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  • 1
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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
    Format: text
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  • 2
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    Cometary spectroscopy (1986)
    In:  CASI
    Details
    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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  • 3
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    The modern role of visual observations of comets (1991)
    In:  Other Sources
    Details
    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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  • 4
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    Dust jets in comet Halley observed by Giotto and from the ground (1986)
    In:  Other Sources
    Details
    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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  • 5
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    Coma morphology and dust-emission pattern of periodic Comet Halley. I - High-resolution images taken at Mount Wilson in 1910 (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A radial/rotational shift-difference algorithm has been developed to improve visibility of the May-June 1910 high-resolution images taken at Mount Wilson of Comet Halley. Dust features for a period of up to three days were identified, which consisted of discrete active areas emitting dust continuously from the sunlit hemisphere of the rotating nucleus. A lower limit of the comet's rotation period was approximated at one day, and expansion velocities of the dust features were determined to be in the range of 0.2-0.3 km/s. Based on relative photometry of a bright jet, it was proposed that the column density of dust ejecta in the jet exceeded the density in the coma by a factor greater than or approximately equal to two, and that, if narrow along the line of light, the jet might have had a particle number concentration much higher than the coma background. Also noted are numerous ion features.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 89; 571-578
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  • 6
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    The 1966 observations of the coorbiting satellites of Saturn, S10 and S11 (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Most of the positions of faint satellite images obtained during the 1966 Saturn ring plane crossing fit the period of the coorbital satellites 1980 S1 and 1980 S3. In 1966 the satellites were separated by 137 deg in orbital longitude. Until the mutual interaction of the satellites is understood and applied to derive the precise orbital motion, the 1966 and 1980 observations cannot be linked.
    Keywords: ASTRONOMY
    Type: Icarus; 46; May 1981
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  • 7
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    A new Saturnian satellite near Dione's L4 point (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A new satellite of Saturn, discovered by Laques and Lecacheux, has been observed on a number of occasions and its orbit determined. It has a period of 2.73614 plus or minus 0.00006 days and occupies the leading Lagrangian point (L4) of Dione. A second object has been observed on one night which may be near the L5 point of Dione.
    Keywords: ASTRONOMY
    Type: Icarus; 43; July 198
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  • 8
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    Charge coupled device (CCD) spectroscopy of comets - Tuttle, Stephan-Oterma, Brooks 2, and Bowell (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: CCD technology allows the acquisition of high quality spectra from faint comets that provide simultaneous spatial and spectral resolution. Most emissions in the spectra thus obtained are due to CN and NH2. The most interesting results for the continuum were displayed at comet Bowell, whose coma is a factor of 10 more extended than the other comets studied. Calculated production rates are presented for NH2 and CN in the cases of the comet Tuttle and Stephan-Oterma, and first-order comparisons are conducted for measured production rates and those of the H2O molecule, which should be the dominant one in comet activity.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 60; 351-372
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  • 9
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    A systematic program of cometary spectroscopy (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Some early results of a systematic program of observing the spectroscopic behavior of comets as a function of heliocentric distance are presented. An ultraviolet sensitive microchannel plate intensifier spectrograph was used to record the 3000-5000A spectrum of comets brighter than magnitude 17 with a spectral resolution of 8 or 16A, followed by direct image for better interpretation of the spatial distribution of spectral features. Although the goals of the program require much more time and data, some interesting results from Comets Schwassmann-Wachmann, 1, Bradfield and Bowell were obtained.
    Keywords: ASTRONOMY
    Type: JPL Mod. Observational Tech. for Comets; p 110-114
    Format: application/pdf
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  • 10
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    Comet Bowell (1980b) - Measurement of the optical thickness of the coma and particle albedo from a stellar occultation (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Comet Bowell (1980b) was observed to pass within 0.25 + or 0.09 arc sec of a star (about 540 km at the comet), where the absorption of starlight by the dust coma was found to be 3 percent (+ or - 1 percent). The implied optical thickness of 0.03 differs greatly from other determinations and gives a mass of 3 x 10 to the 13th g for the coma within 10,000 km of the nucleus. Coupled with absolute continuum filter photometry, these results indicate a very low particle albedo consistent with fluffy carbonaceous material. This experiment indicates the need to observe nearly central occultations by several observers to measure the optical thickness profile of a comet. The advantages of using a charge-coupled device area photometer for such observations are discussed.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 58; 446-450
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