Abstract: In this article, line-of-sight (LOS) measurement based autonomous optical relative navigation algorithms for landing spacecraft on asteroids are presented; observability analysis of the navigation algorithms is also carried out in detail. First, navigation measurement equations and measurement sensitive matrices are provided based on the colinear equation of perspective projection. Next, spacecraft position and attitude parameters are estimated using the Gaussian least square differential correction (GLSDC) algorithm and Levenberg-Marquardt (LM) algorithm by multiple line-of-sight measurements. Then, navigation system observability and observable degree with different quantitative line-of-sight measurements are analyzed in detail by rank analysis of the error variance inverse matrix. Finally, the validity of the autonomous navigation algorithms presented in this article is confirmed by mathematical simulation.

Key words: asteroid landing, line-of-sight measurement, autonomous optical relative navigation, observability