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Results for “Radiative Parameters”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Modelling the performance of the monogroove with screen heat pipe for use in the radiator of the solar dynamic power system of the NASA Space Station

A computer code to model the steady-state performance of a monogroove heat pipe for the NASA Space Station is presented, including the effects on heat pipe performance of a screen in the evaporator section which deals with transient surges in the heat input. Errors in a previous code have been corrected, and the new code adds additional loss terms in order to model several different working fluids. Good agreement with existing performance curves is obtained. From a preliminary evaluation of several of the radiator design parameters it is found that an optimum fin width could be achieved but that structural considerations limit the thickness of the fin to a value above optimum.

Evans, Austin Lewis↗
NASA NTRS1989

Structures for remotely deployable precision antennas

Future space missions such as the Earth Science Geostationary Platform (ESGP) will require highly accurate antennas with apertures that cannot be launched fully formed. The operational orbits are often inaccessible to manned flight and will involve expendable launch vehicles such as the Delta or Titan. There is therefore a need for completely deployable antenna reflectors of large size capable of efficiently handling millimeter wave electromagnetic radiation. The parameters for the type of mission are illustrated. The logarithmic plot of frequency versus aperture diameter shows the regions of interest for a large variety of space antenna applications, ranging from a 1500-meter-diameter radio telescope for low frequencies to a 20-meter-diameter infrared telescope. For the ESGP, a major application is the microwave radiometry at high frequencies for atmospheric sounding. Almost all existing large antenna reflectors for space employ a mesh-type reflecting surface. Examples are shown and discussed which deal with the various structural concepts for mesh antennas. Fortunately, those concepts are appropriate for creating the very large apertures required at the lower frequencies for good resolution. The emphasis is on the structural concepts and technologies that are appropriate to fully automated deployment of dish-type antennas with solid reflector surfaces. First the structural requirements are discussed. Existing concepts for fully deployable antennas are then described and assessed relative to the requirements. Finally, several analyses are presented that evaluate the effects of beam steering and segmented reflector design on the accuracy of the antenna.

Hedgepeth, J. M.↗
NASA NTRS1989

Results from the Earth Radiation Budget Experiment (ERBE)

The Earth Radiation Budget Experiment (ERBE) has been observing the earth during the past 4 years from three satellites. Numerous validation procedures have been applied to the data. Particularly important have been intercomparisons between three channels of scanning radiometers and wide and medium field-of-view radiometers. These intercomparisons and onboard calibration targets have provided assurance of high data quality. In addition to the classic radiation budget parameters: global absorbed and emitted energy, ERBE is producing fluxes on scales of 250 km that can significantly increase understanding of the earth's climate. Of particular interest are ERBE measurements of clear-sky albedos and longwave fluxes, which are part of the ERBE data products. Use of data from the precessing ERBE satellite together with data from the sun-synchronous NOAA-9 and NOAA-10 satellites also provides information on the diurnal cycle of shortwave and longwave fluxes.

Barkstrom, Bruce R.↗
NASA NTRS1989

Interannual variability of the earth's climate during the last decade as observed by the Nimbus-7 spacecraft

A set of earth radiation budget observations spanning the time period 1979 to 1987 is considered. A diurnally averaged eight year top-of-the-atmosphere net radiation field is analyzed along with a zonally averaged radiation budget. Variability in the net radiation due to changes in the clear sky shortwave and longwave radiation fields or changes in the total cloudiness distribution and the cloud properties is assessed, along with those radiation-budget parameters key to the earth's heat balance.

Kyle, H. Lee↗
NASA NTRS1994

Multi-wavelength profiles of aerosol backscatter over Lauder, New Zealand, 24 November 1992

Simultaneous profiles of aerosol backscatter ratio were measured over Lauder, New Zealand (45 deg S, 170 deg E) on the night of November 24, 1992. Instrumentation comprised two complementary lidar systems and a backscattersonde, to give measurements at wavelengths 351, 490, 532, and 940 nm. The data from the lidars and the backscattersonde were self-consistent, enabling the wavelength dependence of aerosol backscatter to be determined as a function of altitude. This wavelength-dependence is a useful parameter in radiative transfer calculations. In the stratosphere, the average wavelength exponent between 351 and 940 nm was -1.23 +/- 0.1, which was in good agreement with values derived from measured physical properties of aerosols.

Mckenzie, R. L.↗
NASA NTRS1995

Hydrodynamics of coalescing binary neutron stars: Ellipsoidal treatment

We employ an approximate treatment of dissipative hydrodynamics in three dimensions to study the coalescence of binary neutron stars driven by the emission of gravitational waves. The stars are modeled as compressible ellipsoids obeying a polytropic equation of state; all internal fluid velocities are assumed to be linear functions of the coordinates. The hydrodynamics equations then reduce to a set of coupled ordinary differential equations for the evolution of the principal axes of the ellipsoids, the internal velocity parameters, and the binary orbital parameters. Gravitational radiation reaction and viscous dissipation are both incorporated. We set up exact initial binary equilibrium configurations and follow the transition from the quasi-static, secular decay of the orbit at large separation to the rapid dynamical evolution of the configurations just prior to contact. A hydrodynamical instability resulting from tidal interactions significantly accelerates the coalescence at small separation, leading to appreciable radial infall velocity and tidal lag angles near contact. This behavior is reflected in the gravitational waveforms and may be observable by gravitational wave detectors under construction. In cases where the neutron stars have spins which are not aligned with the orbital angular momentum, the spin-induced quadrupole moment can lead to precession of the orbital plane and therefore modulation of the gravitational wave amplitude even at large orbital radius. However, the amplitude of the modulation is small for typical neutron star binaries with spins much smaller than the orbital angular momentum.

Lai, Dong↗
NASA NTRS2003

Adaptation of SUBSTOR for controlled-environment potato production with elevated carbon dioxide

The SUBSTOR crop growth model was adapted for controlled-environment hydroponic production of potato (Solanum tuberosum L. cv. Norland) under elevated atmospheric carbon dioxide concentration. Adaptations included adjustment of input files to account for cultural differences between the field and controlled environments, calibration of genetic coefficients, and adjustment of crop parameters including radiation use efficiency. Source code modifications were also performed to account for the absorption of light reflected from the surface below the crop canopy, an increased leaf senescence rate, a carbon (mass) balance to the model, and to modify the response of crop growth rate to elevated atmospheric carbon dioxide concentration. Adaptations were primarily based on growth and phenological data obtained from growth chamber experiments at Rutgers University (New Brunswick, N.J.) and from the modeling literature. Modified-SUBSTOR predictions were compared with data from Kennedy Space Center's Biomass Production Chamber for verification. Results show that, with further development, modified-SUBSTOR will be a useful tool for analysis and optimization of potato growth in controlled environments.

NASA Discipline Life Support Systems↗
NASA NTRS1986

Quality assurance procedures for environmental control and monitoring in plant growth facilities. Report of the North Central Regional 101 Committee on Growth Chamber Use

This report includes procedures for ensuring the quality of the environment provided for plant growth in controlled environment facilities. Biologists and engineers may use these procedures for ensuring quality control during experiments or for ensuring quality control in the design of plant growth facilities. Environmental monitoring prior to and during experiments is included in these procedures. Specific recommendations cover control, acquisition, and calibration for sensor types for the separate parameters of radiation (light), temperature, humidity, carbon dioxide, and air movement.

NASA Discipline Number 61-10↗
NASA NTRS2009

Identifying the Molecular Origin of Global Warming

We have investigated the physical characteristics of greenhouse gases (GHGs) to assess which properties are most important in determining the efficiency of a GHG. Chlorofluorcarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), nitrogen fluorides, and various other known atmospheric trace molecules have been included in this study. Compounds containing the halogens F or Cl have in common very polar X-F or X-Cl bonds, particularly the X-F bonds. It is shown that as more F atoms bond to the same central atom, the bond dipoles become larger as a result of the central atom becoming more positive. This leads to a linear increase in the total or integrated XF bond dipole derivatives for the molecule, which leads to a non-linear (quadratic) increase in infrared (IR) intensity. Moreover, virtually all of the X-F bond stretches occur in the atmospheric IR window as opposed to X-H stretches, which do not occur in the atmospheric window. It is concluded that molecules possessing several F atoms will always have a large radiative forcing parameter in the calculation of their global warming potential. Some of the implications for global warming and climate change are discussed.

Bera, Partha P.↗
NASA NTRS2015

Overview of the Airborne Tropical TRopopause EXperiment (ATTREX)

The NASA Airborne Tropical TRopopause EXperiment (ATTREX) is a series of airborne campaigns focused on understanding physical processes in the Tropical Tropopause Layer (TTL) and their role in atmospheric chemistry and climate. ATTREX is using the high-altitude, long-duration NASA Global Hawk Unmanned Air System to make in situ and remote-sensing measurements spanning the Pacific. A particular ATTREX emphasis is to better understand the dehydration of air as it passes through the cold tropical tropopause region. The ATTREX payload contains 12 in situ and remote sensing instruments that measure water vapor, clouds, multiple gaseous tracers (CO, CO2, CH4, NMHC, SF6, CFCs, N2O), reactive chemical compounds (O3, BrO, NO2), meteorological parameters, and radiative fluxes. ATTREX flight series have been conducted in the fall of 2011 from Armstrong Flight Research Center (AFRC) in California, in the winter of 2013 from AFRC, and in the winter/spring of 2014 from Guam. The first two flight series provided extensive sampling of the central and eastern Pacific, whereas the last flight series permitted sampling in the western Pacific. The sampling strategy has primarily involved repeated ascents and descents through the depth of the TTL (about 13-19 km). Over 100 TTL profiles were obtained on each flight series. The ATTREX dataset includes TTL water vapor measurements with unprecedented accuracy, ice crystal size distributions and habits. The cloud and water measurements provide unique information about TTL cloud formation, the persistence of super-saturation with respect to ice, and dehydration. The plethora of tracers measured on the Global Hawk flights are providing unique information about TTL transport pathways and time scales. The meteorological measurements are revealing dynamical phenomena controlling the TTL thermal structure, and the radiation measurements are providing information about heating rates associated with TTL clouds and water vapor. This presentation will provide an overview of the ATTREX flights, examples of measurements from the flights, and plans for modeling/analysis of the ATTREX dataset.

ATTREX↗
NASA NTRS2014

Overview of the Airborne Tropical TRopopause EX

The NASA Airborne Tropical TRopopause EXperiment (ATTREX) is a series of airborne campaigns focused on understanding physical processes in the Tropical Tropopause Layer (TTL) and their role in atmospheric chemistry and climate. ATTREX is using the high-altitude, long-duration NASA Global Hawk Unmanned Air System to make in situ and remote-sensing measurements spanning the Pacific. A particular ATIREX emphasis is to better understand the dehydration of air as it passes through the cold tropical tropopause region. The ATTREX payload contains 12 in situ and remote sensing instruments that measure water vapor, clouds, multiple gaseous tracers (CO, CO2, CH4, NMHC, SF6, CFCs, N2O), reactive chemical compounds (O3, BrO, NO2), meteorological parameters, and radiative fluxes. ATTREX flight series have been conducted in the fall of 2011 from Armstrong Flight Research Center (AFRC) in California, in the winter of 2013 from AFRC, and in the winter/spring of 2014 from Guam. The first two f light series provided extensive sampling of the central and eastern Pacific, whereas the last flight series permitted sampling in the western Pacific. The sampling strategy has primarily involved repeated ascents and descents through the depth of the TTL (about 13-19 km). Over 100 TTL profiles were obtained on each flight series. The ATTREX dataset includes TTL water vapor measurements with unprecedented accuracy, ice crystal size distributions and habits. The cloud and water measurements provide unique information about TTL cloud formation, the persistence of supersaturation with respect to ice, and dehydration. The plethora of tracers measured on the Global Hawk flights are providing unique information about TTL transport pathways and time scales. The meteorological measurements are revealing dynamical phenomena controlling the TTL thermal structure, and the radiation measurements are providing information about heating rates associated with TTL clouds and water vapor. This presentation will provide an overview of the ATTREX flights, examples of measurements from the flights, and plans for modeling/analysis of the ATTREX dataset.

Airborne↗
NASA NTRS2016

Tropospheric Emissions: Monitoring of Pollution (TEMPO)

TEMPO (Tropospheric Emissions: Monitoring of Pollution) was selected in 2012 by NASA as the first Earth Venture Instrument, for launch between 2018 and 2021. It will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO observes from Mexico City, Cuba, and the Bahamas to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution (approximately 2.1 kilometers N/S by 4.4 kilometers E/W at 36.5 degrees N, 100 degrees W). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry, as well as contributing to carbon cycle knowledge. Measurements are made hourly from geostationary (GEO) orbit, to capture the high variability present in the diurnal cycle of emissions and chemistry that are unobservable from current low-Earth orbit (LEO) satellites that measure once per day. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a commercial GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), formaldehyde (H2CO), glyoxal (C2H2O2), bromine monoxide (BrO), IO (iodine monoxide),water vapor, aerosols, cloud parameters, ultraviolet radiation, and foliage properties. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides these near-real-time air quality products that will be made publicly available. TEMPO will launch at a prime time to be the North American component of the global geostationary constellation of pollution monitoring together with the European Sentinel-4 (S4) and Korean Geostationary Environment Monitoring Spectrometer (GEMS) instruments.

tropospheric measurement suite↗
NASA NTRS2017

Modelling the Passive Microwave Signature from Land Surfaces: A Review of Recent Results and Application to the L-Band SMOS SMAP Soil Moisture Retrieval Algorithms

Two passive microwave missions are currently operating at L-band to monitor surface soil moisture (SM) over continental surfaces. The SMOS sensor, based on an innovative interferometric technology enabling multi-angular signatures of surfaces to be measured, was launched in November 2009. The SMAP sensor, based on a large mesh reflector 6 m in diameter providing a conically scanning antenna beam with a surface incidence angle of 40deg, was launched in January of 2015. Over the last decade, an intense scientific activity has focused on the development of the SM retrieval algorithms for the two missions. This activity has relied on many field (mainly tower-based) and airborne experimental campaigns, and since 2010-2011, on the SMOS and Aquarius space-borne L-band observations. It has relied too on the use of numerical, physical and semi-empirical models to simulate the microwave brightness temperature of natural scenes for a variety of scenarios in terms of system configurations (polarization, incidence angle) and soil, vegetation and climate conditions. Key components of the inversion models have been evaluated and new parameterizations of the effects of the surface temperature, soil roughness, soil permittivity, and vegetation extinction and scattering have been developed. Among others, global maps of select radiative transfer parameters have been estimated very recently. Based on this intense activity, improvements of the SMOS and SMAP SM inversion algorithms have been proposed. Some of them have already been implemented, whereas others are currently being investigated. In this paper, we present a review of the significant progress which has been made over the last decade in this field of research with a focus on L-band, and a discussion on possible applications to the SMOS and SMAP soil moisture retrieval approaches.

SMOS↗
NASA NTRS2019

The New NASA Ames Infrared Optical Constant Facility. Determinations for Titan Aerosol-, and Exoplanet and Brown Dwarf Cloud Particle Analogs

Here we present a new optical constant facility developed at NASA Ames that will allow the determination of optical constants in the infrared of various materials, analogs of hazes and cloud particles in (exo)planet atmospheres and brown dwarfs. Our facility is composed of a Fourier Transform Infrared (FTIR) spectrometer continuously covering the Near-IR, mid-IR and Far-IR range (from 0.74 to 200 µm), coupled to variable angle transmittance and reflectance accessories that allow the characterization of the scattering properties of nonhomogeneous samples (laboratory planetary aerosol analogs, films, slabs of material, crystals, powders...) over a wide incidence and emittance angle range (0-90 degrees). This permits the angular light distribution in both transmission and reflection measurements to be characterized, enabling the determination of the complex indices of refraction, n and k, over the full NIR-FIR range via modeling of the laboratory observations. The resulting refractive indices are critical input parameters in radiative transfer models, exoplanet and brown dwarf cloud models, protoplanetary disk simulations and other models used for the interpretation of observational data from past, current and future (exo)planetary NASA missions. We will present preliminary data obtained on Titan aerosol analogs produced in the Titan Haze Simulation (THS) experiment on COSmIC, a unique experimental platform developed at NASA Ames that allows the simulation of Titan's complex atmospheric chemistry at Titan-like temperature (200 K). We will also introduce a new study of the optical properties of ammonium-bearing phosphates, potential cloud particles forming in temperate exoplanets and brown dwarfs.

Planetary Science↗
NASA NTRS2015

Overview of the NASA Airborne Tropical TRopopause EXperiment (ATTREX)

The NASA Airborne Tropical TRopopause EXperiment (ATTREX) is a series of airborne campaigns focused on understanding physical processes in the Tropical Tropopause Layer (TTL) and their role in atmospheric chemistry and climate. ATTREX is using the high-altitude, long-duration NASA Global Hawk Unmanned Air System to make in situ and remote-sensing measurements spanning the Pacific. A particular ATTREX emphasis is to better understand the dehydration of air as it passes through the cold tropical tropopause region. The ATTREX payload contains 12 in situ and remote sensing instruments that measure water vapor, clouds, multiple gaseous tracers (CO, CO2, CH4, NMHC, SF6, CFCs, N2O), reactive chemical compounds (O3, BrO, NO2), meteorological parameters, and radiative fluxes.ATTREX flight series have been conducted in the fall of 2011 from Armstrong Flight Research Center (AFRC) in California, in the winter of 2013 from AFRC, and in the winterspring of 2014 from Guam. The first two flight series provided extensive sampling of the central and eastern Pacific, whereas the last flight series permitted sampling in the western Pacific. The sampling strategy has primarily involved repeated ascents and descents through the depth of the TTL (about 13-19 km). Over 100 TTL profiles were obtained on each flight series. The ATTREX dataset includes TTL water vapor measurements with unprecedented accuracy, ice crystal size distributions and habits. The cloud and water measurements provide unique information about TTL cloud formation, the persistence of supersaturation with respect to ice, and dehydration. The plethora of tracers measured on the Global Hawk flights are providing unique information about TTL transport pathways and time scales. The meteorological measurements are revealing dynamical phenomena controlling the TTL thermal structure, and the radiation measurements are providing information about heating rates associated with TTL clouds and water vapor.This presentation will provide an overview of the ATTREX flights, examples of measurements from the flights, and plans for modelinganalysis of the ATTREX dataset.

Jensen, Eric J.↗
NASA NTRS2019

OMH3075 Hall Effect Sensor Total Ionizing Dose Test Report

The purpose of this test was to characterize the OMH3075 Hall Effects sensor degradation for total dose response. The device samples were exposed to low dose irradiations using gamma radiation. Device parameters such as magnetic operating points, leakage currents, supply currents, and rise and fall times were investigated.

Forney, James↗
NASA NTRS2019

Introducing NASA Ames' New Infrared Optical Constant Facility. Determinations of Complex Refractive Indices for Titan Aerosol Analogs and Other Applications

A new optical constant facility has been developed at NASA Ames that will allow the determination of optical constants in the infrared of various materials, analogs of (exo)planetary hazes and cloud particles. Our facility is composed of a Fourier Transform Infrared (FTIR) spectrometer continuously covering the Near-IR to Far-IR range (from 0.74 to 200 μm), coupled to variable angle transmittance and reflectance accessories that allow the characterization of the scattering properties of non-homogeneous samples (laboratory (exo)planetary aerosol analogs, films, slabs of material, crystals, powders, etc.) over a wide incidence and emittance angle range (0-90 degrees). This new experimental setup allows the characterization of angular light distribution in both transmission and reflection measurements, and enables the determination of the complex indices of refraction, n and k, over the full NIR-FIR range via modeling of the laboratory measurements. The resulting refractive indices are critical input parameters in radiative transfer models, microphysical models, cloud models, protoplanetary disk simulations and other models used for the interpretation of observational data from past, current and future (exo)planetary NASA missions. Here we present a description of the facility along with the first determination of optical constants for Titan aerosol analogs produced in the Titan Haze Simulation (THS) experiment on COSmIC, a unique experimental setup developed at NASA Ames that allows the simulation of Titan’s complex atmospheric chemistry at Titan-like temperature (200 K). We also introduce a new study of the optical properties of ammonium-bearing phosphates, potential cloud particles forming in temperate exoplanets and brown dwarfs.

Sciamma-O'Brien, Ella M.↗
NASA NTRS2018

NISAR L-Band and S-Band Instrument Antennas: Compatibility Test and Results

Abstract—NASA ISRO SAR (NISAR) is one of the next major Earth science flight projects that NASA is currently developing in collaboration with ISRO, the Indian Space Research Organization. Featuring a 12m deployable off-set reflector, similar to SMAP but twice as large, and a dual band, dual polarization feed array, NISAR will measure with great accuracy even the smallest changes on our planet’s landmass, ice-sheet and forests over a 3 year period with a 12-day repeat cycle everywhere on the globe. Two radar systems will be sharing the same reflector, one operating in L-Band and one in S-Band. While the L-Band radar and feed antenna are being developed at Jet Propulsion Laboratory (JPL) for NASA, the S-Band feed antenna is under development at the Space Application Centre (SAC) in Ahmedabad, India, for ISRO. This paper describes the tests that were carried out both at JPL and SAC in order to verify that the level of compatibility between the two feed antennas were within the allocated requirements. Both S-parameters and radiation patterns were measured and compared with calculated predictions.

Harrell, Jefferson A.↗