QUESTION:
As with other missions, the ability to deploy the panels for solar use, high
gain communications, or any  for that matter, has not been as good
as could be. What has been done in ensuring successful operation now or in
the future? It seems without them opening up all the way it can cause major
problems. Like Galileo's high gain antenna and Mars Surveyor's 20 degree
shortfall in deployment of its solar panels. What is being done to make sure
the Pathfinder doesn't disappear like the Mars Observer or experience major
problems?

ANSWER from Rob Manning:
No one can build a complex spacecraft that is absolutely guranteed to work.
Embarking on unique, first-of-a-kind enterprises, by their very nature,
invoke risk taking. However we can go to great lengths within the limits of
our budget to minimize technical risk. Much like the design process leading
to a passenger jet, spacecraft designers must ensure that design margins
conservatively exceed the uncertainty in the expected environment and that
the spacecraft is tested to those environments. Much work then must be
placed in understanding the environment, followed by as much testing as
money and time will allow. We feel quite certain (and many independent
reviewers have agreed) that although Mars Pathfinder is about 1/10th total
mission cost of Mars Observer, that we have struck an appropriate balance
between cost and risk.

--Rob Manning, Mars Pathfinder Flight System Chief Engineer

ANSWER from David Dubov:
The problems associated with moving parts are difficult ones to solve. Since
the cost to send one kilogram of material into space is so high, spacecraft
designers must be very stingy in allocating mass to the engineers who make
the mechanisms. You might be surprised that the typical spacecraft mechanism
can be destroyed with your bare hands!

The other part of this equation is that MOST of the time, mechanisms must
only need do their jobs under rather benign weightless conditions in space,
BUT they must also be able to handle the much rougher conditions that
precede getting there: ground handling and launch. It is these phases of the
mechanism's life that are the most traumatic. They are the most difficult to
quantify as well. I don't think the designers of the Galileo high gain
antenna mechanism would have expected that the antenna would be closed for
so long before finally opened in flight and that it would have had to
survive three cross-country road trips in a van! (Both of these events were
a direct result of the Challenger disaster.)

There is no magic formula for making mechanisms work in all situations, but
we have been learning just how subtle these problems can be. The trick is to
learn from your (and other people's) mistakes. Mars Pathfinder has more than
its share of moving parts. We knew that going in, so we went out of our way
to be a bit paranoid about it. We hired the very best spacecraft mechanical
engineers we could find. Going to Mars made the job a bit more difficult in
some cases because of our need to have the mechanisms work under very harsh
environmental conditions (harsher even than in deep space). For example, the
Rover, the IMP camera and the high gain antenna actuators must all work
under very cold conditions (as low as -90 deg C). Most lubricants do not
lubricate at those temperatures. We had to make sure that the actuators were
either warmed before they were used or had adequate torque margins for the
motor to overcome the sticky lubricant before it warmed up with use. In some
cases we "overkilled" the problem (e.g. the lander petal actuators) and
provided much more torque than we thought we really needed - just in case.
(I could go on and on.) It is safe to say that the mechanisms on Mars
Pathfinder were a LOT of work. But we tested and tested them (even beating
them up!) under many rough conditions until we were finally satisfied that
they will work fine when we need them to.