时间:天文时-原子秒-基于常数重新定义秒

Time:Astronomical time-atomic time-redefining second based on constant

本文简略回顾现代时间从天文时到原子秒的变革历程.简述铯冷原子喷泉频率基准复现现行秒定义的进展和现状,国际原子时(TAI)和国际通用的协调世界时(UTC)产生过程,以及国际上关于放宽对协调世界时和一类世界时UT1之差的趋势.接着介绍原子喷泉频率基准常规驾驭TAI的现状,国内外光学频率标准(简称光频标)研究的进展,以及迄今6台光频标参与驾驭TAI.依据国际正在讨论的未来修改秒定义路线图,分析常规驾驭TAI对光频标的要求和对策.在此基础上,提出基础研究型和计量型两种光学频率标准研究定位,并针对计量型光频标的性能指标提出建议.提出对不确定度达到3×10^(−17)的计量型光频标频率评定要求,不仅应计及相对论静态重力频率频移,而且应考虑动态潮汐频移.最后建议利用两台高稳定光频标,跨越大经度距离实施频率比对,实验测量直接验证相对论潮汐频移的方案.

The evolution history of modern time from the astronomical time to the atomic second is briefly reviewed herein.The progress and status of realizing the current definition of the second using cesium cold atomic fountain primary frequency standards,the process of generating the international atomic time(TAI)and coordinated universal time(UTC),and trend of releasing the tolerance on inserting leap-seconds into the UTC are sketched.The present situation on steering the TAI regularly from January 2016 by cesium fountain frequency standards from five countries is reported.Research progress of local and global optical frequency standards is summarized,and steering TAI by six optical frequency standards starting from 2016 is reported.Requirements and responses on steering TAI regularly by optical frequency standards are introduced according to the roadmap,which is under discussion internationally,or the future redefinition of the second.Furthermore,two types of optical frequency standards,namely the basic-research and the metrological type are suggested,and the performance and technical qualifications for the metrological type of optical frequency standards are recommended.For the optical frequency standards of the metrological type,with uncertainties better than 3×10^(−17),not only static relative gravity but also the alternative tide frequency shifts should be considered in their frequency evaluations.Finally,a scheme employing frequency comparison,across a long longitude-distance,between two highly stable optical frequency standards to demonstrate the relativistic tidal frequency shift directly and experimentally is proposed.