Observations and mitigation of RFI in ALOS PALSAR SAR data: Implications for the DESDynI mission

Initial examination of ALOS PALSAR synthetic aperture radar (SAR) data has indicated significant radio frequency interference (RFI) in several geographic locations around the world. RFI causes significant reduction in image contrast, introduces periodic and quasi-periodic image artifacts, and introduces significant phase noise in repeat-pass interferometric data reduction. The US National Research Council Decadal Survey of Earth Science has recommended DESDynI, a Deformation, Ecosystem Structure, and Dynamics of Ice satellite mission comprising an L-band polarimetric radar configured for repeat-pass interferometry. There is considerable interest internationally in other future L-band and lower frequency systems, as well. Therefore, the issues of prevalence and possibilities of mitigation of RFI in these crowded frequency bands are of considerable interest. RFI is observed in ALOS PALSAR in California and Hawaii, USA, and in southern Egypt in data examined to date. Application of several techniques for removing it from the data prior to SAR image formation, ranging from straight-forward spectral normalization to time-domain, multi-phase filtering techniques, are considered. Considerable experience has been gained from the removal of RFI from P-band acquired by the GeoSAR system. These techniques applied to the PALSAR data are most successful when the bandwidth of any particular spectral component of the RFI is narrow. Performance impacts for SAR imagery and interferograms are considered in the context of DESDynI measurement requirements.