Understanding our global heliosphere with UV observations: Unique opportunities on Interstellar Probe

Solar Lyman-a emission re-radiated from H atoms incoming to the heliosphere from interstellar medium is a powerful tool to probe globally plasma properties both at the heliosphere boundary and near the Sun. H Lyman-α line profiles reflect velocity distributions of low energy H atoms in the heliosphere which hold information about the plasma near the heliopause. H Lyman α intensities as observed at 1 AU serve as diagnostic of global properties of the solar wind. In this talk we will review what we have learned about the global heliospheric interaction from H Lyman-a observations from inside the heliosphere on SWAN/SOHO, Voyages/UVS and New Horizons/Alice missions. Outward trajectory of Interstellar Probe going through the outer heliosphere to the interstellar medium (ISM) up to 1000 AU enable unique science opportunities to explore global interaction between the solar wind and local ISM by observing for the first time Lyman-a emission from outside of the heliosphere. We will report a progress of UV working group in outlining primary science questions on the nature of the global heliosphere and Local Interstellar Cloud, planning observation strategy, measurement requirements and synergies with planetary UV observations for potential KBO fly-by.