LAUSR

The phase scintillation induced by ionospheric irregularities can reduce azimuth decorrelation and cause defocusing in the low-frequency spaceborne synthetic aperture radar (SAR) imaging. Thus, it demands for an autofocus approach to correct the scintillation phase error (SPE) and to refocus the deteriorated SAR image. However, the azimuth variation of the SPE has been rarely considered and poorly tackled in previous research studies. In this letter, an ionospheric phase screen (PS) projection method of phase gradient autofocus (PSP-PGA) is proposed to deal with this issue and compensate the azimuth-varying SPE in SAR images. The PSP is used to project the SAR image onto the PS, by using the part decompression and spectral analysis, so as to realize the decoupling of the SAR data with SPE. Then, the projected image can be directly applied to the PGA to accurately estimate the SPE. The proposed PSP-PGA is validated by using several simulation processing experiments and its performance is finally evaluated with respect to the parameter of the PS height.