Lunal landing navigation supported by ranging to an orbiter

Precise and safe landings on celestial bodies as the Moon are needed for the further exploration and potential future exploitation of solar system bodies. The current navigation systems for landing probes are based on sensor data fusion of inertial and optical sensor measurements to determine the current flight state with respect to the target body and the desired landing site. To improve the accuracy of lunar landing navigation, radiometric measurements (range and range-rate) with respect to an orbiting vehicle have been proposed in several studies. This paper analyzes the impact of range and range-rate measurements from an orbiting vehicle on the navigation accuracy. For that purpose, a baseline configuration of an optical navigation system is used which has already been taken as a reference for investigating the effect of ground-based beacons. First, the influence of the orbiter trajectory in relation to the landing trajectory is investigated. In particular, the line of sight between orbiter and lander permits a preliminary assessment of the navigation performance. Later, the effects of sensor noise for all measurements and of the orbiter ephemeris error are also evaluated. Finally, for a selected scenario, it is demonstrated that radiometric measurements with respect to an orbiter can reduce the positioning error by about 40%.