Remote Sensing

Remote sensing radars are used to identify objects and landscapes through the transmission of pulsed microwave (radio wave) beams. The beams bounce off, and are altered by, objects and surfaces they come into contact with (termed backscatter).  The backscatter is transmitted back to the satellite, and the strength and origin of these returning reflections is captured by sensors. The resulting data can be analysed to provide information of varying kinds, for example whether a sea surface area has an unusual texture which may be due to spilt oil. Synthetic Aperture Radar (SAR) sensors have enhanced capabilities for transmitting and receiving beams, and therefore produce higher quality images.

The CleanSeaNet service uses radar images acquired by SAR sensors on polar orbiting satellites. Active microwave sensors like SAR are an important tool in oil spill monitoring as they provide wide area coverage and have the capability to detect oil slicks on the sea surface in both darkness and daylight hours and to see through the clouds. Examples of SAR sensor satellites are ENVISAT and RADARSAT 1 and 2.

Optical Sensors

Optical sensors detect reflected sunlight, rather than microwaves.  For this reason, they can only be used during daytime and in good weather conditions (free of cloud cover). Pilot projects and activities undertaken in the scope of CleanSeaNet have used optical images, and their future integration as a regular part of the CleanSeaNet service is envisaged in 2011.