Integrating satellite-to-satellite tracking with star tracker navigation for satellite constellation at earth-moon L2 point

Constructing a satellite constellation with autonomous navigation at the Earth-Moon L2 libration point for deep space exploration has been studied extensively in recent years. The accuracy of satellite-to-satellite tracking (SST) orbit determination is poor due to the unknown model error caused by perturbation and abnormal measurement. An Integrated navigation scheme of SST with star tracker (ST) for satellite constellation at earth-moon L2 point is designed. The range, Doppler information of SST and the angle information between the constellation satellites and the moon of the ST are fused together. Then, a federated adaptive square-root cubature Kalman filter (FASCKF) is developed to improve the accuracy of autonomous orbit determination by introducing an adaptive-scale matrix to adjust the measure covariance under abnormal measurement. The simulation results show that the position error and velocity error of the FASCKF are reduced by 68.85% and 44.17% respectively compared with the federated square-root cubature Kalman filter.

Conclusion

With the study and exploration of the moon and deep space, a lunar navigation system is necessary. Considering the specific properties of the libration point orbits, it is attractive to construct a satellite navigation constellation at Earth-Moon L2. To solve the navigation problem for the satellite constellation itself, and to be robust against perturbations, the FASCKF based SST and ST navigation scheme is proposed in this paper. Simulation results verify that the proposed navigation scheme outperforms SST-only and ST-only in navigational accuracy, stability, and convergence rate. In designed case with measurement fault, the FASCKF method can effectively cope with the measurement faults, and keep generating accurate and stable results, the same as during normal conditions.