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Results for “COSMIC RAY ALBEDO”

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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Energetic neutrons leaking from the top of the atmosphere.

The energy, angular, and latitude distributions of energetic neutrons (up to 2 GeV) leaking from the top of the atmosphere have been calculated. The results agree with the recent measurement of Preszler, Simnett, and White, whose leakage rates were well above the calculation of Lingenfelter. Since the spectrum of Lingenfelter has served for evaluating the cosmic-ray albedo-neutron decay (CRAND) source of energetic protons in Earth's inner radiation belt, it is suggested that the results reported here be used to reevaluate the CRAND contribution.

Merker, M.↗
NASA NTRS1974

Optical properties of the Apollo 15 deep core samples

The variations of albedo observed at different depths in a core tube show almost as large a range as occurs on the surface over the entire moon. Different regions in the core tube are very sharply separated from each other, demonstrating that little mixing had taken place in the deposition process or subsequently. A possible correlation between albedo and cosmic ray exposure is noted.

Gold, T.↗
NASA NTRS1975

Calculated angular distributions of energetic atmospheric neutrons

Calculated angular distributions of atmospheric leakage neutron fluxes from 19 MeV to 1 GeV are presented. Comparisons with the balloon measurements of Preszler et al. and Kanbach et al. are made and show substantial agreement, strengthening the belief in the importance of the CRAND (cosmic-ray albedo-neutron decay) contribution to the high-energy protons in the earth's inner radiation belt. The calculation is presented as a means for investigating features of atmospheric flux distributions.

Merker, M.↗
NASA NTRS1980

Sources and sinks of energetic electrons and protons in Saturn's magnetosphere

The paper deals with some results of continuing analysis and interpretation of energetic particle observations made onboard Pioneer 11 during its August-September 1979 encounter with Saturn. Source strength estimates and the radial dependence of the phase space density of protons of energies above 80 MeV indicate with some confidence that the cosmic-ray neutron albedo from the planets atmosphere and rings is the source of these particles.

Van Allen, J. A.↗
NASA NTRS1982

Two-component proton spectra in the inner Saturnian magnetosphere

Measurements obtained by the Pioneer-11 spacecraft in Saturn's inner magnetosphere revealed the presence of a high energy proton component, primarily confined within the orbits of satellites Enceladus and Mimas. The high energy component was interpreted as due to protons from cosmic ray neutron albedo decay interactions with the Saturnian rings and, secondarily, the planetary atmosphere, but without detailed knowledge of the differential or integral spectrum. The main objective of the present investigation is to examine in some detail the ion spectra in the considered region of the magnetosphere, and to provide some of the basic input necessary in evaluating various models of energetic particle-ring interactions. The conducted measurements clearly show the presence of low energy ions and electrons inside the orbit of Mimas and provide a measure of the evolution of the hot ion spectrum observed inside the orbit of Rhea into a two-component power law spectrum inside the orbits of Enceladus and Mimas.

Krimigis, S. M.↗
NASA NTRS1991

The ionizing radiation environment of LDEF prerecovery predictions

The Long Duration Exposure Facility (LDEF) was exposed to several sources of ionizing radiation while in orbit. The principal ones were trapped belt protons and electrons, galactic cosmic rays, and albedo particles (protons and neutrons) from the atmosphere. Large solar flares in 1989 may have caused a small contribution. Prior to the recovery of the spacecraft, a number of calculations and estimates were made to predict the radiation exposure of the spacecraft and experiments. These were made to assess whether measurable radiation effects might exist, and to plan the analysis of the large number of radiation measurements available on the LDEF. Calculations and estimates of total dose, particle fluences, linear energy transfer spectra, and induced radioactivity were made. The principal sources of radiation is described, and the preflight predictions are summarized.

Watts, John W., Jr.↗
NASA NTRS2000

Natural Hazards of the Space Environment

Spacecraft in Low Earth Orbit (LEO) are subject to numerous environmental hazards. Here I'll briefly discuss three environment factors that pose acute threats to the survival of spacecraft systems and crew: atmospheric drag, impacts by meteoroids and orbital debris, and ionizing radiation. Atmospheric drag continuously opposes the orbital motion of a satellite, causing the orbit to decay. This decay will lead to reentry if not countered by reboost maneuvers. Orbital debris is a by-product of man's activities in space, and consists of objects ranging in size from miniscule paint chips to spent rocket stages and dead satellites. Ionizing radiation experienced in LEO has several components: geomagnetically trapped protons and electrons (Van Allen belts); energetic solar particles; galactic cosmic rays; and albedo neutrons. These particles can have several types of prompt harmful effects on equipment and crew, from single-event upsets, latchup, and burnout of electronics, to lethal doses to crew.All three types of prompt threat show some dependence on the solar activity cycle. Atmospheric drag mitigation and large debris avoidance require propulsive maneuvers. M/OD and ionizing radiation require some form of shielding for crew and sensitive equipment. Limiting exposure time is a mitigation technique for ionizing radiation and meteor streams.

Evans, Steven W.↗
NASA NTRS2006

Radiation Dose from Lunar Neutron Albedo

The lunar neutron albedo from thermal energies to 8 MeV was measured on the Lunar Prospector Mission in 1998-1999. Using GEANT4 we have calculated the neutron albedo due to cosmic ray bombardment of the moon and found a good-agreement with the measured fast neutron spectra. We then calculated the total effective dose from neutron albedo of all energies, and made comparisons with the effective dose contributions from both galactic cosmic rays and solar particle events to be expected on the lunar surface.

Adams, J. H., Jr.↗
NASA NTRS2003

Lunar Regolith Albedos Using Monte Carlos

The analysis of planetary regoliths for their backscatter albedos produced by cosmic rays (CRs) is important for space exploration and its potential contributions to science investigations in fundamental physics and astrophysics. Albedos affect all such experiments and the personnel that operate them. Groups have analyzed the production rates of various particles and elemental species by planetary surfaces when bombarded with Galactic CR fluxes, both theoretically and by means of various transport codes, some of which have emphasized neutrons. Here we report on the preliminary results of our current Monte Carlo investigation into the production of charged particles, neutrons, and neutrinos by the lunar surface using FLUKA. In contrast to previous work, the effects of charm are now included.

Wilson, T. L.↗
NASA NTRS1972

Solar cosmic ray, solar wind, solar flare, and neutron albedo measurements, part C

All mineral detectors exposed on Apollo 16 had high surface track densities probably produced by a solar flare that occurred during the mission. The heavy ions followed a power law spectrum with exponent approximately 3 down to approximately 200 KeV/nucleon. The abundance of low-energy particle tracks observed in this flare may explain the high track densities observed in lunar dust grains. Pristine heavy-particle tracks in feldspar give long tracks. Shallow pits similar to those expected from extremely heavy solar wind ions were observed in about the expected number. Initial results give a low apparent value of neutron albedo relative to theory.

Burnett, D.↗
NASA NTRS1984

Production of high-energy gamma rays by cosmic ray interactions in the atmosphere and lunar surface

The production of gamma rays above 10 MeV by the interaction of cosmic rays in the atmosphere and the lunar surface is simulated using Monte Carlo methods. The calculation incorporates a new model of high-energy nucleon-nucleus interactions based on empirical fits to inclusive cross sections for the production of pions and nucleons. The atmospheric gamma ray flux is calculated as a function of direction, energy, and atmospheric depth. These calculations are compared with observations from balloons and from the SAS 2 satellite. Estimates of the flux of earth albedo electrons produced by cosmic ray interactions are presented. The lunar gamma ray albedo is calculated and compared with an upper limit based on SAS 2 measurements.

Morris, D. J.↗
NASA NTRS2015

Signatures of Volatiles in the Lunar Proton Albedo

We find evidence for hydrated material in the lunar regolith using "albedo protons" measured with the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and are inconsistent with the latitude trends of heavy element enrichment (e.g., enhanced Fe abundance). The latitudinal distribution of albedo protons anti-correlates with that of epithermal or high energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in hydrated regolith that is more prevalent near the poles. The CRaTER instrument may thus provide important measurements of volatile distributions within regolith at the Moon and potentially, with similar sensors and observations, at other bodies within the Solar System.

surface↗
NASA NTRS1975

Splash albedo protons between 4 and 315 MeV at high and low geomagnetic latitudes

Results are reported for measurements of the differential energy spectrum of splash-albedo protons at high geomagnetic latitude during three periods of the last solar cycle as well as at low latitude during one of those periods. The measurements were made with a balloon-borne solid-state detector telescope. Splash-albedo protons with energies between 4 and 315 MeV were observed in fluxes of approximately 81, 70, and 48 protons/sq m per sec per sr at high latitude and in fluxes of approximately 37 protons/sq m per sec per sr at low latitude. It is shown that the difference between the first and third high-latitude measurements was due to solar modulation of the cosmic-ray parent nuclei. The albedo spectrum is found to have a similar shape for both latitudes, and it is suggested that the difference in intensity can be explained by different local geomagnetic cutoffs.

Wenzel, K.-P.↗
NASA NTRS1982

Studies of neutron and proton nuclear activation in low-Earth orbit

The expected induced radioactivity of experimental material in low Earth orbit was studied for characteristics of activating particles such as cosmic rays, high energy Earth albedo neutrons, trapped protons, and secondary protons and neutrons. The activation cross sections for the production of long lived radioisotopes and other existing nuclear data appropriate to the study of these reactions were compiled. Computer codes which are required to calculate the expected activation of orbited materials were developed. The decreased computer code used to predict the activation of trapped protons of materials placed in the expected orbits of LDEF and Spacelab II. Techniques for unfolding the fluxes of activating particles from the measured activation of orbited materials are examined.

Laird, C. E.↗
NASA NTRS2004

Helium Production of Prompt Neutrinos on the Moon

The subject of conducting fundamental physics and astronomy experiments on the lunar surface continues to be of interest in the planetary science community. Such an inquiry necessarily requires an analysis of the backscatter albedos produced by Galactic cosmic rays (GCRs) when they directly impact the lunar regolith. Unlike the Earth, this happens because the Moon has only a tenuous exosphere. Such secondary radiation constitutes a background that obscures and interferes with measurements conducted in the normal sense of laboratory physics on Earth. Our previous investigations using recent enhancements in the Monte Carlo program known as FLUKA included the production of charged particles, neutrons, photons, and neutrinos by the impact of Galactic protons. That investigation is extended here to include the effect of ionized helium, He-4, or a particles. Because high-energy GCRs excite planetary regoliths into giving rise to charmed mesons, neutrinos are produced. Thus a connection is established for the GCR helium production of prompt neutrinos on the Moon using the physics of charm.

Andersen, V.↗
NASA NTRS1991

Charged-particle induced alterations of surfaces in the outer solar system

Researchers calculated the plasma bombardment profiles of the surfaces of the icy Saturnian satellites in order to interpret reflection spectra and the effect of charged particles on the surfaces (mantles) of Pluto and of comets in the Oort cloud. Pluto's exposure to cosmic rays results in a slow alteration of the reflectance if the methane condensed on its surface. The UV absorbed in the atmosphere can produce precipitates. The researchers showed that, depending on the rates of the competing regolith processes and rates for replenishment of the methane, the surface can appear bright, red, or dark. Using laboratory data, they showed that the amount of darkening occurring in one orbit is small. Therefore, transport, burial, and re-exposure of organic sediments must control the reflectance, and the average reflectance is established by the radiation altered species accumulated over many orbits with the observed spatial, and possible temporal, differences in albedo due to transport. The cosmic rays, although producing changes in reflectance slowly, do so inevitably. Therefore, the fact that the surface is not dark everywhere implies that it is active and the exposure rates vs. depth into the surface of Pluto can be used to constrain turnover rates. Comets in the Oort cloud experience similar rates.

Johnson, R. E.↗