【摘 要】
：
Two-way satellite time and frequency transfer (TWSTFT) using geostationary telecommunication satellites has proven to be one of the most appropriate means of comparing time scales and atomic frequency
【机 构】
：
National Time Service Centre, Chinese Academy of Sciences, Xi'an 710600, China Key Lab. Of Time & F
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Two-way satellite time and frequency transfer (TWSTFT) using geostationary telecommunication satellites has proven to be one of the most appropriate means of comparing time scales and atomic frequency standards with an un-certainty less than 1ns.Thispaper analyses what the mainly errors sources of TWSTFT.And then,aim to the current calibrated accuracy levels of ground stations delay are key factor what limits TWSTFT performance improving.A new method is used to calibratelink delay of TWSTFT based on double portable stations that has been proposed.A set of double-portable stations (DPS) has been developed.Toevaluate the performance ofDPS,a compare and test platform has been designed including DPS,fixed ground stations of TWSTFT,fiber-basedlinks.When the distance of two compared clocks arearound 60 km.The DPS andfiber-links are tested synchronously.The measurement results show that the systematic deviation of DPS is less than 0.1ns,and the standard deviation is less than 0.2ns.When the distance between two sites is around 3000km,DPS compare with fixed ground stations,the standard deviation of the differencebetween the two systems measurement resultsare less than 0.3ns.So we can get conclusion,theDPScali-brates links delay that the uncertainty of calibratingachieves less than 0.5ns.It is helpful to improve the performance of TWSTFT.
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