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Sentinel-4/UVN is a high resolution UVN (UV-VIS-NIR) spectrometer system, being developed within the framework of the Copernicus programme, to support operational monitoring of air quality and climate over Europe and adjacent regions, through accurate atmospheric measurements of trace gas concentrations and aerosols. Stray light is one of the main drivers of the instrument performance. We have developed a stray light correction analysis framework, applicable to a wide range of spectrometer systems, to provide input for selecting the right correction method(s) and specifying calibration measurements, well before the on-ground calibration campaign. This was accomplished by using the instrument design parameters and simulated instrument response to evaluate the S4-UVN stray light performance, before and after stray light correction.
This paper presents the developed framework and a stray light correction sensitivity analysis performed for Sentinel-4/UVN. The analysis results indicate that an iterative convolution correction algorithm can reduce stray light levels in case of smooth stray light, such as diffraction and scattering. The observed fast convergence of the algorithm suggests that a single iteration may suffice in many cases. The study shows that calibration uncertainties should be carefully considered during the preparation for the on-ground calibration campaign, as they can significantly degrade the correction quality.
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