Cross-Calibration of Polar-Orbiting Satellite Ocean-Color Sensors Using a Geostationary Reference Sensor

Long-term, global ocean-color observations are needed for biogeochemistry and climate applications and require integration across multiple satellite sensors. This study proposes a methodology for cross-calibrating polar-orbiting ocean-color sensors using a geostationary reference sensor. The geostationary sensor serves as an intermediary, offering numerous coincidences in time and geometry with polar-orbiting sensors, particularly over oceanic regions where radiance levels are typical for ocean-color remote sensing. The methodology is applied to cross-calibrate current ocean-color sensors, including the recently launched OCI, using AHI, a sensor expected to remain stable over short cross-calibration intervals. Accuracy is evaluated based on radiometric noise, acquisition time differences, solar and viewing geometry variations, and spectral band mismatch uncertainties. Cross-calibration coefficients derived from suitable imagery provide a foundation for consistent, normalized calibration of polar-orbiting sensors, enabling the generation of reliable long-term ocean-color products from multiple satellites.