Sea Ice Thickness Measurement Using Spaceborne GNSS-R: First Results With TechDemoSat-1 Data

Abstract

In this article, an effective schematic is developed for estimating sea ice thickness (SIT) from the reflectivity ( $\Gamma$ ) produced with TechDemoSat-1 (TDS-1) Global Navigation Satellite System-Reflectometry data. Here, $\Gamma$ is formulated as the product of the propagation loss due to SIT and the reflection coefficient of underlying seawater. The effect of surface roughness on $\Gamma$ is neglected when only considering signals of coherent reflection. In practice, $\Gamma$ at the specular point is first generated using TDS-1 data. Afterwards, SIT is calculated from TDS-1 $\Gamma$ based on the proposed reflectivity model, and verified with two sets of reference SIT data; one is obtained by the Soil Moisture Ocean Salinity (SMOS) satellite, and the other is the combined SMOS/Soil Moisture Active Passive (SMAP) measurements. This analysis is performed on the data with SIT less than 1 m. Through comparison, good consistency between the derived TDS-1 SIT and the reference SIT is obtained, with a correlation coefficient ( $r$ ) of 0.84 and a root-mean-square difference (RMSD) of 9.39 cm with SMOS, and an $r$ of 0.67 and an RMSD of 9.49 cm with SMOS/SMAP, which demonstrates the applicability of the developed model and the utility of TDS-1 data for SIT estimation. In addition, this method is proved to be useful for improving existing sea ice detection accuracy.