NISAR Complementary Interferometric phase fusion of S & L band - A Simulation Study

NASA and the Indian Space Research Organization (ISRO) are collaborating on the Synthetic Aperture Radar (SAR) mission known as NISAR, which was launched on 30 July 2025. It will undergo a 90-day initial phase operation . The NISAR mission features two SAR sensors on a single satellite platform: one operating in the L-band from NASA and the other in the S-band from ISRO. NISAR will provide simultaneous data from two Interferometric SAR (InSAR) pairs—one in the S-band and one in the L-band—on a 12-day repeat pass orbit cycle. In this paper, we explore the potential for multi-frequency complementary interferometric phase fusion using simulated data from both the S-band and L-band. We propose a methodology aimed at generating a high-quality, improved fused S-band interferogram by combining the complementary phase information from the L-band interferogram. The methodology consists of three main processes. The first process for SAR Raw Data Simulation. This process generates S-band and L-band SAR interferometric pairs utilizing the NISAR sensor parameters. During this simulation, two datasets were created: the first simulated with short vegetation, and the second simulated with shrub vegetation surface backscattering coefficients. The second process is the InSAR Process. This step generates interferograms for both the S-band and L-band using the simulated datasets. The third process is the InSAR Phase Fusion Process. The final step involves fusing the InSAR phases to create a new, improved fused S-band interferogram. This fused S-band interferogram is designed to provide high-resolution unwrapped phase values while minimizing phase errors. The results are promising and show significant improvements compared to using a single-frequency InSAR pair.