QUESTION:
We are wondering how does the telescope operator fix the telescope if
it breaks while it is flying.  Do you carry a whole bunch of spare parts
to fix whatever breaks?

ANSWER from Walt Miller on October 11, 1995:
I received your question about how the telescope operator fixes the
telescope when something goes wrong during a flight.  Although I am an
electrical engineer and not a telescope operator, I will try to give
you a flavor of what happens during a KAO flight.

A number of spare parts are carried for the telescope system, but it is
not possible to work on the telescope itself since it is not inside the
cabin, but instead it is in the cavity (essentially OUTSIDE the airplane).
The part of the telescope that sticks through the cavity wall can be reached
(that is where the scientists instrument mounts usually), and there are
some adjustments that can be made there, such as trimming the telescope
balancing weights.  Most of the telescope problems in-flight occur in
electronics (such as the telescope controller) which ARE mounted in racks
inside the cabin.  Often just cycling power on one of these boxes will
cause a reset which fixes a glitch.  Sometimes it helps to jiggle loose
boards or connectors.  If a tracking camera inside the cavity fails, we
can usually switch to another camera and continue the mission.  If a hard
failure occurs in other critical equipment on the telescope inside the
cavity (such as a gyroscope or the oscillating secondary mirror), we have
no choice but to abort the flight and return home.  The failed parts are
repaired or replaced on the ground, and we reschedule the flight for
another day.

Regards,
Walter Miller