Research On Autonomous Navigation Scheme For Probesaround Mars

Autonomous navigation techniques are proposed as a solution to the problem of navigating in deep space exploration with features of real-time, high stability, and it has gradually applied to a series of practical tasks in deep space exploration abroad. In China’s deep space exploration plan, the development of autonomous navigation technology has become an important research direction. The dissertation focus on the autonomous navigation method for deep space probes around Mars.At first, the dissertation establishes the appropriate time system and coordinate systems based on the requirement of task, then the transformations between different coordinate systems are calculated, while the ephemeris of the sun and Mars natural satellites are calculated, the dynamic model is given in the Mars inertial coordinate system with considering various perturbation factors as Mars Non-spherical gravitational perturbation, sun and Mars natural satellites gravitational perturbation, the resistance of the air, the solar radiation pressure, the errors which are generated when compared with the STK’s reference model verify the accuracy of the dynamic model.Then the observing conditions are taken into consideration to simulate the measurement data correctly as the Mars shelter,the Mars shade, the Sun backlighting condition. Corresponding specific equations are given and simulations are taken to analyze the affections of each observing condition on observations arc. The simulation results show that the main factors of visibility can be attributed to the positional relationships among the goal, Mars and the sun.This paper analyzes the observability of the navigation system. For the probes around Mars, the observability of the nonlinear navigation system is studied through analyzing the independence of the partial derivative equation of the observables pertaining to the state variables, and the observable degree is carried out through the observability matrix. Then the optical autonomous navigation system taking the sight vectors of the beacons as the observables of Mars satellites is analyzed, which processed multiple sets of measurement data with using least square algorithm, and then orbital elements of probes around Mars is calculated with using Newton iterative, while the navigation method based on the landmarks on the surface of Mars which are known the geographical features is researched. Finally, the dissertation analyzes some factors such as the orbital altitude, sampling period, the number of sampling points, measurement noise, and navigation beacon, which might affect the accuracy of orbit determination by comparing simulation, and then predict the orbit with the result of initial orbit determination, at last analyzes the error propagation.