低轨导航增强卫星星座设计

针对目前全球低轨卫星快速发展的现状，对低轨导航增强卫星星座设计方法进行了详细的研究。首先推导了轨道高度与可视球冠的关系，结合太空垃圾分布，从覆盖范围、经济性及碰撞风险几方面联合确定了轨道高度。然后推导了用户仰角与轨道倾角的关系，分析了实现南北极点覆盖的轨道倾角。接着结合铱星星座，推导出单一星座构型无法实现全球范围内均匀的可见星和精度衰减因子（Dilution of Precision，DOP）值分布。最后提出了一种组合低轨卫星星座设计方法。结果表明，该方法设计的组合星座在实现全球覆盖的同时，能够实现可见星数量与DOP值在全球范围内的均匀分布。

Design of LEO satellites augmented constellation for navigation

A constellation design method of LEO (Low Earth Orbit) satellites augmented constellation for navigation is presented since global LEO satellites becoming a hot spot. Firstly, the relationship between the orbit altitude and the visible spherical crown is deduced, thus the constellation altitude can be computed with the space debris distribution, economy and collision risk. Then, the relationship between the elevation and the orbit inclination is derived, and meanwhile the constellation inclination is determined to get north and south poles coverage. Next, compared with Iridium, it is demonstrated that a single constellation can′t achieve a uniform visible satellites distribution and DOP（Dilution of Precision）on global scale. Finally, an LEO satellites constellation design method is proposed, which can achieve global coverage while make the DOP (Dilution of Precision) and the visible satellites distribute evenly around the world. The results show that the mixed constellation designed by the method can achieve a global coverage and even distribution of visible satellite numbers and DOP.