12:02pm  4.Jun.97.PDT Unlike most four-wheel-drive vehicles built in America, which rarely venture out of paved suburban cul-de-sacs and shopping-mall parking lots, Nomad is about to embark on a demanding journey that will test the limits of its capabilities.

The 825-pound vehicle, built by scientists at Carnegie Mellon University, is on its way to the Atacama desert in northern Chile for a 40-day, 125-mile trek across some of the Earth's most desolate terrain. But what's most unusual about Nomad is that its driver, or rather drivers, will mostly be kids who will operate the vehicle from the Carnegie Science Center in Pittsburgh, more than 5,000 miles away.

Nomad's mission is to test the capabilities of unmanned vehicles for planetary and Antarctic exploration. The vehicle, whose development was funded largely by NASA, will examine the viability of a number of emerging technologies in a harsh environment.

"This is a major step forward," said John Murphy, a doctoral student in robotics at CMU who has been part of the Nomad project for four years. "I don't know if it is the longest robotic traverse, but this is definitely one of the few that is being done in a real, rugged planetary environment."

By comparison, NASA's Rover Sojourner is slated to travel only a few meters on the surface of Mars when it lands there on 4 July aboard the Mars Pathfinder.

Nomad's experiments in the Atacama will focus on technological problems in the areas of locomotion, telecommunications, cameras, and display systems, and "safeguarded teleoperation," an expression that means "somewhere between completely mandated operation and completely free operation," Murphy said. "It turns out to be a much more difficult problem than either of those options."

After receiving a command from Pittsburgh, Nomad will have to examine the surrounding terrain and decide whether it can handle the directive. "We've been training the vehicle to figure what it can do, what it can't do, and what it could do but would probably rather not do," Murphy said.

For instance, a driver could tell the vehicle to go right, and Nomad may decide that it is better to go straight for a few feet and then turn right.

Nomad is also equipped with an experimental chassis that can expand its wheelbase so it can fit inside a small spacecraft and still be stable enough on rough terrain. In the communications area, Nomad is testing a tightly focused antenna system that can work reliably while traversing rugged terrain. The two-way broadband communications system will deliver instructions to Nomad, and relay images back to the science center. For that purpose, Nomad is equipped with a camera that captures a 360-degree view around itself that ranges from the ground to 40 degrees above the horizon.

"If you only get one chance to be someplace, you don't want to miss anything," Murphy said.

As Nomad begins trekking through the Atacama, at the speed of a slow walker, a view of its surroundings will be sent back to Pittsburgh, where they will be displayed on the inside of a dome-like screen.

"It's not exactly a videogame type of experience, but it is something not many people get to do," Murphy said about the trek, which is slated to begin on 18 June.

Being on the same time zone as Pittsburgh, Nomad's daylight will coincide with daylight hours at the science center. Also, the desert, with its rocky and mountainous terrain and its one inch of rain every 10 years, is similar to a planetary environment.

And the Atacama was a more exciting destination than deserts in the United States, because most Americans have never been there, Murphy said. In other words, for most visitors to the Carnegie Science Center, the Atacama may as well be on Mars.