The Directive tasks EMSA to ‘work with the Member States in developing technical solutions and providing technical assistance in actions such as tracing satellite discharges by satellite monitoring and surveillance’. Therefore the Agency has established a European wide operational system for oil slick detection based on Synthetic Aperture Radar (SAR) images from satellites. This service, called CleanSeaNet, supplements existing surveillance systems at national and regional level and supports Member States response to illegal discharges and accidental spills as well as helping to locate and identify polluters in areas under their jurisdiction.
CleanSeaNet uses SAR satellite images primarily from ENVISAT ASAR (ESA) and RADARSAT-1 and RADARSAT-2 (CSA/MDA). Looking to the future the planned GMES Sentinel-1 mission series will be important for routine monitoring, while other X-band radar data from TerraSAR-X (DLR) and CosmoSkyMed (ASI): could potentially be used in case of an oil spill emergency. After acquisition by the satellite, SAR data are transmitted to a network of ground receiving stations, where the data is processed and the image interpreted by image analysts. The analysed satellite imagery is available to the relevant Coastal State operational users within 30 minutes after satellite overpass. In case of a detected oil slick, an alert message to the end user is transmitted by phone call as well as e-mail and optionally by fax or SMS. The final verification of the possible slick needs to be done by in-situ means such as patrol vessel or ideally by aerial surveillance. National aerial and vessel surveillance patrols can then target this area to verify the possible spill and potentially identify the polluter. By complementing national aerial and vessel surveillance with satellite images a more cost effective use of these expensive resources is achieved.
Image 1: A CleanSeaNet Envisat ASAR satellite image acquired in February 2009 alerted the Irish Coastguard of an extensive oil slick approximately 50 miles South East of Fastnet Rock off the West Cork coast of Ireland.
CleanSeaNet began operating in April 2007 and oil pollution response authorities of 24 European Coastal States have access to the service. Since the beginning of the service over 400,000,000km2 of European seas have been monitored. More than 4000 possible oil slicks have been detected, but not all of these detections were oil. A study conducted after 18 months of operations showed that the percentage of detections checked on-site by aircraft or patrol vessels and confirmed as oil varies from one region to another but can reach values as high as 80%.
SAR image data is able to detect ships and quite often their wakes. In order to identify vessels suspected of causing pollution, traffic monitoring information from AIS (Automatic Identification Systems) and LRIT (Long Range Identification and Tracking) data is necessary. Later in 2009 CleanSeaNet will provide vessel track information as an added layer on top of the SAR image. Therefore it shall be possible to link a recent spill to a vessel if the vessel is shown to be attached to the spill, or if the track matches pattern and shape of the spill and if there is no confusion between the different vessels observed in the vicinity of the slick.
Image 2: An illegal oil discharge was detected in this CleanSeaNet satellite image acquired in June 2009 off the coast of Spain. The polluting vessel was also detected in the SAR image. Vessel track information taken from the SafeSeaNet AIS database identified the ship responsible for causing the pollution.
Oil spill modelling tools further assist in the identification of vessels responsible for illegal discharges (spill backtracking) and for prediction of spill drift and fate (spill forecasting) to support decision making for pollution response activities. Backtracking of spills and the intersection of the spill trajectory with vessel tracking data can limit the number of potential polluters and allows authorities to carry out more in-depth checking of suspicious vessels. Beginning in 2009 EMSA plans to integrate oil spill modelling capabilities within CleanSeaNet in co-operation with model operators at Coastal States. In the future the service will be further enhanced by the inclusion of additional information to Coastal States, such as sea surface temperature maps, surface chlorophyll maps, and reference data sets including nautical charts.
The Agency has recently launched an open invitation to tender for the “EMSA CleanSeaNet Data Centre”, part of the 2nd generation CleanSeaNet to be in place from 2011. The procurement includes the design, development, implementation, and maintenance of the CleanSeaNet Data Centre (CSN DC) The CSN DC information system shall provide a platform for the Agency to manage Earth Observation data. The data will be stored and managed by the CSN DC and distributed to CleanSeaNet users. The CSN will guarantee an advanced platform for the alerting, visualisation, dissemination, ingestion, and archiving of both data and information.
Further information on CleanSeaNet and this tender can be found at: http://cleanseanet.emsa.europa.eu/