Comparison of Hyperspectral Models for Synergies among Sensors in the CHIME Mission Implementation for Operational Downstreaming Services

CHIME is the Copernicus Hyperspectral Imaging Mission for Environment, a candidate to be added to the Copernicus Sentinel fleet. Within the requirements consolidation study (ESA funded ITT), the value added by hyperspectral data for biophysical variables retrieval is explored in two application domains, namely Agriculture/Food Security and Raw Materials. Currently, there are concerns about the spectral dimensionality of hyperspectral data in different band configurations, the similarity of spectral feature spaces, the variability of hyperspectral signatures, and how sub-pixel analysis capture this variability. Our analyses consider different hyperspectral (AVIRIS-NG CHIME-like and PRISMA) and multispectral data (Sentinel 2). The methodology used is based on unmixing models, namely the Linear Spectral Mixture Analysis (LSMA) and the Multiple Endmember Spectral Mixture Analysis (MESMA), to improve the knowledge on the hyperspectral variability. The land cover products, namely soil organic content and texture, main crop typologies (e.g., rice, alfalfa, maize), and mineral identification, are discussed on the basis of their geospatial pattern distribution when using different sensors and different biophysical parameters retrieval models. The results show the importance of SWIR sensors in the new generation of hyperspectral missions. The unique value offered by hyperspectral data is building a wide arbitrary spectral library. PRISMA extends its nominal spatial resolution of 30 meters to 5 meters thanks to the panchromatic band. The decreased revisit time of multispectral imaging like Sentinel 2 offers the potential for data fusion to leverage the spectral resolution of hyperspectral sensors and the temporal resolution of multispectral constellations. Statistical analyses show that new sensors, complex spectral mixture models and field data shall improve the reliability of the existing and upcoming land cover products.