QUESTION: 
How does the lander right itself?

ANSWER from Robert Manning on February 3, 1997:
As you know, when the airbags are all fully inflated, the Mars Pathfinder 
lander (with the rover snuggly tucked inside) looks like a lot like a 
giant beach ball (17 feet in diameter). The lander is suspended in the 
middle of the bags so that it can be protected from impacts from any 
direction. Of course the reason for this design is that the lander 
will hit the ground in any orientation and then bounce and roll in 
an arbitrary direction. It will then come to a stop in any orientation 
as well. 

Given this, the design wouldn't be complete unless there was a means 
for it to orient itself automatically after it comes to a stop. Since 
the lander is shaped like a tetrahedron (a three-sided pyramid) there 
are four sides that it can come to rest on after the bags deflate and 
are retracted by retraction motors (there are three side petals plus 
the base the lander's electronics are bolted to). The useful aspect 
of this shape is that if you open up the petal that is on the "bottom" 
after it comes to rest, the lander will roll over onto the base! We 
attached a hefty electric motor to the hinges of each of the three side 
petals.  Once the lander comes to rest, the on-board computer uses 
accelerometer readings to determine which way is "down". It then opens 
that petal using its motor which will do the job of rolling it over. 
Once on its base, the other two motors open up the remaining two petals.

In parallel with all this, the airbags get retracted toward the petals 
before they are fully opened so that they do not interfere with the petals 
or the ability of the Sojourner rover to get off of the lander.

-Rob