A large time series of 42 dual-polarimetric co-polarized TerraSAR-X (TSX) StripMap Synthetic Aperture Radar (SAR) measurements are exploited to monitor a well-known oil seep area, i.e., the Taylor Energy site in the Gulf of Mexico. A comprehensive scattering analysis is undertaken to assess the impact of SAR imaging parameters (polarization, angle of incidence-AOI, noise floor) and environmental conditions (wind speed-WS, oil properties) on single-polarization SAR-based sea oil seep observation. The main goal of this study is to evaluate the reliability of the scatteringbased information derived from the time series of TSX SAR imagery. A two-scale backscattering model is considered to give a physical framework that supports a better understanding of the effects of the above-mentioned factors. Experimental results showed that the high TSX noise floor significantly limits a reliable interpretation of the slick-free sea surface and oil seep backscattering at AOIs larger than 34 and 26 , respectively, since they are contaminated by noise. Hence, it is shown that, at larger AOIs, the joint contribution of noisy SAR measurements and low oil backscattering does not result in a larger oil/sea separability. The latter is not remarkably influenced by polarization and WS, under low-to-moderate conditions. Experiments also demonstrate that, when reliable SAR measurements are available, sea oil seep backscattering is affected by the oil's damping properties more than its concentration in the water column. The time variability of the polluted area is also estimated using the time series of TSX imagery and the obtained results agree with independent analysis undertaken on the same test site.

In this study, a time series of 33 TerraSAR-X co-polarized Synthetic Aperture Radar (SAR) imagery collected in Stripmap mode over the Gulf of Mexico in a wide range of incidence angles and sea state conditions, is exploited, together with a theoretical framework based on the X-Bragg scattering model, to analyze the effects of noise, angle of incidence (AOI) and wind speed on the standard deviation of the co-polarized phase difference (σ φc ) evaluated over sea surface with and without oil slicks. This large dataset represents an unprecedented opportunity to analyze, for the first time, the influence of both SAR acquisition and surface parameters on the broadening of the co-polarized phase difference probability density function (pdf), p φc (φc). Experimental results show that the X-Bragg scattering model, here adopted to predict the sea surface p φc (φc), gives an understanding of the increasing trend of σ φc with respect to AOI. It is shown that the noise significantly contributes to broaden p φc (φc) over both slick-free and slick-covered sea surface, while the effects of low-tomoderate wind regimes are negligible. In addition, σ φc exhibits a larger sensitivity to the scene variability, if compared to single-polarization intensity channels, over both slick-free and oil-covered sea surface. This sensitivity is more pronounced at lower AOIs due to the higher noise equivalent sigma zero (NESZ) that affects larger AOIs.

This study aimed at analyzing the effect of Synthetic Aperture Radar (SAR) imaging parameters and environmental conditions on the standard deviation of the co-polarized phase difference (sjC ) evaluated over sea surface[...]

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