On the monitoring of illicit vessel discharges using spaceborne SAR remote sensing - a reconnaissance study in the Mediterranean sea

For much of the last century, the degradation of the sea due to ship pollutions has been recognized as a major concern. Early in the thirties, seven major maritime nations proceeded voluntarily to abating measures of oil discharges from tankers. But from then, it took four decades until the international community reaches a widely accepted agreement, namely the MARPOL 73/78 convention. Within a number of regional seas, declared as Special Areas, the regulations are even stricter, prohibiting ship discharges almost totally. To ensure verification, as well as instigation for compliance, effective capabilities for monitoring and intervention are necessary. Key element for successful monitoring however is the regular remote surveillance. To a certain degree this is supported via routine airborne patrol operations, based either on visual inspection or on remote sensors, functioning in the microwave, infrared and ultraviolet spectral regions. Such operations are carried out only over limited geographic areas, since it is not feasible, technically and/or financially, to spread aerial surveillance over the entire breadth of the European waters. As a result, the compliance with the regulations is not applied everywhere with the same care. Satellites equipped with SAR (Synthetic Aperture Radar), due to their capability to detect oil spills on the sea surface, as well as to survey large areas of the sea independently of sunlight and cloud coverage, appear to be ideal for complementing the conventional airborne means. Nevertheless, despite such successful pioneer efforts, many would still argue that the potential of what could be achieved with the spaceborne sAR surveillance, in monitoring illicit vessel discharges, has been somehow oversold. This document concerns exclusively the problem of monitoring ship discharges with spaceborne SAR. We distinguish them from major accidental pollution caused by ships in distress, because the unique singularities of the later pose different requirements for investigation. We present the main results of a regional reconnaissance study carried out over the entire Mediterranean Sea during the year 1999.