This paper presents a method for solving the inverse problem of thermal sounding using calibrated data from the ACS TIRVIM experiment on board the ExoMars Trace Gas Orbiter . The 1.7–17 µm range TIRVIM Fourier spectrometer as part of the ACS instrument complex aboard the ExoMars TGO operates in the nadir and solar occultation modes in orbit around Mars. The main scientific goal of TIRVIM in the nadir observation mode is the long-term constant monitoring of the thermal structure of the Martian atmosphere and the general content of aerosols and water vapor from measurements in the range of 5–16.7 µm (600–2000 cm –1 ). To process the TIRVIM nadir measurements, an algorithm was developed, allowing the retrieval of the vertical temperature profile from the surface to 60 km, the surface temperature, and the general content of dust and water ice in the atmosphere from the TIRVIM spectrum in the range of 600–1250 cm –1 , as well as the water vapor column abundance according to measurements in the range of 1250–1830 cm –1 . The processing method widely uses the achievements of previous similar experiments, taking into account the features of the TIRVIM spectra. Using the developed method 2.28 × 10 6 spectra obtained by TIRVIM in nadir by regular measurements, were processed with retrieval of the thermal structure up to 60 km altitude and the aerosol content in the atmosphere as well as additional 2.3 × 10 5 specially averaged TIRVIM spectra, were processed with retrieval of the water vapor column abundancein the Martian atmosphere.

This research studies the O 2 (a 1 Δ g ) nightglow distribution in 1.27 μm to understand the dynamics of the atmosphere of Venus. Several factors were considered in the retrieval process, such as thermal emission of the lower atmosphere, reflection by the clouds. Results show deviation from SS-AS circulation mode: the area where horizontal flows from the dayside converge and where oxygen recombines and emits shifts from the midnight to 22–23 hours local time. This shift is caused by solar-induced thermal tide on Venus nightside. Some conclusions about the upper mesosphere dynamics are also presented.

Hydrogen chloride gas was recently discovered in the atmosphere of Mars during southern summer seasons. Its connection with potential chlorine reservoirs and the related atmospheric chemistry is now of particular interest and actively studied. Measurements by the Atmospheric Chemistry Suite mid-infrared channel (ACS MIR) on the ExoMars Trace Gas Orbiter allow us to measure the ratio of hydrogen chloride two stable isotopologues, H35Cl and H37Cl. This work describes the observation, processing technique, and derived values for the chloride isotope ratio. Unlike other volatiles in the Martian atmosphere, because it is enriched with heavier isotopes, theδ37Cl is measured to be − 7 ± 20°, which is almost indistinguishable from the terrestrial ratio for chlorine. This value agrees with available measurements of the surface materials on Mars. We conclude that chlorine in observed HCl likely originates from dust and is not involved in any long-term, surface-atmosphere cycle.

ACS (the Atmospheric Chemistry Suite) [1] instrument onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter (TGO) is dedicated to measurements of the Martian atmosphere, in particular implementing the solar occultation technique for sensitive measurement of trace atmospheric gases TGO has started science observations from April 2018 (Ls=162°; MY34), and has observed two major perihelion dust events, the global dust storm 2018A in June till August 2018, and the regional storm in the beginning of 2019. Here we will give a status update of the ACS results, obtained from the data collected during the first year of observations in the orbit of Mars.

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm −1 . TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described.

The dependences of the spread function of a Fourier spectrometer on the wavenumber, maximum optical path difference, size of the field of view, and angle between the axes of the field of view and an interferometer are considered in this article. (C) 2018 Optical Society of America.

The design and performance features of an IR Fourier-transform spectrometer for studying the Martial atmosphere in the spectrum range of 600–5500 cm–1 during the ExoMars-2016 mission are described. The obtained spectral resolution is in agreement with the theoretical value (0.2 cm–1); the threshold of the instrument sensitivity is approximately 0.1 mW/(m2 sr cm–1).

ACS is a set of spectrometers for atmospheric studies (Atmospheric Chemistry Suite). It is one of the Russian instruments for the Trace Gas Orbiter (TGO) of the Russian-European “ExoMars” program. The purpose of the experiment is to study the Martian atmosphere by means of two observations regimes: sensitive trace gases measurements in solar occultations and by monitoring the atmospheric state during nadir observations. The experiment will allow us to approach global problems of Mars research such as current volcanism, and the modern climate status and its evolution. Also, the experiment is intended to solve the mystery of methane presence in the Martian atmosphere. Spectrometers of the ACS set cover the spectral range from the near IR-range (0.7 μm) to the thermal IR-range (17 μm) with spectral resolution λ/Δλ reaching 50000. The ACS instrument consists of three independent IR spectrometers and an electronics module, all integrated in a single unit with common mechanical, electrical and thermal interfaces. The article gives an overview of scientific tasks and presents the concept of the experiment.

An AOST Fourier spectrometer of the Phobos-Soil project is intended for studying Mars and Phobos by means of measurements of IR radiation spectra of the Martian surface and atmosphere, the Phobos surface, and the spectrum of solar radiation passing through the Martian atmosphere on its limb. The main scientific problems to be solved with the spectrometer on Mars are measurements of methane content, search for minor constituents, and study of diurnal variations in the temperature and atmospheric aerosol. The spectrometer will also study the Martian and Phobos surface both remotely and after landing. The spectral range of the instrument is 2.5–25 μm, the best spectral resolution (without apodization) is 0.6 cm −1 , and the instantaneous field of view is 2.5°. The recording time of one spectrum is equal to 5 s in solar observations and 50 s in observations of Mars and Phobos. The instrument has self-thermal stabilization and two-axis pointing systems, as well as a built-in radiation source for flight calibration. The spectrometer mass is 4 kg, and power consumption is up to 13 W. Scientific problems, measurement modes, and, briefly, engineering implementation of the experiment are discussed in this work.

An overview of results obtained in the field of planetary atmosphere studies in Russia in 2007–2010 prepared by the Commission on Planetary Atmospheres of the National Geophysical Committee for the National Report on Meteorology and Atmospheric Sciences to the XXV General Assembly of the International Union of Geodesy and Geophysics (Melbourne, 28 June–7 July 2011) [1, 2] is presented.

Spread functions are calculated to show how they depend on dimensionless criteria for adjusted and misadjusted Fourier spectrometers with Michelson interferometers. (C) 2011 Optical Society of America.

This paper describes a device for separating a laser radiation beam in the reference channel of a Fourier spectrometer into two beams, shifted in phase by pi/2. This make it possible to constantly monitor the sign of the rate of change of the optical path difference. A plane-parallel glass plate tilted at a definite adjustable angle and overlapping half the laser radiation beam is mounted in one arm of the interferometer. (C) 2011 Optical Society of America.

The paper is devoted to studies of the oxygen 1.27 mu m emission on the Venus nightside using nadir measurements with the imaging spectrometer VIRTIS. A map of the emission distribution in coordinates latitude-local time is drawn for the southern hemisphere, equatorial region, and low latitudes of the northern hemisphere on the basis of observations in the period from June 2006 to January 2008 (more than 600 runs). As it has been noted before, strong spatial and time variations of the emission were observed. Two maxima of the emission are found: the first one (expected) is observed near the antisolar point, and the second one (near 23:00 LT) is seen at latitudes of 30A degrees-60A degrees in the southern hemisphere. The average value of the emission intensity measured according to the nadir data is 1.0 +/- 0.4 MR. The emission with the intensity exceeding the average one by a factor of 2-3 was detected at different times almost over the entire nightside of the southern hemisphere.

The paper is devoted to studies of the oxygen 1.27 μm emission on the Venus nightside using nadir measurements with the imaging spectrometer VIRTIS. A map of the emission distribution in coordinates latitude-local time is drawn for the southern hemisphere, equatorial region, and low latitudes of the northern hemisphere on the basis of observations in the period from June 2006 to January 2008 (more than 600 runs). As it has been noted before, strong spatial and time variations of the emission were observed. Two maxima of the emission are found: the first one (expected) is observed near the antisolar point, and the second one (near 23:00 LT) is seen at latitudes of 30°–60° in the southern hemisphere. The average value of the emission intensity measured according to the nadir data is 1.0 ± 0.4 MR. The emission with the intensity exceeding the average one by a factor of 2–3 was detected at different times almost over the entire nightside of the southern hemisphere.

The AOST Fourier spectrometer being developed for the Phobos-Soil project is intended for remote probing in the 2.5-25-mu m region. This spectral region includes not only reflected and transmitted solar radiation, but also the intrinsic thermal radiation of the celestial body being studied. The maximum spectral resolution, taking into account apodization, is 0.9 cm(-1), and the field-of-view angle is 2.5 degrees. The device has its own thermal-stabilization and two-axis guidance systems, as well as an absolute-blackbody simulator for calibration. The time to record one interferogram ranges from 5 to 50 sec. The mass of the device is 4 kg, and its power requirement is as much as 10 W. (C) 2009 Optical Society of America.