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Arnold, J. R.

Publications and source records attributed to Arnold, J. R..

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Some correlations between measurements by the Apollo gamma-ray spectrometer and other lunar observations

Observations by the Apollo 15 and 16 gamma-ray spectrometers are compared with those of a number of other experiments, both compositional and noncompositional. A general correspondence with topography is seen. The Van de Graaff area is a unique farside region with respect to observations by the laser altimeter, the subsatellite magnetometer, and the gamma-ray spectrometer. X-ray and alpha particle orbital measurements show a broad general agreement with gamma-ray data, although results from additional elements in the gamma-ray spectrum are needed to extend the comparison with X-ray data. A comparison of Th concentrations with those found at various landing sites shows generally good agreement, with the orbital values tending to be somewhat higher.

Trombka, J. I.↗
NASA NTRS1972

The cosmic gamma-ray spectrum between 0.3 and 27 MeV measured on the Apollo 15

The spectrum of the total (diffuse and discrete sources) cosmic gamma-ray background over the 0.3 to 27 MeV range was measured with a 7.0 cm diameter x 7.0 cm long uncollimated NaI(Tl) scintillation counter located on a boom 7.6 m from the Apollo 15 service module. Data on cosmic gamma-rays were taken during transearth coast at various boom extensions, detector gains, and with the plastic anticoincidence scintillator enabled and disabled.

Trombka, J. I.↗
NASA NTRS1972

Interaction of solar and galactic cosmic-ray particles with the moon.

Calculation of the rates of formation of radionuclides as a function of depth in the moon for bombardments by galactic-cosmic-ray particles and by solar protons. The fluxes and spectra of galactic-cosmic-ray particles and of solar protons as a function of depth in the moon are first determined semiempirically. For galactic cosmic rays, the model emphasizes the production of secondary particles and the attenuation of particles by nuclear interactions. Solar proton calculations cover a range of observed spectral parameters, and only ionization energy losses need be considered. The excitation functions for the nuclear reactions used in these calculations are presented. The calculated production rates are given for a range of depths in the moon and are compared with experimental results and with earlier calculations. The model can also be applied to other effects of particle bombardment.

Reedy, R. C.↗
NASA NTRS1972

Gamma-ray spectrometer experiment

The experiments in gamma-ray spectrometry to determine the geochemical composition of the lunar surface are reported. The theory is discussed of discrete energy lines of natural radioactivity, and the lines resulting from the bombardment of the lunar surface by high energy cosmic rays. The gamma-ray spectrometer used in lunar orbit and during transearth coast is described, and a preliminary analysis of the results is presented.

Arnold, J. R.↗
NASA NTRS1972

Gamma ray spectrometer experiment

The transearth coast period of the Apollo 16 mission provided an opportunity to study the astronomical sources of gamma radiation. This experiment was used to aid compositional identification for geochemical mapping of the lunar surface.

Arnold, J. R.↗
NASA NTRS1972

Cosmogenic nuclides in football-sized rocks.

The activity of long- and short-lived isotopes in a series of samples from a vertical column through the center of rock 14321 was measured. Rock 14321 is a 9 kg fragmental rock whose orientation was photographically documented on the lunar surface. Also investigated was a sample from the lower portion of rock 14310, where, in order to study target effects, two different density fractions (mineral separates) were analyzed. A few nuclides in a sample from the comprehensive fines 14259 were measured. This material has been collected largely from the top centimeter of the lunar soil. The study of the deep samples of 14321 and 14310 provided values for the activity of isotopes at points where only effects produced by galactic cosmic rays are significant.

Wahlen, M.↗
NASA NTRS1972

A first look at the lunar orbital gamma-ray data.

Preliminary review of data from the radioactivity relief map of the regions of the moon overflown by the Apollo 15 command module. The data represent count rates in the energy band from 0.55 to 2.75 MeV, appropriately corrected and averaged. Review results include the findings that: (1) the major concentrations of radioactivity in the area covered are in the region of Mare Imbrium and Oceanus Procellarum, (2) the highest regions are in the area of Aristarchus in Oceanus Procellarum and a region in eastern Mare Imbrium, and (3) the K/U ratio appears to be lower everywhere than that characteristic of the earth.-

Metzger, A. E.↗
NASA NTRS1969

Cosmochemistry

Cosmochemistry, discussing interdisciplinary nature, goals, nuclear roots, information sources, key concepts involving elements age and origin, nuclear species abundances, chemical fractionation, etc

Arnold, J. R.↗
NASA NTRS1968

Cosmic dust in the stratosphere.

Cosmic dust in one to 100 micron size range in stratosphere, noting balloon-borne collecting technique and upper limit on total terrestrial accretion rate

Arnold, J. R.↗