On the Phase Nonclosure of Multilook SAR Interferogram Triplets

This work explores the properties characterizing the phase nonclosure of multilook (ML) synthetic aperture radar (SAR) interferograms. Specifically, we study the implications of ML phase time incongruences on the generation of ground displacement time series through small baseline (SB) multitemporal InSAR (Mt-InSAR) methods. Our research clarifies how these phase inconsistencies can propagate through a time-redundant network of SB interferograms and contribute, along with phase unwrapping (PhU) errors, to the quality of the generated ground displacement products. Moreover, we analyze the effects of short-lived phase bias signals that could happen in sequences of SB interferograms and propose a strategy for their mitigation. The developed methods have been tested using both simulated and real SAR data. The latter were collected by the Sentinel-1 A/B (C-band) sensors over the study areas of Nevada, USA, and Sicily, Italy.