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Observations of Io with Juno-UVS

Presentation #111.01 in the session Io (Poster)

Published onOct 23, 2023
Observations of Io with Juno-UVS

The Juno spacecraft’s precessing polar orbit not only provides an excellent vantage point for UVS observations of Jupiter’s auroral emissions, but in the extended mission has been (or will be) used to perform close flybys of Ganymede (June 7, 2021, 1053 km altitude), Europa (September 29, 2022, 355 km altitude), and Io (December 30, 2023, 1498 km altitude; February 3, 2024, 1497 km altitude). Juno’s Ultraviolet Spectrograph (UVS) is a photon-counting far-ultraviolet (FUV) imaging spectrograph with a bandpass of 68-210 nm, which will be used to observe Io’s FUV emissions during the upcoming flybys. As with the similar close flyby of Ganymede (Greathouse et al. 2022; Molyneux et al. 2022), UVS will attempt to measure airglow emissions and reflected FUV sunlight from the surface of Io. The airglow emissions from oxygen (and sulfur) atoms will be more challenging to observe at Io than at Ganymede, however, since the background due to penetrating (>6 MeV) electrons at Io is expected to be many times larger than at Ganymede or Europa. In this talk we will present results from UVS data obtained during more distant observations of Io, including from near-perijove, looking outward from Jupiter’s equatorial upper atmosphere. While these more distant observations have low spatial resolution, the spectral signatures of O and S airglow emissions are clear. We also describe plans to observe Io near closest approach, when Io shields Juno from high-energy electron radiation at Io’s M-shell.

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