US to build Over the Horizon Radar to surveil the South China Sea

How does Over-the-Horizon Radar work?

Conventionally, there are two types of OTHR that can be deployed, a skywave and a surface wave. Both systems were used during the Cold War era but lost their importance to modern-day radars, which are highly sensitive within their ranges.

With changing geopolitical situations and advances in computing capabilities, the OTHR is set to make a comeback as it can address the limitations of range in current radars. The range for OTHRs can extend into thousands of miles as it consists of an extensive array of antennae spread out over an area, with the transmission and receiving equipment placed geographically away from each other.

The skywave type of OTHR works by bouncing off radio waves in the ionosphere. The radio waves travel to the coverage area and return the same after hitting their targets on the ground. The angle at which these waves hit the ionosphere determines their range; therefore, the radar's placement in relation to the targeted coverage area is important.

The surface wave OTHR uses the conductivity of oceanic waters and the ability of radiowaves to bend around the curvature of the Earth to scan relatively closer areas. Such a system is helpful in tracking ships, low-flying aircraft, and cruise missiles fired below the radar horizon.

Together, the two types of OTHR can be an effective tool to monitor contested areas for adversarial activity, look for signs of hypersonic missiles, ships, and aircraft, and serve as an early warning system, The Drivesaid in its report.

When will it be ready?

The TACMOR initiative has been in the works since 2017 and assumes greater importance as China looks to flex its muscles in the South China Sea, and the threat from North Korea continues to rise.

The U.S. Navy has allocated $118 million for the project, which also includes communication infrastructure that will transmit the data from the OTHR to an off-site operations control center responsible for transmitting the real-time data to U.S. and allied forces, as per mission requirements.

The work on the TACMOr is expected to be completed by 2026.