联合GNSS/LEO卫星观测数据的区域电离层建模与精度评估

Regional Ionospheric Modeling and Accuracy Assessment Using GNSS/LEO Satellites Observations

高精度的电离层模型对于提高导航卫星系统的定位精度具有重要意义。低轨卫星的快速发展为建立高精度的电离层模型提供了新的契机。基于仿真数据模拟获得2017年1月1日—30日LEO(low earth orbit)和GNSS(global navigation satellite system)卫星观测数据,星座类型包括60、96、192和288颗卫星,以非洲区域为例,利用该数据研究GNSS和LEO卫星穿刺点的覆盖情况和联合建模精度。结果表明:加入LEO卫星后,穿刺点分布改善明显,能够大幅度提高穿刺点密度;单颗低轨卫星穿刺点的范围比GNSS卫星大,LEO卫星的高度角和方位角变化明显;随着低轨卫星数量的增加,融合建模的精度也随之提高;在12:00时东经30°不同纬度范围内,单GNSS建模和GNSS+288 LEO建模差值最大为-1.6 TECU(total electron content unit);随着建模时长的增加,融合建模结果和单GNSS结果差值逐渐变小。

High-precision ionospheric model is of great significance for improving the positioning accuracy of navigation satellite system. With the rapid development of low earth orbit satellites, the establishment of a high-precision ionospheric model has provided new opportunities. Based on the simulation data, this paper obtains LEO(low earth orbit) and GNSS(global navigation satellite system) satellites observation data of January 1 to 30, 2017 by means of simulation. The constellation types include 60, 96, 192 and 288 satellites respectively. Based on these data and taking African region as an example, the coverage of GNSS and LEO satellites’ ionospheric pierce points and the joint modeling accuracy are studied. The results show that, after LEO satellites are added, the distribution of ionospheric pierce points is significantly improved,which leads to a noticeable rise of their density. The range of ionospheric pierce points of single low-orbit satellite is larger than that of GNSS satellite, and the altitude angle and azimuth angle of LEO satellite change remarkably. With the increase of the number of low-orbit satellites, the accuracy of joint modeling also rises up. Within different latitudes of 30° E at UTC 12: 00, the difference between GNSS-only and GNSS+288 LEO ionospheric modeling results is the largest, reaching-1.6 TECU. With the increase of modeling time, the difference between the joint modeling results and GNSS-only results gradually decreases.