battle management, and communication program of the ballistic missile defense system. (9) Integration with all other elements of the current ballistic missile defense system, including the Terminal High Altitude Area Defense, Aegis Ballistic Missile Defense, Aegis Ashore, and Patriot Air and Missile Defense Systems. (10) Such additional functions as determined by the Ballistic Missile Defense Review. (d) Cost estimates Whenever the Director develops a cost estimate for the sensor architecture required by subsection (a), the Director shall use— (1) the cost-estimating and assessment guide of the Government Accountability Office entitled GAO Cost Estimating and Assessment Guide (GAO-09-3SP), or a successor guide