Thermal Structure and Aerosols in Mars’ Atmosphere From TIRVIM/ACS Onboard the ExoMars Trace Gas Orbiter: Validation of the Retrieval Algorithm

Abstract

The ESA-Roscosmos ExoMars Trace Gas Orbiter (TGO) was launched on 14 March 2016 and was successfully inserted into Mars' orbit in November 2016. After several orbit maneuvers including a 12-month aerobraking phase it reached its final, 400-km altitude and near-circular orbit on

Thermal Tides in the Martian Atmosphere Near Northern Summer Solstice Observed by ACS/TIRVIM Onboard TGO

“…It smooths the temperature vertical oscillations and therefore reduces the apparent daily anomaly. A comparison of these temperature profiles with those obtained from limb sounding by MCS (Kleinböhl et al, 2009) is presented in Guerlet et al (2022), where two sets of profiles show good agreement when vertical convolution is included. This is consistent with the model-observation agreement shown in this work.…”

“…It provided ∼1.7 million thermal infrared spectra with decent data quality. Guerlet et al (2022) presented a retrieval process based on optimal estimation theory that simultaneously retrieves atmospheric temperature profile, surface temperature, and the optical depths of dust and water ice clouds from these spectra. It builds initial guess of the temperatures using different parts of TIRVIM spectra (660-740 cm −1 for atmospheric and 1240-1290 cm −1 for surface temperature), and then it iterates with a radiative transfer model until the synthetic spectrum converges to the observed one or the maximal number (10) of iterations is reached.…”

EMIRS Observations of the Aphelion‐Season Mars Atmosphere

“…Thermal infrared spectroscopy has proven to be an effective means for characterizing the thermal structure, aerosol optical depth, and water vapor abundance in the lower atmosphere of Mars. Numerous examples include the spectrometers on‐board Mariner 9 (e.g., Conrath, 1975), Mars Global Surveyor (e.g., Conrath et al., 2000; Smith, 2002, 2004), Mars Exploration Rovers (e.g., Smith et al., 2006), Mars Express (e.g., Fouchet et al., 2007; Giuranna et al., 2021), and the ExoMars Trace Gas Orbiter (e.g., Guerlet et al., 2022). Multiband thermal infrared instruments on‐board the Viking Orbiter (e.g., Kieffer et al., 1977; Tamppari et al., 2003), Mars Odyssey (e.g., Smith, 2009, 2019), and Mars Reconnaissance Orbiter (e.g., Kleinböhl et al., 2009; McCleese et al., 2010) have provided additional important information.…”

Assimilation of Temperatures and Column Dust Opacities Measured by ExoMars TGO‐ACS‐TIRVIM During the MY34 Global Dust Storm

“…Guerlet et al. (2022) assume dust is well‐mixed in the lowest two scale heights and that its mixing ratio decreases linearly with log( p ) above. A quality flag is assigned to each CDOD observation, related to the sensitivity of the radiance to changes in dust load.…”

“…TGO's inclination is 74°, so there are no nadir observations poleward of this latitude in either hemisphere. The temperature profiles have a maximum sensitivity between 5 and 50 km above the ground, and a vertical resolution of about 10 km (Guerlet et al., 2022). The instrument was only sensitive to the true atmospheric temperatures at altitudes of 3–55 km, based on retrieval averaging kernel statistics (see Section 3.3).…”