Calculation and Analysis of Same Beam VLBI Differential Phase Delay Closure of Lunar Satellite

The paper focuses on verifying the differential phase delay model,detecting and correcting the cycle ambiguity existing in the differential phase delay data of same-beam VLBI. We confirm the methods of calculating the phase delay closure and the differential phase delay closure with the same wave front.We use the method to analyze the differential phase delay data of the same-beam VLBI from SELENE project.The result of the differential phase delay closure is less than several picoseconds.The method in the article can be used to verify the same wave front differential phase delay model,to detect and correct the cycle ambiguity existing in the differential phase delay data.It can also be used to monitor the fluctuations of the differential phase delay.These results are very useful to select the data for scientific research and to process same-beam VLBI data in real-time for navigation.