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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

High-resolution observations of the polar magnetic fields of the sun

High-resolution magnetograms of the solar polar region were used for the study of the polar magnetic field. In contrast to low-resolution magnetograph observations which measure the polar magnetic field averaged over a large area, we focused our efforts on the properties of the small magnetic elements in the polar region. Evolution of the filling factor (the ratio of the area occupied by the magnetic elements to the total area) of these magnetic elements, as well as the average magnetic field strength, were studied during the maximum and declining phase of solar cycle 22, from early 1991 to mid-1993. We found that during the sunspot maximum period, the polar regions were occupied by about equal numbers of positive and negative magnetic elements, with equal average field strength. As the solar cycle progresses toward sunspot minimum, the magnetic field elements in the polar region become predominantly of one polarity. The average magnetic field of the dominant polarity elements also increases with the filling factor. In the meanwhile, both the filling factor and the average field strength of the non-dominant polarity elements decrease. The combined effects of the changing filling factors and average field strength produce the observed evolution of the integrated polar flux over the solar cycle. We compared the evolutionary histories of both filling factor and average field strength, for regions of high (70-80 deg) and low (60-70 deg) latitudes. For the south pole, we found no significant evidence of difference in the time of reversal. However, the low-latitude region of the north pole did reverse polarity much earlier than the high-latitude region. It later showed an oscillatory behavior. We suggest this may be caused by the poleward migration of flux from a large active region in 1989 with highly imbalanced flux.

Lin, H.↗
NASA NTRS1999

An EUVE Study of the B Stars Epsilon and Beta Canis Majoris

This program is a study of the comparative characteristics of the temporal variations in the extreme ultraviolet (EUV), middle ultraviolet, and optical spectral regions of the pulsating star beta Canis Majoris (beta CMa) using data from the Extreme Ultraviolet Explorer satellite. (Although the title includes two stars, only beta CMa was actually observed.) This is a program Initiated at the University of Wisconsin by J. Cassinelli and D. Cohen (now at Univ. of Delaware) and subcontracted into several components. The portion delegated to CSC (Smith) had two components: a study of the stars flux variations in the middle ultraviolet wavelength region and consulting on the pulsational characteristics of this class of stars. The research for CSC's component of this work has been to identity a group of high-resolution spectra In the final archives of the International Ultraviolet Explorer satellite and to analysis the difference between selected spectra during low and high flux phases. This analysis was carried out by binning the spectral fluxes to low resolution, taking their ratio, and examining the spectrum ratio for spectrophotometric signatures sensitive to temperature difference and density. These were calibrated against spectral flux ratios obtained from model atmospheres. These results have been completed and the results communicated to the PIs of the program. We have also communicated to them the general results of the nature of the pulsational amplitude variations both from his work and from the work of other researchers in the astronomical literature. It is expected that this work will be published soon in a refereed astronomical journal.

Smith, Myron A.↗
NASA NTRS1985

Line identifications, line strengths, and continuum flux measurements in the ultraviolet spectrum of Arcturus

The ultraviolet spectrum of Arcturus has been observed at high resolution with the IUE satellite. Line identifications, mean absolute 'continuum' flux measurements, integrated absolute emission-line fluxes, and measurements of selected absorption line strengths are presented for the 2250-2930 A region. In the 1150-2000 A region, identifications are given primarily on the basis of low-resolution spectra. Chromospheric emission lines have been identified with low-excitation species including H I, C I, C II, O I, Mg I, Mg II, Al II, Si I, Si II, S I, and Fe II; there is no evidence for lines of C IV, N V, or other species requiring high temperatures. A search for molecular absorption features in the 2500-2930 A interval has led to several tentative identifications, but only OH could be established as definitely present. Iron lines strongly dominate the identifications in the 2250-2930 A region, Fe II accounting for about 86 percent of the emission features and Fe I for 43 percent of the identified absorption features.

Carpenter, K. G.↗
NASA NTRS1990

IUE observations of comet Austin (1989c1)

Observations of comet Austin (1989c1) were made using the International Ultraviolet Explorer (IUE) satellite on December 22, 1989 (preperihelion) and on nine dates between 7 and 24 May, 1990 (postperihelion). A summary of observation dates and parameters is given. The ultraviolet spectrum is characteristic of that of non-dusty comets. Some preliminary results are presented for OH and CS production rates and dust-reflected solar continuum emission based upon the long wavelength, low resolution mode spectra; photometry using the IUE Fine Error Sensor; a detection of the CO fourth positive system in the short wavelength, low dispersion spectra; and an upper limit on S2.

Budzien, S. A.↗
NASA NTRS1992

The cluster of galaxies associated with the low-redshift quasar H1821 + 643

Low resolution spectra have been obtained of eight R is approximately equal to 19 mag galaxies located within 1 arcmin of the low-redshift, high luminosity quasar H1821 + 643. Six of the eight galaxies belong to a cluster that has the same redshift, within the observational errors, as the quasar. Five of the six cluster members have the spectra of early type galaxies; the spectrum of the sixth cluster member contains H-alpha, semiforbidden O III, and possibly O II emission lines. The other two objects are an emission line foreground galaxy and a background galaxy. The cluster has a Galactocentric redshift of 0.299 +/- 0.002 and a radial velocity dispersion of 1050 +/- 320 km/s. The photometric and spectroscopic data suggest that H1821 + 643 is associated with a rich cluster of galaxies.

Schneider, Donald P.↗
NASA NTRS2017

Ice Mass Change in Greenland and Antarctica Between 1993 and 2013 from Satellite Gravity Measurements

We construct long-term time series of Greenland and Antarctic ice sheet mass change from satellite gravity measurements. A statistical reconstruction approach is developed based on a principal component analysis (PCA) to combine high-resolution spatial modes from the Gravity Recovery and Climate Experiment (GRACE) mission with the gravity information from conventional satellite tracking data. Uncertainties of this reconstruction are rigorously assessed; they include temporal limitations for short GRACE measurements, spatial limitations for the low-resolution conventional tracking data measurements, and limitations of the estimated statistical relationships between low- and high-degree potential coefficients reflected in the PCA modes. Trends of mass variations in Greenland and Antarctica are assessed against a number of previous studies. The resulting time series for Greenland show a higher rate of mass loss than other methods before 2000, while the Antarctic ice sheet appears heavily influenced by interannual variations.

Talpe, Matthieu J.↗
NASA NTRS1993

Constraints on the rate of discharge and duration of the Mangala Valles flood

Interest in Mangala Valles remains high within the planetary science community. This is justified because the survey mission images provide us with nearly complete coverage of the system at high resolution. Upcoming high resolution topography from the Mars Observer Laser Altimeter will enable the application of flood discharge models with an unprecedented level of detail. Previous work on the Mangala Valles problem has relied on the available low resolution topography. This has limited the ability of workers to constrain discharge calculations to only within several-order-of-magnitude estimates. Local determinations of channel depths via shadow length measurements and photoclinometric profiling are much more accurate, but can only be applied to steep slopes (and/or low sun elevations) in the case of shadow measurements, or across relatively short distances (to avoid changes in albedo along asymmetric photoclinometric profiles). We are taking stereo parallax measurements from medium resolution Viking Orbiter images, which provide a valuable intermediate check of the topography between those measurements made thus far and the upcoming Mars Observer data. The images used are from orbits 034A and 637A, and cover Mangala Valles from the source graben in Memnonia Fossae to the beginning of the bifurcated reach (at 9.5 deg lat., 151.5 deg lon.). These images are about 300 m/pixel and 250 m/pixel, respectively. Both sets of images were orthographically projected to 250 m/pixel. The separation angle between left-right pairs is approximately 52 degrees. This results in a vertical accuracy on the order of plus or minus 260 m. Though this is still somewhat coarse, the channel relief is clearly resolved. Preliminary profiles across Mangala Valles and the large topographic ridge to the east are shown on the following page. An east-west regional tilt that resulted from slight scaling differences in the digital data has been 'removed' by visually estimating a regional datum on the stereo pairs. North-south variations in scale have not yet been adjusted for, so the zero datum for each profile was simply taken to be the high water line of the channel itself. Our depth measurement for the source breach of about 750 m agrees reasonably well with values of 700-1000 m determined from shadow measurements.

Parker, T. J.↗
NASA NTRS1990

Measurement of the solar UV flux in the stratosphere

Measurements of the direct solar flux from balloons at an altitude of 40 km are used to determine the effective cross sections of the Schumann-Runge bands. Transmission in these bands, which lie between 180 and 200 nm, allows the Sun's radiation in this region of the spectrum to penetrate into the lower mesosphere. Measurements by a high resolution scanning spectrometer (0.02 nm) are used to measure the transmission in the Schumann-Runge bands. Since ozone absorbs in this wavelength region, a low resolution scanning spectrometer (0.25 nm) measures the transmission between 220 and 260 nm, allowing the column ozone to be determined. Absorption due to ozone can then be calculated and the data corrected for this effect.

Mentall, James E.↗
NASA NTRS1999

AIRES: An Airborne Infra-Red Echelle Spectrometer for SOFIA

SOFIA will enable astronomical observations with unprecedented angular resolution at infrared wavelengths obscured from the ground. To help open this new chapter in the exploration of the infrared universe, we are building AIRES, an Airborne Infra-Red Echelle Spectrometer. AIRES will be operated as a first generation, general purpose facility instrument by USRA, NASA's prime contractor for SOFIA. AIRES is a long slit spectrograph operating from 17 - 210 microns. In high resolution mode the spectral resolving power is approx. 10(exp 6) microns/A or approx. 10(exp 4) at 100 microns. Unfortunately, since the conference, a low resolution mode with resolving power about 100 times lower has been deleted due to budgetary constraints. AIRES includes a slit viewing camera which operates in broad bands at 18 and 25 microns.

Dotson, Jessie J.↗
NASA NTRS1980

Remote sensing for water quality and biological measurements in coastal waters

Recent remote sensing experiments in the United States' coastal waters indicate that certain biological and water quality parameters have distinctive spectral characteristics. Data outputs from remote sensors, to date, include: (1) high resolution measurements to determine concentrations and distributions of total suspended particulates, temperature, salinity, chlorophyll a, and phytoplankton color group associations from airborne and/or satellite platforms, and (2) low resolution measurements of total suspended solids, temperature, ocean color, and possibly chlorophyll from satellite platforms. A summary of platforms, sensors and parameters measured is given. Remote sensing, especially when combined with conventional oceanographic research methods, can be useful in such high priority research areas as estuarine and continental shelf sediment transport dynamics, transport and fate of marine pollutants, marine phytoplankton dynamics, and ocean fronts.

Johnson, R. W.↗
NASA NTRS1994

High-resolution mid-infrared observations of NGC 7469

We present a high-resolution 11.7 micrometer image of the starburst/Seyfert hybrid galaxy NGC 7469 using the Hale 5 m telescope at Palomar Observatory. Our map, with diffraction limited spatial resolution of 0.6 sec, shows a 3 sec diameter ring of emission around an unresolved nucleus. The map is similar to the Very Large Array (VLA) 6 cm map of this galaxy made with 0.4 sec resolution by Wilson et al. (1991). About half of the mid-infrared flux in our map emerges from the unresolved nucleus. We also present spatially resolved low resolution spectra that show that the 11.3 micrometer polycyclic aromatic hydrocarbon (PAH) feature comes from the circumnuclear ring but not from the nucleus of the galaxy.

Miles, J. W.↗
NASA NTRS2000

Visible Wavelength Spectroscopy of Ferric Minerals: A Key Tool for Identification of Ancient Martian Aqueous Environments

The mineralogic signatures of past aqueous alteration of a basaltic Martian crust may include iron oxides and oxyhydroxides, zeolites, carbonates, phyllosilicates, and silica. The identities, relative abundances, and crystallinities of the phases formed in a particular environment depend on physicochemical conditions. At one extreme, hot spring environments may be characterized by smectite-chlorite to talc-kaolinite silicate assemblages, plus crystalline ferric oxides dominated by hematite. However, most environments, including cold springs, pedogenic layers, and ponded surface water, are expected to deposit iron oxides and oxyhydroxides, carbonates, and smectite-dominated phyllosilicates. A substantial fraction of the ferric iron is expected to occur in nanophase form, with the exact mineralogy strongly influenced by Eh-pH conditions. Detection of these phases has been an objective of a large body of terrestrial telescopic, Mars orbital, and landed spectral investigations and in situ compositional measurements. However, clear identifications of many of these phases is lacking. Neither carbonate nor silica has been unequivocally detected by any method. Although phyllosilicates may occur near the limit of detection by remote sensing, in general they appear to occur in only poorly crystalline form. In contrast, compelling evidence for ferric iron minerals has been gathered by recent telescopic investigations, the Imager for Mars Pathfinder (IMP), and the Thermal Emission Spectrometer (TES) on the Mars Global Surveyor (MGS). These data yield two crucial findings: (1) In the global, high spatial resolution TES data set, highly crystalline ferric iron (as coarse-grained 'gray' hematite) has been recognized but with only very limited spatial occurrence and (2) Low-resolution telescopic reflectance spectroscopy, very limited orbital reflectance spectroscopy, and landed multispectral imaging provide strong indications that at least two broad classes of ferric iron minerals are commonplace in non-dust covered regions.

Murchie, Scott L.↗
NASA NTRS2001

Ultraviolet Broad Absorption Features and the Spectral Energy Distribution of the QSO PG 1351+641

We present a moderate-resolution (approximately 20 km/s) spectrum of the broad-absorption line QSO PG 1351+64 between 915-1180 angstroms, obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). Additional low-resolution spectra at longer wavelengths were also obtained with the Hubble Space Telescope (HST) and ground-based telescopes. Broad absorption is present on the blue wings of C III lambda977, Ly-beta, O VI lambda-lambda-1032,1038, Ly-alpha, N V lambda-lambda-1238,1242, Si IV lambda-lambda-1393,1402, and C IV lambda-lambda-1548,1450. The absorption profile can be fitted with five components at velocities of approximately -780, -1049, -1629, -1833, and -3054 km/s with respect to the emission-line redshift of z = 0.088. All the absorption components cover a large fraction of the continuum source as well as the broad-line region. The O VI emission feature is very weak, and the O VI/Ly-alpha flux ratio is 0.08, one of the lowest among low-redshift active galaxies and QSOs. The ultraviolet continuum shows a significant change in slope near 1050 angstroms in the restframe. The steeper continuum shortward of the Lyman limit extrapolates well to the observed weak X-ray flux level. The absorbers' properties are similar to those of high-redshift broad absorption-line QSOs. The derived total column density of the UV absorbers is on the order of 10(exp 21)/s, unlikely to produce significant opacity above 1 keV in the X-ray. Unless there is a separate, high-ionization X-ray absorber, the QSO's weak X-ray flux may be intrinsic. The ionization level of the absorbing components is comparable to that anticipated in the broad-line region, therefore the absorbers may be related to broad-line clouds along the line of sight.

Zheng, W.↗
NASA NTRS1980

A thermalized ion explosion model for high energy sputtering and track registration

A velocity spectrum of neutral sputtered particles as well as a low resolution mass spectrum of sputtered molecular ions was measured for 4.74 MeV F-19(+2) incident of UF4. The velocity spectrum is dramatically different from spectra taken with low energy (keV) bombarding ions, and is shown to be consistent with a hot plasma of atoms in thermal equilibrium inside the target. A thermalized ion explosion model is proposed for high energy sputtering which is expected to describe track formation in dielectric materials. The model is shown to be consistent with the observed total sputtering yield and the dependence of the yield on the primary ionization rate of the incident ion.

Seiberling, L. E.↗
NASA NTRS1980

Enumeration of prairie wetlands with Landsat and aircraft data

A method is described for estimating wetland abundance in the 700,000 sq km prairie pothole region of North America. A double sampling procedure is described, incorporating the use of high resolution aircraft imagery, capable of delineating ponds as small as 5 m across, as a means of adjusting the count of surface water features derived from the low-resolution Landsat census over a 38,876 sq km area in east-central North Dakota. The regression expansion formula used to estimate the actual number of total wetlands is also presented.

Gilmer, D. S.↗
NASA NTRS2004

Bioinspired Engineering of Exploration Systems (BEES) - its Impact on Future Missions

This paper describes an overview of our "Bioinspired Engineering of Exploration Systems for Mars" ( "BEES for Mars") project. The BEES approach distills selected biologically inspired strategies utilizing motion cues/optic flow, bioinspired pattern recognition, biological visual and neural control systems, bioinspired sensing and communication techniques, and birds of prey inspired search and track algorithmic systems. Unique capabilities so enabled, provide potential solutions to future autonomous robotic space and planetary mission applications. With the first series of tests performed in September 2003, August 2004 and September 2004, we have demonstrated the BEES technologies at the El Mirage Dry Lakebed site in the Mojave Desert using Delta Wing experimental prototypes. We call these test flyers the "BEES flyer", since we are developing them as dedicated test platform for the newly developed bioinspired sensors, processors and algorithmic strategies. The Delta Wing offers a robust airframe that can sustain high G launches and offers ease of compact stowability and packaging along with scaling to small size and low ReynOld's number performance for a potential Mars deployment. Our approach to developing light weight, low power autonomous flight systems using concepts distilled from biology promises to enable new applications, of dual use to NASA and DoD needs. Small in size (0.5 -5 Kg) BEES Flyers are demonstrating capabilities for autonomous flight and sensor operability in Mars analog conditions. The BEES project team spans JPL, NASA Ames, Australian National University (ANU), Brigham Young University(BYU), DC Berkeiey, Analogic Computers Inc. and other institutions. The highlights from our recent flight demonstrations exhibiting new Mission enabling capabilities are described. Further, this paper describes two classes of potential new missions for Mars exploration: (1) the long range exploration missions, and (2) observation missions, for real time imaging of critical ephemeral phenomena, that can be enabled by use of BEES flyers. For example, such flyers can serve as a powerful black-box for critical descent and landing data and enablers for improved science missions complementing and supplementing the existing assets like landers and rovers by providing valuable exploration and quick extended low-altitude aerial coverage of the sites of interest by imaging them and distributing instruments to them. Imaging done by orbiters allows broad surface coverage at limited spatial resolution. Low altitude air-borne exploration of Mars offers a means for imaging large areas, perhaps up to several hundred kilometers, quickly and efficiently, providing a close-up birds-eye view of the planetary terrain and close-up approach to constrained difficult areas like canyons and craters. A novel approach to low-mass yet highly capable flyers is enabled by small aircraft equipped using sensors and processors and algorithms developed using BEES technology. This project is focused towards showing the direct impact of blending the best of artificial intelligence attributes and bioinspiration to create a leap beyond existing capability for our future Missions.

navigation↗
NASA NTRS1990

On estimating scale invariance in stratocumulus cloud fields

Examination of cloud radiance fields derived from satellite observations sometimes indicates the existence of a range of scales over which the statistics of the field are scale invariant. Many methods were developed to quantify this scaling behavior in geophysics. The usefulness of such techniques depends both on the physics of the process being robust over a wide range of scales and on the availability of high resolution, low noise observations over these scales. These techniques (area perimeter relation, distribution of areas, estimation of the capacity, d0, through box counting, correlation exponent) are applied to the high resolution satellite data taken during the FIRE experiment and provides initial estimates of the quality of data required by analyzing simple sets. The results of the observed fields are contrasted with those of images of objects with known characteristics (e.g., dimension) where the details of the constructed image simulate current observational limits. Throughout when cloud elements and cloud boundaries are mentioned; it should be clearly understood that by this structures in the radiance field are meant: all the boundaries considered are defined by simple threshold arguments.

Seze, Genevieve↗