The Department of Defense awarded a $118 million contract for the construction of a radar station in Palau. Palau, a country in the Pacific about 800 miles from Guam and approximately 1,000 miles southeast Manila is home to the Tactical Mobile Over-the-Horizon Radar. The Tactical Mobile Over-the-Horizon Radar will be located there by 2026. This new sensor is something the military has been keeping very quiet about.
In December’s announcement, only concrete foundations were mentioned. Tactical Mobile Over-the-Horizon Radar (or TACMOR) was mentioned in a February 2018 budget document. It “will support maritime domain awareness requirements and air domain awareness over the Western Pacific region.” This project will show a smaller over-the-horizon radar, or OTHR (sub-scaled), that’s one-quarter the size of traditional. [Over The Horizon] systems.”
As outlined above, the installation will include two locations. The first will be located along the northern isthmus Babeldaob which is Palau’s largest island. One will be along a northern isthmus of Babeldaob, the largest island in Palau. The second one will be located on Angaur (an island approximately 60 miles to the south). Both sites must have communication between them. This suggests that there could be one connected sensor array. Site schematics depict Babeldaob as a transmitter site and Angaur, as a receive site.
According to the Department of Defense, documents and general US policy suggest that the west Pacific could be a future battleground. Guam is a US territory that has been in the hands of the United States ever since 1898’s Spanish American War. It houses often bombers, which could be used to fly to North Korea and China. The Pacific’s vast ocean presents a major challenge. It is essential to be able track and destroy enemy forces in order to win any war.
Over-the-horizon radar is driven by the desire to look beyond in order to fight better.
Beyond the line of sight
While radar can see far away, it is limited by the laws of physics that waves travel in straight lines. Radio waves must hit objects in direct lines from the point they emanate to return the signal. The difference between the distance it traveled and its destination is called the signal. Radar is useful in tracking aircrafts that travel high above ground. It can be used to detect them at greater distances without having the Earth’s curve interfere. This is why radar installation are usually mounted higher than the ground. Every few feet increases its ability to see further.
Early research into over-the-horizon radars was driven by the Cold War. These were deployed to monitor for possible bomber and missile attacks. How do they work in practice?
Duga is a Soviet-era over-the-horizon receiver that was constructed outside Chernobyl in Ukraine. The ionosphere would allow shortwave radio signals from southern Ukraine to bounce off, which would enable them to travel further and be detected at Duga. Radio hobbyists from the United States called it “woodpecker”, because the Soviet radar signal was easily heard over shortwave radios.
A second way to send radar above the horizon to the surface is by using low-frequency signals that are sent along the surface and let diffraction transport the waves further. The range of this surface radar is hundreds of kilometers. Techniques bouncing off of the ionosphere are capable of detecting the entire world from thousands of miles away.
The distance between Duga receiver and transmitter sites in Ukraine is more than 300 miles. The tactical over-the horizon radar in Palau will be able to transmit and receive signals at a distance of approximately one-sixth that. If TACMOR was built using similar principles, the distance between receiving and sending might indicate a shorter range of surveillance. Duga was created to alert of potential nuclear launch. Instead, the TACMOR site will track other threats on a different scale.
See the sea
TACMOR seems to be designed for a role that is different from the Cold War’s over-the-horizon radars. TACMOR, instead of scanning for signs of nuclear oblivion in the area, will monitor movements and track them. It will presumably cost a fraction of what it would take to deploy crewed aircraft and ships to do the same thing.
“An updated OTHR [over-the-horizon radar] The Palau system will allow for space-based as well as terrestrial-based sensors and weapons systems to detect and warn of potential incoming hypersonic weapon, cruise missiles and ballistic missiles. It also can be used to monitor enemy aircraft and ships. “OTHR permits for the continuous monitoring of certain areas, something that may otherwise be impossible with many radar systems deployed forward over large areas on the ground and in the air.
The Department of Defense can increase its knowledge of large swathes of ocean in Palau and, in turn, monitor important parts of the Pacific by placing the radar system there. The radar should not report anything, but if danger does occur, both the Navy and Air Force will be able to respond quickly with the appropriate warning.