7.4 European Uv Broad Band Filter Radiometer Reference Scale

The pertinent lack of a standard calibration procedure for UV filter radiometers introduces unknown and potentially large uncertainties in their measurement products. Although most UV calibration facilities take into account many instrument properties that affect the measurement quality of UV filter radiometers, some instrument characteristics that are difficult to determine present substantial problems, which limit the measurement quality during long term use of the instruments. At the Joint Research Centre (JRC) of the European Commission a UV broad band filter radiometer reference group is under development which is intended to maintain an accurate UV irradiance scale for instruments used in UV filter radiometer networks throughout Europe. The reference group is intended to be composed of instruments from institutions who may benefit from a uniform and well maintained UV irradiance scale that will be traceable to the high class UV spectroradiometer standard established at the European Reference Centre for Ultraviolet Radiation Measurements (ECUV) at the JRC. From July 2003 on, several UV filter radiometers have been operating routinely next to the UV spectroradiometer standard. All UV filter radiometers together will form part of the reference group, which will be calibrated according to a common procedure. A subset of 3 units in a component summation measurement configuration has been used for a closure study that allows to define a measurement accuracy for UV filter radiometers. The presentation 7.4 gives an introduction to the proposed European UV broad band filter radiometer reference SCALE (EUVSCALE) project, shows first results obtained from the measurements at ECUV, and contains a short discussion of recommendations for UV filter radiometer measurements.