Citation:

Schaeffer, B., P. Whitman, R. Vandermeulen, C. Hu, A. Mannino, J. Salisbury, B. Efremova, R. Conmy, M. Coffer, W. Salls, H. Ferriby, AND N. Reynolds. Assessing potential of the Geostationary Littoral Imaging and Monitoring Radiometer (GLIMR) for water quality monitoring across the coastal United States. MARINE POLLUTION BULLETIN. Elsevier Science Ltd, New York, NY, 196:115558, (2023). https://doi.org/10.1016/j.marpolbul.2023.115558

Impact/Purpose:

This study details the technical specifications of the Geostationary Littoral Imaging and Monitoring Radiometer (GLIMR) , the United States’ first geostationary satellite for ocean color observations, and provides a framework for potential applications regarding water quality characterization and oil film monitoring following its launch later this decade. The spatial, temporal, and radiometric resolutions of GLIMR were evaluated and compared to currently operating satellites. GLIMR offers its best pixel resolution of 300 m directly below the satellite, and median 330 m spatial resolution across the Gulf of Mexico. GLIMR’s spatial resolution is at the coarser end of the distribution of current satellite platforms commonly used for water quality measurements, but is still within the range necessary for differentiating binary oil detect and non-detect. Meanwhile, temporal resolution is unmatched compared to polar orbiting sensors, with possible revisits up to six times per day and planned twice daily acquisitions of the coastal CONUS, among other regions. Radiometric resolution was assessed at the default scan time as well as at alternate scan times for replication of potential use cases.

Description:

The Geostationary Littoral Imaging and Monitoring Radiometer (GLIMR) will provide unique high temporal frequency observations of the United States coastal waters to quantify processes that vary on short temporal and spatial scales. The frequency and coverage of observations from geostationary orbit will improve quantification and reduce uncertainty in tracking water quality events such as harmful algal blooms and oil spills. This study looks at the potential for GLIMR to complement existing satellite platforms from its unique geostationary viewpoint for water quality and oil spill monitoring with a focus on temporal and spatial resolution aspects. Water quality measures derived from satellite imagery, such as harmful algal blooms, thick oil, and oil emulsions are observable with glint <0.005 sr−1, while oil films require glint >10−5 sr−1. Daily imaging hours range from 6 to 12 h for water quality measures, and 0 to 6 h for oil film applications throughout the year as defined by sun glint strength. Spatial pixel resolution is 300 m at nadir and median pixel resolution was 391 m across the entire field of regard, with higher spatial resolution across all spectral bands in the Gulf of Mexico than existing satellites, such as MODIS and VIIRS, used for oil spill surveillance reports. The potential for beneficial glint use in oil film detection and quality flagging for other water quality parameters was greatest at lower latitudes and changed location throughout the day from the West and East Coasts of the United States. GLIMR scan times can change from the planned ocean color default of 0.763 s depending on the signal-to-noise ratio application requirement and can match existing and future satellite mission regions of interest to leverage multi-mission observations.

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