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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 253 records · Page 14
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NASA NTRS2000

BOREAS HYD-3 Subcanopy Incoming Solar Radiation Measurements

The Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-3 team collected several data sets related to the hydrology of forested areas. This data set contains solar radiation measurements from several pyranometers (solar radiometers) placed on the snow surface in jack pine (1994) and black spruce and aspen forests (1996) in the BOREAS southern study area (SSA). An array of radiometers was used to collect data for three to four consecutive days in each forest type to study the hypothesis that energy transfer and snow water equivalent would vary spatially as a function of canopy closure. The quality of the data is good, because the days were generally clear and the radiometers were checked daily to remove anything that landed on the radiometers. The data are available in tabular ASCII files. The subcanopy incoming solar radiation measurement data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Hardy, Janet P.↗
NASA NTRS2008

An Analytical Model for the Prediction of a Micro-Dosimeter Response Function

A rapid analytical procedure for the prediction of a micro-dosimeter response function in low Earth orbit (LEO), correlated with the Space Transportation System (STS, shuttle) Tissue Equivalent Proportional Counter (TEPC) measurements is presented. The analytical model takes into consideration the energy loss straggling and chord length distribution of the detector, and is capable of predicting energy deposition fluctuations in a cylindrical micro-volume of arbitrary aspect ratio (height/diameter) by incoming ions through both direct and indirect (ray) events. At any designated (ray traced) target point within the vehicle, the model accepts the differential flux spectrum of Galactic Cosmic Rays (GCR) and/or trapped protons at LEO as input. On a desktop PC, the response function of TEPC for each ion in the GCR/trapped field is computed at the average rate of 30 seconds/ion. The ionizing radiation environment at LEO is represented by O'Neill fs GCR model (2004), covering charged particles in the 1 less than or equal to Z less than or equal to 28. O'Neill's free space GCR model is coupled with the Langley Research Center (LaRC) angular dependent geomagnetic cutoff model to compute the transmission coefficient in LEO. The trapped proton environment is represented by a LaRC developed time dependent procedure which couples the AP8MIN/AP8MAX, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment is represented by the extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. The charged particle transport calculations correlated with STS 51 and 114 flights are accomplished by using the most recent version (2005) of the LaRC deterministic High charge (Z) and Energy TRaNsport (HZETRN) code. We present the correlations between the TEPC model predictions (response function) and TEPC measured differential/integral spectra in the lineal energy (y) domain for both GCR and trapped protons, with the conclusion that the model correctly accounts for the increase in flux at low y values where energetic ions are the primary contributor. We further discuss that, even with the incorporation of angular dependency in the cutoffs, comparison of the GCR differential/integral flux between STS 51 and 114 TEPC measured data and current calculations indicates that there still exists an underestimation by the simulations at low to mid range y values. This underestimation is partly related the exclusion of the secondary pion particle production from the current version of HZETRN.

Badavi, Francis F.↗
NASA NTRS1972

The radiation budget of the earth-atmosphere system as measured from the Nimbus 3 satellite /1969-1970/.

Data from the Medium Resolution Infrared Radiometer (MRIR) experiment on Nimbus 3 have provided global radiance measurements during four seasons (April 1969-February 1970). From these data, values of the total radiation budget of the earth-atmosphere system were derived on varying time and space scales and were compared with previous satellite measurements and theoretical computations. Results confirm earlier satellite measurements. They show a warmer and darker planet than was previously believed. In addition, the Nimbus 3 data offer the first medium resolution views of both the Northern and Southern Hemispheres' radiation budgets during all seasons.

Vonder Haar, T. H.↗
NASA NTRS1998

Infrared Measurements of Atmospheric Constituents

This research program studies atmospheric trace gas concentrations and altitude distributions, particularly for those gases that are important in stratospheric chemistry and radiative balance. Measurements are made with infrared remote sensing instruments, either ground based or balloon-borne. Most of the ground based instruments are part of the Network for Detection of Stratospheric Change (NDSC), including a very high spectral resolution solar absorption spectrometer at Mauna Loa Observatory and similar system at McMurdo Station, Antarctica (operated in collaboration with the New Zealand NIWA). Additionally, we are deriving stratospheric constituent data from the spectra obtained at the DOE Atmospheric Radiation Measurements (ARM) program's site in north-central Oklahoma. We have an atmospheric emission spectrometer system at the South Pole (with additional support from NSF), and an identical NSF support instrument at Eureka, NWT, Canada. Our balloon-borne instruments include a very high resolution solar absorption spectrometer system, a smaller, slightly lower resolution solar spectrometer system, a high resolution atmospheric emission spectrometer, and several medium resolution emission spectrometers (CAESRs) that are usually flown piggyback. During the past year, we participated in the MANTRA balloon flight from Saskatoon, Saskatchewan, with the high resolution solar spectrometer system. Several of our instruments were extensively compared to (UARS) Upper Atmosphere Research Satellite observations, and so provide a data set with known connections to UARS. In the longer term, the data can be used to relate UARS data to (EOS) Earth Observing System and (ADEOS) Advanced Airborne Earth Observing System.

Frank J Murcray↗
NASA NTRS1982

Radiative flux measurements in the troposphere

A new airborne radiometric system with a time resolution as high as 60 msec has been designed for measuring radiative fluxes in the atmosphere. To verify the instrument performance, the solar constant at the top of the atmosphere has been calculated using the radiative flux densities measured in the troposphere, and the result obtained has been found to agree with the standard value to within 4%. Total heating rates of 0.175 and 0.377 K/h have been determined for hazy and foggy atmospheres, respectively, and aerosol heating rates of 0.065 and 0.235 K/h have been deduced from the total heating rates.

Valero, F. P. J.↗
NASA NTRS2003

[Results for SHEBA/FIRE]

The Atmospheric Research Laboratory's Radiation Measurement System (RAMS) was on the NCAR C-130 aircraft in May and July 1998, collecting radiometric data on the science flights conducted in the vicinity of the Surface Heat Budget of the Arctic Ocean (SHEBA) ship. These measurements were part of the FIRE Arctic Cloud Experiment (FIRE ACE). Analysis of some of the data focused on the absorption, reflection, and transmittance of Arctic clouds, especially compared to model results. In order to assess the absorption of solar radiation by the clear and cloudy atmosphere in the Arctic the measurements from the radiometers were combined in pairs of above-cloud segments and below-cloud segments. To get these pairs, the data for all sixteen of the flights (8 in May and 8 in July) were examined for occurrences of low-altitude segments in proximity to high-altitude segments. The low-altitude data are then treated as measurements of the bottom of a layer and the high-altitude data are taken as measurements of the top of the layer. With measurements of the upwelling and downwelling irradiances above and below a layer one can determine the reflectance, transmittance, and absorptance of the layer. Attachment: Doelling, D.R., P. Minnis, D.A. Spangenberg, V. Chakrapani, A. Mahesh, S.K. Pope, and F.P.J. Valero, Cloud radiative forcing at the top of the atmosphere during FIRE ACE derived from AVHRR data, J. Geophys. Res. 106, 15,279-15,296,2001. Minnis, P., D.R. Doelling, D.A. Spangenberg, A. Mahesh, S.K. Pope, and F.P.J. Valero, AVHRR-derived cloud radiative forcing over the ARM NSA and SHEBA site during FIRE ACE, abstract submitted to the ARM Science Team Meeting, San Antonio, TX, M a . 13-17,2000. Pope, S.K., and F.P.J. Valero, Measured and modeled radiometric fluxes in the Arctic during FIRE-ACE, presented as a poster at the American Geophysical Union meeting, San Francisco, CA, Dec. 13-17, 1999. Pope, S.K., and F.P.J. Valero, Measured and modeled radiometric fluxes in the Arctic during FIRE-ACEy paper presented at SHEBA/FIRE Workshop, National Center for Atmospheric Research, Boulder, Colo., Apr. 17-20,2000.

Valero, Francisco P. J.↗
NASA NTRS2004

High Altitude Radiations Relevant to the High Speed Civil Transport (HSCT)

The Langley Research Center (LaRC) performed atmospheric radiation studies under the SST development program in which important ionizing radiation components were measured and extended by calculations to develop the existing atmospheric ionizing radiation (AIR) model. In that program the measured neutron spectrum was limited to less than 10 MeV by the available 1960-1970 instrumentation. Extension of the neutron spectrum to high energies was made using the LaRC PROPER-3C monte carlo code. It was found that the atmospheric neutrons contributed about half of the dose equivalent and approximately half of the neutron contribution was from high energy neutrons above 10 MeV. Furthermore, monte carlo calculations of solar particle events showed that potential exposures as large as 10-100 mSv/hr may occur on important high latitude routes but acceptable levels of exposure could be obtained if timely descent to subsonic altitudes could be made. The principal concern was for pregnant occupants onboard the aircraft. As a result of these studies the FAA Advisory Committee on the Radiobiological Aspects of the SST recommended: 1. Crew members will have to be informed of their exposure levels 2. Maximum exposures on any flight to be limited to 5 mSv 3. Airborne radiation detection devices for total exposure and exposure rates 4. Satellite monitoring system to provide SST aircraft real-time information on atmospheric radiation levels for exposure mitigation 5. A solar forecasting system to warn flight operations of an impending solar event for flight scheduling and alert status. These recommendations are a reasonable starting point to requirements for the HSCT with some modification reflecting new standards of protection as a result of changing risk coefficients.

Wilson, J. W.↗
NASA NTRS1997

Finite Difference Radiative Transfer Model Calculations Compared to Measurements at the Top and Bottom of the Atmosphere

A finite difference radiative transfer program was developed to handle most anisotropic scattering and reflectance problems encountered in the Earth's atmospheric system. The model has been used to reproduce the radiance received by both satellite and ground based radiation measuring instruments. It accurately replicates the radiance measured by both narrow and wide field-of-view instruments with either narrow or broadband wavelength ranges located on the surface and at satellite altitudes. The output of the finite difference code is compared to the measurements by surface pyranometers and a spectroradiometer aboard a high flying aircraft. The program output is also compared to ERBE measurements aboard the ERBS and NOAA-9 satellites as well as the visible bands aboard the GOES-6 and GOES-7 satellites and AVHRR bands 1 and 2 of the NOAA-9 and NOAA-1 1 satellites. The model is within 0.2 % of the radiance received by pyranometers, within 0.6 % of the ERBE radiances, and within 3 % of the radiances measured by the visible bands of the GOES and NOAA AVHRR radiometers.

LeCroy, Stuart R.↗
NASA NTRS2004

How Well are Recent Climate Variability Signals Resolved by Satellite Radiative Flux Estimates?

One notable aspect of Earth s climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. Understanding the character of radiative flux estimates and relating them to variations in other energy fluxes and climate state variables is key to improving our understanding of climate. In this work we will evaluate several recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project FD radiative flux profiles are available from rnid-1983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and HlRS operational soundings profiles. Full and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NASA/Goddard Earth Observing System assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. Several estimates of downward LW flux at the surface inferred from microwave data are also examined. Since these products have been evaluated with Baseline Surface Radiation Network data over land we focus over ocean regions and use the DOE/NOAA/NASA Shipboard Ocean Atmospheric Radiation (SOAR) surface flux measurements to characterize performance of these data sets under both clear and cloudy conditions. Some aspects of performance are stratified according to SST and vertical motion regimes. Comparisons to the TRMM/CERES SRB data in 1998 are also interpreted. These radiative fluxes are then analyzed to determine how surface (and TOA) radiative exchanges respond to interannual signals of ENS0 warm and cold events. Our analysis includes regional changes as well as integrated signals over land, ocean and various latitude bands. Changes in water vapor and cloud forcing signatures are prominent on interannual time scales. Prominent signals are also found in the SW fluxes for the Pinatubo volcanic event. These systematic changes in fluxes are related to changes in large-scale circulations and energy transport in the atmosphere and ocean. Some estimates of signal-to-noise and reliability are discussed to place our results in context.

Robertson, Franklin R.↗
NASA NTRS2008

Radiation Protection Effectiveness of Polymeric Based Shielding Materials at Low Earth Orbit

Correlations of limited ionizing radiation measurements onboard the Space Transportation System (STS; shuttle) and the International Space Station (ISS) with numerical simulations of charged particle transport through spacecraft structure have indicated that usage of hydrogen rich polymeric materials improves the radiation shielding performance of space structures as compared to the traditionally used aluminum alloys. We discuss herein the radiation shielding correlations between measurements on board STS-81 (Atlantis, 1997) using four polyethylene (PE) spheres of varying radii, and STS-89 (Endeavour, 1998) using aluminum alloy spheres; with numerical simulations of charged particle transport using the Langley Research Center (LaRC)-developed High charge (Z) and Energy TRaNsport (HZETRN) algorithm. In the simulations, the Galactic Cosmic Ray (GCR) component of the ionizing radiation environment at Low Earth Orbit (LEO) covering ions in the 1< or equals Z< or equals 28 range is represented by O'Neill's (2004) model. To compute the transmission coefficient for GCR ions at LEO, O'Neill's model is coupled with the angular dependent LaRC cutoff model. The trapped protons/electrons component of LEO environment is represented by a LaRC-developed time dependent procedure which couples the AP8min/AP8max, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment resulting from interaction of GCR ions with upper atmosphere is modeled through extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. With the validity of numerical simulations through correlation with PE and aluminum spheres measurements established, we further present results from the expansion of the simulations through the selection of high hydrogen content commercially available polymeric constituents such as PE foam core and Spectra fiber(Registered TradeMark) composite face sheet to assess their radiation shield properties as compared to generic PE.

Badavi, Francis F.↗
NASA NTRS1977

Ultraviolet spectrometer experiment for the Voyager mission

An objective grating spectrometer covering the wavelength range of 500 to 1700 A with a 10-A resolution is employed for the Voyager ultraviolet spectrometer experiment. In determining the composition and structure of the atmospheres of Saturn, Jupiter and several satellites, the ultraviolet spectrometer will rely on airglow mode observations to measure radiation from the atmospheres due to resonant scattering of solar flux, and the occultation mode for assessments of the atmospheric extinction of solar or stellar radiation as the spacecraft enters shadow zones. Since it is capable of prolonged stellar observations in the 500 to 1000 A wavelength range, the spectrometer is expected to make important contributions to exploratory studies of UV sources.

Broadfoot, A. L.↗
NASA NTRS2007

Variability in Global Top-of-Atmosphere Shortwave Radiation Between 2000 and 2005

Measurements from various instruments and analysis techniques are used to directly compare changes in Earth-atmosphere shortwave (SW) top-of-atmosphere (TOA) radiation between 2000 and 2005. Included in the comparison are estimates of TOA reflectance variability from published ground-based Earthshine observations and from new satellite-based CERES, MODIS and ISCCP results. The ground-based Earthshine data show an order-of-magnitude more variability in annual mean SW TOA flux than either CERES or ISCCP, while ISCCP and CERES SW TOA flux variability is consistent to 40%. Most of the variability in CERES TOA flux is shown to be dominated by variations global cloud fraction, as observed using coincident CERES and MODIS data. Idealized Earthshine simulations of TOA SW radiation variability for a lunar-based observer show far less variability than the ground-based Earthshine observations, but are still a factor of 4-5 times more variable than global CERES SW TOA flux results. Furthermore, while CERES global albedos exhibit a well-defined seasonal cycle each year, the seasonal cycle in the lunar Earthshine reflectance simulations is highly variable and out-of-phase from one year to the next. Radiative transfer model (RTM) approaches that use imager cloud and aerosol retrievals reproduce most of the change in SW TOA radiation observed in broadband CERES data. However, assumptions used to represent the spectral properties of the atmosphere, clouds, aerosols and surface in the RTM calculations can introduce significant uncertainties in annual mean changes in regional and global SW TOA flux.

Loebe, Norman G.↗
NASA NTRS1977

Solar mesosphere explorer: Experiment description

The Solar Mesosphere Explorer (SME) satellite experiments will provide a comprehensive study of atmospheric ozone and the processes which form and destroy it. Five instruments to be carried on the spacecraft will measure the ozone density and altitude distribution, monitor the incoming solar radiation, and measure other atmospheric constituents which affect ozone. The investigative approach concept, methods and procedures, preflight studies, and orbits and mission lifetime are presented. Descriptions of the instruments are also presented.

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