Retrieval of ionospheric TEC over oceans From GNSS-R delay-Doppler map
In this paper, an approach is presented to retrieve ionospheric total electron content (TEC) over oceans from Global Navigation Satellite System-Reflectometry (GNSS-R) delay-Doppler map (DDM). Here, an additional ionospheric delay (τI) is considered in the conventional DDM simulation process. Based on this, the least squares (LS) fitting method is employed for TEC retrieval by fitting the simulated DDMs with different τI values to the measured DDM. Meanwhile, an adaptive threshold is adopted in the fitting process to restrain the intrinsic errors due to DDM mismatching. The proposed method is validated by comparing the retrieved TEC results based on three datasets from the SSTL UK-DMC satellite with the TEC values produced by the International Reference Ionosphere (IRI)-2012 and the NeQuick 2 models. A good consistency is obtained.