Research On X-ray Pulsar-based Navigation Methods And Signal Processing Algorithms

With the development of space technology and universal exploration,the autonomous navigation technique is challenged by the increasing space missions.Spacecraft using autonomous navigation can effectively reduce the on-orbit operation costs and improve its survivability.The emerging X-ray pulsar-based navigation is a significant support for deep space exploration,autonomous operation of the on-orbit spacecraft and the completed near-ground space navigation system.To promote the engineering application and enhance the performance of the X-ray pulsar-based navigation,this paper studies the signal processing algorithms and positioning methods of the X-ray pulsar-based navigation.The mathematical and ground-simulated X-ray pulsar signals,as well as the RXTE on-orbit measured data,are used to analyze the content of the proposed work.The X-ray pulsar signals are studied in the time domain and frequency domain separately.By the time-domain analytical approach,a high-efficiency period estimation method for X-ray pulsar signal is first proposed using the pulsar time-of-arrival(TOA)arrays,which aims at the technique of pulsar profile recovery.The computational complexity and accuracy are analyzed theoretically.In terms of the computational cost and efficiency,the said period estimation is superior to the classical Chi-square period estimation method.Advanced profile construction algorithms are presented based on kernel estimation technology.The contour quality and the precision of the estimated TOA using de-noised contour are utilized to evaluate the performance of the said pulsar profile recovery methods.According to the simulation results,no differences were found in the precision of the estimated TOA after reducing the noise of the pulsar profiles surprisingly.It can thus be suggested that it is not necessary to de-noise the epoch folding profile for estimating the TOA for X-ray pulsar-based navigation systems.In the frequency domain analysis of X-ray pulsar signals,the paper first delivers the maximum likelihood estimation of the phase of the fundamental frequency and generalizes it to the harmonic phase estimation.Consequently,the optimized weighted-harmonic phase(WHP)is defined,and the Cramér–Rao bound of the WHP is derived.The estimating performance of the WHP is then studied and analyzed by comparing the phase of the fundamental frequency and averaged-harmonic phase in theory.Following the phase invariance principle of the light wave,the navigation measurement model based on the epoch-differential WHP is established in the Minkowski space and the Riemann space respectively.By analyzing the time delay of the general relativity effect numerically,a simplified epoch-differential measurement model using the weighted-harmonic phase is derived for the application of X-ray pulsar-based navigation.Finally,the statistical property of the defined weighted-harmonic phase and the correctness of the corresponding epoch-differential navigation measurement model are discussed by a series of simulation experiments.In terms of the positioning and navigation methods of X-ray pulsar signals,the paper first proposes the initial orbit determination(IOD)method from relative position increment measurement.The epoch-differential information can effectively eliminate the common error of measurement for precise navigation,while the conventional research believes that the differential position measurement information cannot independently navigate spacecraft relative to the central celestial body.Therefore,the proposed IOD method remedies the defect and is applicable to any sensor which provides the relative position increment measurement.The observable analysis method of the piece-wise constant system is applied to study and prove the complete observability of the epoch-differential measurements based pulsar navigation system.Aiming at the correlated process and measurement noise inherent in the epoch-differential pulsar-based navigation scheme,a modified Kalman filter using augmentation state technique is proposed to solve the issue of the correlation and guarantee the efficiency of the presented navigation method.Additionally,notice that the pulsar-based navigation system provides the relative positional distance information of the satellites for the formation flying satellites while navigating the spacecraft in the solar system.The paper designs and studies the formation flying satellite navigation,guidance and control system based on X-ray pulsar signals,and carries out comprehensive research and simulation verification from the perspectives of system framework,navigation filter,and formation satellite guidance and controller.