Ionospheric Error Correction Methods for InSAR Measurements: A systematic review

Spaceborne interferometric synthetic aperture radar (InSAR) has emerged as a crucial geodetic tool for surface deformation monitoring with wide area, high precision, and high resolution. The increasing utilization of low-frequency (LF) (e.g., L-/P-band) SAR systems provides distinct advantages in addressing phase unwrapping and decorrelation challenges, making them indispensable for geological hazard monitoring. However, these LF SAR signals are particularly vulnerable to ionospheric disturbances, posing a significant challenge in maintaining the accuracy of the InSAR measurements. This study provides a systematic review of ionospheric error correction techniques for InSAR, focusing on errors in the line of sight (LOS) and azimuth. The spatiotemporal characteristics of the ionosphere and their impact on SAR and InSAR observations are first reviewed. Subsequently, the principles, methodologies, and performance of various ionospheric correction techniques for SAR LOS and azimuth directions are systematically analyzed. Finally, the key challenges and perspectives in InSAR ionospheric error correction are outlined. The ionosphere is expected to remain a research focus within the InSAR community as LF SAR satellites will continue to develop. Additionally, InSAR ionospheric correction methods offer a promising pathway for high-spatiotemporal-resolution ionospheric mapping, with potential applications in studying space weather and geospace physics.