An Imaging Spectrometer Tailored to Water Quality and Aquatic Ecosystem Monitoring from Space: The AquaSat-1 Concept

We present a description of the AquaSat-1 mission concept, with emphasis on the instrument and concept of operations. AquaSat-1 seeks to provide data that can be used to deliver actionable information on water quality and aquatic ecosystems. The instrument is a state-of-the-art 350–1050 nm imaging spectrometer, with ≤10 nm Full-Width at Half Maximum (FWHM) spectral response function. It utilizes a fast f/1.8 optical system comprised of a three-mirror telescope coupled with a Dyson-type spectrometer. The passively cooled detector is a 3072x512-pixel Teledyne digital-output array with 18 μm pitch. Analysis of the radiometric performance demonstrates that the instrument can provide the required signal-to-noise ratio with margin for challenging aquatic objectives. High optical throughput and ground motion compensation, along with high spectral and spatial uniformity, permit high signal-to-noise ratio and excellent spectral-radiometric fidelity. The orbit is 400 km sun-synchronous with Local Time of Ascending Node (LTAN) 00:00. During its 1-year mission, AquaSat-1 will observe inland rivers, reservoirs, lakes, as well as corals in coastal areas.