Range Biases, Measurement Noise, and Perilune Accuracy in Near Rectilinear Halo Orbit Navigation

The characteristics of Near Rectilinear Halo Orbits (NRHOs) that make them desirable for cislunar operations also introduce navigation challenges. The orbit’s large apolune distance provides excellent coverage of the lunar south pole, and its Earth-facing plane ensures constant line-of-sight with ground stations. However, the nearly perpendicular motion to the Earth-spacecraft line results in poor observability of range biases, and the necessarily low perilune altitude results in highly dynamic and sensitive perilune passages. Preliminary work indicates that range biases and state estimates near apolune and perilune are unintuitively related to range and range-rate measurement quality. This study seeks to clarify the relationship between measurements and navigation solutions, as well as to provide insight into filter designs that are more suitable for NRHO navigation operations.