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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 217 records · Page 12
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NASA NTRS1973

Primary electron spectrometer, 18:63 UE: Electrostatic analyzer description and energy spectrum determination

The primary electron spectrometer used to detect auroral electrons on sounding rocket 18:63 UE is described. The spectrometer used exponentially decaying positive and negative voltages applied to spherical deflection plates for energy analysis. A method for determining the analyzer response which does not require the assumptions that the ratio of plate separation to mean radius, the entrance or the exit apertures are small is described. By comparison with experiment it is shown that the effect of neither entrance nor exit collimation can be ignored. The experimental and calculated values of the limiting orbits agree well. A non-iterative technique of unfolding the electron differential energy spectrum is described. This method does not require the usual assumption of a flat or histogram-type energy spectrum. The unfolded spectra using both this technique and one which assumes a flat spectrum are compared to actual input spectra. This technique is especially useful in analyzing peaked auroral electron energy spectra.

Pongratz, M. B.↗
NASA NTRS1973

A model for the pressure excitation spectrum and acoustic impedance of sound absorbers in the presence of grazing flow

The acoustic impedance of sound absorbers in the presence of grazing flow is essential information when analyzing sound propagation within ducts. A unification of the theory of the nonlinear acoustic resistance of Helmholtz resonators including grazing flow is presented. The nonlinear resistance due to grazing flow is considered to be caused by an exciting pressure spectrum produced by the interaction of the grazing flow and the jets flowing from the resonator orifices. With this exciting pressure spectrum the resonator can be treated in the same manner as a resonator without grazing flow but with an exciting acoustic spectrum.

Rice, E. J.↗
NASA NTRS1973

Analysis of the backscatter spectrum in an ionospheric modification experiment

Predictions of the backscatter spectrum are compared, including effects of ionospheric inhomogeneity with experimental observations of incoherent backscatter from an artificially heated region. Calculations show that the strongest backscatter echo received is not, in fact, from the reflection level, but from a region some distance below (about 0.5 km for an experiment carried out at Arecibo), where the pump wave from a HF transmitter approximately 100 kW) is below the threshold for parametric amplification. By taking the standing wave pattern of the pump into account, asymmetry is explained of the up-shifted and down-shifted plasma lines in the backscatter spectrum, and the several peaks typically observed in the region of the spectrum near the HF transmitter frequency.

Kim, H.↗
NASA NTRS1973

The galactic radio spectrum between 130 and 2600 kHz.

The IMP-6 radio astronomy experiment has provided new measurements of the galactic background spectrum at 22 frequencies between 130 and 2600 kHz. A highly accurate spectrum is presented which corresponds to the minimum galactic radiation observed with a short dipole antenna. The estimated maximum spectrum is presented also. The data demonstrate the need to include the effect of the ambient plasma on synchrotron emission in low-frequency galactic models.

Brown, L. W.↗
NASA NTRS1973

Observation of cosmic-ray particles with Z of 50 or greater and interpretation of the charge spectrum.

Large areas of plastic detectors and nuclear emulsions were exposed to the primary cosmic radiation on two high-altitude balloon flights in May 1968 and September 1969. From measurements on the tracks found in the scanning of the plastic detectors, events with charges Z greater than 50 were selected, and these data were consolidated with those from our earlier flights. Several conclusions can be drawn from the observed charge spectrum. The detection of trans-bismuth nuclei confirms earlier observations of these particles in the cosmic rays. However, no trans-uranium particles were observed. Detailed features of the charge spectrum cannot be explained by nuclei from r-process nucleosynthesis alone. Although the addition of particles following s-process abundances yields improved agreement, the spectrum appears more complicated than would result from a simple combination of r- and s-process abundances with identical propagation histories.

Blanford, G. E., Jr.↗
NASA NTRS1973

An unusual meteor spectrum

An extraordinary spectrum of a meteor at a velocity of about 18.5 + or - 1.0 km/s was observed with an image orthicon camera. The radiant of the meteor was at an altitude of about 49 deg. It was first seen showing a yellow red continuous spectrum alone at a height of 137 + or - 8 km which is ascribed to the first positive group of nitrogen bands. After the meteor had descended to 116 + or - 6 km above sea level it brightened rapidly from its previous threshold brightness into a uniform continuum, the D-line of neutral sodium appeared, and at height 105 + or - 5 km all the other lines of the spectrum also appeared. The continuum remained dominant to the end. Water of hydration and entrained carbon flakes of characteristic dimension about 0.2 micron or less are proposed as constituents of the meteoroid to explain these phenomena.

Cook, A. F.↗
NASA NTRS1973

The diffuse X-ray spectrum from 14 to 200 keV as measured on OSO-5

Evaluation of OSO-5 measurements of the energy spectrum of the diffuse component of the cosmic X-ray flux in the energy range from 14 to 200 keV. A detailed description is given of the X-ray detector employed and of the method of selection and pulse-height analysis of X-ray events. The method employed in eliminating noncosmic X-ray contributions to the total counting rate is discussed. The final energy spectrum is found to be best fitted by a power law which is in essential agreement with that obtained from OSO-3 by Schwartz et al. (1970), in spite of what is regarded as an erroneous correction procedure used by them. In particular, it is suggested that the break in the energy spectrum at 40 keV which they reported may have been produced by an erroneous correction for the radioactivity induced in the detector during each passage through the intense charged-particle fluxes in the South Atlantic Anomaly.

Dennis, B. R.↗
NASA NTRS1973

Energy spectrum and flux of 3- to 20-Mev neutrons and 1- to 10-Mev gamma rays in the atmosphere

An experiment is described which was designed to measure the neutron and gamma ray energy spectrums and fluxes in the energy intervals 3 to 20 MeV and 1 to 10 MeV, respectively. In addition, from the 3 to 20-MeV proton recoil spectrums it is possible to infer the shape of the neutron energy spectrum from 20 to 50 MeV. The detecting system utilized a separate charged particle rejection scheme and a two-parameter display system for the output from the pulse shape discrimination which separated gamma rays from neutrons (n). Two long-duration flights were made with this detector in 1970 at Palestine, Tex. (P sub c = 4.6 Gv) and at Ft. Churchill, Canada (P sub c = 0.3 Gv).

Klumpar, D. M.↗
NASA NTRS1974

Interstellar electron spectrum from the galactic non-thermal radio emission

A range of interstellar electron spectra at energies between 100 MeV and 5 GeV has been derived from an analysis of the observed galactic nonthermal radio spectrum and from consideration of the existing uncertainties in the other relevant physical parameters of the galaxy. We find that for energies larger than about 300 MeV the electron spectrum is uncertain to a factor of 4 due to uncertainties in the galactic magnetic field strength and the total line-of-sight emission length. The uncertainty in the electron spectrum increases towards lower energies, exceeding a factor of 50 near 100 MeV, primarily due to uncertainties in the galactic parameters affecting interstellar radio absorption.

Cummings, A. C.↗
NASA NTRS1974

The shape of the primary cosmic ray electron spectrum above 10 GeV

A balloon borne measurement of the cosmic ray electron spectrum above 10 GeV is reported in which two new techniques have been used to remove proton background contamination. First, the depth of the spectrometer on one of the flights was more than 40 radiation lengths, enabling hadronically and electromagnetically induced cascades to be differentiated for a subset of the data. Second, electromagnetic cascade starting points were determined to within about 0.1 radiation lengths based upon a calibration with electrons from 5.4 to 18 GeV at the Stanford Linear Accelerator. The resulting spectrum, when fitted with a power law, is steep, but the fit is marginal. A significantly better fit is achieved by assuming a model in which the spectrum is steepening in the measured region.

Silverberg, R. F.↗
NASA NTRS1974

Rigidity spectrum of z greater than or equal to 3 cosmic-ray nuclei in the range 4-285 GV and a search for cosmic antimatter

A measurement, using the magnetic emulsion spectrometer system, of the differential rigidity spectrum of Z greater than or equal to 3 nuclei of the galactic cosmic radiation is presented. The system was flown on Aug. 22, 1969, from Palestine, Texas. The instrument floated above 125,000 feet for eight hours. The data in the rigidity range 8-285 GV can be represented by a power-law spectrum in rigidity, J(rho) = A rho to the minus gamma power, with the exponent gamma = 2.6 plus or minus 0.10. The spectrum in the range 15-285 GV is also described by the same exponent, gamma = 2.6 plus or minus 0.25. The data below 8 GV cannot be described by the same power law without invoking solar modulation. A set of nonunique parameters for modulation are given. Upper limit for the fraction of antimatter in the rigidity range 4-125 GV is .005 with 95% confidence limit.

Golden, R. L.↗
NASA NTRS1974

Orbit-spectrum sharing between the fixed-satellite and broadcasting-satellite services at 12 GHz

This paper identifies and evaluates strategies for sharing the geostationary orbit in the band 11.7 to 12.2 GHz between domestic systems in the fixed-satellite and broadcasting-satellite services. The effectiveness of two distinct types of sharing strategies, referred to as spectrum division and orbit division, is determined for various deployments of selected baseline systems representing the two services and for various combinations of sharing tactics such as frequency interleaving, crossed-polarization operation, and crossed-beam operation. Effectiveness is measured by the 'utilization factor', defined as the number of channels provided by the baseline systems when using an assigned share of the orbit-spectrum resource, relative to what they could provide if given the entire resource. Computer simulation is used to verify the intra- and interservice interference compatibility of the assumed deployments. It is concluded that total utilization factors close to 100 percent can be achieved with both spectrum-division and properly-chosen orbit-division strategies.

Reinhart, E. E.↗
NASA NTRS1975

The energy spectrum of the Perseus cluster of galaxies

A one-dimensional focusing X-ray telescope has been used to measure the spatial structure and energy spectrum of the Perseus cluster in the 0.5-4.5 keV X-ray range. A significant variation is observed in the X-ray spectrum from different regions of the cluster, indicating different possible emission mechanisms. The spectrum from the region centered on NGC 1275 appears harder and more cut off at low energy than that of the remainder of the cluster.

Wolff, R. S.↗
NASA NTRS1975

The soft X-ray spectrum of the Perseus cluster

The X-ray spectrum of the Perseus cluster in the range 0.1-4.0 keV has been observed. Contrary to the results of previous low-energy rocket observations, no large flux of soft X-rays was found. The X-ray spectrum from 0.1 to 56 keV is consistent with bremsstrahlung from an intracluster gas with T approximately equal to 100 million K. attenuated by the interstellar column density inferred from 21-cm observations. The low-energy X-ray spectrum is not consistent with a nonthermal power-law model with the same slope as that observed at higher energies. The mass of hot intracluster gas required to produce the observed X-ray flux is a small fraction of the gravitational binding mass. The soft X-ray flux, when combined with limits on the radio flux, implies that the cluster is not gravitationally bounded by ionized gas at any temperature.

Davidsen, A.↗
NASA NTRS1976

Shuttle spectrum despreader

The results of the spread spectrum despreader project are reported and three principal products are designed and tested. The products are, (1) a spread spectrum despreader breadboard, (2) associated test equipment consisting of a spectrum spreader and bit reconstruction/error counter and (3) paper design of a Ku-band receiver which would incorporate the despreader as a principal subsystem. The despreader and test set are designed for maximum flexibility. A choice of unbalanced quadriphase or biphase shift keyed data modulation is available. Selectable integration time and threshold voltages on the despreader further lend true usefulness as laboratory test equipment to the delivered hardware.

Source record↗
NASA NTRS1975

Ultraviolet solar identifications based on extended absorption series observed in the laboratory spectrum of Si I

The absorption spectrum of Si I in the wavelength region between 1500 and 1900 A has been photographed at high resolution. The silicon vapor was produced in a 122-cm-long King furnace at 1800 to 2300 C. Forty-two Rydberg series have been observed from the ground state terms 3p(2)3P and 1D to terms associated with the 3pns and 3pnd configurations. All of the series from these configurations with J less than 4 have been extended with the 3pnd 3D(3) levels reaching n = 56. Numerous perturbations have been observed. This laboratory work has provided the basis for extending the identification of silicon lines in the solar spectrum. Nearly all lines found in the laboratory spectrum are also found in rocket spectrograms of the solar chromosphere. More than 300 lines have been attributed to Si I. The excellent correlation between laboratory and solar Si I lines is illustrated.

Moore, C. E.↗
NASA NTRS1975

Experimental observation of the absorption spectrum of Fe I in the region 1600-900 A

Laboratory observations of the absorption spectrum of Fe I in the vacuum UV region between 900 and 1600 A are reported. The spectrum was obtained by applying the flash pyrolysis technique to iron foils of 1-micron thickness; the continuum was provided by a Garton source used in series with a spark gap. Plots which show several strong autoionized lines superimposed on a smooth continuum are presented along with a table of narrow lines between 904.900 and 1380.208 A. It is noted that the present spectrum is in agreement with others that have been obtained with the flash pyrolysis technique.

Tondello, G.↗
NASA NTRS1975

The radio spectrum of Vela supernova and its implication on the propagation of cosmic rays from sources

A detailed analysis of the radio spectrum of the Vela supernova remnant has been carried out to show that the positive spectral shape below 80 MHz can be understood on the basis of Razin effect. This result requires most of the gas in the remnant to be stratified into high density clumps with intense magnetic fields and large cosmic ray densities. The free-free emission is found to be partly responsible for the observed flat radio spectrum. In order to account for both the gamma ray flux above 100 MeV and the radio spectrum, the equipartition between the cosmic ray density and magnetic field seems to break down. The total cosmic ray energy residing in the supernova is found to be about ten to the forty-ninth ergs, which is much smaller than the value obtained without taking into account the stratification of gas.

Stephens, S. A.↗