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

Denis Belyaev, Anna Fedorova, Alexander Trokhimovskiy, Oleg Korablev, Franck Montmessin, Juan Alday, Kevin Olsen, Miguel Lopez-Valverde

<figure><img src="image_1.png" /></figure>

## To cite this version:

Denis Belyaev, Anna Fedorova, Alexander Trokhimovskiy, Oleg Korablev, Franck Montmessin, et al. Temperature and CO2 density distribution in Mars upper atmosphere from the ACS-MIR / TGO solar occultations at 2.7 µm absorption band. 22nd EGU General Assembly, May 2020, Online, Unknown Region. pp.id.18371, 10.5194/egusphere-egu2020-18371. insu-04494906

HAL Id: insu-04494906

https://insu.hal.science/insu-04494906

Submitted on 5 Jun 2024

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<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Temperature and CO2 density distribution in Mars upper atmosphere from the ACS-MIR / TGO solar occultations at 2.7 µm absorption band

Denis Belyaev, Anna Fedorova, Alexander Trokhimovskiy, Oleg Korablev, Franck Montmessin, Juan Alday, Kevin Olsen, Miguel Lopez-Valverde

<figure><img src="image_1.png" /></figure>

## To cite this version:

Denis Belyaev, Anna Fedorova, Alexander Trokhimovskiy, Oleg Korablev, Franck Montmessin, et al. Temperature and CO2 density distribution in Mars upper atmosphere from the ACS-MIR / TGO solar occultations at 2.7 µm absorption band. 22nd EGU General Assembly, May 2020, Online, Unknown Region. pp.id.18371, 10.5194/egusphere-egu2020-18371. insu-04494906

HAL Id: insu-04494906

https://insu.hal.science/insu-04494906v1

Submitted on 5 Jun 2024

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

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

**Denis Belyaev (1), Anna Fedorova (1), Alexander Trokhimovskiy (1), Oleg Korablev (1), Franck Montmessin (2), Juan Alday (3), Kevin Olsen (3), and Miguel Lopez-Valverde (4) and ACS team**

(1) Space Research Institute (IKI), Moscow, Russia:

(2) LATMOS/CNRS, Guyancourt, France

(3) University of Oxford

(4) IAA, Granada, Spain

<figure><img src="image_5.png" /></figure>
<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

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

**Denis Belyaev** (1), **Anna Fedorova** (1), **Alexander Trokhimovskiy** (1), **Oleg Korablev** (1), **Franck Montmessin** (2), **Juan Alday** (3), **Kevin Olsen** (3), and **Miguel Lopez-Valverde** (4)

and ACS team

(1) Space Research Institute (IKI), Moscow, Russia:

(2) LATMOS/CNRS, Guyancourt, France

(3) University of Oxford

(4) IAA, Granada, Spain

<figure><img src="image_5.png" /></figure>
## Solar occultation by ExoMars Trace Gas Orbiter (April 2018 – nowadays)

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

**Measured atmospheric transmission spectrum:**

$$J_A(\nu, z) = \frac{F(\nu, z)}{F_0(\nu)}$$

$F_0(\nu)$ – pure solar spectrum;

$F_0(\nu, z)$ – solar spectrum, transmitted through atmosphere at tangent altitude z.

## Atmospheric Chemistry Suite (ACS)

[Korablev et al., 2018, Sp. Sci. Rev.]

**Science goals:** altitude sensitive profiling of atmospheric temperature, density, minor species (CO, H₂O, HDO, CH₄ etc.)

**ACS-MIR channel:**

* Echelle spectrometer

* Cross-dispersion system

* Spectral range 2.3 – 4.2 µm

* Resolving power $\lambda/\Delta\lambda \sim 30 000$

* FOV: 0.23°×0.02° (0.2-2 km)
# Solar occultation by ExoMars Trace Gas Orbiter (April 2018 – nowadays)

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

Measured atmospheric transmission spectrum:

$$J_A(\nu, z) = \frac{F(\nu, z)}{F_0(\nu)}$$

$F_0(\nu)$ – pure solar spectrum;

$F_0(\nu, z)$ – solar spectrum, transmitted through atmosphere at tangent altitude z.

## Atmospheric Chemistry Suite (ACS)

[Korablev et al., 2018, Sp. Sci. Rev.]

**Science goals:** altitude sensitive profiling of atmospheric temperature, density, minor species (CO, H₂O, HDO, CH₄ etc.)

**ACS-MIR channel:**

* Echelle spectrometer

* Cross-dispersion system

* Spectral range 2.3 – 4.2 µm

* Resolving power $\lambda/\Delta\lambda \sim 30 000$

* FOV: 0.23°×0.02° (0.2-2 km)
CO₂ spectroscopy around 2.7 µm

<figure><img src="image_8.png" /><figcaption>Transmission spectra measured at one occultation in spectral range ~2.7 µm (echelle order 221)</figcaption></figure>
CO₂ spectroscopy around 2.7 µm

<figure><img src="image_8.png" /><figcaption>Transmission spectra measured at one occultation in spectral range ~2.7 µm (echelle order 221)</figcaption></figure>
$$J(z) = \exp\left[-\int\left(\sigma_{CO_2}(T,p)n_{CO_2}(z) + \sigma_{H_2O}(T,p)n_{H_2O}(z) + 5F_{SMOW}\sigma_{HDO}(T,p)n_{H_2O}(z)\right)dz - \tau_{aer}\right]$$

J(Z) - transmission, σ(T,p) – CO₂ and H₂O absorption cross sections, n – CO₂ and H₂O number densities, F<sub>SMOW</sub>=1.3·10⁻⁴, τ<sub>aer</sub> – aerosol slant opacity.

1) Spectroscopic database HITRAN 2016 for σ(T,p) and CO₂ broadening for H₂O lines [Gordon et al., 2017; Gamache et al., 2016; Devi et al., 2017];

2) 1st guess for (T, p), n<sub>CO2</sub> and n<sub>H2O</sub> profiles from the MCD5.3 (climatology);

3) Direct retrievals of T(z), n<sub>CO2</sub> and n<sub>H2O</sub> at a multi iteration scheme while hydrostatic pressure: p(z) = p<sub>o</sub>exp(-∫ m(z)g(z) dz)
$$J(z) = \exp\left[-\int\left(\sigma_{CO_2}(T,p)n_{CO_2}(z) + \sigma_{H_2O}(T,p)n_{H_2O}(z) + 5F_{SMOW}\sigma_{HDO}(T,p)n_{H_2O}(z)\right)dz - \tau_{aer}\right]$$

J(Z) - transmission, σ(T,p) – CO₂ and H₂O absorption cross sections, n – CO₂ and H₂O number densities, F<sub>SMOW</sub>=1.3·10⁻⁴, τ<sub>aer</sub> – aerosol slant opacity.

1) Spectroscopic database HITRAN 2016 for σ(T,p) and CO₂ broadening for H₂O lines [Gordon et al., 2017; Gamache et al., 2016; Devi et al., 2017];

2) 1st guess for (T, p), n<sub>CO₂</sub> and n<sub>H₂O</sub> profiles from the MCD5.3 (climatology);

3) Direct retrievals of T(z), n<sub>CO₂</sub> and n<sub>H₂O</sub> at a multi iteration scheme while hydrostatic pressure: p(z) = p₀exp(-∫ m(z)g(z) dz)
4) Use Levenberg-Marquardt algorithm with an Jacobian based on cross-section derivatives dσ/dT:

<figure><img src="image_9.png" /><figcaption>CO₂, H₂O and HDO spectroscopy at 2.65-2.7 µm range (MIR echelle orders from 221 to 224)</figcaption></figure>
4) Use Levenberg-Marquardt algorithm with an Jacobian based on cross-section derivatives dσ/dT:

<figure><img src="image_9.png" /><figcaption>CO₂, H₂O and HDO spectroscopy at 2.65-2.7 µm range (MIR echelle orders from 221 to 224)</figcaption></figure>
## Example of one profile retrievals (average of orders 221, 222, 223):

- sensitivity to CO₂ absorption up to 180 km;

- sensitivity to very high water abundance (1-10 ppm at 110-120 km)

<figure><img src="image_10.png" /><figcaption>- MCD climatology; - MIR (this work); - NIR (Fedorova et al., 2020, SCIENCE)</figcaption></figure>
## Example of one profile retrievals (average of orders 221, 222, 223):

- sensitivity to CO₂ absorption up to 180 km;

- sensitivity to very high water abundance (1-10 ppm at 110-120 km)

<figure><img src="image_10.png" /><figcaption>- MCD climatology; - MIR (this work); - NIR (Fedorova et al., 2020, SCIENCE)</figcaption></figure>
Example of one profile retrievals (average of orders 221, 222, 223):

- sensitivity to CO₂ absorption up to 180 km;

- sensitivity to very high water abundance (1-10 ppm at 110-120 km)

<figure><img src="image_11.png" /></figure>
Example of one profile retrievals (average of orders 221, 222, 223):

- sensitivity to CO₂ absorption up to 180 km;

- sensitivity to very high water abundance (1-10 ppm at 110-120 km)

<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /></figure>

Orb 3820n2, Ls = 260.86, Lat = -53.6

<figure><img src="image_13.png" /></figure>
Profiles variability with Martian seasons in MY34 (Ls from 165)

Southern hemisphere (not full)

<figure><img src="image_12.png" /></figure>

<figure><img src="image_13.png" /></figure>

<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /></figure>
Profiles variability with Martian seasons in MY34 (Ls from 165)

Southern hemisphere (not full)

<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /></figure>

<figure><img src="image_16.png" /></figure>

<figure><img src="image_17.png" /></figure>

<figure><img src="image_18.png" /></figure>

<figure><img src="image_19.png" /></figure>

<figure><img src="image_20.png" /></figure>

<figure><img src="image_21.png" /></figure>

<figure><img src="image_22.png" /></figure>

<figure><img src="image_23.png" /></figure>

<figure><img src="image_24.png" /></figure>

<figure><img src="image_25.png" /></figure>
Summary

1) After recent transmission improvements for ACS-MIR spectra new temperature, CO2 and H2O density retrievals in the mesosphere/thermosphere are in good progress at 2.65-2.7 µm from 20 to 180 km of altitude;

2) Good coincidence with ACS-NIR (Fedorova et al., 2020) retrievals below 100 km;

3) Abundance of 1-10 ppm H₂O vmr at 110-120 km on perihelion Southern hemisphere, MY34.

4) Mesospheric+thermospheric comparison with IUVS/MAVEN and with GCM MY34 is needed.

5) ~350 calibrated occultations at Southern and Northern hemispheres are ready for farther retrievals in MY34 and MY35.
1) After recent transmission improvements for ACS-MIR spectra new temperature, CO₂ and H₂O density retrievals in the mesosphere/thermosphere are in good progress at 2.65-2.7 µm from 20 to 180 km of altitude;

2) Good coincidence with ACS-NIR (Fedorova et al., 2020) retrievals below 100 km;

3) Abundance of 1-10 ppm H₂O vmr at 110-120 km on perihelion Southern hemisphere, MY34.

4) Mesospheric+thermospheric comparison with IUVS/MAVEN and with GCM MY34 is needed.

5) ~350 calibrated occultations at Southern and Northern hemispheres are ready for farther retrievals in MY34 and MY35.