CCD Positions of Saturn and Its Major Satellites From 2002-2006

Peng, Q. Y.; Vienne, A.; Wu, Xuefeng; Gan, L.; Desmars, J.

doi:10.1088/0004-6256/136/5/2214

Cited by 10 publications

(6 citation statements)

References 12 publications

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“…suggesting that some terms could be missing in this model, including Titan's effect on Mimas' orbit. This is consistent with Peng et al (2008) who found a significant periodic signal in their Mimas (O-C) residuals compared to the TASS1.7 ephemeris, based on ground-based astrometric observations.…”

Section: Frequency Analysissupporting

confidence: 90%

Astrometric reduction ofCassiniISS images of the Saturnian satellites Mimas and Enceladus

Tajeddine¹,

Cooper²,

Lainey³

et al. 2013

A&A

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Aims. We provide astrometric observations of two of Saturn's main satellites, Mimas and Enceladus, using high resolution Cassini ISS Narrow Angle Camera images. Methods. We developed a simplified astrometric reduction model for Cassini ISS images as an alternative to the one proposed by the Jet Propulsion Labratory (JPL). The particular advantage of the new model is that it is easily invertible, with only marginal loss in accuracy. We also describe our new limb detection and fitting technique. Results. We provide a total of 1790 Cassini-centred astrometric observations of Mimas and Enceladus, in right ascension (α) and declination (δ) in the International Celestial Reference Frame (ICRF). Mean residuals compared to JPL ephemerides SAT317 and SAT351 of about one kilometre for Mimas and few hundreds of metres for Enceladus were obtained, in α cos δ and δ, with a standard deviation of a few kilometres for both satellites. A frequency analysis of the residuals revealed some periodic variability in the right ascension for Mimas. An additional analysis of Mimas' mean longitude suggests that some short-period terms are missing in the TASS orbital model.

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Section: Frequency Analysissupporting

confidence: 90%

Astrometric reduction ofCassiniISS images of the Saturnian satellites Mimas and Enceladus

Tajeddine¹,

Cooper²,

Lainey³

et al. 2013

A&A

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“…The USNO Flagstaff transit circle data, already included in COSS08, has been updated until 2009. Observations from (Peng et al 2008) have also been added. Moreover the highly accurate astrometric observations provided by the observation of the mutual phenomena of Saturnian satellites during 1995 and 2009 have been added.…”

Section: The Observation Setmentioning

confidence: 99%

Strong Tidal Dissipation in Saturn and Constraints on Enceladus' Thermal State From Astrometry

Lainey¹,

Karatekin²,

Desmars³

et al. 2012

ApJ

194

246

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Tidal interactions between Saturn and its satellites play a crucial role in boththe orbital migration of the satellites and the heating of their interiors. Therefore constraining the tidal dissipation of Saturn (here the ratio k 2 /Q) opens the door to the past evolution of the whole system. If Saturn's tidal ratio can be determined at different frequencies, it may also be possible to constrain the giant planet's interior structure, which is still uncertain. Here, we try to determine Saturn's tidal ratio through its current effect on the orbits of the main moons, using astrometric data spanning more than a century. We find an intense tidal dissipation (k 2 /Q= (2.3 ± 0.7) × 10 -4 ), which is about ten times higher than the usual value estimated from theoretical arguments. As a consequence, eccentricity equilibrium for Enceladus can now account for the huge heat emitted from Enceladus' south pole. Moreover, the measured k 2 /Q is found to be poorly sensitive to the tidal frequency, on the short frequency interval considered. This suggests that Saturn's dissipation may not be controlled by turbulent friction in the fluid envelope as commonly believed. If correct, the large tidal expansion of the moon orbits due to this strong Saturnian dissipation would be inconsistent with the moon formations 4.5 Byr ago above the synchronous orbit in the Saturnian subnebulae. But it would be compatible with a new model of satellite formation in which the Saturnian satellites formed possibly over longer time scale at the outer edge of the main rings. In an attempt to take into account for possible significant torques exerted by the rings on Mimas, we fitted a constant rate da/dt on Mimas semi-major axis, also. We obtained an unexpected large acceleration related to a negative value of da/dt= -(15.7 ± 4.4) × 10 -15 au/day. Such acceleration is about an order of magnitude larger than the tidal deceleration rates observed for the other moons. If not coming from an astrometric artifact associated to the proximity of Saturn's halo, such orbital decay may have significant implications on the Saturn's rings.

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“…We give only the outline of these techniques. Interested readers can refer to Peng et al (2003) or Peng et al (2008b) for more details. For the pixel position of Jupiter, our technique involves isolating the disc of Jupiter by creating a subimage.…”

Section: Observations and Image Processingmentioning

confidence: 99%

Precise CCD positions of Galilean satellite-pairs

Peng¹,

He²,

Lainey³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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In this paper, we present 526 precise CCD positions of Galilean satellite‐pairs of Jupiter, which have been extracted from 441 CCD frames captured by a 1‐m telescope at the Yunnan Observatory from 2002 to 2010. The four Galilean satellites (Io, Europa, Ganymede and Callisto) are used to calibrate the CCD field of view by comparing their pixel positions with their theoretical positions computed from two modern ephemerides of the Galilean satellites, L2 and JUP230, which have been developed by the Institut de Méchanique Céleste et de Calcul des Éphémérides and the Jet Propulsion Laboratory, respectively. In this paper, we focus on the relative position of a pair of satellites with short separation (less than 85 arcsec) for good internal precision. The mean (O − C) (observed minus computed) values of all these satellite‐pairs in right ascension and declination are found to be no larger than 6 mas and 2 mas, respectively, for each ephemeris. The estimated precision for one single observation is better than 30 mas in each direction.

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CCD Positions of Saturn and Its Major Satellites From 2002-2006

Cited by 10 publications

References 12 publications

Astrometric reduction ofCassiniISS images of the Saturnian satellites Mimas and Enceladus

Astrometric reduction ofCassiniISS images of the Saturnian satellites Mimas and Enceladus

Strong Tidal Dissipation in Saturn and Constraints on Enceladus' Thermal State From Astrometry

Precise CCD positions of Galilean satellite-pairs

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