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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The thermal structure and energy balance of the Uranian upper atmosphere

Uranus upper atmosphere occultation observations are reported for August 15-16, 1980, and April 26, 1981. Mean atmospheric light curves of 154 + or - 15 K and 132 + or - 15 K, respectively, are derived from the light curves. A comparison of all available Uranus occultation data since March 1977 suggests a significant mean atmospheric temperature change, with a typical 15 K/year variation. It is suggested that molecular and eddy diffusion, together with atmospheric dynamics, are potentially as important as radiation in the upper atmosphere heat balance of Uranus. The close agreement of occultation immersion and emersion temperatures further suggests that effective meridional transport occurs on Uranus.

French, R. G.↗
NASA NTRS2001

A Regularized Neural Net Approach for Retrieval of Atmospheric and Surface Temperatures with the IASI Instrument

Abstract In this paper, a fast atmospheric and surface temperature retrieval algorithm is developed for the high resolution Infrared Atmospheric Sounding Interferometer (IASI) space-borne instrument. This algorithm is constructed on the basis of a neural network technique that has been regularized by introduction of a priori information. The performance of the resulting fast and accurate inverse radiative transfer model is presented for a large divE:rsified dataset of radiosonde atmospheres including rare events. Two configurations are considered: a tropical-airmass specialized scheme and an all-air-masses scheme.

Aires, F.↗
NASA NTRS1984

Applications of cluster analysis to satellite soundings

The advantages of the use of cluster analysis in the improvement of satellite temperature retrievals were evaluated since the use of natural clusters, which are associated with atmospheric temperature soundings characteristic of different types of air masses, has the potential for improving stratified regression schemes in comparison with currently used methods which stratify soundings based on latitude, season, and land/ocean. The method of discriminatory analysis was used. The correct cluster of temperature profiles from satellite measurements was located in 85% of the cases. Considerable improvement was observed at all mandatory levels using regression retrievals derived in the clusters of temperature (weighted and nonweighted) in comparison with the control experiment and with the regression retrievals derived in the clusters of brightness temperatures of 3 MSU and 5 IR channels.

Munteanu, M. J.↗
NASA NTRS1991

Atomic oxygen and ultraviolet radiation mission total exposures for LDEF experiments

An analytical treatment of the effect of thermal molecular velocity on spacecraft atomic oxygen (AO) flux is presented. The analysis leads to a closed form equation that incorporates the effect of atmospheric temperature, number density, spacecraft velocity, and incidence angle on AO flux. The effects of atmospheric rotation, solar activity, and geomagnetic index on AO flux are also included on the computer model. Data developed with the model are presented for the Long Duration Exposure Facility (LDEF). The results incorporate variations in the defining environmental and orbital parameters of the spacecraft over its six year orbital flight. Cumulative ultraviolet solar and albedo exposures were calculated .

Bourassa, R. J.↗
NASA NTRS1992

Rotational Raman Lidar for Lower Tropospheric Temperature Profiling

Accurate sensing of the tropospheric temperature profile is basically needed in meteorology and 3D mapping of the boundary layer atmospheric temperature over urban and industrial areas. Several temperature lidar techniques were investigated, including Differential Absorption Lidar (DIAL), rotational and vibrational Raman, Rayleigh and high resolution Rayleigh schemes. For the tropospheric applications, the rotational Raman scheme looks potentially advantageous, but several stringent technical problems still remain to be solved. Reported here are the continuing efforts of the system development of the rotational Raman lidar.

Kobayashi, Takao↗
NASA NTRS1992

Regularizing the satellite temperature-retrieval problem through singular-value decomposition of the radiative transfer physics

A new technique is derived for retrieving atmospheric temperature profiles from satellite-measured spectral radiance that appears, in first tests, to effectively circumvent certain difficulties of other well-known and implemented techniques. This method provides an effective manner to avoid numerical instability without having to force the algorithm toward adherence to a priori statistics not dependent on the radiance measurements. This provides the opportunity to obtain more information from satellite sounding instruments, without encountering instabilities owing to overlapping weighting functions.

Thompson, Owen E.↗
NASA NTRS2004

Characterization and Uncertainty Analysis of a Reference Pressure Measurement System for Wind Tunnels

This paper presents the calibration results and uncertainty analysis of a high-precision reference pressure measurement system currently used in wind tunnels at the NASA Langley Research Center (LaRC). Sensors, calibration standards, and measurement instruments are subject to errors due to aging, drift with time, environment effects, transportation, the mathematical model, the calibration experimental design, and other factors. Errors occur at every link in the chain of measurements and data reduction from the sensor to the final computed results. At each link of the chain, bias and precision uncertainties must be separately estimated for facility use, and are combined to produce overall calibration and prediction confidence intervals for the instrument, typically at a 95% confidence level. The uncertainty analysis and calibration experimental designs used herein, based on techniques developed at LaRC, employ replicated experimental designs for efficiency, separate estimation of bias and precision uncertainties, and detection of significant parameter drift with time. Final results, including calibration confidence intervals and prediction intervals given as functions of the applied inputs, not as a fixed percentage of the full-scale value are presented. System uncertainties are propagated beginning with the initial reference pressure standard, to the calibrated instrument as a working standard in the facility. Among the several parameters that can affect the overall results are operating temperature, atmospheric pressure, humidity, and facility vibration. Effects of factors such as initial zeroing and temperature are investigated. The effects of the identified parameters on system performance and accuracy are discussed.

Amer, Tahani↗
NASA NTRS2011

Preliminary Analysis of Images from the Thermospheric Temperature Image on Fast, Affordable, Science and Technology Satellite (FASTSAT)

The Thermospheric Temperature Imager (TTI) on Fast, Affordable, Science and Technology SATellite (FASTSAT) measures the upper atmospheric atomic oxygen emission at 135.6 nm and the molecular nitrogen LBH emission at 135.4 nm to determine the atmospheric O/N2 density ratio. Observations of variations in this thermospheric ratio correspond to electron density variations in the ionosphere. The TTI design makes use of a Fabry-Perot interferometer to measure Doppler widened atmospheric emissions to determine neutral atmospheric temperature from low Earth orbit. FASTSAT launched November 10, 2010 and TTI is currently observing geomagnetic signatures in the aurora and airglow. This work is supported by NASA.

Rodriquez, Marcello↗
NASA NTRS1972

Investigation of the Martian environment by infrared spectroscopy on Mariner 9.

Preliminary analysis of Mariner 9 IR spectroscopic data through May 1972 shows spectral features due to carbon dioxide, water vapor, and silicate dust suspended in the atmosphere. Measurements obtained during and after the planet-wide dust storm indicate that large diurnal variations in atmospheric temperature existed up to at least 30 km. Analysis of spectral features due to the atmospheric dust provides a SiO2 content of 60 (plus or minus 10)%, implying substantial geochemical differentiation. Water vapor estimates yield abundances of 10 to 20 precipitable microns, and no water vapor was detected over the north polar region.

Hanel, R.↗
NASA NTRS1976

Scintillations during occultations by planets. I - An approximate theory

Fluctuations are observed during occultations of both stars and spacecraft by planetary atmospheres. Existing treatments of spacecraft scintillations ignore a major effect unique to occultations: the severe flattening of the Fresnel zone or source image by defocusing. Other large effects, due to 'saturation' of the scintillation, have also been ignored. The deeper portions of atmospheric temperature and density profiles inferred from occultation data are seriously in error if other planets' atmospheres are as turbulent as our own. Thus, profiles obtained from entry probes (e.g., the Soviet Venera series) are probably more accurate than those from radio occultation (Mariner 5 and 10) data. Scintillation greatly reduces the information obtainable from occultation observations; much of the detail attributed to layering in published profiles is probably due to aliasing of turbulence. This paper gives an approximately correct theoretical treatment that is a substantial improvement over published theories, and shows how a more accurate theory could be constructed. Some methods for a more accurate determination of atmospheric structure are proposed.

Young, A. T.↗
NASA NTRS1992

Lidar Measurements of Stratospheric Ozone, Temperature and Aerosol During 1992 UARS Correlative Measurement Campaign

Measurements of stratospheric ozone, temperature, and aerosols were made by the NASA/GSFC mobile stratospheric lidar during the UARS (Upper Atmospheric Research Satellite) Correlative Measurement Campaign at the JPL-Table Mountain Facility in Feb. and Mar. 1992. Due to the presence of substantial amounts of residual volcanic aerosol from the eruption of Mt. Pinatubo, the GSFC lidar system was modified for an accurate measurement of ozone concentration in the stratosphere. While designed primarily for the measurement of stratospheric ozone, this lidar system was also used to measure middle atmosphere temperature and density from 30 to 65 km and stratospheric aerosol from 15 to 35 km. In the following sections, we will briefly describe and present some typical measurements made during this campaign. Stratospheric ozone, temperature, and aerosols profiles derived from data taken between 15 Feb. and 20 Mar., 1992 will be presented at the conference.

Mcgee, Thomas J.↗
NASA NTRS1998

Lidar temperature measurements at NY-Alesund (79N) during winter, 1998

During January and February, 1998, a measurements campaign was held at the Network for the Detection of Stratospheric Change (NDSC) Arctic site at Ny-Alesund (78.9N). Lidar measurements of ozone, temperature and aerosol parameters were made along with balloon sonde and microwave measurements of ozone. Atmospheric temperatures were measured between 10 and 70 km. During the time of the campaign an strong warming occurred at the stratopause, elevating the measured temperature by as much as 80 K. The height of the stratopause descended at this time to below 40 km.

McGee, T. J.↗
NASA NTRS2000

Recent Developments and Applications of Quantum Well Infrared Photodetector Focal Plane Arrays

There are many applications that require long wavelength, large, uniform, reproducible, low cost, stable, and radiation-hard infrared (IR) focal plane arrays (FPAs). For example, the absorption lines of many gas molecules, such as ozone, water, carbon monoxide, carbon dioxide, and nitrous oxide occur in the wavelength region from 3 to 18 micron. Thus, IR imaging systems that operate in the long wavelength IR (LWIR) region (6 - 18 micron) are required in many space borne applications such as monitoring the global atmospheric temperature profiles, relative humidity profiles, cloud characteristics, and the distribution of minor constituents in the atmosphere which are being planned for future NASA Earth and planetary remote sensing systems. Due to higher radiation hardness, lower 1/f noise, and larger array size the GaAs based Quantum Well Infrared Photodetector (QWIP) FPAs are very attractive for such space borne applications compared to intrinsic narrow band gap detector arrays. In this presentation we will discuss the optimization of the detector design, material growth and processing that has culminated in realization of large format long-wavelength QWIP FPAs, portable and miniature LWIR cameras, holding forth great promise for myriad applications in 6-18 micron wavelength range in science, medicine, defense and industry. In addition, we will present some system demonstrations using broadband, two-color, and high quantum efficiency long-wavelength QWIP FPAs.

Gunapala, S. D.↗
NASA NTRS2001

Thermal Emission Spectrometer Results: Mars Atmospheric Thermal Structure and Aerosol Distribution

Infrared spectra returned by the Thermal Emission Spectrometer (TES) are well suited for retrieval of the thermal structure and the distribution of aerosols in the Martian atmosphere. Combined nadir- and limb-viewing spectra allow global monitoring of the atmosphere up to 0.01 mbar (65 km). We report here on the atmospheric thermal structure and the distribution of aerosols as observed thus far during the mapping phase of the Mars Global Surveyor mission. Zonal and temporal mean cross sections are used to examine the seasonal evolution of atmospheric temperatures and zonal winds during a period extending from northern hemisphere mid-summer through vernal equinox (L(sub s) = 104-360 deg). Temperature maps at selected pressure levels provide a characterization of planetary-scale waves. Retrieved atmospheric infrared dust opacity maps show the formation and evolution of regional dust storms during southern hemisphere summer. Response of the atmospheric thermal structure to the changing dust loading is observed. Maps of water-ice clouds as viewed in the thermal infrared are presented along with seasonal trends of infrared water-ice opacity. Uses of these observations for diagnostic studies of the dynamics of the atmosphere are discussed.

Smith, Michael D.↗
NASA NTRS2008

Radiative Transfer and Retrievals in EOF Domain

The Infrared Atmospheric Sounding Interferometer (IASI) is a hyperspectral sensor with 8461 spectral channels and a nominal spectral resolution of 0.25 cm(sup -1). It is computationally intensive to perform radiative transfer calculations and inversions using all these channels. We will present a Principal Component-based Radiative Transfer Model (PCRTM) and a retrieval algorithm which perform all the necessary calculations in EOF domain. Since the EOFs are orthogonal to each other, only about 100 principal components are needed to represent the information content of the 8461 channels. The PCRTM provides the EOF coefficients and associated derivatives with respect to atmospheric and surface parameters needed by the inversion algorithm. The inversion algorithm is based on a non-linear Levenberg-Marquardt method with climatology covariance and a priori information as constraints. The retrieved parameters include atmospheric temperature, moisture and ozone profiles, cloud parameters, surface skin temperature, and surface emissivities. To make the retrieval system even more compact and stable. The atmospheric vertical profiles are compressed into the EOF space as well. The surface emissivities are also compressed into EOF space.

Liu, Xu↗
NASA NTRS2013

Assessing the Temperature Dependence of Narrow-Band Raman Water Vapor Lidar Measurements: A Practical Approach

Narrow-band detection of the Raman water vapor spectrum using the lidar technique introduces a concern over the temperature dependence of the Raman spectrum. Various groups have addressed this issue either by trying to minimize the temperature dependence to the point where it can be ignored or by correcting for whatever degree of temperature dependence exists. The traditional technique for performing either of these entails accurately measuring both the laser output wavelength and the water vapor spectral passband with combined uncertainty of approximately 0.01 nm. However, uncertainty in interference filter center wavelengths and laser output wavelengths can be this large or larger. These combined uncertainties translate into uncertainties in the magnitude of the temperature dependence of the Raman lidar water vapor measurement of 3% or more. We present here an alternate approach for accurately determining the temperature dependence of the Raman lidar water vapor measurement. This alternate approach entails acquiring sequential atmospheric profiles using the lidar while scanning the channel passband across portions of the Raman water vapor Q-branch. This scanning is accomplished either by tilt-tuning an interference filter or by scanning the output of a spectrometer. Through this process a peak in the transmitted intensity can be discerned in a manner that defines the spectral location of the channel passband with respect to the laser output wavelength to much higher accuracy than that achieved with standard laboratory techniques. Given the peak of the water vapor signal intensity curve, determined using the techniques described here, and an approximate knowledge of atmospheric temperature, the temperature dependence of a given Raman lidar profile can be determined with accuracy of 0.5% or better. A Mathematica notebook that demonstrates the calculations used here is available from the lead author.

Raman lidar↗