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NASA NTRS1981

SAS 2 observations of the earth albedo gamma radiation above 35 MeV

The earth albedo gamma radiation above 35 MeV in the equatorial region is investigated using observations from the second Small Astronomy Satellite. The zenith angle distribution of the gamma radiation has a peak toward the horizon which is about an order of magnitude more intense than the radiation coming from the nadir, and nearly two orders of magnitude more intense than the gamma radiation from most parts of the sky. The gamma radiation originating from the western horizon is a factor of four more intense than the radiation from the eastern horizon and a factor of three more intense than that from the northern and southern directions. This reflects the geomagnetic effects on the incident cosmic rays whose interactions produce the albedo gamma rays. The variation of the upcoming gamma ray intensity with vertical cutoff rigidity is consistent with the empirical relationship found by Gur'yan et al. (1979).

Thompson, D. J.↗

NASA NTRS1977

The constitution of cometary nuclei

The nongravitational term in the expression for the total force acting on a comet is calculated, and an upper limit is obtained for the product of the radial nongravitational term times the radius times the square root of the albedo. This condition is satisfied for ten periodic comets with q no greater than 1.5 AU, and the activity of these comets is consistent with control by H2O ice. Some of the comets must be spotty to account for their low albedo values. The effect of cosmic rays on comets, leading to frosting of their surface, is discussed.

Whipple, F. L.↗

NASA NTRSDate not supplied

The Ionizing Radiation Environment on the Moon

The ionizing radiation environment on the moon that contributes to the radiation hazard for astronauts consists of galactic cosmic rays, solar energetic particles and albedo particles from the lunar surface. We will present calculations of the absorbed dose and the dose equivalent to various organs in this environment during quiet times and during large solar particle events. We will evaluate the contribution of solar particles other than protons and the contributions of the various forms of albedo. We will use the results to determine which particle fluxes must be known in order to estimate the radiation hazard.

J. H. Adams Jr.↗

NASA NTRS2015

November 2013 Analysis of High Energy Electrons on the Japan Experimental Module (JEM: Kibo)

Albedo (precipitating/splash) electrons, created by galactic cosmic rays (GCR) interaction with the upper atmosphere move upwards away from the surface of the earth. In the past validation work these particles were often considered to have negligible contribution to astronaut radiation exposure on the International Space Station (ISS). Estimates of astronaut exposure based on the available Computer Aided Design (CAD) models of ISS consistently underestimated measurements onboard ISS when the contribution of albedo particles to exposure were neglected. Recent measurements of high energy electrons outside ISS Japan Experimental Module (JEM) using Exposed Facility (EF), Space Environment Data Acquisition Equipment - Attached Payload (SEDA-AP) and Standard DOse Monitor (SDOM), indicates the presence of high energy electrons at ISS altitude. In this presentation the status of these energetic electrons is reviewed and mechanism for the creation of these particles inside/outside South Atlantic Anomaly (SAA) region explained. In addition, limited dosimetric evaluation of these electrons at 600 MeV and 10 GeV is presented.

Badavi, Francis F.↗

NASA NTRS1974

An investigation of the cosmic radiation in the vicinity of the moon on the Luna 10, 11, and 12 artificial lunar satellites

Research on the primary cosmic radiation and solar cosmic rays from the Luna 10, 11, and 12 artificial lunar satellites is reviewed. Data on the vertical distribution of cosmic rays above the moon's surface are presented, and the albedo for the primary radiation is determined. The fluxes of electrons with energies from 30 to 300 keV were registered in the solar cosmic rays. Rapid variations of the electron flux were observed. The angular distributions of 0.5-10 MeV protons moving together with the corpuscular streams responsible for Forbush decreases were investigated.

Grigorov, N. L.↗

NASA NTRS2001

Predictions of secondary neutrons and their importance to radiation effects inside the International Space Station

As part of a study funded by NASA MSFC to assess thecontribution of secondary particles in producing radiation damage to optoelectronics devices located on the International Space Station (IS), Monte Carlo calculations have been made to predict secondary spectra vs. shielding inside ISS modules and in electronics boxes attached on the truss (Armstrong and Colborn, 1998). The calculations take into account secondary neutron, proton, and charged pion production from the ambient galactic cosmic-ray (GCR) proton, trapped proton, and neutron albedo environments. Comparisons of the predicted neutron spectra with measurments made on the Mir space station and other spacecraft have also been made (Armstrong and Colborn, 1998). In this paper, some initial results from folding the predicted neutron spectrum inside ISS modules from Armstrong and Colborn (1998) with several types of radiation effects response functions related to electronics damage and astronaut-dose are given. These results provide an estimate of the practical importance of neutrons compared to protons in assessing radiation effects for the ISS. Also, the important neutron energy ranges for producing these effects have been estimated, which provides guidance for onboard neutron measurement requirements.

Neutrons↗

NASA NTRS1973

Shaped scintillation detector systems for measurements of gamma ray flux anisotropy

The detection efficiencies of cylindrical detectors for various gamma ray photon angular distributions were studied in the energy range from .10 Mev to 15 Mev. These studies indicate that simple detector systems on small satellites can be used to measure flux anisotropy of cosmic gamma rays and the angular distribution of albedo gamma rays produced in planetary atmospheres. The results indicate that flat cylindrical detectors are most suitable for measuring flux anisotropy because of their angular response function. A general method for calculating detection efficiencies for such detectors is presented.

Trombka, J. I.↗

NASA NTRS1979

Predictions of induced background radiations at gamma/X-ray experiment envelopes in NASA spacecraft

This work seeks to predict secondary radiation levels induced in spacecraft structures by space protons. The radiations analyzed are secondary neutrons from spallation and evaporation reactions and gamma and beta rays from the decay of induced radioactivity, as sources of interfering background to spaceborne measurements of galactic and planetary gamma rays below 10 MeV. The spacecraft considered are the Multi-Mission Spacecraft (MMS) and the Space Shuttle, modeled as spherical shells. The proton environment is that of the South Atlantic Anomaly, as well as cosmic ray protons. The induced radioactivity is analyzed in terms of its interference with various gamma-ray lines of astrophysical interest, as well as its contribution to several spectral regions of the gamma-ray continuum. The buildup of the line and continuum radioactivity background is predicted for a period of nearly 9 months in orbit (approximately 4100 orbits). In addition, background contributions from cosmic ray electron bremsstrahlung and earth gamma-ray albedo are estimated.

Fischbein, W. L.↗

NASA NTRS1975

Apollo 17 mission Report. Supplement 6: Calibration results for gamma ray spectrometer sodium iodide crystal

A major difficulty in medium energy gamma-ray remote sensing spectroscopy and astronomy measurements was the high rate of unwanted background resulting from the following major sources: (1) prompt secondary gamma-rays produced by cosmic-ray interactions in satellite materials; (2) direct charged-particle counts; (3) radioactivity induced in the detector materials by cosmic-ray and trapped protons; (4) radioactivity induced in detector materials by the planetary (e.g., earth or moon) albedo neutron flux; (5) radioactivity induced in the detector materials by the interaction of secondary neutrons produced throughout the spacecraft by cosmic-ray and trapped proton interactions; (6) radioactivity induced in spacecraft materials by the mechanisms outlined in 3, 4, and 5; and (7) natural radioactivity in spacecraft and detector materials. The purpose of this experiment was to obtain information on effects 3, 4, and 5, and from this information start developing calculational methods for predicting the background induced in the crystal detector in order to correct the Apollo gamma-ray spectrometer data for this interference.

Dyer, C.↗

NASA NTRS1976

A mechanism for inducing climatic variations through ozone destruction: Screening of galactic cosmic rays by solar and terrestrial magnetic fields

A perturbation analysis, allowing for temperature and opacity feedbacks, is developed to calculate depletions in the O3 abundance and reductions of stratospheric solar heating that result from increases in NOx concentration. A pair of perturbation coefficients give the reduction in O3 and temperature through the stratosphere for a specified NOx increase. This type of analysis illustrates the tendency for various levels to self-heal when a perturbation occurs. Physical arguments indicate that the expected sign of the climatic effect is correct, with colder surface temperatures produced by reduced magnetic shielding. In addition, four qualitative reasons are suggested for thinking that significant ozone reductions by cosmic ray influxes will lead to an increased terrestrial albedo from stratospheric condensation. In this view, long-term (approximately 10,000 years) climatic changes have resulted from secular geomagnetic variations while shorter (approximately 100 years) excursions are related to changes in solar activity.

Chamberlain, J. W.↗

NASA NTRS2001

Neutron Environment Calculations for Low Earth Orbit

The long term exposure of astronauts on the developing International Space Station (ISS) requires an accurate knowledge of the internal exposure environment for human risk assessment and other onboard processes. The natural environment is moderated by the solar wind, which varies over the solar cycle. The HZETRN high charge and energy transport code developed at NASA Langley Research Center can be used to evaluate the neutron environment on ISS. A time dependent model for the ambient environment in low earth orbit is used. This model includes GCR radiation moderated by the Earth's magnetic field, trapped protons, and a recently completed model of the albedo neutron environment formed through the interaction of galactic cosmic rays with the Earth's atmosphere. Using this code, the neutron environments for space shuttle missions were calculated and comparisons were made to measurements by the Johnson Space Center with onboard detectors. The models discussed herein are being developed to evaluate the natural and induced environment data for the Intelligence Synthesis Environment Project and eventual use in spacecraft optimization.

Clowdsley, M. S.↗

NASA NTRS1973

Solar and geomagnetic modulation of low-energy secondary cosmic ray electrons.

Balloon exposures of hodoscope instruments at Churchill, Manitoba; Minneapolis, Minnesota; and Sioux Falls, South Dakota, have established that the flux of return albedo electrons does not depend upon launch latitude and varies with solar modulation in proportion to the intensity of atmospheric secondary electrons. Only one flight out of 21 showed any indication of a magnetospheric electron flux significantly in excess of that attributable to albedo. Diurnal changes in geomagnetic cutoffs exhibit marked variability from day to day, as was illustrated by one flight in which a low cutoff was observed at Churchill throughout the daytime hours. The intensity increase of 15- to 65-MeV primary cosmic ray electrons due to solar modulation was no more than a factor of 2 from 1969-1970 to 1971.

Luhmann, J. G.↗

NASA NTRS1987

Measurements of background gamma radiation on Spacelab 2

A nuclear radiation monitor (NRM) which was flown as part of the verification instrumentation on the Spacelab 2 mission (July 29 - August 6, 1985) recorded spectra every 20 seconds and counting rates in coarse energy bands on finer time scales. The gamma radiation environment on Spacelab is characterized by cosmic-ray and trapped proton secondary radiation in the Spacelab/Shuttle, earth albedo radiation, and delayed induced radioactivity in the detector and surrounding materials. It is found that passages through South Atlantic Anomaly protons produce a well-defined background enhancement.

Fishman, G. J.↗

NASA NTRS1977

Cosmic diffuse gamma rays from 2 to 25 MeV

Results are reported for measurements of cosmic diffuse gamma rays performed with a double Compton scatter gamma-ray telescope flows aboard a balloon at 3.5-g/sq cm residual atmosphere. The operation and calibration of the telescope are briefly reviewed, unwanted backgrounds are identified, and the only significant background for the telescope used is shown to arise from the interaction of albedo neutrons with hydrogen and carbon in one of the liquid scintillators. The fluxes of cosmic diffuse gamma rays with energies of 2 to 3, 3 to 5, 5 to 7, 7.5 to 10 MeV are listed, and upper limits are provided for energies of 10 to 15 and 15 to 25 MeV. These data are compared with numerous previous measurements, and no indication is found that the diffuse radiation is statistically different from isotropic. Upper limits are placed on the gamma-ray fluxes (mainly 3 to 25 MeV) from various localized sources.

White, R. S.↗

NASA NTRS1984

Measuring planetary neutron albedo fluxes by remote gamma-ray sensing

In order to measure the planetary neutron albedo fluxes, a neutron-absorbing shield which emits gamma rays of characteristic energy and serves as a neutron detector, is added to a gamma-ray spectrometer (GRS). The gamma rays representing the neutron flux are observed against interference consisting of cosmic gamma rays, planetary continuum and line emission, and gamma rays arising from the interaction of cosmic rays with the GRS and the spacecraft. The uncertainty and minimum detection limits in neutron albedo fluxes are calculated for two missions, a lunar orbiter and a comet nucleus rendezvous. A GRS on a lunar orbiter at 100 km altitude detects a thermal neutron albedo flux as low as 0.002/sq cm/s and an expected flux of about 0.6/sq cm/s is measured with an uncertainty of 0.001/sq cm/s, for a 100 h observation period. For the comet nucleus, again in a 100 h observing period, a thermal neutron albedo flux is detected at a level of 0.006/sq cm/s and an expected flux of about 0.4/sq cm/s is measured with an uncertainty of 0.004/sq cm/s. The expanded geological capabilities made possible by this technique include improvements in H sensitivity, spatial resolution, and measurement depth; and an improved model of induced gamma-ray emission.

Haines, E. L.↗

NASA NTRS2009

Photon Luminescence of the Moon

Luminescence is typically described as light emitted by objects at low temperatures, induced by chemical reactions, electrical energy, atomic interactions, or acoustical and mechanical stress. An example is photoluminescence created when photons (electromagnetic radiation) strike a substance and are absorbed, resulting in the emission of a resonant fluorescent or phosphorescent albedo. In planetary science, there exists X-ray fluorescence induced by sunlight absorbed by a regolith a property used to measure some of the chemical composition of the Moon s surface during the Apollo program. However, there exists an equally important phenomenon in planetary science which will be designated here as photon luminescence. It is not conventional photoluminescence because the incoming radiation that strikes the planetary surface is not photons but rather cosmic rays (CRs). Nevertheless, the result is the same: the generation of a photon albedo. In particular, Galactic CRs (GCRs) and solar energetic particles (SEPs) both induce a photon albedo that radiates from the surface of the Moon. Other particle albedos are generated as well, most of which are hazardous (e.g. neutrons). The photon luminescence or albedo of the lunar surface induced by GCRs and SEPs will be derived here, demonstrating that the Moon literally glows in the dark (when there is no sunlight or Earthshine). This extends earlier work on the same subject [1-4]. A side-by-side comparison of these two albedos and related mitigation measures will also be discussed.

Wilson, T.L.↗

NASA NTRS1984

The 1984 ASEE-NASA summer faculty fellowship program (aeronautics and research)

The 1984 NASA-ASEE Faculty Fellowship Program (SFFP) is reported. The report includes: (1) a list of participants; (2) abstracts of research projects; (3) seminar schedule; (4) evaluation questionnaire; and (5) agenda of visitation by faculty programs committee. Topics discussed include: effects of multiple scattering on laser beam propagation; information management; computer techniques; guidelines for writing user documentation; 30 graphics software; high energy electron and antiproton cosmic rays; high resolution Fourier transform infrared spectrum; average monthly annual zonal and global albedos; laser backscattering from ocean surface; image processing systems; geomorphological mapping; low redshift quasars; application of artificial intelligence to command management systems.

Dah-Nien, F.↗

NASA NTRS1989

The low energy atmospheric antiproton albedo

The flux of albedo antiprotons in the 100-1000 MeV kinetic energy range produced by the cosmic ray primaries in the atmosphere is calculated. It is shown that this is not a significant background to measurements of the low energy anti-proton cosmic ray flux.

Cole, J. B.↗