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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Short-wavelength electrostatic waves in the earth's magnetosheath

Recent observations with the ISEE-1 spacecraft have found electric field emissions in the dayside magnetosheath whose frequency spectrum is modulated at twice the spacecraft spin period. The upper frequency cut-off in the frequency-time spectrum of the emissions has a characteristic parabola shape or festoon shape. The low frequency cutoff ranges from 100 Hz to 400 Hz, while the high frequency limit ranges from about 1 kHz to 4 kHz. The bandwidth is found to minimize for antenna orientations parallel to the wave vectors. The wave vector does not appear to be related to either the local magnetic field direction of the plasma flow velocity. The spacecraft observed frequency spectrum results from the spacecraft antenna response to the Doppler shifted wave vector spectrum which exists in the plasma. Imposed constraints on the plasma restframe wave vectors and frequencies indicate that the emissions occur within the frequency range from about 150 Hz to 1 kHz, with wavelengths between about 30 meters and 600 meters. These constraints strongly suggest that the festoon-shaped emissions are ion-acoustic waves. The small group velocity and k direction of the ion-acoustic mode are consistent with wave generation upstream at the bow shock and convection downstream to locations within the outer dayside magnetosheath.

Gallagher, D. L.↗
NASA NTRS1985

Surface topography due to convection in a variable viscosity fluid - Application to short wavelength gravity anomalies in the central Pacific Ocean

Finite difference calculations of thermal convection in a fluid layer with a viscosity exponentially decreasing with temperature are performed in the context of examining the topography and gravity anomalies due to mantle convection. The surface topography and gravity anomalies are shown to be positive over regions of ascending flow and negative over regions of descending flow; at large Rayleigh numbers the amplitude of surface topography is inferred to depend on Rayleigh number to the power of 7/9. Compositional stratifications of the mantle is proposed as a mechanism for confining small-scale convection to a thin layer. A comparative analysis of the results with other available models is included.

Lin, J.↗
NASA NTRS1985

Short wavelength laser calculations for electron pumping in Be I and B I isoelectronic sequences (Z greater than or equal to 18 and less than or equal to 36)

There has been considerable interest in creating large laser gains in the X-ray region from atomic transitions in ne-like ions formed in high-temperature plasmas. Although the Ne-like ions habe received the most attention, it is also possible to produce population inversions in ions of other isoelectronic sequences. Accordingly, it is shown that certain levels of the 2s3p and 2s(2)3p configurations in the Be I and B I isoelectronic sequences can be inverted by collisional pumping relative to levels of the 2s3s and 2s(2)3s configurations. Level populations and gain coefficients were calculated for the most promising transitions, and opacities were calculated for 2s2p-2s3s and 2s(2)2p-2s(2)3s transitions.

Feldman, U.↗
NASA NTRS1988

Volcano monitoring using short wavelength infrared data from satellites

It is shown that Landsat TM and MSS data provide useful and sometimes unique information on magmatic and fumarolic events at poorly monitored active volcanoes. The digital number data recorded in each spectral band by TM and MSS can be converted into spectral radiance, measured in W/sq m per micron per sr, using calibration data such as those provided by Markham and Barker (1986) and can provide temperature information on the lava fountain, lava lakes, pahoehoe flows, blocky lava, pyroclastic flow, and fumarole. The examples of Landsat data documenting otherwise unobserved precursors and/or activity include the September 1986 eruption of Lascar volcano, Chile; the continued presence of lava lakes at Erta 'Ale, Ethiopia (in the absence of any ground-based observations); and minor eruptions at Mount Erebus, Antarctica.

Rothery, D. A.↗
NASA NTRS1990

Short wavelength striations on expanding plasma clouds

The present evaluation of current understanding of the growth and evolution of less-than-1 ion gyroradius 'flute modes' on a plasma as it expands across and ambient magnetic field notes that the mechanism by which the instability is generated, and its approximate linear theory (encompassing nonlocal, finite-beta, and collisional effects), have reached a satisfactory degree of development. AMPTE Ba releases have been the bases of most of the observational studies. Substantial progress is also noted in the development of a nonlinear mode-coupling theory which can resolve remaining differences between theory and observation.

Winske, D.↗
NASA NTRS1990

256 x 256 PACE-1 PV HgCdTe focal plane arrays for medium and short wavelength infrared applications

The development of two 256 by 256 hybrid HgCdTe focal plane array (FPA) families is described, and their performance is discussed. The hybrid FPAs employ a PV HgCdTe detector array and custom Si CMOS readouts. The PACE-1 process was used to fabricate the detectors, whereby the liquid phase epitaxial growth of HgCdTe occurs on sapphire substrates buffered by a layer of CdTe. The performance characteristics of the detector arrays are given. A tactical 256 by 256 CMOS readout is tested, in which a high functional yield was achieved. Updated test results are given for a 256 by 256 readout circuit developed for use in an orbital replacement instrument for the Hubble Space Telescope. The characterizations of several MWIR and SWIR FPAs were thorough and shown to be reliable. The pixel yield, maximum FPA responsivity nonuniformity, and SWIR FPA read noise for the tests are given. The high contrast and insignificant fixed pattern noise of the imagery from the MWIR 256 by 256 FPA are emphasized. These qualities were obtained when the device was operating at 80 k and utilizing f/2 optics with an 8-in. focal length and a 4.4 micron high pass filter.

Kozlowski, L. J.↗
NASA NTRS1992

NGC 4314. I - Visible and short-wavelength infrared surface photometry of the nucleus and bar

BVI (TI CCD) and JHK (University of Texas IR Camera) surface photometry of NGC 4314, an SB (rs)ap anemic spiral with a nuclear ring containing recent star formation, is presented. The shortwave IR (SWIR) frames reveal a nuclear bar of length 2 arcsec at PA of 0 deg. The nuclear ring and associated dust were detected in all SWIR color indices. A nuclear spiral was detected in the visible and SWIR just exterior to the ring. Extremely low-amplitude spiral-shaped deficits were found in the stellar distribution in the SWIR in this same region. These are attributed to dust, since CO is detectable at or near these locations. Average minor-axis profiles show this galaxy to have a nuclear bulge obeying the de Vaucouleurs r exp 1/4 law for values in the range 2-7 arcsec. The extinction and scattering characteristics of dust near the sites of recent star formation in the nuclear ring are discussed.

Benedict, G. F.↗
NASA NTRS1991

Lithographic spiral antennas at short wavelengths

We have extended the high efficiency of lithographic antennas to mid-infrared wavelengths. Pattern measurements made at 9.5/zm wavelength on a 65 deg, self-complementary, spiral antenna exhibit a ratio of response to orthogonal linear polarizations of 1.35 dB, a beamwidth of 85 deg (3 dB full width), a directivity of 8.2 dB, and surprisingly, a close resemblance to the theoretical pattern for a 65 deg spiral in free space. Direct detection measurements made with an ambient temperature blackbody source yield an antenna efficiency of 52 +/- 7 percent, when corrected for incomplete filling of the antenna beam by the source, at a mean effective wavelength of 19 micron.

Grossman, E. N.↗
NASA NTRS1993

IUE short-wavelength high-dispersion line list for the symbiotic nova RR Telescopii

An 820 minute and other long-exposure archival SWP IUE high-dispersion spectra of symbiotic star RR Tel have been combined to form a composite spectrum. In most of these spectra many lines are saturated, but weaker features appear above the continuum. Their wavelengths were measured from the composite spectrum and compared with the line list from a thorough study of RR Tel by Penston et al. (1983). Among the revised line list are 22 new line identifications from ions C III, O I, N I, Mg VI, Si I, S I, S IV, Fe II, and Ni II. N I exists inside RR Tel's H II region and is pumped by the hot component's continuum. The fluxes for all the lines in each of the spectra are presented. All of the observed ions show a secular flux decrease between 1978 and 1988. A list of SWP high-dispersion camera artifacts is also presented. The list was generated by comparing RR Tel spectra to a long-exposure sky flat.

Aufdenberg, Jason P.↗
NASA NTRS1997

Development of Short Wavelength Infrared Array Detectors for Space Astronomy Application

The Smithsonian Astrophysical Observatory (SAO) and its team - the University of Arizona (UA), the University of Rochester (UR), Santa Barbara Research Center (SBRC), Ames Research Center (ARC), and Goddard Space Flight Center (GSFC) - are carrying out a research program with the goal of developing and optimizing infrared arrays in the 2-27 micron range for space infrared astronomy. This report summarizes research results for the entire grant period 1 January 1992 through 30 June 1996.

Fazio, Giovanni G.↗
NASA NTRS2011

In Situ Visible to Short Wavelength Imaging Spectroscopy with the Ultra Compact Imaging Spectrometer (UCIS): Case Studies from the Mars Exploration Rovers

In Situ imaging spectroscopy provides a way to address complex questions of geological evolution for both aqueous and igneous processes by mapping mineral composition at the spatial scale of rocks and outcrops. Examination of locations studied by the Mars Exploration Rovers Spirit and Opportunity can provide examples of the potential utility and define the needed measurement requirements. A compact instrument is needed to be able to adequately address these science questions from a rover platform. The Ultra Compact Imaging Spectrometer (UCIS) is an instrument designed to address the science need and implementation constraints.

mineralogy sampling↗
NASA NTRS2022

Surface Biology and Geology (SBG) Visible to Short Wavelength Infrared (VSWIR) Wide Swath Instrument Concept

The 2017 Decadal Survey: Thriving on Our Changing Planet, A Decadal Strategy for Earth Observation from Space has called new observations including global coverage VSWIR Wide Swath (VSWIR-WS) imaging spectroscopy measurements as part of the Surface Biology and Geology (SBG) Designated Observable. The SBG VSWIR-WS along with the companion SBG Thermal Infrared (TIR) imager is an important element of NASA’s larger Earth System Observatory (ESO).

Walch, Marc↗
NASA NTRS1977

A comparison of satellite systems for gravity field measurements

A detailed and accurate earth gravity field model is important to the understanding of the structure and composition of the earth's crust and upper mantle. Various satellite-based techniques for providing more accurate models of the gravity field are analyzed and compared. A high-low configuration satellite-to-satellite tracking mission is recommended for the determination of both the long wavelength and short wavelength portions of the field. Satellite altimetry and satellite gradiometry missions are recommended for determination of the short wavelength portion of the field.

Argentiero, P. D.↗
NASA NTRS1978

A comparison of satellite systems for gravity field measurements

A detailed and accurate earth gravity field model is important both to geophysical progress and to the precise tracking necessary for interpretation of geophysical experiments. Various satellite techniques which may be used to determine the earth's gravity field are compared and their ability to recover the long wavelength and short wavelength features of the field are described. A high-low configuration satellite-to-satellite tracking mission is recommended for the determination of the long wavelength portion of the gravity field. Satellite altimetry and satellite gradiometry experiments are recommended for determination of the short wavelength portion of the gravity field.

Argentiero, P.↗