LEO real-time orbit determination and time-frequency synchronization method based on PPP-B2b signal

The invention discloses an LEO real-time orbit determination and time frequency synchronization method based on a PPP-B2b signal. According to the method, the motion equation and the observation equation are established respectively, the precise orbit of the low-orbit satellite is determined in real time by adopting a two-step method of integral forecasting and filtering updating, a root-mean-square information filtering algorithm is used in the filtering updating process, the divergence problem of numerical calculation of a traditional Kalman filtering method is avoided, and the calculation efficiency is improved; determining a navigation satellite orbit and a clock error through a polynomial fitting method for solving the problem that a satellite-borne receiver cannot acquire a segmental arc of a PPP-B2b signal due to earth shielding; for the condition that the observation value of the satellite-borne receiver is insufficient, the orbit of the low-orbit satellite is obtained by adopting the extrapolation of