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Optical windows play a crucial role in laser ablation systems by protecting delicate components inside the chamber while allowing the transmission of laser energy. However, material buildup during the laser ablation process can lead to a significant loss of optical transmission over time. In this work, material deposition on the optical window by laser ablation of olivine using two laser systems operating at 30 kHz, 1 mJ pulse energy, and 20 Hz, 9.6 mJ pulse energy was performed and its impact on the window's transmission properties, laser-induced breakdown spectroscopy (LIBS) signal, and window recovery is presented. Ablation at 30 kHz with 1 mJ pulses for 10 min resulted in substantial particle deposition on the window, causing a significant drop in transmission. Transmission of clean window dropped abruptly from 90% to nearly 0% (in the UV region from 200 to 300 nm) and 35% (at 600 nm) affecting the LIBS signal. In contrast, ablation at 20 Hz with 9.6 mJ pulses for 5 min showed no material deposition or transmission loss. Additionally, the study demonstrated that the same laser system used for ablation could be employed to remove the deposited material from the window, facilitating its recovery. Laser cleaning of the window at 30 kHz and 12 W average power restored the transmission values from 39% to 62% at 400 nm in the UV region, with potential for further improvement through parameter optimization. In addition, the identification of the hydroxyl group in olivine, which is relevant to NASA's terahertz heterodyne spectrometer for in situ resource utilization project for the validation of water molecules is presented. [ABSTRACT FROM AUTHOR]

We obtained high-resolution spectra of Jupiter between 4.6 and 5.4 µm using NIRSPEC on the Keck 2 telescope in February 2017. We measured the spatial variation of NH 3 , H 2 O, and the pressure level of deep (p > 3 bar) clouds using two geometries. We aligned the slit north–south on Jupiter's Central Meridian to measure the spatial variation of the gas composition and cloud structure between 66 ° N and 70 ° S. With the slit aligned east–west, we also examined the longitudinal variation at two regions of the North Equatorial Belt (NEB) at 18 ° N and at 8 ° N near the latitude of the Galileo Probe entry site. We used the integrated line absorption, also known as the equivalent width, of deuterated methane (CH 3 D) at 4.66 µm to derive the pressure level of deep clouds between 3 and 7 bar. From thermochemical models, these are most likely water clouds. At the location of a deep cloud revealed by HST methane-band imaging, we found spectroscopic evidence for an opaque cloud at the 5 bar level. We also identified regions on Jupiter that lacked deep clouds but exhibited evidence for upper clouds and enhanced NH 3 . We estimated column-averaged mole fractions of H 2 O and NH 3 above the opaque lower boundary of the deep cloud. The meridional scan exhibited significant belt-zone structure with retrieved NH 3 abundances in the 200–400 ppm range above the opaque lower cloud, except for a depletion (down to 90 ppm) in the NEB. Water in Jupiter's belts varies from a maximum of 7 ppm at 8 ° S to a minimum of 1.5 ppm at 23 ° S. We found evidence for water clouds and enhanced NH 3 and H 2 O in the South Equatorial Belt Outbreak region at 13 ° S. The NEB is a heterogeneous region with significant variation in all of these quantities. The NH 3 abundance at 18 ° N and 8 ° N varies with the longitude with mole fractions between 120 and 300 ppm. The H 2 O abundance at these same latitudes varies with the longitude with mole fractions between 3 and 10 ppm. Our volatile mole fractions apply to the 5 to 8 bar pressure range (or to the level of an opaque cloud top where found at shallower pressure); therefore, they imply a deeper gradient continuing to increase toward higher concentrations detected by the Galileo Probe Mass Spectrometer at 11 and 20 bar. Hot Spots in the NEB exhibit minimal cloud opacity; however, they lack prominent anomalies in the concentrations of NH 3 or H 2 O. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.11.014 Byline: Geronimo L. Villanueva (a), Michael J. Mumma (b), Robert E. Novak (c), Tilak Hewagama (a)(d) Keywords: Infrared observations; Spectroscopy; Mars; atmosphere; Astrobiology Abstract: We present the discovery of a new vibrational band system of isotopic CO.sub.2 (carbon dioxide) near 3.3 [mu]m, with multiple strong P, Q and R lines in the prime spectral region used to search for Mars CH.sub.4 (methane). The band system was discovered on Mars using high-resolution spectrometers (I'/[delta]I'40,000, CSHELL and NIRSPEC) at telescopes (NASA-IRTF and Keck-2) atop Mauna Kea, HI. The observed line intensities and frequencies agree very well with values predicted by a vibrational band model that we developed using known parameters for the molecular levels involved. Using this model, we synthesized spectra for different observing conditions (from Space and ground-based telescopes) and for different spectral resolving powers (5000 to 40,000). Although the total atmospheric burden on Mars is more than 150 times smaller than on Earth, the greater mixing ratio of CO.sub.2 ensures that its column abundance on Mars is almost 20 times greater than on Earth. Thus, weak telluric CO.sub.2 band systems appear much stronger on Mars. Many molecules of possible biological and geothermal interest have strong signatures at these wavelengths, in particular hydrocarbons owing to their strong ro-vibrational CH stretching modes. For example, the new isotopic CO.sub.2 band-system encompasses lines of CH.sub.4, C.sub.2H.sub.6 (ethane), CH.sub.3OH (methanol) and H.sub.2O (water). Implications for previous and future searches of biomarker gases are presented. Author Affiliation: (a) NASA Goddard Space Flight Center, Mailstop 693, Greenbelt, MD 20771, USA (b) NASA Goddard Space Flight Center, Mailstop 690.3, Greenbelt, MD 20771, USA (c) Department of Physics, Iona College, New Rochelle, NY 10801, USA (d) Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA Article History: Received 7 August 2007; Revised 12 October 2007

Ozone is an important observable tracer of martian photochemistry, including odd hydrogen (H[O.sub.x]) species important to the chemistry and stability of the martian atmosphere. Infrared heterodyne spectroscopy with spectral resolution [greater than or equal to] [10.sup.6] provides the only ground-based direct access to ozone absorption features in the martian atmosphere. Ozone abundances were measured with the Goddard Infrared Heterodyne Spectrometer and the Heterodyne Instrument for Planetary Wind and Composition at the NASA Infrared Telescope Facility on Mauna Kea, Hawai'i. Retrieved total ozone column abundances from various latitudes and orbital positions ([L.sub.S] = 40[degrees], 74[degrees], 102[degrees] 115[degrees], 202[degrees], 208[degrees], 291[degrees]) are compared to those predicted by the first three-dimensional gas phase photochemical model of the martian atmosphere [Lefevre, F., Lebonnois, S., Montmessin, E, Forget, E, 2004. J. Geophys. Res. 109, doi: 10.1029/2004JE002268. E07004]. Observed and modeled ozone abundances show good agreement at all latitudes at perihelion orbital positions ([L.sub.S] = 202[degrees], 208[degrees], 291[degrees]). Observed low-latitude ozone abundances are significantly higher than those predicted by the model at aphelion orbital positions ([L.sub.S] = 40[degrees], 74[degrees], 115[degrees]). Heterogeneous loss of odd hydrogen onto water ice cloud particles would explain the discrepancy, as clouds are observed at low latitudes around aphelion on Mars. Keywords: Mars, atmosphere; Photochemistry; Infrared observations; Spectroscopy; Abundances, atmospheres

Observations of ozone on Mars were made using the Goddard Space Flight Center's Infrared Heterodyne Spectrometer and Heterodyne Instrument for Planetary Wind and Composition at the NASA Infrared Telescope Facility. Ozone is an important observable tracer of martian photochemistry. Infrared heterodyne spectroscopy with spectral resolution [greater than or equal to] [10.sup.6] is the only technique that directly measures ozone in the martian atmosphere from the surface of the Earth. Ozone column abundances down to the martian surface were acquired in seven data sets taken between 1988 and 2003 at various orbital positions ([L.sub.S] = 40[degrees], 74[degrees], 102[degrees], 115[degrees], 202[degrees], 208[degrees], 291[degrees]). Ozone abundances are compared with those retrieved using ultraviolet techniques, showing good agreement. Odd hydrogen (H[O.sub.x]) chemistry predicts anticorrelation of ozone and water vapor abundances. Retrieved ozone abundances consistently show anticorrelation with corresponding water vapor abundances, providing strong confirmation of odd hydrogen activity. Deviation from strict anticorrelation between the observed total column densities of ozone and water vapor suggests that constituent vertical distribution is an additional, significant factor. Keywords: Mars, atmosphere; Infrared observations; Photochemistry; Spectroscopy; Abundances, atmospheres

Ethane spectral lines were observed in emission from Titan in August 1993, October 1995, and September 1996, at a spectral resolution of [lambda]/[DELTA][lambda] [approximately equal to] [10.sup.6], at wavelength 11.7-11.9 [micro]m using the Goddard Infrared Heterodyne Spectrometer at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. The ethane mole fraction is determined to be (8.8 [+ or -] 2.2) x [10.sup.-6] (68.3% confidence limits, '1[sigma]'), averaging the retrievals from each observing run obtained using the 'recommended' thermal profile of R. V. Yelle, D. Strobel, E. Lellouch, and D. Gautier (1997, in Huygens: Science, Payload, and Mission (J.-P. Lebreton, Ed.), pp. 243-256, European Space Agency SP-1177). Key Words: satellites of Saturn; Titan; atmospheres, composition; infrared observations.

Infrared emission lines of stratospheric ammonia (N[H.sub.3]) were observed following the collisions of the fragments of Comet Shoemaker-Levy 9 with Jupiter in July of 1994 at the impact sites of fragments G and K. Infrared heterodyne spectra near 10.7 [micro]m were obtained by A. Betz et al. (in Abstracts for Special Sessions on Comet Shoemaker-Levy 9, The 26th Meeting of the Division for Planetary Sciences, Washington DC, 31 Oct.-4 Nov. 1994, p. 25) using one of the Infrared Spatial Interferometer telescope systems on Mount Wilson. Lineshapes of up to three different N[H.sub.3] emission lines were measured at a resolving power of [~10.sup.7] at multiple times following the impacts. We present here our radiative transfer analysis of the fully resolved spectral lineshapes of the multiple rovibrational lines. This analysis provides information on temperature structure and N[H.sub.3] abundance distributions and their temporal changes up to 18 days after impact. These results are compared to photochemical models to determine the role of photochemistry and other mechanisms in the destruction and dilution of N[H.sub.3] in the jovian stratosphere after the SL9 impacts. One day following the G impact, the inferred temperature above 0.001 mbar altitude is 283 [+ or -] 13 K, consistent with a recent plume splashback model. Cooling of the upper stratosphere to 204 K by the fourth day and to quiescence after a week is consistent with a simple gray atmosphere radiative flux calculation and mixing with cold jovian air. During the first 4 days after impact, N[H.sub.3] was present primarily at altitudes above 1 mbar with a column density of (7.7 [+ or -] 1.6) x [10.sup.17] [cm.sup.-2] after 1 day and (3.7 [+ or -] 0.8) x [10.sup.17] [cm.sup.-2] after 4 days. (Errors represent precision.) We obtained >2.5 times more N[H.sub.3] than can be supplied by nitrogen from a large cometary fragment, suggesting a primarily jovian source for the N[H.sub.3]. By 18 days postimpact, a return to quiescent upper stratospheric temperature is retrieved for the G region, with an N[H.sub.3] column density of 7.3 x [10.sup.17] [cm.sup.-2] or more in the lower stratosphere, possibly supplied by N[H.sub.3] upwelling across an impact-heated and turbulent tropopause, which may have been masked by initial dust and haze. Above the 1-mbar level, the maximum retrieved column density decreased to 6.5 x [10.sup.16] [cm.sup.-2] Comparison to photochemical models indicates that photolysis alone is not sufficient to account for the loss of N[H.sub.3] above 1-mbar by that time, even when chemical reformation of N[H.sub.3] is ignored. We speculate that the dispersion of plume material at high altitudes (above 1 mbar) is responsible for the change in the spectra observed a few days postimpact. Data on the K impact region provide qualitatively consistent results. Key Words: Comets S-L9; Jupiter; Jupiter--atmosphere; infrared observations; photochemistry.

Multispectral snapshot imagers are capable of producing 2-D spatial images with a single exposure at selected, numerous wavelengths using the same camera, therefore, operate differently from push broom or whiskbroom imagers. They are payloads of choice in multi-angular, multi-spectral imaging missions that use small satellites flying in controlled formation, to retrieve Earth science measurements dependent on the target’s bidirectional reflectance-distribution function. Narrow fields of view are needed to capture images with moderate spatial resolution. This paper quantifies the dependencies of the imager’s optical system, spectral elements, and camera on the requirements of the formation mission and their impact on performance metrics, such as spectral range, swath, and signal-to-noise ratio (SNR). All variables and metrics have been generated from a comprehensive, payload design tool. The baseline optical parameters selected (a diameter of 7 cm, a focal length of 10.5 cm, a pixel size of 20~\mu \textm , and a field of view of 1.15°) and snapshot imaging technologies are available. The spectral components shortlisted were waveguide spectrometers, acousto-optic tunable filters (AOTF), electronically actuated Fabry–Perot interferometers, and integral field spectrographs. Qualitative evaluation favored AOTFs, because of their low weight, small size, and flight heritage. Quantitative analysis showed that the waveguide spectrometers perform better in terms of achievable swath (10–90 km) and SNR (>20) for 86 wavebands, but the data volume generated will need very high bandwidth communication to downlink. AOTFs meet the external data volume caps well as the minimum spectral (wavebands) and radiometric (SNR) requirements, therefore, are found to be currently feasible and design changes to improve swath suggested. [ABSTRACT FROM PUBLISHER]

EPOXI (EPOCh + DIXI) is a NASA Discovery Program Mission of Opportunity using the Deep Impact flyby spacecraft. The EPOCh (Extrasolar Planet Observation and Characterization) Science Investigation will gather photometric time series of known transiting exoplanet systems from January through August 2008. Here we describe the steps in the photometric extraction of the time series and present preliminary results of the first four EPOCh targets. [ABSTRACT FROM PUBLISHER]

The NASA Discovery mission EPOXI, utilizing the Deep Impact flyby spacecraft, comprises two phases: EPOCh (Extrasolar Planet Observation and Characterization) and DIXI (Deep Impact eXtended Investigation). With EPOCh, we use the 30-cm high resolution visible imager to obtain ultraprecise photometric light curves of known transiting planet systems. We will analyze these data for evidence of additional planets, via transit timing variations or transits; for planetary moons or rings; for detection of secondary eclipses and the constraint of geometric planetary albedos; and for refinement of the system parameters. Over a period of four months, EPOCh observed four known transiting planet systems, with each system observed continuously for several weeks. Here we present an overview of EPOCh, including the spacecraft and science goals, and preliminary photometry results. [ABSTRACT FROM PUBLISHER]

Ethane spectral lines were observed in emission from Titan in August 1993, October 1995, and September 1996, at a spectral resolution of λ/Δλ≈106, at wavelength 11.7−11.9 μm using the Goddard Infrared Heterodyne Spectrometer at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. The ethane mole fraction is determined to be (8.8±2.2)×10−6 (68.3% confidence limits, “1σ”), averaging the retrievals from each observing run obtained using the “recommended” thermal profile of R. V. Yelle, D. Strobel, E. Lellouch, and D. Gautier (1997, in Huygens: Science, Payload, and Mission (J.-P. Lebreton, Ed.), pp. 243–256, European Space Agency SP-1177). [Copyright &y& Elsevier]

The demonstration of a newly developed compact thermal imager (CTI) on the International Space Station (ISS) has provided not only a technology advancement but a rich high-resolution dataset on global clouds, atmospheric and land emissions. This study showed that the free-running CTI instrument could be calibrated to produce scientifically useful radiance imagery of the atmosphere, clouds, and surfaces with a vertical resolution of ~460 m at limb and a horizontal resolution of ~80 m at nadir. The new detector demonstrated an excellent sensitivity to detect the weak limb radiance perturbations modulated by small-scale atmospheric gravity waves. The CTI's high-resolution imaging was used to infer vertical cloud temperature profiles from a side-viewing geometry. For nadir imaging, the combined high-resolution and high-sensitivity capabilities allowed the CTI to better separate cloud and surface emissions, including those in the planetary boundary layer (PBL) that had small contrast against the background surface. Finally, based on the ISS's orbit, the stable detector performance and robust calibration algorithm produced valuable diurnal observations of cloud and surface emissions with respect to solar local time during May–October 2019, when the CTI had nearly continuous operation. [ABSTRACT FROM AUTHOR]

Abstract: We report temperatures in Venus’ upper mesosphere/lower thermosphere, deduced from reanalyzing very high resolution infrared spectroscopy of CO2 emission lines acquired in 1990 and 1991. Kinetic temperatures at ∼110km altitude (0.15Pa) are derived from the Doppler width of fully-resolved single line profiles measured near 10.4μm wavelength using the NASA GSFC Infrared Heterodyne Spectrometer (IRHS) at the NASA IRTF on Mauna Kea, HI, close to Venus inferior conjunction and two Venus solstices. Measured temperatures range from ∼200 to 240K with uncertainty typically less than 10K. Temperatures retrieved from similar measurement in 2009 using the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS) at the NOAO McMath Telescope at Kitt Peak, AZ are 10–20K lower. Temperatures retrieved more recently from the SOIR instrument on Venus EXpress are consistent with these results when the geometry of observation is accounted for. It is difficult to compare ground-based sub-mm retrievals extrapolated to 110km due to their much larger field of view, which includes the night side regions not accessible to infrared heterodyne observations. Temperature variability appears to be high on day-to-day as well as longer timescales. Observed short term and long term variability may be attributed to atmospheric dynamics, diurnal variability and changes over solar activity and seasons. The Venus International Reference Atmosphere (VIRA) model predicts cooler temperatures at the sampled altitudes in the lower thermosphere/upper mesosphere and is not consistent with these measurements. [Copyright &y& Elsevier]

Abstract: Ozone is a tracer of photochemistry in the atmosphere of Mars and an observable used to test predictions of photochemical models. We present a comparison of retrieved ozone abundances on Mars using ground-based infrared heterodyne measurements by NASA Goddard Space Flight Center’s Heterodyne Instrument for Planetary Wind And Composition (HIPWAC) and space-based Mars Express Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) ultraviolet measurements. Ozone retrievals from simultaneous measurements in February 2008 were very consistent (0.8μm-atm), as were measurements made close in time (ranging from <1 to >8μm-atm) during this period and during opportunities in October 2006 and February 2007. The consistency of retrievals from the two different observational techniques supports combining the measurements for testing photochemistry-coupled general circulation models and for investigating variability over the long-term between spacecraft missions. Quantitative comparison with ground-based measurements by NASA/GSFC’s Infrared Heterodyne Spectrometer (IRHS) in 1993 reveals 2–4 times more ozone at low latitudes than in 2008 at the same season, and such variability was not evident over the shorter period of the Mars Express mission. This variability may be due to cloud activity. [Copyright &y& Elsevier]

Abstract: We present the discovery of a new vibrational band system of isotopic CO2 (carbon dioxide) near 3.3 μm, with multiple strong P, Q and R lines in the prime spectral region used to search for Mars CH4 (methane). The band system was discovered on Mars using high-resolution spectrometers (, CSHELL and NIRSPEC) at telescopes (NASA-IRTF and Keck-2) atop Mauna Kea, HI. The observed line intensities and frequencies agree very well with values predicted by a vibrational band model that we developed using known parameters for the molecular levels involved. Using this model, we synthesized spectra for different observing conditions (from Space and ground-based telescopes) and for different spectral resolving powers (5000 to ). Although the total atmospheric burden on Mars is more than 150 times smaller than on Earth, the greater mixing ratio of CO2 ensures that its column abundance on Mars is almost 20 times greater than on Earth. Thus, weak telluric CO2 band systems appear much stronger on Mars. Many molecules of possible biological and geothermal interest have strong signatures at these wavelengths, in particular hydrocarbons owing to their strong ro-vibrational Cing modes. For example, the new isotopic CO2 band-system encompasses lines of CH4, C2H6 (ethane), CH3OH (methanol) and H2O (water). Implications for previous and future searches of biomarker gases are presented. [Copyright &y& Elsevier]

Abstract: We present new measurements of vibrational band systems of isotopic carbon dioxide (CO2) with multiple strong lines in the wavelength region 3.3–3.7μm. In our ground-based searches for methane (CH4) and other biomarker gases on Mars, we discovered two new vibrational band systems that we identify as the previously unknown ν 2+ν 3 band of 16O12C18O and the 2ν 1 band of the rare isotope 16O13C18O. We also extended and provide refined spectroscopic constants for the 2ν 1 band of 16O12C17O, detecting 38 new lines. The newly discovered 2ν 1 band of 16O13C18O at 3.7μm and the 2ν 1 band of 16O12C17O at 3.6μm extend over the prime spectral region used when searching for deuterated water (HDO) and formaldehyde (H2CO) on Mars. The ν 2+ν 3 band of 16O12C18O at 3.3μm interferes with the ν 3 band of CH4 at 3.3μm. If unrecognized, even weak bands of CO2 can obscure searches for trace gases on Mars, so it is important to quantify them. Here, we report molecular parameters from the measured line positions that agree well with values calculated from the known energy levels of these isotopologues, and we provide absolute band strengths for each system. [Copyright &y& Elsevier]