Estimating and Removing Ionospheric Effects for L-Band Spaceborne Bistatic SAR

Lin, Haoyu; Deng, Yunkai; Zhang, Heng; Wang, Jili; Liang, Da; Fang, Tingzhu; Wang, Robert

doi:10.1109/tgrs.2021.3137860

Cited by 5 publications

(1 citation statement)

References 39 publications

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“…According to the statistical analysis and release data of the ionosphere, the vertical TEC is generally less than 120 TECU [31,32]. Thus, the impact of the background ionosphere on range signal imaging is quite weak given the general state of the ionosphere for L-band SAR with a resolution more than 3 m; meanwhile, for the L-band systems with a higher resolution (such as LuTan-1 [33]), the effects on range signal should be compensated.…”

Section: Error Model Of Time-variant Background Ionospheric Effects O...mentioning

confidence: 99%

Compensation of Background Ionospheric Effect on L-Band Geosynchronous SAR with Fully Polarimetric Data

2023

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The L-band geosynchronous synthetic aperture radar (GEO-SAR) has been widely praised for its advantages of short revisit time, wide coverage and stable backscattering information acquisition. However, due to the ultra-long integrated time, the echo will be affected by the time-variant background ionosphere, leading in particular to defocusing in the azimuth direction. Existing compensation methods suitable for low Earth orbit SAR (LEO-SAR) are based on the SAR image or the semi-focused image at the ionospheric phase screen, assuming that the ionosphere is time-frozen for a short integrated period; thus, accurate reconstruction of the time-variant characteristics for the ionosphere in GEO-SAR cannot be achieved. In this paper, a compensation method of background ionospheric effects on L-band GEO-SAR with fully polarimetric data is proposed. Considering the continuous variation of the ionosphere within the synthetic aperture, a decompression processing is proposed to reconstruct the echo by recovering the temporal sampling according to the imaging geometry. By virtue of the Faraday rotation angle, the time-variant total electron content (TEC) is accurately estimated with the reconstructed echo. Based on the established error model, the ionospheric effects are well compensated with the estimated TEC. Simulations with the real SAR data from ALOS-2 and the measured time-variant TEC from USTEC validate the effectiveness and performance of the proposed method. The impacts from thermal noise and polarimetric calibration error are also quantitatively analyzed. From this, the error thresholds are given to guarantee compensation accuracy, namely 18.96 dB for SNR, −15.63 dB for crosstalk and −1.02 dB to 0.31 dB for the amplitude of the channel imbalance, and the argument of the channel imbalance is suggested to be maintained as close to zero as possible.

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Section: Error Model Of Time-variant Background Ionospheric Effects O...mentioning

confidence: 99%