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Stokes Parameters Retrieval and Calibration of Hybrid Compact Polarimetric GNSS-R Signals

2022; Institute of Electrical and Electronics Engineers; Volume: 60; Linguagem: Inglês

10.1109/tgrs.2022.3178578

1558-0644

Joan Francesc Muñoz-Martín, Nereida Rodriguez-Alvarez, Xavier Bosch-Lluis, Kamal Oudrhiri,

Synthetic Aperture Radar (SAR) Applications and Techniques

Global Navigation Satellite System – Reflectometry (GNSS-R) is a promising field with a diverse set of applications. Polarimetric GNSS-R has been shown to be sensitive to different land parameters, such as freeze/thaw, crop growth, or soil moisture. In this manuscript, the polarimetric scenario of a GNSS reflection is defined, and the theoretical basis and the algorithm to retrieve the Stokes parameters of a GNSS-R signal is proposed. The presented algorithms are validated using data collected by the two linear orthogonal polarization channels of the SMAP radar antenna working as GNSS-R, known as SMAP-Reflectometry (SMAP-R). The Stokes parameter retrieval is presented for the SMAP-R case, and the receiver phase offset and intensity are calibrated. The same calibration procedure proposed by the CYclone GNSS (CYGNSS) mission is applied to the SMAP-R first Stokes parameter, allowing the retrieval of the normalized bistatic radar cross section of such measurement. Finally, the SMAP-R data is compared to the CYGNSS Normalized Bistatic Radar Cross Section (NBRCS) over the ocean, showing an unbiased root-mean-square error of 3.3 dB, and a small bias.