Solar Occultation FTIR Spectrometry at Mars for Trace Gas Detection: A Sensitivity Study

Earth and Space Science

Marc‐André Soucy¹  Vicky Hipkin²  Debra Wunch³  Zhao‐Cheng Zeng³  Paul O. Wennberg³  Jim Drummond⁴  Geoffrey C. Toon⁵  Carl Christian Liebe⁵  Mark Allen⁵  Yuk L. Yung⁵  Bijan Nemati⁵  Ian Harris⁵  Armin Kleinböhl⁵ 

[1] ABB Canada Quebec City Quebec Canada;Canadian Space Agency Longueuil Quebec Canada;Department of Physics California Institute of Technology Pasadena CA USA;Department of Physics and Atmospheric Science Dalhousie University Halifax Nova Scotia Canada;Jet Propulsion Laboratory, California Institute of Technology Pasadena CA USA;

关键词: Mars;    atmosphere;    trace gases;    FTIR spectrometer;    detection limits;   

DOI  :  10.1029/2018EA000469

来源: DOAJ

【 摘 要 】

Abstract A sensitivity study has been performed to estimate detection limits of various atmospheric trace gases achievable by a Mars‐orbiting solar occultation Fourier transform infrared (FTIR) spectrometer. This was accomplished by first computing realistic limb transmittance spectra based on a model (T, P, VMR, and dust profiles) of the Mars atmosphere and adding appropriate noise and systematic errors based on assumed instrument design/configuration/performance. We then performed spectral fits to the resulting synthetic spectra to derive slant column abundances and their uncertainties. A profile retrieval was performed to infer limits of detection. This methodology was applied to a Mars‐orbiting FTIR solar occultation spectrometer covering the 850–4,300 cm−1 spectral region at 0.025‐cm−1 resolution. We conclude that most gases can be retrieved with a single‐occultation sensitivity of 20–100 ppt. But this sensitivity varies considerably with the dust loading, especially for gases whose strongest absorption bands are toward higher wavenumbers where scattering is large. We conclude that for CH4, the ν4 band centered at 1,305 cm−1, despite being more than 2 times weaker than the ν3 band centered at 3,015 cm−1, offers better sensitivity due to its close spectral proximity to the dust extinction minimum. We also conclude that for the purpose of CH4 detection, a high‐resolution (0.025 cm−1) broadband instrument would have a substantial advantage over a medium‐resolution (0.15 cm−1) instrument, despite the latter having a much larger signal‐to‐noise ratio.

【 授权许可】

Unknown