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Abstract

The interest of the scientific community on the remote observation of sun-induced
chlorophyll fluorescence (SIF) has increased in the recent years. In this context, hyperspectral
ground measurements play a crucial role in the calibration and validation of future satellite
missions. For this reason, the European cooperation in science and technology (COST) Action
ES1309 OPTIMISE has compiled three papers on instrument characterization, measurement setups
and protocols, and retrieval methods (current paper). This study is divided in two sections; first, we
evaluated the uncertainties in SIF retrieval methods (e.g., Fraunhofer line depth (FLD) approaches
and spectral fitting method (SFM)) for a combination of off-the-shelf commercial spectrometers.
Secondly, we evaluated how an erroneous implementation of the retrieval methods increases the uncertainty in the estimated SIF values. Results show that the SFM approach applied to highresolution
spectra provided the most reliable SIF retrieval with a relative error (RE) ≤6% and <5%
for F687 and F760, respectively. Furthermore, although the SFM was the least affected by an inaccurate
definition of the absorption spectral window (RE = 5%) and/or interpolation strategy (RE = 15%–
30%), we observed a sensitivity of the SIF retrieval for the simulated training data underlying the SFM model implementation.