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T.R. Spilker (JPL/Caltech)
In cooperation with NASA's Solar System Exploration Subcommittee and its working groups, JPL is studying planetary science missions proposed for launch near the end of the next decade. Results will focus resources on developing technologies that enable a set of missions in which extraordinary scientific advances reward meeting severe technological challenges. This paper describes Saturn Ring Observer, an innovative, chemical-propulsion-only approach to a previous mission concept that enables close-up observation of Saturn's rings to obtain fundamental new information about ring dynamics, some relevant to planetary system formation. It describes the mission's science goals, provided by the Astrophysical Analogs in the Solar System Campaign Strategy Working Group, and the resulting mission concept.
The primary goal is understanding ring processes and evolution as a model for the origin of planetary systems. This involves direct observations of kinematic processes and parameters in the rings, direct observations of the physical nature and distribution of the particles, measuring local surface mass density over a wide radial range, and mapping the optical depth profile at high (~ 10 m) radial resolution and at several co-rotating longitudes.
The ring opening angle as seen from the approaching spacecraft sets an arrival time window at Saturn. Saturn orbit insertion uses a single-pass aerocapture followed by direct insertion near the Huygens gap at apoapsis. The science mission concept calls for placing the spacecraft in a ring-particle-like orbit with a very small inclination; frequent small plane-change maneuvers enable `hovering' 3 ±0.5 km removed from the ring plane. One month of science operations follow insertion, with as many as four changes in radial position totaling several thousand km.
This work was carried out at the Jet Propulsion Laboratory/California Institute of Technology, under contract to NASA.