The satellite system of Saturn has been the subject of much research in celestial mechanics since the foundation of this branch of astronomy in its classical form by Laplace in the late 18th century. It has been described as a "solar system in miniature" by virtue of the range of types of behaviour which characterise the satellite orbits. Within a single system we have A very dominant satellite (Titan) which is unaffected by periodic perturbations of a planetary type by its neighbours, and whose motion features only secular perturbations and small periodic solar perturbations. Two pairs of satellites (Mimas - Tethys and Enceladus - Dione) whose mean motions are very nearly in the ratio 2:1, causing (among other things) significant librations in the mean longitude of the satellites concerned. A satellite of rather low mass (Hyperion) whose motion is entirely characterised by a close 3:4 resonance with the dominant satellite in the system. The theory of the motion of Hyperion is a problem of such great complexity that Newcomb placed it second only to the lunar theory. A satellite (Iapetus) whose theory is dominated by large periodic solar perturbations due to the great distance at which it orbits Saturn. Moreover, the position of the orbit plane of this satellite is governed by long-period perturbations of roughly equal size acting in two widely-separated planes. This means that the secular theory of the node and inclination of Iapetus is of particular interest. This diversity of behaviour might at first appear daunting, but each satellite (even Titan) only affects its closest neighbours. Most of the satellites are very small and their perturbing effect is only noticeable when it is amplified by a near-resonance. Thus Tethys perturbs Mimas but not Enceladus or Dione, despite the fact that the latter two are its closest neighbours. We may treat the inner satellites (Mimas, Enceladus, Tethys and Dione) as a self-contained system, and likewise the outer satellites, Rhea, Titan, Hyperion and Iapetus. It is the outer satellite system, and in particular the subset consisting of Titan, Hyperion and Iapetus, that is the subject of this thesis. We choose not to include Rhea as an object for direct study, though we shall always be mindful of its perturbations upon the other three satellites. We begin in chapter 2 with a revision of Sinclair's (1974) theory of the motion of Iapetus in the light of later critical work by Rapaport (1978) and Sinclair and Taylor (1985). Both papers note that Sinclair's theory requires improvement and Rapaport investigates a near-resonance with Titan which affects the mean longitude of Iapetus. During the course of our revision, we find that the principal omissions from Sinclair's theory arise from solar perturbations in the node and inclination. These perturbations have periods of up to 29 years and affect the observed position of the satellite as seen from Earth by as much as 0.14 arc-seconds. We also find that Rapaport overestimates the significance of the Titan quasi-resonance perturbations by a factor of 3, and we present an improved theory of the motion of Iapetus which includes the additional solar and Titan perturbations. The theory is compared with Sinclair and Taylor's (1985) integration of the motion of the outer satellites to obtain a quantitative estimate of the precision of the theory. Chapter 3 contains a study of the secular motion of the orbit plane of a satellite acted upon by several perturbing forces in different fixed planes. We find that the concept of a Laplacian plane may easily be extended to any number of perturbing forces up to fourth order in the inclinations. We use auxiliary parameters p = sin i sin Ω and q = sin i cos Ω to represent the position of the orbit plane of the perturbed satellite in an arbitrary fixed reference frame and we show that the pole of the orbit describes an ellipse about a point which is the pole of the Laplacian plane of the orbit. This method is applied to the particular case of Iapetus, which is subject to significant perturbations by Titan and the Sun, and smaller perturbations due to the oblateness of Saturn. The orbit of Iapetus is shown to maintain an almost constant inclination of 7° to its Laplacian plane, upon which it precesses with a period of 3000 years. We fit this model to observed values of the node and inclination of the orbit of Iapetus and we determine the mass of Titan as a result of the fitting process. Chapters 4 and 5 are concerned with the problem of modelling the motion of Titan, Hyperion and Iapetus by numerical integration. This approach has been used by Sinclair and Taylor with some success. They fitted an integration to photographic (astrometric) observations over the period 1967 to 1982 and determined values for the initial position and velocity components of each of the satellites plus the J2 form-factor and the mass of Saturn and the mass of Titan. In this thesis we attempt to fit a similar integration to visual (micrometric) observations made during the period 1874 to 1947. Chapter 4 gives an account of the preparation of the raw data for comparison with any dynamical model. This preparation includes the reduction of the various timescales to Universal Time and Ephemeris Time, the calculation of the topocentric position vector of Saturn at the instant of each observation, and an analysis of the effects of stellar aberration and atmospheric refraction upon position angle and separation measures. In addition, we develop the partial derivatives of position angle and separation observations with respect to the Saturnicentric rectangular coordinates of the satellite(s) involved. Chapter 5 contains a description of the numerical integration method and the procedure employed in fitting the integration to the observations. It also contains an account of the results of a number of trial iterations in which we attempt to determine the parameters of the satellite system. In particular, values are obtained for the J2 form-factor of Saturn and the mass of Titan.

Over the past few decades, short-period giant planets have been discovered in extrasolar planetary systems, allowing for new tests of planetary evolution theories. Many of these giant exoplanets have high temperatures (>1000 K) and do not directly resemble Jupiter or Saturn. Only in the past few years have exoplanets akin to the cold (~100 K) gas giants in the solar system been identified. In this dissertation, I investigated giant gaseous planets through comparative studies of Saturn and exoplanets. Saturn has been the target of numerous high-precision observations, making it the ideal candidate for comparative studies. I simulated transit observations of a Saturn-analog exoplanet and determined that cold exoplanet atmospheres are amenable to characterization via transmission spectroscopy. By casting Saturn as an exoplanet, I demonstrated the potential for exoplanets to place the solar system in a Galactic context. The transit spectrum of Saturn also highlighted the importance of atmospheric refraction in transit observations. Refraction alters the path of light propagating in an atmosphere. I showed that out-of-transit refracted light provides an opportunity to identify and characterize the atmospheres of cold transiting and non-transiting exoplanets. I searched exoplanet parameter space to locate the maximal effect and derived a criterion that predicts which atmospheres produce detectable refracted light signatures. My consideration of exoplanetary refraction also included a parallel study of Saturn's atmosphere. I developed a novel method to measure atmospheric refractivity from distorted images of the Sun. I used this method to infer Saturn's atmospheric structure for more than a dozen Saturn solar occultations and to identify seasonal variations in Saturn's stratospheric temperature. Lastly, I obtained ground-based observations of the long-period transiting exoplanet Kepler-421b to refine its transit ephemeris. Without accurate transit ephemerides, long-period exoplanet characterization with large space-based observatories cannot occur. My unique observations represent the first step toward ensuring that long-period exoplanets are characterized in the near future. In summary, this dissertation lays the foundation for investigations of cold giant exoplanets, which exist in an almost entirely unexplored regime of exoplanetary science. Using Saturn to provide context and motivation, I began confronting the challenges facing this new discipline of exoplanetary science.

The Cassini spacecraft orbits Saturn since 2004, carrying a multitude of instruments for studies of the plasma environment around the planet as well as the constituents of the ring system. Of particular interest to the present thesis is the large E ring, which consists mainly of water ice grains, smaller than a few micrometres, referred to as dust. The first part of the work presented here is concerned with the interaction between, on the one hand, the plasma and, on the other hand, the dust, the spacecraft and the Langmuir probe carried by the spacecraft. In Paper I, dust densities along the trajectory of Cassini, as it passes through the ring, are inferred from measured electron and ion densities. In Paper II, the situation where a Langmuir probe is located in the potential well of a spacecraft is considered. The importance of knowing the potential structure around the spacecraft and probe is emphasised and its effect on the probe's current-voltage characteristic is illustrated with a simple analytical model. In Paper III, particle-in-cell simulations are employed to study the potential and density profiles around the Cassini as it travels through the plasma at the orbit of the moon Enceladus. The latter part of the work concerns large-scale currents and convection patterns. In Paper IV, the effects of charged E-ring dust moving across the magnetic field is studied, for example in terms of what field-aligned currents it sets up, which compared to corresponding plasma currents. In Paper V, a model for the convection of the magnetospheric plasma is proposed that recreates the co-rotating density asymmetry of the plasma. / QC 20120507

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Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1975. / Bibliography: leaves 178-182. / x, 182 leaves ill

Köln, University, Diss., 2004.

Zugl.: Köln, University, Diss., 2004.

Particles in Saturn’s main rings range in size from dust to even kilometer-sized objects. Their size distribution is thought to be a result of competing accretion and fragmentation processes. While growth is naturally limited in tidal environments, frequent collisions among these objects may contribute to both accretion and fragmentation. As ring particles are primarily made of water ice attractive surface forces like adhesion could significantly influence these processes, finally determining the resulting size distribution. Here, we derive analytic expressions for the specific self-energy Q and related specific break-up energy Q⋆ of aggregates. These expressions can be used for any aggregate type composed of monomeric constituents. We compare these expressions to numerical experiments where we create aggregates of various types including: regular packings like the face-centered cubic (fcc), Ballistic Particle Cluster Aggregates (BPCA), and modified BPCAs including e.g. different constituent size distributions. We show that accounting for attractive surface forces such as adhesion a simple approach is able to: a) generally account for the size dependence of the specific break-up energy for fragmentation to occur reported in the literature, namely the division into “strength” and “gravity” regimes, and b) estimate the maximum aggregate size in a collisional ensemble to be on the order of a few meters, consistent with the maximum aggregate size observed in Saturn’s rings of about 10m. / Die Ringe des Saturns bestehen aus Myriaden von Teilchen, deren Größe von Mikrometern (Staub) bis hin zu Hunderten von Metern reicht. Die Ringteilchen bestehen hauptsächlich aus Eis, wobei attraktive Oberflächenkräfte wie Adhäsion und Gravitation zur Bildung von Aggregaten führen kann. Das Wachstum der Aggregate wird durch die Wirkung der Gezeitenkräfte und auch durch Kollisionen der Ringteilchen untereinander auf natürliche Weise begrenzt. Die Kollisionen der Ringteilchen führen zu Akkretion und Fragmentation, welche die resultierende Größenverteilung der Agglomerate schließlich bestimmen. In dieser Arbeit wurden Ausdrücke für die spezifische Eigenenergie Q der Aggregate und der in Relation stehenden spezifischen Fragmentationsenergie Q* analytisch hergeleitet. Diese Ausdrücke können für alle aus monomeren Teilchen bestehenden Agglomerate verwendet werden. Die analytisch gewonnenen Ergebnisse wurden mit numerischen Experimenten verglichen. In den numerischen Experimenten wurden verschiedene Agglomerattypen erzeugt: (i) Agglomerate mit kubischem Kristallsystem, (ii) ballistische Teilchenaggregate und (iii) modifiziert ballistische Teilchenaggregate. Für die ballistischen Teilchenaggregate wurden verschiedene Größenverteilungen der Konstituenten verwendet. Als Ergebnis lassen sich die erzeugten Aggregate gemäß ihrer Größe in zwei Gruppen einteilen. Während die kleinen Aggregate hauptsächlich durch die Kontaktkräfte (Adhäsion) zusammengehalten werden, dominiert bei großen Aggregaten (größer als einige Meter) die Gravitationskraft. D.h. wächst aus kleinen Teilchen ein Aggregat, so wird dieses zunächst durch die haftenden Kontakte zwischen den Teilchen zusammengehalten. Wächst das Agglomerat über eine bestimmte Größe, so ist es die Eigengravitation, die den Körper zusammenhält. Damit kann die maximale Gesamtgröße der Aggregate im Kollisionsensemble abgeschätzt werden. Der so bestimmte Wert von einigen Metern stimmt mit der aus Beobachtungen berechneten maximalen Größe der Ringteilchen von rund 10 Metern gut überein.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Designed and implemented as a partnership between GM and the UAW, Saturn breaks new ground in firm governance,management and industrial relations. Through detailed study of Saturn?s partnership arrangements we have found that thelocal management and union leaders have not only implementedthe contractual joint governance institutions which involvelabor in business strategy, product development, supplier andretailer selection, and manufacturing policy, but have also created a system of co-management which gives hundreds ofjointly selected unionoperations management.1members theIn order toresponsibilities ofunderstand the impact ofthe involvement of union members as management, we analyzedthe relationship between the behaviors of both representedand non-represented middle managers, the dynanics of theirindividual union-management partnership relations,differences in their patterns of communication andcoordination, and Saturn?s quality performance. We alsoexamined each partner?s use of time to explore the balancingof social and economic tasks between represented and nonrepresentedpartners. These data were combined with analysesof the tensions within the union between its traditional rolein membership representation, and its new role in managementand governance. Finally, we raise questions regarding thelearning from and diffusion of Saturn to the rest of the GMand the UAW organizations. / The Impact of Co-Management and Joint Governance on Firm and Local Union Performance / Funds for this researchwere provided by the AlfredP.SloanFoundation,the MIT InternationalMotorVehicleResearchProgram,the MIT Leadersfor ManufacturingProgram,and the NationalscienceFoundation..