Oil spill monitoring

Patrol ships and aircraft ensure continuous monitoring of coastal waters. Because of the high costs involved in patrolling extensive areas, these surveys require careful planning.

Until recently, large scale monitoring was possible only by using aircraft (photo courtesy of Swedish Space Corporation), but this method was and is still very expensive. Few countries can afford routine airborne surveys so, to minimize costs, their geographic coverage is limited.
With the advent of Earth observation satellites, extensive and repetitive surveys have become possible. When compared with similar airborne systems, space-based redars can provide more cost-effective monitoring.

The ERS satellites observe the Earth with microwave radar swaths 100 Km wide. Nominal image resolution is 25x25 m. For oil spill detection, low resolution images of 100x100 m are used; this reduces the size of the data files by up to 2 Mbytes or less. Oil spill detection is possible under wind speed conditions ranging from 6 to around 23 knots (3-12 m/sec). Within this range, the wave damping action of an oil film is most effective.

The microwave backscatter is greatly reduced in these areas as compared to the surrounding oil-free water.
ERS-1 images are already used for monitoring oil spills. Maintaining surveillance of large areas with the help of satellite imagery means that not only can occasional small spills be identified (whether accidental or intentional), but also that their spreading and displacement can be monitored.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry