Martian Atmosphere Study Using THz Limb Sounder

Mars is one of the main targets of deep space exploration. Continuous and high spatial resolution global monitoring of Martian atmosphere is an important way to understand the aeronomy and meteorology of Mars. The atmospheric wind and chemical species in the photochemical cycle such as CO, O3, H2O, and H2O2 can be measured in large scale by Terahertz limb sounding technique to improve our understanding of Martian atmospheric chemistry and dynamics. The spectrum in the frequency region of 300∼1000GHz is analyzed according to the request of Mars exploration. Considering the requirements of the satellite on the parameters of load weight and power, a Martian atmosphere THz limb sounder working in the frequency of 547∼579GHz is proposed. The planetary toolbox of ARTS (Atmospheric Radiative Transfer Simulator) is used to simulate the performance of the instrument. Results show that by using CO lines to retrieve the temperature profile, the total precision can be <4K. The precision is <2K at an altitude below 45km. The retrieval precision of H2O is <50% at an altitude below 50km, and the best precision is 2% below 30km. The retrieval precision of H2O2 is <50% below 40km. The retrieval precision of O3 is <60% below 50km. The retrieval precision of the atmospheric line of sight wind is <5m·s−1 above 65km, and the best precision is 2m·s−1. In conclusion, the middle and upper atmospheric wind and the abundance of the chemical species can be well measured by using THz limb sounding technique.