Lidar as part of an ROV-based sensor network for the detection of chemical pollutants on the seafloor

The seafloor may be polluted by hazardous chemicals in different forms, e.g., as a sinker pool or stored in a sunken container. Although techniques exist for a recovery, instruments for the detection, especially in turbid waters, are still unsuitable. The variety of substances and scenarios requires a number of strategies based on different physical and chemical principles. To complete the existing surveillance system in the German Bight, the German Ministry of Transport intends to operate an ROV which can be equipped with instruments for in situ water analysis and remote sensing of the seafloor. Besides commercially available sensors like CTD probes, the system includes several newly developed underwater instruments: gas chromatography and mass spectrometry, quartz microbalance detectors, acoustic sensor for impedance measurements and lidar. Instruments and control unit on board the operating ship are connected to a database via ethernet which allows for a fast and efficient combined data interpretation. One of the remote sensing instruments integrated in the payload of the ROV is a submarine lidar. It is a combination of a range gating video camera and a fluorescence lidar. The range gating video camera takes contrast enhanced images from the seafloor in turbid waters. Therefore it is used to search for and-in case of success-to inspect lost containers on the ground. The fluorescence lidar is used to detect chemicals which are normally invisible on video images. The analysis of fluorescence spectra allows substances to be classified