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Ganymede is the primary target of the upcoming JUICE mission comma but many open questions currently exist about the unique magnetosphere-within-a-magnetosphere interaction between Ganymede and Jupiter. The virgul10 degree offset between Jupiter.s rotation and magnetic axes leads to a time-varying interaction between the magnetospheres of the two bodies comma with Ganymede encountering the densest Jovian plasma at System III longitudes around 110 and 290 degrees. Previous observations of Ganymede.s ultraviolet auroral emissions indicated that the orbital trailing and leading hemispheres respond differently to the changing plasma environment the leading hemisphere emissions were found to be significantly more variable than the trailing emissions on a range of timescales. However comma the two hemispheres were observed in different regions of System III longitude comma and it is unclear if the difference in variability was real comma or related to changes in the rate of reconnection with System III comma as suggested by a recent analysis of radio observations. Our proposed program addresses this question by observing both hemispheres over a wide range of System III longitudes comma including both plasma sheet crossings and regions of high and low radio emission probability comma thereby conclusively determining whether the apparent disparate behavior of the two hemispheres is real. Our proposed observations comma using COS G130M comma will also provide the ability to test previous analysis of the expected O-O2 ratio in Ganymede.s atmosphere comma and will place constraints on S ions local to Ganymede. An improved understanding of the near-Ganymede environment will provide useful information in advance of the JUICE mission.