Page 97 - Modern Robotics Building Versatile Macines

ROBOT EXPLORERS 77

or a pit appears suddenly in the rover’s path. It would take at least
10 minutes for that information to reach controllers on Earth and
another 10 minutes for a command such as “turn right 30 degrees”
to reach the rover. By then the rover may have crashed into some-
thing or become hopelessly stuck.
This means that a rover must have considerable autonomy, or the
ability to make its own decisions about the environment. With a rover
like Sojourner, the controllers send detailed instructions for each
planned activity, including the location (such as a rock) to which the
rover is to move. The robot then takes over, using a camera and laser
system to chart a course around obstacles. (This would be greatly
aided by an innovative locomotion system featuring wheels that can
“rock” or tilt up in order to roll over the smaller obstacles.)
By the 1980s, robotics researchers at JPL and a number of uni-
versity research labs were developing robots that had some of these
navigation capabilities. As computer processors became more pow-
erful and smaller, it began to be possible to put more intelligence
aboard a roving robot. Nevertheless, Shirley and the other manag-
ers and engineers on the rover team felt they could not adopt the
most ambitious ideas of the artificial intelligence researchers. Only
an effective partnership between human controllers and the robot
would allow for reliable operations on the Martian surface.
Besides navigating and avoiding accidents, software aboard the
rover must also include default instructions such as what to do if it
loses radio contact with base—in this case the lander, which relays
the rover’s transmissions to and from Earth, either directly or via
satellites in orbit around Mars.
All of the necessary computers, control and communications sys-
tems, solar and battery power systems, locomotion systems, and the
cameras and science instruments would have to fit in a rover that
weighs only 23 pounds (10.5 kg)—less than many dogs!

Sojourner’s Truth

Besides her role in planning and organizing the Mars Pathfinder
mission and rover development, Shirley continued to work with pub-
lic relations. In one mildly controversial initiative, she organized a