Autonomous deployment of a Self-Calibrating Pseudolite Array for Mars rover navigation

A "Self-Calibrating Pseudolite Array (SCPA)" is a self-deployable GPS pseudolite-based local-area navigation system applicable to future-generation Mars rovers. By utilizing bidirectional GPS transceivers (incorporating separate GPS pseudolites and GPS receivers) deployed in a ground-based array, the SCPA can provide all the benefits of satellite-based Carrier-phase Differential GPS (CDGPS), such as drift-free, centimeter-level, and three-dimensional positioning, without requiring a satellite constellation on Mars. Relative geometry change by moving the rover enables the SCPA to self-calibrate both the array locations and the rover trajectory to centimeter-level accuracy. This self-calibration capability of the SCPA overcomes the difficulty of autonomous robotic deployment of the pseudolite-based navigation system on Mars, eliminating the need for accurate a priori position information or precise placement of the array. This paper presents new results from the latest field trial of the SCPA conducted in February 2004 using the K9 Mars rover platform operated in the Marscape at NASA Ames Research Center. This field trial demonstrates the entire scenario of the SCPA operation, starting with autonomous array deployment, followed by array self-calibration and centimeter-level navigation for a long traverse. The results show that a 0.2% drift rate is achieved by the SCPA navigation (0.4 meter of the final positioning error after a 174.7 meter traverse).