Investigation of spaceborne polarimetric GNSS-R using the SMAP radar instrument

GNSS-R (Global Navigation Satellite System Reflectometry) is being increasingly used in Earth remote sensing applications; however, up until now, dual-polarized data from spaceborne instruments has not been available. Recently, the radar aboard the SMAP satellite has provided raw received signal data on the GPS L2C frequency band. This data is simultaneously received from two high-gain (36 dBi), dual-polarized channels with excellent cross-polarization isolation. It is currently the only instrument capable of providing high-quality, dual-polarized GNSS-R measurements from space and represents a unique opportunity to study polarimetric scattering properties of geophysical phenomena. This paper presents dual-polarized GPS L2C reflection measurements made using the SMAP data over different ocean (including tropical cyclones) and land surface types. A full, high-fidelity forward SMAP GNSS-R model has been developed and applied in order to interpret scattering properties from the complex Delay-Doppler Map (DDM) data.