Calibration of an imaging system for monitoring light pollution from small UAVs

The paper presents the calibration activity of the imaging system of an autonomous sensor suite designed for monitoring light pollution Which, thanks to its extremely compact design, can be carried by drones or small balloons. Drones and air balloons can in fact play an important role in completing light emission measurement from satellites, allowing an increased spatial and time resolution from convenient altitudes and positions. The proposed sensor suite is able to measure the luminous intensity of polluting sources and their spectral power density with a wavelength resolution which allows to identify the different lamp echnology used in street lighting. By operating over a limited area, the spatial resolution can be about tenths of meter and the time evolution of the luminosity can be measured over hours. The expected performance of imaging system has been verified through an extensive laboratory test activity allowing calibration with referenced light sources. The calibration of the multi-luminance meter allows measurements with a base uncertainty of about 5% of the reading. The multi-spectrometer has a FWHM equal to 10 nm and is able to measure the power density of the outdoor light source in the range between 400 nm and 700 nm.