基于脉冲星观测的原子时波动检验研究

Research on variation test of atomic time based on pulsar observation

脉冲星时(pulsar time,PT)具有较高的长期稳定性,其与原子时(atomic time,AT)的建立属于两个完全不同的物理过程.因此,脉冲星时可作为原子时波动的一种独立检验方式.本文结合真实钟差数据,展示了基于脉冲星时的原子时波动检验结果.首先,给出了Parkes脉冲星计时阵(Parkes pulsar timing array,PPTA)发布数据中四颗毫秒脉冲星的计时结果.为进行原子时波动的检验,利用四颗脉冲星的计时模型参数,仿真生成以地球时(terrestrial time,TT)(BIPM19)为参考的脉冲到达时间(pulse times of arrival,TOAs)数据,然后将参考时由TT(BIPM19)改为TT(TAI).基于此,分别采用经典加权平均算法与维纳(Wiener)滤波算法提取了原子时相对于脉冲星时的波动.将两种方法得到的检验结果进行对比,结果表明Wiener滤波算法对原子时波动的提取效果优于加权平均算法.本文在Wiener滤波算法提取钟差信号的基础上加入了小波阈值去噪算法以扣除高频噪声,去噪后PT更接近于TT(BIPM19),进一步提高了PT对AT波动的检测能力.对于TOA测量精度为100 ns的情况,PT与TT(BIPM19)的差值大致保持在40 ns以内.本文是在给定TOA测量精度的前提下研究进一步提高PT精度的方法,对下一步PT更加有效的守时应用具有重要意义.

Pulsar time(PT)has high long-term stability,and its establishment process is completely different from that of atomic time(AT).Therefore,pulsar-based time scale can be used as an independent test for the fluctuation of atomic time scale.In this paper,the test results of the fluctuation of atomic time using pulsar time are presented in combination with the real clock difference data.In order to test the fluctuation of atomic time,the timing model parameters of four pulsars are used to simulate the pulse times of arrival(TOAs)data with TT(BIPM19)as the reference,and then the reference time is changed from TT(BIPM19)to TT(TAI).Based on this,the classical weighted average algorithm and the Wiener filtering algorithm are used to extract the variations of the atomic time relative to the pulsar time.The test results obtained by the two methods are compared,and it shows that the Wiener filtering algorithm is better than the weighted average algorithm for the extraction of the fluctuation of the atomic time.The wavelet threshold denoising method is added to the clock difference signal extracted by the Wiener filtering algorithm to deduct the high-frequency noise.After denoising,PT is closer to TT(BIPM19),which further improves the ability of PT to detect the fluctuation of AT.For the TOA measurement accuracy of 100 ns,the difference between PT and TT(BIPM19)can be kept roughly within 40 ns.This paper studies the method of further improving the accuracy of PT under the premise of given TOA measurement accuracy,which is of great significance for the next step to use PT for more effective application of time keeping.