POSTER Session 4

UNCERTAINTY BUDGET FOR SEA-BIRD SCIENTIFIC RADIOMETERS FOLLOWING CROSS-SITE CALIBRATION

In-situ and above water radiometers are critical for validating ocean color (OC) satellite measurements used to monitor in-water constituents of the global ocean. The calibration process, instrument response characterization, and environmental measurement effects all contribute to the overall uncertainty budget of the radiometric measurement. An integral part of this uncertainty traceability chain is accurate, NIST-traceable laboratory calibration of radiometric sensors used to validate OC products. In 2023, Sea-Bird Scientific transitioned the manufacturing of radiometric products from the Philomath, Oregon (WET Labs) facility to the Bellevue, Washington (Sea-Bird Electronics) facility. As part of this transition, the radiometer calibration facility was reproduced at the Bellevue site. To maintain accuracy, Sea-Bird Scientific conducted an extensive cross-facility set of round robin experiments to quantify uncertainties between our laboratories. At each site, four independent calibrations were performed with a secondary source (NIST-traceable FEL lamp and reflectance plaque) for a set of 10 internal sensors as well as 27 production radiometers covering radiance and irradiance variants of our hyperspectral (HOCR) and multispectral (OCR) radiometers. Relative percent differences in calibration scale factors between the two sites were kept within ±0.5% for reference radiometers. Repeatability (k=2) of calibrations was within ±0.8% (hyperspectral) and ±0.4% (multispectral). An overall uncertainty budget was comprehensively characterized by eight components consistent with the FRM4SOC FidRadDB database demonstrates that radiometric calibration uncertainty (k=2) was maintained at 3-4% or improved as part of the transition to the new facility. NIST-traceable uncertainties in FEL lamp irradiance and radiance plaque reflectance were the largest contributors.

Eric Rehm, Sea-Bird Scientific, USA, [email protected], https://orcid.org/0000-0002-8417-538X

Michael Dewey, Sea-Bird Scientific, USA, [email protected]

Ryan Lamb, Sea-Bird Scientific, USA, [email protected]

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