Terrain-Relative and Beacon-Relative Navigation for Lunar Powered Descent and Landing

As NASA prepares to return humans to the Moon and establish a long-term presence on the surface, technologies must be developed to access previously unvisited terrain regardless of the condition. Among these technologies is a guidance, navigation, and control (GN&C) system capable of safely and precisely delivering a spacecraft, whether manned or robotic, to a predetermined landing area. This article presents a detailed study of both terrain-relative navigation using a terrain-scanning instrument and radiometric navigation using beacons in lunar orbit or on the surface of the Moon. The models for these sensors are developed along with a baseline sensor suite that includes an IMU, star-camera, altimeter, and velocimeter. Linear covariance analysis is used to rapidly perform the trade studies relevant to this problem and to provide the navigation performance data necessary to determine how each navigation method can be used to support a 100 m 3-σ navigation requirement on landing.