A fluorescence retrieval method for the flex sentinel-3 tandem mission

A new fluorescence retrieval method is proposed to support ESA's 8th Earth Explorer Fluorescence EXplorer (FLEX) candidate mission. Most hyperspectral fluorescence retrieval algorithms available in the literature are very sensitive to true reflectance modelization and/or they assume the atmospheric status as known. The proposed algorithm delivers the retrieval of full fluorescence spectrum at canopy level by using only Top Of Atmosphere (TOA) radiances as input. The proposed method starts with (1) the atmospheric correction of TOA radiances, characterizing the state of the atmosphere without assuming any a-priori classification on aerosols models, (2) performing a first estimation of fluorescence values in main oxygen absorption bands without any approximation of true reflectance spectrum, and (3) using this fluorescence estimation to initialize a Spectral Fitting Method (SFM) to finally retrieve a full fluorescence spectrum. All these aspects make the proposed fluorescence retrieval method robust and independent of external auxiliary data.