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

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.In this paper, an approach was presented to deducethe diurnal variation of ionospheric TEC through only the measured dataof time-delay (pseudo-range) of GPS signals without using any phaseinformation. Thus the procedure to study TEC day-to-day variations isgreatly simplified. In this method, satellite clock bias can be removedself-consistently in the calculations while the receiver clock error iscorrected by using the average night values from IRI model. In this way,some absolute error due to receiver clock may still exist, but this doesnot influence the study of day-to-day variations. The calculatedvertical TEC is the average of vertical projections of all theline-of-sight TEC from different satellites in a conical angle of 60degrees around the local vertical direction. An example of threeconsecutive days' TEC variation was given, which shows the validity ofthe method suggested in this paper. Finally, it is pointed out that inthe case of large zenith angle of satellite, ionospheric irregularitiesmay contribute certain amount to the multi-path effect.国家自然科学基金中文核心期刊要目总览(PKU)中国科学引文数据库(CSCD)0297-1022