The World Standard Group (WSG) of absolute cavity radiometers is maintained by the World Meteorological Organization's (WMO) World Radiation Center (WRC) (Davos, Switzerland). The WSG is a group of seven well-characterized absolute cavity radiometers used to define the World Radiometric Reference (WRR). International intercomparisons of national standard pyrheliometers with the WSG are held every five years at the WRC to transfer the WRR to national centers. Having participated in such comparisons since 1980, NREL has three absolute cavity radiometers directly traceable to the WRR. The WRR has an uncertainty of less than +/- 0.3%. This means that the best possible measurements of direct normal solar irradiance have at least this uncertainty.

Web Service Group; responsible for the overall design and development of the McGill Web System and for certain principal sites

Web Services Gateway.