Abstract
The GaoFen-3 (GF-3) satellite is the first polarimetric synthetic aperture radar (PolSAR) satellite in China. With a designed in-orbit life of 8 years, it will provide large amounts of PolSAR data for ocean monitoring, disaster reduction, and many other applications. The polarimetric data quality is essential for all these applications, so the analysis and calibration of the polarimetric error sources are very important for GF-3. In this study, we established a full-link error model for GF-3 PolSAR system. Based on this model, we comprehensively analyzed the quantitative effects of the main error sources including the composition, figured out characteristics of the phase imbalance introduced by the antenna, and pointed out the error sources which have to be corrected. Furthermore, the polarimetric correction method for GF-3 PolSAR system is proposed. Finally, assisted by several external calibration experiments, polarimetric errors of GF-3 data are efficiently corrected during in-orbit-test phase.
Highlights
The first multi-polarization SAR in China, GaoFen-3 (GF-3) satellite, was launched on 10 August 2016
We presented the calibration of polarimetric error for GF-3 polarimetric synthetic aperture radar (PolSAR) system
The error sources affecting GF-3 polarization observation are analyzed comprehensively, including: (1) the channel imbalance of the transmit/receive channel; (2) sampling delay error introduced by the transmit/receive channel; (3) the isolation and channel imbalance of the antenna array; (4) the POA caused by satellite attitude; (5) the FR introduced by the ionosphere
Summary
The first multi-polarization SAR in China, GaoFen-3 (GF-3) satellite, was launched on 10 August 2016. The calibration and the correction of the polarimetric error is a very important procedure for generating the high quality PolSAR image products. The GF-3 satellite obtains full-polarization images by alternately transmitting horizontal (H) and vertical (V) polarized pulses and receiving backscattering signals in both H and V polarization [8] It possesses two Full Polarized Strip Modes (QPSI and QPSII). All beams have multiple options of bandwidth and pulse duration With these multiple polarization modes, multiple beams and multiple bandwidths, GF-3 PolSAR can obtain more than 250 kinds of data under different system conditions, which may cause different polarimetric errors. SAR satellites with the capability of polarimetric observation such as SIR-C, RADARSAT-2, TerraSAR-X and ALOS-2 have been successfully launched and calibrated for polarization errors, which provide good references for GF-3 data processing. Pq means different polarization combinations, where received by p polarization and transmitted by q polarization
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