QUESTION:
How do you get everything on the Mars Global Surveyor, the Pathfinder,
and the Sojourner to work when it's supposed to?
 
ANSWER from Charles Whetsel on June 16, 1997:
In addition to the main software programs that were loaded before launch
onto the computers inside each of the spacecraft, we also are able to send
short scripts or "sequences" on the radio link to them to let them know
what we want to do in the near future.  Sequences can have instructions on
what the spacecraft is supposed to do covering a period of time as short as
a day or less (like when Sojourner is on the surface of Mars and very busy)
to as long as a month or more (like when Surveyor is cruising to Mars and
there's nothing interesting to look at except for the stars).