Research On Estimation Algorithm Of Atomic Clock Frequency Deviation Based On Pulsar

Pulsars are rapidly rotating compact stars.Their rotation is highly stable,so the radiated electromagnetic waves form significant periodic signals.With the discernibility of their pulse profiles,pulsars become the natural frequency reference in the universe.At present,the ground and space time reference are maintained by atomic clocks.The maintenance of local time UTC(k)depends on international time transfer data.The pulsar timescale(PT)is a time scale generated by the rotation of natural celestial bodies,which is expected to solve the problem of independence and safe reliability in time service.Pulsars have multi-band radiation characteristics,so their continuous and stable periodic signals can serve users on the ground and in space.The combined observation of signals in X-ray and radio band will provide powerful support for the long-term and high-precision maintenance of future deep space time systems.In recent years,hydrogen maser plays an increasingly important role in time-keeping.The pulsar timescale provides a brand-new method for estimating the frequency deviation and frequency drift of hydrogen clocks,and offers a safety backup for time keeping of time laboratory in the future.In this dissertation,the related research on pulsar timescale is carried out in order to furnish theoretical support and technical preparation for the joint time-keeping of pulsar time and atomic time in the future.The main work and innovations covered in this dissertation are as follows:1.Based on the previous research results in the field of X-ray pulsar timing,the data processing procedure of pulsars in X-ray band is further improved.The minimum number of photons for an effective observation,the reasonable value of the sub-phase interval number in the construction of pulse profile and the effective denoising method of pulse profile are analyzed and determined.The Crab pulsar observation data of XPNAV-1 satellite are processed,and the accuracy of the timing results obtained is higher than that of the predecessors.In order to deeply understand the radiation characteristics of pulsars,the simulation method of X-ray pulsar signals is also described.2.The construction method of Ensemble Pulsar Timescale(EPT)based on wavelet analysis theory is studied,and the construction software is designed based on the optimized algorithm.The inherent timing noise of pulsars contained in EPT is further weakened,and the obtained pulsar timescale is closer to TT(BIPM).The test result of fluctuations in atomic timescales using pulsar time are presented in combination with the real clock difference data,and the influence of the measurement accuracy of pulse time of arrival(TOA)on the detection of fluctuations in atomic timescales is analyzed.3.The research of correcting the frequency of on-board clock by pulsar time is carried out.According to the probability distribution theory,the influence of frequency deviation of reference clock on the periodicity of the recorded photon signals is analyzed.Based on the pulsar timing model,a method of using X-ray pulsar observation to correct the frequency deviation of space-borne atomic clock is designed and the steering software platform is implemented.The validity of the algorithm is verified by the Crab pulsar observation data of XPNAV-1 satellite.In addition,the relationship between the estimation accuracy of space-borne clock’s frequency deviation by pulsars and the length of observation data is investigated.Based on the stability of Crab pulsar and its steering results,the feasibility of using X-ray pulsars to maintain the time reference of space users is analyzed.4.The frequency deviation estimation method of ground hydrogen maser using pulsar timescale is investigated.According to the robust estimation theory,a strategy for estimating the frequency deviation and frequency drift of the hydrogen maser using pulsar timescale is designed.The estimation results are analyzed by using the observed data of the International Pulsar Timing Array(IPTA)and the data of a hydrogen clock in National Time Service Center(NTSC).And the effectiveness of the designed method is verified.