The Jupiter Polar Orbiter (JPO) mission is a one-year mission designed to investigate magnetosphere- ionosphere-thermosphere coupling at Jupiter. JPO's prime scientific objectives are (i) characterization of Jupiter's auroral and equatorial emissions through global imaging and identification of the magnetospheric processes responsible for them; (ii) identification of the mechanisms involved in the transport and acceleration of charged particles within the Jovian magnetosphere, particularly in the unexplored high-latitude region, the inner magnetosphere between 6 and 10 jovian radii, and the equatorial magnetosphere at 30 jovian radii; and (iii) characterization of Jupiteršs thermospheric winds.

The optimum JPO science payload comprises (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, for energetic neutral atom imaging of the hot ion populations in the inner and middle magnetosphere, and for near- infrared imaging of thermospheric winds. The optimum orbit for the JPO mission is a near-90-degree polar orbit, with a perijove of ~ 1 jovian radius and an apojove of ~ 30 jovian radii. This orbit permits in-situ measurements over a range of altitudes and allows both global imaging of auroral and equatorial emissions and the Io torus and, at low-periapsis, high-resolution imaging of the thermospheric wind system.

The JPO mission will address key questions left unanswered by the Galileo mission, which samples the Io region only minimally and the high latitude regions not at all. Measurements in both regions are critically important for our understanding of plasma processes occurring in the jovian magnetosphere and of their effects on the structure and dynamics of Jupiteršs upper atmosphere.

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