QUESTION:
The Sojourner rover cannot be talked to directly from Earth.  It must be
communicated with (indirectly) through the MPF lander. Could the rover be
used even after the lander dies?

ANSWER from Guy Beutelschies on July 23, 1997:
The Sojourner rover must use the lander to communicate to the Earth since
its communication's power will only work up to about a hundred meters.
Future rovers will be able to communicate to the Earth through orbiters like
Mars Global Surveyor.  The reasons that this was not done for this mission
were:

1) There are currently no orbiters around Mars (Mars Global Surveyor doesn't
show up for several months).  It would have cost much more (in dollars,
mass, power, and schedule) to put a system that could communicate the
hundreds of kilometers needed to reach an orbiter onboard the Rover.

2) To keep costs down, the qualification of parts on the Rover was only done
for a mission life of 10 days (although we expect it to last much longer). 
The lander is qualified to 30 days on the surface so it is more likely that
the lander will last longer than the rover.

3) The bottom line is that we were given a task of putting a lander and a
Rover on the surface that would last 30 days for a small of amount of money
(compared to other NASA missions) and a short schedule.  To achieve that, we
had to brutally cut out anything that was deemed not essential to achieving
those goals.  An enhanced Rover communication system, while nice for an
extended mission, would have jeopordized getting to launch under the
schedule and budget constraints.

Guy Beutelschies	Mars Pathfinder Flight Engineer