Determining the gravity potential with the CVSTT technique using two hydrogen clocks

TL;DR

This study demonstrates a novel method using hydrogen clocks and CVSTT technique, enhanced by EEMD, to determine geopotential differences with high precision, promising future applications in geodesy.

Contribution

First application of EEMD to CVSTT data for geopotential determination using hydrogen clocks, improving signal extraction and measurement accuracy.

Findings

Geopotential difference between two stations measured with hydrogen clocks.

Comparison shows deviation within measurement uncertainties.

Results align with existing gravity models and clock stability levels.

Abstract

According to general relativity theory (GRT), by comparing the frequencies between two precise clocks at two different stations, the gravity potential (geopotential) difference between the two stations can be determined due to the gravity frequency shift effect. Here, we provide experimental results of geopotential difference determination based on frequency comparisons between two remote hydrogen atomic clocks, with the help of common-view satellite time transfer (CVSTT) technique. For the first time we apply the ensemble empirical mode decomposition (EEMD) technique to the CVSTT observations for effectively determining the geopotential-related signals. Based on the net frequency shift between the two clocks in two different periods, the geopotential difference between stations of the Beijing 203 Institute Laboratory (BIL) and Luojiashan Time--Frequency Station (LTS) is determined. Comparisons show that the orthometric height (OH) of LTS determined by the clock comparison is deviated from that determined by the Earth gravity model EGM2008 by (38.5$\pm$45.7)~m. The results are consistent with the frequency stabilities of the hydrogen clocks (at the level of $10^{-15}$~day$^{-1}$) used in the experiment. Using more precise atomic or optical clocks, the CVSTT method for geopotential determination could be applied effectively and extensively in geodesy in the future.