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  • SPACE SCIENCES  (277)
  • INSTRUMENTATION AND PHOTOGRAPHY  (129)
  • ASTRONOMY  (107)
  • 1
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    Centaurus A, the core of the problem (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: The bright, peculiar elliptical galaxy Centaurus A (NGC 5128, PKS 1322-427) was one of the first extragalactic radio sources to be optically identified (Bolton et al. 1949). At a distance of 4 Mpc, Centaurus A is the closest active radio galaxy and affords the highest linear imaging resolution (1 mas approximately equal to 0.02 pc) and hence the best prospects for studying an active nucleus close to the central radio source. We present the results of multi-epoch, 8.4-GHz, very long baseline interferometry (VLBI), imaging observations of the nucleus made over the past three years. The nucleus possesses a core-jet structure where the inner portion of the jet shows apparent linear motion with a velocity substantially less than the speed of light.
    Keywords: ASTRONOMY
    Type: Australian Journal of Physics (ISSN 0004-9506); 47; 5; p. 619-624
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  • 2
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    Readout electrode assembly for measuring biological impedance (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The invention comprises of a pair of readout ring electrodes which are used in conjunction with apparatus for measuring the electrical impedance between different points in the body of a living animal to determine the amount of blood flow therebetween. The readout electrodes have independently adjustable diameters to permit attachment around different parts of the body between which it is desired to measure electric impedance. The axial spacing between the electrodes is adjusted by a pair of rods which have a first pair of ends fixedly attached to one electrode and a second pair of ends slidably attached to the other electrode. Indicia are provided on the outer surface of the ring electrodes and on the surface of the rods to permit measurement of the circumference and spacing between the ring electrodes.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Format: application/pdf
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  • 3
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    Impact of Thematic Mapper Sensor Characteristics on Classification Accuracy (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: A three factor (spectral, spatial, and radiometric resolution), two level (TM and MSS) analysis of variance (ANOVA) approach allowed evaluation of the effects of each factor individually and in all possible combinations. Digital classification accuracy was used as the figure of merit. Nine study sites in Washington, D.C. each of approximately 256 x 256 TM pixels, were randomly selected from the full scene for analysis. These results strongly suggest that the quantization level improvements and the addition of new spectral bands in the visible and middle IR regions (both afforded by the TM sensor design) can result in improved capabilities to accurately delineate land cover categories using a per point Gaussian maximum likelihood classifier. On the other hand, results indicate that the increase in spatial resolution to 30m does not significantly enhance classification accuracy. The spatial result points to an inherent limitation of a per point classifier and to the need to improve data analysis techniques to handle high spatial resolution data.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: LANDSAT-4 Sci. Invest. Summ., Including Dec. 1983 Workshop Results, Vol. 2; p 93-97
    Format: text
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  • 4
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    The southern hemisphere VLBI experiment (SHEVE) (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Six radio telescopes were operated as the first southern hemisphere VLBI array in April and May 1982. Observations were made at 2.3 and 8.4 Ghz. This array produced VLBI images of 28 southern hemisphere radio sources, high accuracy VLBI geodesy between southern hemisphere sites, and sub-arcsecond radio astrometry of celestial sources south of declination -45 degrees. This paper discusses only the astrophysical aspects of the experiment.
    Keywords: ASTRONOMY
    Type: IAU Symposium on the Impace of VLBI on Astrophysics and Geophysics; May 10, 1987 - May 15, 1987; Cambridge, MA; United States
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  • 5
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    Radio observations of SN 1987A (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The study of radio emission from SN 1987A after the neutrino burst is reviewed. The observed maximum flux density of the burst at radio wavelengths was about 140 mJy and occurred at 1.4 GHz. The radio light curves for SN 1987A at four frequencies are compared with data for SN 1979C and SN 1980K. VLBI observations of SN 1987A at 2.3 GHz and other radio monitoring programs are examined.
    Keywords: ASTRONOMY
    Type: Geroge Mason Astrophysics Workshop; Oct 12, 1987 - Oct 14, 1987; Fairfax, VA; United States
    Format: text
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  • 6
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    The unusual morphology of molecular hydrogen emission in the planetary nebula J900 (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We report new high-resolution near-infrared imaging observations of the planetary nebula J900, in broadband J, H, and K, and narrowband 2.122 micrometers (for H2 1-0 S(1)), Brackett-gamma, and continuum filters. The H2 images reveal a remarkable set of outward-extending features not detected in any previous observations of theis object. In the northwest lobe of the inner bipolar region, the H2 emission, Brackett-gamma emission, and underlying continuum are spatially resolved. The relative positions of the peaks of the line emission suggest an ionization front seen edge-on. The continuum emission, apparently located nearer to the central star, is likely due to transiently heated small dust grains. The extended H2 emission features are probably excited either by oblique shocks caused by material ejected from the nebula, or by radiation leaking from holes in the opacity surrounding the ionized shell.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 109; 3; p. 1173-1180
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  • 7
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    Particle impact and optical property analysis of the surfaces of Surveyor 3 materials (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: As part of the investigation of Surveyor 3 materials, a study was conducted to determine the effect of the lunar environment on some of the painted and unpainted exterior surfaces. Examination of the camera parts and tube sections was conducted using three techniques: (1) optical and scanning electron microscopy, (2) energy dispersive X-ray probe analysis, and (3) spectral reflectance measurements.
    Keywords: SPACE SCIENCES
    Type: Analysis of Surveyor 3 Mater. and Phot. Returned by Apollo 12; p 76-88
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  • 8
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    Surface properties working group (1973)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: The objectives of the Mars surface properties working group are described. The objectives were: (1) determine a simple reference surface that would adequately represent the shape of the planet for cartographic purposes; (2) monitor the topographic results and to assess the relative calibration and accuracies of these techniques, thereby leading to a composite topographic map of the planet; and (3) facilitate the exchange of data in closely connected disciplines. The shape, topography, and isobaric surface are discussed along with the gravity field, and crustal density model. It was found that there is no simple reference figure for the planetary surface, although an offset, triaxial ellipsoid is adequate for most purposes.
    Keywords: SPACE SCIENCES
    Type: Mariner Mars 1971 Proj., Vol. 5; p 81-85
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  • 9
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    Anchoring spacecraft to planets (1971)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: For planet tracking, the immense mass relative to applied nongravitational forces (for even the smaller asteroids) removes limitations on the ability to model orbital motion mathematically. A lander on a natural satellite (other than the moon) would not suffer from nongravitational effects, and would further have a large mean motion, which is important for observing gravitational effects. The tracking of a Mars lander over a long period would yield conclusions in the areas of relativity (determination of the parameter beta), the inertial framework, Mars' internal structure (based on the polar moment), and Mars' physical ephemeris.
    Keywords: SPACE SCIENCES
    Type: Proc. of the Conf. on Exptl. Tests of Gravitation Theories; p 244-248
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  • 10
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    Preliminary report on the geology of the Plato quadrangle of the moon (1966)
    In:  CASI
    Details
    Publication Date: 2006-10-26
    Description: Morphological rock units, structure, and geologic history of Plato quadrangle
    Keywords: SPACE SCIENCES
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