An optical spectrometer is an instrument used to detect, measure and analyze the spectral content of the incident electromagnetic field (narrow-band, VIS, NIR, SWIR and TIR). It breaks down the incoming light spectrum so the whole wavelength range is mapped and each wavelength can be analysed individually. Usually, a distinction is made between optical and mass spectrometers.
Optical spectrometers depict the intensity of the incoming light in function of the wavelength. Considering all wavelengths, each object has a specific spectral signature and the analyse of their particular spectrum allows the deduction of their composition ( e.g. pigments) or health.
Ocean colour can be made visible in atmospherically corrected EO data. Specific spectral bands are necessary to derive physical and biologic parameters of the water from the EO data.