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  • 1
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    Determination of lunar ilmenite abundances from remotely sensed data (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The mineral ilmenite (FeTiO3) was found in abundance in lunar mare soils returned during the Apollo project. Lunar ilmenite often contains greater than 50 weight-percent titanium dioxide (TiO2), and is a primary potential resource for oxygen and other raw materials to supply future lunar bases. Chemical and spectroscopic analysis of the returned lunar soils produced an empirical function that relates the spectral reflectance ratio at 400 and 560 nm to the weight percent abundance of TiO2. This allowed mapping of the lunar TiO2 distribution using telescopic vidicon multispectral imaging from the ground; however, the time variant photometric response of the vidicon detectors produced abundance uncertainties of at least 2 to 5 percent. Since that time, solid-state charge-coupled device (CCD) detector technology capable of much improved photometric response has become available. An investigation of the lunar TiO2 distribution was carried out utilizing groundbased telescopic CCD multispectral imagery and spectroscopy. The work was approached in phases to develop optimum technique based upon initial results. The goal is to achieve the best possible TiO2 abundance maps from the ground as a precursor to lunar orbiter and robotic sample return missions, and to produce a better idea of the peak abundances of TiO2 for benefaction studies. These phases and the results are summarized.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA Space Engineering Research Center for Utilization of Local Planetary Resources; 6 p
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  • 2
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    Cometary spectroscopy and imaging (1991)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The objective is to investigate the spectroscopic and morphological characteristics of comets and selected minor planets over a wide range of heliocentric distances as they may suggest or constrain models of cometary processes, their formation environments and evolution. Direct images of all observable comets and 300-800 nm spectra of the brighter ones are obtained on a monthly basis with a charge coupled device spectrograph-camera. The direct images may be used for astrometry, photometry, and studies of coma and tail morphology. In some cases, anisotropic dust emission can provide information on the nucleus spin vector. Spectra may provide data on strengths of the principle emission for comparison of gas/dust ratios of a large sample of comets. Long integrations of minor planets in comet-like and nearby orbits are made to search for faint comae.
    Keywords: ASTRONOMY
    Type: NASA, Washington, Reports of Planetary Astronomy, 1991; p 75-76
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  • 3
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    Storm on Saturn (1991)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: In September 1990, a white spot appeared on Saturn's atmosphere, which later spread over the entire equatorial region. The accompanying images were obtained as part of an effort to refine techniques for obtaining high resolution groundbased charge coupled device (CCD) images of the planets, and show the turbulent disturbance in Saturn's atmosphere. These broad red-band CCD images were obtained in November 1990 with the Catalina 1.5 m telescope. The planet was low in the sky at sunset, but the viewing was good enough to show detail in the equatorial region over all longitudes. Visibility of the features is enhanced by digital spatial filtering techniques. A storm of this magnitude has not been seen on Saturn since 1933.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington, Reports of Planetary Astronomy, 1991; p 169
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  • 4
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    Near-nucleus H2O(+) structures in comets Brorsen-Metcalf, Okazaki-Levy-Rudenko, and Austin (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Comets P/Brorsen-Metcalf, Okazaki-Levy-Rudenko, and Austin were all observed to have well developed H2O+ structure close to the nuclei that showed changes on a time scale of only a few minutes. Some preliminary data on the observed ion morphology and their evolution is presented.
    Keywords: ASTROPHYSICS
    Type: Southwest Research Inst., Workshop on Observations of Recent Comets (1990); p 121-127
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  • 5
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    Evaluating some computer exhancement algorithms that improve the visibility of cometary morphology (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Digital enhancement of cometary images is a necessary tool in studying cometary morphology. Many image processing algorithms, some developed specifically for comets, have been used to enhance the subtle, low contrast coma and tail features. We compare some of the most commonly used algorithms on two different images to evaluate their strong and weak points, and conclude that there currently exists no single 'ideal' algorithm, although the radial gradient spatial filter gives the best overall result. This comparison should aid users in selecting the best algorithm to enhance particular features of interest.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Lunar and Planetary Inst., Asteroids, Comets, Meteors 1991; p 337-343
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  • 6
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    Are Hyperion and Phoebe Linked to Iapetus? (1999)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Narrowband reflectance spectra of the Saturnian satellites S VII Hyperion and S IX Phoebe were obtained across the 0.4 - 0.8 micron spectral region. The spectrum of Phoebe is similar to the spectrum of a C-class asteroid, with an absorption feature centered near 0.43 micron superimposed on the UV/blue intervalence charge transfer transition present in the spectrum. The spectrum of Hyperion shows the strong spectral slope apparent in spectra of many outer Solar System materials and attributed to organics. We use a linear mixing model to separate the reflectance spectrum of the dark material on Hyperion from the icy material. A distinct absorption feature centered at 0.67 micron is present. A slight inflection near 0.4 - 0.6 micron and change in slope near 0.73 micron suggesting the lower wavelength edge of an absorption are also present. These absorptions are very similar to those identified in the spectrum of the dark material on the surface of Iapetus, suggesting that the dark material on these two satellites is compositionally similar and has a similar origin. These absorption features are attributed to the (6)A(sub 1) yields (4)T(sub 2)(G) and (6)A(sub 1) yields (4)T(sub 1)(G) ferric charge transfer transitions in iron alteration minerals such as goethite and hematite that are products of the aqueous alteration of anhydrous silicates.
    Keywords: Lunar and Planetary Science and Exploration
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  • 7
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    Near-nucleus optical observations of P/Halley (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The Near-Nucleus Studies Net of the International Halley Watch has obtained an extensive series of high resolution optical images of P/Halley during its most active phases in 1985-86 which may be useful in interpreting radio observations of Comet Halley. They often show coma structure resulting from anisotropic emission of dust and gas from the inhomogeneous nucleus. Images were obtained in broadband spectral regions to study dust coma morphology, and in medium to narrow spectral bands to isolate the principal emissions of CN, C3, C2, CO+ and H2O+. The goals and methods of near-nucleus studies are discussed and recent studies of 1910 images are briefly reviewed. The role of dust jets and cometary activity in P/Halley is discussed and several examples of anisotropic emission of dust during the current apparition are shown.
    Keywords: ASTROPHYSICS
    Type: Cometary radio astronomy; Sept. 24-26, 1986; Green Bank, WV; United States
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  • 8
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    Evaluation of the sensitivity of reflectance ratios to mafic minerals in the lunar regolith (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The 950/560-nm spectral ratio has been traditionally used as a qualitative indicator or lunar soil maturity because the 950-nm band falls within the major Fe(2+) mineral absorption bands near 1-micron characteristic of relatively immature crystalline surfaces. Since there are several other processes unrelated to maturation that may affect this ratio value, the 950/730-nm ratio has been evaluated as a potentially better measure of the relative 1-micron band strength. It is found that the 950/730-nm ratio appears to be much more sensitive to the 1-micron band depth, but it is believed that other unknown variables preclude using these single ratios to provide meaningful quantitative results at this time.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 18; 2149-215
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  • 9
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    Remote sensing of potential lunar resources. I - Near-side compositional properties (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Using telescopic CCD multispectral images of the lunar near side and the results of 330-870 nm spectroscopy of selected regions, the compositional differences relevant to the locations of potential lunar resources (such as ilmenite, FeTiO3, and solar-wind-implanted He-3 and H) are estimated. The 400/560 nm CCD ratio images were converted to weight percent TiO2, and the values were used to construct a new TiO2 abundance map which can be used to estimate the areas potentially rich in ilmenite. A 950/560 nm CCD ratio mosaic of the full moon provides estimates of relative surface maturity. Since high He-3 concentrations correlate with mature ilmenite-rich soils, a combination of relative surface maturity maps and the TiO2 abundance maps can be used to estimate distributions of He-3 (and possibly H) on local scales.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 18
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  • 10
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    A reevaluation of spectral ratios for lunar mare TiO2 mapping (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The empirical relation established by Charette et al. (1974) between the 400/560-nm spectral ratio of mature mare soils and weight percent TiO2 has been used extensively to map titanium content in the lunar maria. Relative reflectance spectra of mare regions show that a reference wavelength further into the near-IR, e.g., above 700 nm, could be used in place of the 560-nm band to provide greater contrast (a greater range of ratio values) and hence a more sensitive indicator of titanium content. An analysis of 400/730-nm ratio values derived from both laboratory and telescopic relative reflectance spectra suggests that this ratio provides greater sensitivity to TiO2 content than the 400/560-nm ratio. The increased range of ratio values is manifested in higher contrast 400/730-nm ratio images compared to 400/560-nm ratio images. This potential improvement in sensivity encourages a reevaluation of the original Charette et al. (1974) relation using the 400/730-nm ratio.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 18; 2153-215
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