Abstract: To establish steady relative navigation between two spacecraft in lunar orbit rendezvous and docking, accurate relative state determination between two spacecraft is needed in the long range ground based navigation. Same beam interferometry (SBI), as a high precision technology for relative angle measurement, is of great sigficant in the relative state determination. However, the systemmethodforanalyzing the influence of SBI on the relative states of two spacecraft in lunar orbit rendezvous was not developed. The information matrix of measurements with the relative states was deduced according to the covariance theory, and the model of the relative states error covariance was established. The simulation results show that the relative position and velocity errors are within the meter and millimeter per second under the current range, range rate, VLBI and SBI measurement errors. The error and its influence was obtained, and the influence of cycle ambiguity error on relative state error was analyzed. The resutls show that the cycle ambiguity of SBI reduce from 2 to 0, andthe relative position error on T and N is decreased greatly.

Key words: Same Beam Interferometry, Relative states, Error covariance analysis, Rendezvous and docking, Lunar exploration