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@INPROCEEDINGS{Tagliabue:1047681,
      author       = {Tagliabue, Giulia and Rossini, Micol and Garzonio, Roberto
                      and Julitta, Tommaso and Burkart, Andreas and Bendig,
                      Juliane and Rascher, Uwe and Siegmann, Bastian and Cogliati,
                      Sergio and Chierichetti, Pietro and Vignali, Luigi and
                      Panigada, Cinzia and Pätzold, Falk and Lampert, Astrid and
                      Tudoroiu, Marin and Colombo, Roberto},
      title        = {{A}ir{F}lo{X}: {B}ridging {S}cales for {SIF} {C}alibration
                      and {V}alidation in {S}upport of {FLEX}},
      reportid     = {FZJ-2025-04456},
      year         = {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.},
      month         = {Dec},
      date          = {2025-12-15},
      organization  = {American Geosciences Union, New
                       Orleans (USA), 15 Dec 2025 - 19 Dec
                       2025},
      subtyp        = {Other},
      cin          = {IBG-2},
      cid          = {I:(DE-Juel1)IBG-2-20101118},
      pnm          = {2173 - Agro-biogeosystems: controls, feedbacks and impact
                      (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2173},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/1047681},
}