Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Methane on Mars: New insights into the sensitivity of CH4 with the
  NOMAD/ExoMars spectrometer through its first in-flight calibration   The Nadir and Occultation for MArs Discovery instrument (NOMAD), onboard the
ExoMars Trace Gas Orbiter (TGO) spacecraft was conceived to observe Mars in
solar occultation, nadir, and limb geometries, and will be able to produce an
outstanding amount of diverse data, mostly focused on properties of the
atmosphere. The infrared channels of the instrument operate by combining an
echelle grating spectrometer with an Acousto-Optical Tunable Filter (AOTF).
Using in-flight data, we characterized the instrument performance and
parameterized its calibration. In particular: an accurate frequency calibration
was achieved, together with its variability due to thermal effects on the
grating. The AOTF properties and transfer function were also quantified, and we
developed and tested a realistic method to compute the spectral continuum
transmitted through the coupled grating + AOTF system. The calibration results
enabled unprecedented insights into the important problem of the sensitivity of
NOMAD to methane abundances in the atmosphere. We also deeply characterized its
performance under realistic conditions of varying aerosol abundances, diverse
albedos and changing illumination conditions as foreseen over the nominal
mission. The results show that, in low aerosol conditions, NOMAD single
spectrum, 1-sigma sensitivity to CH4 is around 0.33 ppbv at 20 km of altitude
when performing solar occultations, and better than 1 ppbv below 30 km. In
dusty conditions, we show that the sensitivity drops to 0 below 10 km. In Nadir
geometry, results demonstrate that NOMAD will be able to produce seasonal maps
of CH4 with a sensitivity around 5 ppbv over most of planet's surface with
spatial integration over 5x5 degrees bins. Results show also that such numbers
can be improved by a factor of 10 to 30 by data binning. Overall, our results
quantify NOMAD's capability to address the variable aspects of Martian climate.

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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: quant-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
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The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: gr-qc