Measurement of dust optical depth using the solar irradiance sensor (SIS) onboard the ExoMars 2016 EDM

In addition to dust opacity measurements, this instrument is also capable to detect and characterize clouds by looking at the time variation of the color index (CI), defined as the ratio between the observations in NIR and UVA channels, during daytime or twilight. By simulating CI signals with a radiative transfer model, the cloud opacity and cloud altitude (only during twilight) can be retrieved. Here the different retrieval procedures that are used to analyze SIS measurements, as well as the results obtained in different sensitivity analysis, are presented and discussed.