Coastal Algal Bloom Monitoring Using Satellites and Ships of Opportunity-Operations and Data Analysis

Abstract

Traditional remote sensing strategies typically rely on single platforms, leading to constraints in data availability and validation. While integration of remote and in situ observational platforms allows for more frequent and detailed environmental monitoring, it also introduces complex challenges in agent-planning coordination and multi-source data fusion. This paper presents the operational implementation and multi-source data analysis framework for a cooperative small satellite constellation, utilizing hyperspectral satellite chlorophyll-a retrievals as a phytoplankton proxy for daily algal bloom monitoring. By coordinating the HYPSO CubeSat constellation with the Sentinel-3 mission and in situ FerryBox sensors, this study investigates active multi-platform integration using three complementary planning strategies: 1) an optimized task allocation between HYPSO-1 and HYPSO-2 to maximize spatial coverage while minimizing cloud contamination; 2) exploiting agile satellite pointing maneuvers to capture irregular coastal features along the Norwegian coastline, reducing revisit time; and 3) an automated pipeline ingesting real-time Automatic Identification System (AIS) data to dynamically trigger targeted images over active FerryBox vessels, enabling low-latency spatio-temporal match-ups between HYPSO and the FerryBox. Multi-source data are analyzed through pixel-wise cross-satellite correlation, ocean front detection, and outlier identification. HYPSO and Sentinel-3 chlorophyll-a cross-correlation yields match-ups with Pearson $r$ up to 0.745. Ocean front detection reveals how multi-source platforms can be used to extract information about ocean front dynamics, while multi-sensor redundancy supports the identification of potential outliers in chlorophyll-a estimation. The proposed framework is demonstrated in an algae bloom observational campaign, conducted in spring 2025 over Central Norway, centered on the Frohavet area.