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  • 1
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    Radio properties of type 1.8 and 1.9 Seyfert galaxies (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A number of type 1.8 and 1.9 Seyfert galaxies have been observed at the VLA in order to compare their properties with those of the other types of Seyfert galaxy. The observed types have radio luminosities in the range of 10 to the 39th-40.5th args/s, with the median near 10 to the 40th ergs/s. Most of these galaxies have radio sources with diameters of about 500 pc or less. The ratio of radio luminosity to featureless optical continuum luminosity in the Seyfert 1.8/12.9 galaxies and Seyfert 1.2/1.5 galaxies is intermediate between the values for Seyfert 1 and Seyfert 2 galaxies. The infrared-to-radio ratio decreases along the sequence from Seyfert 1 galaxies, through intermediate Seyfert galaxies, to Seyfert 2 galaxies. This systematic statistical difference in the ratio of two aspect-independent quantities implies that the differences among the Seyfert classes cannot be attributed solely to differences in viewing angle.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 310; 136-144
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  • 2
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    Radio properties of the highly polarized, quiescent quasar OI 287 (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The highly polarized, quiescent quasar OI 287 has been observed with high resolution at 2 cm and 6 cm in an effort to determine the origin of some of the object's peculiar properties. The results seem to rule out the classification of OI 287 as a blazar. Extrapolation of the radio core spectrum to midinfrared wavelengths fails to predict the infrared flux by at least an order of magnitude. This supports the conclusion that the infrared emission and the radio emission do not originate in the same synchrotron-emitting component. The high optical polarization could be related to possible broad absorption lines in the unobserved UV regime, or it could be caused by reflection into the line of sight by scattering agents distributed in a thin disk.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 328; 569-577
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  • 3
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    Strategies for high-precision Global Positioning System orbit determination (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Various strategies for the high-precision orbit determination of the GPS satellites are explored using data from the 1985 GPS field test. Several refinements to the orbit determination strategies were found to be crucial for achieving high levels of repeatability and accuracy. These include the fine tuning of the GPS solar radiation coefficients and the ground station zenith tropospheric delays. Multiday arcs of 3-6 days provided better orbits and baselines than the 8-hr arcs from single-day passes. Highest-quality orbits and baselines were obtained with combined carrier phase and pseudorange solutions.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 12751-12
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  • 4
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    Space Station propulsion system technology (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Two propulsion systems have been selected for the Space Station: O/H rockets for high thrust applications and the multipropellant resistojets for low thrust needs. These thruster systems integrate very well with the fluid systems on the station. Both thrusters will utilize waste fluids as their source of propellant. The O/H rocket will be fueled by electrolyzed water and the resistojets will use stored waste gases from the environmental control system and the various laboratories. This paper presents the results of experimental efforts with O/H and resistojet thrusters to determine their performance and life capability.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Acta Astronautica (ISSN 0094-5765); 15; 673-683
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  • 5
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    Electromagnetic emission experiences using electric propulsion systems (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 5; 534-547
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  • 6
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    Performance characterizations of an engineering model multipropellant resistojet (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 5; 197-203
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  • 7
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    Precise orbit determination of a geosynchronous satellite with differential very-long-baseline interferometry (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The use of differential VLBI (DVLBI) to determine the orbit of a U.S. geosynchronous satellite with a position accuracy of a few meters is examined. DVLBI was employed to track the geosynchronous satellite DSCS-II; two observation channels with 2 MHz bandwidth each in a 2 GHz band were used to receive the telemetry signal of the satellite and quasar radio signals. The random observation, delay, station location, and quasar position errors are discussed. The correlation processing of the quasar and satellite signals is described. The accuracy of the estimated satellite position is evaluated using a covariance analysis. It is determined that the satellite position was estimated with an accuracy of about 4 m at the center of the observation arc. It is noted that the modeling error of the solar radiation pressure factor, ionospheric correction error, and observation error need to be corrected in order to provide more accurate orbit determinations.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
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  • 8
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    A large family of compact radio sources in the starburst nucleus of NGC 253 (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Deep VLA maps of NGC 253 show that it has at least 35 compact radio sources similar to those in the prototypical IR starburst galaxy M82. It is noted that NGC 253 is a twin of M82 in IR spectrum and luminosity as well as distance. Some of the sources in M82 which are rapidly expanding and fading are believed to be extremely young supernova remnants. Most of the sources detected in NGC 253 are unresolved or only marginally resolved, with typical diameters no greater than 2-5 pc. If they are young supernova remnants expanding at 12,000 km/s, the source ages are no more than 160-400 yr. This requires a supernova rate of about 1/0.1 yr. If the compact radio sources are indeed young supernova remnants, star formation must have ceased shortly after the progenitors of the current supernovae were produced.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 330; L97-L100
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  • 9
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    Signal chain for the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The AVIRIS instrument has a separate dedicated analog signal processing chain for each of its four spectrometers. The signal chains amplify low-level focal-plane line array signals (5 to 10 mV full-scale span) in the presence of larger multiplexing signals (approx 150 mV) providing the data handling system a ten-bit digital word (for each spectrometer) each 1.3 microns. This signal chain provides automatic correction for the line array dark signal nonuniformity (which can approach the full-scale signal span).
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). A Description of the Sensor, Ground Data Processing Facility, Laboratory Calibration, and First Results; Airborne Visible(Inf
    Format: application/pdf
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  • 10
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    Effect of water on the composition of partial melts of greenstone and amphibolite (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Closed-system partial melts of hydrated, metamorphosed arc basalts and andesites (greenstones and amphibolites), where only water structurally bound in metamorphic minerals is available for melting (dehydration melting), are generally water-undersaturated, coexist with plagioclase-rich, anhydrous restites, and have compositions like island arc tonalites. In contrast, water-saturated melting at water pressures of 3 kilobars yields strongly peraluminous, low iron melts that coexist with an amphibole-bearing, plagioclase-poor restite. These melt compositions are unlike those of most natural silicic rocks. Thus, dehydration melting over a range of pressures in the crust of island arcs is a plausible mechanism for the petrogenesis of islands arc tonalite, whereas water-saturated melting at pressure of 3 kilobars and above is not.
    Keywords: GEOPHYSICS
    Type: Science (ISSN 0036-8075); 244; 195-197
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