Rolling Around on Mars

Meet the man who tells the Mars Rover where to roam

Brian Cooper drives the ultimate in radio-controlled cars. From the air-conditioned comfort of his cubicle at the Jet Propulsion Laboratory in Pasadena, Calif., Mr. Cooper controls Sojourner, the six-wheeled rover inching its way across the surface of Mars.

Sojourner has special cameras and a device for "sniffing" out the chemicals in rocks. It's like having a geologist on Mars. Scientists want to know what Martian rocks are made of, because that might tell them whether there was ever life on Mars.

Cooper's job is to make sure Sojourner goes where the scientists want it to.

Sojourner is really no different than a radio-guided monster truck from the toy store. It's powered by electricity and it's radio controlled.

But Sojourner's electricity comes from batteries and a solar panel. Its radioed commands come from Earth, 120 million miles away. And the microwave-oven-sized rover is loaded with special equipment. It cost $25 million.

Radio signals take 10-1/2 minutes to make a one-way trip to Mars from Earth, and Cooper also must wait for pictures to come back from the mission's electronic "photo lab" to see whether Sojourner went to the right place. So he doesn't drive Sojourner the way you would a radio-controlled car. Instead, he sends a group of commands telling the rover where the scientists want it to end up. The rover heads there with enough on-board smarts to stay out of trouble. At the end of the Martian day, engineers take a picture of the rover with the camera on the lander to see if Sojourner did what they asked it to. The picture is used to plan the rover's activity for the next day.

Like many of the people taking part in this mission, Cooper set his sights on a job involving space exploration after watching United States astronauts land on the moon.

"I was inspired by the 1969 moon landings and the movie '2001: A Space Odyssey,' " Cooper says. "I was always interested in how things worked and in optical illustions and our visual sense."

His interest in illusions led him to become a professional magician. He's performed at Hollywood's Magic Castle since he was 14. Now he works with what he calls "that visual sense" in controlling the rover.

When he came to JPL from the Air Force in 1985, he began working on ways to allow people to control robotic vehicles. He became the lead "test driver" for them.

On this mission, Cooper explains, "scientists tell me, 'We want to go to this location.' " Sitting at his computer wearing special high-tech 3-D glasses, he looks at images of Pathfinder's landing site to "determine whether we can get there, based on the terrain. Can we get there in one day or two days? And along the way, let's try to fit in all these other science and engineering experiments."

For the first week, he and his backup driver sent complicated commands that told Sojourner where to go and how to get there. Now they've been giving the rover places to go, but they're letting the rover's on-board sensors and computers pick the best path to follow.

"It's the safest way to drive on Mars, because we enable the rover to avoid hazards it may perceive that I won't. If it gets confused about its direction, it still will not bump into things and get hurt," Cooper says.

Sojourner's extended visit last week to Yogi, a bear of a boulder, shows how the rover is designed to keep its driver from getting into trouble. Cooper's backup driver gave Sojourner detailed instructions rather than let it find its own way, because the distance the rover had to travel was less than 3 feet. But the driver slightly miscalculated. On Wednesday, Sojourner overshot its destination by about 4 inches, and one of its front wheels began to climb the rock. The rover's onboard computer ordered it to stop before the rover reached a point where it might tip over. But it stood in its awkward position until Saturday, when it finally got instructions from Earth to back up and try again. (A radio glitch prevented Sojourner from backing off earlier.)

Cooper says that working with Sojourner means trying to keep his sleep schedule in step with Mars time; measured with an earthbound clock, a Martian day is 24 hours and 37 minutes long. Short-ly after Pathfinder landed, he says, he worked three 20-hour days.


The Mars Pathfinder Mission has increased interest in Mars/space-related web pages. Some of the best sites include:

Passport to Knowledge:

An excellent page for children and teachers. A very simple, concise presentation of information. Also includes children's poems, artwork, and other writings about Mars. Lots of ideas for teachers.

Cassini: Voyage to Saturn:

A fantastic site with colorful images and clear, interesting facts about Saturn and the future exploration mission, Cassini, scheduled for launch in October 1997. An entertaining kids page distills the most important information about the planet.

Australia's Telerobot on the Web:

This page lets you control a robotic arm in an Australian laboratory from your own PC, similar to how scientists control the rover on Mars.

Mars Pathfinder Home Page:

This NASA site has an extensive archive of Pathfinder images. There isn't much variety, however, and the pictures aren't that clear. Little of the information is current.

Project Galileo:

An excellent collection of vivid pictures and a wealth of information about the exploration of Jupiter and its moons. Some of the information is a little too technical.

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