A novel orbit determination and time synchronization architecture for a radio navigation satellite constellation in the cislunar environment

This paper presents a novel concept for orbit determination and time synchronization of a lunar radio navigation system. The proposed approach is based on small ground antennas that simultaneously track the entire constellation using K-band frequency links, implementing the concept of multiple spacecraft per aperture. This configuration ensures sufficient data rates and provides high accuracy in Doppler, range, and single-beam interferometry observables, enabling a precise orbit determination. We assess the achieved time transfer accuracies using both the standard asynchronous two-way satellite time and frequency transfer and a novel time transfer method that leverages onboard code epoch time-stamping and precise spacecraft range information. We propose a structure for the navigation message as well as a reference frame and associated time scale for user positioning. We complete the analysis by estimating the attainable accuracies of the signal-in-space error.