Characterisation of an LED-based integrating sphere source for detection of changes of AERONET Europe radiometers

Abstract Within the framework of the EMPIR project 19ENV04 MAPP “Metrology for aerosol optical properties” an LED-based source was built for monitoring responsivity changes of Cimel filter radiometers from the AERONET Europe network. The developed LED device was flanged to integrating spheres to fill the field of view of the radiometers. Here we present the characterisation results of the LED-based integrating sphere source. The spectra of the radiant flux leaving a BaSO 4 -based integrating sphere showed positive wavelength dependent drift, which had not been reported in literature yet and did not appear by using incandescent lamps with the integrating spheres. This report shows approaches to reduce such drifts and an alternative using a PTFE-based integrating sphere, which was also tested for stability, reproducibility and homogeneity.