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.

Reference

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