Over-the-Horizon Backscatter Radar

The Over-the-Horizon Backscatter Radar (PE 0102417F) program is a United States Air Force initiative focused on the research, development, testing, and fielding of advanced long-range radar systems capable of detecting and tracking airborne and surface targets beyond the line of sight. The primary objective of this program is to provide early warning and enhanced surveillance coverage over wide geographic areas, particularly in regions where conventional radar systems are limited by the curvature of the earth. The program supports multiple lines of effort, including the Tactical Multi-Mission Over-the-Horizon Radar (TACMOR), Homeland Defense Over-the-Horizon Radar (HLD-OTHR), and classified requirements supporting U.S. European Command (EUCOM).

The Tactical Multi-Mission Over-the-Horizon Radar (TACMOR) is a key component of this program, with development activities centered on deploying a high-frequency (HF) ionospheric backscatter radar system in the Republic of Palau (RoP). The goal of TACMOR is to enhance Air Domain Awareness within the U.S. Indo-Pacific Command (USINDOPACOM) area of responsibility by closing surveillance gaps in the Pacific region. The system will be operated by the United States in agreement with the RoP and is designed to provide real-time detection, tracking, and reporting of targets that may be concealed from traditional radar systems.

TACMOR development includes the establishment of an unmanned, remotely controlled facility with a transmit site comprising fourteen HF antenna elements and high-power amplifiers, as well as a receive site with 128 dual-monopole antenna elements. The transmit site will also feature environmental monitoring equipment to optimize radar performance based on ionospheric conditions. Data collected by TACMOR will be processed on-site and transmitted to an off-site operations control center, which will support mission planning and provide actionable intelligence to combatant commands and allied forces.

The Homeland Defense Over-the-Horizon Radar (HLD-OTHR) effort aims to extend the North Warning System (NWS) surveillance capabilities to provide long-range early warning for North America. This initiative is a response to emerging threats and is focused on developing, testing, and fielding advanced OTHR systems with greater sensitivity and range than current U.S. systems. HLD-OTHR will integrate with existing air and missile defense networks, including the DAF Battle Network and Cloud Based Command and Control (C2) architectures. This integration is intended to enhance the Air and Cruise Missile Defense of the Homeland and support NORAD/USNORTHCOM missions.

Key technical objectives for both TACMOR and HLD-OTHR include advancing HF sensor and digital receiver technologies, conducting ionospheric characterization research, developing remote sensor management capabilities, and improving sensor data fusion methods. The programs also emphasize the integration of command and control interfaces and the distribution of radar data to support multi-domain awareness and decision-making.

The FY 2026 budget request for the Over-the-Horizon Backscatter Radar program includes discretionary funding, with additional mandatory funds allocated for the Homeland Defense project. Planned activities for FY 2026 include the initiation of full-scale radar component and material development, continued communications infrastructure build-out, software development, and the establishment of a systems integration laboratory. The program will also continue model-based systems engineering and begin implementation of cybersecurity risk management frameworks.

The acquisition strategy for TACMOR is managed by the Air Force Life Cycle Management Center (AFLCMC) and leverages a rapid prototyping Middle Tier Acquisition approach to expedite development and fielding. The program element also includes funding for necessary civilian pay expenses to support program management and execution. The Over-the-Horizon Backscatter Radar program is positioned to deliver critical early warning and surveillance capabilities to address evolving threats and support the defense of U.S. and allied interests in both the Indo-Pacific and North American regions.