Publications by Kevin Olsen

First detection of ozone in the mid-infrared at Mars: implications for methane detection

Astronomy & Astrophysics EDP Sciences 639 (2020) A141

K Olsen, F Lefèvre, F Montmessin, A Trokhimovskiy, L Baggio, A Fedorova​, J Alday​, A Lomakin​, D Belyaev, A Patrakeev, A Shakun​, O Korablev

<br><strong>Aims: </strong>The ExoMars Trace Gas Orbiter (TGO) was sent to Mars in March 2016 to search for trace gases diagnostic of active geological or biogenic processes.</br> <br><strong>Methods: </strong>We report the first observation of the spectral features of Martian ozone (O3) in the mid-infrared range using the Atmospheric Chemistry Suite (ACS) Mid-InfaRed (MIR) channel, a cross-dispersion spectrometer operating in solar occultation mode with the finest spectral resolution of any remote sensing mission to Mars.</br> <br><strong>Results: </strong>Observations of ozone were made at high northern latitudes (> 65◦N) prior to the onset of the 2018 global dust storm (Ls = 163–193◦). During this fast transition phase between summer and winter ozone distribution, the O3 volume mixing ratio observed is 100–200 ppbv near 20 km. These amounts are consistent with past observations made at the edge of the southern polar vortex in the ultraviolet range. The observed spectral signature of ozone at 3000–3060 cm−1 directly overlaps with the spectral range of the methane (CH4) ν3 vibration-rotation band, and it, along with a newly discovered CO2 band in the same region, may interfere with measurements of methane abundance.</br>

First observation of the magnetic dipole CO2 main isotopologue absorption band at 3.3 µm in the atmosphere of Mars by the ExoMars Trace Gas Orbiter ACS instrument

Astronomy & Astrophysics EDP Sciences (2020)

A Trokhimovskiy, V Perevalov, O Korablev, A Fedorova, K Olsen, J Bertaux, A Patrakeev, A Shakun, F Montmessin, F Lefèvre

Stormy water on Mars: the distribution and saturation of atmospheric water during the dusty season

Science American Association for the Advancement of Science (2020)

AA Fedorova, F Montmessin, O Korablev, M Luginin, A Trokhimovskiy, DA Belyaev, NI Ignatiev, F Lefèvre, J Alday, P Irwin, K Olsen, J-L Bertaux, E Millour, A Määttänen, A Shakun, AV Grigoriev, A Patrakeev, S Korsa, N Kokonkov, L Baggio, F Forget, C Wilson

The loss of water from Mars to space is thought to result from the transport of water to the upper atmosphere, where it is dissociated to hydrogen and escapes the planet. Recent observations have suggested large, rapid seasonal intrusions of water into the upper atmosphere, boosting the hydrogen abundance. We use the Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter to characterize the water distribution by altitude. Water profiles during the 2018–2019 southern spring and summer stormy seasons show that high-altitude water is preferentially supplied close to perihelion, and supersaturation occurs even when clouds are present. This implies that the potential for water to escape from Mars is higher than previously thought.

Martian cloud climatology and life cycle extracted from Mars Express OMEGA spectral images

Icarus (2020)

A Szantai, J Audouard, F Forget, KS Olsen, B Gondet, E Millour, JB Madeleine, A Pottier, Y Langevin, JP Bibring

© 2020 A Martian water-ice cloud climatology has been extracted from OMEGA data covering 7 Martian years (MY 26–32) on the dayside. We derived two products, the Reversed Ice Cloud Index (ICIR) and the Percentage of Cloudy Pixels (PCP), indicating the mean cloud thickness and nebulosity over a regular grid (1° longitude × 1° latitude × 1° Ls × 1 h Local Time). The ICIR has been shown to be a proxy of the water-ice column derived from the Mars Climate Database. The PCP confirms the existence and location of the main cloud structures mapped with the ICIR, but also gives a more accurate image of the cloud cover. We observed a more dense cloud coverage over Hellas Planitia, the Lunae Planum region and over large volcanoes (Tharsis volcanoes, Olympus and Elysium Montes) in the aphelion belt. For the first time, thanks to the fact that Mars Express is not in Sun-synchronous orbit, we can explore the clouds diurnal cycle at a given season by combining the seven years of observations. However, because of the eccentric orbit, the temporal coverage remains limited. Identified limitations of the dataset are its small size, the difficult distinction between ice clouds and frosts, and the impact of surface albedo on data uncertainty. We could nevertheless study the diurnal cloud life cycle by averaging the data over larger regions: from specific topographic features (covering a few degrees in longitude and latitude) up to large climatic bands (covering all longitudes). We found that in the tropics (25°S – 25°N) around northern summer solstice, the diurnal thermal tide modulates the abundance of clouds, which is reduced around noon (Local Time). At northern midlatitudes (35°N – 55°N), clouds corresponding to the edge of the north polar hood are observed mainly in the morning and around noon during northern winter (Ls = 260° – 30°). Over Chryse Planitia, low lying morning fogs dissipate earlier and earlier in the afternoon during northern winter. Over Argyre, clouds are present over all daytime during two periods, around Ls = 30° and 160°.

Oxygen isotopic ratios in Martian water vapour observed by ACS MIR on board the ExoMars Trace Gas Orbiter

Astronomy and Astrophysics EDP Sciences 630 (2019) A91

J Alday, CF Wilson, PGJ Irwin, KS Olsen, L Baggio, F Montmessin, A Trokhimovskiy, O Korablev, AA Fedorova, DA Belyaev, A Grigoriev, A Patrakeev, A Shakun

Oxygen isotope ratios provide important constraints on the history of the Martian volatile system, revealing the impact of several processes that might fractionate them, such as atmospheric loss into space or interaction with the surface. We report infrared measurements of the Martian atmosphere obtained with the mid-infrared channel (MIR) of the Atmospheric Chemistry Suite (ACS), onboard the ExoMars Trace Gas Orbiter. Absorption lines of the three main oxygen isotopologues of water vapour (H216O, H218O, and H217O) observed in the transmission spectra allow, for the first time, the measurement of vertical profiles of the 18O/16O and 17O/16O ratios in atmospheric water vapour. The observed ratios are enriched with respect to Earth-like values (δ18O = 200 ± 80‰ and δ17O = 230 ± 110‰ corresponding to the Vienna Standard Mean Ocean Water). The vertical structure of these ratios does not appear to show significant evidence of altitudinal variations.

Validation of the HITRAN 2016 and GEISA 2015 line lists using ACE-FTS solar occultation observations

Journal of Quantitative Spectroscopy and Radiative Transfer 236 (2019)

KS Olsen, CD Boone, GC Toon, F Montmessin, AA Fedorova, O Korablev, A Trokhimovskiy

© 2019 Elsevier Ltd The ExoMars Trace Gas Orbiter (TGO) began its nominal science phase at Mars in April 2018, following releases of editions to two major spectroscopic line lists: GEISA 2015 (Gestion et Etude des Informations Spectroscopiques Atmosphériques: Management and Study of Atmospheric Spectroscopic Information), and HITRAN 2016 (High Resolution Transmission). This work evaluates both line lists over the spectral region between 2325–4350 cm−1 using terrestrial solar occultation observations made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). This spectral region is targeted on Mars by two complementary solar occultation instruments on TGO that will monitor temperature and pressure, aerosols, the abundance of CO2, CO, H2O, HDO, CH4, and other undetected trace gases. Major updates to GEISA 2015 and HITRAN 2016, with respect to previous editions, have been focused on CO2 absorption features in support of Earth-observing missions to monitor greenhouse. Since CO2 is the dominant absorber on Mars, making up 96.5% of the atmosphere, validating the updated line lists is critically important before their deployment for ExoMars. We report that updated CO2 parameters make significant improvements to spectral fits made when using both line lists. Several updates to H2O lines in both line lists also show improvement. The primary difference we observe between the two line lists comes from O3 absorption features near 3850 cm−1 and from several CH4 absorption lines in the regions 2800–3200 cm−1 and 4000–4300 cm−1. Because of these differences, we find that using HITRAN 2016 tends to result in better spectral fits, especially below 30 km, than using GEISA 2015 in this spectral region. Differences are strongly reduced with increasing altitude ( > 40 km) as pressure and gas abundance falls off. It was also discovered that several new errors in both new editions of GEISA and HITRAN were introduced since the HITRAN 2012.

Publisher Correction: No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations.

Nature 569 (2019) E2-

O Korablev, AC Vandaele, F Montmessin, AA Fedorova, A Trokhimovskiy, F Forget, F Lefèvre, F Daerden, IR Thomas, L Trompet, JT Erwin, S Aoki, S Robert, L Neary, S Viscardy, AV Grigoriev, NI Ignatiev, A Shakun, A Patrakeev, DA Belyaev, J-L Bertaux, KS Olsen, L Baggio, J Alday, YS Ivanov, B Ristic, J Mason, Y Willame, C Depiesse, L Hetey, S Berkenbosch, R Clairquin, C Queirolo, B Beeckman, E Neefs, MR Patel, G Bellucci, J-J López-Moreno, CF Wilson, G Etiope, L Zelenyi, H Svedhem, JL Vago, ACS and NOMAD Science Teams

The surname of author Cathy Quantin-Nataf was misspelled 'Quantin-Nata', authors Ehouarn Millour and Roland Young were missing from the ACS and NOMAD Science Teams list, and minor changes have been made to the author and affiliation lists; see accompanying Amendment. These errors have been corrected online.

Publisher Correction: Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter.

Nature 569 (2019) E1-

AC Vandaele, O Korablev, F Daerden, S Aoki, IR Thomas, F Altieri, M López-Valverde, G Villanueva, G Liuzzi, MD Smith, JT Erwin, L Trompet, AA Fedorova, F Montmessin, A Trokhimovskiy, DA Belyaev, NI Ignatiev, M Luginin, KS Olsen, L Baggio, J Alday, J-L Bertaux, D Betsis, D Bolsée, RT Clancy, E Cloutis, C Depiesse, B Funke, M Garcia-Comas, J-C Gérard, M Giuranna, F Gonzalez-Galindo, AV Grigoriev, YS Ivanov, J Kaminski, O Karatekin, F Lefèvre, S Lewis, M López-Puertas, A Mahieux, I Maslov, J Mason, MJ Mumma, L Neary, E Neefs, A Patrakeev, D Patsaev, B Ristic, S Robert, F Schmidt, A Shakun, NA Teanby, S Viscardy, Y Willame, J Whiteway, V Wilquet, MJ Wolff, G Bellucci, MR Patel, J-J López-Moreno, F Forget, CF Wilson, R Young, H Svedhem, JL Vago, D Rodionov, NOMAD Science Team, ACS Science Team

The surname of author Cathy Quantin-Nataf was misspelled 'Quantin-Nata' , authors Ehouarn Millour and Roland Young were missing from the ACS Science Team list, and minor changes have been made to the author and affiliation lists; see accompanying Amendment. These errors have been corrected online.

Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter

Nature Springer 568 (2019) 521-525

AC Vandaele, O Korablev, F Daerden, S Aoki, IR Thomas, F Altieri, M López-Valverde, G Villanueva, G Liuzzi, Smith, JT Erwin, L Trompet, AA Fedorova, F Montmessin, A Trokhimovskiy, DA Belyaev, NI Ignatiev, M Luginin, KS Olsen, L Baggio, J Alday, J-L Bertaux, D Betsis, D Bolsée, Clancy

No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations

Nature Springer Nature 568 (2019) 517-520

O Korablev, AC Vandaele, F Montmessin, AA Fedorova, A Trokhimovskiy, F Forget, F Lefèvre, F Daerden, IR Thomas, L Trompet, JT Erwin, S Aoki, S Robert, L Neary, S Viscardy, AV Grigoriev, NI Ignatiev, A Shakun, A Patrakeev, DA Belyaev, J-L Bertaux, KS Olsen, L Baggio, J Alday, YS Ivanov

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today1. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations2,3,4,5. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere6,7, which—given methane’s lifetime of several centuries—predicts an even, well mixed distribution of methane1,6,8. Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections2,4. We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater4 would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally.

Retrieval of the water ice column and physical properties of water-ice clouds in the Martian atmosphere using the OMEGA imaging spectrometer

Icarus (2019)

KS Olsen, F Forget, JB Madeleine, A Szantai, J Audouard, A Geminale, F Altieri, G Bellucci, F Oliva, L Montabone, MJ Wolff

© 2019 Using spectral images recorded by the OMEGA instrument on Mars Express (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité), we are able to derive physical properties of aerosols in water-ice clouds on Mars for a distribution of pixels over an observed cloud formation. These properties, mean effective radius, r eff , and optical depth (at 0.67 μm), τ i , were used to estimate the water ice-column (WIC), and we found an empirical relationship between the WIC and an ice cloud index (ICI). The overall mean of retrieved r eff is ∼2.2 μm, with a standard deviation of 0.8 μm, and cloud formations with r eff between 4.4 and 5.4 μm are observed. The optical depth varies between 0.2 and 2.0. The OMEGA spectra are primarily sensitive to water ice mass due to absorption, and we find that the ICI, very easy to compute, is a good proxy for the mass of the water-ice column (WIC) along the optical line of sight. Our retrieval of physical properties is limited in time (to before 2010) by the exhaustion of coolant for one of the OMEGA channels, and in space (to equatorial observations between 140 ∘ W and 90 ∘ E) by the availability of surface albedo measurements. However, we used the ICI to compute WIC values for the entire OMEGA data set, which has near-global coverage for Mars years 26–32, and we present a climatology of the WIC derived from the OMEGA data, which features enhancements on the order of 1.2–1.6 pr. μm over the aphelion cloud belt, and 1.5–2.5 pr. μm over the polar hoods. The data set analyzed is for observations between 140 ° W and 90 ° E, and between 35 ∘ S and 35 ∘ N. No restriction is placed on season, but the majority of cloudy observations were during the aphelion period from Ls 35 ∘ to 135 ∘ . This work was motivated by the ability of the OMEGA instrument to observe the distribution of water-ice cloud physical properties, and by the availability of new a priori data sets, especially multi-spectral, aerosol-free surface albedo retrieved from a subset of the OMEGA data featuring a cloud-free sky. The main limitations of the retrieval algorithm are linked to the uncertainties on surface albedo, the dust opacity, and the quantity of water-ice suspended in the atmosphere, which can lead to spectral fits with lower accuracy or unrealistic results. We present distributions of each retrieved parameter, goodness of fit, ICI, and cloud mass, and our investigation of relationships between each parameter. Our approach was to maximize the amount of data analyzed, apply stringent data quality cuts and take a statistical approach to interpretation.

The Atmospheric Chemistry Suite (ACS) of three spectrometers for the ExoMars 2016 Trace Gas Orbiter

Space Science Reviews Springer Netherlands 214 (2017) 7

V Makarov, F Martynovich, I Maslov, D Merzlyakov, PP Moiseev, Y Nikolskiy, A Patrakeev, D Patsaev, A Santos-Skripko, O Sazonov, N Semena, A Semenov, V Shashkin, A Sidorov, AV Stepanov, I Stupin, I Khatuntsev, VA Krasnopolsky, RO Kuzmin, E Lellouch, MA Lopez-Valverde, M Luginin, A Määttänen, E Marcq, J Martin Torres

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 ( &gt; 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 &gt; 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.

Comparison of the GOSAT TANSO-FTS TIR CH volume mixing ratio vertical profiles with those measured by ACE-FTS, ESA MIPAS, IMK-IAA MIPAS, and 16 NDACC stations

Atmospheric Measurement Techniques 10 (2017) 3697-3718

KS Olsen, K Strong, KA Walker, CD Boone, P Raspollini, J Plieninger, W Bader, S Conway, M Grutter, JW Hannigan, F Hase, N Jones, M De Mazière, J Notholt, M Schneider, D Smale, R Sussmann, N Saitoh

© Author(s) 2017. The primary instrument on the Greenhouse gases Observing SATellite (GOSAT) is the Thermal And Near infrared Sensor for carbon Observations (TANSO) Fourier transform spectrometer (FTS). TANSO-FTS uses three short-wave infrared (SWIR) bands to retrieve total columns of CO2 and CH4 along its optical line of sight and one thermal infrared (TIR) channel to retrieve vertical profiles of CO2 and CH4 volume mixing ratios (VMRs) in the troposphere. We examine version 1 of the TANSO-FTS TIR CH4 product by comparing co-located CH4 VMR vertical profiles from two other remote-sensing FTS systems: the Canadian Space Agency's Atmospheric Chemistry Experiment FTS (ACE-FTS) on SCISAT (version 3.5) and the European Space Agency's Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat (ESA ML2PP version 6 and IMK-IAA reduced-resolution version V5R-CH4-224/225), as well as 16 ground stations with the Network for the Detection of Atmospheric Composition Change (NDACC). This work follows an initial inter-comparison study over the Arctic, which incorporated a ground-based FTS at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Canada, and focuses on tropospheric and lower-stratospheric measurements made at middle and tropical latitudes between 2009 and 2013 (mid-2012 for MIPAS). For comparison, vertical profiles from all instruments are interpolated onto a common pressure grid, and smoothing is applied to ACE-FTS, MIPAS, and NDACC vertical profiles. Smoothing is needed to account for differences between the vertical resolution of each instrument and differences in the dependence on a priori profiles. The smoothing operators use the TANSO-FTS a priori and averaging kernels in all cases. We present zonally averaged mean CH4 differences between each instrument and TANSO-FTS with and without smoothing, and we examine their information content, their sensitive altitude range, their correlation, their a priori dependence, and the variability within each data set. Partial columns are calculated from the VMR vertical profiles, and their correlations are examined. We find that the TANSO-FTS vertical profiles agree with the ACE-FTS and both MIPAS retrievals' vertical profiles within 4% (± ∼40ppbv) below 15km when smoothing is applied to the profiles from instruments with finer vertical resolution but that the relative differences can increase to on the order of 25% when no smoothing is applied. Computed partial columns are tightly correlated for each pair of data sets. We investigate whether the difference between TANSO-FTS and other CH4 VMR data products varies with latitude. Our study reveals a small dependence of around 0.1% per 10 degrees latitude, with smaller differences over the tropics and greater differences towards the poles.

Simulation of source intensity variations from atmospheric dust for solar occultation Fourier transform infrared spectroscopy at Mars

Journal of Molecular Spectroscopy 323 (2016) 78-85

KS Olsen, GC Toon, K Strong

© 2015 Elsevier Inc. All rights reserved. A Fourier transform spectrometer observing in solar occultation mode from orbit is ideally suited to detecting and characterizing vertical profiles of trace gases in the Martian atmosphere. This technique benefits from a long optical path length and high signal strength, and can have high spectral resolution. The Martian atmosphere is often subject to large quantities of suspended dust, which attenuates solar radiation along the line-of-sight. An instrument making solar occultation measurements scans the limb of the atmosphere continuously, and the optical path moves through layers of increasing or decreasing dust levels during a single interferogram acquisition, resulting in time-varying signal intensity. If uncorrected, source intensity variations (SIVs) can affect the relative depth of absorption lines, negatively impacting trace gas retrievals. We have simulated SIVs using synthetic spectra for the Martian atmosphere, and investigated different techniques to mitigate the effects of SIVs. We examined high-pass filters in the wavenumber domain, and smoothing methods in the optical path difference (OPD) domain, and conclude that using a convolution operator in the OPD domain can isolate the SIVs and be used to correct for it. We observe spectral residuals of less than 0.25% in both high- and low-dust conditions, and retrieved volume mixing ratio vertical profile differences on the order of 0.5-3% for several trace gases known to be present in the Martian atmosphere. These differences are smaller than those caused by adding realistic noise to the spectra. This work thus demonstrates that it should be possible to retrieve vertical profiles of trace gases in a dusty Martian atmosphere using solar occultation if the interferograms are corrected for the effects of dust.

New temperature and pressure retrieval algorithm for high-resolution infrared solar occultation spectroscopy: Analysis and validation against ACE-FTS and COSMIC

Atmospheric Measurement Techniques 9 (2016) 1063-1082

KS Olsen, GC Toon, CD Boone, K Strong

© 2016 Author(s). Motivated by the initial selection of a high-resolution solar occultation Fourier transform spectrometer (FTS) to fly to Mars on the ExoMars Trace Gas Orbiter, we have been developing algorithms for retrieving volume mixing ratio vertical profiles of trace gases, the primary component of which is a new algorithm and software for retrieving vertical profiles of temperature and pressure from the spectra. In contrast to Earth-observing instruments, which can rely on accurate meteorological models, a priori information, and spacecraft position, Mars retrievals require a method with minimal reliance on such data. The temperature and pressure retrieval algorithms developed for this work were evaluated using Earth-observing spectra from the Atmospheric Chemistry Experiment (ACE) FTS, a solar occultation instrument in orbit since 2003, and the basis for the instrument selected for a Mars mission. ACE-FTS makes multiple measurements during an occultation, separated in altitude by 1.5-5 km, and we analyse 10 CO2 vibration-rotation bands at each altitude, each with a different usable altitude range. We describe the algorithms and present results of their application and their comparison to the ACE-FTS data products. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) provides vertical profiles of temperature up to 40 km with high vertical resolution. Using six satellites and GPS radio occultation, COSMIC's data product has excellent temporal and spatial coverage, allowing us to find coincident measurements with ACE with very tight criteria: less than 1.5 h and 150 km. We present an intercomparison of temperature profiles retrieved from ACE-FTS using our algorithm, that of the ACE Science Team (v3.5), and from COSMIC. When our retrievals are compared to ACE-FTS v3.5, we find mean differences between -5 and +2 K and that our retrieved profiles have no seasonal or zonal biases but do have a warm bias in the stratosphere and a cold bias in the mesosphere. When compared to COSMIC, we do not observe a warm/cool bias and mean differences are between -4 and +1 K. COSMIC comparisons are restricted to below 40 km, where our retrievals have the best agreement with ACE-FTS v3.5. When comparing ACE-FTS v3.5 to COSMIC we observe a cold bias in COSMIC of 0.5 K, and mean differences are between -0.9 and +0.6 K.

Mars methane analogue mission: Mission simulation and rover operations at Jeffrey Mine and Norbestos Mine Quebec, Canada

Advances in Space Research 55 (2015) 2414-2426

A Qadi, E Cloutis, C Samson, L Whyte, A Ellery, JF Bell, G Berard, A Boivin, E Haddad, J Lavoie, W Jamroz, R Kruzelecky, A Mack, P Mann, K Olsen, M Perrot, D Popa, T Rhind, R Sharma, J Stromberg, K Strong, A Tremblay, R Wilhelm, B Wing, B Wong

© 2014 COSPAR. The Canadian Space Agency (CSA), through its Analogue Missions program, supported a microrover-based analogue mission designed to simulate a Mars rover mission geared toward identifying and characterizing methane emissions on Mars. The analogue mission included two, progressively more complex, deployments in open-pit asbestos mines where methane can be generated from the weathering of olivine into serpentine: the Jeffrey mine deployment (June 2011) and the Norbestos mine deployment (June 2012). At the Jeffrey Mine, testing was conducted over 4 days using a modified off-the-shelf Pioneer rover and scientific instruments including Raman spectrometer, Picarro methane detector, hyperspectral point spectrometer and electromagnetic induction sounder for testing rock and gas samples. At the Norbestos Mine, we used the research Kapvik microrover which features enhanced autonomous navigation capabilities and a wider array of scientific instruments. This paper describes the rover operations in terms of planning, deployment, communication and equipment setup, rover path parameters and instrument performance. Overall, the deployments suggest that a search strategy of "follow the methane" is not practical given the mechanisms of methane dispersion. Rather, identification of features related to methane sources based on image tone/color and texture from panoramic imagery is more profitable.

Intercomparison of water vapour and temperature retrievals between the CSA's ACE-FTS and the UCAR/NSPO's COSMIC/FORMOSAT-3 satellites, and presentation of anew algorithm for retrieving temperature

Proceedings of the International Astronautical Congress, IAC 4 (2015) 2941-2944

KS Olsen, GC Toon, CD Boone, PE Sheese, KA Walker, K Strong

Copyright � 2015 by the International Astronautical Federation, All rights reserved. The Canadian Space Agency's (CSA) Atmospheric Chemistry Experiment Fourier transform spectrometer (ACEFTS) onboard SCISAT-1 is a high-resolution Fourier transform spectrometer operating in solar occultation mode in Earth-orbit. ACE-FTS retrieves vertical profiles of temperature, pressure, and volume mixing ratio of 38 molecular species, and relies on international cooperation to validate its data products. Data availability from international Earth-observing missions is vital to interpreting domestic results, and ACE-FTS validation uses data products from 12 instruments and 7 space agencies. Here, we present the latest data set to be incorporated into the ACE-FTS data validation campaign: the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), known as FORMOSAT-3 in Taiwan. A collaboration between Taiwan's National Space Organization (NSPO) and the University Corporation for Atmospheric Research (UCAR) in the US, COSMIC is a group of six small satellites that use signals from GPS satellites to measure water vapour pressure and temperature via radio occultation. We present comparisons with ACE-FTS of both data products in the lower stratosphere and upper troposphere, and a comparison between temperature profiles retrieved by ACE-FTS, COSMIC, and a newly developed algorithm applied to ACEFTS spectra. The new algorithm to retrieve vertical profiles of temperature and pressure from high-resolution solar transmission spectra was developed in support of a partnership between the CSA and NASA's Jet Propulsion Laboratory to place an FTS in orbit around Mars as part of the ESA and NASA's joint ExoMars mission (NASA since withdrew). This algorithm exploits the temperature dependence of individual absorption lines in an infrared vibration-rotation band. ACE-FTS makes multiple measurements during an occultation, separated by 1.5-5 km, and we analyze 10 CO2 vibration-rotation bands at each altitude, each with a different usable altitude range. Retrieved profiles have no seasonal or zonal biases, but do have a warm bias in the stratosphere and a cold bias in the mesosphere, with mean differences less than 5 K when compared to ACE-FTS. COSMIC comparisons are done below 40 km where we have the best agreement with ACE and mean differences are less than 3 K. H2O comparisons between ACE-FTS and COSMIC show good agreement in the stratosphere, and higher concentrations retrieved by COSMIC in the troposphere.

Small-scale methane dispersion modelling for possible plume sources on the surface of Mars

Geophysical Research Letters 39 (2012)

KS Olsen, E Cloutis, K Strong

Intense interest in the characteristics of a methane source on Mars has been spurred by recent observations of a plume structure. The current NASA Mars Science Laboratory and future landers and orbiters will be tasked with understanding the sources of methane. The Canadian Space Agency's Mars Methane Analogue Mission, involving a simulated Mars micro-rover field campaign, was recently able to detect and measure the isotopic composition of methane seeping from boreholes in a serpentine mine in Québec. We aim to determine spatial limits for detecting such a point source above the terrestrial background concentration of methane using gradient transport models. We estimate the source strength to be on the order of 5.3 × <sup>-10</sup> kg s <sup>-1</sup> and find that this produces detectable enhancements at distances less than 11.6 m from the source if there is no wind. These same models are applied to the Mars surface environment to determine whether an instrument on a rover would be capable of detecting a methane point source when not directly downwind of it. The estimated source strengths on Mars are much greater than at Jeffrey Mine and we find that these would be detectable at distances less than 30 m from the plume axis, which lies along the direction of advective transport. Much of the work done on modelling the Martian atmosphere uses large-scale general circulation models and this work examines the behaviour of methane plumes at very local scales. © 2012. American Geophysical Union. All Rights Reserved.