ephemeris time

1. 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。
2. 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。
3. The broadcast ephemeris, which is the basic of satellite navigation, must be precise and real time.
   导航卫星广播星历是卫星导航定位的基础，要求有较高的精度和实时性。
4. Through comparing the accuracy and latency of broadcast ephemeris and three kinds of precise ephemeris provided by IGS ( the International GPS Service), it was found that only IGS ultra rapid products ( IGU) can meet the need for time of tropospheric monitoring.
   通过比较广播星历和IGS（国际GPS服务机构）目前提供的3种精密星历的精度和时延性，得出只有超快星历（IGU）才能满足对流层监测的时间要求。
5. The theories of computing geometric delay are adopted to get the difference between broadcasting ephemeris delay and precise one, which is added to the results of GPS CV time comparison.
   采用几何时延计算的基本原理计算出广播星历时延与精密星历时延之差，然后将其补偿到GPSCV比对结果中，从而提高GPS共视比对结果的精度。
6. The results show that this method improvs the GPS satellite orbital positions coordinate calculation accuracy, and the errors calculated by making use of the broadcast ephemeris are caused by the method of extrapolation of time.
   结果表明，该方法确实提高了GPS卫星轨道位置坐标计算的精度。利用广播星历计算GPS卫星位置的误差主要是由于时间外推方法造成的。
7. The results show that the orbit precision of broadcasting ephemeris is about 3m in observation period of time. 3 、 The basic theory and method of making use of GPS pseudo-range observation data and SLR observation data to evaluate the precision of broadcasting ephemeris is mainly studied.
   结果表明，在观测时段内，广播星历轨道精度总体上达到3m；。3、重点研究了伪距观测量和激光观测量评估广播星历精度的基本原理与方法。

noun

1. (astronomy) a measure of time defined by Earth's orbital motion

   Synonym:    terrestrial timeTTterrestrial dynamical timeTDT