Speakers
Description
SAR interferometric closure phases signal consists in a kind of inconsistency in triplets of interferograms. Closure phases have been shown to carry information about the propagation in semi-transparent media, typically the moisture status in soils and forests. Simple physical models can explain the phenomenon.
Recently, we have developed an inversion algorithm based on closure phases to retrieve the moisture variations from time series of interferometric SAR images. The crucial part in this algorithm is the solution of an ambiguity in model space, for which we propose the use of interferometric coherence or backscatter changes. Once this ambiguity has been solved correctly, the model inversion follows very easily. The results correlate with a number of well-established remote sensing products (e.g. scatterometers) and large scale models (like ECMWF).
Our real data experiments are mostly based on L-band data (ALOS-2). The closure phase and inverted moisture signal appear to be unexpectedly clean over some forested areas, which may allow applications like water status monitoring of forests and wildfire prediction.
Many issues remain open about the use of moisture products derived from closure phases: Is integration with backscatter-based techniques possible? If so, at which level of processing? How do we explain and exploit differences in polarization? To what extent it is possible to make use of C-band and higher frequencies data? Which spatial resolution is ultimately attainable?
At the workshop we will present inversion examples and validation data. We will also present first attempts with C-band Sentinel-1 data over especially coherent areas. The attached figure displays a closure phase map over a desert area after an unusual rain event.
