scholarly journals Multispectral analysis of the Martian dayglow from UVIS-NOMAD on board TGO

2021 ◽  
Author(s):  
Jean-Claude Gérard ◽  
Shohei Aoki ◽  
Gkouvelis Leonardos ◽  
Soret Lauriane ◽  
Willame Yannick ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Trace Gas ◽  
Green Line ◽  
Model Simulations ◽  
Solar Occultation ◽  
Uv Visible ◽  
Polar Aurora ◽  
Multispectral Analysis ◽  
Co Addition ◽  
Characteristic Colour

<p>The NOMAD instrument currently in orbit around Mars on board ESA's ExoMars Trace Gas Orbiter (TGO) includes UVIS, a UV-visible spectrograph covering the spectral range 200-700 nm. This instrument has two channels, one for solar occultation and a nadir channel essentially designed to analyse solar backscattered radiation. Since April 2019, the TGO spacecraft is occasionally tilted so that the nadir channel is pointed toward the Martian limb to observe the planetary airglow. A first success was the discovery of the forbidden oxygen green line at 557.7 nm that is ubiquitous in all UVIS limb dayside observations. This emission gives its characteristic colour to the terrestrial polar aurora but had was never been observed before in the airglow of other planetary atmospheres. This emission is excited by the interaction between solar radiation and CO<sub>2</sub> and shows a mean intensity peak near 80 km. More recently, the much weaker OI 630-nm emission has been detected following co-addition of several hundreds of UVIS spectra. It is much weaker than the green line, as a consequence of collisional deactivation of the long-lived O(<sup>1</sup>D) excited state. Both oxygen dayglow emissions have been successfully modelled. Molecular transitions are also identified in the UVIS ultraviolet spectrum, including the CO Cameron bands, the CO<sub>2</sub><sup>+</sup> ultraviolet doublet at 298-299 nm and the Fox-Duffendack-Baker (FDB) bands. They originate from the lower thermosphere near 120 km.</p><p>The seasonal-latitudinal evolution of the 557.7-nm emission will be described and compared with model simulations for the conditions of the observations. Simultaneous observations of dayglow emissions originating from different altitude will be available over a full Martian year. Coupled with model simulations, they provide constraints on the changing structure and composition of the Martian lower thermosphere, a region difficult to probe otherwise.</p><p> </p>

Nadir retrieval of ice clouds and dust from NOMAD/UVIS on board Exomars TGO

2021 ◽  
Author(s):  
Yannick Willame ◽  
Jon Mason ◽  
Ann C. Vandaele ◽  
Justin Erwin ◽  
Arianna Piccialli ◽  
...  
Keyword(s):  
Spectral Range ◽  
Seasonal Distribution ◽  
Trace Gas ◽  
Ice Clouds ◽  
Mars Atmosphere ◽  
Preliminary Results ◽  
Aerosol Retrieval ◽  
Solar Occultation ◽  
Uv Visible ◽  
Applied Optics

<p>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 using a suite of three spectrometers operating in the UV-visible and infrared. NOMAD is a spectrometer operating in ultraviolet (UV), visible and infrared (IR) wavelengths covering large parts of the 0.2-4.3 µm spectral range [1].</p> <p>The UV-visible “UVIS” instrument covers the spectral range from 200 to 650 nm and can perform solar occultation, nadir and limb observations [2]. The main purpose of UVIS is dedicated to the analysis and monitoring of ozone and aerosols such as dust and ice clouds.  In the present work we will present preliminary results of the aerosol retrieval in the UV recorded in nadir geometry: spatial and seasonal distribution of ice clouds and dust.</p> <div> <p> </p> <p>References<br />[1] Vandaele et al. 2018. Space Sci. Rev.<br />[2] Patel et al., 2017. Applied Optics.</p> </div> <p> </p>

Nadir retrieval of ice clouds, dust and ozone from NOMAD/UVIS on board Exomars TGO

2020 ◽  
Author(s):  
Yannick Willame ◽  
Ann C. Vandaele ◽  
Arianna Piccialli ◽  
Cédric Depiesse ◽  
Frank Daerden ◽  
...  
Keyword(s):  
Spectral Range ◽  
Seasonal Distribution ◽  
Trace Gas ◽  
Ice Clouds ◽  
Mars Atmosphere ◽  
Preliminary Results ◽  
Solar Occultation ◽  
Uv Visible

<p>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 using a suite of three spectrometers operating in the UV-visible and infrared. NOMAD is a spectrometer operating in ultraviolet (UV), visible and infrared (IR) wavelengths covering large parts of the 0.2-4.3 µm spectral range [1].</p> <p>The UV-visible “UVIS” instrument covers the spectral range from 200 to 650 nm and can perform solar occultation, nadir and limb observations [2]. The main purpose of UVIS is dedicated to the analysis and monitoring of ozone and aerosols such as dust and ice clouds.  In the present work we will present preliminary results of UV retrievals recorded in nadir geometry: spatial and seasonal distribution of ice clouds, dust and ozone.</p>

scholarly journals Validation of 525 nm and 1020 nm aerosol extinction profiles derived from ACE imager data: comparisons with GOMOS, SAGE II, SAGE III, POAM III, and OSIRIS

2007 ◽  
Vol 7 (4) ◽  
pp. 12349-12379
Author(s):  
F. Vanhellemont ◽  
C. Tetard ◽  
A. Bourassa ◽  
M. Fromm ◽  
J. Dodion ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Trace Gas ◽  
Aerosol Extinction ◽  
Optical Extinction ◽  
Upper Troposphere ◽  
Solar Occultation ◽  
Stellar Occultation ◽  
Uv Visible ◽  
Atmospheric Trace Gas ◽  
Chemistry Experiment

Abstract. The Canadian ACE (Atmospheric Chemistry Experiment) mission is dedicated to the retrieval of a large number of atmospheric trace gas species using the solar occultation technique in the infrared and UV/visible spectral domain. However, two additional solar disk imagers (at 525 nm and 1020 nm) were added for a number of reasons, including the retrieval of aerosol and cloud products. In this paper, we present the first validation results for these imager aerosol/cloud optical extinction coefficient profiles, by intercomparison with profiles derived from measurements performed by 3 solar occultation instruments (SAGE II, SAGE III, POAM III), one stellar occultation instrument (GOMOS) and one limb sounder (OSIRIS). The results indicate that the ACE imager profiles are of good quality in the upper troposphere/lower stratosphere, although the aerosol extinction for the visible channel at 525 nm contains a significant negative bias at higher altitudes, while the profiles are systematically too high at 1020 nm. Both problems are probably related to ACE imager instrumental issues.

scholarly journals Inter-comparison of stratospheric O<sub>3</sub> and NO<sub>2</sub> abundances retrieved from balloon borne direct sun observations and Envisat/SCIAMACHY limb measurements

2005 ◽  
Vol 5 (5) ◽  
pp. 10747-10797
Author(s):  
A. Butz ◽  
H. Bösch ◽  
C. Camy-Peyret ◽  
M. Chipperfield ◽  
M. Dorf ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Optical Absorption ◽  
Ultra Violet ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Line Of Sight ◽  
Vertical Profiles ◽  
Altitude Range ◽  
Solar Occultation ◽  
Uv Visible

Abstract. Stratospheric O3 and NO2 abundances measured by different remote sensing instruments are inter-compared: (1) Line-of-sight absorptions and vertical profiles inferred from solar spectra in the ultra-violet (UV), visible and infrared (IR) wavelength ranges measured by the LPMA/DOAS (Limb Profile Monitor of the Atmosphere/Differential Optical Absorption Spectroscopy) balloon payload during balloon ascent/descent and solar occultation are examined with respect to internal consistency. (2) The balloon borne stratospheric profiles of O3 and NO2 are compared to collocated space-borne skylight limb observations of the Envisat/SCIAMACHY satellite instrument. The trace gas profiles are retrieved from SCIAMACHY spectra using different algorithms developed at the Universities of Bremen and Heidelberg and at the Harvard-Smithsonian Center for Astrophysics. A comparison scheme is used that accounts for the spatial and temporal mismatch as well as differing photochemical conditions between the balloon and satellite borne measurements. It is found that the balloon borne measurements internally agree to within ±10% and ±20% for O3 and NO2, respectively, whereas the agreement with the satellite is ±20% for both gases in the 20 km to 30 km altitude range and in general worse below 20 km.

NOMAD on ExoMars TGO: Data processing and public release via the ESA Planetary Science Archive

2020 ◽  
Author(s):  
Ian Thomas ◽  
Ann Carine Vandaele ◽  
Frank Daerden ◽  
Bojan Ristic ◽  
Yannick Willame ◽  
...  
Keyword(s):  
Data Processing ◽  
Scientific Community ◽  
Planetary Science ◽  
Trace Gas ◽  
Current Status ◽  
Solar Occultation ◽  
Enormous Amount ◽  
Uv Visible ◽  
Occultation Data ◽  
Very High

&lt;p&gt;NOMAD is a suite of three spectrometers on-board the ExoMars Trace Gas Orbiter. The spectrometers operate in solar occultation, nadir and limb observing modes, measuring in the infrared (2.2-4.3um in occultation; 2.2-3.8um in nadir) and UV-visible (0.2-0.65um) spectral regions. The nominal science phase began on 21st April 2018; since then NOMAD has collected over one Martian year of data.&lt;br&gt;&lt;br&gt;Due to the very high spectral and spatial resolution of NOMAD, an enormous amount of data has already been generated - including tens of millions of solar occultation and nadir spectra - which currently total around four terabytes and are spread across almost half a million files. To serve the scientific community, all calibrated data will eventually be made publicly available in PDS4 format via the ESA Planetary Science Archive at &lt;br&gt;&lt;br&gt;At the time of writing, the NOMAD data collection has successfully passed peer review, and data from two of the three channels will be available very shortly. This first release will consist of: 1) infrared solar occultation data; 2) UV-visible solar occultation data; and 3) UV-visible nadir data. The infrared nadir and infrared and UV-visible limb data will be released later, once the calibration is finalised. In this presentation I will update the scientific community on the current status of the NOMAD PSA archive, including a description of the data and how to start using it.&lt;/p&gt;&lt;!-- COMO-HTML-CONTENT-END --&gt; &lt;p class=&quot;co_mto_htmlabstract-citationHeader&quot;&gt; &lt;strong class=&quot;co_mto_htmlabstract-citationHeader-intro&quot;&gt;How to cite:&lt;/strong&gt; Thomas, I., Vandaele, A. C., Daerden, F., Ristic, B., Willame, Y., Depiesse, C., Aoki, S., Trompet, L., Erwin, J., Robert, S., Piccialli, A., Neary, L., Viscardy, S., Mason, J., Patel, M., Bellucci, G., and Lopez-Moreno, J. J.: NOMAD on ExoMars TGO: Data processing and public release via the ESA Planetary Science Archive, Europlanet Science Congress 2020, online, 21 September&amp;#8211;9 Oct 2020, EPSC2020-521, 2020 &lt;/p&gt;

scholarly journals Inter-comparison of stratospheric O<sub>3</sub> and NO<sub>2</sub> abundances retrieved from balloon borne direct sun observations and Envisat/SCIAMACHY limb measurements

2006 ◽  
Vol 6 (5) ◽  
pp. 1293-1314 ◽  
Author(s):  
A. Butz ◽  
H. Bösch ◽  
C. Camy-Peyret ◽  
M. Chipperfield ◽  
M. Dorf ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Optical Absorption ◽  
Ultra Violet ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Line Of Sight ◽  
Vertical Profiles ◽  
Altitude Range ◽  
Solar Occultation ◽  
Uv Visible

Abstract. Stratospheric O3 and NO2 abundances measured by different remote sensing instruments are inter-compared: (1) Line-of-sight absorptions and vertical profiles inferred from solar spectra in the ultra-violet (UV), visible and infrared (IR) wavelength ranges measured by the LPMA/DOAS (Limb Profile Monitor of the Atmosphere/Differential Optical Absorption Spectroscopy) balloon payload during balloon ascent/descent and solar occultation are examined with respect to internal consistency. (2) The balloon borne stratospheric profiles of O3 and NO2 are compared to collocated space-borne skylight limb observations of the Envisat/SCIAMACHY satellite instrument. The trace gas profiles are retrieved from SCIAMACHY spectra using different algorithms developed at the Universities of Bremen and Heidelberg and at the Harvard-Smithsonian Center for Astrophysics. A comparison scheme is used that accounts for the spatial and temporal mismatch as well as differing photochemical conditions between the balloon and satellite borne measurements. It is found that the balloon borne measurements internally agree to within ±10% and ±20% for O3 and NO2, respectively, whereas the agreement with the satellite is ±20% for both gases in the 20 km to 30 km altitude range and in general worse below 20 km.

scholarly journals Case studies of the impact of orbital sampling on stratospheric trend detection and derivation of tropical vertical velocities: solar occultation vs. limb emission sounding

2016 ◽  
Vol 16 (18) ◽  
pp. 11521-11534 ◽  
Author(s):  
Luis F. Millán ◽  
Nathaniel J. Livesey ◽  
Michelle L. Santee ◽  
Jessica L. Neu ◽  
Gloria L. Manney ◽  
...  
Keyword(s):  
Case Studies ◽  
Atmospheric Chemistry ◽  
Stratospheric Ozone ◽  
Sampling Bias ◽  
Nonuniform Sampling ◽  
Trend Detection ◽  
Trace Gas ◽  
Uniform Sampling ◽  
Solar Occultation ◽  
The Impact

Abstract. This study investigates the representativeness of two types of orbital sampling applied to stratospheric temperature and trace gas fields. Model fields are sampled using real sampling patterns from the Aura Microwave Limb Sounder (MLS), the HALogen Occultation Experiment (HALOE) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The MLS sampling acts as a proxy for a dense uniform sampling pattern typical of limb emission sounders, while HALOE and ACE-FTS represent coarse nonuniform sampling patterns characteristic of solar occultation instruments. First, this study revisits the impact of sampling patterns in terms of the sampling bias, as previous studies have done. Then, it quantifies the impact of different sampling patterns on the estimation of trends and their associated detectability. In general, we find that coarse nonuniform sampling patterns may introduce non-negligible errors in the inferred magnitude of temperature and trace gas trends and necessitate considerably longer records for their definitive detection. Lastly, we explore the impact of these sampling patterns on tropical vertical velocities derived from stratospheric water vapor measurements. We find that coarse nonuniform sampling may lead to a biased depiction of the tropical vertical velocities and, hence, to a biased estimation of the impact of the mechanisms that modulate these velocities. These case studies suggest that dense uniform sampling such as that available from limb emission sounders provides much greater fidelity in detecting signals of stratospheric change (for example, fingerprints of greenhouse gas warming and stratospheric ozone recovery) than coarse nonuniform sampling such as that of solar occultation instruments.

scholarly journals Validation of MIPAS IMK/IAA methane profiles

2015 ◽  
Vol 8 (12) ◽  
pp. 5251-5261 ◽  
Author(s):  
A. Laeng ◽  
J. Plieninger ◽  
T. von Clarmann ◽  
U. Grabowski ◽  
G. Stiller ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Michelson Interferometer ◽  
European Space Agency ◽  
Trace Gas ◽  
Mixing Ratios ◽  
Air Sampler ◽  
Solar Occultation ◽  
Space Agency ◽  
Scanning Imaging ◽  
Satellite Instruments

Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is an infrared (IR) limb emission spectrometer on the Envisat platform. It measures trace gas distributions during day and night, pole-to-pole, over an altitude range from 6 to 70 km in nominal mode and up to 170 km in special modes, depending on the measurement mode, producing more than 1000 profiles day−1. We present the results of a validation study of methane, version V5R_CH4_222, retrieved with the IMK/IAA (Institut für Meteorologie und Klimaforschung, Karlsruhe/Instituto de Astrofisica de Andalucia, Grenada) MIPAS scientific level 2 processor. The level 1 spectra are provided by the ESA (European Space Agency) and version 5 was used. The time period covered is 2005–2012, which corresponds to the period when MIPAS measured trace gas distributions at a reduced spectral resolution of 0.0625 cm−1. The comparison with satellite instruments includes the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the HALogen Occultation Experiment (HALOE), the Solar Occultation For Ice Experiment (SOFIE) and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). Furthermore, comparisons with MkIV balloon-borne solar occultation measurements and with air sampling measurements performed by the University of Frankfurt are presented. The validation activities include bias determination, assessment of stability, precision validation, analysis of histograms and comparison of corresponding climatologies. Above 50 km altitude, MIPAS methane mixing ratios agree within 3 % with ACE-FTS and SOFIE. Between 30 and 40 km an agreement within 3 % with SCIAMACHY has been found. In the middle stratosphere, there is no clear indication of a MIPAS bias since comparisons with various instruments contradict each other. In the lower stratosphere (below 25 km) MIPAS CH4 is biased high with respect to satellite instruments, and the most likely estimate of this bias is 14 %. However, in the comparison with CH4 data obtained from cryogenic whole-air sampler (cryosampler) measurements, there is no evidence of a high bias in MIPAS between 20 and 25 km altitude. Precision validation is performed on collocated MIPAS–MIPAS pairs and suggests a slight underestimation of its uncertainties by a factor of 1.2. No significant evidence of an instrumental drift has been found.

scholarly journals Detection of Outflow of Formaldehyde and Glyoxal from the African continent to the Atlantic Ocean with a MAX-DOAS Instrument

2019 ◽  
Author(s):  
Lisa K. Behrens ◽  
Andreas Hilboll ◽  
Andreas Richter ◽  
Enno Peters ◽  
Leonardo M. A. Alvarado ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Cape Verde ◽  
Trace Gas ◽  
Biogenic Emissions ◽  
African Continent ◽  
Satellite Measurements ◽  
Model Simulations ◽  
Spatial Gradients ◽  
Volatile Organic ◽  
Continental Outflow

Abstract. Trace gas maps retrieved from satellite measurements show enhanced levels of the atmospheric volatile organic compounds formaldehyde (HCHO) and glyoxal (CHOCHO) over the Atlantic Ocean. To validate the spatial distribution of this continental outflow, ship-based measurements were taken during the project Continental Outflow of Pollutants towards the MArine tRoposphere (COPMAR). A Multi-AXis Differential Optical Absorption Spectrometer (MAX-DOAS) was operated on board the research vessel (RV) Maria S. Merian during the cruise MSM58/2. This cruise was conducted in October 2016 from Ponta Delgada (Azores) to Cape Town (South Africa), crossing between Cape Verde and the African continent. The instrument was continuously scanning the horizon looking towards the African continent. Enhanced levels of HCHO and CHOCHO were found in the area of expected outflow during this cruise. The observed spatial gradients of HCHO and CHOCHO along the cruise track agree with the spatial distributions from satellite measurements and MOZART-4 model simulations. The continental outflow from the African continent is observed in an elevated layer, higher than 1000 m, and probably originates from biogenic emissions or biomass burning according to FLEXPART emission sensitivities.

scholarly journals Solar occultation with SCIAMACHY: algorithm description and first validation

2005 ◽  
Vol 5 (1) ◽  
pp. 17-66 ◽  
Author(s):  
J. Meyer ◽  
A. Bracher ◽  
A. Rozanov ◽  
A. C. Schlesier ◽  
H. Bovensmann ◽  
...  
Keyword(s):  
Vertical Profile ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Trace Gas ◽  
Transmission Spectra ◽  
Atmospheric Transmission ◽  
Gas Concentration ◽  
Solar Occultation ◽  
First Results ◽  
The Vertical Distribution

Abstract. This presentation concentrates on solar occultation measurements with the spaceborne spectrometer SCIAMACHY in the UV-Vis wavelength range. Solar occultation measurements provide unique information about the vertical distribution of atmospheric constituents. For retrieval of vertical trace gas concentration profiles, an algorithm has been developed based on the optimal estimation method. The forward model is capable to simulate the extinction signals of different species as they occur in atmospheric transmission spectra obtained from occultation measurements. Furthermore, correction algorithms have been implemented to address shortcomings of the tangent height pre-processing and inhomogeneities of measured solar spectra. First results of O3 and NO2 vertical profile retrievals have been validated with data from ozone sondes and satellite based occultation instruments. The validation shows very promising results for SCIAMACHY O3 and NO2 values between 15 to 35 km with errors in the order of 10% and 15%, respectively.

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