Future SI standard for Solar Irradiance delivered to World Radiation Center

Scientists from NPL’s Earth Observation, Climate and Optical (ECO) group have recently installed the Cryogenic Solar Absolute Radiometer (CSAR) at the Physikalisch-Meteorologisches Observatorium Davos / World Radiation Center (PMOD/WRC) in Switzerland. CSAR was developed in close collaboration with PMOD/WRC and METAS (NMI Switzerland).

As a cryogenic radiometer, CSAR provides a direct link to the International System of Units (SI), and offers a much-reduced measurement uncertainty compared to the current standard.

During the WMO International Pyrheliometer Comparison (IPC XII) CSAR was measuring Solar Irradiance alongside the existing World Standard Group (WSG) which currently provides the worldwide radiometric reference scale for Solar Irradiance measurements.