Fisalia research vessel sampling in the Tagus

Comparing radiometers in the Tagus

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15 November 2021

An extensive field work campaign in the Tagus estuary, Portugal took place in October 2021. 

Two sets of radiometers, one from the CERTO project and the other from the Alfred Wegener Institut were mounted on the Fisália research ship to obtain measurements of water quality that will be used to validate satellite observations.

Radiometers mounted on the Fisália following the Lisboat ferry. Photo: Federico IennaThe radiometers measure the reflectance of sunlight by water which gives us an insight into aspects of the water quality including plankton biomass, suspended solids and dissolved organic matter. These measurements are enhanced by the addition of a hyperspectral radiometer which measures the colour or spectral distribution of sunlight near the water’s surface. This is used to improve accuracy of other sensors by correcting for atmospheric effects.

An additional intercomparison transect was performed with the CERTO radiometers that are already installed on the Lisboat ferry, where the Fisalia took measurements alongside the ferry in order to calibrate the instruments.

These measurements will be essential for the CERTO project to help improve atmospheric correction of satellite imagery in optically complex transitional waters.