canadian contribution DEXTRE was
designed to be able to swap electronic cards when they failed outdoors
in order to reduce the number of EVAs. Was DEXTRE ever used for actual
work, or is it just an ugly statue at top of the station that is just
used as a toy ?

Or is this more of a case of astronauts itching for any opportunity to
go outdoors for a breath of fresh air and some exercise and to get to
see the view ?

Is this unit located in a place that is inaccessible to DEXTRE?

Dave