Engineering topics

Adams, James H., Jr.

Publications and source records attributed to Adams, James H., Jr..

45 records · Page 3

NASA NTRS1993

Progress report on the Heavy Ions in Space (HIIS) experiment

One of the objectives of the Heavy Ions In Space (HIIS) experiment is to investigate heavy ions which appear at Long Duration Exposure Facility (LDEF) below the geomagnetic cutoff for fully-ionized galactic cosmic rays. Possible sources of such 'below-cutoff' particles are partially-ionized solar energetic particles, the anomalous component of cosmic rays, and magnetospherically-trapped particles. In recent years, there have also been reports of below-cutoff ions which do not appear to be from any known source. Although most of these observations are based on only a handful of ions, they have led to speculation about 'partially-ionized galactic cosmic rays' and 'near-by cosmic ray sources'. The collecting power of HIIS is order of magnitude larger than that of the instruments which reported these results, so HIIS should be able to confirm these observations and perhaps discover the source of these particles. Preliminary results on below-cutoff heavy-ions are reported. Observations to possible known sources of such ions are compared. A second objective of the HIIS experiment is to measure the elemental composition of ultraheavy galactic cosmic rays, beginning in the tin-barium region of the periodic table. A report on the status of this analysis is presented.

Adams, James H., Jr.↗

NASA NTRS1993

Future radiation measurements in low Earth orbit

The first Long Duration Exposure Facility (LDEF) mission has demonstrated the value of the LDEF concept for deep surveys of the space radiation environment. The kinds of measurements that could be done on a second LDEF mission are discussed. Ideas are discussed for experiments which: (1) capitalize on the discoveries from LDEF 1; (2) take advantage of LDEF's unique capabilities; and (3) extend the investigations begun on LDEF 1. These ideas have been gleaned from investigators on LDEF 1 and others interested in the space radiation environment. They include new approaches to the investigation of Be-7 that was discovered on LDEF 1, concepts to obtain further information on the ionic charge state of cosmic rays and other energetic particles in space and other ideas to extend the investigations begun on LDEF 1.

Adams, James H., Jr.↗

NASA NTRS1992

Heavy Ions In Space (HIIS) experiment

The Heavy Ions In Space (HIIS) experiment has two primary objectives: (1) to measure the elemental composition of ultraheavy Galactic cosmic rays, beginning in the tin-barium region of the periodic table; and (2) to study heavy ions which arrive at LDEF below the geomagnetic cutoff, either because they are not fully stripped of electrons or because their source is within the magnetosphere. Both have practical as well as astrophysical consequences. The HIIS experiment used eight thick stacks of plastic track detectors mounted in two trays on the space facing end of LDEF. Since the last LDEF symposium, the statistics were increased of the observations and have extended the analysis to a second stack and to detector sheets near the top of a stack. New results are reported on the detector resolution and on the observations of both stopping and relativistic particles.

Adams, James H., Jr.↗

NASA NTRS1992

Future radiation measurements in low Earth orbit

The first Long Duration Exposure Facility (LDEF) mission has demonstrated the value of the LDEF concept for deep surveys of the space radiation environment. This paper will survey the types of measurements that could be done on a second LDEF mission. One of the most surprising discoveries on LDEF1 was the Be-7 that was found imbedded on the windward surface. LDEF2 could follow up on this discovery and search for evidence of other cosmogenic nuclei. Another experiment could be designed to investigate the presence of energetic heavy ions observed on LDEF1. The relative abundance of rare earths can also be used to search for evidence that cosmic rays accelerate in episodes which occur throughout their propagation in the stellar medium. Further investigations of radiation effects could also be undertaken. A second LDEF mission also offers the opportunity for new investigations such as measurements of cosmic ray differential energy spectrum to ultrahigh energies. These and other ideas will be discussed.

Adams, James H., Jr.↗

NASA NTRS1992

Preliminary results from the heavy ions in space experiment

The Heavy Ions In Space (HIIS) experiment has two primary objectives: (1) to measure the elemental composition of ultraheavy galactic cosmic rays, beginning in the tin-barium region of the periodic table; and (2) to study heavy ions which arrive at LDEF below the geomagnetic cutoff, either because they are not fully stripped of electrons or because their source is within the magnetosphere. Both of these objectives have practical as well as astrophysical consequences. In particular, the high atomic number of the ultraheavy galactic cosmic rays puts them among the most intensely ionizing particles in Nature. They are therefore capable of upsetting electronic components normally considered immune to such effects. The below cutoff heavy ions are intensely ionizing because of their low velocity. They can be a significant source of microelectronic anomalies in low inclination orbits, where Earth's magnetic field protects satellites from most particles from interplanetary space. The HIIS results will lead to significantly improved estimates of the intensely ionizing radiation environment.

Adams, James H., Jr.↗

NASA NTRS1990

Astrogam - A magnetic rigidity spectrometer for gamma-ray astronomy

A novel concept is presented for a high-energy gamma-ray telescope with an extended energy range and excellent energy and angular resolution. The characteristics of Astrogam, a wide-field camera which makes an all-sky survey, are enumerated. Consideration is given to the instrument's unique features: wide energy range (four orders of magnitude and energy, which will bridge the gap between satellite and ground-based observations); excellent source location precision (multiple scattering error dominating nuclear recoil and measurement error below 20 GeV); and excellent energy resolution (1-percent energy resolution). Astrogam will make observations in the GTE energy range possible and could resolve complex source regions like the Crab pulsar/Nebular system, the Galactic center, and the Geminga region as well as discover the true nature of the sources.

Adams, James H., Jr.↗

NASA NTRS1988

Toward a descriptive model of solar particles in the heliosphere

During a workshop on the interplanetary charged particle environment held in 1987, a descriptive model of solar particles in the heliosphere was assembled. This model includes the fluence, composition, energy spectra, and spatial and temporal variations of solar particles both within and beyong 1 AU. The ability to predict solar particle fluences was also discussed. Suggestions for specific studies designed to improve the basic model were also made.

Shea, M. A.↗

NASA NTRS1988

Toward a descriptive model of galactic cosmic rays in the heliosphere

Researchers review the elements that enter into phenomenological models of the composition, energy spectra, and the spatial and temporal variations of galactic cosmic rays, including the so-called anomalous cosmic ray component. Starting from an existing model, designed to describe the behavior of cosmic rays in the near-Earth environment, researchers suggest possible updates and improvements to this model, and then propose a quantitative approach for extending such a model into other regions of the heliosphere.

Mewaldt, R. A.↗

NASA NTRS1988

Current models of the intensely ionizing particle environment in space

The Cosmic Ray Effects on MicroElectronics (CREME) model that is currently in use to estimate single event effect rates in spacecraft is described. The CREME model provides a description of the radiation environment in interplanetary space near the orbit of the earth that contains no major deficiencies. The accuracy of the galactic cosmic ray model is limited by the uncertainties in solar modulation. The model for solar energetic particles could be improved by making use of all the data that has been collected on solar energetic particle events. There remain major uncertainties about the environment within the earth's magnetosphere, because of the uncertainties over the charge states of the heavy ions in the anomalous component and solar flares, and because of trapped heavy ions. The present CREME model is valid only at 1 AU, but it could be extended to other parts of the heliosphere. There is considerable data on the radiation environment from 0.2 to 35 AU in the ecliptic plane. This data could be used to extend the CREME model.

Adams, James H., Jr.↗