Autonomous navigation and rendezvous of spacecraft in lunar orbit

Abstract

The task of autonomous navigation of a spacecraft in a lunar orbit on optical measurements of the star tracker and Moon horizon sensor is considered. A method to carry out the measurements is proposed, and a recurrent algorithm for definition of a current estimate of an orbit by earlier measurements is developed. The accuracy of problem solution is investigated. It is shown that the accuracy of the orbit estimation is essentially influenced by errors in knowledge of topography of the lunar surface, as well as by errors of the gravitational field of the Moon. A possibility to use the topographic map of the Moon CLEM-L-LIDAR-TOPO-VI.0 received by the results of measurements performed on the spacecraft CLEMENTINE in 1994 and a model of the gravitational field of the Moon GLGM-2 of 70 × 70 to solve the navigation problem is considered. The results of modeling of the proposed method efficiency with regard to the topographic map of the Moon and the model of the gravitational field with the accuracy of navigation measurements of the star tracker and horizon sensor of ∼5″ have shown a possibility to maintain the positional accuracy of navigation in a lunar orbit of ∼50 m, which is commensurable with the accuracy of the US radionavigation system Deep Space Network including a network of antenna complexes with antenna diameters from 26 to 70 m. It is also shown that on the basis of the proposed method of absolute navigation a system of relative navigation providing rendezvous of two spacecrafts in a lunar orbit can be realized, which differs from the existing systems of rendezvous by simplicity of realization, low weight, power consumption and cost.