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Z. H. Tang - One of the best experts on this subject based on the ideXlab platform.
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Phoebe's orbit from ground-based and space-based observations
Astronomy and Astrophysics - A&A, 2013Co-Authors: Josselin Desmars, Radwan Tajeddine, Qing-yu Peng, Z. H. TangAbstract:Context. The ephemeris of Phoebe, the ninth satellite of Saturn, is not very accurate. Previous dynamical models were usually too simplified, the astrometry is heterogeneous and, the Saturn's ephemeris itself is an additionnal source of error. Aims: The aim is to improve Phoebe's ephemeris by using a large set of observations, correcting some systematic errors and updating the dynamical model. Methods: The dynamical model makes use of the most recent ephemeris of planets and Saturnian satellites. The astrometry of Phoebe is improved by using a compilation of ground-based and space-based observations and by correcting the bias in stellar catalogues used for the reduction. Results: We present an accurate ephemeris of Phoebe with residuals of 0.45 arcsec and with an estimated accuracy of Phoebe's position of less that 100 km on 1990-2020 period. The catalogue of ground-based observations of Phoebe is available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/553/A36Table 5 is available in electronic form at http://www.aanda.org
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Phoebe s orbit from ground based and space based observations
Astronomy and Astrophysics, 2013Co-Authors: Radwan Tajeddine, Josselin Desmars, Qing-yu Peng, Z. H. TangAbstract:Context. The ephemeris of Phoebe, the ninth satellite of Saturn, is not very accurate. Previous dynamical models were usually too simplified, the astrometry is heterogeneous and, the Saturn’s ephemeris itself is an additionnal source of error. Aims. The aim is to improve Phoebe’s ephemeris by using a large set of observations, correcting some systematic errors and updating the dynamical model. Methods. The dynamical model makes use of the most recent ephemeris of planets and Saturnian satellites. The astrometry of Phoebe is improved by using a compilation of ground-based and space-based observations and by correcting the bias in stellar catalogues used for the reduction. Results. We present an accurate ephemeris of Phoebe with residuals of 0.45 arcsec and with an estimated accuracy of Phoebe’s position of less that 100 km on 1990‐2020 period.
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Phoebe s orbit from ground based and space based observations
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: Radwan Tajeddine, Josselin Desmars, Qing-yu Peng, Z. H. TangAbstract:The ephemeris of Phoebe, the ninth satellite of Saturn, is not very accurate. Previous dynamical models were usually too simplified, the astrometry is heterogeneous and, the Saturn's ephemeris itself is an additionnal source of error. The aim is to improve Phoebe's ephemeris by using a large set of observations, correcting some systematic errors and updating the dynamical model. The dynamical model makes use of the most recent ephemeris of planets and Saturnian satellites. The astrometry of Phoebe is improved by using a compilation of ground-based and space-based observations and by correcting the bias in stellar catalogues used for the reduction. We present an accurate ephemeris of Phoebe with residuals of 0.45 arcsec and with an estimated accuracy of Phoebe's position of less that 100 km on 1990-2020 period.
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Updated Phoebe's orbit
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: K. X. Shen, R. C. Qiao, G. Dourneau, Z. H. Tang, Hong-xin Zhang, S. H. WangAbstract:In recent years, many new CCD observations of Phoebe, the ninth Saturnian satellite, were published. In this paper, we have used all the observations of Phoebe available until 2009 to update Phoebe's orbit. These observations represent a total number of 2994 positions, spread over a time-interval of 105 years, from 1904 to 2009. The accuracy of the updated orbit of Phoebe presented here has been improved to about 0.1 arcsec as it has been fitted to a large number of new high-accuracy observations. However, the accuracy of the orbit remains limited by the accuracy of the observations. Moreover, we have shown that the new orbit is in quite good agreement with the very reliable JPL ephemeris, within less than 20 mas.
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ccd astrometric observations of Phoebe in 2005 2008
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: R. C. Qiao, G. Dourneau, K. X. Shen, X. Cheng, Z. H. Tang, S. H. Wang, Hong-xin ZhangAbstract:Astrometric observations of Phoebe, the faint ninth satellite of Saturn, with a visual magnitude of 16.5, were performed during four successive oppositions in 2005, 2006, 2007 and 2008. A total of 1173 new observed positions of Phoebe, representing more than 50 per cent of the observational data now available, were obtained during 30 nights of observation involving six missions and three telescopes. A comparison of our observed positions with the JPL Phoebe ephemeris shows the high quality of our observations, which have an accuracy of about 100 mas. Moreover, our observations appear to be consistent with this ephemeris within only about 50 mas.
Douglas P. Hamilton - One of the best experts on this subject based on the ideXlab platform.
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Radial profiles of the Phoebe ring: A vast debris disk around Saturn
Icarus, 2016Co-Authors: Daniel Tamayo, Stephen R. Markham, Matthew M. Hedman, Joseph A. Burns, Douglas P. HamiltonAbstract:Abstract We present observations at optical wavelengths with the Cassini Spacecraft’s Imaging Science System of the Phoebe ring, a vast debris disk around Saturn that seems to be collisionally generated by its irregular satellites. The analysis reveals a radial profile from 80–260 Saturn radii ( R S ) that changes behavior interior to ≈110 R S . We attribute this to either the moon Iapetus... sweeping up small particles, or to orbital instabilities that cause the ring to flare up vertically. Our study yields an integrated I / F at 0.635 µ m along Saturn’s shadow in the Phoebe ring’s midplane from 80–250 R S of 2 . 7 − 0.3 + 0.9 × 10 − 9 . We develop an analytical model for the size-dependent secular dynamics of retrograde Phoebe ring grains, and compare this model to the observations. This analysis implies that 1) the “Phoebe” ring is partially sourced by debris from irregular satellites beyond Phoebe’s orbit and 2) the scattered light signal is dominated by small grains (≲20 µ m in size). If we assume that the Phoebe ring is generated through steady-state micrometeoroid bombardment, this implies a power-law size distribution with index >4, which is unusually steep among Solar System rings. This suggests either a steep size distribution of ejecta when material is initially released, or a subsequent process that preferentially breaks up large grains.
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saturn s largest ring
Nature, 2009Co-Authors: Anne J Verbiscer, Michael F Skrutskie, Douglas P. HamiltonAbstract:Saturn's main ring system is a familiar image, but it's only part of the story. Most Solar System rings lie within a few radii of their planet, where gravitational accelerations inhibit satellite formation. Saturn's faint E ring is an exception, made up of sheets of dust that extend out to about 10 planetary radii. Beyond that, Spitzer Space Telescope observations of Saturn's most distant moon Phoebe reveal an enormous and previously unknown saturnian ring, extending from at least 128 to 207 planetary radii. The ring's vertical thickness of 40 planetary radii matches the up-and-down motion of Phoebe along its orbit, and the ring may be composed of material ejected from Phoebe. These ring particles appear to span the saturnian system from the main rings to the edges of interplanetary space. In the Solar System, planetary rings tend to lie within a few radii of their host body, because at these distances gravitational accelerations inhibit satellite formation. One of the best known exceptions to this rule is Saturn's E ring, a broad sheet of dust continuously supplied by source satellites that fades from view at five to ten planetary radii. An enormous ring associated with Saturn's outer moon Phoebe is now reported; it extends from at least 128 to 207 Saturn radii. Most planetary rings in the Solar System lie within a few radii of their host body, because at these distances gravitational accelerations inhibit satellite formation. The best known exceptions are Jupiter’s gossamer rings1 and Saturn’s E ring, broad sheets of dust that extend outward until they fade from view at five to ten planetary radii. Source satellites continuously supply the dust, which is subsequently lost in collisions or by radial transport. Here we report that Saturn has an enormous ring associated with its outer moon Phoebe, extending from at least 128RS to 207RS (Saturn’s radius RS is 60,330 km). The ring’s vertical thickness of 40RS matches the range of vertical motion of Phoebe along its orbit. Dynamical considerations argue that these ring particles span the Saturnian system from the main rings to the edges of interplanetary space. The ring’s normal optical depth of ∼2 × 10-8 is comparable to that of Jupiter’s faintest gossamer ring, although its particle number density is several hundred times smaller. Repeated impacts on Phoebe, from both interplanetary and circumplanetary particle populations, probably keep the ring populated with material. Ring particles smaller than centimetres in size slowly migrate inward2,3 and many of them ultimately strike the dark leading face of Iapetus.
Josselin Desmars - One of the best experts on this subject based on the ideXlab platform.
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Phoebe's orbit from ground-based and space-based observations
Astronomy and Astrophysics - A&A, 2013Co-Authors: Josselin Desmars, Radwan Tajeddine, Qing-yu Peng, Z. H. TangAbstract:Context. The ephemeris of Phoebe, the ninth satellite of Saturn, is not very accurate. Previous dynamical models were usually too simplified, the astrometry is heterogeneous and, the Saturn's ephemeris itself is an additionnal source of error. Aims: The aim is to improve Phoebe's ephemeris by using a large set of observations, correcting some systematic errors and updating the dynamical model. Methods: The dynamical model makes use of the most recent ephemeris of planets and Saturnian satellites. The astrometry of Phoebe is improved by using a compilation of ground-based and space-based observations and by correcting the bias in stellar catalogues used for the reduction. Results: We present an accurate ephemeris of Phoebe with residuals of 0.45 arcsec and with an estimated accuracy of Phoebe's position of less that 100 km on 1990-2020 period. The catalogue of ground-based observations of Phoebe is available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/553/A36Table 5 is available in electronic form at http://www.aanda.org
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Phoebe s orbit from ground based and space based observations
Astronomy and Astrophysics, 2013Co-Authors: Radwan Tajeddine, Josselin Desmars, Qing-yu Peng, Z. H. TangAbstract:Context. The ephemeris of Phoebe, the ninth satellite of Saturn, is not very accurate. Previous dynamical models were usually too simplified, the astrometry is heterogeneous and, the Saturn’s ephemeris itself is an additionnal source of error. Aims. The aim is to improve Phoebe’s ephemeris by using a large set of observations, correcting some systematic errors and updating the dynamical model. Methods. The dynamical model makes use of the most recent ephemeris of planets and Saturnian satellites. The astrometry of Phoebe is improved by using a compilation of ground-based and space-based observations and by correcting the bias in stellar catalogues used for the reduction. Results. We present an accurate ephemeris of Phoebe with residuals of 0.45 arcsec and with an estimated accuracy of Phoebe’s position of less that 100 km on 1990‐2020 period.
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Phoebe s orbit from ground based and space based observations
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: Radwan Tajeddine, Josselin Desmars, Qing-yu Peng, Z. H. TangAbstract:The ephemeris of Phoebe, the ninth satellite of Saturn, is not very accurate. Previous dynamical models were usually too simplified, the astrometry is heterogeneous and, the Saturn's ephemeris itself is an additionnal source of error. The aim is to improve Phoebe's ephemeris by using a large set of observations, correcting some systematic errors and updating the dynamical model. The dynamical model makes use of the most recent ephemeris of planets and Saturnian satellites. The astrometry of Phoebe is improved by using a compilation of ground-based and space-based observations and by correcting the bias in stellar catalogues used for the reduction. We present an accurate ephemeris of Phoebe with residuals of 0.45 arcsec and with an estimated accuracy of Phoebe's position of less that 100 km on 1990-2020 period.
Daniel Tamayo - One of the best experts on this subject based on the ideXlab platform.
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Radial profiles of the Phoebe ring: A vast debris disk around Saturn
Icarus, 2016Co-Authors: Daniel Tamayo, Stephen R. Markham, Matthew M. Hedman, Joseph A. Burns, Douglas P. HamiltonAbstract:Abstract We present observations at optical wavelengths with the Cassini Spacecraft’s Imaging Science System of the Phoebe ring, a vast debris disk around Saturn that seems to be collisionally generated by its irregular satellites. The analysis reveals a radial profile from 80–260 Saturn radii ( R S ) that changes behavior interior to ≈110 R S . We attribute this to either the moon Iapetus... sweeping up small particles, or to orbital instabilities that cause the ring to flare up vertically. Our study yields an integrated I / F at 0.635 µ m along Saturn’s shadow in the Phoebe ring’s midplane from 80–250 R S of 2 . 7 − 0.3 + 0.9 × 10 − 9 . We develop an analytical model for the size-dependent secular dynamics of retrograde Phoebe ring grains, and compare this model to the observations. This analysis implies that 1) the “Phoebe” ring is partially sourced by debris from irregular satellites beyond Phoebe’s orbit and 2) the scattered light signal is dominated by small grains (≲20 µ m in size). If we assume that the Phoebe ring is generated through steady-state micrometeoroid bombardment, this implies a power-law size distribution with index >4, which is unusually steep among Solar System rings. This suggests either a steep size distribution of ejecta when material is initially released, or a subsequent process that preferentially breaks up large grains.
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First observations of the Phoebe ring in optical light
Icarus, 2014Co-Authors: Daniel Tamayo, Matthew M. Hedman, Joseph A. BurnsAbstract:The Phoebe ring, Saturn’s largest and faintest ring, lies far beyond the planet’s well-known main rings. It is primarily sourced by collisions with Saturn’s largest irregular satellite Phoebe, perhaps through stochastic macroscopic collisions, or through more steady micrometeoroid bombardment. The ring was discovered with the Spitzer Space Telescope at 24 lm and has a normal optical depth of � 2 � 10 � 8
Joseph A. Burns - One of the best experts on this subject based on the ideXlab platform.
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Radial profiles of the Phoebe ring: A vast debris disk around Saturn
Icarus, 2016Co-Authors: Daniel Tamayo, Stephen R. Markham, Matthew M. Hedman, Joseph A. Burns, Douglas P. HamiltonAbstract:Abstract We present observations at optical wavelengths with the Cassini Spacecraft’s Imaging Science System of the Phoebe ring, a vast debris disk around Saturn that seems to be collisionally generated by its irregular satellites. The analysis reveals a radial profile from 80–260 Saturn radii ( R S ) that changes behavior interior to ≈110 R S . We attribute this to either the moon Iapetus... sweeping up small particles, or to orbital instabilities that cause the ring to flare up vertically. Our study yields an integrated I / F at 0.635 µ m along Saturn’s shadow in the Phoebe ring’s midplane from 80–250 R S of 2 . 7 − 0.3 + 0.9 × 10 − 9 . We develop an analytical model for the size-dependent secular dynamics of retrograde Phoebe ring grains, and compare this model to the observations. This analysis implies that 1) the “Phoebe” ring is partially sourced by debris from irregular satellites beyond Phoebe’s orbit and 2) the scattered light signal is dominated by small grains (≲20 µ m in size). If we assume that the Phoebe ring is generated through steady-state micrometeoroid bombardment, this implies a power-law size distribution with index >4, which is unusually steep among Solar System rings. This suggests either a steep size distribution of ejecta when material is initially released, or a subsequent process that preferentially breaks up large grains.
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First observations of the Phoebe ring in optical light
Icarus, 2014Co-Authors: Daniel Tamayo, Matthew M. Hedman, Joseph A. BurnsAbstract:The Phoebe ring, Saturn’s largest and faintest ring, lies far beyond the planet’s well-known main rings. It is primarily sourced by collisions with Saturn’s largest irregular satellite Phoebe, perhaps through stochastic macroscopic collisions, or through more steady micrometeoroid bombardment. The ring was discovered with the Spitzer Space Telescope at 24 lm and has a normal optical depth of � 2 � 10 � 8
