Organised annually by the European Solar Test Installation (ESTI) laboratories of the Joint Research Centre (JRC), the event consists of a week of uninterrupted measurements of solar radiation performed by participating instruments to be assessed against reference instruments.

More specifically, the exercise assesses the amount of broadband solar irradiance (direct and global normal) and spectrally resolved spectral irradiance (direct and global normal) measured by broadband sensors and spectroradiometers. For the former, the conversion factors will be provided, using as a reference the set of ESTI’s absolute cavity radiometers directly traceable to the World Radiometric Reference (WRR) via IPC-XIII held in Davos (CH); for the latter, several performance statistics indicators will be calculated, with focus on the relative spectral content in different spectral bands. The results will be published by the JRC in an official report. Several other prototypes and custom sensors are also eligible for participation and the report foresees a dedicated section for these instruments if they are not directly comparable with reference instruments.

Launched in 2011, the first ISRC edition focused primarily on photovoltaic (PV) research and application. Over the years, the range of interested participants has gradually differentiated encompassing not only laboratories in the PV field, but also space agencies, national metrological institutes (NMI), universities, research groups and manufacturers of measurement equipment operating in the fields of climatology and meteorology.