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  • 1
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    Major outburst of periodic Comet Halley at a heliocentric distance of 14 AU (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The properties and evolution of the major outburst experienced by Comet Halley at 14 AU during February-March 1991 are studied. It is found that the observed halo is a segment of a conical surface populated by solid particles ejected from a localized, temporarily activated region on the sunlit hemisphere of the spinning nucleus. The total mass of the ejecta was at least 10 exp 12 g and CO was probably the prime driver, accelerating the smallest grains to a terminal velocity of about 45 m/s. The mass loading of the gas flow by particulate matter is enormous, with the mass production rate exceeding the expected production rate of CO by a factor of several tens.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 263; 1-2; p. 367-386.
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  • 2
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    Observations of comet Ikeya-Seki /1965 f/ from Tucson, Arizona (1966)
    In:  CASI
    Details
    Publication Date: 2006-10-26
    Description: Visual and photographic observations of comet Ikeya-Seki, pre-perihelion and post-perihelion, from Arizona, 1965f
    Keywords: SPACE SCIENCES
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  • 3
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    International Halley Watch: Discipline specialists for near-nucleus studies (1986)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The purpose of the Near-Nucleus Studies Net is to study the processes taking place in the near-nucleus environment as they relate to the nature of nucleus. This is accomplisghed by measuring the spatial and temporal distribution of dust, gases and ions in the coma on high resolution images taken from many observatories around the world. By modeling the motions of discrete dust features in Comet Halley, it is often possible to determine the locations of the emission sources on the surface and learn about the nucleus structure. In addition to the general goals shared by all IHW nets, the scientific goals of the net has been to determine (1)the gross surface structure of the nucleus, (2)the nucleus spin vector, (3)the distribution and evolution of jet sources and (4)the interrelationships between the gas, dust and ion components of the coma. An additional Comet Giacobini-Zinner watch was carried out by the NNSN in support of the NASA International Cometary Explorer flyby.
    Keywords: ASTRONOMY
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 181-182
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  • 4
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    Cometary spectroscopy (1986)
    In:  CASI
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    Publication Date: 2006-02-14
    Description: The spectroscopic and morphological characteristics of comets over a wide range of heliocentric distances are investigated as they may suggest or constrain models of cometary formation environments and evolution. This program also contributes to the understanding of the general comet population with which spacecraft data will be compared. Long slit spectra and direct images of all observable comets (M2〈18) are obtained on a monthly basis with either a UV sensitive microchannel plate or a red sensitive CCD spectrograph/camera. Scale lengths of the principal emission of OH, NH, CN, C3, C2, NH2 and OI different comets can be compared. The direct images are used for studies of dust anisotropy which can provide data on the spin vector and gross surface morphology.
    Keywords: ASTRONOMY
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 100-101
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  • 5
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    The modern role of visual observations of comets (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: This paper reviews the role of past and future visual observations in cometary research. The strengths and limitations of visual observations are explored for the benefit of both investigators who might have to use them and observers who wish to make real contributions to the field. We consider the characteristics of the eye-brain combination as a detector and compare them with those of modern detectors. We specifically evaluate visual discoveries, magnitude estimates, and drawings.
    Keywords: ASTRONOMY
    Type: In: Comets in the post-Halley era. Vol. 1 (A93-13551 02-90); p. 209-223.
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  • 6
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    Thermal-infrared and visual imaging of comet Giacobini-Zinner (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Thermal-infrared and visual images obtained simultaneously of comet Giacobini-Zinner on UT 1985 August 4.4 are presented. The 10.8-micron map, which spans several arc minutes with 8-arcsec resolution, is the first ground-based infrared image of a comet. Considerable spatial structure is evident in the map, including a curved dust tail consisting primarily of dust grains larger than 100 microns. The width of this large-grain tail implies that these grains depart the nucleus with velocities less than 3 m/s. The distribution of grain albedo is determined for the central 1 arcmin. It is speculated that an observed increase in the albedo by a factor of 2 with distance from the nucleus and prolonged radius vector results from the confinement to the orbital plane of large fluffy grains previously considered for GZ by others; the lower albedo of this dust could result from multiple internal scattering increasing the probability of absorption of incident light. It is estimated that dust was departing the nucleus at the rate of about 8 x 10 to the 5th g/s, comparable to that derived for many other comets.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 310; L61-L65
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  • 7
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    Coma morphology and dust-emission pattern of periodic Comet Halley. IV - Spin vector refinement and map of discrete dust sources for 1910 (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A hypothetical continuous ejection of dust from discrete emission sources on the sunlit hemisphere of a rotating comet nucleus is tested against 34 digitally processed plates of Comet Halley over the May 5-June 6, 1910 period, as well as the reported projected lengths of six antisunward jets observed between May 14 and June 6, 1910. A map of the comet's nucleus is presented of whose 13 discrete dust sources only two can be modeled as point-like regions. Attention is given to curious cases of 'chain' activation in which the sources that intersect one another on the surface emit dust sequentially, in successive rotations.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 92; 462-482
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  • 8
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    Dust jets in comet Halley observed by Giotto and from the ground (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A hypothesis for the short-lived, intermittent discrete sources of dust on the nucleus surface of comet Halley has been confirmed by closeup imaging by a camera aboard the Giotto probe. A previous conclusion for the nonexistence of jet emission from the dark side of the nucleus, reached on the basis of analysis of ground-based data, is also confirmed. Attention is given to such issues as possible spin vector variations for comet Halley over the 76-year period, the survival of dust sources, and the positions of the prime meridian at the two returns to the sun.
    Keywords: ASTRONOMY
    Type: Nature (ISSN 0028-0836); 321; 357-361
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  • 9
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    Coma morphology and dust-emission pattern of periodic comet Halley. III - Additional high-resolution images taken in 1910 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: High-resolution photographic images of comet Halley obtained at Lick, Helwan, Lowell, and Vienna observatories during May-June 1910 are analyzed using the image-processing algorithm of Larson and Sekanina (1984). The results are presented in tables and compared with analyses of Mt. Wilson plates for the same period (Sekanina and Larson, 1984), and good general agreement is noted. Consideration is given to the position of the rotation pole, features indicative of the nucleus spin rate, the spokelike structure observed on May 21-22, and the expanding gas halo.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 90; 823-826
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  • 10
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    No. 102. Venus photographs. Part 1 - Photographs of Venus taken with the 82-inch telescope at McDonald Observatory, 1950-1956 (1969)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Photographs of Venus taken by 82-inch telescope
    Keywords: SPACE SCIENCES
    Type: COMMUN. OF THE LUNAR AND PLANETARY LAB., VOL. 6, PT. 4, NO. 100-104 1969; P 251-262
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