The Studies Of Observational Strategies For Establishing Pulsar Clocks And Timing Noise Analysis

Millisecond pulsars have extraordinary stable spinning,so they can be used as fre-quency source to generate pulsar time-scale.From the timing observation of one mil-lisecond pulsar,the sequence of times of arrival can be acquired to construct a pulsar clock.Noises emerge in pulsar clocks because pulsar spinning and signal propagation are affected by various factors.These noises not only reduce the accuracy and stability of pulsar clocks but also restrict their applications,making observational strategy such as observational cadence(average time between observations),data span a constraint for the stability of pulsar clocks.In practical observations,almost every radio telescope is mission-diverse,which also make observational strategy a concrete problem.The study of the effects of observational strategy on pulsar clocks is of great importance for constructing pulsar clocksThis paper studied the effects of observational strategy on the stability and tim-ing model parameters of pulsar clocks constructed by the best four pulsars in the first data released by the International Pulsar Timing Array(IPTA).The results show that observational cadence do not affect the stability and timing model parameters of the four pulsar clocks unless the observation is too sparse.On the other hand,the relation between the stability of pulsar clocks and data span is complicated under the existence of red noise.Hence when intensive observation can not be guaranteed,it is acceptable to enlarge the observational cadence if noise standard of the data is on the same level with the four pulsars in this studyApart from pulsar clocks themselves,observational strategy could also make im-pacts on the accuracy and stability of the predictions made by timing models.Selecting the later data of the four pulsars above as the observations to be predicted,and con-structing pulsar clocks by using the former data,the effects of observational strategy on predictions can also be studied.Results of analysis show that if the data to construct pulsar clocks is adjacent to the observations to be predicted,the accuracy and stability of predictions made by pulsar clocks constructed under different observational strate-gies would not deviate obviously if observational cadence is not very large or data span is not too short;however if the data to construct pulsar clocks is far away from the ob-servations to be predicted,predictions would go worse.On the other hand,although the weighted root mean square of the residuals would increase if the data to be predicted extending to a longer span,the stability would not be worse.This paper also points out that dispersion measure would affect the predictions greatly if the data to construct pulsar clocks is far away from the observations to be predicted,which indicates that in this situation dispersion measure should be corrected by the real observations.In addition,this paper analyzed the effects of timing noise model parameters on the stability of pulsar clocks by using simulated data,and the impacts of noise corrections on the stability of pulsar clocks based on the real data of IPTA.All the results could give some guidances for constructing pulsar clocks.