Research On Process Of Pulsar Timing Data And It’s Application

Pulsar has excellent rotation frequency stability, especially millisecond pulsar, its long term frequency stability is as good as atomic clock’s, so millisecond pulsar is suitable to establish a brand new time scale, that is pulsar time scale(PT). Pulsar time and atomic time are based on different physical mechanism, so pulsar time can be used to compare with atomic time. But there are many astrometric factors that will cause influence on pulsar timing observation, such as pulsar position error, pulsar proper motion error, earth orbit major semi-axis error, earth orbit eccentricity error,these will all cause bias in pulsar’s clock model parameter. Analyzing pulsar timing observation from astrometric aspect will work out the mechanism how earth ephemeris error cause influence on fitting of pulsar clock model parameters. A set of pulsars with accurate clock model parameters and astrometric parameters can make up pulsar time and space reference frame, it will provide time and space standard for space vehicle. Autonomous navigation using pulsar is another important application of pulsar time scale, and its principle can be testified with radio observation data, and accuracy of this method can be evaluated.Research work of this dissertation is mainly about influence of earth ephemeris error on pulsar timing observation, establishment of pulsar time scale and pulsar navigation.(1). Influence of influence of earth ephemeris error on pulsar timing observationPulsar timing observation is fundamental means of pulsar physics and its application, high precision earth ephemeris is necessary to get high quality timing observation data. Now the most common and most accurate earth ephemeris used in pulsar timing observation is DE series ephemeris from JPL under NASA, this series of ephemeris is derived from solar system planets ranging information and estimation of planets. Because of errors in planets ranging and mass estimation will deduce systematic error in DE ephemeris, especially error in earth ephemeris will pose influence on pulsar timing observation and navigation. In this dissertation we analyzed the systematic error in DE ephemeris in details, compared different versions of ephemeris to each other, results show that mass error in outer planets is the main reason that causes error in ephemeris. Meanwhile we analyzed pulsar timing residuals from astrometry aspect, calculated influence caused by all errors of ephemeris parameters on pulsar timing residuals, deduced linear fit formulation.(2). Establish ensemble pulsar time with NANOGRAV data setDuring evolution of pulsars, with the collapse of massive star its radius becomes less and less, as its core rotates faster and faster, finally when pulsar comes into being,its rotation period is at second level, among those there is a special kind of pulsars whose rotation period is at millisecond level, that is millisecond pulsar. Millisecond pulsar has extremely stable rotation frequency, the shift of its rotation frequency is at1E-20 level. Pulsar rotation is stable and measurable, long term timing data of millisecond pulsar can be used to generate pulsar based time scale. Unlike atomic time scale, pulsar time is a kind of time scale that referenced to macroscopical movement, so physical mechanism behind these two time scales are totally different,we could compare them with each other. High precision pulsar timing data is crucial to PT’s accuracy and stability, we decided to use NANOGRAV’s data set to generate pulsar time, which has the best data quality among three arrays that compose IPTA.According to characteristics of NANOGRAV data set, suitable algorithm and data process procedure is studied. At last we generated ensemble pulsar time scale using the latest released NANOGRAV’s 9 year data set, whose long term(>1 yr) frequency stability is 3.4E-15. And results showed that these algorithm and data process procedure can significantly reduce the influence caused by noise in timing residuals,and increased long term stability of ensemble pulsar time scale.(3). Pulsar navigation with single telescope and principal experimentAutonomous navigation using pulsar is another application of pulsar, usually when pulsar autonomous navigation technique is deployed at least four large area X-ray telescope must be loaded on spacecraft, it is very difficult to deploy it. Beyond that, I proposed a new spacecraft autonomous navigation method using single X-ray telescope together with inertial navigation system, with this method only one X-ray telescope need to be loaded on spacecraft, and observe a set of pulsars in certain sequence, together with information of relative position measurement at different epoch,spacecraft’s position at initial epoch is derived. To testify the feasibility and accuracy of this method, I made an experiment with observational data from PPTA data set, 16 pulsars’ data was used and telescope’s coordinates were calculated. The calculated coordinates was compared to real position of telescope, results show that pulsar navigation with single X-ray telescope is feasible. In this dissertation I studied spacecraft formation time synchronization method based on ensemble telescope observation, and detailed plan was given.