Sensitivity study of the reduced electric field and geometry of observation on the thermal infrared signature of a sprite

International audienceSince their first recording in 1989, effects of sprites on the atmospheric composition have become an open and important question. The lack of suitable infrared experimental data is a shortcoming that hampers our understanding of the physical and chemical effects involved during a sprite. HALESIS (High-Altitude Luminous Events Studied by Infrared Spectro-imagery) is a future experiment dedicated to the measurement of the atmospheric perturbation induced by a transient luminous event in the minutes following its occurrence, from a stratospheric balloon flying at an altitude of 25 km to 40 km. The aim of this work is to describe the population of electrons and vibrational levels of N2 and CO2 following a sprite for different reduced electric fields. Then, the thermal infrared emission intensity and duration are evaluated considering the radiative emissions of vibrational N2 and CO2 in the 500-2500 cm-1 spectral range for different lines-of-sight. The radiance signature is computed for observers located on the ground, plane, stratospheric balloon and satellite. To do that, we first built an input atmospheric composition model from the Whole Atmosphere Community Climate Model (WACCM, Marsh et al., 2013). The kinetic model of sprite comes from Gordillo-Vazquez, 2008. We updated it with vibrational processes of Parra-Rojas, 2015. Then, we computed the time-dependent concentrations of the species solving the kinetics with ZDPlaskin (Pancheshnyi et al., 2008). Finally, we obtained the disturbed atmospheric radiance spectra using the Line-By-Line Radiative Transfer Model (LBLRTM, Clough et al., 2005) code. We will conclude that the maximum increase of radiance stands between 900-1100 and 2200-2400 cm-1 and could be significant for an airborne observer and a satellite during several tens of seconds after the visible flash is over

Sensitivity study of the reduced electric field and geometry of observation on the thermal infrared signature of a sprite

International audienceSince their first recording in 1989, effects of sprites on the atmospheric composition have become an open and important question. The lack of suitable infrared experimental data is a shortcoming that hampers our understanding of the physical and chemical effects involved during a sprite. HALESIS (High-Altitude Luminous Events Studied by Infrared Spectro-imagery) is a future experiment dedicated to the measurement of the atmospheric perturbation induced by a transient luminous event in the minutes following its occurrence, from a stratospheric balloon flying at an altitude of 25 km to 40 km. The aim of this work is to describe the population of electrons and vibrational levels of N2 and CO2 following a sprite for different reduced electric fields. Then, the thermal infrared emission intensity and duration are evaluated considering the radiative emissions of vibrational N2 and CO2 in the 500-2500 cm-1 spectral range for different lines-of-sight. The radiance signature is computed for observers located on the ground, plane, stratospheric balloon and satellite. To do that, we first built an input atmospheric composition model from the Whole Atmosphere Community Climate Model (WACCM, Marsh et al., 2013). The kinetic model of sprite comes from Gordillo-Vazquez, 2008. We updated it with vibrational processes of Parra-Rojas, 2015. Then, we computed the time-dependent concentrations of the species solving the kinetics with ZDPlaskin (Pancheshnyi et al., 2008). Finally, we obtained the disturbed atmospheric radiance spectra using the Line-By-Line Radiative Transfer Model (LBLRTM, Clough et al., 2005) code. We will conclude that the maximum increase of radiance stands between 900-1100 and 2200-2400 cm-1 and could be significant for an airborne observer and a satellite during several tens of seconds after the visible flash is over

Sensitivity study of the reduced electric field and geometry of observation on the thermal infrared signature of a sprite

International audienceSince their first recording in 1989, effects of sprites on the atmospheric composition have become an open and important question. The lack of suitable infrared experimental data is a shortcoming that hampers our understanding of the physical and chemical effects involved during a sprite. HALESIS (High-Altitude Luminous Events Studied by Infrared Spectro-imagery) is a future experiment dedicated to the measurement of the atmospheric perturbation induced by a transient luminous event in the minutes following its occurrence, from a stratospheric balloon flying at an altitude of 25 km to 40 km. The aim of this work is to describe the population of electrons and vibrational levels of N2 and CO2 following a sprite for different reduced electric fields. Then, the thermal infrared emission intensity and duration are evaluated considering the radiative emissions of vibrational N2 and CO2 in the 500-2500 cm-1 spectral range for different lines-of-sight. The radiance signature is computed for observers located on the ground, plane, stratospheric balloon and satellite. To do that, we first built an input atmospheric composition model from the Whole Atmosphere Community Climate Model (WACCM, Marsh et al., 2013). The kinetic model of sprite comes from Gordillo-Vazquez, 2008. We updated it with vibrational processes of Parra-Rojas, 2015. Then, we computed the time-dependent concentrations of the species solving the kinetics with ZDPlaskin (Pancheshnyi et al., 2008). Finally, we obtained the disturbed atmospheric radiance spectra using the Line-By-Line Radiative Transfer Model (LBLRTM, Clough et al., 2005) code. We will conclude that the maximum increase of radiance stands between 900-1100 and 2200-2400 cm-1 and could be significant for an airborne observer and a satellite during several tens of seconds after the visible flash is over

Simulation of the infrared signature of transient luminous events in the middle atmosphere for a limb line of sight

International audienceTransient Luminous Events (TLE) are electrical and optical events which occurs above thunderstorms. Visual signatures are reported since the beginning of the 20th century but the first picture is accidentally recorded from a television camera in 1989. Their occurrence is closely linked with the lightning activity below thunderstorms. TLEs are observed from the base of the stratosphere to the thermosphere (15 - 110 km). They are a very brief phenomenon which lasts from 1 to 300 milliseconds. At a worldwide scale, four TLEs occur each minute. The energy deposition, about some tenth of megajoules, is able to ionize, dissociate and excite the molecules of the atmosphere. Atmospheric discharges in the troposphere are important sources of NO and NO2. TLEs might have the same effects at higher altitudes, in the stratosphere. NOx then can affect the concentration of O3 and OH. Consequently, TLEs could be locally important contributors to the chemical budget of the middle atmosphere. The perturbation of the atmospheric chemistry induced by TLEs has the consequence to locally modify the radiations in the infrared during the minutes following the event. The interest of studying the infrared signature of a TLE is twofold. For the atmospheric sciences it allows to link the perturbed composition to the resulting infrared spectrum. Then, some Defense systems like detection and guiding devices are equipped with airborne infrared sensors so that the TLE infrared signature might disturb them. We want to obtain a quantitative and kinetic evaluation of the infrared signature of the atmosphere locally perturbed by a TLE. In order to do so we must model three phenomena. 1) The plasma/chemistry coupling, which describes how the different energetic levels of atmospheric molecules are populated by the energetic deposition of the TLE. This step lasts the time of the lightning itself. 2) The chemical kinetics which describes how these populations will evolve in the following minutes. 3) The radiative transfer which describes the propagation of infrared radiations from the disturbed area to an instrument in a limb line of sight. These three steps must be considered under the assumption of the Non Local Thermodynamic Equilibrium: where TLEs occurs, above 20 km, the populations of the energetic levels are not well described with a Maxwell-Boltzmann distribution. We must consider each excited level as a single species. In this poster we will present our strategy to simulate the signature of a TLE for different limb line of sights and how we expect to retrieve the atmospheric composition by remote sensing measurement spectra in the framework of the High Altitude Luminous Events Studied by Infrared Spectro-imagery (HALESIS) project and to quantify in which way a TLE can disturb military airborne sensors

Simulation of the infrared signature of transient luminous events in the middle atmosphere for a limb line of sight

International audienceWe study the effects of Sprites on the atmospheric chemistry and radiances. We use the code SAMM2 to model the excitation of the ambient atmosphere. Then we explain how we will include a sprite model

CO₂ thermal infrared signature following a sprite event in the mesosphere

International audienceSprites are a potential thermal infrared radiation source in the stratosphere and mesosphere through molecular vibrational excitation. We developed a plasma‐chemical model to compute the vibrational kinetics induced by a sprite streamer in the 40‐70 km altitude range until several tens of seconds after the visible flash is over. Then, we computed the consecutive time‐dependent thermal infrared spectra that could be observed from the stratosphere (from a balloon platform), high troposphere (from an aircraft) and low troposphere (aircraft or altitude observatory) using a non‐local thermodynamic equilibrium radiative transfer model. Our simulations predict a strong production of CO2 in the (001) vibrational level which lasts at least 40 seconds before falling to background concentrations. This leads to enhanced emissions in the long wavelength infrared, around 1000 cm‐1, and mid wavelength infrared, around 2300 cm‐1. The maximum sprite infrared signatures (sprite spectra minus background spectra) reach several 10‐7 W/sr/cm2/cm‐1 after propagation through the mesosphere and stratosphere, to an observer located at 20‐40 km of altitude. This maximum signal is about one order of magnitude lower if propagated until the troposphere. From the two spectral bands, the 1000 cm‐1 one could be detected more easily than the 2300 cm‐1 one, which is more affected by atmospheric absorption (CO2 self‐trapping at all altitudes, and H2O, mostly in the troposphere). With a sufficiently sensitive instrumentation, mounted in an open stratospheric balloon platform for example, the 1000 cm‐1 band could be detected from 20 – 40 km of altitude

Evaluation of the infrared signature of auroras from a stratospheric balloon

International audienceHALESIS (High-Altitude Luminous Events Studied by Infrared Spectro-imagery) is a future experiment dedicated to the measurement of the atmospheric perturbation induced by transient luminous events in the minutes following their occurrence. The recordings will be done from a stratospheric balloon flying at an altitude of 25 km to 40 km. These electrical and optical events occur above thunderstorms between 20 and 100 km of altitude. As a diversification purpose of the HALESIS experiment, we want to investigate the possibility to observe another kind of atmospheric luminous events: auroras. Auroras are optical phenomena caused by the collision of solar particle with high-atmosphere molecules and ions. They are known for their typical visible emissions, but the excited species could enhance the atmospheric radiances in the short and mid wavelength infrared too. The objective of this work is to evaluate the infrared radiances in the 2000-4000 cm-1 spectral range for typical cases of auroras that should be observed by an instrument located in the stratosphere (HALESIS setup). The vibrational populations of CO2, NO and NO+ during an aurora are computed together with the resulting infrared radiative emissions. Then, the signal is propagated through the atmosphere to the observer. The computations are done using the code Sharc And MODTRAN Merged, second release (SAMM2, Dothe et al., 2009). We will conclude that the radiance enhancement caused by CO2 is not significant. Those of NO and NO+ can reach 10-10 W/cm2/sr/cm-1. Due to the very low amplitude of this signature, it will be necessary to use an appropriate strategy of spatial and temporal co-averaging of spectra to detect it. This could be possible considering the large dimension of this phenomena and its long duration. The HALESIS experiment will be done in coordination with ATISE (Auroral Thermospheric and Ionospheric Spectrometer Experiment) ground or balloon demonstration experiment. This will allow coordinating the infrared emissions studies with the visible ones

Evaluation of the infrared signature of auroras from a stratospheric balloon

International audienceHALESIS (High-Altitude Luminous Events Studied by Infrared Spectro-imagery) is a future experiment dedicated to the measurement of the atmospheric perturbation induced by transient luminous events in the minutes following their occurrence. The recordings will be done from a stratospheric balloon flying at an altitude of 25 km to 40 km. These electrical and optical events occur above thunderstorms between 20 and 100 km of altitude. As a diversification purpose of the HALESIS experiment, we want to investigate the possibility to observe another kind of atmospheric luminous events: auroras. Auroras are optical phenomena caused by the collision of solar particle with high-atmosphere molecules and ions. They are known for their typical visible emissions, but the excited species could enhance the atmospheric radiances in the short and mid wavelength infrared too. The objective of this work is to evaluate the infrared radiances in the 2000-4000 cm-1 spectral range for typical cases of auroras that should be observed by an instrument located in the stratosphere (HALESIS setup). The vibrational populations of CO2, NO and NO+ during an aurora are computed together with the resulting infrared radiative emissions. Then, the signal is propagated through the atmosphere to the observer. The computations are done using the code Sharc And MODTRAN Merged, second release (SAMM2, Dothe et al., 2009). We will conclude that the radiance enhancement caused by CO2 is not significant. Those of NO and NO+ can reach 10-10 W/cm2/sr/cm-1. Due to the very low amplitude of this signature, it will be necessary to use an appropriate strategy of spatial and temporal co-averaging of spectra to detect it. This could be possible considering the large dimension of this phenomena and its long duration. The HALESIS experiment will be done in coordination with ATISE (Auroral Thermospheric and Ionospheric Spectrometer Experiment) ground or balloon demonstration experiment. This will allow coordinating the infrared emissions studies with the visible ones

Assessing Greenhouse Gas Monitoring Capabilities Using SolAtmos End-to-End Simulator: Application to the Uvsq-Sat NG Mission

International audienceMonitoring atmospheric concentrations of greenhouse gases (GHGs) like carbon diox- ide and methane in near real time and with good spatial resolution is crucial for enhancing our understanding of the sources and sinks of these gases. A novel approach can be proposed using a con- stellation of small satellites equipped with miniaturized spectrometers having a spectral resolution of a few nanometers. The objective of this study is to describe expected results that can be obtained with a single satellite named Uvsq-Sat NG. The SolAtmos end-to-end simulator and its three tools (IRIS, OptiSpectra, and GHGRetrieval) were developed to evaluate the performance of the spectrometer of the Uvsq-Sat NG mission, which focuses on measuring the main GHGs. The IRIS tool was imple- mented to provide Top-Of-Atmosphere (TOA) spectral radiances. Four scenes were analyzed (pine forest, deciduous forest, ocean, snow) combined with different aerosol types (continental, desert, maritime, urban). Simulated radiance spectra were calculated based on the wavelength ranges of the Uvsq-Sat NG, which spans from 1200 to 2000 nm. The OptiSpectra tool was used to determine optimal observational settings for the spectrometer, including Signal-to-Noise Ratio (SNR) and integration time. Data derived from IRIS and OptiSpectra served as input for our GHGRetrieval simulation tool, developed to provide greenhouse gas concentrations. The Levenberg–Marquardt algorithm was applied iteratively to ne-tune gas concentrations and model inputs, aligning observed transmittance functions with simulated ones under given environmental conditions. To estimate gas concentrations (CO2 , CH4 , O2 , H2 O) and their uncertainties, the Monte Carlo method was used. Based on this analysis, this study demonstrates that a miniaturized spectrometer onboard Uvsq-Sat NG is capable of observing different scenes by adjusting its integration time according to the wavelength. The expected precision for each measurement is of the order of a few ppm for carbon dioxide and less than 25 ppb for methane