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  • LUNAR AND PLANETARY EXPLORATION  (7)
  • ASTRONOMY  (6)
  • 1980-1984  (13)
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Years
Year
  • 1
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    Near-nucleus studies of Comet Halley (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The near-nucleus dust coma structure of Comet Halley are studied using modern digital image processing techniques on photographs taken in 1910. Recent investigations carried out in conjunction with the Near-Nucleus Studies Net of the IHW to better understand the characteristics and behavior of Comet Halley are reviewed. A new image processing algorithm developed to enhance coma feature boundaries permits their evolution over as many as three days to be followed. The features can be modeled to derive information on the nucleus spin vector, particle sizes, ejection velocities and distribution of emission areas on the nucleus. Useful contributions by observers in the Astrometry Net are also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL Cometary Astrometry; p 14-20
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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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
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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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
    Format: text
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  • 4
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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
    Format: text
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  • 5
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    Observations of the Saturn E ring and a new satellite (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It is noted that the faint E ring of Saturn appears as a narrow ring 246,000 + or - 4000 km from the center of Saturn on photographs taken when the ring-plane inclination was 5.4 deg. The apparent brightness of the ring was uniform at all observed orbital longitudes and makes it possible to estimate the normal optical thickness. In addition, a faint satellite (1981S1) was observed near the L4 triangular libration point of Tethys; this satellite is probably the same object as 1980S13.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 47; Aug. 198
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  • 6
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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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  • 7
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    Summary of optical groundbased E ring observations at the University of Arizona (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Photographic and CCD images of Saturn's E ring were obtained by a 154 cm telescope, edge-on and with the ring plane inclined at 5 and 10 deg. Radial structure and brightness; temporal brightness variations; and spectral reflectivity data are summarized.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: CNES Planetary Rings; p 111-114
    Format: text
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  • 8
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    Multi-ring basin formation - Possible clues from impact cratering calculations (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Finite difference continuum mechanics code calculations make it possible to vary the controlling variables in an impact event and to determine basic trends at scales unavailable to experimental analysis. Orphal et al. (1980) have summarized the results of a pair of such calculations for identical projectile/target characteristics but different impact velocities. One calculation considered a relatively low velocity iron impactor (5 km/s); the other, a high velocity iron impactor (15.8 km/s). The primary purpose was to investigate the generation and transport of impact melt for the two impact energies. Attention is given to crater growth, crater ejecta, and possible implications for basin-size events. Based on extrapolations, a new scenario is proposed. The scenario incorporates elements of several existing basin models.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Multi-ring basins: Formation and evolution; Nov 10, 1980 - Nov 12, 1980; Houston, TX
    Format: text
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  • 9
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    Impact melt generation and transport (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The results from the first two calculations in a series of continuum mechanics computer code calculations, investigating the effects of variations in impactor mass and velocity on the generation and transport of impact melt, are reported. In the present calculations, the impactor is modeled as a spherical iron projectile with a mass of one trillion grams, and the target as a gabbroic anorthosite (GA) half-space, where the cases calculated have impact velocities of 5 and 15.8 km/sec. Early-time ejection velocities are 1-2 km/sec in both cases. The first calculation results in 0.07 projectile masses of GA being partly or completely melted, with all the melted GA being ejected from the crater, and a maximum impact range for the ejected melted material of 30 km. The second calculation yields 10.4 projectile masses of melted GA, 50% of which is ejected from the crater to ranges of up to about 130 km. Peak shock pressure attenuation with depth is reported for both cases, and transient cavity dynamics are described and compared to that for surface and near-surface explosions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 17, 1980 - Mar 21, 1980; Houston, TX
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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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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