Abstract
The Chinese first fully polarimetric space-borne synthetic aperture radar (SAR)-Gaofen-3 (GF-3) was launched in August 2016, which operates at the C-band and the resolution can reach 1 m. Polarimetric SAR calibration is a procedure that corrects the polarization distortion of a measured scattering matrix by referring to the scattering matrix of a known target. The present paper describes the principle, design, manufacture, and measurement results of a novel polarimetric active radar calibrator (PARC) designed for GF-3. A new design method for PARC was presented and two dual-polarized antennas with very high polarization purity were used. The internal calibration technique was introduced to ensure balance in the amplitude and phase, which ensures the precision of the PARC’s scattering matrices. The results we obtained through measurement in the microwave anechoic chamber and experiments in in-orbit calibration agree well with the theoretical predictions, and the novel PARC presented is proved to be well suited for polarization and radiometric calibration of GF-3.
Highlights
The Chinese satellite, Gaofen-3 (GF-3), was launched in August 2016
The polarimetric active radar calibrator (PARC) we developed have been utilized for the in-orbit calibration campaign of the GF-3
The PARCs of Radarsat-2 and Sentinel-1 that use rotating in the amplitude and phase, we did realize this through the amplitude and phase internal antennas do not have this problem because only one radio frequency (RF) channel is used
Summary
The Chinese satellite, Gaofen-3 (GF-3), was launched in August 2016. It is the first satellite ofChina equipped with a fully polarimetric synthetic aperture radar (SAR), which operates at the C-band and its highest resolution can reach 1 m [1]. Compared to conventional single polarimetric SAR, the fully polarimetric SAR can obtain a variety of polarimetric information of targets. It provides a wide aspect of targets with a scattering matrix. When the scattering matrix of a target is measured with the fully polarimetric SAR, it usually gets distorted due to the imperfect polarization transfer characteristics of the SAR’s transmitting and receiving antennas. This polarization distortion in the measured scattering matrix must be removed before the data can be used in several polarimetric applications. This procedure is called polarimetric calibration [5,6]
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