IMPROVED COMPARISON OF THE WORLD RADIOMETRIC REFERENCE AND THE SI RADIOMETRIC SCALE

A few years ago, we compared for the first time the World Radiometric Reference, which is used as reference for meteorological radiometry, a nd the Systeme International (SI) radiometric scale realized at the Na tional Physical Laboratory with cryogenic radiometers. We present an i mproved comparison which used as transfer standard a trap detector cal ibrated to the NPL primary standard cryogenic radiometer. As a realiza tion of the World Radiometric Reference, we used an electrical substit ution radiometer traceable to the WRR and used in solar radiometry. Th e method of transfer has been improved and the results confirm those o f the first comparison but with much lower uncertainty.