A Local-Area GPS Pseudolite-Based Navigation System for Mars Rovers

Tasks envisioned for future generation Mars rovers—sample collection, area survey, resource mining, habitat construction, etc.—will require greatly enhanced navigational capabilities over those possessed by the Mars Sojourner rover. Many of these tasks will involve cooperative efforts by multiple rovers and other agents, adding further requirements both for accuracy and commonality between users. This paper presents a new navigation system called a Self-Calibrating Pseudolite Array (SCPA) that can provide centimeter-level, drift-free localization to multiple rovers within a local area by utilizing GPS-based transceivers deployed in a ground-based array. Such a system of localized beacons can replace or augment a system based on orbiting satellite transmitters, and is capable of fully autonomous operations and calibration. This paper describes the basic principles of navigation using an SCPA, focusing on the critical issue of array self-calibration. The new algorithm presented herein—called Quadratic Iterative Least Squares—achieves successful self-calibration 99.80% of the time even under extremely adverse conditions. The paper concludes with a description of the experimental prototype developed to demonstrate these capabilities and presents successful results from field trials which validate both the navigation and self-calibration functions of the SCPA.