Millimeter‐Wave Radiometric Information Content Analysis for Venus Atmospheric Constituents

Abstract

AbstractVarious gaseous constituents present in Venus atmosphere have been detected and measured using in situ and remote sensing instruments. However, the measurements of mesospheric constituents above the cloud level are still scarce and inadequate. This is because constituents above the cloud level have a low abundance and a high level of variability. However, millimeter and submillimeter (mm and sub‐mm) frequencies can be used for Venus mesosphere measurements during prolonged Venusian day and night because several minor species in the upper atmosphere have emission/absorption bands in these frequencies owing to the rotational transitions. This study presents brightness temperatures and the corresponding sensitivity at the mm and sub‐mm wave frequencies for a limb sounding radiometer. This will be useful in potential payload design, that is, instrument design, frequency, bandwidth selection, and satellite altitude as well as pointing accuracy determination for measurement above Venus clouds. For this study, a simulation based experiment has been performed and presented to determine the mm and sub‐mm wave frequencies, optimum for estimation of concentration of water vapor, CO, CO2, SO2, HDO, and HCl present in the mesosphere. The simulations have been performed using a radiative transfer model called Atmospheric Radiative Transfer Simulator. The mm and sub‐mm wave measurement frequencies have been determined for both day and night time of Venus. It has been determined that 183, 380, 448, and 556 GHz frequencies are most suitable for water vapor measurements, 115, 230, and 345 GHz are optimum for CO measurements, and 600, 621, and 690 GHz frequency measurements are sensitive for HCl detection.