We discuss the roles of the two classes of space-environment sensors on operational space systems: (1) Targeted sensors capable of measuring the environment and effects at a level sufficient for providing situational awareness for the host spacecraft and (2) Comprehensive sensors capable of providing detailed environment measurements that can be mapped to a broad region of near-Earth space, providing global situational awareness and quantitative characterization of the environment. Our purpose is to show the usefulness of a heterogeneous architecture with both classes of sensors for the near-term and long-term needs of National Security Space