Spatial, spectral and nocturnal observation capabilities of a future satellite mission for coastal and inland aquatic ecosystems (GALENE)

Kurzfassung

Coastal and inland aquatic ecosystems are critically important to society, yet they remain among the least studied habitats because there are no satellites specifically designed to observe them at global scale. To address this gap, the GALENE mission concept (Global Assessment of Limnological, Estuarine and Neritic Ecosystems) is proposed to be submitted to future calls of European Space Agency. The mission concept comprises three innovative instruments. A hyperspectral imager covering the 380-1700 nm spectral range with 5-20 nm spectral and 30 m spatial resolutions is complemented with a panchromatic camera with 5 m spatial resolution capable of performing nighttime observations of turbid waters and with a polarimeter with 300 m spatial resolution. We demonstrate the relevance of GALENE’s combined spatial, spectral and nocturnal observational capabilities for synergistic use. The panchromatic camera can enhance spatial resolution while preserving hyperspectral information. We quantify this by applying a convolutional neural network-based fusion method on PRISMA hyperspectral data. We also study the value of GALENE’s 5 m panchromatic and 30 m hyperspectral bands by spatial and spectral resampling of very-high-resolution 8-bands WorldView satellite data. The feasibility of nighttime estimation of suspended matter concentration (SPM) is investigated by analyzing the sensitivity of satellite-measured radiances to SPM for a range of lunar phases and illumination geometries. Simulations of satellite-observed radiances are also analyzed to assess the radiometric (SNR) and spectral sensitivity of GALENE’s hyperspectral sensor for the detection and quantification of phytoplankton functional types and other coastal and inland water quality parameters.