Simultaneous Localization and Calibration for Radio Navigation on the Moon: Results from an Analogue Mission

Abstract

Autonomous robotic system will play a crucial role in future exploration missions to Mars or the Moon. Autonomous operation requires reliable navigation and communication. While a satellite communication and navigation system for the Moon is planned, only few satellites are foreseen. Accuracy and availability can be increased by a local radio system for communication and cooperative navigation. Based on the signal round-trip time (RTT) and direction-of-arrival (DoA), positions and orientations of the robots are estimated. Accurate distance estimation by the RTT requires calibrated transceiver and antenna group delays, and accurate DoA estimation requires antenna calibration. Usually, these calibrations are performed once before the system becomes operational. However, calibration parameters can change, for instance due to varying temperature of RF components or reconfigurable antenna surroundings. Thus, we propose to estimate antenna responses and direction-dependent ranging biases simultaneously with positions and orientations by simultaneous localization and calibration (SLAC). In this paper, we derive a SLAC algorithm, which is suitable for arbitrary antenna types. The algorithm is then evaluated with measurement data obtained in a Moon-analogue mission with robotic rovers that took place on the volcano Mt Etna, Sicily. We show that by SLAC, the position error of the robots is reduced by more than a factor of two.