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

The FY3C/GNOS launched in 2013 can only detect the scintillation of GPS navigation signals, while the FY3D satellite launched in 2017 supports the scintillation observation of BeiDou navigation satellite system (BDS) signals, thus enabling simultaneous detection of GPS and BDS ionospheric scintillation. This work presents a preliminary accuracy evaluation of BDS ionospheric scintillation observed by the global navigation satellite system (GNSS) occultation sounder (GNOS) onboard the FY3D satellite, to support long-term ionospheric scientific applications based on the BDS system. First, the F-layer worst-case (maximum) amplitude scintillation index ($S4_{\text{max}}^F$) of FY3D-BDS, FY3D-GPS, and COSMIC-GPS are, respectively, quality-controlled, and the spatial-temporal matching of $S4_{\text{max}}^F$ between FY3D-BDS and FY3D-GPS/COSMIC-GPS is performed. Then, based on the statistical deviation (std) of the $S4_{\text{max}}^F$ data pairs, the data accuracy of FY3D-BDS $S4_{\text{max}}^F$ relative to FY3D-GPS and COSMIC-GPS is obtained. The results show that the std of the $S4_{\text{max}}^F$ differences in data pairs between FY3D-BDS and FY3D-GPS/COSMIC-GPS is smaller than 0.1, which proves the high precision of BDS ionospheric scintillation detection of FY3D/GNOS. Meanwhile, the std of the $S4_{\text{max}}^F$ differences between FY3D-BDS and FY3D-GPS/COSMIC-GPS at nighttime is higher than that at daytime, and the std in the mid-latitude region is lower than that in the low-latitude and high-latitude regions.