Accuracy Evaluation of the Worst-Case BDS Scintillation in F-Layer Observed by GNOS Onboard FY3D Satellite

While FY3C-GNOS (FengYun3C-Global Navigation Satellite System Occultation Sounder) can only observe the ionospheric scintillation of Global Positioning System (GPS) radio occultation signals, FY3D-GNOS adds the scintillation monitoring of BeiDou Navigation Satellite System (BDS) occultation signals, which can realize the simultaneous detection of BDS and GPS ionospheric scintillation. This work provides the first preliminary assessment of the BDS ionospheric scintillation data detected by FY3D-GNOS, thus supporting the subsequent development of long-term integrated ionospheric scientific applications based on the BDS. The worst-case scintillation index in F-layer ($S4_{max}^F$) of FY3D-GNOS and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) in 2019 are quality-controlled, spatial-temporally matched, then the deviation statistics are performed to assess the accuracy of the BDS scintillation index. The results show that the bias and standard deviation(std) of matching $S4_{max}^F$ pairs between FY3D BDS and COSMIC are −0.025 and 0.082 at wholeday, −0.023 and 0.081 at daytime, and −0.027 and 0.083 at nighttime, which proves the reliability and accuracy of FY3D-GNOS BDS scintillation detection.