Can We Determine the Grain Composition of the Interstellar Medium with Astro E2 ? Julia C. Lee, Bruce Ravel (NRL) Harvard Center for Astrophysics 60 Garden Street, MS70 Cambridge, MA 02138 I will discuss the ability of the Astro E2 XRS to directly probe the grain composition of the ISM. Using experimental data taken at the National Synchrotron Light Source at Brookhaven National Laboratory, I will discuss our current prospects for (1) distinguishing gas from dust phase absorption, and (2) determining the chemical composition of interstellar grains, through the details of X-ray absorption fine structure.