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Hyperspectral Imaging has been accepted for ocean color measurements from both airborne platforms and space-based instruments but has yet to be implemented with the desired ground resolution, coverage, revisit rate, and Signal to Noise Ratio (SNR) for coastal observations of biological processes. The low albedo and high levels of atmospheric scattering drives the need for 1000:1 SNR ocean color data, while harmful algal blooms or post-extreme weather events require daily revisit rates. To achieve higher SNR, Low-Earth Orbit (LEO) sensors must make the trade-off of aperture size and spatial resolution versus spacecraft size and complexity. Airborne missions can achieve the high SNR and spatial resolution needed but lack in coverage and revisit rates. Recent flights of the NASA ER-2 and stratospheric solar planes have suggested an opportunity for regional coastal hyperspectral imaging with multi-week observations, rapid revisit times, and low frame rates for high SNR. Stratospheric platforms, also known as High-Altitude Pseudo Satellites (HAPS), can fill this gap but have limited payload size, weight, and power (SWaP.) We present an example payload that fits within these limitations, the Compact Hyperspectral Advanced Imager (CHAI) for ocean color measurements. A solar plane HAPS UAV platform with a CHAI payload is compared against the baseline NASA HySPIRI LEO mission and the NASA AVIRIS-NG airborne system. Hyperspectral imaging is only one of the technologies needed for better understanding of the coastal environment. Other low SWaP coastal imaging payloads are discussed for applications including Solar Induced Fluorescence (SIF), Evapotranspiration (ET), and Methane Gas Imaging. For Earth Science applications such as coastal remote sensing, a HAPS platform with a suite of small sensors may be the optimal system for regional studies.
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