This thread may provide information about some potential approaches to guidance for hypersonic vehicles, albeit for airborne targets.I haven't heard anybody explicitly mention guidance method - the tests to date (2011, 2017) were against a static target. I strongly suspect that it will be INS/GPS only guidance, with the possibility of allowing for an update before the terminal dive. I think terminal guidance at these speeds makes for problematic material choices - ie, heat dissipation vs RF transparency. I think anything optical would be right out. That and the USN booster seems to be only 34.5 inches wide, which would indicate a very narrow glider (the the same one is used across the CPGS, LRHW, and HCSW programs). There probably isn't a lot of room for antenna in the nose.