MATMOS Trace Gas Detection Limits

Mars solar occultation spectra have been simulated covering the 850 to 4250 cm-1 range at 0.025 cm-1 resolution. Noise and systematic error were added to these spectra, and then a spectral fitting retrieval was performed. This provides an estimate of the sensitivity of the MATMOS instrument to various trace gases in the Martian atmosphere as a function of altitude. MATMOS was developed to fly on the ExoMars 2016 Trace Gas Orbiter mission, but its participated was cancelled by NASA in 2012. A gas sensitivity analysis was performed prior to cancellation, as described in detail in the paper "Solar Occultation FTIR spectrometry at Mars for Trace Gas Detection: A Sensitivity Study", published in 2019 in Earth and Space Science. The main purpose of this web-page is to make those data available.

The limb transmittance spectra themselves are too large to include here. There are 4 occultations, each representing a different dust condition ( τ = 0.0, 0.1, 0.3, 0.6) in the nadir at 1075 cm-1. There are 79 observations per occultation to cover 0 to 200 km tangent altitude. Each observation includes a HgCdTe spectrum covering 700 to 2100 cm-1 and an InSb spectrum covering 1800 to 4306 cm-1, both at 0.020 cm-1 grid spacing. The total spectral information is therefore   4 x 79 x 3906/0.02 * 4 = 247 MB   in a I*4 or R*4 binary format, and substantially larger if an ASCII format were used.

This webpage therefore present only the vmr profiles and their uncertainties. In the case of a gas that cannot be detected, the uncertainty represents the detection limit for that gas. Each file contains four occultations of data. ocltn=1 corresponds to the no-dust case; ocltn=2 is the τ=0.1 case; ocltn=3 is the τ=0.3 case; ocltn=4 is the τ=0.6 case.

The file matmos2018_all.lav.ret contains the detectivity profiles for the 22 gases shown in Table 1 of the paper, after combining the results from multiple windows of the same gas. These data are plotted in figure 8 ("all the above"), fig.9, fig.12 panel (c), and fig.13 panel (a). These data are used to provide the single-occultation aggregated detection limit (SOADL) values in Table 2.

The file matmos2018_all.lsw.ret contains the single-window detectivity profiles for each of the 41 individual windows shown in Table 1 of the paper. These data are used in Fig.12 panels (a) and (b). They are also used for the CH4 SOADL values shown in Table 4.

VersionGas Detectivity ProfilesIndividual Window Detectivity Profiles
20190124 matmos2018_all.lav.ret matmos2018_all.lsw.ret


Geoffrey C. Toon, Carl Christian Liebe, Bijan Nemati, Ian Harris, Armin Kleinboehl, Mark Allen, Vicky Hipkin, Jim Drummond, Marc-Andre Soucy, Yuk L. Yung, Zhao-Cheng Zeng, Debra Wunch, Paul O. Wennberg, Solar Occultation FTIR spectrometry at Mars for Trace Gas Detection: A Sensitivity Study, Earth Space Science, 2019

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