Research On Orbit Determination And Time Synchronizing Of Navigation Satellite Based On Crosslinks

In order to enhance the ability of navigation battle, and meet the requirement of solving the limit of the regional monitoring station net, it is a general tendency to build Inter-Satellite Links (ISL) in the next generation of the global navigation satellite system (GNSS). This dissertation mainly studies the approaches of satellite orbit determination and time synchronization based on ISL, for the purpose of realizing the optimal estimation of satellite orbital parameters and clock error with engineering constraints. Two of the key problems, i.e. space-ground-based integrated estimation and distributed autonomous navigaition (AutoNav), are solved in this dissertation. The main results achieved in this dissertation are summarized as follows.(1) The conceptual design and analysis for navigation constellation with ISL are carried out. The architecture of multi-layer links of navigation constellation is studied and designed. The data processing flow for AutoNav is designed particularly. The principle of Dual-One-Way Messament for ISL is researched, and the error sources of ISL measurements are summarized systematically. The flow of preprocessing inter-satellite measurements is described. After analysing the dynamic topological structure of ISL, a method of estimating AutoNav Error (ANE) is proposed based on the satellite positioning principles.(2) The space-ground-based combined estimation theory, methods and approaches for navigation constellation are studied and proposed. Base on the analysis of satellite orbit and clock error processing in Master Control Station (MCS) supported by ISL, the space-ground-based combined batch processing of orbit determination for the whole net is studied and proposed, which combines the integrated adjustment principles and the combined orbit determination theories. The algorithm of real time orbit determination and time synchronization for the whole net are studied in terms of engineering realization, thereby the UD factorizing Extended Kalman Filter (UD-EKF) of numerical stability for the whole net is presented. The robust M estimations and adaptive filters are introduced in the combined estimation to design the adaptively robust filtering with multiple adaptive factors. The results indicate that, the proposed approaches can solve the limit of regional monitoring station net, realize continuous precise estimation of orbit and clock error; and also restrict the modeling errors and faulty measurements.(3) The distributed AutoNav algorithms are studied. Several distributed filters based on EKF are proposed and researched after analysing the observation equations which are made up of inter-satellite measurements. The error covariance analysing theory is introduced to compare the transient and steady-state covariances of the estimated states. It is found out that, the Increasing the measurement error variance matrix R EKF (IREKF) is suitable for UHF ISL and the SKF suitable is for Ka ISL. The distributed autonomous time synchronization algorithms are proposed. The distributed Satellite Autonomous Integrity Monitoring (SAIM) algorithms are researched. The distributed adaptively filters based on predicted residuals are put forward to deal with the reduced dynamic models. The simulation results show that the proposed algorithms can meet the precision requirement of long-time AutoNav.(4) One of the key problems, the Ephemeris observability issues in AutoNav, is studied. This problem is mainly described by the orientating parameters of the Keplerian elements, so it is also viewed as an orientational problem. The precise predicted EOPs are investigated. The other cause, i.e. the constellation orientating in inertial system, is explained in three aspects. The observability analysis method based on Singular Value Decomposition (SVD) theory is introduced for qualitative analysis of AutoNav observability. Several approaches for orientation with engineering constraints are studies. The investigation indicated that, the semi-autonomous navigation strategy based on ground-based anchor is engineering realizable.(5) The X-ray Pulsar-Based Navigation technology used in navigation constellation AutoNav is studied from the perspective of the integrated navigation. The dual-rate kinematic and static filter is designed. The positioning precision based on X-ray Pulsar is analyzed, from which the approach of using X-ray pulsars for aiding the navigation constellation AutoNav is put forward and studied. The proposed integrated navigation method can improve the AutoNav precision, and solve the orientational problem partly.This dissertation expands the research domain of the traditional orbit determination theory,which has some theoretical significance. The developed theory, methods and approaches, combined with engineering constraints, can promote the applications of optimal estimation theory and methods in GNSS, which has some application value.