The White House, National Security Presidential Directive 39 (NSPD 39): U.S. Space-Based Position, Navigation, and Timing Policy (Dec. 8, 2004) (full-text).
This policy (also known as the 2004 U.S. Space-Based Positioning, Navigation, and Timing Policy) provides guidance for: (1) development, acquisition, operation, sustainment, and modernization of the Global Positioning System and U.S.-developed, owned and/or operated systems used to augment or otherwise improve the Global Positioning System and/or other space-based positioning, navigation, and timing signals; (2) development, deployment, sustainment, and modernization of capabilities to protect U.S. and allied access to and use of the Global Positioning System for national, homeland, and economic security, and to deny adversaries access to any space-based positioning, navigation, and timing services; and (3) foreign access to the Global Positioning System and U.S. Government augmentations, and international cooperation with foreign space-based positioning, navigation, and timing services, including augmentations.
NSPD-39 assigns governance roles to numerous federal agencies and other entities. In particular, within DOD, the U.S. Air Force is responsible for the overall development, acquisition, operation, security, and continued modernization of GPS. The Department of Transportation (DOT) serves as the lead civilian agency on GPS-related issues and has lead responsibility for developing requirements for civilian applications. The Department of Homeland Security (DHS), through the U.S. Coast Guard Navigation Center (NAVCEN), provides user support to the civilian, non-aviation GPS community.
Additionally, NSPD-39 requires that DOT, in coordination with DHS, develop, acquire, operate, and maintain backup capabilities that can support critical civilian and commercial infrastructure during a GPS disruption. NSPD-39 also assigns the DHS (in coordination with other agencies) the responsibility to identify, locate, and attribute any interference within the United States that adversely affects GPS use and to develop a central repository and database for reports of domestic and international interference to GPS civilian services.
NSPD-39 also directed the federal government to improve the performance of space-based PNT services, including by developing more robust resistance to interference for national security purposes, homeland security, and civilian, commercial, and scientific users worldwide. Furthermore, NSPD-39 assigns the Department of Commerce and the Federal Communications Commission (FCC) responsibility for mitigating electronic interference with U.S. space-based PNT services within the United States.
NSPD-39 also established a National Executive Committee for Space-Based PNT (National Executive Committee), chaired jointly by DOD and DOT, to coordinate GPS-related matters across federal agencies. The National Coordination Office for Space-Based PNT (NCO) houses the permanent staff of the National Executive Committee and provides day-to-day support for the committee's activities. Among other things, the National Executive Committee issued a 5-year plan for space-based PNT that recommends that DHS institute a risk management approach to assess threats, vulnerabilities, and potential consequences to interference to GPS signals and examine the best opportunities to mitigate those risks.