Refining a Hyperspectral and Multi-Angle Measurement Concept for Vegetation Structure Assessment

The concept of combining multi-angle and hyperspectral remote sensing has been developed and utilized in an existing satellite observation system CHRIS (Compact High-Resolution Imaging Spectrometer) onboard the Project for On-Board Autonomy (PROBA) platform developed by the European Space Agency (ESA). We attempt to refine this measurement concept by testing a new one: a system that acquires hyperspectral signals only in the nadir direction but measures in two additional directions in two spectral bands, red and NIR. Through model experiments, we demonstrate that the combination of the hotspot and darkspot reflectances has the strongest signals about the vegetation structure quantified using the foliage clumping index. The results suggest that the multi-angle hyperspectral data exhibit much redundancy, and that the multi-spectral measurements at off-nadir angles in addition to the nadir hyperspectral data would be sufficient to reconstruct hyperspectral signatures at off-nadir angles.