Measurement of the geopotential difference between two sites at Beijing and Wuhan using two hydrogen clocks via CVSTT technique

Based on the gravity frequency shift equation, by comparing the frequencies between two precise clocks at two different stations at the 203 Institute Laboratory (in Beijing) and the Luojia Time-Frequency Station (in Wuhan), respectively, the geopotential difference between the two stations is determined. Here, we conduct a clock-transportation experiment for measuring the geopotential difference between the two stations by comparing two remote hydrogen atomic clocks’ frequencies via satellite links. Based on the gravity frequency shift measured between the two remote clocks at Beijing and Wuhan, the geopotential difference between the two stations was determined. Comparisons show that the experimental result deviates from the EGM2008 result by 38.5(45.7) meters in orthometric height. The results are consistent with the frequency stabilities of the hydrogen clocks (at the level of 10⁻¹⁵@day) used in the experiment. With the rapid development of time and frequency science and technology, the approach discussed in this study for measuring the geopotential is prospective and thus, could have broad applications. This study is supported by the National Natural Science Foundations of China (Nos. 42030105, 41721003, 41804012, 41631072, and 41874023), Space Station Project (No.2020-228), and the Natural Science Foundation of Hubei Province of China (No. 2019CFB611).