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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.10.024 Byline: M.M. Hedman (a), N.J. Cooper (b), C.D. Murray (b), K. Beurle (b), M.W. Evans (b)(a), M.S. Tiscareno (a), J.A. Burns (a)(c) Keywords: Saturn, Satellites; Saturn, Rings; Satellites, Dynamics; Resonances, Orbital Abstract: Aegaeon (Saturn LIII, S/2008 S1) is a small satellite of Saturn that orbits within a bright arc of material near the inner edge of Saturn's G-ring. This object was observed in 21 images with Cassini's Narrow-Angle Camera between June 15 (DOY 166), 2007 and February 20 (DOY 051), 2009. If Aegaeon has similar surface scattering properties as other nearby small saturnian satellites (Pallene, Methone and Anthe), then its diameter is approximately 500m. Orbit models based on numerical integrations of the full equations of motion show that Aegaeon's orbital motion is strongly influenced by multiple resonances with Mimas. In particular, like the G-ring arc it inhabits, Aegaeon is trapped in the 7:6 corotation eccentricity resonance with Mimas. Aegaeon, Anthe and Methone therefore form a distinctive class of objects in the Saturn system: small moons in corotation eccentricity resonances with Mimas associated with arcs of debris. Comparisons among these different ring-arc systems reveal that Aegaeon's orbit is closer to the exact resonance than Anthe's and Methone's orbits are. This could indicate that Aegaeon has undergone significant orbital evolution via its interactions with the other objects in its arc, which would be consistent with the evidence that Aegaeon's mass is much smaller relative to the total mass in its arc than Anthe's and Methone's masses are. Author Affiliation: (a) Department of Astronomy, Cornell University, Ithaca, NY 14853, USA (b) Queen Mary University of London, Astronomy Unit, School of Mathematical Sciences, Mile End Road, London E1 4NS, UK (c) Department of Theoretical and Applied Mechanics, Cornell University, Ithaca, NY 14853, USA Article History: Received 29 July 2009; Revised 28 October 2009; Accepted 29 October 2009 Article Note: (footnote) [star] This paper is dedicated to the memory of Kevin Beurle.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.11.001 Byline: M.M. Hedman (a), C.D. Murray (b), N.J. Cooper (b), M.S. Tiscareno (a), K. Beurle (b), M.W. Evans (b), J.A. Burns (a)(c) Keywords: Saturn; rings; Saturn; satellites; Resonances; rings Abstract: Using Cassini images, we examine the faint material along the orbits of Methone, Anthe and Pallene, three small moons that reside between the orbits of Mimas and Enceladus. A continuous ring of material covers the orbit of Pallene; it is visible at extremely high phase angles and appears to be localized vertically to within [+ or -]25 km of Pallene's inclined orbit. By contrast, the material associated with Anthe and Methone appears to lie in longitudinally confined arcs. The Methone arc extends over [approximately equal to]10[degrees] in longitude around the satellite's position, while the Anthe arc reaches [approximately equal to]20[degrees] in length. The extents of these arcs are consistent with their confinement by nearby corotation eccentricity resonances with Mimas. Anthe has even been observed to shift in longitude relative to its arc in the expected manner given the predicted librations of the moon. Author Affiliation: (a) Department of Astronomy, Cornell University, Ithaca, NY 14853, USA (b) Queen Mary University of London, Astronomy Unit, Mile End Road, London E1 4NS, United Kingdom (c) Department of Theoretical and Applied Mechanics, Cornell University, Ithaca, NY 14853, USA Article History: Received 7 August 2008; Revised 6 November 2008; Accepted 10 November 2008

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.01.006 Byline: N.J. Cooper (a), C.D. Murray (a), M.W. Evans (a), K. Beurle (a), R.A. Jacobson (b), C.C. Porco (c) Keywords: Satellites; dynamics; Saturn; satellites; Resonances; orbital Abstract: We describe the astrometry and dynamics of Anthe (S/2007 S 4), a new satellite of Saturn discovered in images obtained using the Imaging Science Subsystem (ISS) of the Cassini spacecraft. Included are details of 63 observations, of which 28 were obtained with Cassini's narrow-angle camera (NAC) and 35 using its wide-angle camera (WAC), covering an observation time-span of approximately 3 years. We estimate the diameter of Anthe to be [approximately equal to]1.8 km. Orbit modeling based on a numerical integration of the full equations of motion fitted to the observations show that Anthe is in a first-order 11:10 mean motion resonance with Mimas. Two resonant arguments are librating: [phi].sub.1=11I'.sup.'-10I'-I and [phi].sub.2=11I'.sup.'-10I'-I.sup.'-I[c].sup.'+I[c], where I', I and I[c] refer to the mean longitude, longitude of pericenter and longitude of ascending node of Mimas and Anthe, with the primed quantities corresponding to Anthe. These resonances cause periodic variations in the orbital elements. The semi-major axis varies by [+ or -]26 km over a 913-day period. Anthe is also close to a second-order eccentricity-type mean motion resonant relationship of the form 77:75 with Methone. Since Methone is also in a first-order resonance with Mimas [Spitale, J.N., Jacobson, R.A., Porco, C.C., Owen, W.M., 2006. Astron. J. 132, 692-710], an additional indirect perturbation exists between Methone and Anthe via Mimas. Neither effect is detectable in the orbit fitting and the short-term dynamical evolution of Anthe is dominated by the Mimas-Anthe resonances alone. The expected modulation effect from the Mimas-Tethys 4:2 inclination resonance is also insignificant over this time period. By including Cassini ISS observations of Mimas in the numerical integration fit, we estimate the GM of Mimas to be 2.509[+ or -]0.004km.sup.3s.sup.-2, consistent with Jacobson et al. [Jacobson, R.A., Spitale, J., Porco, C.C., Owen, W.M., 2006. Astron. J. 132, 711-713]. Author Affiliation: (a) Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK (b) Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099, USA (c) Cassini Imaging Central Laboratory for Operations (CICLOPS), Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA Article History: Received 31 October 2007; Revised 8 January 2008

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2005.06.009 Byline: C.D. Murray, N.J. Cooper, M.W. Evans, K. Beurle Keywords: Satellites; general; Satellites of Saturn; Orbits; Resonances Abstract: We describe the astrometry and dynamics of S/2004 S 5 (provisionally named Polydeuces), a new satellite of Saturn, discovered in images recorded using the Imaging Science Subsystem (ISS) of the Cassini spacecraft. A total of 119 observations are presented, 101 of which were obtained with Cassini's narrow-angle camera and 18 using the wide-angle camera. Orbit determinations, based on a uniformly precessing ellipse model clearly showed S/2004 S 5 to be a possible co-orbital of Dione. By fitting a numerical solution of the full equations of motion to the available observations, we show that S/2004 S 5 is executing tadpole motion around Dione's L.sub.5 Lagrangian point, with a libration amplitude varying between +21.16[+ or -]0.03[degrees] and -31.68[+ or -]0.06[degrees] over a period of 791.3[+ or -]0.1 days. Author Affiliation: Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK Article History: Received 11 March 2005; Revised 11 June 2005

We describe the astrometry and dynamics of S/2004 S 5 (provisionally named Polydeuces), a new satellite of Saturn, discovered in images recorded using the Imaging Science Subsystem (ISS) of the Cassini spacecraft. A total of 119 observations are presented, 101 of which were obtained with Cassini's narrow-angle camera and 18 using the wide-angle camera. Orbit determinations, based on a uniformly precessing ellipse model clearly showed S/2004 S 5 to be a possible co-orbital of Dione. By fitting a numerical solution of the full equations of motion to the available observations, we show that S/2004 S 5 is executing tadpole motion around Dione's [L.sub.5] Lagrangian point, with a libration amplitude varying between +21.16 [+ or -] 0.03[degrees] and -31.68 [+ or -] 0.06[degrees] over a period of 791.3 [+ or -] 0.1 days. Keywords: Satellites, general; Satellites of Saturn; Orbits; Resonances