电离层效应的测时误差及其修正

电磁波经过电离层传播时会受到电离层折射的影响而产生延迟, 星载接收机探测到的时间是信号延迟之后的到达时间. 某次实验数据显示, 一些波段的瞬态电测辐射信号的群时延之差可达10⁵ns数量级, 这在对信号源进行时差定位时是不能直接运用的. 为有效消除电离层延迟的影响, 将双频修正法应用于某项工程中, 利用接收到的实验数据求解出电离层的TEC(电离层总电子含量), 并在此基础上对信号到达星载接收机的时间进行修正. 最后,对修正结果进行了验证, 给出了误差来源.

Measurement Error and Correction of the Ionospheric Effect

Electromagnetic waves,when propagate through the ionosphere,would get delays due to the ionosphere refraction.According to certain experimental data,the difference of the group delay is up to 10⁵ ns.It is close to the time of the earth surface echoes when the signal generator is about 15 kilometers above ground in the air,and they are difficult to be distinguished(30 km/(3×10⁸m·s^-1) = 10⁵ ns).So the time when the transient electromagnetic waves reach satellite receiver cannot be utilized directly in doing Time Difference of Arrival（TDOA）.In this paper,the ionospheric Total Electron Content（TEC） is derived by Dual-Frequency Method,and on this basis,the time received by satellite receiver is modified.The result shows that it is inaccurate with the error being about 100 ns.The potential origins of the error are provided.