GNSS ionospheric model performance under non-nominal conditions: CMEs and Solar Eclipse

Global Navigation Satellite System (GNSS)-based navigation is usually carried out in open sky conditions, where one of the main error sources is introduced by the ionosphere. Ionospheric effect can be mitigated by combining two GNSS signals at different frequencies exploiting the dispersive behavior of the ionosphere. Unfortunately, most of the mass-market receivers do not benefit from this cancellation since they are single frequency receivers, hence they have to apply a model to reduce the ionospehric effects. In this work three models are considered, specifically Klobuchar, NeQuick-G and Global ionospheric Maps (GIMs). In this context, it is important to evaluate the response of these models to non-nominal ionospheric conditions, such as the geomagnetic storm on March 17, 2015 followed by a Solar Eclipse on March 20. The combination of these phenomena generates a unique scenario to test the discrepancies of the broadcast ionosphere with the real one. The performance is evaluated in the measurement domain computing the delay by the above mentioned models and comparing it with respect to the reference delay computed using post-processed Vertical Total Electron Content (VTEC) maps provided by the International GNSS Service (IGS). In order to analyze the impact of the Coronal Mass Ejection (CME) and the Eclipse, a performance analysis is carried out also in the position domain, applying different ionospheric algorithms. In this work, experiments to compare the performance of different ionospheric modelling methods, and to evaluate their robustness in non-nominal conditions, are conducted. The performance is evaluated using data from three different IGS stations.