Navy Aegis Ballistic Missile Defense (BMD) Program: Background and Issues for Congress [Updated September 30, 2021] [open pdf - 2MB]
From the Introduction: "This report provides background information and issues for Congress on the Aegis ballistic missile defense (BMD) program, a program carried out by the Missile Defense Agency (MDA) and the Navy that gives Navy Aegis cruisers and destroyers a capability for conducting BMD operations. The issue for Congress is whether to approve, reject, or modify Department of Defense (DOD) acquisition strategies and proposed funding levels for the Aegis BMD program. Congress's decisions on the Aegis BMD program could significantly affect U.S. BMD capabilities and funding requirements, and the BMD-related industrial base."
CRS Report for Congress, RL33745
Congressional Research Service: https://crsreports.congress.gov/