An Improved Ionospheric Correction Model for Grazing Angle GNSS-R Altimetry

In this work, Spire Global, Inc. carrier phase of GNSS dual-frequency reflected signals under grazing angle (GG-R) are used for sea surface altimetry over the Java Sea, Indonesia. Processing of 714 GG-R coherent profiles from January 2020 to October 2021 is carried out to retrieve the relative surface height from WGS84 applying two methods to remove the ionospheric delay: an ionosphere-free combination and smoothing of the frequency-specific correction based on dual-frequency carrier phase observations. A substantial improvement of ∼ 8 cm is observed in the root mean square error (RMSE) between the GG-R retrievals and the reference surface model using the frequency-specific ionospheric correction method.