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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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NASA NTRS1980

Gravity fields of the terrestrial planets - Long-wavelength anomalies and tectonics

The paper discusses the gravity and topography data available for four terrestrial planets (earth, moon, Mars, and Venus), with particular emphasis on drawing inferences regarding the relationship of long-wavelength anomalies to tectonics. The discussion covers statistical analyses of global planetary gravity fields, relationship of gravity anomalies to elastic and viscoelastic models, relationship of gravity anomalies to convection models, finite strength, and isostasy (or the state of isostatic compensation). The cases of the earth and the moon are discussed in some detail. A summary of comparative planetology is presented.

Phillips, R. J.↗
NASA NTRS1982

Comparisons of free-flight experimental and predicted heating rates for the Space Shuttle

Experimental windward-ray heating rates measured during entry of the first Space Shuttle Orbiter mission are compared with predicted rates based on engineering and detailed equilibrium-air analyses. The experimental heating rates were reduced from temperature-time histories which are available only for the trajectory period after blackout which corresponds to a freestream Mach number and altitude of approximately 11.0 and 53 km, respectively. The experimental heating rates are computed for two measured emissivity data sets. The differences in the experimental heating rates based on the two emissivity data sets are sufficiently large that different interpretations of the STS-1 aerothermal environment may be inferred.

Zoby, E. V.↗
NASA NTRS1983

Simulating spatial and temporal variation of corn canopy temperature during an irrigation cycle

The canopy air temperature difference (delta T) which provides an index for scheduling irrigation was examined. The Monteith transpiration equation was combined with both uptake from a single layered root zone and change in internal storage of the plant and the continuity equation for water flux in the soil plant atmosphere system was solved. The model indicates that both daily total transpiration and soil induced depression of plant water potential may be inferred from mid-day delta T. It is suggested that for the soil plant weather data used in the simulation, either a mid day spatial variability of about 0.8K in canopy temperatures or a field averaged delta T of 2 to 4K may be a suitable criterion for irrigation scheduling.

Choudhury, B. J.↗
NASA NTRS1983

The extragalactic background light at 4400 A

Space based photometric determinations of the extragalactic background light (EBL) are compared with galaxy count determinations of EBL brightness. The results of various EBL studies at blue and visual wavelengths are summarized, and an upper limit of 3.9 S-sub-10 (V)-sub-G2V at the 2 sigma level is placed on the brightness of the extragalactic background at 4400 A. EBL data in regions near the north and south galactic poles are also presented, the first such data obtained from heliocentric distances where the zodiacal light is negligible. Several paradigms consistent with the inferred EBL limits are mentioned, including less galactic evolution or masking of galactic evolution, galaxy formation at very high redshifts, and dusty primeval galaxies decreasing optical EBL and increasing infrared EBL. Models promulgating all primeval galaxies as high-luminosity objects undergoing bursts of star formation are incompatible with the EBL observations.

Toller, G. N.↗
NASA NTRS1985

Observed relation between thermal emission and reflected spectral radiance of a complex vegetated landscape

An investigation is conducted, for a complex vegetated land area, into the statistical relationship between remotely sensed thermal emissions and reflected spectral radiance. The Kauth-Thomas Tasseled Cap transformation is employed to infer the albedo and amount of green vegetation present from Landsat multispectral scanner (MSS) observations. Reflective data and thermal infrared data were acquired from the Heat Capacity Mapping Mission (HCMM) satellite along with reflective data from the Landsat 3 MSS for a site near Hartford, CT on a single date. Results are presented which indicate that thermal emissions had the greatest association with the amount of vegetation as indicated by a multispectral index, while albedo did not exhibit any substantial relationship with these emissions. These findings are explained in terms of the enhanced latent heat flux to the atmosphere associated with actively transpiring vegetation.

Goward, S. N.↗
NASA NTRS1986

Heliocentric radius of the cosmic ray modulation boundary

A semiempirical analysis is made of an extensive body of observed cosmic ray intensity data from Pioneers 10 and 11, and related spectral information from other authors, in order to infer the radius R of the modulation region surrounding the sun. During the period 1972-1985, the inferred values of R vary with time systematically and in a manner generally similar to that of sunspot numbers. The range of values of R is from 42 AU at the time of minimum solar activity (circa 1976) to 88 AU about 1.5 yr following the time of maximum solar activity (circa 1980). A specific, testable prediction is that Pioneer 10 will reach the modulation boundary in 1988, and will remain in its vicinity for several years thereafter.

Randall, B. A.↗
NASA NTRS1986

A study of gravity-wave spectra in the troposphere and stratosphere at 5-min to 5-day periods with the Poker Flat MST radar

An analysis of frequency spectra at periods of about 5 days to 5 min from two 20-day sets of velocity measurements in the stratosphere and troposphere region obtained with the Poker Flat mesosphere-stratosphere-troposphere (MST) radar during January and June, 1984 is presented. A technique based on median filtering and averaged order statistics for automatic editing, smoothing and spectral analysis of velocity time series contaminated with spurious data points or outliers is outlined. The validity of this technique and its effects on the inferred spectral index was tested through simulation. Spectra obtained with this technique are discussed. The measured spectral indices show variability with season and height, especially across the tropopause. The discussion briefly outlines the need for obtaining better climatologies of velocity spectra and for the refinements of the existing theories to explain their behavior.

Bemra, R. S.↗
NASA NTRS1988

High-latitude dayside electric fields and currents during strong northward interplanetary magnetic field - Observations and model simulation

On July 23, 1983 the IMF turned strongly northward, becoming about 22 nT for several hours. Using a combined data set of ionospheric convection measurements made by the Sondre Stromfjord incoherent scatter radar and convection inferred from Greenland magnetometer measurements, the onset of the reconfiguration of the high-latitude ionospheric currents is found to occur about 3 min after the northward IMF encounters the magnetopause. The large-scale reconfiguration of currents, however, appears to evolve over a period of about 22 min. These observations and the results of numerical simulations indicate that the dayside polar-cap electric field observed during strong northward IMF is produced by a direct electrical current coupling with the solar wind.

Clauer, C. Robert↗
NASA NTRS1992

Ockham's razor and Bayesian analysis

'Ockham's razor', the ad hoc principle enjoining the greatest possible simplicity in theoretical explanations, is presently shown to be justifiable as a consequence of Bayesian inference; Bayesian analysis can, moreover, clarify the nature of the 'simplest' hypothesis consistent with the given data. By choosing the prior probabilities of hypotheses, it becomes possible to quantify the scientific judgment that simpler hypotheses are more likely to be correct. Bayesian analysis also shows that a hypothesis with fewer adjustable parameters intrinsically possesses an enhanced posterior probability, due to the clarity of its predictions.

Jefferys, William H.↗
NASA NTRS1995

Shadowing the soft x-ray background by infrared cirrus: A study of selected regions

Using the ROSAT and IRAS data achieves, we studied shadows in the diffuse 0.25 keV background toward infrared cirrus clouds to infer the distribution of the hot interstellar medium (ISM). Surprisingly, we found that anticorrelation between infrared emission from cirrus clouds and background x-ray intensity was present in all five galactic latitude (b approx. greater than 25 deg) fields that we selected. In two fieds, the anticorrelation is more than 30% deep, and shows particularly convincing evidence that they are due to x-ray absorption by the clouds. Assuming an average density for the local x-ray-emitting gas (T approximately 10(exp 6) K), we estimated the minimum distances to the clouds based on our best-fit x-ray intensities originating in front of the clouds. These distances are in the range of 60 to 160 pc. Therefore, we conclude that there are a considerable number of degree-size, x-ray-absorbing gas clouds at approximately 10(exp 2) pc and that large amounts of x-ray-emitting gas exist in regions beyonds these clouds.

Wang, Q. Daniel↗
NASA NTRS1995

Lyman alpha emissions in the outer heliosphere

Since 1993, the Ultraviolet Spectrometers aboard both Voyager 1 and 2, were used to study the Ly-alpha glow pattern backscattered by neutral hydrogen atoms at great distance from the sun. When compared to a radiative transfer calculation for an unperturbed interstellar hydrogen flow into the solar system, the data present an excess of intensity seen in the direction of the incoming interstellar wind. An absolute estimate of this Lyman alpha intensity yields 10 to 15 Rayleighs for each spacecraft. We discuss the possibility that this excess is caused by a gradient of hydrogen at large distance from the Sun due to the filtration of interstellar hydrogen when crossing the heliopause. Comparisons with results from the Baranov-Malama model of neutral-plasma coupling at the heliopause are presented. The data yield a range of possible values for the hydrogen gradient which may be used to infer the location of the heliopause.

Quemerais, E.↗
NASA NTRS2005

The Abundance of Interstellar Fluorine

The primary objective of this program was to obtain FUSE observations of the interstellar absorption lines of F I at 951 and 954 Angstroms to derive the abundance of fluorine toward the star HD 164816. The nucleosynthetic source(s) of fluorine are still a matter of debate - the present day abundance of fluorine can potentially constrain models for pulsationally driven dredge-up in asymptotic giant branch stars. An accurate measure for the depletion behavior of fluorine will determine whether it may be detectable in QSO absorption line systems - an unambiguous detection of fluorine at suitably high redshifts would provide the best evidence to date for the neutrino process in massive stars. Furthermore, due to its extreme reactivity, measurement of the gas-phase interstellar fluorine abundance is important for models of grain chemistry. Despite the importance of measuring the interstellar fluorine abundance, at the time of our proposal only one previous detection has been made due to the low relative abundance of fluorine, the lack of lines outside the far-UV, and the blending of the available F I transitions with lines of Hz. The star HD 164816 is associated with the Lagoon nebula (M8), and at a distance of approximately 1.5 kpc probes both distant and local gas. Beginning April 8th, 2004 FUSE FP-Split observations of the star HD 164816 were obtained for this program. This data became available in the FUSE data archive May 21, 2004, and these observations were then downloaded and we began our analysis. Our analysis procedure has involved (1) fitting stellar models to the FUSE spectra, (2) using the multiple lines of Hz and N I at other wavelengths in the FUSE bandpass to derive column densities for the lines of H2 and N I which are blended with the F I features at 951 and 954 angstroms (3) the measurement of the column densities of F I and the species O I and C1 I which are important species for the dis-entangling of dust and nucleosynthetic effects. As discussed in our poster paper presented at the Winter 2005 American Astronomical Society meeting (Lauroesch et al. 2004, AAS, 205, 57.06), our analysis of the data taken for this star suggests that the observed fluorine gas-phase abundance (and hence inferred depletion onto dust grains) are consistent with previous measures toward delta Sco (Copernicus) and two recent measures toward stars in Cep OB2 obtained by others with FUSE. We are currently revising the draft a paper for submission to the Astrophysical Journal which presents the results of these observations and in addition our recently obtained FUSE observations of another star (HD 103779, FUSE GO program D073) which shows an apparent slight enhancement in the gas-phase fluorine abundance.

Lauroesch, James T.↗
NASA NTRS2005

Large-Scale Experimental Planetary Science Meets Planetary Defense: Deorbiting an Asteroidal Satellite

Other than remote-sensing and spacecraft-derived data, the only information that exists regarding the physical and chemical properties of asteroids is that inferred through calculations, numerical simulations, extrapolation of experiments, and meteorite studies. Our understanding of the dynamics of accretion of planetesimals, collisional disruption of asteroids, and the macroscopic, shock-induced modification of the surfaces of such small objects is also, for the most part, founded on similar inferences. While considerable strides have been made in improving the state of asteroid science, too many unknowns remain to assert that we understand the parameters necessary for the more practical problem of deflecting an asteroid or asteroid pair on an Earth-intersecting trajectory. Many of these deficiencies could be reduced or eliminated by intentionally deorbiting an asteroidal satellite and monitoring the resulting collision between it and the primary asteroid, a capability that is well within the limitations of current technology.

Cintala, M. J.↗
NASA NTRS2010

A Model-Based Probabilistic Inversion Framework for Wire Fault Detection Using TDR

Time-domain reflectometry (TDR) is one of the standard methods for diagnosing faults in electrical wiring and interconnect systems, with a long-standing history focused mainly on hardware development of both high-fidelity systems for laboratory use and portable hand-held devices for field deployment. While these devices can easily assess distance to hard faults such as sustained opens or shorts, their ability to assess subtle but important degradation such as chafing remains an open question. This paper presents a unified framework for TDR-based chafing fault detection in lossy coaxial cables by combining an S-parameter based forward modeling approach with a probabilistic (Bayesian) inference algorithm. Results are presented for the estimation of nominal and faulty cable parameters from laboratory data.

Schuet, Stefan R.↗
NASA NTRS2015

Aerosol Correction for Improving OMPS/LP Ozone Retrieval

The Ozone Mapping and Profiler Suite Limb Profiler (OMPS-LP) on board the Suomi National Polar-orbiting Partnership (SNPP) satellite was launched on Oct. 28, 2011. Limb profilers measures the radiance scattered from the Earth's atmospheric in limb viewing mode from 290 to 1000 nm and infer ozone profiles from tropopause to 60 km. The recently released OMPS-LP Version 2 data product contains the first publicly released ozone profiles retrievals, and these are now available for the entire OMPS mission, which extends from April, 2012. The Version 2 data product retrievals incorporate several important improvements to the algorithm. One of the primary changes is to turn off the aerosol retrieval module. The aerosol profiles retrieved inside the ozone code was not helping the ozone retrieval and was adding noise and other artifacts. Aerosols including polar stratospheric cloud (PSC) and polar mesospheric clouds (PMC) have a detectable effect on OMPS-LP data. Our results show that ignoring the aerosol contribution would produce an ozone density bias of up to 10 percent in the region of maximum aerosol extinction. Therefore, aerosol correction is needed to improve the quality of the retrieved ozone concentration profile. We provide Aerosol Scattering Index (ASI) for detecting aerosols-PMC-PSC, defined as ln(Im-Ic) normalized at 45km, where Im is the measured radiance and Ic is the calculated radiance assuming no aerosols. Since ASI varies with wavelengths, latitude and altitude, we can start by assuming no aerosol profiles in calculating the ASIs and then use the aerosol profile to see if it significantly reduces the residuals. We also discuss the effect of aerosol size distribution on the ozone profile retrieval process. Finally, we present an aerosol-PMC-PSC correction scheme.

OMPS/LP↗
NASA NTRS2019

Mercury's Internal Structure

We describe the current state of knowledge about Mercury's interior structure. We review the available observationalconstraints, including mass, size, density, gravity eld, spin state, composition, and tidal response. These data enablethe construction of models that represent the distribution of mass inside Mercury. In particular, we infer radial prolesof the pressure, density, and gravity in the core, mantle, and crust. We also examine Mercury's rotational dynamicsand the inuence of an inner core on the spin state and the determination of the moment of inertia. Finally, we discussthe wide-ranging implications of Mercury's internal structure on its thermal evolution, surface geology, capture in aunique spin-orbit resonance, and magnetic eld generation.

Mercury↗
NASA NTRS2019

ALMA Spectral Imaging of Titan Contemporaneous with Cassini's Grand Finale

The Cassini mission performed 127 targeted ybys of Titan during its 13 yr mission to Saturn, culminating in the Grand Finale between 2017 April and September. Here we demonstrate the use of the Atacama Large Millimeter/ submillimeter Array (ALMA) to continue Cassini's legacy for chemical and climatological studies of Titan's atmosphere. Whole-hemisphere, interferometric spectral maps of HCN, HNC, HC3N, CH3CN, C2H3CN, C2H5CN,and C3H8 were obtained using ALMA in 2017 May at moderate (0 2, or 1300 km) spatial resolution, revealing the effects of seasonally variable chemistry and dynamics on the distribution of each species. The ALMA submillimeter observations of HCN and HC3N are consistent with Cassini infrared data on these species, obtained in the same month. Chemical/dynamical lifetimes of a few years are inferred for C2H3CN and C2H5CN, in reasonably close agreement with the latest chemical models incorporating the sticking of C2H5CN to stratospheric aerosol particles. ALMA radial limb ux proles provide column density information as a function of altitude, revealing maximum abundances in the thermosphere (above 600 km) for HCN, HNC, HC3N, and C2H5CN. This constitutes the rst detailed measurement of the spatial distribution of HNC, which is found to be conned predominantly to altitudes above 730 ± 60 km. The HNC emission map shows an east-west hemisphericasymmetry of 13% ± 3%. These results are consistent with very rapid production (and loss) of HNC in Titan's uppermost atmosphere, making this molecule an effective probe of short-timescale (diurnal) ionospheric processes.

Cordiner, M. A.↗
NASA NTRS2005

An improved data structure for AVIRIS-type imaging spectrometer measurements

Imaging spectrometers, such as the Airborne Visible/Infrared Imaging (AVIRIS), measure spectra in the region from 400 to 2500 nm at nominally 10-nrn sampling. This gives approximately 200 continuous spectral channels of data for every spatial element measured. These spectroscopic measurements are used to determine the composition and infer processes of the Earth system through spectroscopy analysis. Spectroscopic analysis is based on the physics, chemistry, and biology revealed through the interaction of energy with matter recorded in each measured spectrum

Perez, Rosa M.↗