The Venus InfraRed Atmospheric gases Linker instrument concept on-board the Venus Orbiter Mission of the Indian Space Research Organization
Résumé
In 2019, the Indian Space Research Organisation (ISRO) opened an Announcement of Opportunity to the international science community to study Venus for space-based experiments onboard planned ISRO's Venus Orbiter Mission. The joint proposal of Space Research Institute (Russia) and Laboratoire Atmosphères, Observations Spatiales, UVSQ Université Paris-Saclay (France) was chosen by the ISRO mission program committee. The VIRAL (Venus InfraRed Atmospheric gases Linker) project is aimed at proposing a remote sensing infrared (IR) spectrometer to provide first-class information on the composition and structure of the atmosphere at the top and above the cloud layer of Venus. VIRAL leverages from the legacy of a generation of spectrometers that has achieved very high detecting performances in a compact, light-weight, and easily-to-design. VIRAL will cover the IR range from 2.3 to 4.3 μm that will allow the retrieval of the layering of the Venusian upper atmosphere and its composition. The list of measured species includes CO2 and its main isotopes (with related retrievals of the atmospheric temperature), H2O and HDO (related to the evolution of water on Venus), CO, SO2, HCl, HF, H2SO4 droplets and aerosols. Its enhanced sensitivity will allow establishing refined upper limits or new detections for a number of trace gasses, such as OCS, H2S, H2CO, C2H2. An exclusive science goal is to trace phosphine, recently announced in Venus atmosphere. The concept, design and expected performance will be reported.