Research On Key Technologies Of Space-based Pulsar Time

The construction of space-based time-frequency scale is an important basis for improving the autonomous survivability of space-based systems.This dissertation mainly studies the key technologies of space-based pulsar time construction,including the efficient period and phase search methods and pulsar timing.The main research work and results are as follows:（1）A pulsar cumulative profile prediction model is constructed,and on this basis,a pulsar rotation period and phase search method without tentative epoch folding is proposed.In order to further improve the calculation speed,a pulsar period and phase estimation method in the vector space constructed by pulse profile template is proposed.When the template is unknown,a pulsar period estimation method based on Fourier series is proposed.This method is insensitive to noise and can obtain high-precision pulsar period and pulse profile with high signal-to-noise ratio.（2）The application of fast folding algorithm in X-ray pulsar observation data processing is studied.Two improved schemes suitable for weak signals are proposed,which expands the application scope of the fast folding algorithm.Aiming at the disadvantage that the original fast folding algorithm is not flexible in operation and storage,a variant of fast folding algorithm based on post order traversal of binary tree is proposed which can reduce redundant calculation.Aiming at the shortcomings in processing extremely weak pulse signals of X-ray millisecond pulsar,a fast folding algorithm independent of pulse intensity matrix is proposed,which has obvious advantages over epoch folding algorithm.（3）Pulsar timing based on the data of NICER mission is studied.Aiming at the preprocessing of space X-ray observation data,a photon screening method based on photon energy is proposed which has the advantages of simplicity and efficiency,and greatly improves the signal-to-noise ratio of space X-ray observation data.The timing results show that the annual stability of PSR B1821-24 and PSR B1937+21 are 6.60×10^-13 and 1.05×10^-13 respectively,which verifies the feasibility of constructing space-based time-frequency scale through X-ray millisecond pulsar observation.The research of this dissertation can provide theoretical and technical support for X-ray observation data processing and the construction of space-based time-frequency scale.