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  • 1
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    Crystal activation experiment MA-151 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The crystal activation experiment consisted of two sample packages that were flown in the command module and returned to earth for analysis of the radioactivity induced in them during the flight. The objective of the experiment was to define the background caused by detector activation that interferes when gamma radiation is measured in the 0.02- to 10-megaelectronvolt range from earth orbit. Preliminary results show that the activation of the NaI(Tl) crystal was a factor of 3 below that from a similar measurement on Apollo 17. The identification of certain species and the level of activation observed show an important contribution from the interactions of thermal and energetic neutrons produced as secondaries in the spacecraft. That the activation was reduced by only a factor of 3 compared with the Apollo 17 experiment, despite the geomagnetically shielded orbit, possibly indicates more efficient secondary neutron production by the more energetic cosmic rays.
    Keywords: SPACE RADIATION
    Type: Apollo-Soyuz Test Project; 10 p
    Format: text
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  • 2
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    Ames collaborative study of cosmic ray neutrons (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of a collaborative study to define both the neutron flux and the spectrum more precisely and to develop a dosimetry package that can be flown quickly to altitude for solar flare events are described. Instrumentation and analysis techniques were used which were developed to measure accelerator-produced radiation. The instruments were flown in the Ames Research Center high altitude aircraft. Neutron instrumentation consisted of Bonner spheres with both active and passive detector elements, threshold detectors of both prompt-counter and activation-element types, a liquid scintillation spectrometer based on pulse-shape discrimination, and a moderated BF3 counter neutron monitor. In addition, charged particles were measured with a Reuter-Stokes ionization chamber system and dose equivalent with another instrument. Preliminary results from the first series of flights at 12.5 km (41,000 ft) are presented, including estimates of total neutron flux intensity and spectral shape and of the variation of intensity with altitude and geomagnetic latitude.
    Keywords: SPACE RADIATION
    Type: NASA-TM-X-3329 , A-6139
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  • 3
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    Local and large scale galactic gamma-ray emission (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A study of the gas-to-dust ratio suggests that interstellar reddening may provide an accurate way of assessing column densities in various directions in the Galaxy. A gamma ray intensity of 7.25 x 10 to the -5th E sub B-V photon/sq cm/s/sterad is predicted for regions of the Galaxy where the medium cosmic ray density is equal to that observed close to the sun. It is found that in the longitude range of about 0-180 degrees, the large scale cosmic ray distribution producing the gamma rays follows that of extreme population I stars put in evidence by giant H II regions, and that of molecular hydrogen traced by carbon monoxide emission. The gamma-ray production exhibits a maximum at R roughly equal to 5 kpc, and practically vanishes at R not less than 11 kpc, beyond the location of the outermost H II regions.
    Keywords: SPACE RADIATION
    Type: Astronomy and Astrophysics; 50; 2, Ju; July 197
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  • 4
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    Solar modulation and a galactic origin for the anomalous component observed in low-energy cosmic rays (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The current theory of solar modulation can be used to argue that the cosmic-ray component at low energies, which is observed to have an anomalous composition, is not of galactic origin, i.e., it is not a component of the galactic cosmic-ray flux. The current theory predicts, from quite general considerations, that an unreasonably large intensity of cosmic rays, by many orders of magnitude, would be required in the interstellar medium to account for the observed fluxes. Conceivably, the current modulation theory could be modified so that only reasonable interstellar fluxes are predicted. One such modification involves an unusual scheme for particle diffusion in the interplanetary medium. Particles are assumed to diffuse not as a result of their own motion among small-scale irregularities in the magnetic field, but rather in a process in which they are trapped between time-varying constrictions in the large-scale field.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 206; May 15
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  • 5
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    Photonuclear interactions of ultrahigh energy cosmic rays and their astrophysical consequences (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Results are presented for detailed Monte Carlo calculations of the interaction histories of ultrahigh-energy cosmic-ray nuclei with intergalactic radiation fields, using improved estimates of these fields and empirical determinations of photonuclear cross sections, including multinuclear disintegrations for nuclei up to Fe-56. Intergalactic and galactic energy-loss rates and nucleon-loss rates for nuclei up to Fe-56 are also given. Astrophysical implications are discussed in terms of expected features in the cosmic-ray spectrum between 10 to the 18th and 10 to the 21st power eV for the universal and supercluster origin hypotheses. The results of these calculations indicate that ultrahigh-energy cosmic rays cannot be universal in origin regardless of whether they are protons or nuclei. Both the supercluster and galactic origin hypotheses, however, are possible regardless of nuclear composition.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 205; Apr. 15
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  • 6
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    Three-dimensional interplanetary stream magnetism and energetic particle motion (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Cosmic rays interact with mesoscale configurations of the interplanetary magnetic field. A technique is presented for calculating such configurations in the inner solar system, which are due to streams and source conditions near the sun, and maps of magnetic field are constructed for some plausible stream and source conditions. One effect of these mesoscale configurations on galactic cosmic rays is shown to be an out-of-the-ecliptic gradient drift sufficient to explain Forbush decreases. The effects on solar energetic particles include small polar drifts due to the field gradients and a possibly large modification of the time-intensity profiles and anisotropy characteristics due to the formation of mirror configurations in space. If a diffusion model is applicable to solar particles, the true diffusion coefficient will be masked by the effects of streams. A conceptual model which incorporates these ideas and those of several other models is presented.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 81; May 1
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  • 7
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    Advances in gamma-ray burst astronomy (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The paper reviews the current status of observational research into the highly puzzling problem of cosmic gamma-ray bursts. Up to now there is no convincing temporal or spatial correlation with any known celestial processes or objects. The typical burst source strength is somewhere between 10 to the 26th power ergs and 10 to the 52nd power ergs. A list of 39 confirmed and 9 unconfirmed cosmic gamma-ray bursts observed by satellite is given, showing times of occurrence and in some cases, the size in erg per square centimeter. Several approaches to the problem of source object identification are discussed: (1) accumulation of observation statistics with their present poor resolution and research for correlative phenomena, (2) mapping out celestial source distributions with moderate resolution in order to search for galactic or other anisotropies in direction or to look for repeating source regions, and (3) very high-accuracy localization of the source directions of one or several bursts in order to pinpoint a tiny fraction of the celestial sphere for correlative radio, optical and X-ray studies. Planned future instrumentation for deep space probes and multiple-balloon studies is described.
    Keywords: SPACE RADIATION
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  • 8
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    A nonlinear theory of cosmic-ray pitch-angle diffusion in homogeneous magnetostatic turbulence (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A plasma strong turbulence, weak coupling, theory is applied to the problem of cosmic-ray pitch-angle scattering in magnetostatic turbulence. The theory used is a rigorous generalization of Weinstock's 'resonance broadening' theory and contains no ad hoc approximations. A detailed calculation is presented for a model of 'slab' turbulence with an exponential correlation function. The results agree well with numerical simulations. The rigidity dependence of the pitch-angle scattering coefficient differs from that found by previous researchers. The differences result from an inadequate treatment of particle trajectories near 90 deg pitch angle in earlier work.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 204; Mar. 15
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  • 9
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    Reanalysis of the Apollo cosmic gamma-ray spectrum in the 0.3 to 10 MeV energy region (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Additional data obtained from the Apollo-16 and -17 missions, together with collateral calculations on background radiation effects, have enabled an improved subtraction of unwanted backgrounds from the diffuse cosmic gamma-ray data previously reported from Apollo-15. As a result, the 1- to 10-MeV spectrum is lowered significantly and connects smoothly with recent data at other energies. The inflection reported previously is much less pronounced and has no more than a 1.5-sigma significance. Sky occultation by the Apollo-16 spacecraft shows the bulk of the 0.3- to 1-MeV radiation to be diffuse. The analysis of spurious backgrounds points to important improvements for future experiments designed for this spectral region.
    Keywords: SPACE RADIATION
    Type: NASA-TM-X-71150 , X-682-76-128
    Format: application/pdf
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  • 10
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    Hard X-ray imaging facility for space shuttle: A scientific and conceptual engineering study (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A shuttle-accommodated instrument for imaging hard X-rays in the study of nonthermal particles and high temperature particles in various solar and cosmic phenomena was defined and its feasibility demonstrated. The imaging system configuration is described as well as the electronics, aspect systems, mechanical and thermal properties and the ground support equipment.
    Keywords: SPACE RADIATION
    Type: NASA-CR-156736
    Format: application/pdf
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