There are two main types of sensor used for earth observation purposes:
- Synthetic Aperture Radar (SAR) sensors use radar frequencies to construct an image of the sea (or land) surface below. Images can be acquired regardless of weather conditions and cloud cover, and at any time of day or night. By measuring the roughness of the sea surface, certain features stand out against the background; for example, vessels appear as bright spots, while oil spills appear as dark shapes.
- Optical sensors can provide a wealth of information in different spectral bands. They provide easier image interpretation and object identification due to the combination of Red-Green-Blue (RGB) and infra-red frequencies, albeit with very high dependency on sunlight and weather conditions. Optical sensors cannot capture images during the night or in cloud cover conditions.
