Evaluating the Physical Properties of the Local Interstellar Medium Along Trajectories Toward the Nearest Stars

The local interstellar medium (LISM), the gas and dust drifting among the nearest stars, is our closest example of galactic interstellar material. Recently, Voyager 1 crossed the heliopause, effectively leaving the solar system and entering the galactic interstellar environment. In the coming decades, we will be designing and constructing successive missions pushing exploration outward faster and farther. Not only will the local interstellar medium be a prime "target" of study for these missions, but estimating the physical properties of the LISM will be critical to the safety and design of these missions. For example, the erosion of shielding material will depend on the size and composition of dust in the LISM. The weak signatures of the interstellar medium along the short path lengths toward nearby stars have necessitated LISM analysis using high-resolution ultraviolet spectroscopy. We will present an analysis of the dust content likely to be encountered by interstellar missions using the depletion of gas phase elements along the actual trajectories toward nearby stars, including the alpha Centauri system. We will include a discussion of the large-scale morphology of the LISM and the unique scientific objectives and measurements of the interstellar medium that would be enabled by a mission into our immediate cosmic neighborhood.