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  • Other Sources  (145)
  • SOLAR PHYSICS  (65)
  • INSTRUMENTATION AND PHOTOGRAPHY  (40)
  • MECHANICAL ENGINEERING  (40)
  • Polymer and Materials Science
  • 1980-1984  (145)
  • 1945-1949
  • 1981  (145)
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  • 1980-1984  (145)
  • 1945-1949
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  • 1
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    Evaluation of RCA thinned buried channel charge-coupled devices /CCDs/ for scientific applications (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: An experimental version of a thinned illuminated buried-channel 512 x 320 pixel CCD with reduced amplifier input capacitance has been produced which is characterized by lower readout noise. Changes made to the amplifier are discussed, and readout noise measurements obtained by several different techniques are presented. The single energetic electron response of the CCD in the electron-bombarded mode and the single 5.9 keV X-ray pulse height distribution are reported. Results are also given on the dark current versus temperature and the spatial frequency response as a function of signal level.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Solid state imagers for astronomy; June 10, 11, 1981; Cambridge, MA
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Soft X-ray and XUV imaging with a charge-coupled device /CCD/-based detector (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A soft X-ray/XUV imaging camera which uses a thinned, back-illuminated, all-buried channel RCA CCD for radiation sensing has been built and tested. The camera is a slow-scan device which makes possible frame integration if necessary. The detection characteristics of the device have been tested over the 15-1500 eV range. The response was linear with exposure up to 0.2-0.4 erg/sq cm; saturation occurred at greater exposures. Attention is given to attempts to resolve single photons with energies of 1.5 keV.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Solid state imagers for astronomy; June 10, 11, 1981; Cambridge, MA
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    NASA TECHNICAL REPORTS
  • 3
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    Thermal iron ions in high speed solar wind streams. II - Temperatures and bulk velocities (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Mitchel and Roelof (1980) reported the detection of iron in high speed solar wind flows using the small, but finite sensitivity of solid state detectors to Fe ions in the low energy (50-200 keV protons) L1 channel of the NOAA/JHU energetic particle experiment (EPE). In the current investigation, the EPE response is modeled to a convected Maxwellian to obtain the thermal velocity, flow angle, and bulk velocity of the iron distribution. It is assumed that the iron bulk flow velocity can be represented as a vector sum of the hydrogen bulk velocity and an interplanetary magnetic field (IMF) aligned velocity increment. It is found that the velocity increment is smaller than the local Alfven speed in magnitude, and that the iron thermal velocity is comparable with or greater than the proton thermal velocity, with the 'thermal' velocity defined as the square root of 2kT/m.
    Keywords: SOLAR PHYSICS
    Type: AD-A105214 , AFGL-TR-81-0279 , Geophysical Research Letters; 8; July 198
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    NASA TECHNICAL REPORTS
  • 4
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    Echelle spectroscopy with a charge-coupled device /CCD/ (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The recent availability of large format CCD's with high quantum efficiency makes it possible to achieve significant advances in high dispersion astronomical spectroscopy. An echelle CCD combination excels or equals other techniques presently available, and offers the advantage of complete spectral coverage of several thousand Angstroms in a single exposure. Attention is given to experiments which were conducted with a CCD camera head and an echelle spectrograph on a 4-meter telescope. It was found possible to achieve a signal-to-noise ratio of 150/1 on a 13th magnitude star at 6000 A in a two-hour exposure at 0.16 A/pixel, limited primarily by photon statistics. For fainter objects, readout noise is the limiting factor in precision. For 20 electron rms readout noise, an S/N = 15/1 at 18th magnitude is expected, all other things being equal.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Solid state imagers for astronomy; June 10, 11, 1981; Cambridge, MA
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    NASA TECHNICAL REPORTS
  • 5
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    Large loop thermal models of solar hard X-ray bursts (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results for small loop thermal models of hard X-ray bursts are extended to large loops. In this model a magnetic arch with a coronal length of 45,000 km has the electrons near the top heated to temperatures above 1 billion K. The resulting conduction fronts which form are dominated by collisionless processes and travel down the arch to the transition region and chromosphere where they evaporate off part of the latter. This relatively cool material travels back up the loop and eventually quenches the source for energy injection times of order 10 sec. Most of the X-ray emission comes from the footpoints of the arch over most of the source lifetime and the spectrum is a power law with a typical spectral index of 3.0. Even though the efficiency gain in this model is only 2.8, it is much easier from the point of view of plasma physics to heat all the electrons in a plasma than to accelerate a substantial fraction of them.
    Keywords: SOLAR PHYSICS
    Type: ESA Plasma Astrophys.; p 401-404
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  • 6
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    Eclipse radius measurements (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Methods for predicting the path edges and reducing observations of total solar eclipses for determining variations of the solar radius are described. Analyzed observations of the 1925 January eclipse show a 0.7 (arc second) decrease in the solar radius during the past fifty years.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 117-120
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    The sunspot chromosphere-corona transition region (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Data from simultaneous readings of the line intensities, Doppler shifts, and line widths of a sunspot ion emission lines between 1170-1700 A are reported. Subsonic and supersonic flows were observed in the same line of sight above the umbra. A reduction of coronal plasma over sunspots with an electron temperature exceeding 1,000,000 K was confirmed, concurrent with enhanced emission from the transition region plasma in the temperature range 200,000-1,000,000 K. The differential emission measure is noted to have been caused to shift because of the enhancement of the transition region plasma emission, where radiative losses dominated the energy balance. Calculations of the energy balance also indicated that a detected divergence in the enthalpy flux for the umbral downflows could balance the radiative losses in the electron temperature range 30,000-200,000 K.
    Keywords: SOLAR PHYSICS
    Type: The physics of sunspots; Conference; Jul 14, 1981 - Jul 17, 1981; Sunspot, NM
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    NASA TECHNICAL REPORTS
  • 8
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    Energetic electrons and plasma waves associated with a solar type III radio burst (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Detailed in situ observations from the ISEE 3 spacecraft of energetic electrons, plasma waves, and radio emission for the type II solar radio burst of February 17, 1979, are presented. The reduced, one-dimensional electron distribution function is constructed as a function of time. Since the faster electrons arrive before the slower ones, a bump on tail distribution forms which is unstable to the growth of Langmuir waves. The plasma wave growth computed from the distribution function agrees well with the observed onset of the Langmuir waves, and there is qualitative agreement between variations in the plasma wave levels and in the development of regions of positive slope in the function. The evolution of the function, however, predicts far higher plasma wave levels than those observed. The maximum levels observed are approximately equal to the threshold for nonlinear wave processes, such as oscillation two-stream instability and soliton collapse.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 251
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  • 9
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    Application of a laser interferometer skin-friction meter in complex flows (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The application of a nonintrusive laser-interferometer skin-friction meter, which measures skin friction with a remotely located laser interferometer that monitors the thickness change of a thin oil film, is extended both experimentally and theoretically to several complex wind-tunnel flows. These include two-dimensional seperated and reattached subsonic flows with large pressure and shear gradients, and two and three-dimensional supersonic flows at high Reynolds number, which include variable wall temperatures and cross-flows. In addition, it is found that the instrument can provide an accurate location of the mean reattachment length for separated flows. Results show that levels up to 120 N/sq m, or 40 times higher than previous tests, can be obtained, despite encountering some limits to the method for very high skin-friction levels. It is concluded that these results establish the utility of this instrument for measuring skin friction in a wide variety of flows of interest in aerodynamic testing.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ICIASF ''81; International Congress on Instrumentation in Aerospace Simulation Facilities; Sep 30, 1981; Dayton, OH
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Measurement of the solar constant (1981)
    In:  CASI
    Details
    Publication Date: 2006-06-04
    Description: The absolute value of the solar constant and the long term variations that exist in the absolute value of the solar constant were measured. The solar constant is the total irradiance of the Sun at a distance of one astronomical unit. An absolute radiometer removed from the effects of the atmosphere with its calibration tested in situ was used to measure the solar constant. The importance of an accurate knowledge of the solar constant is emphasized.
    Keywords: SOLAR PHYSICS
    Type: NASA. Marshall Space Flight Center Spacelab Mission 1 Expt. Descriptions; 3 p
    Format: text
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