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Mars Pathfinder, launching in December 1996 and landing July 4, 1997, will demonstrate a low-cost delivery system to the surface of Mars. A rover will be deployed to perform mobility tests, image its surroundings, and place a spectrometer against rocks to make elemental composition measurements. After impact on the surface of Mars, the lander will deploy its three solar panels for power, the camera will view the surroundings and the rover will be positioned for deployment to the surface. First, the lander will transmit the engineering and science data collected during descent through Mars' thin atmosphere. Then its camera will take a panoramic image of its surroundings and begin transmitting it directly to Earth at a few hundred bits per second. The rover, which will have been carried in a stowed configuration with the body lowered, will extend to its full height before it leaves the lander. It will roll down a deployment ramp to the surface and will then be independent except for using the lander data and communications functions for contact with Earth. After the lander transmits its engineering data and panorama image to Earth, much of its mission will be focused on supporting the rover with imaging telecommunications and data storage. The rover, named Sojourner, has a rocker-bogie suspension system. A computer generated image of the rover is shown in figure 1. The rocker-bogie suspension system utilizes a six-wheel drive platform without axles or springs. The system kinematically adapts to terrain geometry and can negotiate obstacles twice the wheel diameter. Precise steering is performed with steering actuators mounted above the four outer wheels. The rover can turn in place. The Martian environment is, to a great degree, uncertain. Detailed information about the terrain's grades and soil characteristics are not available. As such, the behavior of the rover on the surface of Mars is unknown.
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