AN/TPS-71 (ROTHR)

The AN/TPS-71 Relocatable Over-The-Horizon Radar (ROTHR) is a tactical, land-based, bistatic ionospheric backscatter radar operating in the HF frequency band (5 to 28 MHz). Manufactured by Raytheon E-Systems, this early warning radar is designed for wide-area over-the-horizon surveillance and tracking of both aircraft and ships, supporting tactical forces in areas of national interest. The system can be configured for general surveillance, spotlighting specific regions for targets of interest, or assessing the size of an attacking force. Its relocatable components include the transmit and receive shelters and the operational control center, which are designed for transport by land, sea, or air, though the transmit and receive antennas require pre-prepared sites. ROTHR continuously adapts to changing ionospheric conditions using co-located Quasi-Vertical Incidence (QVI) and backscatter sounders for propagation management. The system comprises three distinct elements: a transmit site, a receive site, and an operations control center. The transmit and receive sites are separated by 92 to 185 km (50 to 100 nautical miles). The transmit site provides 200 kW of solid-state power, illuminating a 64-degree sector with a range from 926 to 2,963 km. Range resolution is achieved by transmitting a 25-kHz continuous frequency-modulated waveform. The receive subsystem, featuring a 2.58 km (approximately 2 miles) array of 372 twin-monopole elements, digitally processes returned beams, performs range and Doppler processing, and extracts target detections. The operations control center, which can be co-located or remotely linked via satellite, processes target information and allows operators to interface with the largely automatic system, with manual override capability.

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