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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Photometry of Pluto-Charon mutual events and Hirayama family asteroids

During 1985 to 1990, nature provided earth bound astronomers with a once-per-century opportunity to observe occultation and transit phenomena between Pluto and its satellite, Charon. Ground based observations of these events are now being used to derive physical parameters for the Pluto-Charon system to a precision that is unlikely to be improved upon until in situ spacecraft observations are obtained. This program supports analysis of photometry observations from McDonald Observatory, a critical location in the International Pluto Campaign network. Knowledge of the diameters, masses, densities, and compositions derived from these observations will augment the understanding of Pluto's origin and its context within the problem of solar system formation.

Binzel, Richard P.↗
NASA NTRS1992

Albedo maps of Pluto and Charon - Initial mutual event results

By applying the technique of maximum entropy image reconstruction to invert observed lightcurves, surface maps of single-scattering albedo are obtained for the surfaces of Pluto and Charon from 1954 to 1986. The albedo features of the surface of Pluto are similar to those of the Buie and Tholen (1989) spot model maps; a south polar cap is evident. The map of Charon is somewhat darker, with single-scattering albedos as low as 0.03.

Buie, Marc W.↗
NASA NTRS1993

Comparative mapping of Pluto's sub-Charon hemisphere - Three least squares models based on mutual event lightcurves

Observations of Charon transits are used here to derive preliminary maps of Pluto's sub-Charon hemisphere. Three models are used to describe the brightness of Pluto's surface as functions of latitude and longitude. Mapping results are presented using spherical harmonic functions, polynomial functions, and finite elements. A smoothing algorithm applied to the maps is described and the validity and resolution of the maps is tested by reconstruction from synthetic data. A preliminary finding from the maps is that the south polar region has the highest albedo of any location on the planet.

Young, Eliot F.↗
NASA NTRS1994

High-resolution imaging of the Pluto-Charon system with the Faint Object Camera of the Hubble Space Telescope

Images of the Pluto-Charon system were obtained with the Faint Object Camera (FOC) of the Hubble Space Telescope (HST) after the refurbishment of the telescope. The images are of superb quality, allowing the determination of radii, fluxes, and albedos. Attempts were made to improve the resolution of the already diffraction limited images by image restoration. These yielded indications of surface albedo distributions qualitatively consistent with models derived from observations of Pluto-Charon mutual eclipses.

Albrecht, R.↗
NASA NTRS1994

The impactor flux in the Pluto-Charon system

Current impact rates of comets on Pluto and Charon are estimated. It is shown that the dominant sources of impactors are comets from the Kuiper belt and the inner Oort cloud, each of whose perihelion distribution extends across Pluto's orbit. In contrast, long-period comets from the outer Oort cloud are a negligible source of impactors. The total predicted number of craters is not sufficient to saturate the surface areas of either Pluto of Charon over the age of the Solar System. However, heavy cratering may have occurred early in the Solar System's history during clearing of planetesimals from the outer planets' zone.

Weissman, Paul R.↗
NASA NTRS1995

The Surface Compositions of Triton, Pluto, and Charon

Neptune's satellite Triton, and the planet-satellite binary Pluto and Charon, are the most distant planetary bodies on which ices have been directly detected. Triton and Pluto have very similar dimensions and mean densities, suggesting a similar or common origin. Through earth-based spectroscopic observations in the near-infrared, solid N2, CH4, and CO have been found on both bodies, with the additional molecule C02 on Triton. N2 dominates both surfaces, although the coverage is not spatially uniform. On Triton, the CH4 and CO are mostly or entirely frozen in the N2 matrix, while CO2 may be spatially segregated. On Pluto, some CH4 and the CO are frozen in the N2 matrix, but there is evidence for additional CH4 in a pure state, perhaps lying as a lag deposit on a subsurface layer of N2. Despite their compositional and dimensional similarities, Pluto and Triton are quite different from one another in detail. Additional hydrocarbons and other volatile ices have been sought spectroscopically but not yet have been detected. The only molecule identified on Pluto's satellite Charon is solid H2O, but the spectroscopic data are of low precision and admit the presence of other ices such as CH4.

Cruikshank, Dale P.↗
NASA NTRS2000

Charon Message-Passing Toolkit for Scientific Computations

Charon is a library, callable from C and Fortran, that aids the conversion of structured-grid legacy codes-such as those used in the numerical computation of fluid flows-into parallel, high- performance codes. Key are functions that define distributed arrays, that map between distributed and non-distributed arrays, and that allow easy specification of common communications on structured grids. The library is based on the widely accepted MPI message passing standard. We present an overview of the functionality of Charon, and some representative results.

VanderWijngaart, Rob F.↗
NASA NTRS2015

Geology of Pluto and Charon Overview

Pluto's surface was found to be remarkably diverse in terms of its range of landforms, terrain ages, and inferred geological processes. There is a latitudinal zonation of albedo. The conspicuous bright albedo heart-shaped feature informally named Tombaugh Regio is comprised of several terrain types. Most striking is Texas-sized Sputnik Planum, which is apparently level, has no observable craters, and is divided by polygons and ovoids bounded by shallow troughs. Small smooth hills are seen in some of the polygon-bounding troughs. These hills could either be extruded or exposed by erosion. Sputnik Planum polygon/ovoid formation hypotheses range from convection to contraction, but convection is currently favored. There is evidence of flow of plains material around obstacles. Mountains, especially those seen south of Sputnik Planum, exhibit too much relief to be made of CH4, CO, or N2, and thus are probably composed of H2O-ice basement material. The north contact of Sputnik Planum abuts a scarp, above which is heavily modified cratered terrain. Pluto's large moon Charon is generally heavily to moderately cratered. There is a mysterious structure in the arctic. Charon's surface is crossed by an extensive system of rift faults and graben. Some regions are smoother and less cratered, reminiscent of lunar maria. On such a plain are large isolated block mountains surrounded by moats. At this conference we will present highlights of the latest observations and analysis. This work was supported by NASA's New Horizons project

Sputnik Planum↗
NASA NTRS2016

Hemispherical Pluto and Charon Color Composition From New Horizons

New Horizons flew by Pluto and its moons on July 14, 2015 [1]. In the days prior to the closest approach (C/A), panchromatic and color observations of Pluto and Charon were made covering a fully complete range of longitudes. Although only a fraction of this "late-approach" data series has been transmitted to the ground, the results indicate Pluto's latitudinal coloring trends seen on the encounter hemisphere continues on the far side. Charon's red pole is visible from a multitude of longitudes and its colors are uniform with longitude at lower latitudes.

Pluto↗
NASA NTRS1993

Masses and Densities of Pluto and Charon

We have analyzed Hubble Space Telescope Wide Field Camera CCD images of Pluto, Charon, and a background star, obtained on seven HST visits over a 3.2 day span in August 1991, to observe Pluto's barycentric motion and to determine the individual masses and bulk densities of Pluto and Charon.

Charon/Pluto↗
NASA NTRS1983

A charge-coupled device observation of Charon

Images of Pluto which were obtained with a charge-coupled device (CCD) detector show an elongation caused by its satellite, Charon. Analysis of these images separates the planet and satellite components, and yields a Pluto/Charon brightness ratio of 5.5.

Reitsema, H. J.↗
NASA NTRS1985

Pluto-Charon mutual event predictions for 1986

Circumstances are tabulated for 81-Pluto-Charon mutual events occurring during the 1986 opposition. The deepest and longest events will occur in February and reach a depth of about 0.15 mag. Observations of these events will lead to an accurate determination of the satellite's orbit, the diameters of the two bodies, the mean density of the system, and crude albedo maps of one hemisphere on each object.

Tholen, D. J.↗
NASA NTRS1986

Modeling Pluto-Charon mutual eclipse events. I - First-order models

The present 'first order' analytical and numerical models of light curves due to mutual events between close planetary binaries, the effects of shadowing are included. Attention is given to the case of the Pluto-Charon system. The results of the analytical and numerical approaches agree to well within the expected light curve measurement error. The model predicts that the current mutual eclipse event series will end by November 1990.

Dunbar, R. Scott↗
NASA NTRS1987

Circumstances for Pluto-Charon mutual events in 1988

Physical parameters are tabulated for 89 Pluto-Charon mutual events occurring during the 1988 opposition. A primary star and a check star have been selected as comparison stars for events occurring prior to the 1988 opposition. Standardization of the comparison star 1987 Primary has provided a B magnitude of 12.3093 + or - 0.0013 and a V magnitude of 11.4215 + or - 0.0013. The designations, positions, and preliminary magnitudes and colors are also given for two transformation stars selected in order to aid in determination of the color terms necessary to convert the instrumental magnitudes of observers to the standard system.

Tholen, David J.↗
NASA NTRS1988

No effect of diffraction on Pluto-Charon mutual events

Mulholland and Gustafson (1987) made the interesting suggestion that observations of Pluto-Charon mutual events might show significant dependence on both wavelength and telescope aperture because of diffraction effects. In this letter, observations are presented that show the predicted effects to be absent and demonstrate that the parameters of the system are such that the events can be accurately analyzed with geometrical optics.

Tholen, D. J.↗
NASA NTRS1988

Circumstances for Pluto-Charon mutual events in 1989

Circumstances for 90 Pluto-Charon mutual events occurring during the 1989 opposition are presented. It is found that the deepest and longest events will occur near postopposition quadrature in early August. Two new stars are selected as comparison stars for events occurring before opposition in 1989, and it is noted that the 1988 comparison stars should be used for events occurring after opposition.

Tholen, David J.↗
NASA NTRS1989

Orbital elements of Charon from speckle interferometry

The semimajor axis and the inclination are the two most important quantities presently determined from 56 well-calibrated speckle-interferometric observations of the position of Charon, which are presented in conjunction with an orbit solution that incorporates them. Both values in the best solution obtained are noted to significantly differ from earlier determinations. The new value for the semimajor axis represents a 2.7 percent increase over the previously accepted value; the mean density of the system, however, remains unaltered.

Beletic, J. W.↗