Study on differential phase delay closure of same-beam VLBI

The paper focuses on verifying the differential phase delay model and detecting and correcting the cycle ambiguity existed in the differential phase delay data of same-beam VLBI. We confirmed the methods of calculating the phase delay closure and the differential phase delay closure with the same wave front. We used 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 was less than several picoseconds. The method can be used to verify the same wave front differential phase delay model and to detect and correct the cycle ambiguity existed 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 science research and to process same-beam VLBI data in real-time for navigation.