Research On Deep Space Autonomous Navigation Scheme And Application To Small Celestial Bodies Exploration

As a key technology, the autonomous navigation influences directly the mission's success. Spacecraft autonomous navigation can reduce the operational complexity of the ground-assisted system, and extends the potential space application. With the supports of National Natural Science Foundation of China'Theory and Method of Deep Space Autonomous Navigation', this dissertation deeply studies the autonomous navigation scheme according to the characters of different spaceflight stages. The main contents of this dissertation are as follows.Firstly, the observability analysis methods of the deep space autonomous navigation system are studied. Considering the environmental characters of deep space, the corresponding surfaces of spacecraft position with different measurement information are given utilizing the geometry method. By taking the partial derivatives of the measurement with respect to each state variable, the observability of the autonomous navigation system is analyzed qualitatively. The quantitative analysis of the observability, including the observability and observable degree, are carried out through the observability matrix, error variance matrix, and FIM (Fisher Information Matrix).Secondly, the autonomous navigation scheme of the interplanetary cruise phase based on asteroid image is studied. Navigation measurement model is constructed as the Line-of-Sight (LOS) vectors, and the observability of autonomous navigation system is investigated by analyzing the FIM. After given the selection criteria, the navigation asteroid is chosen according to the observable degree defined by the FIM. The spacecraft orbit is determined by using the recursive weighted least square based on UD factorization. Considering the attitude determination from the stars contained in asteroid image, a fast optimal attitude estimation algorithm is presented.Next, the autonomous navigation scheme of the cruise phase based on the Sun observation is studied. For the autonomous navigation system utilizing the Sun LOS vector, an initial orbit determination algorithm utilizing three LOS vectors measurement is given based on observability degree analysis. After that, the autonomous navigation method introduced the radial velocity is researched. Furthermore, the autonomous navigation method based on the LOS vector is studied from the combination of the Sun LOS vector and the optical information, and an autonomous navigation algorithm of information fusion based on observability degree is given. Based on investigating the attitude estimation error using vector observation, the application of the Sun LOS vector in the optimal attitude estimation is studied.Then, the autonomous navigation scheme of the rendezvous phase for small celestial body is studied. The state equation and measurement equation of the approach phase are constructed, and the observability of the navigation system is investigated qualitatively by using the analytical method. Considering the ephemeris information of the target celestial body, the autonomous navigation method based on the relative LOS vector and the Sun LOS vector are studied respectively. For the rendezvous phase, the RSEN (Reduced State Encounter Navigation) of the relative motion is given. The relative position vector is deduced under the different previous situation of the relative velocity, and the relative navigation method based on the LOS vector is researched.Finally, the autonomous navigation scheme of the circling phase and landing phase are studied. For the circling phase, an autonomous navigation method based on the vector observation of the limb feature points of small celestial body is proposed. Combining the shape model, the relative position and attitude of the spacecraft in the small celestial body fixed coordinate frame are deduced directly, and an autonomous navigation algorithm using the Gauss-Markov process and Unscented Kalman filter is presented. For the landing mission, an autonomous navigation method based on vector observation of the feature points on the surface of the target small celestial body is studied. The position vectors from the spacecraft to three feature points can be constructed from the measurements of optical camera and laser range finder. The landing site coordinate frame and the spacecraft relative position and attitude are constructed directly. The spacecraft orbit parameters are determined by using the extended Kalman filter.