AQUAVis: Landsat-sentinel virtual constellation of remote sensing reflectance (Rrs) product for coastal and inland waters

Operational Land Imager (OLI) onboard Landsat-8 and -9 (L89) and the MultiSpectral Instrument (MSI) onboard Sentinel-2A and -2B (S2A-B), as well as the recently launched Sentinel-2C, have been increasingly used for inland and coastal water monitoring. Integrating both data sensors into a single virtual constellation presents opportunities to enhance the revisit rate and capture the temporal variability of optically active water constituents. Since the NASA Harmonized Landsat-Sentinel-2 product is primarily focused on land applications, a new water-focused framework is needed for consistent integration of both OLI and MSI Remote Sensing Reflectance ( R r s ) products for aquatic studies. This study proposes a new globally validated framework, called AQUAVis (Aquatic Virtual Constellation for Landsat-Sentinel R r s Observations), designed to generate a harmonized L89-S2A/B dataset for aquatic applications. The AQUAVis workflow includes atmospheric, adjacency effect, and sunglint corrections, as well as spectral bandpass adjustment derived from a global dataset of more than 4000 water bodies to ensure seamless R r s integration. We acquired a total of 3568 L89 and 2986 S2A/B images (6.6 TB) between 2015 and 2023, and AQUAVis R r s retrievals were assessed using 2664 matchup observations with the AErosol RObotic NETwork-Ocean Color across 23 sites worldwide. Results demonstrated high agreement between AQUAVis-derived and in situ R r s retrievals, with spectral differences ranging from 0.39 % in the blue band to 21 % in the near-infrared band. The AQUAVis R r s product was further assessed for Chlorophyll-a estimation using the XGBoost model, which showed high spatial agreement between AQUAVis OLI and MSI matchup results in a wide range of Chl-a concentrations. These findings highlight the potential of AQUAVis to provide consistent R r s products for large-scale water quality monitoring. By facilitating global aquatic data integration, AQUAVis supports applications in aquatic remote sensing, contributing to a broader understanding of water quality dynamics and trends. • AQUAVis harmonizes Landsat-8/9 and Sentinel-2 reflectance (Rrs) for inland and coastal waters. • Workflow applies vicarious calibration, atmospheric, adjacency, sunglint corrections and sensor bandpass adjustments. • Validated with 2,664 AERONET-OC matchups, showing strong spectral agreement across sensors. • XGBoost chlorophyll-a retrievals confirm consistent OLI and MSI Rrs across trophic ranges. • AQUAVis enables scalable, reliable global water quality monitoring from multi-source satellites.