Novel HST observations of the Galilean moons Io and Ganymede, and simultaneous Juno-UVS observations of the Io footprint

Within two Hubble Space Telescope (HST) campaigns in support of the NASA Juno mission (GO14634 & GO15638, PI D. Grodent), spectra and spectral images of the moons Io and Ganymede were obtained by HST's Space Telescope Imaging Spectrograph (STIS) and Cosmic Origins Spectrograph (COS) on several occasions between 2017 and 2019.
On one occasion around Juno's perijove #14 in July 2018, the Juno Ultraviolet Spectrograph (UVS) observed Io's footprint simultaneously to the HST imaging of Io. We compare the temporal variability of the local moon aurora and the footprint brightness. Through this comparison, we investigate how the amplitude and phase of the periodically changing brightness of Io's aurora and the footprint are correlated.
Additionally, we present results from two novel far-UV observations of Ganymede: High- sensitivity spectra of the moon going into eclipse as well spectral images of the moon while transiting Jupiter. Both Ganymede observations are used to constrain the optical depth of the moon's atmosphere in the far-UV.