Processing of ACS-NIR observations to build the solar spectrum with high spectral resolution in the 0.7-1.7 m domain

The ACS-NIR spectrometer on board the Trace Gas Orbiter is currently being used to probe the atmosphere of Mars. When ACS-NIR is pointed at the Sun, it detects the spectral signature of atmospheric components present on its line of sight (LOS) as it passes through the atmosphere. The solar spectrum is directly measured when the LOS is above the atmosphere. Special observations were therefore made to construct the solar spectrum in the 0.7-1.7 mu m domain. This is mainly useful for ACS-NIR calibrations and for other experiments. The observations consist in recording all the diffraction orders of ACS-NIR by continuously varying the frequency of its AOTF. Here we will present how to process this data to obtain the solar spectrum. We will first show how we get the flat field for image correction. Next, we will present how to overcome order contamination using a geometric method. We will then show how to correct the order intensity variations to obtain the solar spectrum. We will end by showing some results.