| LEO satellite can move faster relative to the ground and provide stronger landing signal than GNSS satellites,which can effectively improve the performance of medium and high orbit navigation constellation,therefore,it has become the development direction of the next generation of navigation constellation.However,most of the existing global navigation constellations and LEO constellations are single configuration,which has the inherent problem of uneven global distribution of navigation performance.Some scholars have proposed the hybrid configuration to solve this problem,but the relevant design method is not perfect,the efficiency of analysis and optimization also needs to be improved.In this paper,the design and optimization methods of LEO hybrid constellation for regional /global navigation services are studied.The research starts from the mature high orbit regional hybrid navigation constellation to the more complex large scale LEO hybrid navigation satellite constellation.Based on the hybrid configuration consists of GEO and IGSO,a symmetrical satellite constellation design and optimization universal model for rectangular area navigation service is proposed;Taking Walker Constellation as a sub-constellation,a fast analysis and optimization model of large LEO global navigation constellation with multiple inclination subconstellations is proposed;Aiming to specific area,taking Flower constellation as a subconstellation,a LEO hybrid asymmetry navigation constellation design and optimization model is proposed,which is composed of two asymmetric sub-constellations.Since the optimization objective is mainly to calculate the GDOP and the number of visible satellites base on the spatial and temporal distribution of the constellation,this method can provide some new ideas for the following LEO satellite constellation design which integrate the function of navigation,communication and remote sensing.The main research contents and conclusions are as follows:(1)For the rectangular navigation service area that contains key area and normal area,a hybrid constellation design and optimization universal model based on GEO and IGSO satellites and symmetrical configuration is proposed,which has the advantage of less optimization parameters.The asymmetric constellation configuration in a certain range is obtained by properly releasing the constraints of symmetrical configuration to achieve better navigation performance.The 6 / 7 / 8 satellites constellation is designed for the low latitude region(55 ° E?110 ° E,5 °S?50 ° N)based on two-step method,and the 3 GEO satellites and 4 IGSO satellites(double "8" ground track)is the best navigation constellation scheme.In addition,the method is also flexible applied to the design and optimization of extended constellation scheme of extended service area.(2)For large scale LEO hybrid global navigation constellation,a fast analysis and optimization model of multi constellation based on characteristic parameters and GAPM model is proposed.Only using the characteristic parameters(semi-major axis,orbital inclination and the total number of satellites)of each sub-constellation can greatly reduce the dimension of the optimized parameter set;The geometric and probability model(GAPM)is introduced and reasonably reduce the number of ground sampling points,which can quickly calculate the spatial and temporal statistics of GDOP.Taking 180 LEO satellites with the height of 1500 km as an example,a hybrid constellation composed of Walker sub-constellations with 1 to 5 orbital inclinations is constructed.The comparison shows that the hybrid constellation composed of four sub-constellations is the best scheme,and the number of satellites and inclination of each subconstellation are 32(25.31°),36(44.07°),43(62.03°)and 69(82.49°).In addition,this method is also used to the design of the LEO navigation augmentation constellation based on the 24 MEO satellites constellation of BDS-3.(3)Aiming at applying LEO constellation to navigation augmentation in specific area,through the studies of the restricted right ascension of ascending node,which determines the range of the orbit plane,a LEO hybrid asymmetry navigation constellation design and optimization model is proposed,which is composed of the main sub-constellation and supplementary subconstellation of Flower configuration.Taking the constellation contains 60 LEO satellites with semi-major axis of 7626.31 km as an example,a LEO navigation augmentation constellation of BDS-3 is designed for the region(10 ° N-40 ° N,100 ° E-140 ° E).The number of satellites and orbital inclination of the two optimized sub-constellations are 43(50°)and 17(39°),the total range of right ascension of ascending node is 327.38°.However,compared with the single symmetry configuration,the navigation performance of hybrid asymmetry configuration is only improved2%;If only considering the navigation GDOP index,compared with geosynchronous orbit,LEO satellite constellation(single configuration and hybrid configuration)has no advantage in multiple coverage of the region. |
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