Research On Configuration Design And Coverage Performance Analysis Of Leo Mega-constellation

With the rapid development of global information network and commercial spaceflight,using numerous low-cost satellites to form mega-constellation to provide the Internet and other services has become an important future research direction.Appropriate satellite distribution is the prerequisite for the function realization of the constellation.In order to improve the efficiency and reduce the construction cost,it is necessary to determine the satellites distribution through configuration design and coverage analysis in advance.However,as the quantity of satellites increases,the computation burden of traditional design and analysis methods will significantly increase,thus many methods will no longer be applicable.Oriented to the current demand for the construction of low earth orbit(LEO)satellite systems,taking coverage analysis and configuration design of mega constellations as the background,this dissertation carries out research on the following issues: quick solution of the coverage performance of regular homogeneous constellations,design of Walker constellation configurations for continuous coverage requirements,and low-orbit constellation configuration evolution and coverage analysis in complex perturbation environments,etc.,which are specified as follows.Since the calculation volume of the traditional constellation coverage analysis method increases significantly with the number of satellites,a fast coverage analysis method of regular homogeneous constellations is proposed based on the satellite coverage area mapping and repeating unit theory of coverage performance.Firstly,according to the configuration symmetry of the regular constellation,the minimum period and area on the2 D map in which the coverage performances are repeated are determined.Then,the satellites that may affect the coverage performance in the repeating unit are screened based on the phase mapping of satellites and their coverage areas.By calculating the overlap of the mapped access area within a repeating unit of these satellites,the periodic coverage characteristics for a specific latitude can be obtained.Finally,coverage performance indexes are solved by calculating the areal multiplicity of the mapped target access area at different latitudes.Simulation results show that when solving the coverage performance of regular homogeneous constellations,computation amount and time of the proposed method are significantly reduced compared with the traditional methods,while the accuracy is not affected.As one of the most common configurations of LEO constellations,there are few general design methods of Walker constellation configuration that can satisfy different coverage requirements.To this end,a generalized Walker constellation configuration design method is proposed based on the street of coverage(SOC)theory and the geometric relationship of the mapping of coverage areas.Firstly,the configuration parameters of the SOC of a Walker constellation are proposed to improve the traditional configuration parameters.Then,the calculation method of geometric characteristics of the mapping of SOC is given.The configuration that satisfies the coverage requirements is obtained by determining the splicing of adjacent streets of coverage with different width positions.Finally,according to the configuration characteristics of constellations with different coverage folds,the configuration design steps of Walker constellations with even and odd continuous coverage,and the optimization method of the orbit inclination of the constellation are proposed respectively.Compared with the traditional design methods based on configuration enumeration,the proposed method can not only solve the constellation orbit and configuration parameters semi-analytically according to the satellite coverage area,the required coverage target area,and coverage folds but also obtain a constellation with fewer satellites under the same coverage constraint.Due to the orbit injection error and space environment,the satellite distribution will deviate from the nominal value,which will have a long-term impact on the constellation configuration and coverage performance.To analyze the evolution of the constellation configuration,a continuum probability distribution model is established.The initial distribution of the orbit parameters is first calculated based on the velocity deviation of the entry position.Then the evolution equations of orbit parameters are established under the two-body,J2 perturbation and atmospheric drag perturbation models.The differential equations are transformed into the first-order Cauchy problem using the characteristic line method for calculation,and then the analytical solution to the spatial probability distribution of the satellite is realized.Referring to the long-term evolution results of the constellation configuration and the evolution characteristics of different stages,the probabilistic description of the coverage performance evolution is given,and then the simplification and dimensionality reduction of this coverage probability model are realized based on the Poisson process theory.Finally,the Monte Carlo method is used to verify the validity of the long-term evolution model of constellation configuration and coverage performance.The model not only describes the constellation evolution law under the complex perturbation environment but also gives quantitative estimation and guiding suggestions on the constellation configuration and the number of satellites based on the desired coverage probability.