Potential Referenced Sources for System Vicarious Calibration Applied to Ocean Color Satellite Sensors: Marine Pseudo-Invariant Sites

System vicarious calibration (SVC) is essential for achieving high-precision ocean color products from satellite sensors, traditionally relying on in situ measurements from stable calibration sites. However, data constraints due to environmental factors have prompted the exploration of marine pseudo-invariant sites (MPISs) as supplementary SVC sources. This study investigates the feasibility of MPIS for SVC by analyzing long-term Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua data to identify oceanic regions with stable optical properties suitable for calibration. Four MPISs were identified, and time-series models of remote sensing reflectance ( $R_{\mathrm {rs}}$ ) were constructed, demonstrating consistent variability patterns that support their suitability for SVC. These models were then applied to calculate SVC coefficients for Visible Infrared Imaging Radiometer Suite (VIIRS)-suomi national polar-orbiting partnership (SNPP) and were validated against in situ measurements from the Marine Optical Buoy (MOBY) site. Results indicate that MPIS-derived SVC coefficients show less than 1.68% discrepancy across visible (VIS) wavelengths compared to MOBY, enhancing SVC stability and reducing calibration timeframes. Additionally, the comparison between VIIRS-derived remote sensing reflectance, before and after applying the MPIS-based SVC coefficients, and in situ data further verifies the accuracy of the calibration coefficients. This study underscores MPIS’s potential to supplement traditional SVC methods, improving calibration coverage and enabling continuity in ocean color remote sensing missions.