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  • 1
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    Gravitational acceleration as a cue for absolute size and distance? (1996)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: When an object's motion is influenced by gravity, as in the rise and fall of a thrown ball, the vertical component of acceleration is roughly constant at 9.8 m/sec2. In principle, an observer could use this information to estimate the absolute size and distance of the object (Saxberg, 1987a; Watson, Banks, von Hofsten, & Royden, 1992). In five experiments, we examined people's ability to utilize the size and distance information provided by gravitational acceleration. Observers viewed computer simulations of an object rising and falling on a trajectory aligned with the gravitational vector. The simulated objects were balls of different diameters presented across a wide range of simulated distances. Observers were asked to identify the ball that was presented and to estimate its distance. The results showed that observers were much more sensitive to average velocity than to the gravitational acceleration pattern. Likewise, verticality of the motion and visibility of the trajectory's apex had negligible effects on the accuracy of size and distance judgments.
    Keywords: Life Sciences (General)
    Type: Perception & psychophysics (ISSN 0031-5117); Volume 58; 7; 1066-75
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  • 2
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    Of red planets and indigo computers: Mars database visualization as an example of platform downsizing (1997)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The last decade has witnessed tremendous advancements in the computer hardware and software used to perform scientific visualization. In this paper, we consider how the visualization of a particular data set, the digital terrain model derived from the Viking orbiter imagery, has been realized in four distinct projects over this period. These examples serve to demonstrate how the vast improvements in computational performance both decrease the cost of such visualization efforts and permit an increasing level of interactivity. We then consider how even today's graphical systems require the visualization designer to make intelligent choices and tradeoffs in database rendering. Finally, we discuss how insights gleaned from an understanding of human visual perception can guide these design decisions, and suggest new options for visualization hardware and software.
    Keywords: Life Sciences (General)
    Type: Behavior research methods, instruments, & computers : a journal of the Psychonomic Society, Inc (ISSN 0743-3808); Volume 29; 1; 48-53
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  • 3
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    Asymmetries in the Io plasma torus (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Using Ulysses radio wave data taken during the 1992 Jupiter encounter, we conclude that there are significant large and small spatial scale azimuthal asymmetries at high latitudes in the Io plasma torus. During a period of time near perijove when the spacecraft motion was predominantly in the azimuthal direction and was relatively fixed in both latitude and radial distance, inferred electron densities depart significantly from the common assumption of longitudinal symmetry. Specifically, electron plasma concentrations near 0 deg system III longitude (and 0400 LT) are greater than those near 180 deg (and 0000 LT). Superposed on this large-scale variation are regularly spaced density depletions, 30-50% in magnitude, and having a spatial periodicity of about 17 deg. Some of these depletions may drive various known radio and plasma wave sources by means of large B parallel electric potentials. The observations are compared with recent models and with the in-situ Voyager observations.
    Keywords: ASTRONOMY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A9; p. 17,205-17,210
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  • 4
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    Ulysses observations of auroral hiss at high Jovian latitudes (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: During the Ulysses flyby of Jupiter, a whistler-mode emission was periodically detected by the unified Radio and Plasma wave (URAP) experiment during intervals when the spacecraft extended to high magnetic latitudes. The signal was detected between the local electron plasma frequency and lower hybrid resonance and appears as a funnel-shaped structure on frequency-versus-time spectrograms; these characteristics are very reminiscent of whistler-mode auroral hiss observed at high latitudes at Earth. Ray tracing of the emission occurrences suggests the emission source is on magnetic field lines extending out to at least 65 R(sub J). This location associates the emission with the boundary between open and closed field lines -- not the Io torus. The emission radiates about 10(exp 7) W of power. Consequently, the auroral input power derived from the solar wind to drive the emission is believed to be 10(exp 10-12) W (or about 1% of the energy associated with Io torus electrical processes).
    Keywords: SPACE SCIENCES (GENERAL)
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 20; p. 2259-2262
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  • 5
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    Possible radio wave precursors associated with the comet Shoemaker-Levy 9/Jupiter impacts (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We suggest that prior to its impact with Jupiter, comet Shoemaker-Levy 9 will behave as an electrical generator in the Jovian magnetosphere, converting planetary rotational energy to electrical energy via a dust/plasma interaction. This electrical energy will then be deposited in the dayside auroral region where it may drive various auroral phenomena including cyclotron radio emission. Such emission could be detected by spacecraft like Ulysses and Galileo many hours prior to the actual comet impact with the upper atmosphere. We apply the theory originally developed to explain the spokes in Saturn's rings. This theory allows us to quantify the driving potential associated with the comet and, consequently, to determine the radio power created in the auroral region. We conclude that if enough fine dust is present in the cometary system, comet-induced auroral radio emissions will reach detectable levels. This emission should be observable in the dayside hemisphere about 12-24 hours prior to each fragment impact.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 11; p. 1067-1070
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  • 6
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    Elliptically polarized bursty radio emissions from Jupiter (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We report a new component of Jovian radio emission observed by the Ulysses spacecraft when Ulysses was at high Jovigraphic latitudes (greater than or approximately = 30 deg north or south of the Jovian magnetic equator). This bursty high-latitude emission is elliptically polarized in the right-hand sense when observed from northern latitudes and in the left-hand sense when observed from southern latitudes, consistent with extraordinary mode. The orientation of the polarization ellipse is observed to systematically vary with time relative to the observer. It is argued that the elliptically-polarized nature of the emission is intrinsic to the source region.
    Keywords: ASTRONOMY
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 4; p. 345-348
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  • 7
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    Source characteristics of Jovian narrow-band kilometric radio emissions (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: New observations of Jovian narrow-band kilometric (nKOM) radio emissions were made by the Unified Radio and Plasma Wave (URAP) experiment on the Ulysses spacecraft during the Ulysses-Jupiter encounter in early February 1992. These observations have demonstrated the unique capability of the URAP instrument for determining both the direction and polarization of nKOM radio sources. An important result is the discovery that nKOM radio emission originates from a number of distinct sources located at different Jovian longitudes and at the inner and outermost regions of the Io plasma torus. These sources have been tracked for several Jovian rotations, yielding their corotational lags, their spatial and temporal evolution, and their radiation characteristics at both low latitudes far from Jupiter and at high latitudes near the planet. Both right-hand and left-hand circularly polarized nKOM sources were observed. The polarizations observed for sources in the outermost regions of the torus seem to favor extraordinary mode emission.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; E7; p. 13,163-13,176.
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  • 8
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    Ulysses observations of escaping VLF emissions from Jupiter (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The Ulysses URAP experiment has detected Jovian radio emissions in the VLF range at distances from Jupiter in excess of 1.5 AU. The URAP observations represent the first synoptic observations of Jupiter in the VLF band, from 3 to 30 kHz. In this band lie the low-frequency extent of the bKOM emission, the escaping continuum emission, and the Jovian type IIIs. Initial results indicate that the continuum varies in frequency with the solar wind ram pressure at Jupiter, whereas, the Jovian type IIIs appear to be controlled to some extent by the planetary rotation, often appearing when system III longitude 100 deg faces the spacecraft.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 19; 649-652
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  • 9
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    In ecliptic observations of Jovian radio emissions by Ulysses - Comparison with Voyager results (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: During the Ulysses inbound cruise to Jupiter the Unified Radio and Plasma Wave (URAP) experiment observed a variety of the planet's radio components in the frequency range below 1 MHz. Most of these emissions were already detected by the Voyager Radio Astronomy and Plasma Wave experiments, however, with much less sensitivity and different spectral coverage. These different radio components within the URAP dynamic spectra are identified, and their appearance with the previous Voyager observations are compared.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 19; 12, J; 1307-131
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  • 10
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    Phenomenology of Neptune's radio emissions observed by the Voyager planetary radio astronomy experiment (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The Neptune flyby in 1989 added a new planet to the known number of magnetized planets generating nonthermal radio emissions. We review the Neptunian radio emission morphology as observed by the planetary radio astronomy experiment on board Voyager 2 during a few weeks before and after closest approach. We present the characteristics of the two observed recurrent main components of the Neptunian kilometric radiation, i.e., the 'smooth' and the 'bursty' emissions, and we describe the many specific features of the radio spectrum during closest approach.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 97; A12; p. 19,201-19,211.
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