抄録
Future lunar surface missions will require reliable and accurate positioning, particularly for autonomous rover operations. Although dedicated lunar navigation satellite systems are being developed, their vertical positioning performance can be limited by satellite availability and observation geometry, especially during early deployment phases. In this context, this study investigated a radiometric navigation architecture in which a surface station (SS) complements lunar navigation satellites by providing satellite observations for differential processing and an additional surface-to-surface ranging measurement to improve the vertical positioning performance of lunar surface users. The SS receives pseudorange and Doppler signals from the navigation satellites, which are used by the user to form double-differenced measurements that reduce clock and common-mode ephemeris errors and enable positioning of the rover relative to the SS. In addition, dual one-way ranging (DOWR) is performed between the SS and rover. The user (rover) then integrates the position solution obtained from these radiometric measurements with dead-reckoning information from a rover navigation sensor. Numerical Monte Carlo simulations were performed using five lunar navigation satellites representing NASA's LCRNS constellation and a rover trajectory around Connecting Ridge near the lunar south pole. The results showed that introducing the SS improved both horizontal and vertical relative positioning performance, and that SS–rover ranging provided an additional improvement. In the simulated representative case, the mean 99.7% vertical positioning error was reduced from 29.9 m without the SS to 5.5 m when the SS was used for double-differenced pseudorange and Doppler processing, and further reduced to 4.8 m when SS–rover DOWR was additionally included. The simulations also showed that an uncorrected DOWR hardware bias could significantly degrade positioning performance, whereas the proposed bias-estimation process reduced the final DOWR-bias estimation error to 0.058 ± 0.057 m. The results further revealed that the benefit of SS–rover ranging depended on the observation geometry. Overall, the results quantitatively demonstrated the potential of a lunar SS to play an additional role beyond communication, differential corrections, and satellite orbit determination: directly improving the vertical relative positioning of lunar surface users through an additional radiometric ranging measurement.