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We now know that the outer solar system is host to at least six diverse planetary ring systems, each of which is a scientifically compelling target with the potential to inform us about the evolution, history and even the internal structure of the body it adorns. These diverse ring systems represent a set of distinct local laboratories for understanding the physics and dynamics of planetary disks, with applications reaching beyond our Solar System. We highlight the current status of planetary rings science and the open questions before the community to promote continued Earth-based and spacecraft-based investigations into planetary rings. As future spacecraft missions are launched and more powerful telescopes come online in the decades to come, we urge NASA for continued support of investigations that advance our understanding of planetary rings, through research and analysis of data from existing facilities, more laboratory work and specific attention to strong rings science goals during future mission selections.

We present astrometric observations of the Saturnian satellites Mimas, Enceladus, Tethys, Dione and Rhea from Cassini Imaging Science Subsystem (ISS) narrow-angle camera (NAC) images. Image sequences were designed to observe mutual occultations between these satellites. The positions of satellite centres were estimated by fitting ellipsoidal shape models to the measured limbs of the imaged satellites. Spacecraft pointing corrections were computed using the UCAC2 star catalogue. We provide a total of 2303 astrometric observations, resulting in 976 pairs, the remainder consisting of observations of a single satellite. Mean residuals for the individual satellite positions relative to the SAT360 ephemeris were 4.3 km in the line direction and -2.4 km in the sample direction, with standard deviations of 5.6 and 7.0 km respectively, an order of magnitude improvement in precision compared to published HST observations. By considering inter-satellite separations, uncertainties in camera pointing and spacecraft positioning along with possible biases in the individual positions of the satellites can be largely eliminated, resulting in an order-of-magnitude increase in accuracy compared to that achievable using the individual satellite positions. We show how factors relating to the viewing geometry cause small biases in the individual positions of order 0.28 pixel to become systematic across the dataset as a whole and discuss options for reducing their effects . The reduced astrometric data are provided in the form of individual positions for each satellite, together with the measured positions of reference stars, in order to allow more flexibility in the processing of the observations, taking into account possible future advances in limb-fitting techniques as well as the future availability of more accurate star catalogues, such as those from the GAIA mission., Comment: Accepted for publication in Astronomy & Astrophysics

We present numerically-derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus and Epimetheus from a fit to 2580 new Cassini ISS astrometric observations spanning February 2004 to August 2013. The observations are provided in a supplementary table. We estimate GM_ Atlas=0.384+/-0.001 x 10^(-3)km^3s^(-2), a value 13% smaller than the previously published estimate but with an order of magnitude reduction in the uncertainty. We also find GM_ Prometheus=10.677+/-0.006x10(-3)km^3s^(-2), GM_Pandora=9.133+/-0.009x10^(-3)km^3s^(-2), GM_Janus=126.51+/-0.03x10^(-3)km^3s^(-2) and GM_Epimetheus=35.110+/-0.009x10^(-3)km^3s^(-2), consistent with previously published values, but also with significant reductions in uncertainties. We show that Atlas is currently librating in both the 54:53 co-rotation-eccentricity resonance (CER) and the 54:53 inner Lindblad (ILR) resonance with Prometheus, making it the latest example of a coupled CER-ILR system, in common with the Saturnian satellites Anthe, Aegaeon and Methone, and possibly Neptune's ring arcs. We further demonstrate that Atlas's orbit is chaotic, with a Lyapunov time of ~10 years, and show that its chaotic behaviour is a direct consequence of the coupled resonant interaction with Prometheus, rather than being an indirect effect of the known chaotic interaction between Prometheus and Pandora. We provide an updated analysis of the second-order resonant perturbations involving Prometheus, Pandora and Epimetheus based on the new observations, showing that these resonant arguments are librating only when Epimetheus is the innermost of the co-orbital pair, Janus and Epimetheus. We also find evidence that the known chaotic changes in the orbits of Prometheus and Pandora are not confined to times of apse anti-alignement., Comment: 23 pages, 16 figures. Accepted for publication in The Astronomical Journal 23 September 2014 (corrected Fig. 11)

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 51), 2009. If Aegaeon has similar surface scattering properties as other nearby small Saturnian satellites (Pallene, Methone and Anthe), then its diameter is approximately 500 m. 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 co-rotation 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., Comment: 35 pages, 12 figures, accepted for publication in Icarus. Some typographical errors fixed

The Dirac equation is solved for two novel terms which describe the interaction energy between the half integral spin of a fermion and the classical, circularly polarized, electromagnetic field. A simple experiment is suggested to test the new terms and the existence of radiation induced fermion resonance., Comment: latex, 4 pages, no figures

A charge $q$ moving in a reference laboratory system with constant velocity {\bf V} in the $X$-axis produces in the $Z$-axis a longitudinal, phase free, vacuum magnetic field which is identified as the radiated ${\bf B}^{(3)}$ field of Evans, Vigier and others., Comment: ReVTeX file, 7pp., no figures