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

Abstract

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 (GNC) system capable of safely and precisely delivering a spacecraft, whether manned or robotic, to a predetermined landing area. This thesis presents detailed research of both terrain-relative navigation using a terrain-scanning instrument and beacon-relative 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 altimeter, IMU, velocimeter, and star camera. 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 which navigation method is best suited to support a 100 m 3-σ navigation requirement for landing anytime and anywhere on the moon.(90 pages) iv

Beacons for supporting lunar landing navigation

“…This position is a good trade-off between minimization of evaluation functions and final errors and the constraints imposed by the avoidance zone. Although in [6,7] the avoidance zones were not considered, a similar optimal position for the beacon was found by covariance analysis.…”

“…In [6,7] the performance of a lander navigation aided by RF measurements (beacon-relative) has been studied, where the lander transponds signals from available RF assets, i.e. LRS or LCT, receiving range and range rate information from them.…”

“…These measurements are inserted in a EKF together with other navigation measurements coming from IMU, star camera, velocimeter and altimeter, which is the basic sensor suite of ALHAT [8]. The study in [6,7] has evaluated the performance of the navigation accuracy through linear covariance analyses, when on-board system is supported by a single surface beacon. The result shows that surface beacons provide the best RF measure if they are not located directly under the path of the lander as it approaches the landing site.…”

Linear Covariance Techniques for Powered Ascent

“…Linear covariance techniques have been successfully applied to many GNC system problems in aerospace, such as orbital rendezvous and proximity operations, 1-4 cislunar trajectories, lunar powered descent and landing, 5,6 interplanetary missions, 7 and powered ascent, just to name a few. In the case of powered ascent, however, existing linear covariance simulations are limited to evaluating the performance of the navigation system in an open-loop setting, commonly referred to as navigation performance analysis.…”

Using Estimation Techniques in Multidisciplinary Design

“…This is achieved through the application of a Kalman filter in a method analogous to that in linear covariance analysis. [5][6][7] This paper provides the necessary fundamentals to apply this dynamical systems technique to the MDA/O problem and then shows its applicability through two example problems. In addition, a note regarding a bounding technique on the variance which utilizes the covariance matrix is provided.…”