低轨通信卫星多普勒定位性能分析

Doppler Positioning Performance Analysis of LEO Communication Satellites

为了研究低轨通信卫星多普勒定位性能,首先分析了低轨卫星的对地覆盖特性、信号传输特性以及多普勒频移特性,推导了多普勒定位原理和方法,提出了适用于多普勒定位的精度因子.基于已在轨的铱星和全球星系统,解算了全球范围可见卫星数和定位精度因子,并对相应测站进行了定位仿真实验和误差分析.结果表明:对于铱星和全球星系统,随着纬度降低,卫星可见数减小,多普勒几何精度因子变大;多普勒定位结果精度同时受到频率测量精度、卫星位置误差以及卫星速度误差影响,当卫星位置误差小于10 m、卫星速度误差小于0.1 km·s^(−1)时,对定位结果影响不大,此时频率测量精度成为影响定位精度的决定性因素,且当频率测量精度为0.01 Hz时,定位精度可达1.18 m.

In order to study the Doppler positioning performance of low-earth orbit communication satellite,this paper analyses the ground coverage characteristics,signal transmission characteristics and Doppler frequency shift characteristics of low-earth orbit satellite,deduces the Doppler positioning principle and method and proposes the geometric dilution of precision which is suitable for Doppler positioning,firstly.Then,based on the Iridium satellite and GlobalStar satellite system,the number of visible satellites and geometric dilution of precision are calculated,and the positioning simulation experiment and error analysis of the corresponding stations are carried out.The results show that as for Iridium and GlobalStar systems,the visible number of satellites decreases and the Doppler geometric dilution of precision increases with the decrease of latitude;the accuracy of Doppler positioning results is affected by the frequency measurement accuracy,satellite position error and satellite speed error at the same time.When the satellite position error is less than 10 m and the satellite speed error is less than 0.1 m·s^(−1),it has little impact on the positioning results.At this time,the frequency measurement accuracy becomes the decisive factor affecting the positioning accuracy,and when the frequency measurement accuracy is 0.01 Hz,the positioning accuracy can reach 1.18 m.