Sojourner driver Brian Cooper, a video game master since childhood, developed the software for the highly sophisticated driving system. Although Sojourner looked like a remote control toy car, steering her across Mars would be considerably more complicated. It would take at least 10 minutes for signals to travel across the 119 million miles that separated Mars from Earth. Sojourner could roll over a cliff before an order to halt reached her.
Brian had to plan the best and safest route in advance. He would sit at a computer console with a set of battery operated goggles over his eyes. Through the goggles, he would see 3-D images of the landing site taken by the camera on the Pathfinder lander. Using a joystick, Brian would "steer" a rover-shaped cursor to a particular rock or other feature. This destination, and the instructions for getting there, would be radioed to Sojourner. To assure her safety, the rover would move very slowly. Her top cruising speed would be only 2 feet per minute.