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M. Dibiasi (L. Diabiasi Associates), W. S. Lewis, J. H. Waite (Southwest Research Institute), B. H. Mauk (Applied Physics Laboratory)
The Galileo mission has added enormously to our knowledge of the Jupiter system. However, as pointed out by the Committee on Planetary and Lunar Exploration (COMPLEX) in its 1994 report, "An Integrated Strategy for the Planetary Sciences: 1995-2010," Galileo will miss the "high latitudes that are essential to studies of aurorae, substorms, and magnetospheric coupling.... Also the crucial Io region will be only minimally sampled." We present a concept for a Jupiter Polar Orbiter (JPO) mission that would address key questions about Jupiter's magnetosphere and its coupling with the upper atmosphere that Galileo will leave unanswered.The nominal JPO mission would focus on three scientific themes: 1) magnetosphere-ionosphere coupling as manifested in Jupiter's auroral-zone and equatorial emissions; 2) acceleration and transport of charged particles within the magnetosphere, particularly in the unexplored high-latitude region, the critical regions of the inner magnetosphere between 6 and 10 RJ, and in the equatorial magnetosphere at 30 RJ; and 3) thermospheric dynamics and thermosphere-ionosphere-magnetosphere coupling. An experiment payload optimized to address the JPO science themes would comprise (i) instrumentation for in-situ particles-and-fields measurements and (ii) a suite of imagers for global auroral imaging at ultraviolet and X-ray wavelengths, energetic neutral atom imaging of hot ion populations in the inner and middle magnetosphere, and near- infrared imaging of thermospheric winds. A near-90-degree polar orbit, with a perijove of ~1 RJ and an apojove of ~30 RJ, would permit in-situ measurements over a range of altitudes and allow both global imaging of auroral and equatorial emissions and the Io torus and, at low-periapsis, high-resolution imaging of the thermospheric wind system. Mission duration would be one year.