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As Voyager 1 sailed through Saturn’s system of moons and rings last November 1980 it revealed new worlds not seen by man before. For centuries, since Galileo’s first telescopic observations in 1610, the satellites of Saturn had been no more than pin points of light, whilst the structure of the rings was barely resolved beyond 3 principal bands. Yet, within the space of a few hours, that picture changed dramatically as the images of these objects grew through Voyager’s cameras from mere specks into full and wondrous worlds. These pictures contained features that were not only intricate and astonishing in detail but which were, in many cases, unfamiliar and unexpected. A composite view of the Saturnian system as seen by Voyager 1 appears in Figure 1. Saturn’s rings, once thought to be broad belts of particles spread uniformly thin through billions of years of evolution and interparticle collisions, were found to be divided into hundreds of individual ringlets (Figure 2). And Cassini’s Division, a region which had been previously thought to be empty because of a ‘sweeping’ influence of Mimas, was found to contain many ringlets itself! The appearance of light and dark radial spokes in the B ring, which rotated with a velocity contrary to the law expected of Keplerian orbits, was baffling. And the F ring (Figure 3) was found to contain knots, kinks and braids which probably indicated the presence of electro-magnetic forces as well as gravitational forces (Smith et al. 1981).

An overview of the Voyager 2 encounter with Saturn is presented, including a brief discussion of the trajectory, the planned observations, and highlights of the results described in the subsequent reports.

The aim of the CASSINI mission is the exploration of the Saturnian system. The spacecraft is composed of an Orbiter and a Probe. The Probe is planned to land on Titan, Saturn's largest moon. While the Probe descends through Titan's atmosphere the Orbiter flying by serves as a relay for the transmission of scientific data towards Earth. Due to the large Earth-Saturn distance, ground control of the Probe's descent is impossible. Further, the knowledge about Titan's atmosphere still includes major uncertainties, preventing an accurate prediction of the planetary entry characteristics and of the subsequent descent via parachute. The descent profile has to provide appropriate conditions for the operation of the scientific instruments and to guarantee the transmission of all gathered scientific data. Thus, according to in-situ measurements adaptive control actions, related to the timing of parachute deployment and parachute exchange, have to be initiated. By these means it seems possible to satisfy the requirements despite uncertainties.

Maxwell determined the conditions of stability of a single ring of small particles moving round a large primary. He also made some incomplete remarks on the effects of introducing a second ring. The present investigation considers in greater detail the stability of two rings of particles moving about a primary and subject to the gravitational attractions of the primary and of each other. It is shown that such a system, under conditions satisfied by the Saturnian system, is stable, the particles oscillating finitely about their mean positions. It is inferred that the Saturnian system, considered as a number of such rings, is therefore also stable.

A theory concerning the orbital spacing patterns in the solar system, more intriguing than many of the traditional topics to our general studies astronomy students and useful pedagogically since it is accessible to such students in quantitative as well as qualitative terms, is presented. The orbital distributions of the planets and major satellite systems are fitted with a Bode‐type form. The Saturnian system requires vacant orbitals if the best fit is to have an accuracy comparable to that obtained for the other systems. One pattern of vacant orbitals is shown to be consistent with what would be expected if Titan produced resonant perturbations on the forming satellite system.

One major puzzle from the ground-based and Voyager observations of the saturnian system concerns the presence of the E ring and its possible relationship to the icy satellite, Enceladus1–3. Several issues concerning the surface property and interior condition of Enceladus remain unresolved if it is the main supplier of the E-ring particulate matter. Here we explore the intriguing alternative that the mass supply and orbital configuration of the E ring may be derived from a mass and momentum coupling between the A ring and the tenuous E ring a process of plasmatization and recondensation of the A-ring icy material. In the same way, the C ring could be replenished by the B ring. In this new view, plasma transport has a very important role in the dynamical evolution of the saturnian ring system.

An overview of the Voyager 1 encounter with Saturn is presented, including a brief discussion of the flight, trajectory, science plan formulation, and highlights of the results described in the subsequent reports.

Since the Voyager 1 close-pass observations of Titan, scientific interest in the nature and composition of the atmosphere and surface of Titan has increased greatly. This enhanced interest has led to the study of mission options to the Saturnian system with a principal goal of depositing a probe into the atmosphere of Titan. Such a probe could carry instrumentation to perform in situ measurements of the structure and composition of the atmosphere and clouds and of the morphology and composition of the surface. Previous studies have examined the possibility of modifying, in a minimal way, the Galileo probe currently being prepared for an atmospheric sampling mission to Jupiter. The purpose of this paper is to report the results of a study of probe-system concepts optimized for the Titan mission. The scientific rationale for such a mission to Titan is discussed and instruments to accomplish the scientific goals are indicated. Probe systems compatible with those goals and instruments are described, and the associated development costs for each are discussed.

We searched for H2O 6(1,6)-5(2,3) maser emission at 22.235 GHz from several Saturnian satellites with the Nobeyama 45m radio telescope in May 2009. Observations were made for Titan, Hyperion, Enceladus and Atlas, for which Pogrebenko et al. (2009) had reported detections of water masers at 22.235 GHz, and in addition for Iapetus and other inner satellites. We detected no emission of the water maser line for all the satellites observed, although sensitivities of our observations were comparable or even better than those of Pogrebenko et al.. We infer that the water maser emission from the Saturnian system is extremely weak, or sporadic in nature. Monitoring over a long period and obtaining statistical results must be made for the further understanding of the water maser emission in the Saturnian system., Comment: 8 pages, 2 figures, accepted for publication in PASJ (Letter)

In July 2004 the Cassini-Huygens mission reached the Saturnian system and started its orbital tour. A total of 75 orbits will be carried out during the primary mission until August 2008. In these four years Cassini crosses the ring plane 150 times and spends approx. 400 h within Titan's orbit. The Cosmic Dust Analyser (CDA) onboard Cassini characterises the dust environment with its extended E ring and embedded moons. Here, we focus on the CDA results of the first year and we present the Dust Analyser (DA) data within Titan's orbit. This paper does investigate High Rate Detector data and dust composition measurements. The authors focus on the analysis of impact rates, which were strongly variable primarily due to changes of the spacecraft pointing. An overview is given about the ring plane crossings and the DA counter measurements. The DA dust impact rates are compared with the DA boresight configuration around all ring plane crossings between June 2004 and July 2005. Dust impacts were registered at altitudes as high as 100 000 km above the ring plane at distances from Saturn between 4 and 10 Saturn radii. In those regions the dust density of particles bigger than 0.5 mu m can reach values of 0.001 m(-3). (c) 2006 Published by Elsevier Ltd.

During both Voyager encounters with the saturnian system, the Planetary Radio Astronomy experiment detected strong discrete episodic bursts of radio emission, termed Saturn electrostatic discharges (SED). An examination of Voyager 2 photopolarimeter data now reveals a narrow feature (possibly a gap) in Saturn's B ring. A single, unique object appears to be responsible for both the SED and this feature.

Voyager 2 will whiz past Saturn late next month, giving scientists yet another look at the planet's intricate ring system, its satellites, and the atmosphere. The encounter will concentrate on selected targets, though, rather than take a sweeping look at the entire Saturnian system, as Voyager 1 did. Voyager 2 will take higher-resolution photographs of five satellites—Enceladas, Tethys, lapetus, Hyperion, and Phoebe—than did its sister ship. Higher-resolution pictures of the rings also are expected. Closest approach to the planet will be on August 25 at 8:25 P.M. PDT (11:25 P.M. EDT). Transmission of signals from the spacecraft to earth will take nearly another hour and a half.