Over-the-Horizon Backscatter Radar

Efforts funded in this program focus on development, testing, and fielding, of a long-range early detection capability for airborne and surface targets of interest. Each line of effort acquires and fields a land based, high-frequency (HF) ionospheric, backscatter Over-the-Horizon RADAR (OTHR) for detection and tracking of airborne and surface targets over wide geographic areas. Fielding of this capability will enable detection, tracking and reporting of airborne and surface targets that may be obscured from conventional line of sight radar systems by the curvature of the earth. Tactical Multi-Mission Over the Horizon Radar(TACMOR) is a US Air Force remotely operated OTHR system being developed for deployment in the Republic of Palau (RoP). The system will provide enhanced Air Domain Awareness in key regions of USINDOPACOM's area of responsibility. This program may include necessary civilian pay expenses required to manage, execute, and deliver weapon system capability. The use of such program funds would be in addition to the civilian pay expenses budgeted in program element 0605827F, 0605828F, 0605829F, 0605831F, 0605832F, 0605833F, 0605898F, 0606398F. In FY 2025 0.000 million was expended for civilian pay expenses in this program, in FY 2026 0.111 million is forecasted for civilian pay expenses in this program element. TACMOR FY 2026 funds were allocated to - Program 012417F Project 674865 (budget authority 7). FY 2027-FY 2031 corrects the budget authority from 7 to 5 to appropriately reflect program efforts.

Homeland Defense (HLD) Over-the-Horizon radar (OTHR) efforts are focused on the development of a capability to provide long range early, warning for North America in response to threats. The program's intent is to design, develop, test and field advanced OTHR systems operating at levels of sensitivity far exceeding current US OTHR systems in operation. Program activities include command and control (C2) interface design and integration, transmit sub-system development and integration, HF sensor and digital receiver technology advancement, ionospheric characterization research, remote sensor management capability development, and sensor data fusion research. HLD OTHR data will be distributed and integrated into existing Integrated Air and Missile Defense (IAMD) early warning networks, to include the emerging architectures as applicable. In support of the Air and Cruise Missile Defense of the Homeland (ACMD-H) mission and North American Aerospace Defense Command (NORAD)/United States Northern Command USNORTHCOM (N/NC) Defense of North America mission, the project focuses investments to enhance capability for OTHRs. HLD OTHR will continue executing experimental efforts and procure necessary upgraded hardware with the Department of War science and technology community, including federally funded research and development center, defense laboratories, and small business expertise to characterize ionospheric conditions in CONUS locations. This program element may include necessary civilian pay expenses required to manage, execute, and deliver weapon system capability. The use of such program funds would be in addition to the civilian pay expenses budgeted in PE 0605827F, 0605828F, 0605829F, 0605831F, 0605832F, 0605833F, 0605898F, 0606398F. In FY 2025, 3.865 million was expended for civilian pay expenses in this program element. HLD OTHR development is not a new start. The program received initial funding in FY 2023 under the North Warning Systems Program (0102412F). The DAF realigned the funding in FY 2024 to Over-the-Horizon Backscatter Radar Program (0102417F) to report all DAF OTHR efforts. The HLD OTHR program utilized FY 2025 28.0 million for a Rapid Acquisition Authority requirement.