QUESTION:
I had a though about the solar panels on the Sagan Memorial Station (SMS).
Would the panel produce more electricty if at sunrise/sunset the appropriate
petal was raised to make its angle to the sun more nearly normal? Obviously
the orientation of SMS might not make this useful and also raising/lowering
the petals takes power, but if it resulted in a net increase in the charging
rate outside the times when the sun is directly overhead, it might extend
the battery and mission lifetime.

ANSWER from Chris Salvo on August 20, 1997:
In our more relaxed and "what-if-ish" moments we too have had thoughts of
moving the petals to track the sun.  In reality, we will never do it on
Pathfinder.  There are two main concerns.
     
1.  There is a very strict coordinate system that has been established at
the landing site which is used to correlate imaging from day to day.  The
rover is particularly dependent upon the accuracy of the stereo imaging
which it uses for navigation.
     
If we move the petals we will certainly change the tilt of the spacecraft. 
There is also a possibility that the spacecraft would rotate about its
vertical axis, or even translate (move horizontally) on the surface some
amount.
     
The first problem (tilt) is detectable on board since we have accelerometers
which tell us which way is up.  This we could probably correct for with
relatively little difficulty.  The second and third problems (rotation and
translation) cannot be detected by the spacecraft and would be much more
difficult to deal with.  We would have to determine based on imaging that
these movements had occurred.  This is problematic as there are errors in
the camera pointing and limitations in our ability to discern movement in
the images.
     
2.  The BIGGER problem involves destroying the lander.  The petal actuators
(motors) are extremely powerful (they have more torque than a high powered
super-sports car).  If they were to start to move towards the lander (close)
and then they could not be commanded to stop, they would literally crush the
components on the base petal of the lander.  While this was only a slight
risk on the first sol (in fact we did move one of the petals as you may
recall on Sol 1), it is a larger concern now.  The electronics that control
the motion of the petal actuators are outside the thermal enclosure in which
most of the electronics are housed.  The petal actuator electronics have
been subjected to severely low temperatures (-80 to -100 C).  They were not
designed to withstand such thermal extremes and there is a good chance that
they would no longer function properly if we were to turn them on.  It is
likely that they would not turn on at all.  In the worst case they would
turn on (start to close) but never turn off.  That would be bad.