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The arrival of Juno at Jupiter enables repeated in situ observations above the Jovian ionosphere. The low altitude and high velocity of Juno at perijove permits direct sampling of ionospheric ion populations. We present the first direct observations above the ionosphere made by the Jovian Auroral Distributions Experiment Ion sensor (JADE-I). When looking into the spacecraft ram direction, JADE-I can measure ion energy distributions to below 1 eV/q along with ion composition. We report observations from 17 Juno perijove passes. At these latitudes, the low energy ions consist of protons and heavier ions, protons being the dominant species. Heavy ions-primarily oxygen and sulfur likely originating from the magnetosphere-are seen each pass, but their intensity varies. Other trace light ions are observed during some of the perijoves: H-3(+) (6 of 17 perijoves), He+ (2 of 17 perijoves). Ionospheric ions are observed up to altitudes of similar to 7,000 km.

Plain Language Summary The high speed of the Juno spacecraft permits its lower energy ion sensor-JADE-I-to chase down and observe low energy ions that have not been directly observed before. When looking into the direction the spacecraft is moving (i.e., the spacecraft ram direction), this sensor can observe ionospheric ions that are at a near-zero velocity in the rest frame of Jupiter. This permits direct observations of the ion population above Jupiter's ionosphere for the first time. Here, we present those observations for 17 close fly-bys at equatorial latitudes. We observe that the cold ion population contains a range of species. The dominant species is protons. Seen in each pass are also heavier oxygen and sulfur ions, but the intensity of these heavy ions varies from pass to pass. The presence of these heavy ions shows that there is some form of coupling between Jupiter and material on magnetic field lines far away from the planet, but the mechanism is not clear from these observations. Other light ions are also seen for some of the passes: H-3(+) for six of 17 passes, He+ for two of 17 passes.