面向区域导航增强的低轨卫星星座设计

部署低轨导航卫星是对现有卫星导航系统的有效补充，是实现导航增强的重要途径。研究了低轨卫星的星座设计问题，面向区域导航增强的应用需求，采用基于椭圆轨道的星座设计方案，利用卫星在椭圆轨道远地点运动速度慢、覆盖区域大、相对地面滞留时间长等特点，提升其对局部区域的覆盖能力。此外，在Flower星座框架下优化每颗卫星的轨道参数，确保其星下点轨迹重复经过重点区域的中心，延长卫星相对于给定区域的过顶时间。有效改善了过顶时间、覆盖重数、空间几何分布等影响导航性能的关键指标。在以北斗3号系统为导航增强对象的仿真对比中发现，在低轨卫星数量相同的条件下，该文的卫星星座设计方案具有更好的导航增强性能。

LEO Satellite Constellation Design for Regional Navigation Augmentation

The deployment of low earth orbit (LEO) navigation satellites is an important supplement to the existing satellite navigation systems and also an effective approach to navigation augmentation. The design of LEO satellite constellation is studied in this paper, in order to optimize its performance in regional navigation augmentation. Different from the near-circular-orbit-based scheme adopted by most LEO constellations for global navigation augmentation, an elliptical-orbit-based constellation scheme is employed in our design. Owing to the slow-motion speed, the large coverage area, and the long residence time of satellites in the apogee of elliptical orbit, the elliptical-orbit-based scheme is specifically suitable for regional navigation augmentation. In addition, under the framework of Flower constellation, the orbit parameter of each satellite is optimized to ensure that the trajectory of its sub-satellite point repeatedly passes through the center of the region, thus extending the zenith crossing time of the satellite. By the aforementioned constellation design, the key navigation performance metrics, such as zenith crossing time, coverage multiplicity, and geometric dilution of precision, are effectively improved. In the simulations with BeiDou-3 system (BDS-3) being the navigation system to be augmented, it is validated that with the same number of LEO satellites, the proposed design achieves better navigation augmentation performance.