As
Hubble's power-switching station, the Power Control Unit (PCU) controls
and distributes electricity from the solar arrays and batteries
to other parts of the telescope.
The new PCU increases the reliability and
longevity of the telescope. It handles the increased power from
the new solar arrays better than the old PCU could have.
Replacing the original PCU, which has been
on the job for 11 years, will require the Hubble to be completely
powered down for the first time since its launch in 1990. Anytime
something is "turned off," there is a risk that it may
not "turn on" again.
The switch-out is a very complicated process: there are 36 different connectors
that have to be taken off the old PCU and put on the new one.
This will take a lot of time, so an entire day is devoted to making
this change.
The PCU is the heart of the Hubble Space Telescope.
Its successful replacement is this mission's second most important
task, after replacement of the solar arrays.
