Schmidt Kalman filter in autonomous orbit determination of navigation satellites
To further improve the accuracy of autonomous orbit determination(AOD)of BDS navigation satellites with the equivalent observation Kalman filter, the Schmidt Kalman filter algorithm is applied, considering the cross covariance informa-tion between two correlated satellite states of the inter-satellite link observation. The formula for the measurement update and time update of Schmidt Kalman filter according to the observation one by one is deduced, and the square root filtering is also used to ensure the positive definite of the covariance matrix of state variable.The simulation and observed data test result of au-tonomous orbit determination shows that the Schmidt Kalman filter algorithm can perceptibly improve the AOD accuracy com-pared with the equivalent observation Kalman filter.