Abstract
We conducted experiments on detecting intentionally oil polluted areas using the C-band Synthetic Aperture Radar on the European Remote Sensing Satellite-1 in November 1991 and in October and November 1992. Intentionally polluted areas were produced by spilling oleyl alcohol from a small ship in the Pacific Ocean about 100 km off the coast of Japan. Sea truth data were collected by both a research vessel and the small ship which is used to spill the alcohol. The ERS-1 SAR images were processed by NASDA. The intentionally polluted areas appeared as dark patch area on the SAR image. This is because slick damps surface capillary waves and makes ocean surface smooth, and slick appears as dark patch area in the SAR image. The intentionally polluted areas were clearly detected by ERS-1 SAR under various wind speeds of less than 11m/s. While we expected the damping decreases as the wind speed increases, the maximum damping of the scattered power was nearly the same (4 to 5 dB) for wind speeds of less than 11m/s. This may be because of the small incidence angle of 23° where the effect of quasi-specular scattering still remains. However, the ERS-1 SAR did not detect the intentionally polluted areas when the wind speed was 13.7m/s. Although we cannot state any definite reasons, we suppose that intentionally polluted areas may have been scattered out by the strong wind and could not make damp surface capillary waves produced by strong wind. We need further analysis and experiment under strong wind conditions.
