References of "Stiepen, Arnaud"
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See detailA chemical survey of exoplanets with ARIEL
Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul et al

in Experimental Astronomy (2018)

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the ... [more ▼]

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet's birth, and evolution. ARIEL was conceived to observe a large number ( 1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25-7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10-100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H[SUB]2[/SUB]O, CO[SUB]2[/SUB], CH[SUB]4[/SUB] NH[SUB]3[/SUB], HCN, H[SUB]2[/SUB]S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed - using conservative estimates of mission performance and a full model of all significant noise sources in the measurement - using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL - in line with the stated mission objectives - will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives. [less ▲]

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See detailNOMAD, an Integrated Suite of Three Spectrometers for the ExoMars Trace Gas Mission: Technical Description, Science Objectives and Expected Performance
Vandaele, A. C.; Lopez-Moreno, J.-J.; Patel, M. R. et al

in Space Science Reviews (2018), 214

The NOMAD ("Nadir and Occultation for MArs Discovery") spectrometer suite on board the ExoMars Trace Gas Orbiter (TGO) has been designed to investigate the composition of Mars' atmosphere, with a ... [more ▼]

The NOMAD ("Nadir and Occultation for MArs Discovery") spectrometer suite on board the ExoMars Trace Gas Orbiter (TGO) has been designed to investigate the composition of Mars' atmosphere, with a particular focus on trace gases, clouds and dust. The detection sensitivity for trace gases is considerably improved compared to previous Mars missions, compliant with the science objectives of the TGO mission. This will allow for a major leap in our knowledge and understanding of the Martian atmospheric composition and the related physical and chemical processes. The instrument is a combination of three spectrometers, covering a spectral range from the UV to the mid-IR, and can perform solar occultation, nadir and limb observations. In this paper, we present the science objectives of the instrument and explain the technical principles of the three spectrometers. We also discuss the expected performance of the instrument in terms of spatial and temporal coverage and detection sensitivity. [less ▲]

Detailed reference viewed: 29 (11 ULiège)
See detailMars Nitric Oxide Nightglow and Its
Stiepen, Arnaud ULiege; MAVEN IUVS team; LMD-MGCM team

Conference (2018, July)

Detailed reference viewed: 12 (1 ULiège)
See detailHighlights from Imaging Ultraviolet Spectroscopy of the Mars Atmosphere with MAVEN/IUVS
Stiepen, Arnaud ULiege; Chaffin; MAVEN IUVS team

Conference (2018, July)

Detailed reference viewed: 23 (1 ULiège)
See detailGlobal aurora on Mars during the September 2017 Space Weather Event
Schneider; MAVEN IUVS team; Particle and Fields MAVEN team et al

Conference (2018, April)

Detailed reference viewed: 18 (1 ULiège)
See detailMAVEN IUVS Remote Sensing Highlights Relevant to Upcoming TGO Observations
Chaffin, M.; Schneider, N. M.; Deighan, J. et al

in From Mars Express to ExoMars (2018, February 01)

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Detailed reference viewed: 14 (2 ULiège)
See detail14 years of Mars' atmosphere monitoring by SPICAM on Mars Express
Lacombe, G.; Montmessin, F.; Korablev, O. et al

in From Mars Express to ExoMars (2018, February 01)

Not Available

Detailed reference viewed: 20 (6 ULiège)
See detailThree types of aurora on Mars
Schneider, N.; Jain, S.; Deighan, J. et al

Conference (2017, December)

Observations by the Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft have identified three types of aurora on Mars, each profoundly different from comparable types on Earth and other ... [more ▼]

Observations by the Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft have identified three types of aurora on Mars, each profoundly different from comparable types on Earth and other planets. The primary reason for these differences is Mars’ lack of a global magnetic field and presence of localized crustral magnetic fields primarily in the southern hemisphere. IUVS is MAVEN’s remote sensing instrument for study of the Mars atmosphere. The instrument records spatially-resolved spectra in the far-UV (110-190 nm) and Mid-UV (180-340 nm). By virtue of an internal scan mirror and a gimbaled instrument platform, IUVS obtains useful spectra on Mars with >50% duty cycle, including Mars’ nightside. IUVS performs limb scans during the spacecraft periapse, and obtains UV images of the planet from reconstructed apoapse disk scans. Two types of aurora have been detected on Mars’ nightside by virtue of emissions requiring excitation by precipitating charged particles. The first type, discrete aurora, are localized near the boundary between open and closed crustal magnetic field lines. They generally appear at ~140 km altitude and the spectra correspond to moderate mean electron energy precipitation. These detections confirm the discovery of discrete discovered by Mars Express/SPICAM. IUVS has discovered a second type, diffuse aurora, which are widespread and potentially global. They occur as low as 70 km altitude; the spectra, depth of penetration and timing are consistent with the precipitation of relativistic electrons from the Sun. IUVS has discovered a third type, proton aurora, on Mars’ dayside as excess hydrogen Lyman alpha emission confined to Mars’ thermosphere. The intermittent excesses appear correlated with enhanced solar wind conditions. This type is the most common form of aurora detected by IUVS. IUVS results dispel a common misconception that aurora only occur near the edges of closed planetary magnetic field lines. While this is true for terrestrial aurora and discrete aurora on Mars, it is false for Mars’ diffuse and proton auroras. In this sense, Mars serves as the best archetype for auroral processes on unmagnetized planets in our solar system and beyond. [less ▲]

Detailed reference viewed: 29 (2 ULiège)
See detailThe UV spectrum of Phobos as measured by MAVEN/IUVS
Chaffin; Deighan; Schneider et al

Conference (2017, December)

Detailed reference viewed: 18 (3 ULiège)
See detailMAVEN/IUVS periapse Ly-alpha observations: variabilité and constraints on H and CO2 abundance
Hughes; et al; Stiepen, Arnaud ULiege et al

Conference (2017, December)

Detailed reference viewed: 10 (3 ULiège)
See detailMars topographic clouds: MAVEN/IUVS observations and LMD-MGCM predictions
connour; et al; Stiepen, Arnaud ULiege et al

Conference (2017, December)

Detailed reference viewed: 16 (2 ULiège)
See detailConstraints on Mars Hydrogen loss from MAVEN: processes and present day-rates
chaffin; deighan; stewart et al

Conference (2017, December)

Detailed reference viewed: 11 (2 ULiège)
See detailImproving MAVEN-IUVS Ly-Alpha apoapsis images
AlMannaei; Chaffin; Jain et al

Conference (2017, December)

Detailed reference viewed: 7 (2 ULiège)
See detailSeasonal transport in Mars' mesosphere-thermosphere revealed by NO nightglow
Stiepen, Arnaud ULiege; Royer; Schneider et al

Conference (2017, December)

Detailed reference viewed: 5 (2 ULiège)
See detailThree types of aurora on Mars
Schneider; Jain; Deighan et al

Conference (2017, December)

Detailed reference viewed: 7 (1 ULiège)
See detailFirst Detection of the Nitric Oxide Dayglow on Mars
Stevens, Michael H.; Siskind, David E.; Evans, J. Scott et al

Conference (2017, October 01)

Nitric oxide (NO) is a well-known indicator of solar and auroral activity in the terrestrial upper atmosphere. Direct measurements of NO on Mars can therefore constrain studies of energetic processes ... [more ▼]

Nitric oxide (NO) is a well-known indicator of solar and auroral activity in the terrestrial upper atmosphere. Direct measurements of NO on Mars can therefore constrain studies of energetic processes controlling the composition and structure of its upper atmosphere (80-200 km). Identifying and quantifying these processes is one of the science objectives of NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission currently orbiting Mars. NO can be observed directly by solar resonance fluorescence in the mid-ultraviolet (MUV). Indeed, this approach has routinely been used to measure terrestrial NO for 50 years. On Mars, this “dayglow” emission is very weak relative to other bright MUV features and thus has confounded attempts at its detection there for nearly the same amount of time. Here, we report the first detection of the NO dayglow in the Martian atmosphere using limb observations by the Imaging Ultraviolet Spectrograph (IUVS) on the MAVEN spacecraft. The detection is enabled by the spectral modeling and removal of the carbon monoxide Cameron bands, which dominate the MUV limb spectra. We focus on the spectral region between 213.0-225.5 nm, where three NO gamma bands emit. We will infer NO densities from the dayglow spectra and compare our observations with predictions from a photochemical model. We will discuss the implications, particularly in the context of previous in situ measurements. [less ▲]

Detailed reference viewed: 10 (0 ULiège)
See detailMars topographic clouds: MAVEN/IUVS observations and LMD MGCM predictions
Schneider, Nicholas M.; Connour, Kyle; Forget, Francois et al

Conference (2017, October 01)

The Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian atmosphere. From these apoapse disk ... [more ▼]

The Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian atmosphere. From these apoapse disk images, information about clouds and aerosols can be retrieved and comprise the only MAVEN observations of topographic clouds and cloud morphologies. Measuring local time variability of large-scale recurring cloud features is made possible with MAVEN’s ~4.5-hour elliptical orbit, something not possible with sun-synchronous orbits. We have run the LMD MGCM (Mars global circulation model) at 1° x 1° resolution to simulate water ice cloud formation with inputs consistent with observing parameters and Mars seasons. Topographic clouds are observed to form daily during the late mornings of northern hemisphere spring and this phenomenon recurs until late summer (Ls = 160°), after which topographic clouds wane in thickness. By northern fall, most topographic clouds cease to form except over Arsia Mons and Pavonis Mons, where clouds can still be observed. Our data show moderate cloud formation over these regions as late as Ls = 220°, something difficult for the model to replicate. Previous studies have shown that models have trouble simulating equatorial cloud thickness in combination with a realistic amount of water vapor and not-too-thick polar water ice clouds, implying aspects of the water cycle are not fully understood. We present data/model comparisons as well as further refinements on parameter inputs based on IUVS observations. [less ▲]

Detailed reference viewed: 14 (0 ULiège)
See detailFirst Retrieval of Thermospheric Carbon Monoxide From Mars Dayglow Observations
Evans, J. Scott; Stevens, Michael H.; Jain, Sonal et al

Conference (2017, October 01)

As a minor species in the Martian thermosphere, Carbon Monoxide (CO) is a tracer that can be used to constrain changing circulation patterns between the lower thermosphere and upper mesosphere of Mars. By ... [more ▼]

As a minor species in the Martian thermosphere, Carbon Monoxide (CO) is a tracer that can be used to constrain changing circulation patterns between the lower thermosphere and upper mesosphere of Mars. By linking CO density distributions to dynamical wind patterns, the structure and variability of the atmosphere will be better understood. Direct measurements of CO can therefore provide insight into the magnitude and pattern of winds and provide a metric for studying the response of the atmosphere to solar forcing. In addition, CO measurements can help solve outstanding photochemical modeling problems in explaining the abundance of CO at Mars. CO is directly observable by electron impact excitation and solar resonance fluorescence emissions in the far-ultraviolet (FUV). The retrieval of CO from solar fluorescence was first proposed over 40 years ago, but has been elusive at Mars due to significant spectral blending. However, by simulating the spectral shape of each contributing emission feature, electron impact excitation and solar fluorescence brightnesses can be extracted from the composite spectrum using a multiple linear regression approach. We use CO Fourth Positive Group (4PG) molecular band emission observed on the limb (130 - 200 km) by the Imaging Ultraviolet Spectrograph (IUVS) on NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft over both northern and southern hemispheres from October 2014 to December 2016. We present the first direct retrieval of CO densities by FUV remote sensing in the upper atmosphere of Mars. Atmospheric composition is inferred using the terrestrial Atmospheric Ultraviolet Radiance Integrated Code adapted to the Martian atmosphere. We investigate the sensitivity of CO density retrievals to variability in solar irradiance, solar longitude, and local time. We compare our results to predictions from the Mars Global Ionosphere-Thermosphere Model as well as in situ measurements by the Neutral Gas and Ion Mass Spectrometer on MAVEN and quantify any differences. [less ▲]

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See detailMars’ seasonal mesospheric transport seen through nitric oxide nightglow
Milby, Zachariah; Stiepen, Arnaud ULiege; Jain, Sonal et al

Conference (2017, October 01)

We analyze the ultraviolet nightglow in the atmosphere of Mars through nitric oxide (NO) δ and γ band emissions as observed by the Imaging UltraViolet Spectrograph (IUVS) instrument onboard the Mars ... [more ▼]

We analyze the ultraviolet nightglow in the atmosphere of Mars through nitric oxide (NO) δ and γ band emissions as observed by the Imaging UltraViolet Spectrograph (IUVS) instrument onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft when it is at apoapse and periapse.In the dayside thermosphere of Mars, solar extreme-ultraviolet radiation dissociates CO[SUB]2[/SUB] and N[SUB]2[/SUB] molecules. O([SUP]3[/SUP]P) and N([SUP]4[/SUP]S) atoms are carried from the dayside to the nightside by the day-night hemispheric transport process, where they descend through the nightside mesosphere and can radiatively recombine to form NO(C[SUP]2[/SUP]Π). The excited molecules rapidly relax by emitting photons in the UV δ and γ bands. These emissions are indicators of the N and O atom fluxes from the dayside to Mars’ nightside and the descending circulation pattern from the nightside thermosphere to the mesosphere (e.g. Bertaux et al., 2005 ; Bougher et al., 1990 ; Cox et al., 2008 ; Gagné et al., 2013 ; Gérard et al., 2008 ; Stiepen et al., 2015, 2017).Observations of these emissions are gathered from a large dataset spanning different seasonal conditions.We present discussion on the variability in the brightness and altitude of the emission with season, geographical position (longitude), and local time, along with possible interpretation by local and global changes in the mesosphere dynamics. We show the possible impact of atmospheric waves forcing longitudinal variability and data-to-model comparisons indicating a wave-3 structure in Mars’ nightside mesosphere. Quantitative comparison with calculations of the Laboratoire de Météorologie Dynamique-Mars Global Climate Model (LMD-MGCM) suggests the model reproduces both the global trend of NO nightglow emission and its seasonal variation. However, it also indicates large discrepancies, with the emission up to a factor 50 times fainter in the model, suggesting that the predicted transport is too efficient toward the night winter pole in the thermosphere by ˜20° latitude to the north.These questions are now addressed through an extensive dataset of disk images, in complement to improved simulations of the LMD-MGCM and the Mars Global Ionosphere-Thermosphere Model (MGITM) models. [less ▲]

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See detailUnveiling Mars nightside mesosphere dynamics by IUVS/MAVEN global images of NO nightglow
Stiepen, Arnaud ULiege; Jain, S. K.; Schneider, N. M. et al

Conference (2017, September 01)

We analyze the morphology of the ultraviolet nightglow in the Martian upper atmosphere through Nitric Oxide (NO) δ and γ bands emissions observed by the Imaging Ultraviolet Spectrograph instrument on the ... [more ▼]

We analyze the morphology of the ultraviolet nightglow in the Martian upper atmosphere through Nitric Oxide (NO) δ and γ bands emissions observed by the Imaging Ultraviolet Spectrograph instrument on the Mars Atmosphere and Volatile EvolutioN spacecraft. The seasonal dynamics of the Martian thermosphere-mesosphere can be constrained based on the distribution of these emissions. We show evidence for local (emission streaks and splotches) and global (longitudinal and seasonal) variability in brightness of the emission and provide quantitative comparisons to GCM simulations. [less ▲]

Detailed reference viewed: 9 (0 ULiège)