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At least 343 records · Page 19

Energy spectra and pitch angle distributions of storm-time and substorm injected protons.

Discussion of the energy spectra and pitch angle distributions of ring current protons observed with the solid-state proton detector of Explorer 45 during the main and fast recovery phases of a storm on Dec. 17, 1971. Appearances of characteristic changes in the pitch angle distributions of roughly 100-eV protons are interpreted as pitch angle dispersion of rapidly injected protons during their azimuthal drift at L values above 5.

Konradi, A.↗

Observations of proton spectra /Ep ranging from 1.0 to 300 keV/ and fluxes at the plasmapause.

Discussion of proton flux data recorded for 32 samples per spin period by two solid state proton detectors and a three-axis fluxgate magnetometer aboard Explorer 45 which was launched from Kenia into a 220-km-to-5.24 earth radius orbit. The occurrence of an amplifier saturation effect in the presence of high energy protons is noted. Diagrams are included for proton intensities, proton differential flux vs altitude in six energy bands, evolution of proton differential energy spectra through a steep gradient region, omnidirectional fluxes vs altitude, and plasma densities.

Williams, D. J.↗

Uranus rings - An optical search

The discovery of rings surrounding Uranus has prompted reexamination of telescopic observations made a year ago with a solid-state area detector called a charge-coupling device (CCD). The extreme narrowness of the rings apparently caused them to be hidden in glare from the planet, the reflectivity of which is very high in the blue and green regions of the spectrum. However, Uranus appears as a much darker image in the near-infrared spectral regions detected by the CCD. Although no direct evidence of the rings is obtainable from the CCD images, some simplifying assumptions permit the deduction from the CCD data that average reflectivity of individual particles composing the rings is at most a few percent, much closer to that of carbonaceous chondritic material than to that of the ice-coated particles in Saturn's rings.

Smith, B. A.↗

A dc amplifier for nuclear particle measurement

A monolithic preamplifier-postamplifier combination has been developed for use with solid state particle detectors. The direct coupled amplifiers employ interdigitated n-channel JFET's, diodes, and diffused resistors. The circuits developed demonstrate the feasibility of matching the performance of existing discrete component designs. The fabrication procedures for the monolithic amplifier fabrication are presented and the results of measurements on a limited number of sample amplifiers are given.

Macnee, A. B.↗

The ISEE-C gamma ray burst spectrometer

The technical properties, operation, and expected sensitivity are discussed for an experiment intended to search for narrow lines in the spectra of gamma ray bursts during the ISEE-C mission. At the heart of the experiment is a radiatively cooled germanium solid state photon detector. The instrumentation is capable of storing the entire spectrum of all but the largest bursts in the energy range 0.05-6.5 MeV. In addition, it analyzes the signals from two CsI detectors in two other experiments on the spacecraft and records event time histories from these to a few millisecond accuracy. A background mode permits spectral analysis during quiet times and will allow the determination of physically interesting upper limits for narrow lines in the diffuse gamma ray background radiation.

Teegarden, B. J.↗

The University of Chicago cosmic ray electrons and nuclei experiment on the H spacecraft

The University of Chicago instrument on the Heliocentric spacecraft (MEH experiment) will measure the energy spectrum of cosmic electrons in the range 5-400 MeV. In addition, the energy spectra and relative abundances of nuclei from protons to the iron group, with energies ranging from 30 MeV/n to 15 GeV/n, will be determined. Primary scientific objectives involve the study of the long and short term variability of these components as a probe of the structure of the heliosphere. Particles are identified by multiparameter analysis using the pulse height analyzed signals from eight active detectors - silicon solid state, plastic and crystal scintillators are solid and gas Cerenkov counters. Data return is optimized by a three level priority logic scheme.

Meyer, P.↗

Quiet time observations of equatorially trapped megaelectronvolt radiation belt ions with nuclear charge Z greater than or equal to 4

Data from the equatorial satellite Explorer 45 were used to study ion fluxes during the geomagnetically quiescent period June 1-15, 1972. A heavy-ion solid-state ion detector system obtained count rates close to the equatorial plane in the energy passband 1.82-4.8 MeV per ion during a single satellite pass through the radiation belts. Fluxes of these ions are interpreted as oxygen ions and are found to maximize in the L shell range 3-3.5 with peak equatorially mirroring flux of 0.38 ions/(sq cm s sr keV). This peak is not as sharply confined in L shell as is the helium ion peak.

Spjeldvik, W. N.↗

Development of an earth resource pushbroom scanner utilizing a 90-element 8-14 micrometer /Hg,Cd/Te array

A detailed description is presented of thermal infrared 'pushbroom' scanners being developed for NASA's earth resources survey experiments in the middle to late 1980's. The devices offer high spectral, temporal and spatial resolution, and great reliability as well, due to simplicity of design. Their mode of operation does not require moving optics, since chopping and calibration are integral. The specific device described, a 90-element IR/CCD instrument, was developed to demonstrate scan imagery in the 8-14 micron spectral region in simulated aircraft tests. The scanning operation covers a straight-line path with a linear array of solid-state IR detectors, whose elements are activated sequentially in the cross-track direction while being swept forward along a flight path that, at an aircraft altitude of 10 km, is 7 km wide.

Brown, T. J.↗

High spectral resolution airborne spectrometry

An airborne spectroradiometer system developed at Columbia University has been providing new spectral data for use in remote sensing for natural resources. The system has been improved by addition of a solid state silicon detector array, and has been extended into the infrared by addition of a 64 element lead sulfide detector array. The infrared data in the 2000 to 2500 nm region especially holds large potential for mineral and oil exploration.

Collins, W.↗

A high-resolution study of ultra-heavy cosmic-ray nuclei (A0178)

The main objective of the experiment is a detailed study of the charge spectra of ultraheavy cosmic-ray nuclei from zinc (Z = 30) to uranium (Z = 92) and beyond using solid-state track detectors. Special emphasis will be placed on the relative abundances in the region Z or - 65, which is thought to be dominated by r-process nucleosynthesis. Subsidiary objectives include the study of the cosmic-ray transiron spectrum a search for the postulated long-lived superheavy (SH) nuclei (Z or = 110), such as (110) SH294, in the contemporary cosmic radiation. The motivation behind the search for super-heavy nuclei is based on predicted half-lives that are short compared to the age of the Earth but long compared to the age of cosmic rays. The detection of such nuclei would have far-reaching consequences for nuclear structure theory. The sample of ultraheavy nuclei obtained in this experiment will provide unique opportunities for many tests concerning element nucleosynthesis, cosmic-ray acceleration, and cosmic-ray propagation.

Osullivan, D.↗

Innovative research in the design and operation of large telescopes for space: Aspects of giant telescopes in space

The capability and understanding of how to finish the reflector surfaces needed for large space telescopes is discussed. The technology for making very light glass substrates for mirrors is described. Other areas of development are in wide field imaging design for very fast primaries, in data analysis and retrieval methods for astronomical images, and in methods for making large area closely packed mosaics of solid state array detectors.

Angel, J. R. P.↗

Heavy ion measurement on LDEF

The Kiel Long Duration Exposure Facility (LDEF) experiment M0002, mounted on experiment tray E6, was designed to measure the heavy ion environment by means of CR-39 plastic solid state track detectors. The detector stack with a size of 40x34x4.5 cu cm was exposed in vacuum covered by thermal protection foils with a total thickness of approx. 14 mg/sq cm. After etching small samples of the detector foils tracks with Z greater than or = 6 could be easily detected on a background of small etch pits, which were probably produced by secondaries from proton interactions. The LDEF orientation with respect to the magnetic field lines within the South Atlantic Anomaly (SAA) is expected to be constant during the mission. Therefore, the azimuth angle distribution was measured on the detector foils for low energy stopping particles. All detected arrival directions are close to a plane perpendicular to the magnetic field line of -20 deg declination and -40 deg inclination at location 34 deg W and 27 deg S. Together with the steep energy spectrum, this spatial distribution close to the mirror plane in the SAA is an evidence that heavy ions were detected from a radiation belt population.

Beaujean, R.↗

International Symposium on Space Terahertz Technology, 1st, University of Michigan, Ann Arbor, Mar. 5, 6, 1990, Proceedings

Problems, proposed solutions, and recent results related to the development of solid-state oscillators, detectors, mixers, diode multipliers, and antennas at THz frequencies are addressed. Individual topics considered include: submillimeter heterodyne remote sensing of upper atmospheric gases, planar dipole array antenna with an elliptical lens, twin slot antenna structures integrated with microbolometer detectors for 94-GHz imaging. Also discussed are: quantum-well and quantum-barrier diodes for generating submillimeter wave power, planar Schottky barrier mixer diodes for space applications at submillimeter wavelengths, GaAs Schottky barrier varactor diodes for submillimeter wavelength power generation, planar doped barrier devices for subharmonic mixers.

Ulaby, Fawwaz↗

Space plasma physics at the Applied Physics Laboratory over the past half-century

An overview is given of space-plasma experiments conducted at the Applied Physics Laboratory (APL) at Johns Hopkins University including observational campaigns and the instrumentation developed. Specific space-plasma experiments discussed include the study of the radiation environment in the Van Allen radiation belt with solid-state proton detectors. Also described are the 5E-1 satellites which acquired particle and magnetic-field data from earth orbit. The Triad satellite and its magnetometer system were developed for high-resolution studies of the earth's magnetic field, and APL contributions to NASA's Interplanetary Monitoring Platforms are listed. The review mentions the International Ultraviolet Explorer, the Atmosphere Explorer mission, and the Active Magnetic Particle Tracer Explorers mission. Other recent programs reviewed include a high-latitude satellite, contributions to the Voyager mission, and radar studies of space plasmas.

Potemra, Thomas A.↗

Some results of the oxidation investigation of copper and silver samples flown on LDEF

The Long Duration Exposure Facility (LDEF) Mission provides a unique opportunity to study the long term effects of the space environment on materials. The LDEF has been deployed in orbit on 7 April 1984 by the shuttle Challenger in an almost circular orbit with a mean altitude of 477 km and an inclination of 28.5 degrees. It was retrieved from its decayed orbit of 335 km by the shuttle Columbia on 12 January 1990 after almost 6 years in space. The LDEF is a 12-sided, 4.267 m diameter, and 9.144 m long structure. The experiments, placed on trays, are attached to the twelve sides and the two ends of the spacecraft. The LDEF was passively stabilized with one end of the spacecraft always pointing towards the earth center and one of the sides (row 9) always facing the flight direction. The materials investigated originate from the Ultra-Heavy Cosmic Ray Experiment (UHCRE). The main objective is a detailed study of the charge spectra of ultraheavy cosmic-ray nuclei from zinc to uranium and beyond, using solid-state track detectors. Besides the aluminium alloy used for the experiment, UHCRE comprises several other materials. The results of space exposure for two of them, the copper grounding strips and the thermal covers (FEP Teflon/Ag/Inconel) painted black on the inner side (Chemglaze Z306), are presented.

Derooij, A.↗

Excimer laser processing of backside-illuminated CCDS

An excimer laser is used to activate previously implanted dopants on the backside of a backside-illuminated CCD. The controlled ion implantation of the backside and subsequent thin layer heating and recrystallization by the short wavelength pulsed excimer laser simultaneously activates the dopant and anneals out implant damage. This improves the dark current response, repairs defective pixels and improves spectral response. This process heats a very thin layer of the material to high temperatures on a nanosecond time scale while the bulk of the delicate CCD substrate remains at low temperature. Excimer laser processing backside-illuminated CCD's enables salvage and utilization of otherwise nonfunctional components by bringing their dark current response to within an acceptable range. This process is particularly useful for solid state imaging detectors used in commercial, scientific and government applications requiring a wide spectral response and low light level detection.

Russell, S. D.↗

Study on the biological effect of cosmic radiation and the development of radiation protection technology (L-11)

NASDA is now participating in a series of flight experiments on Spacelab missions. The first experiment was carried out on the first International Microgravity Laboratory Mission (IML-1) January 1992, and the second experiment will be conducted on the Spacelab-J Mission, First Materials Processing Test (FMPT). The equipment or Radiation Monitoring Container Devices (RMCD) includes passive dosimeter systems and biological specimens. The experiments using this hardware are designed by NASDA to measure and investigate the radiation levels inside spacecraft like space shuttle and to look at the basic effects of the space environment from the aspect of radiation biology. The data gathered will be analyzed to understand the details of biological effects as well as the physical nature of space radiation registered in the sensitive Solid-State Track Detectors (SSTD).

Nagaoka, Shunji↗

Measurements of striae in CR+ doped YAG laser crystals

Striations in Czochralski (CZ) grown crystals have been observed in materials such as GaAs, silicon, photorefractive crystals used for data storage, potassium titanyl phosphate crystals and LiNbO3. Several techniques have been used for investigating these defects including electron microscopy, laser scanning tomography, selective photoetching, X-ray diffuse scattering, interference orthoscopy, laser interferometry and micro-Fourier transform infrared spectroscopy mapping. A 2mm thick sample of the material to be investigated is illuminated with light that is absorbed and non-absorbed by the ion concentration to be observed. The back surface of the sample is focused onto a solid-state image detector and images of the input beam and absorbed (and diffracted) beams are captured at two wavelengths. The variation of the coefficient of absorption asa function of distance on the sample can be derived from these measurements. A Big Sky Software Beamcode system is used to capture and display images. Software has been written to convert the Beamcode data files to a format that can be imported into a spreadsheet program such as Quatro Pro. The spreadsheet is then used to manipulate and display data. A model of the intensity map of the striae collected by the imaging system has been proposed and a data analysis procedure derived. From this, the variability of the attenuation coefficient alpha can be generated. Preliminary results show that alpha may vary by a factor of four or five over distances of 100 mu m. Potential errors and problems have been discovered and additional experiments and improvements to the experimental setup are in progress and we must now show that the measurement techniques and data analysis procedures provide 'real' information. Striae are clearly visible at all wavelengths including white light. Their basic spatial frequency does not change radically, at least when changing from blue to green to white light. Further experimental and theoretical work can be done to improve the data collection techniques and to verify the data analysis procedures.

Cady, Fredrick M.↗