This Broad Agency Announcement (BAA) by the Air Force Research Laboratory seeks research proposals for the Space Environment Technologies and Science (SETS) Program to understand and mitigate the space environment's impact on national security systems. The program covers five technical areas: Solar/Ionospheric Effects, Thermosphere/Satellite Drag, Plasma Physics, Particle Effects/Radiation, and the Cislunar Environment. This is a closed BAA that will remain open for eight years, but no proposals should be submitted against this baseline announcement; specific deadlines and requirements will be issued in future individual Calls. The period of performance and all deliverable items, such as hardware, software, or reports, will be specified within each Call. Offerors must maintain an active registration in the System for Award Management (SAM).