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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 91 records · Page 5
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NASA NTRS1989

The UV spectrum of Pluto-Charon - IUE observations from 2600 to 3100 A

Observations of the UV spectra of the Pluto-Charon system were obtained between 1987 and 1988 using the large aperture of the IUE long-wavelength prime spectrograph. At the resolution and SNR of the data, no gas-phase spectral identifications were made. The present data indicate a geometric albedo of 0.35 + or - 0.05. Curve fitting the geometric albedo from 2600-3100 A, a blue slope is found which corresponds to a decrease of about 12 percent per 1000 A. An albedo reversal or trough between about 3000 A and the shortest ground-based data (at about 3500 A) is noted which may be due to a spectral absorption feature on the surface.

Stern, S. Alan↗
NASA NTRS1990

Pushing back the frontier - A mission to the Pluto-Charon system

A flyby mission to Pluto is proposed. The size, orbit, atmosphere, and surface of Pluto, and the Pluto-Charon system are described. The benefits of a planetary flyby compared to ground observations are discussed in terms of imaging capabilities. Planned payloads include a plasma science package, a UV spectrometer, and a thermal mapper. The advantages of a dual launch to Mars and the need for a Jupiter-Pluto transfer are considered. A diagram of a spacecraft for a flyby study of Pluto is provided.

Farquhar, Robert↗
NASA NTRS1991

Pluto-Charon stellar occultation candidates - 1990-1995

A search to identify stars that might be occulted by Pluto or Charon during the period 1990-1995 and part of 1996 is studied. This search was made with an unfiltered CCD camera operated in the strip scanning mode, and it reaches an R magnitude of approximately 17.5 - about 1.5 mag fainter than previous searches. Circumstances for each of the 162 potential occultations are given, including an approximate R magnitude of the star, which allows estimation of the signal-to-noise ratio (S/N) for observation of each occultation. The faintest stars in the list would yield an S/N of about 20 for a 1 s integration when observed with a CCD detector on an 8 m telescope under a dark sky. The astrometric precision (+/- 0.2 arcsec, with larger systematic errors possible for individual cases) is insufficient to serve as a final prediction for these potential occultations, but is sufficient to identify stars deserving of further, more accurate, astrometric observations. Statistically, about 32 of these events to be observable somewhere on earth are expected. The number of events actually observed will be substantially smaller because of clouds and the sparse distribution of large telescopes. Finder charts for each of the 91 stars involved are presented.

Dunham, E. W.↗
NASA NTRS1991

Studies of Triton and the Pluto-Charon system

The project is designed to take advantage of the six-year-long series of mutual occultation and eclipse events involving Pluto and its satellite Charon during one of its rare edge-on orbital alignments. High-precision, high-time-resolution photometry of these events can be utilized to extract several important physical parameters. An important derived parameter is the mean density of the system, which constrains the bulk composition of two bodies.

Tholen, David J.↗
NASA NTRS1991

Pluto-Charon Stellar Occultation Candidates: 1990-1995

We have carried out a search to identify stars that might be occulted by Pluto or Charon during the period 1990-1995 and part of 1996. This search was made with an unfiltered CCD camera operated in the strip scanning mode, and it reaches an R magnitude of approximately 17.5-about 1.5 mag fainter than previous searches. Circumstances for each of the 162 potential occultations are given, including an approximate R magnitude of the star, which allows estimation of the signal-to-noise ratio (S/N) for observation of each occultation. The faintest stars in our list would yield an S/N of about 20 for a 1 S integration when observed with a CCD detector on an 8 m telescope under a dark sky. Our astrometric precision (+/- 0.2 arcsec, with larger systematic errors possible for individual cases) is insufficient to serve as a final prediction for these potential occultations, but is sufficient to identify stars deserving of further, more accurate, astrometric observations. Statistically, we expect about 32 of these events to be observable somewhere on Earth. The number of events actually observed will be substantially smaller because of clouds and the sparse distribution of large telescopes. Finder charts for each of the 91 stars involved are presented.

Dunham, E. W.↗
NASA NTRS1995

Modeling Pluto-Charon Mutual Events: CCD Observations with the 60 in. Telescope at Palomar Mountain - 2

We present observations of 15 Pluto-Charon mutual events which were obtained with the 60 in. telescope at Palomar Mountain Observatory. A CCD camera and Johnson V filter were used for the observations, except for one event that was observed with a Johnson B filter, and another event that was observed with a Gunn R filter. We observed two events in their entirety, and three pairs of complementary mutual occultation-transit events.

Buratti, B. J.↗
NASA NTRS2002

Stellar Occultation Studies of Pluto, Triton, Charon, and Chiron

Bodies inhabiting the outer solar system are of interest because, due to the colder conditions, they exhibit unique physical processes. Also, some of the lessons learned from them can be applied to understanding what occurred in the outer solar system during its formation and early evolution. The thin atmospheres of Pluto and Triton have structure that is not yet understood, and they have been predicted to undergo cataclysmic seasonal changes. Charon may have an atmosphere - we don't know. Chiron exhibits cometary activity so far from the sun (much further than most comets), so that H2O sublimation cannot be the driving mechanism. Probing these bodies from Earth with a spatial resolution of a few kilometers can be accomplished only with the stellar occultation technique. In this program we find and predict stellar occultation events by small outer-solar system bodies and then attempt observations of the ones that can potentially answer interesting questions. We also develop new methods of data analysis for occultations and secure other observations that are necessary for interpretation of the occultation data.

Elliot, James L.↗
NASA NTRS1997

Charon Toolkit for Parallel, Implicit Structured-Grid Computations: Functional Design

Charon is a software toolkit that enables engineers to develop high-performing message-passing programs in a convenient and piecemeal fashion. Emphasis is on rapid program development and prototyping. In this report a detailed description of the functional design of the toolkit is presented. It is illustrated by the stepwise parallelization of two representative code examples.

VanderWijngaart, Rob F.↗
NASA NTRS2004

Observations of the Pluto-Charon System

We are continuing the analysis of adaptive optics observations of the Pluto-Charon system, with the goal of confirming the orbital eccentricity reported by Tholen and Bule (1997). Previous work on these data, obtained with the Hokupa's adaptive optics system and Gemini North and reported by Tholea (2002), utilized only a portion of the full set of 348 images taken on 8 nights between 2001 and 2002, and was based on a preliminary calibration of the image scale and position angle of the detector. For each of the three observing runs, independent calibrations were performed using the motion of an asteroid past a fixed stellar source to remove any minor differences in the way the instrument was mounted on the telescope for each run. The image scales determined for each run are good to better than 1 part in 1000, while the individual position angle determinations are good at least 0.1 deg. The preliminary analysis reported at last year's DPS meeting indicated consistency with the orbit determined from the HST observations acquired a decade ago, however, a more careful analysis yields a longitude of periapsis of 132.2 degrees plus or minus 9.3 degrees, disagreeing with the HST results: Finally, possible explanation for the differences in orbital solutions are considered.

Tholen, David J.↗
NASA NTRS2016

Charon's Light Curves, as Observed by New Horizons' Ralph Color Camera (MVIC) on Approach to the Pluto System.

Light curves produced from color observations taken during New Horizons approach to the Pluto-system by its Multi-spectral Visible Imaging Camera (MVIC, part of the Ralph instrument) are analyzed. Fifty seven observations were analyzed, they were obtained between 9th April and 3rd July 2015, at a phase angle of 14.5 degrees to 15.1 degrees, sub-observer latitude of 51.2 degrees North to 51.5 degrees North, and a sub-solar latitude of 41.2 degrees North. MVIC has four color channels; all are discussed for completeness but only two were found to produce reliable light curves: Blue (400-550 nm) and Red (540-700 nm). The other two channels, Near Infrared (780-975 nm) and Methane-Band (860-910 nm), were found to be potentially erroneous and too noisy respectively. The Blue and Red light curves show that Charon's surface is neutral in color, but slightly brighter on its Pluto-facing hemisphere. This is consistent with previous studies made with the Johnson B and V bands, which are at shorter wavelengths than that of the MVIC Blue and Red channel respectively.

Howett, C. J. A.↗
NASA NTRS2016

Surface Compositions Across Pluto and Charon

The Kuiper Belt hosts a swarm of distant, icy objects ranging in size from small, primordial planetesimals to much larger, highly evolved objects, representing a whole new class of previously unexplored cryogenic worlds. Pluto, the largest among them, along with its system of five satellites, has been revealed by NASAs New Horizons spacecraft flight through the system in July 2015, nearly a decade after its launch.

Grundy, W. M.↗
NASA NTRS1997

Determination of the Charon/Pluto Mass Ratio from Center-of-Light Astrometry

The Charon/Pluto mass ratio is a fundamental but poorly known parameter of the two-body system. Previous values for the mass ratio have ranged from 0.0837 plus or minus 0.0147 (Null et al., 1993, Astron. J. 105, 2319-2335) to 0.1566 plus or minus 0.0035 (Young et al., 1994, Icarus 108,186-199). We report here a new determination of the Charon/Pluto mass ratio, using five sets of groundbased images taken at four sites in support of Pluto occultation predictions. Unlike the Null et al. and Young et A determinations, where the centers of light for Pluto and Charon could be determined separately, this technique examines the motion of the center of light of the blended Pluto-Charon image. We compute the offsets of the observed center-of-light position of Pluto-Charon from the ephemeris position of the system and fit these offsets to a model of the Pluto-Charon system. The least-squares fits to the five data sets agree within their errors, and the weighted mean mass ratio is 0.117 plus or minus 0.006. The effects of errors in the Charon light fraction, semimajor axis, and ephemeris have been examined and are equal to only a small fraction of the formal error from the fit. This result is intermediate between those of Null et al., and Young et al. and matches a new value of 0.124 plus or minus 0.008 by Null and Owen (1996, Astron. J. 111, 1368-1381). The mass ratio and resulting individual masses and densities of Pluto and Charon are consistent with a collisional origin for the Pluto-Charon system.

Foust, Jeffrey A.↗