Research On Acquisition And Recongnition Of Pulsar Signals And Its Application In Navigation For Formation Flying Spacecrafts

The competition of space resource in new epoch has undertaken among the countries worldwide and pulsar navigation as the effective substitute and challenge to the traditional counterpart becomes the focus of the research and exploration. Pulsar signal as the source of navigation information is beneficial in the navigation range and on the other hand independent from the usage license limitation. Meanwhile it supplies synchronization, vehicle attitude and position information for spacecraft navigation. Analysis towards pulsar navigation perspectives and key technology breakthrough leads to a predominant position in competition. This thesis combined with the eleventh five years project background and national high technology research development project explores the pulsar processing technology for its application in the navigation of formation flying spacecraft, mainly focus on pulsar signal denoising, identification, and attitude measurement as well as relative ranging based on pulsar navigation, the details as follows.First of all, on the basis of current research statement, this thesis summarizes the research method and development of pulsars navigation for distributed satellite system, and then by analyzing the research method, this paper indicates the research direction of pulsars navigation for distributed satellite system in future researches.Secondly the thesis discusses the pulsar classification according to the signal characeristic and the analysis covers the pulsar emission signals and spectrum characteristic which is the theoretical foundation of the pulsar identification and measurements.Then considering the extraction of pulsar signals, the thesis presents a method of pulsar signal denoising based on empirical mode docomposition. Meawhile entropy is selected as the threshold to decide the operation of postfitting of the signal. Furthermore, a tower-like multiple EMD is derived later.Considering the pulsar signal's characteristic it is proposed that the identification of pulsars is implemented via instantaneous amplitude and frequency extracted via Hilbert-huang Transformation; Then BP neural network algorithm are respectively applied to identify the different pulsarsMoreover, this paper describes the design, tests and preliminary results of a multiple-plane sensor detecting the X-ray pulsars vectors to acquire the spacecraft attitude. Comparing to the star sensors or other traditional attitude measuring, the multiple-plane sensor has made an adversary and new effort by inventing a multiple-plane structure, with the orthogonal vectors pointing towards the different directions. By measuring the power received by each plane and considering the geometry relationship of the planes, the sensor computes the pulsars vector from a certain pulsar. Therefore, the attitude of the spacecraft can be acquired if vectors from several different pulsars is recognized and specified. Accordingly the simulation is established and the result proves its charming feasibility in future spacecraft missions.Finally, a novel method of intersatellite ranging calibration is presented based on the observation of pulsars. According to the method intersatellite range projected in the direction of pulsars can be directly determined by correlating the pulsar signals detected on different spacecrafts in a distributed satellite system. Meanwhile accuracy of the method is derived based on the analysis of the celestial sources and their spectras. The method is evaluated using the realistic simulation of the pulsars and orbit information of distributes spacecraft. The result verifies the feasibility of in the application of the future distributed satellite system. Then according to the method intersatellite range projected in the direction of pulsars can be directly determined by using the rotational invariance of the pulsar signals detected on different spacecrafts in a distributed satellite system. Meanwhile accuracy of the method is derived based on the analysis of the celestial sources and their spectrums. The method is evaluated using the realistic simulation of the pulsars and orbit information of distributed spacecraft. The result verifies the feasibility of in the application of the future distributed satellite system.