Using ERS-2 SAR images for routine observation of marine pollution in European coastal waters

More than 400 synthetic aperture radar (SAR) images acquired over the southern Baltic Sea, the North Sea, and the Gulf of Lions in the Mediterranean Sea by the Second European Remote Sensing Satellite (ERS-2) have been analyzed since December 1996 with respect to radar signatures of (natural and anthropogenic) oil pollution and other phenomena causing similar signatures. First results of this analysis reveal that the seas are most polluted along the main shipping routes. SAR images acquired during descending (morning) and ascending (evening) satellite passes show different percentages of oil pollution, because most of this pollution occurs during night time and is still visible on the SAR images acquired in the morning time. By using an ERS-2 SAR image of the North Sea test area we show how the reduction of the normalized radar backscattering cross section (NRCS) by an oil spill depends on wind speed. In order to point out the difficulties in detecting oil pollution undoubtedly, we finally present signatures of atmospheric and oceanic phenomena which are very similar to those of marine pollution.