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| Hauptseite > Publikationsdatenbank > AirFloX: Bridging Scales for SIF Calibration and Validation in Support of FLEX |
| Hauptseite > Publikationsdatenbank > AirFloX: Bridging Scales for SIF Calibration and Validation in Support of FLEX |
| Conference Presentation (Other) | FZJ-2025-04456 |
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2025
Abstract: The upcoming FLuorescence EXplorer (FLEX) mission of the European Space Agency (ESA) will provide global, high-resolution maps of sun-induced chlorophyll fluorescence (SIF), enhancing the monitoring of photosynthetic activity. Accurate calibration and validation (Cal/Val) of FLEX products through independent in-situ measurements is essential to ensure reliable SIF estimates. While tower-based systems offer unattended, continuous measurements, they are not suitable for spatially heterogeneous landscapes. Airborne systems offer broad spatial coverage and capture spatial heterogeneity, but they are costly and have limited temporal resolution. Unmanned aerial systems (UAS) are a lower-cost alternative, with the potential to bridge the spatial and temporal gap between ground-based and satellite observations. In this context, we present AirFloX: a novel, modular, spectroscopy system deployable on UAS or helicopters capable of measuring SIF and high-resolution reflectance. AirFloX is a non-imaging spectroscopy system consisting of two point spectrometers (Ocean Insight, USA) connected to bifurcated fibre optics switching between the downwelling irradiance and upwelling radiance. The two spectrometers complement each other having different spectral range and resolution for measuring both SIF and reflectance. The 4 kg payload can be mounted on commercial UAS platforms, and a dedicated graphical user interface allows to customize the acquisition. AirFloX was extensively tested during two ESA-funded field campaigns in May and June 2025 in agricultural and forested areas in Tuscany, Italy. The campaigns aimed to evaluate different strategies for the validation of the SIF products of the upcoming FLEX mission. To this end, we implemented sampling schemes based on optimisation methods designed to find the optimal locations of the sampling points maximising their spatial representativeness. Multi-scale SIF measurements were collected using ground-based systems (FloX) and airborne systems (AirFloX) mounted on two UAS and a helicopter (HELiPOD system), enabling to cross-compare the results at different scales. In this contribution we present the first results of these campaigns, discuss associated challenges, and outline implications for the Cal/Val of SIF satellite products.
Keyword(s): Earth, Environment and Cultural Heritage (1st)
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