Mars clouds simulation for the optical depth sensor (ODS)
Résumé
A small and sophisticated optical depth sensor (ODS) has been selected in the payload of the atmospheric package DREAMS onboard the MARS 2016 mission. ODS was built to carry out the opacity due to the Martian dust and to characterize the high altitude clouds at twilight on Mars. Dust and clouds are primary elements for studying the interactions of solar radiation with the Mars atmosphere and surface and their influence on the radiation balance. In addition, dust lifted by storms are the unique condensation nuclei available at the Mars atmosphere. Therefore a capability of modeling the dust and clouds is vital for understanding of meteorology and climate on Mars. For the clouds detection, the index colour (CI) is used, defined as the ratio between the scattered light at red and blue wavelengths. If a cloud is present during twilight, then a peak must be observed in the CI. The opacity due to the Martian dust can be detected by comparing the sunlight scattered at zenith and direct sunlight. In order to retrieve the dust and cloud properties, a radiative transfer three- dimensional model in spherical geometry must be used. In this presentation, we will show the principle of the instrument, we will describe the procedure which is used in order to retrieve the dust and cloud physical properties and we will finally present some results of field campaigns made in terrestrial environment.