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  • General Chemistry  (1.962)
  • Chemical Engineering  (1.399)
  • LUNAR AND PLANETARY EXPLORATION  (1.134)
  • AERODYNAMICS  (1.098)
  • 1985-1989  (5.593)
  • 1980-1984
  • 1988  (2.872)
  • 1986  (2.721)
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  • 1985-1989  (5.593)
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  • 1
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    The Lunar Orbital Prospector (1988)
    In:  CASI
    Details
    Publikationsdatum: 2005-07-19
    Beschreibung: The Moon is a body rich in natural resources and full of intriguing scientific questions, and it will most certainly play a central role in the growth of near-Earth and deep space ventures of the twenty-first century. The LOP mission is an example of one way to catalog the Moon's natural resources and to answer lunar science questions in parallel. In a realistic planetary exploration program, this mission must compete with other interesting planetary missions and therefore the LOP must be as low cost and adaptable as possible. This flexibility is reflected in the LOP's heavy design emphasis on modularity. The LOP mission can easily be expanded to include new technologies, and additional orbiters could be launched into lunar orbit to provide a constellation of remote-sensing platforms. This design thus projects a broad range of possibilities for continued lunar exploration in the next century.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: USRA, NASA(USRA University Advanced Design Program Fourth Annual Summer Conference; p 145-151
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  • 2
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    Planetary spectroscopy (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Spectroscopic and spectrophotometric data on the atmospheres of comets, the outer planets, and Titan at ultraviolet to near-infrared wavelengths were acquired. These data support an effort aimed at characterizing the physical properties and distribution of aerosol particles in the atmospheres of these bodies. New spectrophotometry was acquired of Uranus at 0.2 lambda 0.3 micrometer with IUE; archival IUE spectrophotometry of Uranus and Neptune in this wavelength range was acquired and recalibrated. New estimates of radiometric Bond albedos and global energy budges of Uranus, Neptune and Titan were published.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 19
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  • 3
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    Infrared observations of outer planet satellites (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Infrared observations were made of the outer planet satellites. These data provide vital information about the thermophysical properties of satellite surfaces, including internal heat sources for Io. Observations include both broad and narrow band measurements in the 2 to 20 micrometer spectral range. Types of observation and target priority were determined to make maximum use of existing data from Voyager and other missions, on-going and planned missions such as Galileo, were supported and techniques and data for planning new missions and instrumentation were developed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 38
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  • 4
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    Studies of extended planetary atmospheres (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Telescopic observations were made of gases and plasmas in the Jupiter system, and related phenomena such as the recently-discovered sodium atmosphere of Mercury. Sodium absorption in Io's atmosphere was observed to distances as large as 5 Io radii during the mutual-eclipse season of the Jovian satellites. Analysis of Jovian disk spectra has proceeded, as planned, from an emphasis on the H2 ortho-para ratio to analysis of methane absorptions and determination of cloud structure. Several 2-channel photometers were constructed in 1978 for the Uranus event at which the rings were discovered and a smaller, single-channel unit was built more recently. Although the photometers themselves are still fully usable, the data-acquisition systems have major deficiencies.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 34-35
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  • 5
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    Search for volatiles in the surface of icy satellites (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: It is proposed to measure the reflectance spectra of the icy satellites of Jupiter, Saturn and Uranus in the spectral region 1.8 to 2.4 micrometers. These observations use the new Cooled Grating Array Spectrometer using a 32-element InSb photodiode array detector and produce spectra of higher resolution and precision than any data yet obtained; the ultimate scientific objective is to search for the signatures of methane clathrate, ammonium hydroxide or carbon monoxide clathrate (compounds predicted to exist on icy surfaces in the outer solar system by several theories of formation of these bodies) in the region of the spectrum where water ice has a relative maximum in reflectance. At the very least, these data will allow upper limits to be placed on the amount of these chemical species that can be present. The specific targets is Europa, Ganymede, Enceladus, Ariel and Titania, bodies that have the highest probability of having some or all of these volatiles on their surface according to current formation models.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 20
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  • 6
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    Shuttle Tethered Aerothermodynamics Research Facility (STARFAC) (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The Earth's atmosphere from 90 km to 200 km provides the last aerothermodynamics frontier. Present NASA programs which require but also can provide an understanding of the aerodynamics and aerothermodynamics of the free molecule and transition flows that exist at these altitudes are the Aeroassisted OTV, Entry Research Vehicle and the Tethered Satellite. Each of these programs provides a unique opportunity to do flight research in the rarefied upper atmosphere. However, the Tethered Satellite Program provides, because of its capability to obtain global, in-situ, steady state data, the greatest potential to: (1)define the performance of aerodynamic shapes as a function of environmental characteristics (free molecule, transition, slip flow regimes); (2)define the characteristics of the upper atmosphere and the global variability of properties such as composition temperature, pressure and density. Such data are required to accomplish the systematic development and verification of analytical prediction techniques required to support advance configuration designs.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA, Washington Applications of Tethers in Space: Workshop Proceedings, Vol. 2; p 265-285
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  • 7
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    New techniques for the detection and capture of micrometeoroids (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: In order to understand the origin and distribution of the biogenic elements and their compounds in the solar system, it will be necessary to study material from many classes of objects. Chemical, elemental, and isotopic measurements of returned samples of comets, asteroids, and possibly extra-solar system dust clouds would provide information on a particularly important class: the primitive objects. Extraterrestrial micron-sized particles in the vicinity of earth are one source of such materials that might otherwise be inaccessible. The Space Station appears to be an eminently suitable platform from which to collect and detect these various particles. The primary challenge, however, is to collect intact, uncontaminated particles which will be encounted at tens of kilometers per seconds. A concept for a micrometeoroid detector that could be deployed at a Space Station has been developed which uses a large area detector plate implanted with acoustic transducers. When an impact event occurs, the resulting signal is subjected to spectral analysis providing positive detection, momentum information, and angle of incidence. The primary advantage of this detector is the large area which increases the probability of measuring events.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Second Symposium on Chemical Evolution and the Origin and Evolution of Life; p 59
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  • 8
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    Experimental basis for a Titan probe organic analysis (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The recent Voyager flyby of Titan produced evidence for at least nine organic compounds in that atmosphere that are heavier than methane. Several models of Titan's atmosphere, as well as laboratory simulations, suggest the presence of organics considerably more complex that those observed. To ensure that the in situ measurements are definitive with respect to Titan's atmosphere, experiment concepts, and the related instrumentation, must be carefully developed specifically for such a mission. To this end, the possible composition of the environment to be analyzed must be bracketed and model samples must be provided for instrumentation development studies. Laboratory studies to define the optimum flight experiment and sampling strategy for a Titan entry probe are currently being conducted. Titan mixtures are being subjected to a variety of energy sources including high voltage electron from a DC discharge, high current electric shock, and laser detonation. Gaseous and solid products are produced which are then analyzed. Samples from these experiements are also provided to candidate flight experiments as models for instrument development studies. Preliminary results show that existing theoretical models for chemistry in Titan's atmosphere cannot adequetely explain the presence and abundance of all trace gases observed in these experiments.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Second Symposium on Chemical Evolution and the Origin and Evolution of Life; p 52
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  • 9
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    Visible phase curves of Uranus and Neptune and scattering in their atmospheres (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The Voyager 1 and Voyager 2 narrow angle cameras have been imaging Uranus and Neptune (through several filters) from distances of several AU for the past four years. The justification for this is to determine the way in which the albedoes of the two planets vary with angle from the sun. The Voyager 1 spacecraft has already reached a phase angle of approx. 40 deg. for Neptune and approx. 70 deg. for Uranus. The albedo of a gaseous planet depends on the phase angle (angle from the sun through the planet to the observer), the color being observed, and the vertical distribution and nature of aerosols and clouds in the atmosphere of the planet. Since the colors are known and the phase angles, and phase curves will be used to constrain models of the aerosol and cloud structrures of Uranus and Neptune. A knowledge of the way albedo varies with phase angle allows one to compute the total amount of sunlight being absorbed by a planet. With knowledge of the solar flux incident on the planet and knowledge of how much infrared is being emitted by the planet (at least in the direction of the Earth and sun) one can determine a rough extimate of the internal heat source of the planet. Although Jupiter and Saturn have measured internal heat sources of magnitude comparable to their absorbed energy from the sun, preliminary results indicate that Uranus may not have an internal heat and that Neptune if it has one that heat source is small.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 64
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  • 10
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    Planetary research at Lowell Observatory (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Narrowband CCD profiles of C2 and grains in several comets (including P/Halley and P/Giacobini-Zinner) were performed. Rotational light curves were made of Comet P/Arend-Rigaux (visible and infrared) yielding the size, shape, albedo, and rotation period of the nucleus. Production rates were measured as a function of heliocentric distance for OH, CN, and C2 in P/Giacobini-Zinner and for OH, NH, CN, C3, and C2 in P/Halley. Detection and measurement was made of forbidden (O I) lines near 6300 and 5577 A in P/Halley, permitting the production rate of oxygen from CO to be distinguished from that from H2O. Identification of C-12C-13 lines in cometary spectra indicating a possible enrichment of C-13 over the telluric value was made. An assessment of techniques for detecting (determining the existence of) a trans-Neptunian comet belt is included.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 68-70
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  • 11
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    Modeling and investigative studies of Jovian low frequency emissions (1986)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The Voyager data in a newly produced noise-reduced and recalibrated format has been received. New color spectrograms were developed on high resolution color terminals which display this data. The production of these new spectrograms utilizing the new format data is quite important, because it eliminates a serious problem of noise contamination and miscalibration in the old data set. In addition, a new Jovian plasma model was introduced, which includes the Io torus and accounts for 7 ionic species. The new plasma model is important in the ray tracing of hectometric (HOM) and kilometric (KOM) radiation which may be influenced by the Io torus.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 44-45
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  • 12
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    Long-term changes in reflectivity and larger scale motions in the atmospheres of Jupiter and Saturn (1986)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: A multi-color, broad-band photographic program for monitoring atmospheric variability of Jupiter and Saturn with the 61-cm, f/75 telescope was continued. The archivial product consists of approximately 20 sequential images on 3 1/4 x 4 1/4 glass plates with a plate scale of 4.53 arc sec/mm. An eleven-step sensitometric wedge, recorded times of acquisition, and fiducial marks which determine the orientation of the plate, are recorded on each individual plate. This allows accurate positional measurements, as well as detailed relative surface brightness determinations. Detailed measurements of the Red Spot are being utilized in a study of zonal velocity variation and the ability to predict the longitude of the Red Spot during the Galileo mission. An ongoing 5-color series of Saturn has been maintained to map the seasonal changes in the belt-zone reflectivity. Digitization of a series of blue images containing the Red Spot and a series of red and blue images excluding the Red Spot are being processed and reduced to normalized surface brightness maps. This data is being utilized to map time-dependent brightness variations of selected features, belts, and ones.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 17-18
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  • 13
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    Interiors of the giant planets (1986)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: The interior structure of the Jovian planets was studied by means of observational data obtained by ground-based astronomy. Recent work was oriented toward a determination of oblateness from occultation measurements of the shape of planetary atmospheres. This provides a determination of the degree of central condensation of the planet, which is then compared with interior models and theoretical equations of state. As a serendipitous result of the attempts to measure the oblateness of Neptune, a partial Neptune ring (or arc) was discovered following an occultation observation on July 22, 1984. During 1985, older observations were reexamined to determine whether Neptune arcs had been detected (but not identified) during previous occultations. It appears that Neptunian arcs may locally imitate Uranian rings, with an 1981 event resembling Uranus' epsilon ring, while an 1984 event was more similar to the thinner Uranian rings such as the alpha ring.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 32-33
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  • 14
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    Theoretical and observational planetary physics (1986)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: This program supports NASA's deep space exploration missions, particularly those to the outer Solar System, and also NASA's Earth-orbital astronomy missions, using ground-based observations, primarily with the NASA IRTF at Mauna Kea, Hawaii, and also with such instruments as the Kitt Peak 4 meter Mayall telescope and the NRAO VLA facility in Socorro, New Mexico. An important component of the program is the physical interpretation of the observations. There were two major scientific discoveries resulting from 8 micrometer observations of Jupiter. The first is that at that wavelength there are two spots, one near each magnetic pole, which are typically the brightest and therefore warmest places on the planet. The effect is clearly due to precipitating high energy magnetospheric particles. A second ground-based discovery is that in 1985, Jupiter exhibited low latitude (+ or - 18 deg.) stratospheric wave structure.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 21-22
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  • 15
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    Radiative transfer in planetary atmospheres (1986)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: The research effort was concentrated toward comet P/Halley, although observations of other comets including Giacobini-Zinner, Hartley-Good and Thiele were made as opportunities arise. In preparing for the apparition of P/Halley, detailed predictions for the emission in the 18 cm OH transitions were made in order to assist observers and to indicate what type of data would be particularly valuable. Likewise, since occultations by the comet of background radio sources can provide unique types of information, the tracks of P/Halley and P/Giacobini-Zinner were surveyed with the NRAO Very Large Array, background sources were mapped, and a catalogue of occulted sources published. Beginning in September, 1985, regular observations of the 18 cm OH lines have been made for P/Halley using the 43 m antenna of the NRAO in Greenbank, West Virginia. These data promise to provide the most accurate time sequence for the OH emission for any comet ever obtained at radio wavelengths. From the linewidth and shape, information is obtained on the kinetics of the gas in the cometary coma. An extensive series of observations have been undertaken with 14 m antenna to study emission from the HCN molecule in P/Halley. These data provide the first definitive detection of this component of the cometary ices. Interesting variations in the production of HCN were observed with time scales less than a day. Likewise, there appeared to be variations in the ratio of the hyperfine components of the J = 1-0 transition.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 96-97
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  • 16
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    Chronology and isotopic geochemistry of apollo 14 basalts and Skaergard Gabbro, Eastern Greenland (1986)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: Work completed on Apollo 14 basalts has been published. The two dates obtained from these rocks comprised the oldest and two of the three oldest ages (4.1 and 4.3 billion years) known for lunar maria basalts; thus their ages are important in understanding the moon's earliest history. Owing to the antiquity of these rocks, two more fragments have been dated as part of a second ASEE/NASA SFF program. The new ages are 3.95 and 4.12 billion years, thus further establishing and amplifying the earlier results. This work, although perhaps more interesting for its chronologic information, was begun as a test of chemical and petrographic models. Fragments of Apollo basalt were placed into five categories, based on petrologic and chemical, especially rare-earth element, composition. Isotopic studies were begun in an attempt to determine if the five groups of basalts were related by age or initial isotopic composition (isotopic composition of lava at time of extrusion). Although a few of the representatives of the five groups have the same age and/or initial strontium-isotopic composition, within the analtytical uncertainties, most apparently are unrelated. Petrologic implications of these data will be published in an appropriate journal.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA. Johnson Space Center NASA/American Society for Engineering Educatio; NASA. Johnson Space
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  • 17
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    Measurements of physical properties of model Titan atmospheres (1986)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: One aspect of the study of Titan's atmosphere is the elucidation of the chemical and physical nature of the aerosols. In order to facilitate this, a program to produce laboratory synthesized model materials for Titan's aerosol and to study their chemical and physical properties is now in progress. Various processes, including electric discharge, photolysis by ultraviolet light, and irradiation by energetic particles, will be used to produce the materials. A first set of experiments where a nominal Titan mixture (97%N2, 3% CH4, 0.2% H2) was subjected to pulsed high temperature shocks yielded a reddish brown waxy solid. This material was subjected to pyrolysis/gas chromatography, a technique that has been proposed as a method for analysis of the Titan aerosols. Preliminary results show the material to consist of simple hydrocarbons but little else, at least up to temperatures of 600 C. Since the material was colored, compounds other than those mentioned above must be present.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Second Symposium on Chemical Evolution and the Origin and Evolution of Life; p 50
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  • 18
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    Design of a lunar transportation system (1988)
    In:  CASI
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    Publikationsdatum: 2005-07-19
    Beschreibung: The establishment of lunar bases is the next logical step in the exploration of space. Permanent lunar bases will support scientific investigation, the industrialization of space, and the development of self-sufficiency on the Moon. Scientific investigation and research and development would lead to applications utilizing lunar material resources. By utilizing these resources, the industrialization of space can become a reality. The above two factors coupled with the development of key and enabling technologies would lead to achievement of self-sufficiency of the lunar base. Attention was focused on specific design(s) to be pursued during subsequent stages in advanced courses. Some of the objectives in the project included: (1) minimizing the transportation of construction material and fuel from earth, or maximizing the use of the lunar material; (2) use of novel materials and light weight structures; (3) use of new manufacturing methods and technology such as magnetically levitated, or superconducting materials; and (4) innovative concepts of effectively utilizing the exotic lunar conditions, i.e. high thermal gradients, lack of atmosphere, zero wind forces, and lower gravity, etc.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: USRA, NASA(USRA University Advanced Design Program Fourth Annual Summer Conference; p 89-92
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  • 19
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    Unsteady transonic flow calculations for wing/fuselage configurations (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 23; 897-903
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  • 20
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    Circulation control airfoils as applied to rotary-wing aircraft (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 23; 865-875
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  • 21
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    Mass spectrometric study of the mercury isotopes in the Allende meteorite (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Isotopic abundance ratios for mercury were determined by mass spectrometry in six samples of bulk material and in one sample of chondrules from the Allende meteorite. A primary purpose of the work was to attempt to verify the anomalous ratios reported for Hg-196/Hg-202 by neutron activation. Measurements were made on the mercury released at temperatures of 250, 450, 600 C, and in some cases, higher temperatures. The precision of the measurements was such that if an anomaly of the magnitude reported exists, it should have been seen. The isotopic abundance ratios for the other mercury isotopes were also measured. Within the errors of measurement these agreed with normal terrestrial values.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 91; E124-E12
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  • 22
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    Linear volcanic features at Alba Patera, Mars - Probable spatter ridges (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A number of extensive linear constructional features occur on the north and east flanks of Alba Patera. They are found in a 150-km-wide zone and comprise aligned ridge elements that are locally associated with short volcanic flows. They are among the youngest volcanic features in the region and are believed to be Martian analogs of terrestrial spatter ridges. On the basis of measurements made on Viking images, it appears that active volcanic fissures on Mars were larger than their terrestrial counterparts.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 91; E159-E16
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  • 23
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    Shock-implanted noble gases - An experimental study with implications for the origin of Martian gases in shergottite meteorites (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The shock-implantation of gases is studied by artificially shocking whole rock and power samples of terrestrial basalt to pressures of 2-40 GPa. Ar, Kr, Xe, and Ne were implanted into the silicate. It is observed that the amount of implanted gas is linearly proportional to its partial pressure over a pressure range of 0.0001 to 0.1 atmosphere. The fractionation effect in the implanted gas and the gas diffusion properties are examined. The amounts of gas that would have been implanted with 100 percent efficiency are calculated from the measured porosities of the power samples and are compared to observed abundances. It is determined that the implantation efficiencies are approximately 0.5 percent at 2 GPa, 7 percent at 5 GPa, and greater than 50 percent at both 20 and 35 GPa. The experimental data correlate with the shock implantation of Martian gases without mass fractionation into the shock-melted phase of meteorite EETA 79001.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 91; E99-E114
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  • 24
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    Composition of the Cayley Formation at Apollo 16 as inferred from impact melt splashes (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Abundances of major and trace elements and magnetic properties of 50 impact melt splashes (IMSs) from the Apollo 16 landing site are analzyed to determine the composition of their meteoritic component. MgO-Sc and Ca-Sc variation diagrams and least-squares mixing models are utilized to analyze the IMS, soil, and rock data. Consideration is given to progenitor lithologies of the IMS, the number of impact events represented by the IMS, and the heterogeneity of impact melts from single events. It is observed that the IMSs are composed of either a mixture of anorthosite and low-Sc impact melt rocks or anorthositic norite. It is determined that the surface Cayley layer is composed of TiO2, MgO, Sc, and La concentrations of 0.69, and 7.1 wt pct and 10.5 and 21.2 microg/g, respectively and 0.38 and 5.9 wt pct and 6.1 and 11.8 microg/g, respectively, for the subsurface Cayley layer. The Descartes Formation composition is estimated as TiO2, MgO, Sc, and La concentrations of 0.25, and 3.5 wt pct and 7.7 and 2.2 microg/g, respectively.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 91; E21-E42
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  • 25
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    Apollo 16 impact-melt splashes - Petrography and major-element composition (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Petrographic and major-element analyses are applied to 50 Apollo 16 impact-melt splash (IMS) samples in order to determine their origin and assess the nature of the subregolith source. The macroscopic analyses reveal that the IMSs exhibit a glassy appearance, but the textures range from holohyaline to hyalopilitic. Schlieren-rich glasses dominate the holohyaline areas, and the crystalline areas are mainly spherulitic. It is observed that most IMSs contain feldspathic monomineralic and lithic clasts and no regolithic materials. It is detected that the chemistry of most IMSs is not like the local regolith and appears to represent varied mixtures of VHA impact-melt breccias and anorthosite; the host rocks are mainly dimict breccias. It is concluded that the Cayley Formation is a polymict deposit composed of VHA impact-melt breccias and anorthosites. Tables revealing the macroscopic characteristics of the IMSs and the major-element composition of IMSs and various host rock are presented.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 91; E3-E20
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  • 26
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    Lunar and Venusian radar bright rings (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Twenty-one lunar craters have radar bright ring appearances which are analogous to eleven complete ring features in the earth-based 12.5 cm observations of Venus. Radar ring diameters and widths for the lunar and Venusian features overlap for sizes from 45 to 100 km. Radar bright areas for the lunar craters are associated with the slopes of the inner and outer rim walls, while level crater floors and level ejecta fields beyond the raised portion of the rim have average radar backscatter. It is proposed that the radar bright areas of the Venusian rings are also associated with the slopes on the rims of craters. The lunar craters have evolved to radar bright rings via mass wasting of crater rim walls and via post-impact flooding of crater floors. Aeolian deposits of fine-grained material on Venusian crater floors may produce radar scattering effects similar to lunar crater floor flooding. These Venusian aeolian deposits may preferentially cover blocky crater floors producing a radar bright ring appearance. It is proposed that the Venusian features with complete bright ring appearances and sizes less than 100 km are impact craters. They have the same sizes as lunar craters and could have evolved to radar bright rings via analogous surface processes.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Earth, Moon, and Planets (ISSN 0167-9295); 36; 167-185
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  • 27
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    Clay-mineraloid weathering products in Antarctic meteorites (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The production of clay mineraloids (CMs) in the weathering of stony meteorites recovered in the Allan Hills and Elephant Moraine areas of Antarctica is investigated, applying electron microbeam analysis, pyrolysis/mass spectroscopy, X-ray diffractometry, and differential scanning calorimetry to whole-rock chips from two eucrites, two diogenites, and an H5 chondrite. The data are presented in tables, graphs, and photomicrographs and characterized in detail. Massive to incipient-vermicular CM formations with smectitelike or micalike compositions and indications of poor crystallization are observed and attributed to hydrocryogenic diagenesis (with little or no liquid water) on time scales of 10-1000 kyr. The need to take the compositional effects of weathering into account before attempting to reconstruct the preterrestrial histories of meteorites is stressed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 50; 2215-222
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  • 28
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    Transonic separated solutions for an augmentor wing (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 23; 837-842
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  • 29
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    Density stratification effects on wake vortex decay (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 23; 820-824
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  • 30
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    Venus - Dead or alive? (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: In situ nightside electric field observations from the Pioneer Venus Orbiter have been interpreted as evidence of extensive lightning in the lower atmosphere of Venus. The scenario, including proposed evidence of clustering of lightning over surface highland regions, has encouraged the acceptance of currently active volcanic output as part of several investigations of the dynamics and chemistry of the atmosphere and the geology of the planet. However, the correlation between the 100-hertz electric field events attributed to lightning and nightside ionization troughs resulting from the interaction of the solar wind with the ionosphere indicates that the noise results from locally generated plasma instabilities and not from any behavior of the lower atmosphere. Furthemore, analysis of the spatial distribution of the noise shows that it is not clustered over highland topography, but rather occurs at random throughout the latitude and longitude regions sampled by the orbiter during the first 5 years of operation, from 1978 to 1984. Thus the electric field observations do not identify lightning and do not provide a basis for inferring the presence of currently active volcanic output. In the absence of known evidence to the contrary, it appears that Venus is no longer active.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science (ISSN 0036-8075); 234; 1087-109
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  • 31
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    Artificial dissipation models for the Euler equations (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1931-194
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  • 32
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    Small satellites (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Satellites smaller than Mimas (r = 195 km) are distinguished by irregular overall shapes and by rough limb topography. Material properties and impact cratering dominate the shaping of these objects. Long fragmentation histories can produce a variety of internal structures, but so far there is no direct evidence that any small satellite is an equilibrium ellipsoid made up of noncohesive gravitationally bound rubble. One many bodies that orbit close to their primary the tidal and rotational components of surface gravity strongly affect the directions of local g and thereby affect the redistribution of regolith by mass wasting. Downslope movement of regolith is extensive on Deimos, and is probably effective on many other small satellites. It is shown that in some cases observed patterns of downslope mass wasting cold produce useful constraints on the satellite's mean density. The diversity of features seen in the few high-resolution images of small satellites currently available suggests that these objects have undergone complex histories of cratering, fragmentation, and regolith evolution.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 33
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    Satellites of Uranus and Neptune, and the Pluto-Charon system (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The orbital properties, surface compositions, opposition surges, masses, radii, and densities of the satellites of Uranus are presented. It is noted that the Uranian satellites are comparable in size to the largest of Saturn's icy satellites while density measurements suggest that the bulk compositions of Ariel and Umbriel might be different from those of Titania and Oberon. Consideration is given to the two satellites of Neptune and the question of a third satellite is addressed. The elements of Charon, determined from astrometric observations by photographic and speckle interferometric techniques, and then from eclipse observations, are given. The diurnal period of Pluto and its photometric lightcurve are discussed. The similarities and differences existing between the satellites of Uranus and Neptune and the Pluto-Charon pair are mentioned briefly.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 34
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    Interactions of planetary magnetospheres with icy satellite surfaces (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: When natural satellites and ring particles are embedded within magnetospheric plasmas, the charged particles interact with the surfaces of these solid bodies. These interactions have important implications for the surface, the atmosphere of the parent body, and the magnetosphere as a whole. Significant erosion of the surface by sputtering, as well as redeposition of sputter ejecta, can occur over geologic time. The surface can also be chemically modified. Sputter ejecta can make important contributions to the atmosphere; sputtering provides a lower limit to the atmospheric column density even for arbitrarily cold satellite surfaces. Sputter ejecta escaping from the parent body can form extensive neutral clouds within the magnetosphere. Ionization and dissociation within these neutral clouds can be dominant sources of low-energy plasma. The importance of these processes is discussed for the satellites and magnetospheres of Jupiter, Saturn and Uranus.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 35
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    Some background about satellites (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Four tables of planetary and satellite data are presented which list satellite discoveries, planetary parameters, satellite orbits, and satellite physical properties respectively. A scheme for classifying the satellites is provided and it is noted that most known moons fall into three general classes: regular satellites, collisional shards, and irregular satellites. Satellite processes are outlined with attention given to origins, dynamical and thermal evolution, surface processes, and composition and cratering. Background material is provided for each family of satellites.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 36
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    Thermal histories, compositions and internal structures of the moons of the solar system (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Thermal evolution models of satellites are discussed with emphasis placed on the fundamental physical processes common to all planetary bodies. A comparison is made between the different evolutionary tracks followed by individual satellites. Consideration is given to the compositions and structures of satellites, heat sources, relevant thermal and mechanical properties of the materials in satellite interiors, and heat transfer mechanisms. Thermal history scenarios are presented for the majority of the satellites of the solar system and these are related to the constraints imposed by surface geology.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 37
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    Origins of satellites (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Solar system origin and planetary formation are discussed with emphasis placed on accretion disk dynamics, disk instabilities, giant gaseous protoplanets, condensation, sedimentation, coagulation, planetesimal swarm evolution, giant planet formation, and implications for satellites. Disk formation and the dynamics of a protosatellite disk are considered as well as satellite accretion, impact disruption and ablation, and satellite capture. Possible explanations for each of the satellite systems are offered. It is concluded that satellite formation involves a variety of processes.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 38
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    Paneling methods with vorticity effects and corrections for nonlinear compressibility (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The prediction of missile aerodynamic characteristics is presently undertaken through the application of supersonic paneling methods and nonlinear corrections to the prediction of missile aerodynamic characteristics. Attention is given to supersonic panel methods and line-singularity methods for the modeling of axisymmetric bodies, in combination with corrections for nonlinear flow phenomena, which are applied to complete missile, inlets, and wing-body combinations. The LRCDM2 computer program is used as an example of the methods presented.
    Schlagwort(e): AERODYNAMICS
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  • 39
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    Vortex cloud model for body vortex shedding and tracking (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The discrete vortex cloud approach models a missile airframe's vortex wake by means that are capable of treating a variety of configurations over a range of flow conditions. Attention is given to the sheets of vorticity formed on the lee side of a missile at moderate angles-of-attack. While three-dimensional attached flow models are used to represent the missile body, two-dimensional, incompressible, separated flow models are used to represent the separated vortex wake. The predicted pressure distribution of the body under the influence of the freestream and the separation vortex wake are used to calculate aerodynamic loads on the body. The separation vortex wake is represented by clouds of discrete vortices in cross flow planes normal to the body axis.
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  • 40
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    Early thermal profiles and lithospheric strength of Ganymede from extensional tectonic features (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The early thermal profiles and the lithospheric stability and strength of Ganymede are quantitatively determined on the basis of brittle lithosphere thickness estimates derived from the width and spacing of extensional tectonic features, together with lithospheric strength envelopes for ice. Plots of the brittle and ductile yield stress vs. depth for the icy lithosphere of Ganymede exhibit a linear increase in brittle strength with depth to a maximum at the brittle-ductile transition that is followed by an exponential decrease in ductile yield stress with depth. The results obtained imply that the thermal gradient and lithospheric strength have varied laterally by factor as great as 5, and that Ganymede underwent cooling in a highly inhomogeneous fashion with lateral thermal anomalies. The present analysis furnishes reasons for the stability of large cratered terrain remnants.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 68; 252-265
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  • 41
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    Profiling Saturn's rings by radio occultation (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The development of reconstruction algorithms that correct for diffraction effects in radio occultation measurements is described. The reciprocal Fresnel transform relationship between the complex amplitude of the observed coherent signal and the complex microwave transmittance of the rings is derived using the Huygens-Fresnel formulation of the diffraction problem. The effects of the finite data segment width, the uncertainties in the Fresnel scale, systematic phase errors in the kernel of the inverse transform, reference oscillator instabilities, and random noise measurements on the resolution of the reconstructed transmittance are analyzed. Examples of reconstructed opacity profiles for some regions of Saturn's rings derived by applying the reconstruction theory to Voyager 1 at Saturn data are presented.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 68; 120-166
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  • 42
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    Interannual variability of global dust storms on Mars (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Under the assumption that the cross-equatorial Hadley circulation plays a key role in the onset of Martian global dust storms, numerical simulations indicate that a northern hemisphere dust haze weakens its intensity and, thereby, its contribution to the surface stress in the southern hemisphere. Since this in turn reduces the possibility of global dust storm development, the interannual variability observed is the result of either a competition between circulations in opposite hemispheres, in which case the variability has a random component, or it is the result of dust cycling between hemispheres, so that the variability is related to the characteristics of the global dust storms themselves.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science (ISSN 0036-8075); 234; 459-461
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  • 43
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    Affordable solar system exploration (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The design features of the Comet Rendezvous Asteroid Flyby (CRAF) version of the Mariner Mark II spacecraft are described, together with the instruments to be carried aboard and the goals of the mission. To minimize the cost, computer-aided design, engineering, and manufacturing will be used, and, where possible, established technologies and off-the- shelf products will be incorporated. Planned for a launch in 1992, the CRAF will rendezvous with the Tempel 2 comet in 1996 and will stick with it through 1999, making studies of plasma in the comet's coma and the comet's dust, gas, and nucleus by means of its penetrator rocket which will pierce the nucleus.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Aerospace America (ISSN 0740-722X); 24; 28-31
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  • 44
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    Magnetic configurations of planetary obstacles (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The interaction of the solar wind with planetlike obstacles is examined. The four different types of interactions, and the properties of the planets relative to their roles as obstacles to solar wind flow are discussed. The characteristic features of the magnetosphere of Mercury, Jupiter, Saturn, and the earth are described; particular attention is given to the configuration of the magnetosphere and the factors which control the position and shape of the magnetopause. The role of the magnetic field as it becomes modified in the solar wind interaction with nonmagnetic objects possessing an ionosphere is studied and examples of ionospheric interaction, such as Venusian and Titan interactions, are presented.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 45
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    Solar wind control of Jupiter's decametric radio emission (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Observations of the solar wind close to Jupiter are compared with the decametric radio emission (DAM), using data recorded by Voyager 1 and Voyager 2 during 1979. The Non-Io DAM, recorded by both spacecraft and combined using the superposed epoch technique, is found to correlate with the solar wind density and velocity, as well as with the interplanetary magnetic field (IMF) magnitude. In agreement with earlier work using ground-based observations, there are indications that the Non-Io DAM is somehow associated with magnetic sector structure although the precise details of the relationship are still not known and it is not clear if this is a fundamental effect or some secondary effect of intercorrelation.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 165; 1-2,
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  • 46
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    Dynamic crystallization of chondrule melts of porphyritic and radial pyroxene composition (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Dynamic crystallization experiments in which heterogeneous nucleation is an important variable have been completed on four melts of chondrule composition. Compositions were chosen to best represent chondrules with porphyritic pyroxene and radial pyroxene textures. Experimental results show that heterogeneous nucleation is essential for the formation of porphyritic textures. Without preexisting nuclei, too much supercooling is established before crystallization is initiated and the textures are more likely to be dendritic or radial. In the near total absence of nuclei, radial textures can form at cooling rates as slow as 5 C/hr in this study. By varying the heterogeneous nucleation conditions and having a melt in which the appropriate phases are stable or metastable, analogs to most of the recognized chondrule textures can be produced in a single melt composition.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 50; 1715-172
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  • 47
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    Laser velocimetry for transonic aerodynamics (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Applications of laser velocimetry to the measurement of turbulent flow properties of strong transonic viscous-inviscid interactions are reviewed. The data resulting from these studies are then discussed in relation to their importance in the development of improved viscous-flow calculation methods. Also considered are the current limitations of laser velocimetry, the need for further improvements in the method, and potential future applications.
    Schlagwort(e): AERODYNAMICS
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  • 48
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    Evidence for the existence of additional small satellites of Saturn (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Voyager-1 and 2 long exposure images were studied in a search for previously undiscovered satellites in the Saturn system. The technique used was to overlap the images with common view areas, thereby including increasingly higher-resolution images of nearby exposures with those taken at greater distances during approach. No definite identifications were made of new satellites. However, five objects were apparently detected by the survey and the orbits associated with each of the recorded photographic 'streaks' were calculated. Techniques are discussed for applying the Space Telescope to confirm or disprove the satellite status of the observed objects.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 67; 189-204
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  • 49
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    Two-dimensional blade-vortex flow visualization investigation (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1468-147
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    Comparison of finite volume flux vector splittings for the Euler equations (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1453-146
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  • 51
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    Spectral methods for modeling supersonic chemically reacting flowfields (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1461-146
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  • 52
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    Computation of sharp-fin-induced shock wave/turbulent boundary-layer interactions (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1433-144
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    Transonic airfoil calculations including wind tunnel wall-interference effects (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The results of Reynolds-averaged time-dependent inviscid and turbulent compressible Navier-Stokes computations using the implicit finite-difference approach of Steger (1978), modified by incorporating a pressure boundary condition, (PBC) to account for wall interference are compared with experimental data on a NACA 64A010 airfoil (Johnson and Bachalo, 1980) in graphs and briefly characterized. The computational approach is the same as that used by King and Johnson (1980), but a 137 x 50 mesh is used instead of a 97 x 35 mesh, and special care is taken in resolving the nose, shock, and trailing-edge regions. Imposition of PBC is shown to improve significantly the accuracy of the computations for the flowfield on the upper surface of the airfoil, shifting the shock forward to its experimentally measured position in the case of turbulent flow. The failure of the method, even with PBC, to match the experimental shock location in the case of a flow with a separation bubble is attributed to inadequacies in the algebraic turbulence model employed (Baldwin and Lomax, 1978).
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1378-138
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    Airfoil trailing-edge flow measurements (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1245-125
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    Recent developments in rotary-wing aerodynamic theory (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Current progress in the computational analysis of rotary-wing flowfields is surveyed, and some typical results are presented in graphs. Topics examined include potential theory, rotating coordinate systems, lifting-surface theory (moving singularity, fixed wing, and rotary wing), panel methods (surface singularity representations, integral equations, and compressible flows), transonic theory (the small-disturbance equation), wake analysis (hovering rotor-wake models and transonic blade-vortex interaction), limitations on computational aerodynamics, and viscous-flow methods (dynamic-stall theories and lifting-line theory). It is suggested that the present algorithms and advanced computers make it possible to begin working toward the ultimate goal of turbulent Navier-Stokes calculations for an entire rotorcraft.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1219-124
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    Applications of potential theory computations to transonic aeroelasticity (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Unsteady aerodynamic and aeroelastic stability calculations based upon transonic small disturbance (TSD) potential theory are presented. Results from the two-dimensional XTRAN2L code and the three-dimensional XTRAN3S code are compared with experiment to demonstrate the ability of TSD codes to treat transonic effects. The necessity of nonisentropic corrections to transonic potential theory is demonstrated. Dynamic computational effects resulting from the choice of grid and boundary conditions are illustrated. Unsteady airloads for a number of parameter variations including airfoil shape and thickness, Mach number, frequency, and amplitude are given. Finally, samples of transonic aeroelastic calculations are given. A key observation is the extent to which unsteady transonic airloads calculated by inviscid potential theory may be treated in a locally linear manner.
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    Algebraic grid generation about wing-fuselage bodies (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An algebraic procedure for the generation of boundary-fitted grids about wing-fuselage configurations is presented. A wing-fuselage configuration is specified by cross sections and mathematically represented by Coons' patches. A configuration is divided into sections so that several grid blocks that either adjoin each other or partially overlap each other can be generated. Each grid has six exterior surfaces that map into a computational cube. Grids are first determined on the six boundary surfaces and then in the interior. Grid curves that are on the surface of the configuration are derived from the intersection of planes with the Coons' patch definition. Single-valued functions relating approximate arc lengths along the grid curves to a computational coordinate define the distribution of grid points. The two-boundary technique and transfinite interpolation are used to determine the boundary surface grids that are not on the configuration, and transfinite interpolation with linear blending functions is used to determine the interior grid.
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    The rotation period of Uranus (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: On 24 January 1986 the spacecraft Voyager 2 transversed the innermost magnetosphere of the planet Uranus, coming as close as 4.2 Uranus radii to the planet. It is pointed out that the magnetic field data provide a direct measure of the rotation period of the planet's interior, where the field is generated. Two period determinations are reported. A combination of the obtained values provides a weighted mean value of P = 17.24 + or - 0.01 h. It is concluded that the 17.24-h rotation period has important consequences for studies of atmospheric dynamics and the internal structure and composition of Uranus. Thus, inferences regarding the internal structure can be drawn from the relationship between the observed planetary oblateness, rotation period, and gravitational moment.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature (ISSN 0028-0836); 322; 42
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  • 59
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    Martian volatiles in shergottite EETA 79001 - New evidence from oxidized sulfur and sulfur-rich aluminosilicates (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Two equivalent chips of lithology A (lith-A) and lithology C (lith-C) taken from the same interior portion of EETA 79001 shergottite have been analyzed for volatile species produced by high-vacuum pyrolysis. The lith-C was found to contain an oxidized sulfur component that does not occur in lith-A. The preterrestrial origin of this component in lith-C is supported by the occurrence in lith-C of sulfur- and chlorine-rich aluminosilicates that are not the same as Antarctic weathering products found in the control samples. The oxidation state and distribution of sulfur found in lith-C are consistent with the interpretation of EETA 79001 as a rock from Mars.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 50; 1049-105
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    Nuclear tracks, Sm isotopes and neutron capture effects in the Elephant Morraine shergottite (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Nuclear track studies, uranium concentration measurements and Sm-isotope studies have been performed on both lithologies A and B of the Elephant Morraine shergottite, EETA 79001. Track studies show that EETA 79001 was a rather small object in space with a preatmospheric radius of 12 + or - 2 cm, corresponding to a preatmospheric mass of 28 + or - 13 kg. Phosphates have U concentrations ranging from 0.3 to 1.3 ppm. There are occasional phosphates with excess fission tracks, possibly produced from neutron-induced fission of U and Th, during the regolith exposure in the shergottite parent body (SPB). Sm-isotope studies, while not showing any clear-cut excess in Sm-150, make it possible to derive meaningful upper limits to thermal neutron fluences of 2 to 3 x 10 to the 15th n/sq cm, during a possible regolith irradiation. These limits are consistent with the track data and also make it possible to derive an upper limit to the neutron exposure age of EETA 79001 of 55 Myr in the SPB regolith.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 50; 1039-104
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    Clinopyroxene REE distribution coefficients for shergottites The REE content of the Shergotty melt (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Rare-earth element (REE) distribution coefficients were measured between synthetic pyroxenes and melts similar in composition to the Shergotty intercumulus fluid. REE-doped synthetic glass samples were analyzed by means of an automated microbeam electron microprobe. The coefficients were found to exhibit a strong positive correlation with pyroxene wollastonite content. Using distribution coefficients measured for the natural phase compositions, REE abundances for the Shergotty intercumulus melt were computed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 50; 927-937
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    X-ray investigations related to the shock history of the Shergotty achondrite (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The shock stress suffered by naturally shocked materials from the Shergotty achondrite was studied using X-ray diffraction techniques and experimentally shocked augite and enstatite as standards. The Shergotty pyroxenes revealed the formation of continuous diffraction rings, line broadening, preferred orientation of small scale diffraction domains, and other evidence of substantial lattice disorders. As disclosed by the application of Debye-Scherrer techniques, they are hybrids between single crystals and fine-grained random powders. The pyroxene lattice is very resistant to shock damage on smaller scales. While measurable lattice disaggregation and progressive fragmentation occur below 25 GPa, little additional damage is suffered from application of pressures between 30 to 60 GPa, making pressure calibration of naturally shocked pyroxenes via X-ray methods difficult. Powder diffractometer scans on pure maskelynite fractions of Shergotty revealed small amounts of still coherently diffracting plagioclase, which may contribute to the high refractive indices of the diaplectic feldspar glasses of Shergotty.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 50; 905-908
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    Transient induced drag (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: In the present treatment of the calculation of forces on a wing that is suddenly brought into motion at a constant speed, attention is given to the unsteady potential's contribution to the force balance. Total bound vorticity is produced at the initial impulse. The results obtained are independent of wing aspect ratio; as time increases, this effect on the drag force becomes smaller as the vortex emanating from the trailing edge is left behind. The second contributor to induced drag is the spanwise vorticity shedding that results from the spanwise load distribution of three-dimensional wings. This contribution grows with time as the length of the wake grows.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1203-120
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    Comparison of various drag coefficient expansions using polynomials and splines (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 23; 259-263
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    Measured and predicted heating distributions for biconics at Mach 10 (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Laminar heating distributions have been measured on a 1.9 percent scale model of a generic aeroassisted vehicle taking the shape of a spherically blunted, 13-deg/7-deg biconic whose forecone section is bent upward (by 7 deg) to furnish self-trim capability at a 20-deg angle-of-attack. The results thus obtained were compared with data gathered for a straight biconic. While no Reynolds number effect on heating was noted on the windward side of the forecone, the opposite was true of the leeward side, where a Reynolds number increase caused circumferential flow separation at lower angles of attack. Generally, windward heating was predicted to within 10 percent with a computer code solving the steady, three-dimensional parabolized Navier-Stokes equations.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 23; 251-258
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    Three-dimensional adaptive grid method (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 948-954
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    Application of a supersonic Euler code (SWINT) to wing-body-tail geometries (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 23; 513-519
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    Wake hazard alleviation associated with roll oscillations of wake-generating aircraft (1986)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 23; 484-491
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    Catching the whispers from Uranus (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Sophisticated telecommunications techniques are described that were used to acquire images of Uranus, its 14 moons and ten narrow rings darker than coal. The images, equal in quality to those transmitted from Saturn several years earlier despite the signal being weaker by 6 dB due to the increased distance, were received from Voyager 2 during its January 24, 1986 flyby of Uranus. Solutions to the problem of the weakening signal were found in modifications to Voyager's image processing system and NASA's ground tracking network. In April 1985, Voyager's prime flight data computer was reconfigured to accept only nonimaging science data, and its backup, only imaging data; the latter was reprogrammed to determine only arithmetic differences between adjacent pixel intensities rather than absolute intensities. By image compression, equivalent imaging information could be sent at lower bit rates. Instead of Golay coding, Reed-Solomon onboard encoding was used. These techniques gained the equivalent of 4-dB in imaging yield. Additional improvements were gained by using earth station antennas in pairs (the Parkes radio telescope and the Canberra ground station antenna). Moves under way to prepare for the Voyager encounter with Neptune in 1989 are described (using additional antennas and arrays, scaling up the Deep Space Network antennas from 64 m to 70 m, etc.) to assure almost Saturn-equivalent pictures despite a further 3.5-dB drop in signal strength.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Aerospace America (ISSN 0740-722X); 24; 44-46
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    Motions in the interiors and atmospheres of Jupiter and Saturn. II - Barotropic instabilities and normal modes of an adiabatic planet (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A rotating and adiabatic inviscid fluid planet possesses low frequency motions that are barotropic, quasi-geostrophic and quasi-columnar. The limiting curvature at which flow becomes unstable upon projection onto the planetary surface is negative, with an amplitude that is 3-4 times that for thin atmospheres, in planets in which density linearly decreases to zero at the surface. This result is shown to hold for all quasi-columnar perturbations. Both the phase speed of the normal mode oscillations and the barotropic stability criterion have features in common with Saturn and Jupiter oscillations.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 65; 370-382
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    Flow field and near and far sound field of a subsonic jet (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Flow and sound field data are presented for a 2.54 cm diameter air jet at a Mach number of 0.50 and a Reynolds number of 300,000. Distributions of mean velocity, turbulence intensities, Reynolds stress, spectral components of turbulence as well as of the near field pressure, together with essential characteristics of the far field sound are reported. This detailed set of data for one particular flow, erstwhile unavailable in the literature, is expected to help promoote and calibrate subsonic jet noise theories. 'Source locations' in terms of the turbulence maxima, coupling between the entrainment dynamics and the near pressure field, the sound radiation paths, and the balance in mass, momentum and sound energy fluxes are discussed. The results suggest that the large scale coherent structures of the jet govern the 'source locations' by controlling the turbulence and also strongly influence the near field pressure fluctuations.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Sound and Vibration (ISSN 0022-460X); 106; 1-16
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    The climate of Mars (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The composition of the primitive Martian atmosphere and its development into the present environment are described. The primitive atmosphere consisted of water vapor, carbon dioxide, and nitrogen released from rocks; the greenhouse effect which maintained the surface temperature above the frost point of water is examined. Volcanic activity reduced the greenhouse effect and along with CO2 removal from the atmosphere caused a lowering of the planet temperature. The global circulation patterns on earth and Mars are compared; the similarities in the circulation patterns and Mars' seasonal variations are studied. The carbon dioxide and water cycles on Mars are analyzed; the carbon dioxide cycle determines seasonal variations in surface pressure and the behavior of the water cycle. The behavior of the atmospheric dust and the relationship between the seasonal dust cycle and Hadley circulation are investigated. The periodic variations in the three orbital parameters of Mars, which affect the climate by changing the seasonal and latitudinal distribution of incoming solar energy are discussed
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Scientific American (ISSN 0036-8733); 254; 54-62
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    Implications of the VEGA balloon results for Venus atmospheric dynamics (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Both VEGA balloons encountered vertical winds with typical velocities of 1 to 2 meters per second. These values are consistent with those estimated from mixing length theory of thermal convection. However, small-scale temperature fluctuations for each balloon were sometimes larger than predicted. The approximate 6.5-kelvin difference in temperature consistently seen between VEGA-1 and VEGA-2 is probably due to synoptic or planetary-scale nonaxisymmetric disturbances that propagate westward with respect to the planet. There is also evidence from Doppler data for the existence of solar-fixed nonaxisymmetric motions that may be thermal tides. Surface topography may influence atmospheric motions experienced by the VEGA-2 balloon.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science (ISSN 0036-8075); 231; 1422-142
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    Overview of VEGA Venus balloon in situ meteorological measurements (1986)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The VEGA balloons made in situ measurements of pressure, temperature, vertical wind velocity, ambient light, frequency of lightning, and cloud particle backscatter. Both balloons encountered highly variable atmospheric conditions, with periods of intense vertical winds occurring sporadically throughout their flights. Downward winds as large as 3.5 meters per second occasionally forced the balloons to descend as much as 2.5 kilometers below their equilibrium float altitudes. Large variations in pressure, temperature, ambient light level, and cloud particle backscatter (VEGA-1 only) correlated well during these excursions, indicating that these properties were strong functions of altitude in those parts of the middle cloud layer sampled by the balloons.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science (ISSN 0036-8075); 231; 1411-141
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    Measurements of reflectance spectra of ion-bombarded ice and application to surfaces in the outer solar system (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The first results of laboratory measurements of the wavelength dependence of the alternation of the visible reflectance of H2O ice irradiated by keV ions are presented. When the implanted species is chemically neutral, absorption is slightly enhanced below 0.55 micron. For an incident species containing sulfur, a strong absorption feature is produced at 0.4 micron, probably corresponding to S3. This occurs at too large a wavelength to account for the absorption feature observed at Europa by Voyager and therefore casts doubt on the recent interpretation of the reflectance data of Europa.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature (ISSN 0028-0836); 333; 240
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    Surficial textures of the Galilean satellites (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The observations of the Galilean satellites of Jupiter obtained with the IUE have been analyzed as a function of solar phase angle. By fitting the measurements to a shadowing model, comparative descriptions of the microtextures of the optically active portion of the surfaces of the satellites are derived. Important differences among the satellites and between leading and trailing hemispheres of individual satellites result from the different processes of meteoritic bombardment, magnetospheric interaction, and geological resurfacing that operate in the Jovian system. Io and Callisto have the most tenuous upper regoliths, whereas the surface of the leading side of Europa is the most compact.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature (ISSN 0028-0836); 333; 148-151
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    Thermal structure of the ionosphere of Mars - Simulations with one- and two-dimensional models (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Heat flux saturation effects are included in the present one- and two-dimensional models of the Martian upper ionosphere's thermal structure. The inclusion of small upper boundary and volume heat sources is found to yield satisfactory simulations of the dayside ion temperature observation results obtained by Viking 1's retarding potential analyzers. It is noted that the plasma flow-transport of heat from the dayside to the nightside makes no contribution to the ion and electron temperatures that have been calculated for the nightside.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 74; 357-364
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    Deformational models of rifting and folding on Venus (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Features of presumed tectonic origin on Venus are reviewed, and lithospheric strength envelopes are derived based on laboratory measurements of the deformational properties of crustal and subcrustal rocks, extrapolated to conditions appropriate to Venus. Models for rifting and folding are developed that use this lithospheric structure and take into account both brittle and ductile yielding as well as finite elastic strength. For both rifting and folding, structures with characteristic widths and spacings are predicted whose size depends on the thickness of the lithosphere, density contrast, and elastic properties of the layer. Finally, the model predictions are compared with the widths and spacings of observed tectonic features, and it is concluded that they are consistent with a relatively strong mantle layer separated from a thin brittle surface layer by a ductile lower crust. These results allow constraints to be placed on the crustal thickness and thermal gradient on Venus.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 93; 4759-477
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    Evolution of a steam atmosphere during earth's accretion (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The evolution of an impact-generated steam atmosphere around an accreting earth is presently modeled under the assumption of Safronov (1978) accretion, in a scheme that encompasses the degassing of planetesimals on impact, thermal blanketing by the steam atmosphere, surface-to-interior water exchange, the shock heating and convective cooling of the earth's interior, and hydrogen escape due both to solar EUV-powered planetary wind and impact erosion. The model yields four distinct classes of impact-generated atmospheres: the first, on which emphasis is placed, has as its salient feature a molten surface that is maintained by the opacity of a massive water vapor atmosphere; the second occurs when the EUV-limited escape exceeds the impact degassing rate, while the third is dominated by impact erosion and the fourth is characterized by an atmosphere more massive than any thus far encountered.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 74; 62-97
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    On the origin of Venus' atmosphere - Possible contributions from simple component mixtures and fractionated solar wind (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: It is suggested that while an origin of the volatiles of the Venus atmosphere as a single, fractionated component derivable from the solar wind can account for Ar, Kr, and Xe relative abundances, it does so only with an excess of C, and perhaps of N. A similarity is noted in relative abundances between Venus volatiles and fractionated solar wind gases in the lunar regolith which implies that such a lunar-type component is a major contributor to Venus' volatiles. A variety of Venus atmosphere models is considered; these fail to explain the low Ne/Ar ratio on Venus.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 74; 3-20
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  • 81
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    Source of the Australasian tektite strewn field - A possible off-shore impact site (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Although there is a preponderance of evidence that tektites were formed by asteroid impacts on the earth, no source crater has been found for the largest and youngest of the strewn fields - the Austalasian strewn field. A combined Seasat/Geos 3 altimeter data set of sea surface heights in the northern portion of the Australasian strewn field has been examined for negative gravity anomalies on the continental shelf and slope which might be related to the source crater for these tektites. A large negative anomaly called the Qui Nhon Slope Anomaly is a sea surface depression of approximately 1.5 meters over an area of 100 km diameter. It corresponds to a gravity anomaly of about -50 mgal. It is proposed that this anomaly may be due to the impact structure that produced the Australasian strewn field.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 15; 357-360
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  • 82
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    The solar wind control of Jupiter's broad-band kilometric radio emission (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Observations of the solar wind close to Jupiter are compared with the broad-band kilometric radio emission (bKOM), using data recorded by Voyager 1 and Voyager 2 during 1979. The lower bKOM frequencies, less than about 300 kHz, are found to correlate with the solar wind density and pressure and with the interplanetary magnetic field (IMF) magnitude during periods when there is a well-defined magnetic sector structure. The results suggest that lower frequency bKOM events are most likely to occur after a sector boundary has passed Jupiter during the period when the solar wind density and the IMF magnitude are increasing towards the sector center. The average bKOM energy per Jovian rotation tends to have lower values soon after the sector center has passed. Higher-frequency/higher-energy bKOM emission may be contaminated by hectometric emission (HOM) and differently correlated with solar activity. The solar wind control may also be obscured by some stronger control. It is suggested that electron density fluctuations in the Io torus, where the source is believed to be located, may be responsible for variations in the beaming and hence variations in the observed emission.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 192; 1-2,; 354-359
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  • 83
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    Large impact basins and the mega-impact origin for the crustal dichotomy on Mars (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The hypothesis that the crustal dichotomy on Mars is due to a single giant (mega) impact early in Martian history is tested by determining the number of 'missing' basins, the difference between the observed number of large impact basins on Mars and the number expected from a 1/D-squared distribution. If the Borealis Basin was the largest member of a 1/D-squared impact population, a large number of 'missing' basins is expected which is too large to be hidden by the younger surface units. If Chryse is the largest member of a 1/D-squared impact population, the more modest number of 'missing' basins could be confined to areas of Mars that have been resurfaced or reworked by subsequent geologic processes.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 15; 229-232
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  • 84
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    Thermal emission from Saturn's rings at 380 microns (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Two different techniques have been used to derive the Saturn disk's ring brightness temperatures from 380-micron observations: (1) comparisons of these wide-beam observation disk-ring system results with those obtained for an earlier epoch, when the rings were edge-on, then differencing the two measurements to obtain a value for the rings' contribution; and (2) ring contribution resolution during scanning along the disk-ring plane, to yield a B-ring brightness temperature of 39 + or - 8 K at 380 microns. The results obtained indicate a gradual decrease of observed ring brightness temperature from the IR to the radio wavelength range.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 574-583
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  • 85
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    Force and pressure study of thick cambered/twisted 58 deg delta wings (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 25; 69-75
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  • 86
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    Progress in analysis and prediction of dynamic stall (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 25; 6-17
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  • 87
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    Superposed ridges of the Hesperia Planum area on Mars (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Mare ridges of the Hesperia Planum area form linear, reticular and circular structures. The main factors effective in mare ridge formation have been: (1) a large areal, or maybe even global, shortening and compression, (2) major crustal tectonics, and (3) the moderation of tectonic movements by the megaregolith discontinuity layer(s) between surface lavas and the bedrock leaving the compressional thrust to dominate over other fault movements in surface tectonics.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Earth, Moon, and Planets (ISSN 0167-9295); 40; 71-99
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  • 88
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    Analysis of Pioneer Venus Orbiter ultraviolet spectrometer Lyman alpha data from near the subsolar region (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Pioneer Venus Orbiter ultraviolet spectrometer data from 20 orbits which span 3 years have been analyzed to determine the atomic hydrogen number density and vertical flux at the exobase as a function of solar zenith angle, F(10.7) index, and spacecraft latitude. From 1979 through 1981, the exobase number density n(c) and flux phi(c) are remarkably constant at n(c) = 6.0 + or - 1.5 x 10 to the 4th/cu cm and phi(e) = 7.5 + or - 1.5 x 10 to the 7th/sq cm per s in the subsolar region. The integrated vertical column density above 110 km is 3.6 + or - 1 x 10 to the 13th/sq cm. An empirical relationship is determined between the line center solar flux at H Lyman alpha, piF(0), and the F(10.7) index.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 93; 1766-177
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  • 89
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    Voyager at Uranus (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The findings made in the Voyager flyby past Uranus are reviewed. The spacecraft is described, and the preparations for the Uranus encounter are recalled. The encounter characteristics are presented, and the characteristics of the Uranian atmosphere and interior, magnetic field, rings, and satellites are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: (ISSN 0007-084X); 41; 49-62
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  • 90
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    Neptune radio emission - Predictions based on planetary scaling laws (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: In this paper a prediction is advanced concerning Neptune's low-frequency radio emission based on the radiometric Bode's law for radio planets in combination with the magnetostrophic scaling law for magnetized planets. The total emitted radio power is predicted to be about 1.6 x 10 to the 7th W, very nearly the same as that predicted and observed for Uranus. Possible emission spectral shapes, based on Saturn and earth-like models, are shown. Using these models, the radio emission frequency range is predicted to extend from approximately 100 to just over 1000 kHz, with a spectral peak between 350 and 500 kHz. If radiation is beamed approximately in the sunward direction, Neptune should be detectable by the planetary radio astronomy experiment onboard the Voyager spacecraft sometime between 45 and 90 days before closest approach. This detection is likely to represent the first direct evidence of a Neptune magnetic field. Possible implications for Neptune's magnetosphere with regard to the time of first detection are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 15; 114-1117
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  • 91
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    Atmospheres and ionospheres of the outer planets and their satellites (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Essential aspects of physical and chemical processes in the atmospheres and ionospheres of the outer planets are examined in an introductory overview of current knowledge, intended both for graduate students of planetary science and for practicing scientists. Chapters are devoted to bulk atmospheric compositions, thermal structures, cloud structures, vertical mixing, photochemistry, the ionospheres, and the satellites. Measurement data are compiled in tables, and extensive graphs and diagrams are provided.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 92
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    Multitasking the code ARC3D (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The CRAY multitasking system was developed in order to utilize all four processors and sharply reduce the wall clock run time. This paper describes the techniques used to modify the computational fluid dynamics code ARC3D for this run and analyzes the achieved speedup. The ARC3D code solves either the Euler or thin-layer N-S equations using an implicit approximate factorization scheme. Results indicate that multitask processing can be used to achieve wall clock speedup factors of over three times, depending on the nature of the program code being used. Multitasking appears to be particularly advantageous for large-memory problems running on multiple CPU computers.
    Schlagwort(e): AERODYNAMICS
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  • 93
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    Mass fractionation during transonic escape and implications for loss of water from Mars and Venus (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Hydrodynamic escape of hydrogen from a planetary atmosphere can remove heavier gases as well as hydrogen, provided that the escape rate is sufficiently large. Analytic approximations for the degree of mass fractionation of a trace species during hydrodynamic escape are compared with accurate numerical solutions for the case of transonic outflow. The analytic approximations are most accurate when the ratio of molecular weights of the heavier and lighter constituents is large so that nonlinear terms in the momentum equation for the heavy constituent become small. The simplest analytic formula is readily generalized to the case where a heavy constituent is also a major species. Application of the generalized formula to hypothetical episodes of hydrodynamic escape from Venus and Mars suggests that both hydrogen and oxygen could have escaped; thus, substantial quantities of water may have been lost without the need to oxidize large amounts of the crust.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 68; 462-480
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  • 94
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    Europa (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Europa, the second major satellite outward from Jupiter, is a lunar-sized object in synchronous rotation about that planet. Its high albedo and spectral characteristics indicate the presence of surface water ice and/or frost. Its density suggests a substantial silicate component of at least 85 percent by volume. A limited variety of landforms is seen in Voyager images, most likely because of poor spatial resolution of these data. The absence of numerous impact craters is interpreted as indicating a youthful surface and /or surface regenerating processes. A planet-wide lineament system has been interpreted to result from tectonic stresses induced by evolution of Europa's orbit and interior. Present data do not permit unambiguous tests of such interpretations. Greater insight may come from analytical or numerical models and future spacecraft observations.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 95
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    Cratering of planetary satellites (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Recent findings concerning craters and cratering populations on the satellites of Jupiter and Saturn are discussed. Current understanding of cratering mechanics is reviewed with emphasis placed on scaling and ejecta and the differences between cratering in rock and ice. Evidence from crater statistics regarding cratering histories on various planetary satellites is discussed and connections are made with what is known about the cratering record on the terrestrial bodies. Consideration is given to the source populations and an attempt is made to summarize and critique the various scenarios that have been proposed for linking the cratering records on the various planets and satellites. It is noted that early Voyager Uranus results seem compatible with the present summary.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 96
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    The Jovian magnetotail (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The current understanding of the plasma, magnetic field, and plasma wave characteristics of the near and distant Jovian magnetotail is discussed. The properties of these two regions are compared, with particular emphasis given to the data on the distant tail obtained by Voyager 2. The Jovian tail has many unusual properties, such as the large scale sausage-string shape of its outer boundary, but some of its properties resemble those of the earth's magnetotail, such as its central current sheet and a surrounding region resembling a plasma sheet consisting of hot ions. Data are presented that support the view that plasma in the Jovian tail plasma sheet comes from Jupiter.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Advances in Space Research (ISSN 0273-1177); 6; 1, 19
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  • 97
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    Supersonic full-potential method applied to missile bodies (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The NCOREL full-potential method with an entropy correction is presently applied to supersonic missile flowfield problems. After defining the salient characteristics of the method, a combination of linear theory with NCOREL and experimental data is used to isolate the nonlinear features of the supersonic flow so that the influence of geometry and flow conditions on the development of such flow nonlinearities can be appreciated. Comparisons of experimental longitudinal force and moment data with NCOREL and various linear theory predictions are presented for several generic missile airframe configurations of circular and elliptic cross section. The NCOREL code solves the nonconservative full potential equation in a spherical coordinate system; exact boundary conditions are defined on the missile surface.
    Schlagwort(e): AERODYNAMICS
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  • 98
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    Low aspect ratio wings at high angles of attack (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A comprehensive evaluation is made of experimental data compiled to date for the flowfields and aerodynamic forces that occur at high angles of attack for low aspect ratio wings with delta, rectangular, clipped delta, and strake/wing planform geometries. Attention is given to wing leading edge-generated vortex breakdown, aspect ratio and compressibility effects, and strake vortex effects on main wing areas. Although the nonlinear effects created by a wing-body combination significantly alter wing-alone aerodynamics, the wing-alone data presented are vital to the development of prediction methodologies for large angle of attack aerodynamics.
    Schlagwort(e): AERODYNAMICS
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  • 99
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    Radar glory from buried craters on icy moons (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Three ice-covered moons of Jupiter, in comparison with rocky planets and earth's moon, produce radar echoes of astounding strengths and bizarre polarizations. Scattering from buried craters can explain these and other anomalous properties of the echoes. The role of such craters is analogous to that of the water droplets that create the apparition known as 'the glory', the optically bright region surrounding an observer's shadow on a cloud. Both situations involve the electromagnetic phenomenon of total internal reflection at a dielectric interface, operating in a geometry that strongly favors exact backscattering. Dim surface craters are transformed into bright glory holes by being buried under somewhat denser material, thereby increasing the intensity of their echoes by factors of hundreds. The dielectric interface thus formed at the crater walls nicely accounts for the unusual polarizations of the echoes.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science (ISSN 0036-8075); 234; 587-590
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  • 100
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    Rotor wake characteristics of a transonic axial-flow fan (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 24; 1802-181
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