NOMAD on ExoMars Trace Gas Orbiter: One Martian year of observations

2020 ◽  
Author(s):  
Ann Carine Vandaele ◽  
Frank Daerden ◽  
Ian R. Thomas ◽  
Shohei Aoki ◽  
Cédric Depiesse ◽  
...  
Keyword(s):  
Trace Gas ◽  
Vertical Profiles ◽  
Ice Clouds ◽  
Mars Atmosphere ◽  
Solar Occultation ◽  
Composition And Structure ◽  
Temperature And Pressure ◽  
Spectral Channels ◽  
Infrared Channel

<p>The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter has been designed to investigate the composition of Mars' atmosphere, with a particular focus on trace gases, clouds and dust. The instrument probes the ultraviolet and infrared regions covering large parts of the 0.2-4.3 µm spectral range [1,2], with 3 spectral channels: a solar occultation channel (SO – Solar Occultation; 2.3–4.3 μm), a second infrared channel capable of nadir, solar occultation, and limb sounding (LNO – Limb Nadir and solar Occultation; 2.3–3.8 μm), and an ultraviolet/visible channel (UVIS – Ultraviolet and Visible Spectrometer, 200–650 nm).</p> <p>Since its arrival at Mars in April 2018, NOMAD performed solar occultation, nadir and limb observations dedicated to the determination of the composition and structure of the atmosphere. Here we report on the different discoveries highlighted by the instrument during its first full Martian year of observations: investigation of the 2018 Global dust storm and its impact on the water uplifting and escape, on temperature and pressure increases within the atmosphere; dust and ice clouds distribution; ozone measurements; dayglow observations; detection of HCl vertical profiles and in general advances in the analysis of the spectra recorded by the three channels of NOMAD.</p> <p>References</p> <p>[1] Vandaele, A.C., et al., 2015. Planet. Space Sci. 119, 233-249.</p> <p>[2] Vandaele et al., 2018. Space Sci. Rev., 214:80, doi.org/10.1007/s11214-11018-10517-11212.</p>

The Martian environment observed by NOMAD on ExoMars Trace Gas Orbiter

2021 ◽  
Author(s):  
Ann Carine Vandaele ◽  
Frank Daerden ◽  
Ian R. Thomas ◽  
Shohei Aoki ◽  
Cédric Depiesse ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Trace Gas ◽  
Vertical Profiles ◽  
Mars Atmosphere ◽  
Solar Occultation ◽  
Composition And Structure ◽  
Spectral Channels ◽  
Distribution Water ◽  
Infrared Channel

<p>The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter has been designed to investigate the composition of Mars' atmosphere, with a particular focus on trace gases, clouds and dust. The instrument probes the ultraviolet and infrared regions covering large parts of the 0.2-4.3 µm spectral range [1,2], with 3 spectral channels: a solar occultation channel (SO – Solar Occultation; 2.3–4.3 μm), a second infrared channel capable of nadir, solar occultation, and limb sounding (LNO – Limb Nadir and solar Occultation; 2.3–3.8 μm), and an ultraviolet/visible channel (UVIS – Ultraviolet and Visible Spectrometer, 200–650 nm). Since its arrival at Mars in April 2018, NOMAD performed solar occultation, nadir and limb observations dedicated to the determination of the composition and structure of the atmosphere.</p><p>NOMAD has been accumulating data about the Martian atmosphere and its surface since its insertion. We will present some results covering the atmosphere composition including clouds and dust, climatologies of water, carbon monoxide and ozone. We also report on the different discoveries highlighted by the instrument by pointing to a series of contributions to this conference that will present in detail several specific studies, like recent progress in the instrument calibration, the latest CO2 and temperature vertical profiles, studies of aerosol nature and distribution, water vapor profiles and variability, carbon monoxide vertical distribution, dayglow observations; detection of HCl, its vertical profiles and in general advances in the analysis of the spectra recorded by the three channels of NOMAD.</p><p>References</p><p>[1] Vandaele, A.C., et al., 2015. Planet. Space Sci. 119, 233-249.</p><p>[2] Vandaele et al., 2018. Space Sci. Rev., 214:80, doi.org/10.1007/s11214-11018-10517-11212.</p><p> </p>

Observations of the Martian atmosphere by NOMAD on ExoMars Trace Gas Orbiter

2020 ◽  
Author(s):  
Ann Carine Vandaele ◽  
Arianna Piccialli ◽  
Ian R. Thomas ◽  
Frank Daerden ◽  
Shohei Aoki ◽  
...  
Keyword(s):  
Spectral Range ◽  
Dust Storm ◽  
Trace Gases ◽  
Martian Atmosphere ◽  
Trace Gas ◽  
Ice Clouds ◽  
Mars Atmosphere ◽  
Solar Occultation ◽  
Composition And Structure

<p>The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter has been designed to investigate the composition of Mars' atmosphere, with a particular focus on trace gases, clouds and dust probing the ultraviolet and infrared regions covering large parts of the 0.2-4.3 µm spectral range [1,2].</p><p>Since its arrival at Mars in April 2018, NOMAD performed solar occultation, nadir and limb observations dedicated to the determination of the composition and structure of the atmosphere. Here we report on the different discoveries highlighted by the instrument: investigation of the 2018 Global dust storm and its impact on the water uplifting and escape, its impact on temperature increases within the atmosphere as inferred by GCM modeling and observations, the dust and ice clouds distribution during the event, ozone measurements, dayglow observations and in general advances in the analysis of the spectra recorded by the three channels of NOMAD.</p><p>References</p><p>[1] Vandaele, A.C., et al., 2015. Planet. Space Sci. 119, 233-249.</p><p>[2] Vandaele et al., 2018. Space Sci. Rev., 214:80, doi.org/10.1007/s11214-11018-10517-11212.</p>

Nadir retrieval of ice clouds and dust from NOMAD/UVIS on board Exomars TGO

2021 ◽  
Author(s):  
Yannick Willame ◽  
Jon Mason ◽  
Ann C. Vandaele ◽  
Justin Erwin ◽  
Arianna Piccialli ◽  
...  
Keyword(s):  
Spectral Range ◽  
Seasonal Distribution ◽  
Trace Gas ◽  
Ice Clouds ◽  
Mars Atmosphere ◽  
Preliminary Results ◽  
Aerosol Retrieval ◽  
Solar Occultation ◽  
Uv Visible ◽  
Applied Optics

<p>The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter (TGO) has been designed to investigate the composition of Mars' atmosphere using a suite of three spectrometers operating in the UV-visible and infrared. NOMAD is a spectrometer operating in ultraviolet (UV), visible and infrared (IR) wavelengths covering large parts of the 0.2-4.3 µm spectral range [1].</p> <p>The UV-visible “UVIS” instrument covers the spectral range from 200 to 650 nm and can perform solar occultation, nadir and limb observations [2]. The main purpose of UVIS is dedicated to the analysis and monitoring of ozone and aerosols such as dust and ice clouds.  In the present work we will present preliminary results of the aerosol retrieval in the UV recorded in nadir geometry: spatial and seasonal distribution of ice clouds and dust.</p> <div> <p> </p> <p>References<br />[1] Vandaele et al. 2018. Space Sci. Rev.<br />[2] Patel et al., 2017. Applied Optics.</p> </div> <p> </p>

Nadir retrieval of ice clouds, dust and ozone from NOMAD/UVIS on board Exomars TGO

2020 ◽  
Author(s):  
Yannick Willame ◽  
Ann C. Vandaele ◽  
Arianna Piccialli ◽  
Cédric Depiesse ◽  
Frank Daerden ◽  
...  
Keyword(s):  
Spectral Range ◽  
Seasonal Distribution ◽  
Trace Gas ◽  
Ice Clouds ◽  
Mars Atmosphere ◽  
Preliminary Results ◽  
Solar Occultation ◽  
Uv Visible

<p>The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter (TGO) has been designed to investigate the composition of Mars' atmosphere using a suite of three spectrometers operating in the UV-visible and infrared. NOMAD is a spectrometer operating in ultraviolet (UV), visible and infrared (IR) wavelengths covering large parts of the 0.2-4.3 µm spectral range [1].</p> <p>The UV-visible “UVIS” instrument covers the spectral range from 200 to 650 nm and can perform solar occultation, nadir and limb observations [2]. The main purpose of UVIS is dedicated to the analysis and monitoring of ozone and aerosols such as dust and ice clouds.  In the present work we will present preliminary results of UV retrievals recorded in nadir geometry: spatial and seasonal distribution of ice clouds, dust and ozone.</p>

Retrievals of dust and ozone from NOMAD-UVIS

2020 ◽  
Author(s):  
Arianna Piccialli ◽  
Ann Carine Vandaele ◽  
Yannick Willame ◽  
Cedric Depiesse ◽  
Loic Trompet ◽  
...  
Keyword(s):  
Dust Storm ◽  
Circulation Model ◽  
Dust Storms ◽  
Atmospheric Composition ◽  
Trace Gas ◽  
Global Circulation Model ◽  
Global Circulation ◽  
Solar Occultation ◽  
Composition And Structure ◽  
Hydrogen Radicals

<p>We will present two years of observation of <strong>dust</strong> and <strong>ozone</strong> vertical distribution obtained from <strong>NOMAD-UVIS solar occultations</strong>.</p><p>Atmospheric <strong>aerosols</strong> are ubiquitous in the Martian atmosphere and they strongly affect the Martian climate [1]. This is particularly true during dust storms. In June 2018, after a pause of 11 years, a planet-encircling dust storm took place on Mars that lasted two months.</p><p><strong>Ozone</strong>, on the other hand, is a species with a short chemical lifetime and characterized by sharp gradients at the day-night terminator due to photolysis [2]. Odd hydrogen radicals play an important role in the destruction of ozone. This results in a strong anti-correlation between O<sub>3</sub> and H<sub>2</sub>O [2].</p><p>The <strong>NOMAD</strong> (Nadir and Occultation for MArs Discovery) – operating onboard the ExoMars 2016 Trace Gas Orbiter satellite – started to acquire the first scientific measurements on 21 April 2018.</p><p>It is a spectrometer composed of 3 channels: 1) a solar occultation channel (SO) operating in the infrared (2.3-4.3 μm); 2) a second infrared channel LNO (2.3-3.8 μm) capable of doing nadir, as well as solar occultation and limb; and 3) an ultraviolet/visible channel UVIS (200-650 nm) that can work in the three observation modes [3,4]. The UVIS channel has a spectral resolution <1.5 nm. In the solar occultation mode it is mainly devoted to study the climatology of ozone and aerosols content [5].</p><p>Since the beginning of operations, on 21 April 2018, NOMAD-UVIS acquired more than <strong>3000 solar occultations</strong> with a complete coverage of the planet. NOMAD-UVIS spectra are simulated using the line-by-line radiative transfer code ASIMUT-ALVL developed at IASB-BIRA [6]. In a preliminary study based on SPICAM-UV solar occultations (see [7]), ASIMUT was modified to take into account the atmospheric composition and structure at the day-night terminator. As input for ASIMUT, we used gradients predicted by the 3D GEM-Mars v4 Global Circulation Model (GCM) [8,9].</p><p>NOMAD will help us improve our knowledge of the climatology of ozone and aerosols. In particular, we will have the rare opportunity to analyze the distribution of aerosols during a dust storm.</p><p>References:</p><p>[1] Määttänen, A., Listowski, C., Montmessin, F., Maltagliati, L., Reberac, A., Joly, L., Bertaux, J.L., Apr. 2013. Icarus 223, 892–941.</p><p>[2] Lefèvre, F., et al., Aug. 2008. Nature 454, 971–975.</p><p>[3] Vandaele, A.C., et al., Planetary and Space Science, Vol. 119,  pp. 233–249, 2015.</p><p>[4] Neefs, E., et al., Applied Optics, Vol. 54 (28),  pp. 8494-8520, 2015.</p><p>[5] M.R. Patel et al., In: Appl. Opt. 56.10 (2017), pp. 2771–2782. DOI: 10.1364/AO.56.002771.</p><p>[6] Vandaele, A.C., et al., JGR, 2008. 113 doi:10.1029/2008JE003140.</p><p>[7] Piccialli, A., Icarus, in press, https://doi.org/10.1016/j.icarus.2019.113598.</p><p>[8] Neary, L., and F. Daerden (2018), Icarus, 300, 458–476, doi:10.1016/j.icarus.2017.09.028.</p><p>[9] Daerden et al., 2019, Icarus 326, https://doi.org/10.1016/j.icarus.2019.02.030</p>

Observations of CO2 clouds on Mars from TIRVIM and NIR solar occultation measurements onboard TGO

2021 ◽  
Author(s):  
Mikhail Luginin ◽  
Nikolay Ignatiev ◽  
Anna Fedorova ◽  
Alexander Trokhimovskiy ◽  
Alexey Grigoriev ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Chemistry ◽  
Near Infrared ◽  
Trace Gas ◽  
Major Constituent ◽  
Russian Science ◽  
Geophysical Research ◽  
Ice Clouds ◽  
Wind Speeds ◽  
Solar Occultation

<p>Carbon dioxide is the major constituent of the Martian atmosphere. Its seasonal cycle plays an important role in atmospheric dynamics and climate. Formation of the polar CO<sub>2</sub> frost deposits results in up to 30% of atmospheric pressure variations as well as in dramatic change in surface reflectance and emissivity. Another case of carbon dioxide condensation is formation of a CO<sub>2</sub> clouds that are still poorly studied, despite the fact that they have been observed by a number of instruments [1−6] on the orbit of Mars.</p><p>In this work, we will present first results of CO<sub>2</sub> clouds observations from a combination of thermal-infrared (1.7−17 µm) and near-infrared (0.7-1.6 µm) spectra measured by TIRVIM and NIR instruments onboard the ExoMars Trace Gas Orbiter (TGO) in solar occultation geometry. These instruments are part of the Atmospheric Chemistry Suite (ACS), a set of three spectrometers (NIR, MIR, and TIRVIM) that is conducting scientific measurements on the orbit of Mars since the spring of 2018 [7].</p><p>This work was funded by Russian Science Foundation, grant number 20-42-09035.</p><p><strong>References</strong></p><p>[1] Montmessin et al. (2006). Subvisible CO2 ice clouds detected in the mesosphere of Mars. Icarus, 183, 403–410. https://doi.org/10.1016/j.icarus.2006.03.015</p><p>[2] Montmessin et al. (2007). Hyperspectral imaging of convective CO2 ice clouds in the equatorial mesosphere of Mars. Journal of Geophysical Research, 112, E11S90. https://doi.org/10.1029/2007JE002944</p><p>[3] Määttänen et al. (2010). Mapping the mesospheric CO2 clouds on Mars: MEx/OMEGA and MEx/HRSC observations and challenges for atmospheric models. Icarus, 209, 452–469. https://doi.org/10.1016/j.icarus.2010.05.017</p><p>[4] McConnochie et al. (2010). THEMIS-VIS observations of clouds in the Martian mesosphere: Altitudes, wind speeds, and decameter-scale morphology. Icarus, 210, 545–565. https://doi.org/10.1016/j.icarus.2010.07.021</p><p>[5] Vincendon et al. (2011). New near-IR observations of mesospheric CO2 and H2O clouds on Mars. Journal of Geophysical Research, 116, E00J02. https://doi.org/10.1029/2011JE003827</p><p>[6] Jiang et al., (2019). Detection of Mesospheric CO 2 Ice Clouds on Mars in Southern Summer. Geophysical Research Letters, 46(14), 7962–7971. https://doi.org/10.1029/2019GL082029</p><p>[7] Korablev et al., (2018). The Atmospheric Chemistry Suite (ACS) of three spectrometers for the ExoMars 2016 Trace Gas Orbiter. Space Sci. Rev. 214, 7. doi:10.1007/s11214-017-0437-6</p>

scholarly journals New temperature and pressure retrieval algorithm for high-resolution infrared solar occultation spectroscopy: analysis and validation against ACE-FTS and COSMIC

2015 ◽  
Vol 8 (10) ◽  
pp. 10823-10873 ◽  
Author(s):  
K. S. Olsen ◽  
G. C. Toon ◽  
C. D. Boone ◽  
K. Strong
Keyword(s):  
High Resolution ◽  
Atmospheric Chemistry ◽  
Primary Component ◽  
Retrieval Algorithm ◽  
Cold Bias ◽  
Vertical Profiles ◽  
Solar Occultation ◽  
Spatial Coverage ◽  
Temperature And Pressure ◽  
Mean Differences

Abstract. Motivated by the initial selection of a high-resolution solar occultation Fourier transform spectrometer (FTS) to fly to Mars on the ExoMars Trace Gas Orbiter, we have been developing algorithms for retrieving volume mixing ratio vertical profiles of trace gases, the primary component of which is a new algorithm and software for retrieving vertical profiles of temperature and pressure from the spectra. In contrast to Earth-observing instruments, which can rely on accurate meteorological models, a priori information, and spacecraft position, Mars retrievals require a method with minimal reliance on such data. The temperature and pressure retrieval algorithms developed for this work were evaluated using Earth-observing spectra from the Atmospheric Chemistry Experiment (ACE) FTS, a solar occultation instrument in orbit since 2003, and the basis for the instrument selected for a Mars mission. ACE-FTS makes multiple measurements during an occultation, separated in altitude by 1.5–5 km, and we analyze 10 CO2 vibration-rotation bands at each altitude, each with a different usable altitude range. We describe the algorithms and present results of their application and their comparison to the ACE-FTS data products. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) provides vertical profiles of temperature up to 40 km with high vertical resolution. Using six satellites and GPS radio occultation, COSMIC's data product has excellent temporal and spatial coverage, allowing us to find coincident measurements with ACE with very tight criteria: less than 1.5 h and 150 km. We present an inter-comparison of temperature profiles retrieved from ACE-FTS using our algorithm, that of the ACE Science Team (v3.5), and from COSMIC. When our retrievals are compared to ACE-FTS v3.5, we find mean differences between −5 and +2 K, and that our retrieved profiles have no seasonal or zonal biases, but do have a warm bias in the stratosphere and a cold bias in the mesosphere. When compared to COSMIC, we do not observe a warm/cool bias and mean differences are between −4 and +1 K. COSMIC comparisons are restricted to below 40 km, where our retrievals have the best agreement with ACE-FTS v3.5. When comparing ACE-FTS v3.5 to COSMIC we observe a cold bias in COSMIC of 0.5 K, and mean differences are between −0.9 and +0.6 K.

Characterization of the atmospheric gravity waves on Mars at altitudes 10-180 km as measured by the ACS/TGO solar occultations

2020 ◽  
Author(s):  
Ekaterina Starichenko ◽  
Denis Belyaev ◽  
Alexander Medvedev ◽  
Anna Fedorova ◽  
Oleg Korablev ◽  
...  
Keyword(s):  
Spectral Range ◽  
Gravity Waves ◽  
Atmospheric Chemistry ◽  
Thin Layers ◽  
Resolving Power ◽  
Trace Gas ◽  
Atmospheric Gravity Waves ◽  
Solar Occultation ◽  
Atmospheric Gravity ◽  
Infrared Channel

<p>Atmospheric gravity waves (GW) are periodic oscillations of air masses that manifest themselves as fluctuations of density, temperature, pressure and other quantities. Studying vertical distributions of density and temperature helps to characterize vertical propagation of GWs and evaluate their influence on the coupling between atmospheric layers.</p><p>We report on the first results of GWs retrievals in the Martian atmosphere from the solar occultation experiment performed by the Atmospheric Chemistry Suite (ACS) onboard the ExoMars Trace Gas Orbiter TGO [1]. This is the first time when GWs were measured simultaneously in almost the entire atmosphere. The ACS is a set of infrared spectrometers operating on the orbit of Mars since April 2018. The mid-infrared channel (ACS-MIR) is a cross-dispersion spectrometer covering the 2.3–4.2 µm spectral range with the resolving power reaching ~30 000. In the solar occultation mode the spectrometer can observe thin layers of the Martian thermosphere and lower atmosphere in strong (e.g. 2.7 and 4.3 μm) and weak (about 3 μm) CO<sub>2</sub> absorption bands with vertical resolution ~1 km. The near-infrared channel (ACS-NIR) is another echelle spectrometer working in the 0.73–1.6 µm spectral range with the resolving power ~25000 [2]. Due to the high resolution, these instruments (operating simultaneously) allow for deriving the temperature, pressure and density fluctuations at the unprecedented altitude range from 10 to 180 km. The dataset we present consists of more than 100 vertical profiles derived at seasons from the second half of MY34 to the beginning of MY35 in the both Martian hemispheres. The data analysis in IKI is supported by the RSF grant #20-42-09035.</p><p> </p><p>REFERENCES</p><p>[1] Korablev O. et al., 2018. The Atmospheric Chemistry Suite (ACS) of three spectrometers for the ExoMars 2016 Trace Gas Orbiter. Space Sci. Rev., 214:7. DOI 10.1007/s11214-017-0437-6.</p><p>[2] Fedorova A. et al., 2020. Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season. Science, eaay9522. DOI: 10.1126/science.aay9522.</p>

scholarly journals Inter-comparison of stratospheric O<sub>3</sub> and NO<sub>2</sub> abundances retrieved from balloon borne direct sun observations and Envisat/SCIAMACHY limb measurements

2005 ◽  
Vol 5 (5) ◽  
pp. 10747-10797
Author(s):  
A. Butz ◽  
H. Bösch ◽  
C. Camy-Peyret ◽  
M. Chipperfield ◽  
M. Dorf ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Optical Absorption ◽  
Ultra Violet ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Line Of Sight ◽  
Vertical Profiles ◽  
Altitude Range ◽  
Solar Occultation ◽  
Uv Visible

Abstract. Stratospheric O3 and NO2 abundances measured by different remote sensing instruments are inter-compared: (1) Line-of-sight absorptions and vertical profiles inferred from solar spectra in the ultra-violet (UV), visible and infrared (IR) wavelength ranges measured by the LPMA/DOAS (Limb Profile Monitor of the Atmosphere/Differential Optical Absorption Spectroscopy) balloon payload during balloon ascent/descent and solar occultation are examined with respect to internal consistency. (2) The balloon borne stratospheric profiles of O3 and NO2 are compared to collocated space-borne skylight limb observations of the Envisat/SCIAMACHY satellite instrument. The trace gas profiles are retrieved from SCIAMACHY spectra using different algorithms developed at the Universities of Bremen and Heidelberg and at the Harvard-Smithsonian Center for Astrophysics. A comparison scheme is used that accounts for the spatial and temporal mismatch as well as differing photochemical conditions between the balloon and satellite borne measurements. It is found that the balloon borne measurements internally agree to within ±10% and ±20% for O3 and NO2, respectively, whereas the agreement with the satellite is ±20% for both gases in the 20 km to 30 km altitude range and in general worse below 20 km.

scholarly journals New temperature and pressure retrieval algorithm for high-resolution infrared solar occultation spectroscopy: analysis and validation against ACE-FTS and COSMIC

2016 ◽  
Vol 9 (3) ◽  
pp. 1063-1082 ◽  
Author(s):  
Kevin S. Olsen ◽  
Geoffrey C. Toon ◽  
Chris D. Boone ◽  
Kimberly Strong
Keyword(s):  
High Resolution ◽  
Atmospheric Chemistry ◽  
Primary Component ◽  
Retrieval Algorithm ◽  
Cold Bias ◽  
Vertical Profiles ◽  
Solar Occultation ◽  
Spatial Coverage ◽  
Temperature And Pressure ◽  
Mean Differences

Abstract. Motivated by the initial selection of a high-resolution solar occultation Fourier transform spectrometer (FTS) to fly to Mars on the ExoMars Trace Gas Orbiter, we have been developing algorithms for retrieving volume mixing ratio vertical profiles of trace gases, the primary component of which is a new algorithm and software for retrieving vertical profiles of temperature and pressure from the spectra. In contrast to Earth-observing instruments, which can rely on accurate meteorological models, a priori information, and spacecraft position, Mars retrievals require a method with minimal reliance on such data. The temperature and pressure retrieval algorithms developed for this work were evaluated using Earth-observing spectra from the Atmospheric Chemistry Experiment (ACE) FTS, a solar occultation instrument in orbit since 2003, and the basis for the instrument selected for a Mars mission. ACE-FTS makes multiple measurements during an occultation, separated in altitude by 1.5–5 km, and we analyse 10 CO2 vibration–rotation bands at each altitude, each with a different usable altitude range. We describe the algorithms and present results of their application and their comparison to the ACE-FTS data products. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) provides vertical profiles of temperature up to 40 km with high vertical resolution. Using six satellites and GPS radio occultation, COSMIC's data product has excellent temporal and spatial coverage, allowing us to find coincident measurements with ACE with very tight criteria: less than 1.5 h and 150 km. We present an intercomparison of temperature profiles retrieved from ACE-FTS using our algorithm, that of the ACE Science Team (v3.5), and from COSMIC. When our retrievals are compared to ACE-FTS v3.5, we find mean differences between −5 and +2 K and that our retrieved profiles have no seasonal or zonal biases but do have a warm bias in the stratosphere and a cold bias in the mesosphere. When compared to COSMIC, we do not observe a warm/cool bias and mean differences are between −4 and +1 K. COSMIC comparisons are restricted to below 40 km, where our retrievals have the best agreement with ACE-FTS v3.5. When comparing ACE-FTS v3.5 to COSMIC we observe a cold bias in COSMIC of 0.5 K, and mean differences are between −0.9 and +0.6 K.

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