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

To help keep an eye on the South China Sea region.
Ameya Paleja
US Navy Over-the-Horizon Radar
US Navy Over-the-Horizon Radar

U.S. Navy 

The U.S. Navy recently approved a contract for the construction of reinforced concrete pads and foundations for installing a tactical Over-the-Horizon Radar (OTHR) on the Republic of Palau, the Department of Defense (DoD) said in a press release about awarded contracts.

The Republic of Palau is an archipelago of over 500 islands covering 177 square miles (459 sq km). With a population of just over 18,000 people, the country has a military relationship with the U.S., per the 1994 Compacts of Free Association (COFA) agreement.

The U.S. military uses the Palau islands for a range of military exercises. Last year's exercises featured the Patriot Missile Defense system, the most advanced air defense equipment in the U.S. arsenal. The U.S. island territory of Guam is located about 800 miles (1,295 km) away from Palau, and installing a Tactical Mobile Over-the-Horizon Radar, or TACMOR in the region will increase the surveillance capabilities of the U.S. forces in the area manifold.

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.

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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 Drive said 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.

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