Testing gravitational redshift based on microwave frequency links onboard the China Space Station
Wenbin Shen, Pengfei Zhang, Ziyu Shen, Rui Xu, Sun Xiao, Mostafa Ashry, Abdelrahim Ruby, Wei Xu, Kuangchao Wu, Yifan Wu, Ning An, Lei Wang, Lihong Li, C. Cai
Abstract
In November 2022, the China Space Station (CSS) was equipped with a cold atomic microwave clock and a Sr optical lattice clock with stabilities of $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}/\sqrt{\ensuremath{\tau}}$ and $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}/\sqrt{\ensuremath{\tau}}$ (where $\ensuremath{\tau}$ is the integration time in seconds), respectively, which provides an excellent opportunity to test gravitational redshift (GRS) with higher accuracy than previous results. Based on high-precision frequency links between the China Space Station and a ground station, we formulated a model and provided simulation experiments to test GRS. Simulation results suggest that this method could test the GRS at the accuracy level of $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$, more than 2 orders in magnitude higher than the result of the experiment of a hydrogen clock on board a flying rocket more than 40 years ago.