The Principles And Methods Of Spacecraft Attitude Measurement Based On X-ray Pulsars

The autonomous navigation based on X-ray Pulsar is one of the perfect ways for spacecraft navigation in deep space exploration, such as the Lunar Exploration in China. The autonomous navigation can be applied to the navigation of spacecrafts around the Earth. It can reduce the dependence of the ground stations, and enhance spacecraft autonomy, security and reliability. So the autonomous navigation based on X-ray Pulsar becomes a focus for the power country in spaceflight. The X-ray Pulsar attitude measurement is an important part of the autonomous navigation based on X-ray Pulsar.The principles and methods of the spacecraft attitude measurement based on X-ray Pulsar are studied in the thesis. It focuses on the contents and their corresponding conclusion as follows:1,Improved absolute positioning method based on X-ray Pulsar and Compass satellite is discussed.In view of the coupling of attitude measurement and positioning based on X-ray Pulsar, the absolute positioning improved method based on X-ray Pulsar and Compass satellite is proposed , according to the general principle of absolute positioning based on X-ray Pulsar . The key of this method is solution of the integer cycle phase ambiguity of Pulsar arrival time. Combining batch with search space array method for solving the Pulsar time phase ambiguity, the improved search space array method is proposed. The simulation shows that the precision of positioning from improved search space array method is more accuracy than it from the batch.2,The abstract structure of detectors, technology framework and Formal Theory description for attitude measurement based on X-ray Pulsar is proposed.The current X-ray Pulsar detectors as known are analyzed, the imager abstract structure is proposed for attitude measurement of three-axis stabilized spacecrafts, and the scanner abstract structure is proposed for attitude measurement of single-axis stabilized spacecrafts. According to the characteristic of two equipments, technology framework of attitude measurement based on X-ray Pulsar is proposed as a whole. The ideas of attitude measurement based on X-ray Pulsar are given for spacecrafts of three-axis stabilized and single-axis stabilized. The process of Attitude measurement based on X-ray Pulsar is given with the technology frameworks. In order to promote theory scalable of attitude measurement based on X-ray Pulsar, Attitude measurement based on X-ray Pulsar is described Formal by Tuple. The formalization directed graph of attitude measurement based on X-ray Pulsar is deduced.3,Attitude measurement model based on X-ray Pulsar is deduced for single-axis stabilized spacecrafts. The detectable efficiency of abstract structure is depicted,X-ray Pulsar collimator model of mathematics is deduced. The single collimator attitude measurement models of first order and second order based on X-ray Pulsar are established, and difference collimator attitude measurement models of first order and second order based on X-ray Pulsar are established too. The target is providing available mathematic models and establishing theory groundwork.4,The genetic algorithm is applied to attitude measurement model based on X-ray Pulsar.Attitude measurement model is optimized by genetic algorithms in the thesis. According to simulation, the convergence value of target is achieved. The attitude information of spacecraft is obtained from the fitting parameters at the same time. It can be seen from simulation that the objective function can obtain good convergence results, when the genetic algorithm is applied to attitude measurement model based on X-ray Pulsar. Comparing with attitude measurement models of single-collimator and the differential-collimator, it can be found that the convergence speed of difference collimator attitude measurement models is faster than the single collimator attitude measurement models,moreover the convergence efficiency is more obvious.5,The Kalman filter model of spacecraft attitude measurement based on X-ray Pulsars is established.The Kalman filter model of spacecraft attitude measurement based on X-ray Pulsars is established through continuous observation values and state equations. According to the simulation of the Kalman filter model, it can be found that the theory of attitude measurement based on X-ray Pulsars is feasible. The spacecraft attitude converge errors can reach the order of 0.001 radians, whether three-axis stabilized spacecraft or single-axis stabilized spacecraft through filtering. And it can be seen from the convergence curve of the simulation that the convergence error decreases as the decrease of the initial error. The differential-collimator attitude measurement precision is more accuracy than the single-collimator attitude measurement precision.It can be seen from the conclusions in the thesis, the precision of positioning from improved search space array method is more accuracy than the precision of positioning from the batch. The idea and method of attitude measurement based on X-ray Pulsars are given by technology framework and Formal Theory description. When the Genetic algorithm is applied to attitude measurement models of single-collimator based on X-ray Pulsars, the convergence efficiency of target value is obvious. It can be indicated from simulation of attitude measurement in the Kalman filter model, the differential-collimator attitude measurement precision is more accuracy than the single-collimator attitude measurement precision by about 36%.Above all, as long as we plunge into more energy for attitude measurement based on X-ray Pulsar, the new available approach of attitude determination can be obtained for deep space exploration spacecraft in China.