Observations of Oil Pollution on the Ocean by an X-band SLAR System

Abstract

This report describes the results of oil-slick observation experiment using an X-band SLAR (Side-looking Airborne Radar) developed in our research program from 1984 to 1986. The purposes of the experiment are to verify the ability of oil slick detection by the SLAR and to clarify the properties of Δσ°(the difference of backscattering cross-sections between clean and slick ocean surfaces) which is the most important parameter for the SLAR observation of ocean oil slicks. In the experiment, two kinds of oil slick were observed : artificial and natural oil slicks. From the artificial slick observation, it was found that even a small slick made with only 18-liter oleyl-alcohol can be clearly detected. The following properties of Δσ°were also clarified : (1) Δσ° shows clear azimuth-angle dependence for the incident angle range from 30°to 80°, (2) incident angle dependence of Δσ° is not large for the same range, (3) Δσ° appears to decrease gradually at incidence angles larger then 80°. From the natural slick observation, it was found that very small (about 50m×50m) slicks can be detected and that Δσ°was approximately the same as the value for the artifical slick. These results indicate that the SLAR
has a very high sensitivity in oil slick detection over a wide incident angle range. Based on the results of our experiment and those of other investigators, SLAR observation parameters suitable for oil slick detection are also discussed.