Describes the field testing of the Hyperion robotics project which uses the concept of sun-synchronous navigation. Hyperion is made of aluminum tubing and has four, wheels on two axles. Each wheel has a motor, and the front axle has a passive joint that can roll and yaw relative to the back end. Hyperion steers by driving the wheels at different speeds, and the passive front-axle joint turns the robot in arcs. The 1.5 meter-high front axle gives the robot's digital cameras and laser scanner a view of surrounding terrain; the latter helps it detect close-range obstacles. A third panoramic camera offers remote observers a view of its surroundings. All other robot components are housed in the body, which is mounted between the axles. Hyperion uses a pair of global positioning system receivers and an odometric system to determine its position and orientation and wheel-based odometric:sensing to estimate motion. Odometry also enables positioning and orientation on other planets, where the robot could use things such as a star, sun, or terrain landmark in place of GPS. Multiple onboard sensors act as Hyperion's health-monitoring and fault-detection system, checking everything from computer processes and laser scanners to a sensor suite that monitors the rate at which the system receives GPS information. The planner combines a priori knowledge of terrain, planetary rotation, sun location, solar flux predictions, and predictions of rover capability.