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| Titel |
The ExoMars Trace Gas Orbiter NOMAD Spectrometer Suite for Nadir and Solar Occultation Observations of Mars' Atmosphere |
| VerfasserIn |
Ian Thomas, Ann Carine Vandaele, Josè Juan Lopez-Moreno, Manish Patel, Giancarlo Bellucci, Rachel Drummond, Eduard Neefs, Cédric Depiesse, Frank Daerden, Julio Rodriguez-Gomez, Lori Neary, Séverine Robert, Yannick Willame, Arnaud Mahieux |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110509
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| Publikation (Nr.) |
 EGU/EGU2015-10511.pdf |
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| Zusammenfassung |
| NOMAD (Nadir and Occultation for MArs Discovery) is one of four instruments
on board the ExoMars Trace Gas Orbiter, scheduled for launch in January 2016
and to begin nominal science mission around Mars in late 2017. It consists of a
suite of three high-resolution spectrometers – Solar Occultation (SO), LNO (Limb
Nadir and Occultation) and UVIS (Ultraviolet-Visible) – which will generate a
huge dataset of Martian atmospheric observations during the mission, across a wide
spectral range. Specifically, the SO spectrometer channel will perform occultation
measurements, operating between 2.2-4.3μm at a resolution of Â0.15cm-1, with
180-1000m vertical spatial resolution and an SNR of 1500-3000. LNO will perform limb
scanning, nadir and occultation measurements, operating between 2.2-3.8μm at a
resolution of Â0.3cm-1. In nadir, global coverage will extend between ±74O latitude
with an IFOV of 0.5x17km on the surface. This channel can also make occultation
measurements should the SO channel fail. UVIS will make limb, nadir and occultation
measurements between 200-650nm, at a resolution of 1nm. It will have 300-1000m
vertical resolution during occultation and 5x60km ground resolution during 15s nadir
observations.
An order-of-magnitude increase in spectral resolution over previous instruments will
allow NOMAD to map previously unresolvable gas species, such as important trace gases and
isotopes. CO, CO2, H2O, C2H2, C2H4, C2H6, H2CO, CH4, SO2, H2S, HCl, O3 and several
isotopologues of methane and water will be detectable, providing crucial measurements of
the Martian D/H and methane isotope ratios. It will also be possible to map the sources and
sinks of these gases, such as regions of surface volcanism/outgassing and atmospheric
production, over the course of an entire Martian year, to further constrain atmospheric
dynamics and climatology. NOMAD will also continue to monitor the Martian water, carbon,
ozone and dust cycles, extending existing datasets made by successive space missions in the
past decades, and to derive surface UV radiation levels. Using SO and LNO in
combination with UVIS, aerosol properties such as optical depth, composition and size
distribution can be derived for atmospheric particles and for distinguishing dust from ice
aerosols.
The NOMAD science team will interpret instrument observations using simulations of the
GEM-Mars global circulation model. This GCM can model complex atmospheric and
chemical processes, such as heterogeneous chemistry, phase transitions, and regolith
interaction on both a localised and global scale. Model results can then influence the selection
of observational modes and measurement parameters, refining future observations to optimise
science return.
The instrument, as of January 2015, is currently being assembled and tested. By April, the
instrument will have undergone a full range of tests, calibration at Centre Spatial de Liège,
and will have been delivered to ESA for mounting onto the Trace Gas Orbiter. |
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