Temperature and CO2 density distribution in Mars upper atmosphere from the ACS-MIR / TGO solar occultations at 2.7 μm absorption band

2020 ◽  
Author(s):  
Denis Belyaev ◽  
Anna Fedorova ◽  
Alexander Trokhimovskiy ◽  
Oleg Korablev ◽  
Franck Montmessin ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Near Infrared ◽  
Molecular Diffusion ◽  
Iteration Scheme ◽  
Resolving Power ◽  
Trace Gas ◽  
Spectral Interval ◽  
Absorption Bands ◽  
The Moment ◽  
Infrared Channel

<p>The mid-infrared channel of the Atmospheric Chemistry Suite (ACS-MIR) is a cross-dispersion echelle spectrometer dedicated to solar occultation measurements in the 2.3–4.3 μm wavelength range [1]. The instrumental resolving power λ/Δλ reaches ~30 000, while the altitude resolution is ~1 km. ACS-MIR began regular science operations in April 2018 on board the ExoMars Trace Gas Orbiter (TGO). Each occultation session covers a spectral interval with one or a few CO<sub>2</sub> absorption bands appropriate for the atmospheric density and temperature retrievals.</p><p>In this paper, we present results from data analysis in the 2.65-2.7 μm spectral range hosting strong CO<sub>2</sub> absorption bands detectable up to 180 km. It provides us with unprecedented capability to profile CO<sub>2</sub> from 20 to 180 km, covering the troposphere, the mesosphere and the thermosphere of Mars. The homopause is found around ~130 km and CO<sub>2</sub> mixing ratio decreases from 96% to 20-40% at 180 km due to photolysis and molecular diffusion. A multiple iteration scheme was applied to retrieve CO<sub>2</sub> density and temperature from the rotational absorption lines, while pressure was estimated assuming hydrostatic equilibrium. The vertical profiles coincide well with the simultaneous occultations performed below 100 km by the near-infrared channel ACS-NIR [2]. At the moment, our MIR channel dataset is made of >100 profiles encompassing the second half of MY34 and the beginning of MY35 in both martian hemispheres. The retrievals of density/temperature profiles in IKI are funded by the RSF grant #20-42-09035.</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>

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>

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 First observation of the magnetic dipole CO2 absorption band at 3.3 μm in the atmosphere of Mars by the ExoMars Trace Gas Orbiter ACS instrument

2020 ◽  
Vol 639 ◽  
pp. A142 ◽  
Author(s):  
A. Trokhimovskiy ◽  
V. Perevalov ◽  
O. Korablev ◽  
A. F. Fedorova ◽  
K. S. Olsen ◽  
...  
Keyword(s):  
Absorption Band ◽  
Magnetic Dipole ◽  
Atmospheric Chemistry ◽  
Electric Quadrupole ◽  
Optical Path Length ◽  
Trace Gas ◽  
First Year ◽  
Co2 Absorption ◽  
Absorption Bands ◽  
Atmospheric Species

The atmosphere of Mars is dominated by CO2, making it a natural laboratory for studying CO2 spectroscopy. The Atmospheric Chemistry Suite (ACS) on board the ExoMars Trace Gas Orbiter uses solar occultation geometry to search for minor atmospheric species. During the first year of ACS observations, the attention was focused on the spectral range covering the methane ν3 absorption band, 2900–3300 cm−1, which has previously been observed on Mars. No methane was detected by ACS; instead, an improvement of the data processing has led to the identification of 30 weak absorption lines that were missing from spectroscopic databases. Periodic series of absorptions up to ~1.6% deep are observed systematically around the position of the methane Q-branch when the line of sight penetrates below 20 km (creating an optical path length of 300–400 km, with an effective pressure of a few millibar). The observed frequencies of the discovered lines match theoretically computed positions of the P-, Q-, and R-branches of the magnetic dipole and electric quadrupole 01111-00001 (ν2 + ν3) absorption bands of the main CO2 isotopologue; neither band has been measured or computed before. The relative depths of the observed spectral features support the magnetic dipole origin of the band. The contribution of the electric quadrupole absorption is several times smaller. Here we report the first observational evidence of a magnetic dipole CO2 absorption.

scholarly journals Noninvasive Monitoring of Glucose Using Near-Infrared Reflection Spectroscopy of Skin—Constraints and Effective Novel Strategy in Multivariate Calibration

Biosensors ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 64
Author(s):  
H. Michael Heise ◽  
Sven Delbeck ◽  
Ralf Marbach
Keyword(s):  
Blood Glucose ◽  
Near Infrared ◽  
Multivariate Calibration ◽  
Response Spectrum ◽  
Blood Glucose Monitoring ◽  
Oral Glucose ◽  
Spectral Interval ◽  
Sample Population ◽  
Vibration Band ◽  
Absorption Bands

For many years, successful noninvasive blood glucose monitoring assays have been announced, among which near-infrared (NIR) spectroscopy of skin is a promising analytical method. Owing to the tiny absorption bands of the glucose buried among a dominating variable spectral background, multivariate calibration is required to achieve applicability for blood glucose self-monitoring. The most useful spectral range with important analyte fingerprint signatures is the NIR spectral interval containing combination and overtone vibration band regions. A strategy called science-based calibration (SBC) has been developed that relies on a priori information of the glucose signal (“response spectrum”) and the spectral noise, i.e., estimates of the variance of a sample population with negligible glucose dynamics. For the SBC method using transcutaneous reflection skin spectra, the response spectrum requires scaling due to the wavelength-dependent photon penetration depth, as obtained by Monte Carlo simulations of photon migration based on estimates of optical tissue constants. Results for tissue glucose concentrations are presented using lip NIR-spectra of a type-1 diabetic subject recorded under modified oral glucose tolerance test (OGTT) conditions. The results from the SBC method are extremely promising, as statistical calibrations show limitations under the conditions of ill-posed equation systems as experienced for tissue measurements. The temporal profile differences between the glucose concentration in blood and skin tissue were discussed in detail but needed to be further evaluated.

scholarly journals Performance of a geostationary mission, geoCARB, to measure CO<sub>2</sub>, CH<sub>4</sub> and CO column-averaged concentrations

2013 ◽  
Vol 6 (5) ◽  
pp. 9397-9465 ◽  
Author(s):  
I. N. Polonsky ◽  
D.M. O'Brien ◽  
J. B. Kumer ◽  
C. W. O'Dell ◽  
the geoCARB Team
Keyword(s):  
Power Plants ◽  
Near Infrared ◽  
Trace Gas ◽  
Reliable Estimate ◽  
Absorption Bands ◽  
Particulate Filters ◽  
Noise Characteristics ◽  
Gaussian Plume ◽  
Spectral Channels ◽  
Emission Strength

Abstract. GeoCARB is a proposed instrument to measure column averaged concentrations of CO2, CH4 and CO from geostationary orbit using reflected sunlight in near-infrared absorption bands of the gases. The scanning options, spectral channels and noise characteristics of geoCARB and two descope options are described. The accuracy of concentrations from geoCARB data is investigated using end-to-end retrievals; spectra at the top of the atmosphere in the geoCARB bands are simulated with realistic trace gas profiles, meteorology, aerosol, cloud and surface properties, and then the concentrations of CO2, CH4 and CO are estimated from the spectra after addition of noise characteristic of geoCARB. The sensitivity of the algorithm to aerosol, the prior distributions assumed for the gases and the meteorology are investigated. The contiguous spatial sampling and fine temporal resolution that geoCARB could provide opens the possibility of monitoring localised sources such as power plants. Simulations of emissions from a power plant with a gaussian plume are conducted to assess the accuracy with which the emission strength may be recovered from geoCARB spectra. Scenarios for "clean" and "dirty" power plants are examined. It is found that a reliable estimate of the emission rate is possible, especially for power plants that have particulate filters, by averaging multiple snap-shots of the CO2 field surrounding the plant. The result holds even in the presence of partial cloud cover.

CO and O2 in the Martian atmosphere with ACS NIR onboard TGO.

2021 ◽  
Author(s):  
Anna Fedorova ◽  
Franck Lefèvre ◽  
Alexander Trokhimovskiy ◽  
Oleg Korablev ◽  
Franck Montmessin ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
General Circulation ◽  
Near Infrared ◽  
Circulation Model ◽  
Carbon Oxide ◽  
Martian Atmosphere ◽  
Resolving Power ◽  
Mixing Ratio ◽  
Mars Atmosphere ◽  
Mixing Ratios

&lt;p&gt;The molecular oxygen (O2) and carbon oxide (CO) are minor constituents of the Martian atmosphere with the annual mean mixing ratio of (1560 &amp;#177; 60 ppm) and (673 &amp;#177; 2.6 ppm), respectively (Krasnopolsky, 2017). Both are non-condensable species and their latitudinal variations are induced by condensation and sublimation of CO&lt;sub&gt;2&lt;/sub&gt; from the polar caps that result in enrichment and depletion and seasonal variations are following the total CO&lt;sub&gt;2&lt;/sub&gt; amount in the atmosphere.&lt;/p&gt;&lt;p&gt;The Atmospheric Chemistry Suite (ACS) is a set of three spectrometers (-NIR, -MIR, and -TIRVIM) intended to observe Mars atmosphere onboard the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission (Korablev et al., 2018). The near infrared channel (NIR) is a compact spectrometer operating in the range of 0.7&amp;#8211;1.7 &amp;#181;m with a resolving power of &amp;#955;/&amp;#916;&amp;#955; ~ 25,000. It is designed to operate in nadir and in solar occultation modes. The simultaneous vertical profiling of the O&lt;sub&gt;2 &lt;/sub&gt;and CO density at altitudes of 10-60 km based on 0.76 &amp;#181;m and 1.57 &amp;#181;m bands, respectively, is a unique feature of the ACS NIR science in occultation. In this work we present the seasonal and latitudional distribution of the O&lt;sub&gt;2&lt;/sub&gt; and CO mixing ratios obtained for period of 2018-2020 (MY34 and35) and the comparison with the LMD General Circulation model. We report the averaged mixing ratio for CO of ~950 ppm and for O2 of~1800 ppm at low altitudes (~20 km). Also, we detected extremely enriched CO layer at 10-15 km in the southern polar region at Ls=100-200&amp;#176; both for MY34 and MY35.&lt;/p&gt;

The High Resolution Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 316-317
Author(s):  
A. V. Crewe
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Vacuum ◽  
Scanning Transmission Electron Microscope ◽  
Ultra High Vacuum ◽  
Resolving Power ◽  
Imaging Characteristics ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Moment

The high resolution STEM is now a fact of life. I think that we have, in the last few years, demonstrated that this instrument is capable of the same resolving power as a CEM but is sufficiently different in its imaging characteristics to offer some real advantages.It seems possible to prove in a quite general way that only a field emission source can give adequate intensity for the highest resolution^ and at the moment this means operating at ultra high vacuum levels. Our experience, however, is that neither the source nor the vacuum are difficult to manage and indeed are simpler than many other systems and substantially trouble-free.

scholarly journals Line observations of the 30-Dor complex and N159A5 with the MPE imaging NIR spectrometer FAST

1991 ◽  
Vol 148 ◽  
pp. 205-206 ◽  
Author(s):  
A. Krabbe ◽  
J. Storey ◽  
V. Rotaciuc ◽  
S. Drapatz ◽  
R. Genzel
Keyword(s):  
Spatial Resolution ◽  
Molecular Hydrogen ◽  
Near Infrared ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Emission Lines ◽  
Resolving Power ◽  
Max Planck ◽  
First Time ◽  
Infrared Array

Images with subarcsec spatial resolution in the light of near-infrared atomic (Bry) and molecular hydrogen H2 (S(1) v=1-0) emission lines were obtained for some extended, pointlike objects in the Large Magellanic Cloud (LMC) for the first time. We used the Max-Planck-Institut für extraterrestrische Physik (MPE) near-infrared array spectrometer FAST (image scale 0.8”/pix, spectral resolving power 950) at the ESO/MPI 2.2m telescope, La Silla. We present some results on the 30-Dor complex and N159A5.

scholarly journals Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS) in the red spectral range

2007 ◽  
Vol 7 (1) ◽  
pp. 69-79 ◽  
Author(s):  
T. Wagner ◽  
S. Beirle ◽  
T. Deutschmann ◽  
M. Grzegorski ◽  
U. Platt
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Spectral Range ◽  
Near Infrared ◽  
Vegetation Type ◽  
Differential Optical Absorption Spectroscopy ◽  
Trace Gas ◽  
Satellite Monitoring ◽  
Optical Absorption Spectroscopy ◽  
Vegetation Types

Abstract. A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm) reflectance structures (i.e. "fingerprint" structures) of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS), which is usually applied for the analysis of atmospheric trace gas absorptions. Since the spectra of atmospheric absorption and vegetation reflectance are simultaneously included in the analysis, the effects of atmospheric absorptions are automatically corrected (in contrast to other algorithms). The inclusion of the vegetation spectra also significantly improves the results of the trace gas retrieval. The global maps of the results illustrate the seasonal cycles of different vegetation types. In addition to the vegetation distribution on land, they also show patterns of biological activity in the oceans. Our results indicate that improved sets of vegetation spectra might lead to more accurate and more specific identification of vegetation type in the future.

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