Sun-induced fluorescence - a new tool for precision farming

Abstract

The objective of this paper is to present a new remote sensing technique that allows to monitor the sun induced chlorophyll fluorescence of green vegetation superimposed to the reflectance spectra. In contrast to the Fraunhofer Line Discriminator (McFarlane et. al. 1980) the new method uses the spectral absorption feature of atmospheric oxygen at 762nm which better fits to the wavelength of chlorophyll fluorescence than the Fraunhofer absorption line at 656nm. It will be shown how the sun induced chlorophyll fluorescence can be derived from reflectance spectra measured on ground and from aircraft. The new method can even be applied to medium spectral resolution imaging spectrometers like ROSIS, MOS and MERIS with a spectral resolution better than 5nm in the oxygen absorption band. In addition, it will be demonstrated that sun induced chlorophyll fluorescence is closely linked to photosynthesis and may thus be used in the future for areal observation of the photosynthetic status of plants. For a better understanding of sun induced fluorescence of plants the first leaf reflectance model is presented which includes chlorophyll fluorescence. Modeling results show the performance of the algorithm to determine sun induced fluorescence.