ephemeris time

The evolution of time measurement system has experienced the following stages in general : the ancient time measurement systems , universal time , ephemeris time , atomic time and universal time coordinated .

时间计量系统的演变大致经历了如下几个阶段：古代的时间计量系统、世界时、历书时、原子时、协调世界时。

The emphasis is given on analysis to relationship of error sources to location accuracy on platform ephemeris , echo time delays , target elevation , Doppler center frequency and time clock etc.

着重分析了平台星历、回波时延、目标高度、多普勒中心频率和时钟等误差源与定位精度的关系。