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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

On the Utility of the Molecular Oxygen Dayglow Emissions as Proxies for Middle Atmospheric Ozone

Molecular oxygen dayglow emissions arise in part from processes related to the Hartley band photolysis of ozone. It is therefore possible to derive daytime ozone concentrations from measurements of the volume emission rate of either dayglow. The accuracy to which the ozone concentration can be inferred depends on the accuracy to which numerous kinetic and spectroscopic rate constants are known, including rates which describe the excitation of molecular oxygen by processes that are not related to the ozone concentration. We find that several key rate constants must be known to better than 7 percent accuracy in order to achieve an inferred ozone concentration accurate to 15 percent from measurements of either dayglow. Currently, accuracies for various parameters typically range from 5 to 100 percent.

Mlynczak, Martin G.↗
NASA NTRS2019

Impact of Clouds and Hazes on the Simulated JWST Transmission Spectra of Habitable Zone Planets in the TRAPPIST-1 System

The TRAPPIST-1 system, consisting of an ultracool host star having seven known Earth-sized planets, will be a prime target for atmospheric characterization with the James Webb Space Telescope (JWST). However, the detectability of atmospheric molecular species may be severely impacted by the presence of clouds and/or hazes. In this work, we perform 3D general circulation model (GCM) simulations with the LMD-G model supplemented by 1D photochemistry simulations at the terminator with the Atmos model to simulate several possible atmospheres for TRAPPIST-1e, 1f, and 1g: (1) modern Earth, (2) Archean Earth, and (3) CO2-rich atmospheres. The JWST synthetic transit spectra were computed using the GSFC Planetary Spectrum Generator. We find that the TRAPPIST-1e, 1f, and 1g atmospheres, with clouds and/or hazes, could be detected using JWST's NIRSpec Prism from the CO2 absorption line at 4.3 μm in less than 15 transits at 3σ or less than 35 transits at 5σ. However, our analysis suggests that other gases would require hundreds (or thousands) of transits to be detectable. We also find that H2O, mostly confined in the lower atmosphere, is very challenging to detect for these planets or similar systems if the planets' atmospheres are not in a moist greenhouse state. This result demonstrates that the use of GCMs, self-consistently taking into account the effect of clouds and subsaturation, is crucial to evaluate the detectability of atmospheric molecules of interest, as well as for interpreting future detections in a more global (and thus robust and relevant) approach.

Thomas J. Fauchez↗
NASA NTRS1994

Optical remote sensing for measurement of toxic gases

There is renewed interest in using optical remote sensing techniques for measuring and monitoring airborne toxins. Many instruments have been used to measure traces of atmospheric molecular species. Some optical remote sensing technology is in use for measuring or monitoring toxic or pollutant gases. The examples in this article provide a number of lessons that may be of use in the new field of optical remote sensing of toxic gases. Topics covered include the following: atmospheric properties, Fourier transform spectrometry, gas-filter correlation, differential absorption laser systems, aircraft missions, laser long-path instruments, differential optical absorption spectrometry, and ozone measurement.

Grant, William B.↗
NASA NTRS1994

Io's fast sodium: Implications for molecular and atomic atmospheric escape

Recent observational evidence for sodium-bearing molecular ions in the Io plasma torus has strong implications for the nature of Io's atmosphere (Schneider et al. 1991). We use a Monte Carlo model offast-sodium production to analyze high-resolution ground-based images of sodium emission. We find the observations can be explained if a significant fraction of Io's exobase is molecular, possible including a sodium-bearing molecule, Total sodium loss rates from Io imply a collisionally thick atmosphere. Most of the images indicate significant slow-down of the corotating plasma near Io.

Wilson, Jody K.↗
NASA NTRS1996

Radioactive Transfer Models for Saturn and Titan

The infrared spectra of the earth's atmosphere and planetary atmospheres contains information about atmospheric physical and chemical processes. Atmospheric molecular constituents absorb and emit infrared radiation by rotational and vibrational transition. Observed spectra exhibit characteristic features in the electromagnetic spectrum region. Observation of the absorption or thermal emission spectra may be obtained with space-borne high resolution infrared spectrometers in the 10-5000 cm(exp -1) (2-1000 micro-m) spectral region. Information about the atmospheric thermal structure, composition, and the chemical and physical processes of the observed spectral was accomplished. A preliminary version of a P-T retrieval algorithm for Saturn using all three modes for temperature inversion, e.g., CH4-limb, and H2-nadir spectra was completed and tested for accuracy. Radiative transfer and inversion programs were studied and analyzed for applications to infrared limb thermal emission observations of Saturn and Titan from the Cassini Orbiter, as well as Earth's atmosphere. Analysis and modification of the existing radiative transfer and inversion programs for Earth and planetary atmospheres are being made. Data analysis and retrieval of information form the observations by digital calculations were carried out at UAH and MSFC computer. The working program for generating and reading g-k arrays for using the c-k arrays via the c-k method for radiative transfer calculations for desired atmospheric and instrumental parameters was completed, tested for accuracy and resides at the MSFC computer.

Wu, S. T.↗
NASA NTRS1988

Advanced infrared astronomy

This task supports the application of infrared heterodyne and Fourier transform spectroscopy to ultra-high resolution studies of molecular constituents of planetary astomspheres and cometary comae. High spectral and spatial resolutions are especially useful for detection and study of localized, non-thermal phenomena in low temperature and low density regions, for detection of trace constituents and for measurement of winds and dynamical phenomena such as thermal tides. Measurement and analysis of individual spectial lines permits retrieval of atmospheric molecular abundances and temperatures and thus, information on local photochemical processes. Determination of absolute line positions to better than 10 to the minus eighth power permits direct measurements of gas velocity to a few meters/sec. Observations are made from ground based heterodyne spectrometers at the Kitt Peak McMath solar telescope and from the NASA infrared Telescope Facility on Mauna Kea, Hawaii. Wind velocities at 110km altitude on Venus were extracted approximately 1 m/sec from measurements of non-thermal emission cores of 10.3 micron CO2 lines. Results indicate a subsolar to antisolar circulationwith a small zonal retrograde component.

Kostiuk, T.↗
NASA NTRS1998

F/NAS/ Pressure Temperature Retrieval Techniques

The purpose of this investigation is to study methods and ways for rapid inversion programs involving the correlated k-method, and to modify the existing programs so that the rapid analysis of data can be accomplished. The earth's atmosphere as well as those around the planets consist of gases which emit radiation in the infrared spectral region, providing wealth of information about chemical and physical processes in the atmosphere. The atmospheric molecular constituents absorb and radiate by vibrational and rotational transitions, and the observed spectra exhibit characteristic spectral features in the region of the electromagnetic spectrum. The observed absorption or thermal emission spectra may be obtained with space-borne high resolution infrared spectrometers the 50-1000 micrometers spectral region. A detailed analysis of the observed spectra leads to information about the atmospheric thermal structure, composition, and the physical and chemical processes. The analytic techniques involve the development of radiative transfer models for the calculation of the observed radiance and transmittances for realistic atmospheric conditions and observational geometries, and the development of inversion methods for retrieval of atmospheric parameters from the observations.

Poularikas, Alexander↗
NASA NTRS2018

VLTI-GRAVITY Measurements of Cool Evolved Stars I. Variable Photosphere and Extended Atmosphere of the Mira Star R Peg

Context. Dynamic model atmospheres of Mira stars predict variabilities in the photospheric radius and in atmospheric molecular layers which are not yet strongly constrained by observations. Aim. Here we measure the variability of the oxygen-rich Mira star R Peg in near-continuum and molecular bands. Methods. We used near-infrared K-band spectro-interferometry with a spectral resolution of about 4000 obtained at four epochs between post-maximum and minimum visual phases employing the newly available GRAVITY beam combiner at the Very Large Telescope Interferometer (VLTI). Results. Our observations show a continuum radius that is anti-correlated with the visual lightcurve. Uniform disc (UD) angular diameters at a near-continuum wavelength of 2.24 m are steadily increasing with values of 8.7 0.1 mas, 9.4 0.1 mas, 9.8 0.1 mas, and 9.9 0.1 mas at visual phases of 0.15, 0.36, 0.45, 0.53, respectively. UD diameters at a bandpass around 2.05 m, dominated by water vapour, follow the near-continuum variability at larger UD diameters between 10.7 mas and 11.7 mas. UD diameters at the CO 2-0 bandhead, instead, are correlated with the visual lightcurve and anti-correlated with the near-continuum UD diameters, with values between 12.3 mas and 11.7 mas. Conclusions. The observed anti-correlation between continuum radius and visual lightcurve is consistent with an earlier study of the oxygen-rich Mira S Lac, and with recent 1D CODEX dynamic model atmosphere predictions. The amplitude of the variation is comparable to the earlier observations of S Lac, and smaller than predicted by CODEX models. The wavelength-dependent visibility variations at our epochs can be reproduced by a set of CODEX models at model phases between 0.3 and 0.6. The anti-correlation of water vapour and CO contributions at our epochs suggests that these molecules undergo different processes in the extended atmosphere along the stellar cycle. The newly available GRAVITY instrument is suited to conducting longer time series observations, which are needed to provide strong constraints on the model-predicted intra- and inter-cycle variability.

photospheric radius↗
NASA NTRS1973

Ultraviolet observations of Mars made by the Orbiting Astronomical Observatory.

Ultraviolet albedos of Mars in the region from 2000 to 3600 A are discussed. When the reflectivity due to the known amount of CO2 on Mars is accounted for, the remaining reflectivity may be used to set an upper limit for the surface albedo. The result disagrees qualitatively with published ultraviolet reflectivities of limonite and carbon suboxide. An alternate interpretation of the observations leads to the conclusion that CO2 comprises at least 60% of the molecular atmosphere of Mars, assuming the remainder to be argon. A comparison of the OAO results with 1969 Mariner ultraviolet data reveals some important areas of conflict. Attempts to detect Mars at wavelengths less than 2000 A were unsuccessful, with only very high upper limits being set.

Caldwell, J.↗
NASA NTRS1980

The 1980 summer research fellowship program

The problem of incorporating visual input into robot systems is described. The photochemistry of the stratosphere, particularly possible permutations of the ozone layer, is discussed. Photoelectrochemical properties of metal thio-hypodiphosphates are investigated. Extreme eigenvalues are computed by the Lancqos approach. The rotational Raman spectra of the molecular atmosphere is studied. A computer operated mathematical symbolic manipulation system is described. Preparation of polycrystalline semiconductor electrodes of tungsten and molybdenum dichalcogenides is received.

Darden, G. C.↗
NASA NTRS1983

The detection of H2 in cool carbon stars

Spectra of several carbon stars in the two micron region are examined and compared with synthetic spectra from model atmospheres. Molecular hydrogen has been directly observed in carbon stars for the first time through the quadrupole 1-0 S(1) line at 4712.9/cm. It is definitely present in several Mira variables, and is definitely not present in several irregular variables and one Mira variable. A discrepancy between the predicted and observed line depths at different temperatures is shown. Resolution of the discrepancy by change of temperature alone would require an upward revision of the present effective temperature scale by at least 600 K. Several possible resolutions of the dilemma are briefly examined.

Goebel, J. H.↗
NASA NTRS1989

Inspecting our upper atmosphere

The Upper Atmosphere Research Satellite (UARS) has been proposed for intensive studies of the 15-100 km-altitude region of the earth's atmosphere, begining in 1991. This 14,000-lb satellite will carry a suite of 10 instruments able to study the energy input and loss, photochemistry, and circulation of the upper atmosphere, as well as the extensive web of interactions among these three processes. UARS's remote sensors will give attention to the atmospheric molecular species of the nitrogen, hydrogen, and chlorine families.

Reber, C. A.↗