Validation of Ionospheric Parameters From Electron Density Profiles of FY‐3E Satellite Using Ionosonde, GIMs, Satellite Altimetry and Other Occultations

Abstract The FengYun‐3E satellite (FY‐3E) is the first to feature the GNSS Occultation Sounder II (GNOS‐II). Occultation is effective for ionosphere detection, but data variations between FY‐3E and other techniques are inevitable due to differing instruments and methodologies. Evaluating the GNOS‐II performance against other techniques is imperative. We extract ionospheric parameters—the F2 layer peak height (hmF2), F2 layer critical frequency (foF2), and Vertical Total Electron Content (VTEC)—from FY‐3E's electron density profile. We use ionosonde, Global Ionospheric Maps (GIMs), and Satellite Altimetry (SA), along with FY‐3D and COSMIC‐2 to analyze FY‐3E's performance. Additionally, we use the International Reference Ionosphere (IRI‐2020) to normalize VTEC, eliminating systematic biases due to altitude differences. Results show that FY‐3E's foF2 has high consistency with ionosonde, while hmF2 shows larger differences. However, both foF2 and hmF2 from FY‐3E, FY‐3D, and COSMIC‐2 have comparable data quality. TEC differences between FY‐3E and GIMs are greater during equinoxes and in the daytime. Significant TEC deviations are observed, particularly in low‐latitude region affected by the Equatorial Ionization Anomaly (EIA) during the daytime, with underestimation at EIA crests and overestimation at EIA troughs and around ±40° geomagnetic latitude, a phenomenon also observed when compared to SA. FY‐3D and COSMIC‐2 exhibit similar patterns, but FY‐3E shows better consistency with GIMs and SA compared to FY‐3D. Compared to FY‐3D and FY‐3E, COSMIC‐2 has fewer overestimated profiles. Furthermore, FY‐3E performs poorly in observing ionospheric structure in the EIA region but performs well in the Weddell Sea Anomaly (WSA) region, similar to FY‐3E.