Evaluation of the Spatial Representativeness of In Situ SIF Observations for the Validation of Medium-Resolution Satellite SIF Products

The upcoming Fluorescence Explorer (FLEX) mission will provide sun-induced fluorescence (SIF) products at unprecedented spatial resolution. Thus, accurate calibration and validation (cal/val) of these are key to guarantee robust SIF estimates for the assessment quantification photosynthetic processes. In this study, we address one specific component uncertainty budget related retrieval: representativeness in situ observations compared medium-resolution (e.g., 300 m pixel size). Here, propose an approach evaluate optimal sampling strategy characterise based on high-spatial-resolution data. This was applied demonstration purposes two agricultural areas that have been extensively characterized with a HyPlant airborne imaging spectrometer recent years. First, determined increasing number points respect reference area (either monocultural crop fields or hypothetical FLEX pixels characterised by different land cover types). Then, approaches determine which provided most representative data given area. Results show between 3 13.5 needed average value both considered study. tends increase standard deviation area, as well classes pixel, even if is not always statistically significant. study contributes guiding cal/val activities mission, providing useful insights selection site network particularly definition best scheme each site.