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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 1,369 records · Page 76
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NASA NTRS1986

Radiometric responsivity determination for Feature Identification and Location Experiment (FILE) flown on space shuttle mission

A procedure was developed to obtain the radiometric (radiance) responsivity of the Feature Identification and Local Experiment (FILE) instrument in preparation for its flight on Space Shuttle Mission 41-G (November 1984). This instrument was designed to obtain Earth feature radiance data in spectral bands centered at 0.65 and 0.85 microns, along with corroborative color and color-infrared photographs, and to collect data to evaluate a technique for in-orbit autonomous classification of the Earth's primary features. The calibration process incorporated both solar radiance measurements and radiative transfer model predictions in estimating expected radiance inputs to the FILE on the Shuttle. The measured data are compared with the model predictions, and the differences observed are discussed. Application of the calibration procedure to the FILE over an 18-month period indicated a constant responsivity characteristic. This report documents the calibration procedure and the associated radiometric measurements and predictions that were part of the instrument preparation for flight.

Wilson, R. G.↗
NASA NTRS1986

Magnetic location of C IV events in the quiet network

Ultraviolet Spectrograph and Polarimeter (UVSP) observations of C IV intensity in the quiet sun were examined and compared to magnetograms and He I 10830 A spectroheliograms from Kitt Peak National Laboratory. The observations were made between 3 and 9 April, 1985. Spatially rastered UVSP intensity measurements were obtained at 11 wavelength positions in the 1548 A line of C IV. It was concluded that the stochastic process whereby convective shuffling of loop footprints leads to many topically dissipative events in active regions and the larger bipoles treated here continues to operate in regions of fewer, weaker flux loops, but the resulting events above threshold are less frequent.

Porter, Jason G.↗
NASA NTRS1987

Application of the complex cepstrum to the location of acoustic sources near reflective surfaces

The complex cepstrum is used to correct bearing estimations of acoustic sources in the presence of a reflective surface. An automated liftering procedure is used which zeros out a block portion of the cepstrum including the echo information. The problem of the resulting distortion is alleviated by applying a coherence criterion to the recovered direct signals at each microphone. Thus to a large degree the interactive nature of cepstral processing is overcome for this application. For the test signals and geometries considered the cepstrum is shown to accurately correct for bearing errors in acoustic signals contaminated with reflections from nearby surfaces.

Fuller, C. R.↗
NASA NTRS1986

Interplanetary magnetic field control of the Venus magnetosheath field and bow shock location

Six Venus years of Pioneer Venus Orbiter (PVO) data are analyzed in a coordinate system which isolates magnetic effects. The field draping pattern features two lobes easily identifiable even in the near planet region. The magnetosheath magnetic magnitude has a hemispherical asymmetry controlled by the IMF orientation in a manner suggesting preferrential ion pickup in one hemisphere. This result complements recent findings that the bow shock position is responsive to IMF direction. Examination of the ionopause position to evaluate ionospheric effects on the overall asymmetry of thfe Venus-solar wind interaction produces negative but not conclusive results.

Phillips, J. L.↗
NASA NTRS1987

Constraints on the mass-radius relation for the neutron star in the X-ray burst source 4U/MXB 1820-30 located in the globular cluster NGC 6624

From the spectral evolution of seven X-ray bursts observed from 4U/MXB 1820-30 (Haberl et al., 1986) during the phases of photospheric expansion and cooling, constraints are derived on the mass-radius relation of the neutron star in this system. Taking into account the uncertainty in the source distance and the possible anisotropy of the burst emission. If during bursts with radius expansion the outer layers of the neutron star are of a hydrogen-poor composition, none of the current equations of state of high-density matter is excluded. For a hydrogen-rich composition, only very soft equations of state are allowed.

Van Paradijs, J.↗
NASA NTRS1987

Highly ionized interstellar gas located in the Galactic disk and halo

High-resolution IUE absorption line spectra have been obtained for 40 distant stars in order to study the distribution of interstellar H I, Si IV, C IV, and N V in the Galactic disk and lower halo. Respective midplane densities of 2 x 10 to the -9th, 7 x 10 to the -9th, and 3 x 10 to the -9th are found for Si IV, C IV, and Ni V. Both column density and velocity data indicate that the highly ionized gas (HIG) is considerably more extended in directions away from the Galactic plane than is H I or Si II. The absorption-line velocities for the halo HIG are consistent with the notion that halo gas in the inner Galaxy rotates more slowly than gas in the underlying disk. The derived column densities suggest an exponential scale height for the HIG of about 3 kpc; however, a simple exponential distribution is a poor representation of the distribution of the gas. It is concluded that a full explanation of the origin of the halo HIG will probably require a blending of ideas from the Galactic fountain and the photoionized halo models.

Savage, Blair D.↗
NASA NTRS1988

Locating Residual Wax In Coolant Channels

Neutron inspection finds deposits and defects invisible to x rays. Neutron radiography detects many low-density materials even when surrounded by larger quantities of denser materials. Materials with similar properties and densities often appear quite different when viewed by neutron radiography. Technique gives comprehensive view of hidden channels.

Guthrie, Douglas M.↗
NASA NTRS1988

Spark Igniters Fit In Correct Locations Only

Pins create interference if incorrect assembly is attempted. When two different types of spark igniters must be used on same engine simple expedient ensures that each igniter is inserted in correct hole. Damage to engine and consequent failure are thereby avoided. Pins in base of spark igniter allow part to be inserted in any type hole.

Wendland, Fred J.↗
NASA NTRS1987

Tropical easterly jet located using TOMS data

The formative stages of the onset of the 1979 southwest monsoon was marked by a WNW-ESE oriented band of marine convection over the South Arabian Sea. This convection was first observed on June 10, 1979 using satellite cloud imagery. The marine convection appeared during a major acceleration of the upper troposphere easterly wind field. A composite vertical meridional cross-section of upper level winds for June 11, revealed the core of the Tropical Easterly Jet (TEJ) at 115 mb, 9.5 deg N. Time analysis of the upper level wind field over the Tropical Wind Observing Ship (TWOS) polygon show a lowering of both the pressure level of maximum wind and tropopause level with acceleration of the upper level easterlies. The tropopause was as much as 20 mb lower on the equatorial side of the TEJ. Streamline analysis of the maximum observed easterly winds over India did not reveal the horizontal position of the TEJ. Careful analysis of Total Ozone Mapping Spectrometer (TOMS) data for June 11, 1979 showed relatively high values of ozone south of India. It was observed that the latitudinal position of the TEJ on June 11, at approximately 70 deg E coincided with the northern edge of relatively high ozone values. Using this as a reference, the TEJ core was identified as far as NE Bay of Bengal (the limits of the available TOMS data).

Bolhofer, William C.↗
NASA NTRS1988

Lightning detection and locating systems

U.S. agency and agency-sponsored programs for lightning detection are listed. Research and development in the area of lightning sensors is described.

Hovey, Russell L.↗
NASA NTRS1988

Asymmetries in the location of the Venus ionopause

Four large data sets of Venus ionopause observations, based on different definitions and observations by Pioneer Venus Orbiter field and particle instruments, are compared. Regardless of the definition chosen, the ionopause is observed to be higher on average at dawn than at dusk. The results of an empirical ionosphere model and a data analysis technique which minimizes orbital bias are combined to show that most or all of this asymmetry results from the effects of orbital bias and uneven sampling of solar wind conditions. However, an additional asymmetry is found in which the ionopause is displaced in the direction opposite to the motional electric field of the solar wind. This effect is attributed to asymmetric pickup of exospheric ions by the electric and magnetic fields in the magnetosheath. This ion pickup interpretation can be understood in terms of a previous observed magnetosheath magnetic field asymmetry. Quantitative analysis indicates that the transverse momentum imparted by the solar plasma to pickup particles in their initial gyration is transmitted by the magnetosheath magnetic field to the ionosphere boundary.

Phillips, J. L.↗
NASA NTRS1988

Impact wave deposits provide new constraints on the location of the K/T boundary impact

All available evidence is consistent with an impact into oceanic crust terminating the Cretaceous Period. Although much of this evidence is incompatible with an endogenic origin, some investigators still feel that a volcanic origin is possible for the Cretaceous/Tertiary (K/T) boundary clay layers. The commonly cited evidence for a large impact stems from delicate clay layers and their components and the impact site has not yet been found. Impact sites have been suggested all over the globe. The impact is felt to have occurred near North America by: the occurrence of a 2 cm thick ejecta layer only at North American locales, the global variation of shocked quartz grain sizes peaking in North America, the global variation of spinel compositions with most refractory compositions occurring in samples from the Pacific region and possibly uniquely severe plant extinctions in the North American region. The K/T boundary interval was investigated as preserved on the banks of the Brazos River, Texas. The K/T fireball and ejecta layers with associated geochemical anomalies were found interbedded with this sequence which apparently allows a temporal resolution 4 orders of magnitude greater than typical K/T boundary sections. A literature search reveals that such coarse deposits are widely preserved at the K/T boundary. Impact wave deposits have not been found elsewhere on the globe, suggesting the impact occurred between North and South America. The coarse deposits preserved in Deep Sea Drilling Project (DSDP) holes 151-3 suggest the impact occurred nearby. Subsequent tectonism has complicated the picture.

Hildebrand, A. R.↗
NASA NTRS1989

The source location and beaming of broadband bursty radio emissions from Uranus

A rotationally-dependent occurrence pattern is identified for the b-bursty emissions observed with Voyager 2 during its 1986 encounter with Uranus. Certain features of this pattern, such as its extension to the highest frequencies and a 40-min signal gap, were sometimes recognizable on individual rotations despite the bursty character of the signals. This pattern is interpreted in terms of Voyager's passing from the inside of a broad, hollow emission cone coming from the southern hemisphere to the outside, and then back in, as a result of planetary rotation. The emission gap then corresponds to the times when Voyager was outside the cone.

Farrell, W. M.↗
NASA NTRS1989

Source location of Jupiter's decametric radiation and UV aurora

The source region of a component of Jovian Io-unrelated decametric radiation is inferred geometrically based on simultaneous observations from Voyager spacecraft and a ground-based observatory with the aid of a hollow cone beam model and model of the Jovian magnetic field. The results indicate that the sources of this component lie above the northern hemisphere, and on field lines that connect the Io plasma torus and the Jovian ionosphere in the so-called active sector. It is concluded that an interaction between the Io-torus plasma and the ionospheric plasma through a thin flux tube initiates the decametric radiation.

Maeda, Koitiro↗
NASA NTRS1989

Source locations for impulsive electric signals seen in the night ionosphere of Venus

A mapping of the rate of occurrence of impulsive VLF noise bursts in Venus' dark low altitude ionosphere, which increases rapidly with decreasing altitude, as a function of latitude and longitude indicates enhanced occurrence rates over Atla. In a 30-sec observing period, there are impulsive signals 70 percent of the time at 160 km in the region of maximum occurrence; the occurrence rates, moreover, increase with decreasing latitude, so that the equatorial rate is of the order of 1.6 times that at 30 deg latitude. These phenomena are in keeping with lightning-generated wave sources.

Russell, C. T.↗