, , , , Giuseppe Zibordi
The global Aerosol Robotic Network for Ocean Color (AERONET-OC) program utilizes AERONET CE-318 sun photometers (termed SeaPRISMs) modified for in-air observations of ocean waters situated on oil drilling rigs, off-shore lighthouses, or other platforms that meet the AERONET‑OC site requirements. The measurements provide quantification of the water-leaving radiance and are a source of validation data for ocean color satellite sensors. Accurate, validated retrievals at these sites, which present both spatially and temporally complex waters and atmospheres, aid in many aspects of the ocean color problem. In this study, we characterized and calibrated one instrument from the AERONET‑OC network SeaPRISM080 using the NIST Spectral Irradiance and Radiance responsivity Calibrations using Uniform Sources (SIRCUS) facility. A laser-illuminated integrating sphere of known radiance mapped out the absolute radiance responsivity for 7 bands. We validated these results using NIST calibrated lamp-illuminated integrating spheres. Finally, we compared the results to calibrations from the AERONET facility at NASA/GSFC and the Joint Research Centre (JRC) of the European Commission. The results agree within the estimated uncertainties. Along the way, we determined that a specific interpretation to the way the SeaPRISM080 processed data internally was required in order to correctly interpret results acquired using the RS232 interface protocol, which was necessary on SIRCUS. We demonstrated this was a valid interpretation by comparing this NIST custom data acquisition procedure to a firmware version in the SeaPRISM080 control unit.
Ocean Color, AERNET-OC, Calibration, Radiometry