Research On Autonomous Navigation Methods Of Asteroid Exploration's Encounter Phase

In recent ten years, countries all over the world have launched numbers of deep space probes to explore various kinds of valuable celestial bodies in the solar system. In deep space exploration missions, autonomous navigation technology is very important, and in this paper, we do some research into the autonomous navigation schemes of encountering small celestial bodies. It is mainly described as the follows:Firstly, by analyzing the orbit characteristics and task requirements in encounter, The simplified orbit dynamic model for the deep space probe is built up, and whether the corresponding model error that meets the demanding of autonomous navigation task is validated. Secondly, based on the existing international technologic analysis, two different measurement schemes are proposed. One navigation scheme uses pixels as measurements vector, and the other one uses line of sight (LOS) of object celestial body and angles from probe to object body as the measurements vector.Thirdly, the analysis method for nonlinear system using rank factor of observability and singular value decomposition are proposed, and navigation observability is analyzed. At the same time, we use Kalman filter error equations in errors analysis for autonomous navigation algorithm, and compare the analysis results of the two methods.Finally, based on the observability analysis and error analysis, two autonomous navigation schemes for encounter phase are respectively proposed in detail. Monte Carlo simulations are done for the two schemes. By analyzing and comparing the simulation results, we can get the conclusion that, under the accuracy conditions provided by the instruments in existence, the position estimation accuracy for probe encountering object celestial body is 0.42km and 0.04km, which demonstrate the feasibility of the two navigation schemes.