Simulation Analysis and Retrieval of Venusian Lower Atmosphere Based on Microwave Sounding

This article investigates the potential of microwave sounders for a future international Venusian lower atmosphere exploration mission. Venusian microwave atmospheric radiative transfer (RT) calculations from a spaceborne perspective are performed with appropriate settings of the specific observation geometry and input atmospheric scenarios. An atmospheric profile perturbation analysis was undertaken to determine the channel selection and corresponding retrieval accuracy. Meanwhile, a suitable configuration of microwave sounder is proposed based on the gas absorption characteristics, sensitivity, and retrieval error analysis. The channel frequency selected includes 21 (2) channels of SO2 (H2SO4) absorption lines and its sidebands, as well as 37 channels between 6 and 42 GHz. Due to the strong coupling between temperature, SO2, and H2SO4 in the lower atmosphere, a joint physical retrieval method [optimal estimation method (OEM)] is proposed. Under ideal model conditions, the RMSE of retrieved temperature profiles improves by 1.3 K to stay within 2 K for 0–65 km, while the maximum RMSEs for SO2 and H2SO4 volume mixing ratios (VMRs) show improvements of at least 15% and 10%, reaching 30% and 25%, respectively. These results validate the proposed microwave sounder’s effectiveness for temperature and SO2 (H2SO4) profiling up to 65 km (30–75 km for SO2 and 35–55 km for H2SO4). However, increasing model error reduces retrieval accuracy, emphasizing the importance of model development for accurate joint observations of these parameters.