Geopotential determination based on a direct clock comparison using two-way satellite time and frequency transfer

  • Author(s): Wen-Bin Shen, Xiao Sun, Chenghui Cai, Kuangchao Wu, and Ziyu Shen
  • DOI: 10.3319/TAO.2018.07.09.02
  • Keywords: General relativity, TWSTFT, Geopotential, Atomic clock, Height difference
  • Approach for determining geopotential using time signals was proposed
  • TWSTFT technique was used to transfer time signals
  • Experimental results demonstrated the feasibility of the proposed approach

According to Einstein’s general relativity theory, a precise (atomic) clock runs faster at a position with higher gravitational potential than a clock at a position with lower potential. Here, we provide a direct clock comparison using a fixed hydrogen clock and a portable hydrogen clock for geopotential determination based on the two-way satellite time and frequency transfer (TWSTFT) technique. After synchronizing the two hydrogen clocks at positions at the same height, the clocks were compared for a height difference of 22 m over a period of 14 days using the TWSTFT technique. Interpretation of the observed time elapse implies a height difference of 175 m +/- 59 m, which matches the frequency stability of our instruments. This study and relevant experiments provide a way of determining the geopotential using ultra-high precise clocks based on the TWSTFT technique in the near future.

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