【作者】 许龙霞；

【导师】 李孝辉；

【作者基本信息】 中国科学院研究生院（国家授时中心） ， 测试计量技术及仪器， 2012， 博士

【摘要】 时间与人们的生活密切相关，人们将利用无线电波播发标准时间信号的工作称为授时。从故至今人们在不断地探索获取时间的新方法，从最初以声音为媒介的晨钟暮鼓发展到使用光信号的落球报时，再发展到目前以无线电波为载体的各种授时方法。授时精度也随之不断地提高，目前精度最高的授时方法为基于卫星导航系统的单向授时方法，最高精度约为15ns。对于航天、导弹领域的纳秒级授时精度的需求用户只能使用如共视时间传递、卫星双向时间频率传递等高精度时间比对方法。这些高精度时间传递方法的成本高，且只能实现少数用户间的时间同步，因此，迫切需要研究高精度的授时方法。本文将共视时间传递方法进行扩展，将共视原理应用于卫星授时，提出了基于共视原理的卫星授时新方法，可以提供3~5ns的授时精度。本文围绕共视授时新方法，开展了以下几个方面的研究：（1）提出了一种基于共视原理的卫星授时新方法虽然基于GNSS的共视时间传递方法可以实现纳秒级的时间同步，但共视与授时有着本质区别。授时要求实时地为用户发播标准时间信号，服务的用户数量不限，而共视只实现了少数用户之间的时间比对，且具有滞后性。本文提出的基于共视原理的卫星授时新方法，在主站监测卫星广播的系统时间与标准时间UTC(NTSC)的时差，并将授时偏差广播给用户。用户接收使用后，相当于与主站共视相同可见星，获得标准时间UTC(NTSC)，实现授时。（2）试验验证了共视授时新方法的原理为验证共视授时新方法的原理和可行性，本文搭建了原理验证系统。基于验证系统开展了零基线、短基线和长基线比对试验。零基线和短基线试验数据结果验证了共视授时方法的原理和可行性。通过与卫星双向时间比对的结果进行比较，扣除长春临潼两站钟差的影响，长基线比对结果验证了共视授时的原理。（3）提出虚拟共视基准站技术，应用在共视授时新方法中虚拟共视基准站技术利用了星历误差、电离层误差的空间相关性，综合利用多个基准站的观测数据，按用户与基准站的位置关系内插得到用户附近的虚拟基准站的观测数据，与用户观测量形成近零基线差分，解决用户远离基准站时，获得的授时精度下降的问题。论文针对提出的虚拟共视基准站技术，研究了不同基准站个数、不同的权值确定方法对用户授时精度的影响。制定了用户选择基准站的原则，确定了用户端虚拟改正量生成算法，分析了站间时间同步误差对共视授时精度的影响。（4）研究了授时偏差的变化特点及授时数据的广播方法为保证实时性和用户容量，需要研究授时偏差的变化规律，建立适当的模型，实现对用户的实时广播。本文研究了3种适用于授时偏差的广播方法①通信卫星，可实现实时广播；②互联网，事后发布授时偏差数据文件；③短信查询，实时响应用户查询，为用户返回指定时刻的数据。（5）制定共视授时系统的实施方案设计了共视授时系统的总体架构，制定了共视授时系统的实施方案。按功能将系统划分为单元，并对每个单元进行了初步的规划和设计。更多还原

【Abstract】 Time is closely related to people’s daily life. The work of broadcasting standardtime signal is called time service. In ancient time, sound is used to provide timeservice, such as beating bell and drum, and then light is used. Today, most timingmethods are based on radio wave with improved accuracy. Currently, the accuracy ofone-way timing method can reach about15ns.For users of nanosecond requirement of accuracy can only turn to common viewtime transfer and Two Way Satellite Time and Frequency Transfer methods. However,these methods need high cost equipments and only can be applied to few users. Allthese limitations compel us to advance a new timing method.Based on the analysis of both one-way timing method and common-view timetransfer, a new common-view based one-way timing method is proposed which canprovide accuracy of3~5ns. This paper focuses on this method and mainly discussesthe following aspects.（1）Proposal of the new timing method.Time service is different from common view in essence. As a timing method, itrequires disseminate timing signals in real time for mass users. While common viewcan only realize the time comparisons between fewer users after data exchange.The method overcomes these shortcomings by monitoring timing signal ofsatellites with receivers located at master station and then broadcasting to users. Thisequals to observe the same satellites with users. These data are used to correct the userreceiver’s measurements after received. Finally, the local time of users aresynchronized to the standard time UTC(NTSC).（2）Experiment verification of the new method.In order to testify the feasibility of the new method, a test platform is set up. Thezero-baseline experiment, short-baseline experiment and long-baseline experiment arecarried out based on it. The results of zero-baseline and short-baseline experimentsvalidate the feasibility of the new method. Influenced by the longer baseline and theunknown time difference between two Changchun and Lintong stations, the result oflong-baseline experiment is affected by the correction error of ionosphere delay andother space-related errors.（3）Proposition of the virtual common-view reference station technology. According to locations of users and reference stations, the relativity of ephemeriserrors and ionosphere delay errors are explored by Virtual Common-View ReferenceStation technique (VCVRS) for interpolating the observations of a non-existedreference station close to user. This method makes use of measurements of serveralreference stations and solves the problem of decreasing accuracy with the increasingdistance between user and reference stations.Some further researches about VCVRSare discussed. Firstly, the effects of different reference station number and differentmethods of weight determination on timing accuracy of the new method are studied.The fundamentals for users choosing reference stations are established and the impactof time synchronization errors is analyzed after that.（4）Research on the changing characteristic and broadcasting methods of timingdataTo ensure the real time and user capacity, the modeling and broadcasting oftiming data must be considered. Three methods are provided for data dissemination.The first one is based on communication satellite which is used to broadcast timingmodel parameters for users in real time. Internet is the following one which releasetiming data files each day for user’s download. The last one is short message enquirewhich waits the query command of users and then response.（5）Scheme design of the new timing system.The whole system of common-view based timing method is planed and designed.The detailed design of each part is also layout.更多还原