Electron Density Reconstruction by Ionospheric Tomography From the Combination of GNSS and Upcoming LEO Constellations
Electron Density Reconstruction by Ionospheric Tomography From the Combination of GNSS and Upcoming LEO Constellations
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DOI：
10.1029/2020ja029074
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
X. Ren;Dengkui Mei;Xiaohong Zhang;Mohamed Freeshah;Si Xiong
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文献类型：
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作者：
X. Ren;Dengkui Mei;Xiaohong Zhang;Mohamed Freeshah;Si Xiong
基于全球导航卫星系统(GNSS)数据的电离层层析成像(CIT)是一个值得研究的课题。然而，诸如测站分布不均、缺乏数据和高海拔GNSS信号等主要问题可能会影响有关电离层的准确信息。为了解决这个问题，以前的许多研究主要是改进层析算法，而不是纳入多源数据，例如来自快速发展的即将到来的低地球轨道(LEO)卫星的数据。本文研究了全球范围内基于全球导航卫星系统的电离层层析成像的潜在改进，即结合即将到来的低轨卫星星座。在此基础上，对LEO增强GNSS电离层层析成像的性能进行了数值实验评估。具体地说，利用国际参考电离层(IRI-2016)模型分别模拟了2018年太阳活动低和2014年太阳活动高期间从地面接收器到GNSS(包括GPS、GLONASS、BDS和Galileo)和LEO卫星的电离层层析所需的倾斜总电子含量(STEC)。模拟的全球导航卫星系统单星、双星和四星系统的STEC值首次用于电离层层析成像。然后，将基于GNSS的STEC值与基于LEO的模拟STEC值相结合。直接从IRI-2016模型获得的、尚未在电离层层析成像中使用的STEC值被用作独立的参考。结果表明，GNSS+LEO解算结果总体上优于纯GNSS解算结果，GNSS+LEO解算得到的STEC值在太阳活动高年和低年与STEC参考值更加一致。与STEC参考资料相比，在太阳活动低年和高年，由CIT得到的仅用于GNSS解的STEC的均方根值最多可分别降低15%和20.3%。
Computerized ionospheric tomography (CIT) based on Global Navigation Satellite System (GNSS) data is a worthwhile project. However, predominant issues like unevenly distributed stations, lack of data, and high‐elevation GNSS signals could affect the precise information about the ionosphere. To address this problem, many previous studies were mainly improving tomographic algorithms, rather than incorporating multisource data such as data from rapidly developed upcoming Low‐Earth‐Orbit (LEO) satellites. In this paper, the potential improvements of GNSS‐based ionospheric tomography at a global scale by combining the upcoming LEO constellations is investigated. On this basis, some numerical experiments were conducted to evaluate the performances of LEO‐augmented GNSS ionospheric tomography. Specifically, the slant total electron contents (STEC) required for ionospheric tomography from ground receivers to GNSS (including GPS, GLONASS, BDS, and Galileo) and LEO satellites are simulated by the international reference ionosphere (IRI‐2016) model during low and high solar activity in 2018 and 2014, respectively. The simulated STEC values from single‐, double‐ and quad systems of GNSS constellations were first used for ionospheric tomography. Afterward, the GNSS‐based STEC values were combined with the LEO‐based simulated STEC values. The STEC values directly derived from the IRI‐2016 model that have not been used in ionospheric tomography were used as independent references. The results showed that the GNSS + LEO solutions outperform the GNSS‐only solutions overall, the STEC values obtained by GNSS + LEO solutions are more consistent with the STEC references during both high and low years of solar activity. In comparison with the STEC references, the RMS values of the CIT‐derived STEC for GNSS‐only solutions can be decreased by 15% and 20.3% at most during low and high years of solar activity, respectively.