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Water insight spectrometer with three radiometers
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The water insight spectrometer with three radiometers (WISP-3) is a hand-held radiometer which automatically operates measurements with 3 radiometers simultaneously (Lsky, Lu, Ed) for water quality monitoring. It derives the colour of the water, for water quality monitoring. WISP-3 directly derives values of water quality parameters (Chl, SPM, phycocyanin and Transparency) by the use of standard algorithms: * Chl-a: Chlorophyll-a (0-120 µg l ). * SPM: suspended particulate matter (0-100 mg l ). * Phycocyanin concentration (0-1200 mg m ). * Transparency (kd m ). The absorption by colored dissolved organic matter (aCDOM) water quality parameter is also indirectly derived by WISP-3. In this case, more advanced algorithms are used which need the use of computers. Technical description The WISP-3 device is composed by three Ocean Optics, Inc. JAZ radiometers, a portable computer and a battery. One of the radiometers is connected through optical fibers to a cosine corrector to measure the downwelling irradiance [Ed (λ)]. The other two radiometers are connected to two Gershun tubes in order to measure the downwelling radiance from the sky [ Lsky (λ, θ)] in which θ=42 deg from the zenith and the total upwelling radiance [Lu (λ,θ)] at 42 deg from the nadir (θ138 deg). The three radiometers and the mentioned angles are chosen conforming to Mobley's guidance. Function Optical close range devices and satellites measure the light that is reflected from the water bodies. In order to derive water quality parameters ( Chl-a, SPM, aCDOM and Secchi depth) from these measurements, algorithms are used. The WISP-3 spectro-radiometer measures three optical signals that allow deriving reflectance values from the water surface. Using adapted band ratio algorithms determined by the water type where the measurements are taken, real time concentration of Chl-a, phycocyanin, SPM and Transparency are computed. It also has been used for monitoring activities of Blue-green algae in the IJsselmeer, in the Netherlands.<ref name="Chawira"/> 
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