SMAP-Reflectometry: Dataset, Calibration and Sensitivities to Geophysical Parameters of Compact Polarimetric GNSS-R

The Soil Moisture Active Passive (SMAP) mission was conceived to provide collocated radar and radiometry measurements at L-band to estimate surface soil moisture at moderate spatial resolutions (9 km). Months after its launch, the radar suffered an anomaly that prevented its nominal operation. This was seen as an opportunity to change its central frequency to GPS L2C (1.227 GHz) [1], [2]. Since then, the SMAP radar receiver is a polarimetric Global Navigation Satellite System – Reflectometer (GNSS-R), collecting for the first time from space two orthogonal polarization components of a GNSS reflection. Initial analyses were conducted using the ratio between the two SMAP linear polarizations (Horizontal, H, and Vertical, V) [1], [3], [4], and preliminary analysis using full polarimetry (i.e., H, V, right and left-hand circularly polarized, RHCP and LHCP, respectively) where performed in [5] by synthetically composing the circular polarization components from the cross correlation of the complex voltages of the H and V channels. Recently, the authors of this abstract continued the work in [5] providing a complete mathematical definition of the polarimetric scenario defined of the SMAP-Reflectometer (SMAP-R) [6].