Comparison to the conventional primary standard, the WRR, defined by the World Standard Group; the three NMIs NPL, PMOD/WRC and METAS are participating with a common instrument CSAR (Cryogenic Solar Absolute Radiometer).
Comparison done as part of the International Pyrheliometer Comparisons XII (IPC-XII), which is a WMO comparison.
Final Report 2019-09-23
The comparison has been completed and results are published in the KCDB.
Progress Report 2016-01-21
Measurements finished as planned, report in progress.