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  • Other Sources  (18)
  • 1990-1994  (18)
  • 1993  (11)
  • 1992  (7)
  • 1
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    Mass loading and velocity diffusion models for heavy pickup ions at comet Grigg-Skjellerup (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We compare model predictions of cometary water group ion densities and the solar wind slow down with measurements made by the Giotto Johnstone plasma analyzer implanted ion sensor at the encounter with comet Grigg-Skjellerup (G-S) on July 10, 1992. The observed slope of the ion density profile on approach to the comet is unexpectedly steep. Possible explanations for this are discussed. We present also a preliminary investigation of the quasilinear velocity-space diffusion of the implanted heavy ion population at G-S using a transport equation including souce, convection, adiabatic compression, and velocity diffusion terms. Resulting distributions are anisotropic, in agreement with observations. We consider theoretically the waves that may be generated by the diffusion process for the observed solar wind conditions. At initial ion injections, waves are generated at omega approximately Omega(sub i) the ion gyrofrequency, and lower frequencies are predicted for diffusion toward a bispherical shell.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A12; p. 20,995-21,002
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  • 2
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    Mirror modes and fast magnetoacoustic waves near the magnetic pileup boundary of comet P/Halley (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Large-amplitude ultralow-frequency wave structure observed on both sides of the magnetic pileup boundary of comet P/Halley during the flyby of the Giotto spacecraft have been analyzed using suprathermal electron density and magnetic field observations. Upstream of the boundary, electron density and magnetic field magnitude variations are anticorrelated, while in the pileup region these quantities are clearly correlated. Both in front of and behind the pileup boundary the observed waves are quasi-perpendicular wave structures as a minimum variance analysis shows. A detailed comparison of our observations in the prepileup region with theoretical and numerical results shows that the mirror mode mode waves may have been generated by a mirror instability driven by the pressure anisotropy of the ring-type distributions of the heavy (water group) pickup cometary ions.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A12; p. 20,955-20,964
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  • 3
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    Estimation of crown closure from AVIRIS data using regression analysis (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Crown closure is one of the input parameters used for forest growth and yield modelling. Preliminary work by Staenz et al. indicates that imaging spectrometer data acquired with sensors such as the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) have some potential for estimating crown closure on a stand level. The objectives of this paper are: (1) to establish a relationship between AVIRIS data and the crown closure derived from aerial photography of a forested test site within the Interior Douglas Fir biogeoclimatic zone in British Columbia, Canada; (2) to investigate the impact of atmospheric effects and the forest background on the correlation between AVIRIS data and crown closure estimates; and (3) to improve this relationship using multiple regression analysis.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: JPL, Summaries of the 4th Annual JPL Airborne Geoscience Workshop. Volume 1: AVIRIS Workshop; p 169-172
    Format: application/pdf
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  • 4
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    Fuzzy logic control for camera tracking system (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A concept utilizing fuzzy theory has been developed for a camera tracking system to provide support for proximity operations and traffic management around the Space Station Freedom. Fuzzy sets and fuzzy logic based reasoning are used in a control system which utilizes images from a camera and generates required pan and tilt commands to track and maintain a moving target in the camera's field of view. This control system can be implemented on a fuzzy chip to provide an intelligent sensor for autonomous operations. Capabilities of the control system can be expanded to include approach, handover to other sensors, caution and warning messages.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Fifth Annual Workshop on Space Operations Applications and Research (SOAR 1991), Volume 1; p 94-99
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  • 5
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    Manned mission to Mars with periodic refueling from electrically propelled tankers (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: In a joint study by students from the Ecole Polytechnique Feminine, France, and the University of California, Los Angeles, a mission concept that had the objective of evaluating the feasibility of a non-nuclear, yet fast, manned mission to Mars was considered. Ion-engine propelled tankers are postulated that would provide mid-coarse refueling of LOX and LH2 to the manned ship. The scenario is therefore one of a 'split mission', yet with the added feature that the cargo ships include tankers for mid-course refueling. The present study is a continuation of one first conducted last year. Emphasis this year was on the design of the tanker fleet.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: USRA, Proceedings of the 8th Annual Summer Conference: NASA(USRA Advanced Design Program; p 22-30
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  • 6
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    RAPID: The imaging energetic particle spectrometer on Cluster (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The RAPID spectrometer for the Cluster mission, an advanced particle detector for the analysis of suprathermal plasma distributions in the energy range from 20 to 400 keV and from 2 keV/nuc to 1500 keV for electrons and ions, respectively, is presented. Novel detector concepts in combination with pinhole acceptance permit the measurement of angular distributions over a range of 180 deg in polar angle for either species. The detection principle for the ionic component is based on a two dimensional analysis of a particle's velocity and energy. Electrons are identified by the well known energy range relationship. The detection techniques are described and selected areas in geospace are used to highlight the scientific objectives of this investigation.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: ESA, Cluster: Mission, Payload, and Supporting Activities; p 185-217
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  • 7
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    Fingerprints of carbon, nitrogen, and silicon isotopes in small interstellar SiC grains from the Murchison meteorite (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report ion microprobe determinations of the carbon, nitrogen, and silicon isotopic compositions of small SiC grains from the Murchison CM2 chondrite. Analyses were made on samples containing variable numbers of grains and on 14 individual grains. In some cases the multiple-grain sample compositions were probably dominated by only one or two grains. Total ranges observed are given. Only a few grains show values near the range limits. Both the total ranges of carbon and nitrogen isotopic compositions, and even the narrower ranges typical for the majority of the grains, are similar to those observed for larger SiC grains. Two rare components appear to be present in the smaller-size fraction, one characterized by C-12/C-13 about 12-16 and the other by very heavy nitrogen. The carbon and nitrogen isotopic compositions qualitatively may reflect hydrostatic H-burning via the CNO cycle and He-burning in red giants, as well as explosive H-burning in novae. The silicon isotopic compositions of most grains qualitatively show what is the signature of He-burning. The silicon isotopic composition of one grain, however, suggests a different process.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 57; 16; p. 4059-4068.
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  • 8
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    Effect of spaceflight on the extracellular matrix of skeletal muscle after a crush injury (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The organization and composition of the extracellular matrix were studied in the crush-injured gastrocnemius muscle of rats subjected to 0 G. After 14 days of flight on Cosmos 2044, the gastrocnemius muscle was removed and evaluated by histochemical and immunohistochemical techniques from the five injured flight rodents and various earth-based treatment groups. In general, the repair process was similar in all injured muscle samples with regard to the organization of the extracellular matrix and myofibers. Small and large myofibers were present within an expanded extracellular matrix, indicative of myogenesis and muscle regeneration. In the tail-suspended animals, a more complete repair was observed with nonenlarged area of nonmuscle cells or matrix material visible. In contrast, the muscle samples from the flight animals were less well organized and contained more macrophages and blood vessels in the repair region, indicative of a delayed repair process, but did not demonstrate any chronic inflammation. Myofiber repair did vary in muscles from the different groups, being slowest in the flight animals and most complete in the tail-suspended ones.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: Journal of Applied Physiology, Supplement (ISSN 8750-7587); 73; 2 Au; 74S-81S
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  • 9
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    Laser Raman sensor for measurement of trace-hydrogen gas (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A new optical hydrogen sensor based on spontaneous Raman scattering of laser light has been designed and constructed for rugged field use. It provides good sensitivity, rapid response, and the inherent Raman characteristics of linearity and background gas independence of the signal. Efficient light collection and discrimination by using fast optics and a bandpass interference filter compensate for the inefficiency of the Raman-scattering process. A multipass optical cavity with a Herriott-type configuration provides intense illumination from an air-cooled CW gas laser. The observed performance is in good agreement with the theoretical signal and noise level predictions.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 31; 831-835
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  • 10
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    Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Overview and spectral characteristics (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Large-amplitude electromagnetic plasma waves are one of the dominant features of the solar wind-comet interaction. Wave characteristics strongly depend on parameters such as the solar wind flow and Alfven velocities and the angle between flow and interplanetary magnetic field as well as the production rate. With respect to the latter the flyby of the spacecraft Giotto at comet P/Griff-Skjellerup provides a unique possibility to study such waves in further detail. Pickup ion-related wave signatures have been observed up to a distance of 600,000 km from the nucleus. Peak spectral power in the spacecraft frame of reference occurs at frequencies mainly somewhat below the water group ion gyrofrequency. From this the waves are determined to be mainly left-hand polarized waves, causing one-sided pitch angle diffusion outbound. The wave activity strongly increases close to the comet; upstream it exhibits a quadratic dependence on the water group pickup ion free energy. Furthermore, a phenomenological study of the wave characteristics provides a unique description of the fine-structure of the interaction region. Indications of steepened magnetosonic waves have been found in the outbound magnetosheath region.
    Keywords: ASTRONOMY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A12; p. 20,921-20,935
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