Absolute calibration of the Colour and Stereo Surface Imaging System (CaSSIS)

The Colour and Stereo Surface Imaging System (CaSSIS) onboard the ExoMars Trace Gas Orbiter (TGO) has observed several standard stars Jupiter with aim of deriving absolute calibration factors that convert signal into reflectance (”I over F”). targets were through all four colour filters hence a relative between was possible. In addition, observations Phobos acquired during TGO capture orbits in 2016 analysed support calibration. results show CaSSIS around 13% less sensitive than predicted (normalised to RED filter) - value is larger formal uncertainty therefore significant. shows be 4% more BLU modelled which close uncertainty. text describes analysis approach methods for various newly recommended conversion are provided table form.