Synthetic aperture radar (SAR) is now commonly used for operational oil spill monitoring. During major spills SAR data from different satellites give an overview of the areas affected and provide information on the direction in which surface oil is drifting. SAR is also used to monitor illegal discharges from ship traffic or offshore operations. In many areas this has helped to reduce oil pollution.
In regions that are relatively cloud free data from optical sensors such as MERIS and MODIS are increasingly used. Combining SAR and optical data makes detection of small spills more reliable and can provide additional information for use in oil spill response during larger spills.