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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Chondrules and other components in C, O, and E chondrites Similarities in their properties and origins

Three types of chondrules are described that are common to H3, LL3, CM2, CO3, and CV3 chondrites. Low- and high-FeO, porphyritic olivine chondrules contain olivine with Fa0.3-8 and Fa5-50 respectively, and can easily be distinguished petrographically. Poikilitic pyroxene chondrules have 1-20 vol pct olivine (Fa0.2-8) enclosed by low-Ca pyroxene (Fs0.5-7), and also occur in E chondrites. These three types formed in separate nebular regions which had dimensions and spacings such that a few percent of the chondrules that collided to form compound chondrules were of different types. Sorting of chondrule precursor material and mixing of chondrule types probably account for most variations in bulk and mineral chemistry among chondrite groups. Metallic Fe,Ni grains containing 0.1-1 percent Cr, Si, and P are present in low-FeO olivine chondrules from all type 2 and least metamorphosed type 3 chondrites. Metal compositions reflect reduction during chondrule formation in the nebula, not nebular condensation. Opaque matrices in type 3 ordinary and carbonaceous chondrites are somewhat similar in composition and mineralogy, and probably have related origins. It is concluded that chondrules in all known chondrite groups share similar nebular origins.

Scott, E. R. D.↗
NASA NTRS1984

Rocket observations of electron density in the nighttime E region using Faraday rotation

A rocket radio propagation experiment is described in which the electron density profile of the nighttime E region is obtained with an accuracy of 100 per cu cm. The factors limiting the accuracy of the experiment are found to be related to atmospheric and receiver noise and to the use of a magnetometer to determine the spin rate of the rocket. The Fourier analysis used for the frequency measurement may also contribute error under conditions of steep electron density gradients. The accuracy being achieved appears to be adequate for present applications of the experiment.

Smith, L. G.↗
NASA NTRS1985

The experimental cascade curves of EAS at E sub 0 10(17) eV obtained by the method of detection of Cherenkov pulse shape

The individual cascade curves of EAS with E sub 0 10 to the 17th power eV/I to 3/ were studied by detection of EAS Cherenkov light pulses. The scintillators located at the center of the Yakutsk EAS array within a 500-m radius circle were used to select the showers and to determine the main EAS parameters. The individual cascade curves N(t) were obtained using the EAS Cherenkov light pulses satisfying the following requirements: (1) the signal-to-noise ratio fm/delta sub n 15, (2) the EAS axis-detector distance tau sub 350 m, (3) the zenith angle theta 30 deg, (4) the probability for EAS to be detected by scintillators W 0.8. Condition (1) arises from the desire to reduce the amplitude distortion of Cherenkov pulses due to noise and determines the range of EAS sizes, N(t). The resolution times of the Cherenkov pulse shape detectors are tau sub 0 approx. 23 ns which results in distortion of a pulse during the process of the detection. The distortion of pulses due to the finiteness of tau sub 0 value was estimated. It is shown that the rise time of pulse becomes greater as tau sub 0.5/tau sub 0 ratio decreases.

Fomin, Y. A.↗
NASA NTRS1985

Observations of E region irregularities generated at auroral latitudes by a high-power radio wave

The initial results of a series of observations made with the high-power HF heating facility near Tromso, Norway are reported. During these experiments, attention was focused on the production of artificial geomagnetic field-aligned irregularities (AFAIs) in the auroral E region by HF waves. A mobile 46.9-MHz radar was used to diagnose the formation of AFAIs having spatial scales of 3.2 across geomagnetic field lines. The dynamic characteristics of the AFAIs are discussed within the context of current theoretical work dealing with the natural production of AFAIs in the ionosphere.

Djuth, F. T.↗
NASA NTRS1986

Acceleration of energetic oxygen (E greater than 137 keV) in the storm-time ring current

Measurements obtained with the medium-energy particle analyzer of the equatorial-orbit AMPTE/CCE satellite during a geomagnetic storm on September 4-7, 1984 are reported and analyzed, with a focus on the high-energy populations (H, He, and CNO-group ions with E greater than 56, 72, and 137 keV, respectively). During the main phase of the storm, ring-current-region increases in O(+) intensity by factors up to 2000 are observed at L = 2.5-7.0, and the component at L = 3.5-5.5 is attributed to a 1.5-earth-radius inward displacement of the prestorm energetic-oxygen population followed by betatron acceleration. Alternative oxygen sources and/or acceleration mechanisms to account for the component at L = 6.5-8 and pitch angle 90 deg are discussed.

Lui, A. T. Y.↗
NASA NTRS1987

Multiple frequency radar observations of high-latitude E region irregularities in the HF modified ionosphere

This paper discusses the results of the September 1983 observations of artificial field-aligned irregularities (AFAIs) in the Tromso, Norway region, made by backscatter radars operating at 46.9, 143.8, 21.4, and 140.0 MHz. Four classes of resonant instability processes at work in the E and F regions are examined in detail: (1) the coupling of parametric decay instability waves across geomagnetic field lines, (2) thermal parametric instability, (3) four-wave interaction thermal parametric instability, and (4) the resonance instability. The characteristics of the AFAI scatter are described, with special attention given to the growth and decay time constants, functional dependence on the heater power and polarization, and the scattering cross sections of the irregularities.

Noble, S. T.↗
NASA NTRS1990

Linear prediction filter analysis of relativistic electron properties at 6.6 R(E)

The relationship between relativistic electron flux variations at 6.6 R(E) and various published indices and solar wind properties is studied. An attempt is made to characterize the temporal and dimensional relationships between solar wind or magnetic indices and electron flux enhancements. It is shown that the solar wind speed upstream of the earth's magnetosphere is correlated with large increases in the flux of highly relativistic electrons at geostationary orbit.

Baker, D. N.↗
NASA NTRS1994

"E" Heating Head

Two separate areas heated inductively for adhesive bonding in single operation. "E" heating head developed to satisfy need for fast-acting and reliable induction heating device. Used in attaching "high-hat" stiffeners to aircraft panels. Incorporates principles and circuitry of toroid joining gun. Width and length configured to provide variously sized heat zones, depending on bonding requirements. Lightweight, portable and provides rapid, reliable heating of dual areas in any environment. Well suited for flight-line and depot maintenance, and battlefield repair. Also useful in automotive assembly lines to strengthen automobile panels.

Fox, Robert L.↗
NASA NTRS1993

Equatorial ion composition, 140-200 km, based on Atmosphere Explorer E data

We have used in situ measurements of ion composition and horizontal winds, taken from equatorial orbiting Atmosphere Explorer E in eccentric orbit during 1975-1976 to investigate the bottomside ionosphere at altitudes 140-200 km. Representative daytime altitude profiles of ionization were stable against wide variations in horizontal wind patterns. Special features that sometimes appeared in the structured nightside ionization were apparent ion composition waves, intermediate layers of enhanced ionization, and ionization depletions similar to equatorial ionization bubbles. Apparent ion composition waves displayed a horizontal wave length of about 650 km. Enhanced layers of ionization appeared to be newly separated from the bottomside midnight F layer; its ions were primarily NO(+) and O2(+) without significant densities of metallic ions, an indication that metallic ions are not required to produce the layers at altitudes above 140 km. Equatorial ionization depletions were observed at lower altitudes than previously reported and displayed molecular ion depletions as well as O(+) depletions.

Miller, N. J.↗
NASA NTRS1997

Measurement of Atomic Oxygen in Diffuse Aurora and Ion Density in the E-Region

An ion mass spectrometer (IMS) was refurbished, calibrated and supplied to the University of Colorado payload (Dr. Charles Barth, P.I.) which was launched from White Sands in September of 1993 as NASA 33.062. The nose cone failed to deploy and their were problems with the ACS so the mission was declared a failure. However, the door covering the IMS deployed and the instrument obtained data. The launch occurred shortly after a payload carrying solar x-ray detectors was launched. Thus a small portion of the Colorado payload science was salvaged; namely, the NO(+)/O2(+) ratio to compare with the measured x-ray flux. Figure I shows the NO(+) to O2(+) ratio vs. altitude. The behavior is typical of the E-region.

Sharp, William E.↗
NASA NTRS1999

The Astro-E/XRS Blocking Filter Calibration

We describe the transmission calibration of the Astro-E XRS blocking filters. The XRS instrument has five aluminized polyimide blocking filters. These filters are located at thermal stages ranging from 200 K to 60 mK. They are each about 1000 A thick. XRS will have high energy resolution which will enable it to see some of the extended fine structure around the oxygen and aluminum K edges of these filters. Thus, we are conducting a high spectral resolution calibration of the filters near these energies to resolve out extended flue structure and absorption lines.

Audley, Michael D.↗
NASA NTRS1999

Design and Performance of the Astro-E/XRS Signal Processing System

We describe the signal processing system of the Astro-E XRS instrument. The Calorimeter Analog Processor (CAP) provides bias and power for the detectors and amplifies the detector signals by a factor of 20,000. The Calorimeter Digital Processor (CDP) performs the digital processing of the calorimeter signals, detecting X-ray pulses and analyzing them by optimal filtering. We describe the operation of pulse detection, Pulse height analysis. and risetime determination. We also discuss performance, including the three event grades (hi-res mid-res, and low-res). anticoincidence detection, counting rate dependence, and noise rejection.

Boyce, Kevin R.↗
NASA NTRS1996

Properties of Slow-Mode Shocks in the Distant (>200 R(sub e)) Geomagnetic Tail

Two distant ISEE-3 geomagnetic tail passes have been examined to identify all slow-mode shocks present in the data. We find a total of 86 events from 439 plasmasheet/lobe crossings, using five criteria based on relations between the upstream lobe and the downstream plasmasheet magnetic field and plasma measurements. The statistical results of slow-mode shock parameters such as the angle between magnetic field and shock normal, Theta(sub bn), Alfven Mach number along the normal direction, M(sub an), and electron beta, Beta(sub e), are calculated and reported.

magnothermodynamic theory MHD geomagnetic tails sl↗
NASA NTRS2002

Compact holographic memory using E - O beam steering

An innovative holographic memory system has been developed at JPL for high-density and high speed data storage in a space environment. This system ulitlizes a newly developed electro-optic (E-O) beam steering technology for beam steering to enable high-speed random access memory read/write without moving parts. Recently, a compact CD-sized holographic memory broadboard has been developed and demonstrated for holographic data storage adn retrieval. Detail technical progress will be presented in this paper.

electo - optic (E - O ) beam↗
NASA NTRS2006

Impact of Rainfall on the Retrieval of Soil Moisture Using AMSR-E Data

Rainfall leads to errors and limitations on the soil moisture retrieval using satellite radiometry. To understand the impact of rainfall, we examined the temporal and spatial correlations between rainfall and soil moisture using AMSR-E (Advanced Microwave Scanning Radiometer-EOS) data. Scan by scan (swath basis) analyses were conducted to find the short time scale relationship between the two physical parameters. The retention of soil moisture after rainfall in different climatic regimes (e.g. humid and arid regions) was also examined.

rainfall↗
NASA NTRS2007

Discovery of a New Dusty B[E] Star in the Small Magellanic Cloud

We present new optical spectroscopic and Spitzer IRAC photometric observations of a B-type star in the SMC cluster NGC 346, NGC 346:KWBBe 200. We detect numerous Fe II, [O I], [Fe II], as well as strong P-Cygni profile H I emission lines in its optical spectrum. The star's near-IR color and optical to IR SED clearly indicate the presence of an infrared excess, consistent with the presence of gas and warm, T -800 K, circumstellar dust. Based on a crude estimate of the star's luminosity and the observed spectroscopic line profile morphologies, we find that the star is likely to be a B-type supergiant. We suggest that NGC 346:KWBBe 200 is a newly discovered B[e] supergiant star, and represents the fifth such object to be identified in the SMC.

Wisniewski, John P.↗
NASA NTRS2011

Land Surface Microwave Emissivities Derived from AMSR-E and MODIS Measurements with Advanced Quality Control

A microwave emissivity database has been developed with data from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and with ancillary land surface temperature (LST) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the same Aqua spacecraft. The primary intended application of the database is to provide surface emissivity constraints in atmospheric and surface property retrieval or assimilation. An additional application is to serve as a dynamic indicator of land surface properties relevant to climate change monitoring. The precision of the emissivity data is estimated to be significantly better than in prior databases from other sensors due to the precise collocation with high-quality MODIS LST data and due to the quality control features of our data analysis system. The accuracy of the emissivities in deserts and semi-arid regions is enhanced by applying, in those regions, a version of the emissivity retrieval algorithm that accounts for the penetration of microwave radiation through dry soil with diurnally varying vertical temperature gradients. These results suggest that this penetration effect is more widespread and more significant to interpretation of passive microwave measurements than had been previously established. Emissivity coverage in areas where persistent cloudiness interferes with the availability of MODIS LST data is achieved using a classification-based method to spread emissivity data from less-cloudy areas that have similar microwave surface properties. Evaluations and analyses of the emissivity products over homogeneous snow-free areas are presented, including application to retrieval of soil temperature profiles. Spatial inhomogeneities are the largest in the vicinity of large water bodies due to the large water/land emissivity contrast and give rise to large apparent temporal variability in the retrieved emissivities when satellite footprint locations vary over time. This issue will be dealt with in the future by including a water fraction correction. Also note that current reliance on the MODIS day-night algorithm as a source of LST limits the coverage of the database in the Polar Regions. We will consider relaxing the current restriction as part of future development.

Moncet, Jean-Luc↗