Mars Pathfinder

Process control

Rover driver pilots his boyhood dreams across face of Red Planet

By Paul Hoversten
For July 7, 1997
Gannett News Service

PASADENA, Calif. - Brian Cooper loved to play with remote-controlled planes and cars as a boy.

Now, the 37-year-old computer engineer is piloting the ultimate remote control machine, the $25 million Sojourner, along the Martian surface.

Cooper's job is to send a set of commands each day from his desktop computer to the 23-pound robotic rover, directing it to geologically interesting rocks in a Martian flood plain called Ares Vallis. The commands from JPL are relayed to the rover through the Mars Pathfinder lander that carried it to the planet.

When it arrives at a rock, Sojourner takes a photo and then places its X-ray spectrometer on the rock much like a doctor puts a stethoscope on a patient. It takes 10 hours for Sojourner to analyze the chemical and mineral content of a single rock in this fashion.

"What we end up doing is telling the rover where to go for an entire day's motion," says Cooper.

Then it's up to Sojourner to get there. Cooper can't watch the journey as it happens because there's a 10 1/2-minute lag in signal time between Earth and Mars, which are 119 million miles apart.

"It's not a joystick, so it's really a different feeling," he says. "We're giving it an extended series of goals and saying, `Rover, please get there, but first and foremost, remain safe.' We're relying on its ability to navigate."

Sojourner's on-board computer is limited in memory but still clever enough that "it will find its way out a maze if you give it enough time," says Cooper. "Even if I told it to go over a cliff, as long as the sensing is working, it would sense there's a cliff and not go over it."

With 3-D goggles, Cooper can "see" what Pathfinder's camera saw nearly 11 minutes earlier as it photographed Sojourner's progress.

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