Research On Theory And Methods Of Pulsar Timing Data

Pulsar is a natural celestial body with ultra-high density,super magnetic field,super gravitational field and super radiation.It is a natural laboratory under extreme physical conditions.In addition to the research of pulsar physical characteristics and gravitational wave detection,pulsar can provide high-precision autonomous navigation service and high stable time and frequency resources due to its unique periodic pulse radiation.On the one hand,pulsar navigation technology can provide autonomous navigation for deep probes,on the other hand,it can effectively reduce the demand of ground station measurement and control.Pulsar timescale can provide an independent time frequency based on distant natural objects,providing time services lasting millions or even billions of years.It can be seen that pulsar is a good combination of scientific research and technological research.In recent years,China attaches great importance to the development of pulsar related technologies.Ground radio stations and space X-ray satellites hold high-frequency observations of pulsars.It is is a basic work that how to deal with these observation data with high precision and how to build the spac×10-time benchmark of pulsar in China.This paper focuses on the establishment of pulsar database,the relativistic modeling of pulsar signal and the processing of pulsar measured data.The main innovative work and conclusions are summarized as follows:(1)Aiming at the problem of incomplete and inconsistent navigation ephemeris parameters,a qualitative criteria of navigation pulsars is proposed,and their parameters of a complete ephemeris are gained;the navigation observation accuracy of each pulsar is evaluated.Based on foreign pulsar databases and related documents of pulsar navigation,the timing models,pulse profile and energy spectrums of 18 pulsars are collected and processed;The observation accuracy of each pulsar by focusing or collimating X-ray detectors is analyzed;The influence mechanisms of pulsar observation error and position error on navigation accuracy are studied;Through error analysis,we can know that the navigation accuracy 6.538 km can be realized by observing three pulsar(PSR J1939 + 2134,J1824-2452 and J0437-4715)in near-earth space.The whole process from X-ray photon simulation to pulse ephemeris parameter fitting is established,the feasibility of obtaining ephemeris parameter based on space X-ray observation is studied,and the relationships between ephemeris parameter,observation time and observation interval are analyzed;The accuracy of ephemeris measurement by 120 meter diameter radio telescope in one year is equivalent to the technical level of 65 meter telescope in 10 years and 80 meter telescope in 5 years.(2)Aiming at the application prospect of pulsar navigation in deep space,a complete pulsar navigation model with universality in solar system is established.Based on the influence magnitude of time delay effect,a simplified navigation model with accuracy better than 1 ns is given,which has achieved good results in the actual data processing.In this paper,the transformation formulas of geometrical delay,gravitational delay under the second-order post Newton effect and the time from the original time to the center of mass of spacecraft are derived,and a complete signal propagation equation considering geometrical and relativistic effects is established.Using the concept of "instantaneous center of mass",an observation model for pulsar navigation is established,and the existing navigation models are compared;The influence of various geometric and relativistic effects on the orbits of the Sun,Earth and Jupiter in the solar system are analyzed;The influences of different planetary ephemeris on Romer time delay and the difference of different Shapiro time delay formulas are discussed;Based on the influence magnitude of various time delays,the observation model is simplified and applied to the data processing of pulsar,and the accurate pulse period and pulse contour are obtained.The difference between the results of the navigation observation model and those of the heasoft and hxmtsoft is compared.(3)According to the characteristics of the measured data of China's satellite navigation pulsars,several innovations are put forward in the signal processing method.The thre×10-year observation data of xpnav-1 pulsar crab and the two-year observation data of HXMT satellite crab and b1509 are processed,which improves the efficiency and accuracy of data processing.After processing,the pulse profile of pulsar in different energy segments is obtained,and the evolution rule of crab pulse profile characteristics with time is analyzed.It is confirmed that the first domestic focused x-ray detector can accurately measure pulsar.A method of evaluating its performance stability by using detector intrinsic radiation spectrum is studied,and it is found that xpnav-1 satellite tends to be stable since May 2018.This paper studies a method to analyze the performance and stability of the XPNAV-1 satellite by using the intrinsic energy spectrum of the detector,finds that there is strong interference in the observation data of the XPNAV-1 satellite in the Antarctic(latitude is greater than 70 degrees south latitude),proposes a method to check the total count rate of the observation by using the fitting value of the cas×10-based photon model,and suspects that the XPNAV-1 satellite may have high-energy particles to produce multiple readouts on the detector.This paper studies a method to get the time delay of the detector by timing analysis,and obtains the time delay of LE relative to HE detector.A pulse period search algorithm based on similarity is proposed,which is conducive to the detection of known pulsar signals in navigation.(4)It is the first time in China to carry out the joint ground observation processing of millisecond pulsars at multiple stations and the joint ground observation processing of crab pulsars.The systematic difference of each observation equipment is obtained,which makes a useful exploration for the establishment of pulsar timing array in China.The observation data of four Pulsars(J0835-4510,J0437-4715,J1744-1134,J1939 + 2134)at three stations in China are processed,the parameters of timing model are updated,and the systematic difference of the same pulsar observed at each station is obtained;Secondly,the ground radio joint processing,space joint processing and satellite earth joint processing of Crab pulsar are completed,and the system error between different observation equipments at different frequencies are obtained.It is found that there is obvious difference between radio and high-energy radiation,and the difference becomes larger after periodic jump.For the maximum periodic jump event of Crab pulsar in 2017,the differences at different frequencies are estimated by domestic equipment.(5)The testing methods of X-ray detector on ground or in orbit are studied,which effectively guarantees the selection of xpnav-1 satellite pulsar navigation detector and in orbit performance evaluation.A comprehensive test method of X-ray detector performance is studied,and five domestic X-ray detectors are tested.Aiming at xpnav-1 satellite without calibration radiation source,a method of using pulsar radiation spectrum to calibrate the effective area of detector is proposed.