TEREX-1: A feasibility study of H2O, O2, O3, H2O2 up-looking observation in Martian atmosphere
Abstract
The TERa-hertz EXplorer (TEREX) is a series mission of micro Mars lander/orbitars carry a terahertz wave instrument. We are building a terahertz measurement system for the first lander mission, TEREX-1, which is capable to detect the molecular oxygen (O$ _{2}$), water vapor (H$ _{2}$O), ozone (O$ _{3}$), and hydrogen peroxide (H$ _{2}$O$ _{2}$) emission lines. The frequency windows are 474.64 to 475.64 and 486.64 to 487.64 GHz double-side-band with 100 kHz frequency resolution. We have developed a terahertz (THz) radiative transfer model, named Atmospheric Terahertz RAdiation SimUlator (ATRASU), for future terahertz observation missions. The line-by-line forward model of the current version assumes the clear-sky condition and 2-D of pencil beam geometry. The retrieval method is based on Rodgers (1976) algorithm. Spectral line parameters within 0 to 3 THz frequency range are gathered from both of the Jet Propulsion Laboratory and High Resolution Transmission (HITRAN) line catalogs and possible to add by users in certain format. An advanced Non-LTE solver in spherical symmetry for molecular rotational transitions in static or expanding atmospheres as shown in Yamada et al. (2018) is also available in ATRASU. We present feasibility studies of the TEREX-1 observation for H$ _{2}$O, O$ _{2}$, O$ _{3}$, and H$ _{2}$O$ _{2}$ vertical profiles in Martian Atmosphere. The CO$ _{2}$ continuum caused by collision-induced absorption is considered by using the HITRAN data. We used Mars Climate Database for atmospheric conditions. Tentative location (landing point), season, and local time were assumed to be 10.5$^\circ$N and 85.5$^\circ$E of latitude and longitude, 49 degrees of solar longitude, and 12 h, respectively. The measurement error was assumed to be 1 K which is equivalent to five minutes integrated noise temperature by our measurement system. The expected errors on the measurement error for O$ _{2}$ profiles are less than 130 ppmv with good measurement response from 10 to 40 km altitudes. The H$ _{2}$O expected errors are less than 30 ppmv from 5 to 15 km altitude. The O$ _{3}$ expected errors are less than 13 ppbv at 40 km altitude with no vertical resolution. Further investigations about sensitivities with wind profile, antenna elevation angle, and dust condition, and error analysis include errors on forward model parameter and a priori profile will be discussed.
- Publication:
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43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E.224Y