卫星星座的相对几何和区域覆盖重复周期

研究了在设计δ星座或者由几个δ星座的某些卫星构成的星座时经常需要考虑的三个问题：任意两颗卫星是否在同一条星下点轨迹上，同一条星下点轨迹上的卫星通过某一区域的相对顺序和星座对某特定区域或地点覆盖重复周期的计算。首先对δ星座中卫星之间的相对几何关系做了详细的分析，给出了第一个问题的判断准则，并进一步导出了位于同一条星下点轨迹上的卫星通过某一指定地区的相对顺序以及相应的时间间隔的计算方法。在解决前两个问题的基础上，针对由一个或几个δ星座(或子星座)构成的设计星座，给出了计算其区域覆盖重复周期的方法。

Relatively geometry and regional coverage repetitive period of satellite constellation

This paper focuses on the three problems about subsatellite point trace the sequence of satellites passing one region and regional coverage repetitive period in the process of designing satellite constellation.Firstly,the paper offers a rule to determine whether several satellites of a Walker constellation share the same subpoint trace.Secondly,we present a method to calculate the relative sequence of the satellites,which share the same subpoint track,passing across a particular region and the time intervals between two consecutive satellites.Finally,based on the work mentioned above,we develop a method to calculate the regional coverage repetitive period of a designed constellation--which may comprise one or several Walker constellations (or sub-constellation) by doing as the following.First,we make out the satellites that belong to every single subpoint traces according to the rule that is supposed to determine whether several satellites in a Walker constellation share the same subpoint trace.Then,for every subpoint trace,we analyze the relative sequence of all the subpoints of the satellites of this subpoint trace to determine the relative positions of the subpoints of those satellites in the designed constellation.Finally,the subpoints-repetitive periods of every subpoint trace are calculated,and,the least common factor of all the calculated periods is the regional coverage period of the designed constellation.