Autonomous Orbit Determination Of Navigation Constellation Based On Crosslink Range And Orientation Parameter Constraint

Autonomous navigation of navigation satellite is a distinctly important aspect to enhance the survivability of navigation system. And the orbit precision is one of the main factors to judge its quality. In this paper, some sticking points of the key techniques in navigation constellation's autonomous orbit determination, such as long-term orbit forecast with high precision, algorithm for constraining constellation's direction and algorithm of orbit estimation, are studied. Followings are the main study in this paper.1. The theory and methods of autonomous orbit determination are systematically expounded, including time system, coordinate system, dynamic model and numerical mothod of satellite motion equation. Long-term orbit forecast's precision depends mainly on dynamic model's error. In view of navigation satellite, the influence of all perturbation forces is analyzed. Considering the orbit determination precision and computational efficiency, main perturbation forces are included.2. Two kinds of nonlinear filter algorithms EKF and UKF are emphatically presented. In view of the calculation divergence problem, SREKF and SRUKF are put forward. And these two algorithms are compared by using the simulation example.3. Considering satellite moving in high elliptical orbit, such as navigation satellite, the problem how to choose the state variables in the process of autonomous orbit determination is discussed. Considering the real-time request of orbit determination, orbital elements are selected as state variables. Besides, also considering the characteristic of near-circular orbits of navigation satellites, nonsingular orbital elements are selected as state variables.4. Measurement model based on crosslink range is established. The viewpoint that there exists the rank defect problem caused by only using crosslink range observations in aspect of adjustment processing is proved. Besides fully considering the prior orbital information of each satellite, orbit estimation algorithm is utilized to fuse crosslink range data and satellite orbital dynamic information, and it can modify integral parameters timely and determine the satellite position and velocity vectors of the whole constellation.5. Long-term orbit forecast information contains the evolution characteristics of satellite orbit. Therefore, if the orbit forecast information is fully considered, the influence of constellation's free drifts to the orbit determination precision can be reduced effectively. Consequently, algorithm for constraining constellation's direction is proposed.6. The state transition matrix is sovled by using the numerical method and analytical method separately, and both results are compared. Results indicate that the analytical method can fully meet the needs of orbit determination precision. Consequently, the improved SREKF algorithm is put forward. In comparison with the SRUKF algorithm, the proposed algorithm is verified to have the advantages of high precision and high efficiency.