Annotation of the results obtained in 2018
The following research were conducted in the reporting year. 1. A self-consistent photochemical model of the martian neutral and ion composition at 80–300 km that accounts for variations of the atmospheric composition with solar activity and water abundance at 80 km is presented. The model involves vertical transport by eddy, molecular, and ambipolar diffusion and both thermal and nonthermal escape of light species. The model predicts rather stable hydrogen escape of ≈1.9 × 108 cm−2 s−1 at 250 km during the most of the martian year beyond the perihelion period at LS=200–330°. The reaction between H2 and CO2+ remains here the key process that determines the hydrogen escape. Therefore the HST observation of D and the FUSE observation of H2 at LS=68 and 160°, respectively, do not need revision. Appearance of water in the thermosphere during the perihelion period results in significant increase in production of hydrogen by photolysis of water and reactions of its ions. Photolysis of H2O is the most effective at 160–180 nm and weakly depends on solar activity. Reactions of water ions start chiefly by charge exchange between CO2+ and H2O and end by recombination of H3O+. Both H2O photolysis and its ion reactions proceed near 100 km, and just a small part of the hydrogen production can escape. The calculated hydrogen escape at 250 km may be approximated by ΦH (cm−2 s−1)=1.6×108 +1.4×107 fH2O (ppm). Here fH2O is the H2O mixing ratio at 80 km that is reduced to 150 km by a factor of 5 by the photolysis and ion reactions. Therefore the observed high hydrogen escape up to 109 cm−2 s−1 requires the dayside-mean water abundances up to 60 ppm at 80 km that are within those observed by the SPICAM IR solar occultations. The significant H2O abundances do not deplete densities of HCO+ and are compatible with the MAVEN/NGIMS ion composition. The H Lyman-alpha observations reflect mostly the dayside-mean photochemistry, and our one-dimensional model may adequately respond to the problem. 2. A new implementation of the hydrological cycle scheme into a general circulation model of the Martian atmosphere is presented. The model includes a semi-Lagrangian transport scheme for water vapor and ice and accounts for microphysics of phase transitions between them. The hydrological scheme includes processes of saturation, nucleation, particle growth, sublimation, and sedimentation under the assumption of a variable size distribution. The scheme has been implemented into the Max Planck Institute Martian general circulation model and tested assuming monomodal and bimodal lognormal distributions of ice condensation nuclei. We present a comparison of the simulated annual variations, horizontal and vertical distributions of water vapor, and ice clouds with the available observations from instruments on board Mars orbiters. The accounting for bimodality of aerosol particle distribution improves the simulations of the annual hydrological cycle, including predicted ice clouds mass, opacity, number density, and particle radii. The increased number density and lower nucleation rates bring the simulated cloud opacities closer to observations. Simulations show a weak effect of the excess of small aerosol particles on the simulated water vapor distributions. 3. A portable, lightweight, and low-cost near-infrared laser heterodyne spectroradiometer (LHS) with a high spectral resolution of 0.0003 cm-1. Due to advanced capabilities provided by its ultra-high spectral resolution, such an instrument may be included into ground-based networks for monitoring greenhouse gases. Sample spectra of the atmospheric CO2 absorption lines obtained by direct Sun observations have allowed us to measure CO2 column abundance with a precision of 0.5% and to retrieve its vertical profiles. CO2 measurements were made in Moscow suburb near the industrial zone. 10 min of signal integration are chosen as an operation mode of the LHS, which lets to achieve SNR ~ 100. The inverse problem solution algorithm based on the principle of maximal entropy results in the evaluation of the CO2 atmospheric column with the accuracy comparable with the measurements of high resolution FTIR spectrometers. Due to the extreme spectral resolution, additional capabilities are appearing, including vertical profiling of greenhouse gas concentration and winds. Total column CO2 concetration was calculated to be XρCO2 = 402,3 ± 2,2 ppm. 4. We present a heterodyne spectrometers based on distributed feedback (DFB) quantum cascade lasers (QCL) and IR-photodetector (PD) as a mixer. Incoming signal, received by IR telescope and passed through the spectrometers input aperture, is mixed up with a local oscillator (LO) via a beam splitter and then is detected by PD. As a LO 7.8μm, 5.6μm and 10μm QCLs are utilized and as PD we implement TEC-cooled mercury-cadmium telluride (MCT) photodiode with 1 GHz intermediate frequency (IF) bandwidth. In order to achieve higher signal to noise ratio and lager IF range we also use superconductive hot electron bolometers (HEB) with helical antenna specially designed to provide effective absorption for 10 um radiation. The light is coupled to HEB with hemispherical Ge lense. The HEB IF bandwidth is relatively wide (≥ 3.5GHz) and its signal to noise ratio approaching to the quantum limit. We demonstrate performance of our setup with both types of PDs and characterization of our mid-IR HEB with QCLs (sensitivity, signal to noise ratio, bandwidth and antenna beam pattern). C2H2 absorption line spectrum around 7.8μ was measured during laboratory tests in the heterodyne mode with a 400oC black body which was used as the incoming signal and MCT photodiode as a detector. Developed mid-IR heterodyne spectrometer is planned to use for the solar occulatation observations of CO2 and methane total column concentrations. HEB antenna with lense beam pattern was measured in 2.25 μm, 7.8 μm and 10.4 μm range. It was calculated to be around 3 degree full width wavelenght independently. HEB efficiency was measured as a ratio of absorped emission power to incident power for the same wavelenghts and appered to be 0.01%, 0.03% и 0.2% respectevily. This results mean that spiral planar antenna does not work well in mid IR. Further investigations of HEB in mid-IR have to be conducted to clarify possibility of HEB application capabilities for heterodyning.

 

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Annotation of the results obtained in 2016
During the reported term theoretical models of planetary atmospheres have been updated in order to improve their capabilities in treatment and interpretation of planetary observations with ultra-high spectral resolution. The following results have been obtained: - The impact of iron chloride FeCl3 on the key processes in the Venus atmosphere has is studied. Based on model results on FeCl3 published earlier, including data on its coagulation with sulfuric acid, eddy transport and sedimentation, a model has been developed that results in the following insights: FeCl3 contributes in the blue and near UV albedo of Venus; FeCl3 contributes to the vertical profile of 0.1 and 0.3-micron cloud particles in the middle and lower cloud layer; this species also causes the lowering of the Venus atmosphere The model predicts the near-UV albedo of Venus close to the observed values taking into account the presence of FeCl3 in mass proportion to sulfuric acid 1:100. The model confirms that the presence of FeCl3 aerosol agrees with the observed spectral characteristics of the planet and accounts for the vertical distribution of mode 1 in the lower and middle cloud layers of Venus. Model results imply that FeCl3 delivery rate to the upper cloud layer is only ~0.01 of the value required to explain the observed UV albedo. Thus, iron chloride may with some confidence be considered as a component of the Venus atmosphere. - New results of the coupled general circulation model of the Martian atmosphere and thermosphere have been analyzed in terms of its capability of correct prediction of hydrogen escape processes, important for the Mars atmosphere's stability. Results of the 1D model implying eddy mixing argue that 3D models, being highly advanced in detailed description of transport processes, may not provide necessary accuracy for such a key parameter as hydrogen escape rate. - A new hydrological block of the Mars atmosphere general circulation model MAOAM (Martian Atmosphere: Observation and Modeling) has been developed. The model has spectral dynamical core and is capable of predicting wind velocity and temperature field using parameterizations typical for both terrestrial and Martian models. Hydrological block includes aerosol microphysics, advection, eddy mixing and sedimentation of ice and dust particles according to their mean size, as well as atmosphere-surface interactions. A good agreement of simulations with 10-year Mars climate monitoring is achieved. Model results are available online at http://mars.mipt.ru - The photochemical model molecular nitrogen production in the atmosphere of Titan has been updated, including isotopic fractionation in nitrogen predissociation, production of N(4S), N(2D), and N+ in dissociation and dissociative ionizatoin by solar extreme UV radiation, photoelectrons, magnetospheric charged particles and galactic cosmic rays. The model predicts 14N/15N = 57 in nitriles, which is consistent with the ration observed in HCN. Production and loss rates of molecular nitrogen has been estimated, resulting in the ratio 14N/15N = 129 at the moment of Solar System formation, which is close to the ratio 127±32 observed in ammonia ice in comets. This result confirms the hypothesis that the source of nitrogen in the Titan atmosphere may be ammonia delivered by comet collisions. Techniques for solution to inverse problems of planetary atmosphere sounding by ultra-high resolution ground-based observations were developed based on sample data from the heterodyne instrument. Based on Venus observations at McMath-Pierce solar telescope of Kitt-peak observatory (USA) with the infrared heterodyne spectrometer THIS near CO2 ro-vibrational line 963,26 cm-1 with extreme spectral resolution, temperature vertical profile has been retrieved in the range 60-110 km. The profile agrees with Fourier spectrometer data onboard Venera-15 and Venera-16 spacecraft, as well as with VIRA reference model. The retrievals show that provided signal-to-noise ratio ~300, thermal profiling accuracy is similar to that obtained by remote sensing from the planet's orbit. Based on the laboratory setup created in the framework of the project, key elements of heterodyne spectro-radiometer for astronomical purposes have been studied, with the following results: - Continuous frequency sweeping range of the quantum cascade laser (QCL) employed as a local oscillator in the model of heterodyne spectrometer has been studied. In the experiment laser radiation modulated by a sawtooth-shaped pump current and put into a cell filled by acetylene with the pressure 10 Torr and into a Fabry-Perot etalon. As the pump current modulation results in both intensity and frequency modulation of the laser radiation, direct absorption acetylene spectra were detected. The comparison of these spectra with model calculations based on HITRAN 2012 database resulted in highly accurate determination of the local oscillator frequency sweep. It worth noting that sweeping local oscillator in frequency is a novel technique in heterodyne detection in the thermal infrared range. This approach allows to enhance detected intermediate frequency range and to employ frequency stabilization methods based on reference absorption lines in order to suppress local oscillator drift. - Noise characteristics of the laboratory setup of mid-infrared heterodyne spectrometer have been studied, including relative intensity noise of the QCL, used as a local oscillator. - Heterodyne detection of the blackbody radiation with brightness temparature Т=400 оС has been demonstrated. Radiation from the blackbody was coupled with QCL beam at CaF plate and then transmitted to the detector. The signal at the detector was analyzed by a radio frequency spectral analyzer with the resolution of 10 MHz and IF range of 1 GHz. IF spectra with detector pumped by LO and LO coupled with bkackbody have been registered. The excess observed in all experiments after coupling blackbody radiation is interpreted as a heterodyne component. IF spectra with detector pumped by blackbody only, as well as dark signal have also been registered. The spectra coincide up to the detector noise level, wich confirms the heterodyne component detection.

 

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Annotation of the results obtained in 2017
Measurements of HBr in the atmosphere of Venus Observations of the Venusian atmosphere have been carried out in order to find presence of the HBr absorption lines in the 3.8 μm spectral range (2605.80 and 2606.20 cm-1). The high-resolution spectrometer (λ / Δλ ~ 104) CSHELL located at the IRTF telescope have been used for the measurements. 101 experimental spectra of the Venusian atmosphere have been studied. Estimated HBr concentration from these spectra varied from -8 to +5 ppb with -1.2 ppb average and standard deviation of 2.5 ppb. The negative values ​​of the HBr concentration indicate a systematic measurement error. The obtained upper limit of the HBr content in the upper cloud layer of Venus (at a height of 78 km from the surface) is ~ 1 ppb. The photochemical model of the Venusian atmosphere was refined with basic photochemical processes involving bromine. In accordance with the refined model, the photodissociation of HBr and its reactions with atomic hydrogen and oxygen determines the relative content of hydrogen bromide at altitudes of 70-80 km above the surface as about 300 times less than at altitudes below 60 km. The additional analysis of the observation data with taking into account the HBr profile calculated from the photochemical model estimated the maximum of the HBr content as 20-70 ppb and an optical depth of the aerosol for a height of 70 km and a wavelength of 3.84 μm as ~ 0.7. Thermodynamic calculations based on the chemical-kinetic model have shown that hydrogen bromide is the main bromine compound in the lower layers of the atmosphere of Venus. Calculation of N2, Ar, O2, and CO average annual concentrations in the atmosphere of Mars The data obtained by the quadrupole mass spectrometer of the MSL complex on board of the Mars rover Curiosity have been analyzed. For the N2, Ar, O2, and CO concentrations measured by the mass spectrometer in the Gale Crater, the normalizing coefficients were calculated. These coefficients allows determining the average annual global concentration of these gases on Mars. The normalizing coefficients were determined as p0pm, where p0 is the calculated average annual pressure value in the measurement area, pm- pressure during the measurement period. To estimate average pressure and its variations, the Mars Climate Database have been used as well as the first year of observations of the Viking 1 and 2 landing platforms. The normalization of the MSL data by the factor of p0pm gives the mean annual concentrations as (1.83 ± 0.03)% for N2, (1.86 ± 0.02)% for Ar, (1.56 ± 0.06) * 10-3 for O2, 673 ± 2.6 ppm for CO. The calculated O2 concentration is in a good agreement with measurements of the Herschel Observatory in the 773.84 GHz band, ground observations and photochemical models. The CO concentration is consistent with the measurements of the CRISM on the MRO. In this way, the obtained data can be used as standard values ​​for validating data from satellites and refining the models of general circulation. Critical analysis of the New Horizons mission results The recent results of the New Horizons mission are discussed in detail. Some inconsistencies in the observation of Pluto’s atmosphere and predictions of the existing models are highlighted. In particular, the problem with the inconsistency of the temperature profile of Pluto at altitudes of more than 300 km is described. According to the data of the NH, obtained by the solar eclipse method in the UV range, the temperature of the atmosphere rises from the surface to 30 km from 39 K to 107 K, then linearly decreases to 65-68 K at an altitude of 300 km and to altitudes of 1,700 km remains unchanged. This observation does not correspond to the idea of ​​adiabatic cooling of the Pluto thermosphere. This contradiction can potentially be solved by adding cooling to the model of radiative balance due to the thermodynamically equilibrium radiation of H2O and HCN molecules. Another problem of the Pluto’s atmosphere models is the discrepancy between the prediction of the amount of generated water vapor and observed data. This may be due to the photolysis of H2O, which was not taken into account in the models. Also, a significant discrepancy was found in calculating the surface area of ​​aerosol particles in the Pluto atmosphere from the data of the LORRI and MVIC instruments and existing models, as well as the cohesion and condensation coefficients calculated for these data for C2H2x and HCN. Disulfur dioxide and its near-UV absorption in the photochemical model of Venus atmosphere Calculations of production and photolysis of the S2O2 isomers by Frandsen et al. (2016) were included into the photochemical model of Venus atmosphere. The major photochemical effect is caused by SO recycling in the termolecular association of S2O2 followed by its photolysis, while it was lost in these processes in the previous model. Consequences of this change to balances of sulfur species are discussed. The basic model and four versions with small deviations in eddy diffusion and SO2 abundance at the lower boundary are calculated. The models agree with the observed abundances of CO, H2O, SO2 , SO, OCS and their variations; some differences are discussed. Volcanism is not required to explain variations of sulfur species that may be induced by minor changes in atmospheric dynamics. Three methods are applied to evaluate S2O2 abundance sufficient for the NUV absorption on Venus, and the derived S2O2 exceeds the model value by two orders of magnitude. Therefore our model does not support S2O2 as a significant NUV absorber. Simulations of the Mars water cycle A new model of the hydrological cycle in the atmosphere of Mars and its application in the Martian general atmospheric circulation model MAOAM (Martian Atmosphere: Observation and Modeling) are presented. The hydrological scheme includes a semi-Lagrangian scheme for the transfer of water vapor and ice particles and a microphysical model for calculating phase transitions between them. The microphysical scheme uses the approach of Montmessin et al. [2002, 2004] and Navarro et al. [2014], but differs from the listed models by more precise microphysical parametrizations. The simulation was performed using a fixed dust distribution that represented the seasonal and spatial evolution of atmospheric aerosol based on the Mars Global Surveyor (MGS-TES) infrared spectrometer and the Mars Express (MEX-PFS) Fourier spectrometer with the removal of global dust storms. The number of particles (which are considered as the condensation nuclei in the model) of a certain size (divided into bins) was calculated using a bimodal logarithmic distribution of dust. Unlike previous works [for example, Montmessin et al., 2002], we used a distribution involving much smaller particles and a ratio of peak density to 103-104, which is confirmed by observations in certain seasons [Fedorova et al., 2014]. The hydrological scheme also includes saturation, nucleation, particle growth, sublimation and sedimentation depending on the mean particle radius and surface microphysics, diffusion and advection of vapor and ice particles. The simulated annual oscillations, horizontal and vertical distribution of water vapor and ice clouds were compared with SPICAM data (Mars Express spectrometer), MGS-TES and CRISM. Simulation shows the total amount of steam in the summer season at the north pole with a maximum of about 50-70 precipitated microns, which is close to SPICAM observations. Comparison of simulation results with SPICAM profiles shows a good reproduction of water vapor in the middle atmosphere at altitudes 40-60 km. The model also predicts overly dense clouds in the north during the perihelion period, which could not largely be measured by TES, and does not tend to form clouds over the northern polar cap during the aphelion season, according to observations. The simulated belt of clouds ACB (clouds of water ice over the equator during the seasons Ls ~ 40◦ - 110◦) is in good agreement with the observations of CRISM. Development of the MIR heterodyne spectrometer for atmospheric studies Development of the high resolution (λ / Δλ ~ 108) middle infrared (MIR) range heterodyne spectrometer for the the atmospheric studies continued in this year. The spectrometer is designed to fully resolve single spectral line of molecules in MIR range in atmospheres of planets of solar system with ground based meter-class telescopes. The spectrometer utilize the set of quantum cascade lasers (QCLs) as local oscillator and hot electron bolometer (HEB) or high bandwidth MCT photodiode as mixer. Custom QCL package have been developed, which allows QCL operation in wide temperature range (-30 - 40 oC) and simplifies its optical alignment. Galvo scanner with gold-plated mirror and two reference blackbodies have been added to the setup to perform simultaneously calibration of the heterodyne signal in terms of brightness temperature. The noise temperature (Tnoise) of the spectrometer with MCT photodetector have been studied using Y-factor method in 7.8 μm spectral range. The measured value of Tnoise was about 18000 K which is still far from the quantum limit (~1800 K). Detailed analysis of noise sources of different nature allows us to determine the reason of such inconsistency, which is due to large value MCT photodetector noise. Application of low noise and wide bandwidth HEB will potentially make possible quantum limit performance of the spectrometer. Now we are upgrading our spectrometer with such kind of photomixer. In order to examine spectrometer performance heterodyne signal from laboratory blackbody with temperature of 400oC have been recorded. The mean signal value was close to our estimation taking into account MCT photodetector noise. Finally,. we have observed spectrum of the Doppler broadened absorption line of acetylene in heterodyne mode in 7.8 μm spectral range, which was acquired by our spectrometer by passing blackbody radiation through 4 cm gas cell filled with acetylene at pressure about 5 torr and then mixed with local oscillator radiation on СaF2 plate. Spectrum have been recorded with 10 MHz resolution at the IF range of ~700 MHz and was close to the HITRAN-2012 based simulation. For astronomical observations superconducting hot-electron bolometers (HEB) seem to be most suitable heterodyne detectors in mid IR range in terms of noises and bandwidth. The current-voltage characteristics of a HEB with spiral planar antenna were measured for several black body temperatures which irradiated HEB for determining optimal operating regime. In order to simplify optical scheme of heterodyne spectrometer, hollow waveguides are planned to be used for LO and signal emission delivery to the mixer. For this reason a single-mode operation regime of Ag coated hollow waveguide was investigated. A 7.78 μm quantum-cascade laser emission was coupled with hollow waveguide with an inner-wall coating of Ag, with an internal diameter of 1 mm and an external one of 1.6 mm is studied. The numerical aperture of the waveguide for single-mode radiation propagation was measured to be 0.03. Potential capability of heterodyne detection of water vapor above the Venus cloud layer at altitudes 60 to 90 km has been estimated based on the model of the planet's outgoing thermal radiation within the intervals 1280 - 1295 см-1 and 1852 - 1860 см-1. With the instrument's signal-to-noise ratio S/N=100 it is possible to detect water vapor at 2 ± 1ppm level, with S/N=300 - at 0.4 ± 0.2ppm accordingly. Thermal profile may be retrieved with the accuracy of 1.5% for Venus atmosphere at 60-90 км and 2.5% for Mars atmosphere at 0-40 км. The vertical expected of the thermal profile retrievals is about 5 km for both Venus and Mars.

 

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