Observability analysis of autonomous navigation system for Earth-lunar transfer orbit phase

Currently, international interest has revived for the scientific exploration of the Moon. In this paper, autonomous orbit navigation of spacecraft for lunar probe missions is implemented completely independent of a ground tracking system. In order to achieve this aim, the Doppler measurement duo to the relative motion from a probe to the Moon is used. Other measurements are the directional data and distance data from the ultraviolet sensor. The observability of the system with the available measurements is investigated using a novel observability analysis, which can provide an assessment of the degree of observability. Autonomous orbit navigation is obtained by extended Kalman filtering. The resultings of simulation show that adding radial velocity can improve the estimate accuracy. It is also proved from an observability index point of view.