GPS时间系统的转换程序，比较简单，各个时间系统和GPS时间的相互转换-GPS time system conversion process is relatively simple, all-time systems and GPS time conversion

通过坐标转换的方法估算月球在某一时刻在J2000坐标系下的位置和速度。（理解航天中坐标转化、时间系统的学习案例）-Through the coordinates of the conversion method to estimate the moon at a time in the J2000 coordinate system under the location and speed. (Understanding of aerospace coordinate transformatio