通过GPS测量数据研究电离层电子总含量的逐日变化

提出了一种直接通过双频GPS伪距测量数据导出接收站附近垂直TEC的方法,这种方法不需要事先知道卫星和接收机电路时延的精确值,前者可在换算过程中自洽地加以修正,而接收机时钟误差则利用IRI模式的夜晚平均值作为参考来订正,这一订正存在一定的绝对误差,但不会影响逐日相对变化,却使数据处理过程大为简化.得到的垂直TEC为天顶周围60锥角内的平均值,能够相当好地反映电离层电子总含量的周日变化.一个计算实例显示了连续三天北京地区TEC的日变化情况,证实了这一方法的实用性.文中还提出一个新概念或问题,即GPS卫星仰角很小时,通常认为多径效应造成大的误差,本文的一些实例似乎表明,这种多径效应的概念应当包括电离层不规则结构的贡献.

AN APPROACH TO STUDY THE DAY-TO-DAY VARIATIONS OF IONOSPHERIC TECDIRECTLY BY GPS TIME-DELAY SIGNAL

In this paper, an approach was presented to deduce the diurnal variation ofionospheric TEC through only the measured data of time-delay (pseudo-range) ofGPS signals without using any phase information. Thus the procedure to studyTEC day-tcaday vaxiations is greatly simpllfied. In this method, satellite clock biascan be removed self consistently in the calculations while the receiver clock erroris corrected by using the average night values from IRI model- In this way someabsolute error due to receiver clock may still exist, but this does not infiuence thestudy of day-to-day vaxiations. The calculated vertical TEC is the average of verticalprojections of all the line-of sight TEC from differellt satellites in a conical angleof 60 degrees around the local vertical direction. An example of three consecutivedays' TEC variation was given, which shows the validity of the method suggestedin this paper. Finally it is pointed out that in the case of large zenith angle ofsatellite, ionospheric irregularities may contribute certain amoullt to the multi-patheffect.