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R A Jacobson - One of the best experts on this subject based on the ideXlab platform.
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the orbits of the Uranian Satellites and rings the gravity field of the Uranian system and the orientation of the pole of uranus
The Astronomical Journal, 2014Co-Authors: R A JacobsonAbstract:French et al. determined the orbits of the Uranian rings, the orientation of the pole of Uranus, and the gravity harmonics of Uranus from Earth-based and Voyager ring occultations. Jacobson et al. determined the orbits of the Uranian Satellites and the masses of Uranus and its Satellites from Earth-based astrometry and observations acquired with the Voyager 2 spacecraft; they used the gravity harmonics and pole from French et al. Jacobson & Rush reconstructed the Voyager 2 trajectory and redetermined the Uranian system gravity parameters, satellite orbits, and ring orbits in a combined analysis of the data used previously augmented with additional Earth-based astrometry. Here we report on an extension of that work that incorporates additional astrometry and ring occultations together with improved data processing techniques.
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the orbits of the inner Uranian Satellites from hubble space telescope and voyager 2 observations
The Astronomical Journal, 1998Co-Authors: R A JacobsonAbstract:This article presents revised orbital elements for the 10 small Uranian Satellites discovered by the Voyager 2 spacecraft. The elements have been determined from a fit to astrometric observations made with the Hubble Space Telescope and imaging data acquired by Voyager 2. An assessment of the accuracy of the orbits represented by the elements is provided, as are comparisons with orbits found by previous investigators.
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astrographic observations of the major Uranian Satellites from voyager 2
Astronomy & Astrophysics Supplement Series, 1992Co-Authors: R A JacobsonAbstract:This article provides the reduced astrographic observations of the major Uranian Satellites derived from star-satellite imaging data acquired by the Voyager 2 spacecraft. The data set contains 445 sets of spacecraft-centered right ascension and declination observations and includes all of the observations used in Voyager encounter operations. The conversion process from imaging to astrographic observations was identical to that used for the Neptunian Satellites (Jacobson 1991). The effect of using the astrographic rather than imaging form in ephemeris improvement is evaluated.
Bonnie J Buratti - One of the best experts on this subject based on the ideXlab platform.
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the science case for spacecraft exploration of the Uranian Satellites candidate ocean worlds in an ice giant system
arXiv: Earth and Planetary Astrophysics, 2021Co-Authors: Richard Cartwright, Bonnie J Buratti, Chloe B Beddingfield, Tom Nordheim, C M Elder, A M Bramson, M M Sori, Marc Neveu, Julie Castillorogez, R T PappalardoAbstract:The 27 Satellites of Uranus are enigmatic, with dark surfaces coated by material that could be rich in organics. Voyager 2 imaged the southern hemispheres of Uranus' five largest 'classical' moons Miranda, Ariel, Umbriel, Titania, and Oberon, as well as the largest ring moon Puck, but their northern hemispheres were largely unobservable at the time of the flyby and were not imaged. Additionally, no spatially resolved datasets exist for the other 21 known moons, and their surface properties are essentially unknown. Because Voyager 2 was not equipped with a near-infrared mapping spectrometer, our knowledge of the Uranian moons' surface compositions, and the processes that modify them, is limited to disk-integrated datasets collected by ground- and space-based telescopes. Nevertheless, images collected by the Imaging Science System on Voyager 2 and reflectance spectra collected by telescope facilities indicate that the five classical moons are candidate ocean worlds that might currently have, or had, liquid subsurface layers beneath their icy surfaces. To determine whether these moons are ocean worlds, and investigate Uranus' ring moons and irregular Satellites, close-up observations and measurements made by instruments onboard a Uranus orbiter are needed.
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spectrophotometry of the small Satellites of saturn and their relationship to iapetus phoebe and hyperion
Icarus, 2005Co-Authors: Bonnie J Buratti, M D Hicks, A G DaviesAbstract:Abstract We have obtained broadband spectrophotometric observations of four of the recently discovered small Satellites of Saturn (Gladman et al., 2001, Nature 412, 163–166). The new data enable an understanding of the provenance, composition, and interrelationships among these Satellites and the other Satellites of Saturn, particularly Iapetus, Phoebe, and Hyperion. Temporal coverage of one satellite (S21 Tarvos) was sufficient to determine a partial rotational lightcurve. Our major findings include: (1) the Satellites are red and similar in color, comparable to D-type asteroids, some KBOs, Iapetus, and Hyperion; (2) none of the Satellites, including those from the “Phoebe Group” has any spectrophotometric relationship to Phoebe; and (3) S21 Tarvos exhibits a rotational lightcurve, although the data are not well-constrained and more observations are required to fit a definitive period. Dust created by meteoritic impacts and ejected from these Satellites and additional undiscovered ones may be the source of the exogenous material deposited on the low-albedo side of Iapetus. Recent work which states that the small irregular Satellites of Saturn have impacted Phoebe at least 6–7 times in the age of the Solar System (Nesvorny et al., 2003, Astron. J. 126, 398–429), suggests that such collisions may have propelled additional material from both Phoebe and the small irregular Satellites toward Iapetus. The accretion of material from outer retrograde Satellites may be a process that also occurs on Callisto and the Uranian Satellites.
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high resolution 0 33 0 92 μm spectra of iapetus hyperion phoebe rhea dione and d type asteroids how are they related
Icarus, 2002Co-Authors: Bonnie J Buratti, Kimberly A. Tryka, M D Hicks, Micah S Sittig, Ray L NewburnAbstract:New high-resolution spectra in the 0.33 to 0.92 μm range of Iapetus, Hyperion, Phoebe, Dione, Rhea, and three D-type asteroids were obtained on the Palomar 200-inch telescope and the double spectrograph. The spectra of Hyperion and the low-albedo hemisphere of Iapetus can both be closely matched by a simple model that is the linear admixture of the spectrum of a medium-sized, high-albedo icy saturnian satellite and D-type material. Our results support an exogenous origin to the dark material on Iapetus; furthermore, this material may share a common origin and a similar means of transport with material on the surface of Hyperion. The recently discovered retrograde Satellites of Saturn (Gladman et al., Nature412, 163–166) may be the source of this material. The leading sides of Callisto and the Uranian Satellites may be subjected to a similar alteration mechanism as that of Iapetus: accretion of low-albedo dust originating from outer retrograde Satellites. Phoebe does not appear to be related to either Iapetus or Hyperion. Separate spectra of the two hemispheres of Phoebe show no identifiable global compositional differences.
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ccd photometry of the Uranian Satellites
The Astronomical Journal, 1992Co-Authors: Bonnie J Buratti, James Gibson, Joel A MosherAbstract:Broadband V and R CCD observations of the Uranian satellite system have been obtained over the full range of solar phase angles observable from earth. These first visual observations of the phase curves of Miranda, Ariel, and Umbriel show that Ariel and Miranda exhibit the large opposition surges previously seen on the two outer Uranian Satellites. Umbriel, however, lacks an appreciable opposition surge; its surface is either extremely compact or consists of small particles which lack a backscattered component. The tenuous structure of the other Satellites is most likely due to the effects of eons of meteoritic gardening.
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comparative global albedo and color maps of the Uranian Satellites
Icarus, 1991Co-Authors: Bonnie J Buratti, Joel A MosherAbstract:Abstract The large Uranian Satellites comprise a unique class of dark, grayish objects. They exhibit important differences in albedo and color among each other and on their individual surfaces. Except for Umbriel, albedo variegations of up to a factor of 2 occur on their surfaces, and in the case of Ariel, Titania, and Oberon these changes are correlated with high albedo impact features. The bright regions of each satellite differ in the extent to which their color is different from the surrounding terrain: these areas of Miranda, Titania, and Oberon are clearly bluer, but morphologically similar areas on Ariel show no clear differences in color. This result suggests compositional differences on the Satellites' surfaces. Specifically, Ariel's upper mantle contains a larger fraction of slightly redder material. Although Umbriel has albedo variegations of ≤10%, its color variegations—which are ≥20%—are equal to or greater than those of the other four bodies. The Satellites tend to become redder as the distance from Uranus increases. The largest internal color differences are exhibited by a leading/trailing dichotomy: the leading side of at least the outer four Satellites is redder by 2–23% than the trailing side. The magnitude of this dichotomy also increases with the distance from the primary. The color measurements are not consistent with a surficial alteration process involving magnetospheric interactions. Rather it appears that the optical properties of these Satellites are affected by the accretion of low albedo reddish meteoritic dust which may be common in the outer Solar System. The specific source of this material in the Uranian system may be undiscovered retrograde Satellites orbiting outside the region of Oberon.
Richard Cartwright - One of the best experts on this subject based on the ideXlab platform.
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the science case for spacecraft exploration of the Uranian Satellites candidate ocean worlds in an ice giant system
arXiv: Earth and Planetary Astrophysics, 2021Co-Authors: Richard Cartwright, Bonnie J Buratti, Chloe B Beddingfield, Tom Nordheim, C M Elder, A M Bramson, M M Sori, Marc Neveu, Julie Castillorogez, R T PappalardoAbstract:The 27 Satellites of Uranus are enigmatic, with dark surfaces coated by material that could be rich in organics. Voyager 2 imaged the southern hemispheres of Uranus' five largest 'classical' moons Miranda, Ariel, Umbriel, Titania, and Oberon, as well as the largest ring moon Puck, but their northern hemispheres were largely unobservable at the time of the flyby and were not imaged. Additionally, no spatially resolved datasets exist for the other 21 known moons, and their surface properties are essentially unknown. Because Voyager 2 was not equipped with a near-infrared mapping spectrometer, our knowledge of the Uranian moons' surface compositions, and the processes that modify them, is limited to disk-integrated datasets collected by ground- and space-based telescopes. Nevertheless, images collected by the Imaging Science System on Voyager 2 and reflectance spectra collected by telescope facilities indicate that the five classical moons are candidate ocean worlds that might currently have, or had, liquid subsurface layers beneath their icy surfaces. To determine whether these moons are ocean worlds, and investigate Uranus' ring moons and irregular Satellites, close-up observations and measurements made by instruments onboard a Uranus orbiter are needed.
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the science case for spacecraft exploration of the Uranian Satellites
arXiv: Instrumentation and Methods for Astrophysics, 2020Co-Authors: Richard Cartwright, Chloe B Beddingfield, Tom Nordheim, C M Elder, William M Grundy, A M Bramson, M M Sori, R T Pappalardo, Marc Neveu, D M BurrAbstract:The five classical Uranian moons are possible ocean worlds that exhibit bizarre geologic landforms, hinting at recent surface-interior communication. However, Uranus' classical moons, as well as its ring moons and irregular Satellites, remain poorly understood. We assert that a Flagship-class orbiter is needed to explore the Uranian Satellites.
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probing the regoliths of the classical Uranian Satellites are their surfaces mantled by a layer of tiny h2o ice grains
Icarus, 2020Co-Authors: Richard Cartwright, William M Grundy, D P Cruikshank, Joshua P Emery, C B Beddingfield, N PinillaalonsoAbstract:Abstract We investigate whether the surfaces of the classical moons of Uranus are compositionally stratified, with a thin veneer of mostly tiny H2O ice grains (≤2 μm diameters) mantling a lower layer composed of larger grains of H2O ice, dark material, and CO2 ice (~10–50 μm diameters). Near-infrared observations (~1–2.5 μm) have determined that the H2O ice-rich surfaces of these moons are overprinted by concentrated deposits of CO2 ice, found almost exclusively on their trailing hemispheres. However, best fit spectral models of longer wavelength datasets (~3–5 μm) indicate that the spectral signature of CO2 ice is largely absent, and instead, the exposed surfaces of these moons are composed primarily of tiny H2O ice grains. To investigate possible compositional layering of these moons, we have collected new data using the Infrared Array Camera (IRAC) onboard the Spitzer Space Telescope (~3–5 μm). Spectral modeling of these new data is consistent with prior analyses, suggesting that the exposed surfaces of the Uranian moons are primarily composed of tiny H2O ice grains. Furthermore, analysis of these new data reveal that the trailing hemispheres of these moons are brighter than their leading hemispheres over the 3 to 5 μm wavelength range, except for Miranda, which displays no hemispherical asymmetries in its IRAC albedos. Our analyses also reveal that the surface of Ariel displays five distinct, regional-scale albedo zones, possibly consistent with the spatial distribution of CO2 ice on this moon. We discuss possible processes that could be enhancing the observed leading/trailing albedo asymmetries exhibited by these moons, as well as processes that could be driving the apparent compositional stratification of their near surfaces.
Anthony Mallama - One of the best experts on this subject based on the ideXlab platform.
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models for planetary eclipses of the Uranian Satellites
Icarus, 2007Co-Authors: Anthony MallamaAbstract:Abstract A model for computing the brightness of a satellite in the shadow of a planet is described, which takes into account the Sun–planet–satellite–sensor geometry, the satellite bi-directional reflectance function, and the refraction of sunlight in the planetary atmosphere. Synthetic light curves for eclipse ingress or egress of the five large Satellites of Uranus are generated. The model luminosities can be fitted to photometric observations in order to calculate a precise distance between the centers of the satellite and the planet. Alternately, when the satellite ephemeris is accurately known the atmospheric state of the planet can be studied.
D M Dowling - One of the best experts on this subject based on the ideXlab platform.
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hubble space telescope astrometric observations and orbital mean motion corrections for the inner Uranian Satellites
The Astronomical Journal, 1998Co-Authors: D Pascu, J R Rohde, Kenneth P Seidelmann, E N Wells, Charles T Kowal, Ben Zellner, A Storrs, D G Currie, D M DowlingAbstract:The 10 small inner Satellites of Uranus were discovered in 1986 with Voyager 2 and not seen again until 1994, when eight were recovered with the Hubble Space Telescope Wide Field Planetary Camera 2 for astrometric, dynamical, and photometric studies. Thirty-three exposures were taken on 1994 August 14 with the PC1 chip in the BVRI filters. Measurable images of Ariel and Miranda were also obtained on the same CCD frames with those of the faint Satellites. We present here the astrometric observations of these eight Satellites relative to Miranda, as well as corrected orbital mean motions for them. For the full-well images of Ariel and Miranda, the astrometric limitation was due to an inadequate geometric distortion correction and distance from center. For the faint inner Satellites, the astrometric precision varied from 50 mas for Bianca (V = 23 mag) to 9 mas for Puck (V = 20 mag) and was due primarily to a centroiding error caused by a low signal-to-noise ratio. The orbits of Owen & Synnott for the inner Satellites were compared with these observations and corrections derived to their mean daily motions. While the orbits of Owen & Synnott proved to be better than their errors indicated, the new mean motions are 2 orders of magnitude more precise.