First Comparison of the Solar and an SI Radiometric Scale

Abstract

The paper presents the results of the first comparison between the solar radiometric scale, the World Radiometric Reference (WRR) and a Système International radiometric scale (SI scale) as disseminated by national standards laboratories, in particular, the scale based on the cryogenic radiometer of the National Physical Laboratory (NPL). The comparison used a number of transfer standards to act as intermediaries between the two scales which limited the overall uncertainty to 0,07%. The final result shows that the WARR and the NPL SI scale agree to better than 0,03%, well within the absolute uncertainty of the two scales.