Diurnal Remote Sensing of Coastal/Oceanic Waters: a Radiometric Analysis for Geostationary Coastal and Air Pollution Events

Optical remote sensing systems aboard geostationary platforms can provide high-frequency observations of bio-optical properties in dynamical coastal/oceanic waters. From the end-user standpoint, it is recognized that the fidelity of daily science products relies heavily on the radiometric sensitivity/performance of the imaging system. This study aims to determine the theoretical detection limits for bio-optical properties observed diurnally from a geostationary orbit. The analysis is based upon coupled radiative transfer simulations and the minimum radiometric requirements defined for the GEOstationary Coastal and Air Pollution Events (GEO-CAPE) mission. The diurnal detection limits are found for the optically active constituents of water, including near-surface concentrations of chlorophyll-a (CHL) and total suspended solids (TSS), and the absorption of colored dissolved organic matter (aCDOM \u3e��CDOMaCDOM ). The diurnal top-of-atmosphere radiance (Lt \u3e����Lt ) is modeled for several locations across the field of regard (FOR) to investigate the radiometric sensitivity at different imaging geometries. It is found that, in oceanic waters (CHL=0.07 mg/m3 \u3eCHL=0.07 mg/m3CHL=0.07 mg/m3 ), detecting changes smaller than 0.01 mg/m3 \u3e0.01 mg/m30.01 mg/m3 in CHL is feasible for all locations and hours except for late afternoon observations on the edge of the FOR. For more trophic/turbid waters (0.60.60.1 mg/m30.1 mg/m3 when the air mass fraction (AMF) is less than 5. For aCDOM(440) \u3e��CDOM(440)aCDOM(440) , detecting the changes larger than 0.02 m−1 \u3e0.02 m−10.02 m−1 (0.080.08\u3c��CDOM(440)\u3c0.360.08 ) is found feasible for most of the imaging geometries. This is equivalent to AMF\u3c5 \u3eAMF\u3c5AMF\u3c5 . For TSS, changes on the order of ΔTSS=0.1 g/m3 \u3eΔTSS=0.1 g/m3ΔTSS=0.1 g/m3 (0.50.