Measurement of atmospheric non-reciprocity effects for satellite-based two-way time-frequency transfer

Future optical clock networks will require high-precision optical time-frequency transfer between satellites and ground stations. However, due to atmospheric turbulence, satellite motion and time delay between the satellite–ground transmission links will cause spatial and temporal variations, respectively, resulting in the breakdown of the time-of-flight reciprocity on which optical two-way time-frequency transfer is based. Here, we experimentally simulate the atmospheric effects by two-way spatio-temporally separated links between two stationary terminals located 113 km apart and measure the effects for optical two-way time-frequency transfer. Our experiment shows that the effect on the link instability is less than 2.3×10 −19 at 10,000 s. This indicates that when the link instability of satellite–ground optical time-frequency transfer is on the order of 10 −19 , it is not necessary to consider the atmospheric non-reciprocity effects.