The U.S. military has successfully demonstrated a new lower-cost receiver that could form part of a future over-the-horizon (OTH) radar. The testing also raises the question of whether the High Frequency Active Auroral Research Program (HAARP) research site in Alaska, which the U.S. Air Force transferred away more than a decade ago, could be repurposed for operational use in this role. A new radar of this kind would help the United States plug critical gaps in surveillance coverage over the ever-more strategic Arctic region. Canada is notably already pursuing a multi-billion-dollar OTH radar project in cooperation with Australia for this exact purpose.
The U.S. military put out a press release yesterday regarding the testing of the newly developed receiver array, which occurred between September 7 and September 11. This was the culmination of a series of “Arctic air domain awareness” experiments conducted cooperatively by U.S. and Canadian authorities over the past three years.
The final round of experimentation last month “examined whether an existing high-frequency transmitter [HAARP], paired with a newly developed, low-cost [16-element high-frequency] receiver array, could detect aircraft beyond the coverage of current long-range radar sites,” according to the release. “The effort focused on improving awareness across a region where vast distances, harsh weather and limited infrastructure present challenges for air surveillance.”
“Researchers used the University of Alaska Fairbanks’ High Frequency Active Auroral Research Program [HAARP] facility and a receiver array in Cold Bay developed by MITRE to collect data on participating aircraft over the Gulf of Alaska and Bering Sea,” the release added. “MITRE also supported the effort throughout the three-year experiment series and designed and executed the field experiment in partnership with government, scientific, and operational participants.”
The remote HAARP site was built in the 1990s as part of a joint U.S. Air Force and U.S. Navy effort. The Defense Advanced Research Projects Agency (DARPA) was also involved. The central component of the 33-acre facility is an array of 180 crossed-dipole antennas, which can transmit up to 3.6 megawatts of radio frequency energy, according to the Air Force.
The primary purpose of HAARP was to provide U.S. government and independent researchers with a state-of-the-art facility to explore ionospheric phenomena. On the U.S. military side, work was focused on improving long-range surveillance and communications capabilities, including ways to communicate with submerged submarines. Over the years, HAARP has also been the subject of several entirely unsubstantiated conspiracy theories.
In 2014, the U.S. Air Force announced that it would shutter the HAARP site and dismantle it. However, the following year, the decision was instead made to transfer it to the University of Alaska Fairbanks, which has continued to operate it as a civilian research facility.
“During an experimental air domain awareness initiative, HAARP served as a high-power illuminator, transmitting signals toward the ionosphere to support the detection of airborne targets over Alaska’s maritime approaches,” according to the captions of several pictures that accompanied the release yesterday. “The experiment evaluated bistatic over-the-horizon detection methods to explore potential improvements in long-range surveillance and air domain awareness across Alaska’s maritime approaches.”
The most common types of OTH radars are so-called ‘skywave’ or ‘backscatter’ designs. They usually consist of two large and geographically separated arrays of antennas. The ‘illuminator’ array pumps out signals that are bounced off the ionosphere, the ionized layer of Earth’s upper atmosphere, at a specific angle so that they return to the ‘receiver’ array. Objects of interest (in the air and/or on the surface depending on the specific configuration) are detected in the process. As TWZ has previously written:
“Commonly, radars are limited by line of sight due to the curvature of the Earth in relation to the altitude they are operating at. OTHRs overcome this critical limitation, but with some major drawbacks.”
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“While they offer much lower fidelity than many of their line-of-sight counterparts in most cases, they make up for it in huge range, hundreds of miles to thousands of miles (1,500 miles is common, for instance, for powerful military sky wave/backscatter OTHR systems) and a large coverage area. The sky wave type of OTHRs achieve this by bouncing their radio waves off the ionosphere to a coverage area where they hit targets and return the same way to the receiving station. The angle at which the radio waves hit the ionosphere dictates the range, and that angle is limited to a specific envelope or the waves won’t properly bounce back toward Earth. As such, placing the radar in the right place in relation to the targeted surveillance area or areas, to begin with, is key.”
In the testing last month, Air Force E-3 Sentry Airborne Warning and Control System (AWACS) radar planes, HC-130J Combat King II rescue aircraft, and KC-135 aerial refueling tankers “served as cooperative targets, providing known positions against which researchers could compare the experimental data,” according to the official release. “The team successfully completed testing, meeting or exceeding its test execution objectives. Initial results show the system was successfully able to achieve full skywave (beyond line of sight) detections of aircraft and correlation to truth flights. Thorough data analysis is ongoing.”
The release also says that the tests “explored how existing infrastructure and emerging technology could complement current surveillance capabilities.” This raises the possibility that the HAARP site, specifically, might be utilized as part of a new OTH radar. Whether or not this is actually under consideration is still unclear, and TWZ has reached out for more information.
Regardless, OTH radars have been experiencing something of a renaissance in recent years in the United States and elsewhere globally. Separate reports just in the past day or so have highlighted what appears to be significant progress on at least one part of a long-planned OTH radar in Russia’s Kaliningrad enclave.
Outside of Alaska, the U.S. military has been working to establish a Tactical Mobile Over-the-Horizon Radar (TACMOR) site in the South Pacific archipelago nation of Palau. The originally stated goal had been to finish work on this facility in 2026, but the project has faced legal challenges.
As already mentioned, OTH radars have also been part of U.S. plans to improve surveillance coverage in the Arctic. Like the recent testing in Alaska, there has been significant cooperation with Canada in this regard over the years, including through the U.S.-Canadian North American Aerospace Defense Command (NORAD).
Today, NORAD relies heavily on a network of ground-based radars called the North Warning System (NWS) to provide aerial surveillance coverage in the High North. The radars that make up the NWS are also all pointed northward, and none of them provide the kind of wide-area long-range coverage that an OTH design would offer.
The NWS reflects a long-standing focus on monitoring for aerial threats heading across the North Pole toward North America, especially possible nuclear strikes from Russia (and the Soviet Union before it). However, new avenues for geostrategic competition in the Arctic with Russia, as well as China, over natural resources, from oil and natural gas to fish and other sealife, as well as trade routes have emerged in recent years amid receding ice and other impacts of global climate change. This, in turn, has only prompted growing demand for surveillance coverage.
“We need a layered sensing grid, from [the] seafloor to the space layer. And we have no choice. It has to be layered and deep, a defense in depth, from a sensing point of view,” Royal Canadian Air Force (RCAF) Maj. Gen. Chris McKenna, head of 1 Canadian Air Division and the Canadian NORAD Region, also said during a panel discussion at the Air & Space Forces Association’s (AFA) annual Warfare Symposium in 2025, at which TWZ was in attendance. “And I will say I suffer from an insufficiency of ISR [intelligence, surveillance, and reconnaissance] in the Arctic on a daily basis. And I am fighting for information.”
McKenna was responding at the time to a direct question about gaps in so-called “domain awareness” in and around the Arctic and how to address them.
“I think there’s an importance here of not just air domain, but also space domain, and having a sufficiency of ISR in the Arctic to actually build you the [domain awareness] picture,” he added. “I haven’t really touched on over-the-horizon radar, but I certainly can get into it. I think that’s a really important capability given the austerity of the Arctic and the need for it to cue other things.”
For its part, Canada is now building its own new Arctic Over The Horizon Radar (A-OTHR), at an estimated cost of more than $4 billion. In an announcement last year that caught many off guard, the Canadian government announced that it would be leveraging technology originally developed for Australia’s Jindalee Operational Radar Network (JORN) to support this development. It is also important to note here that relations between Canadian authorities and the Trump administration have been and continue to be heavily strained over a variety of issues, which has prompted broad concerns about future defense and security cooperation.
Back in the United States, OTH radar plans are also now tied in with the broader Golden Dome air and missile defense initiative. Golden Dome is seeking to establish new layers of defense around the U.S. homeland against a wide array of threat types, and puts major emphasis on new space-based sensor and interceptor capabilities. Expanded defensive architectures within the Earth’s atmosphere are also part of this plan.
“Adversaries are developing and building advanced nuclear and conventional delivery capabilities,” U.S. Army Lt. Gen. Joseph Jarrard, Vice Commander of the U.S. element of NORAD and Deputy Commander of U.S. Northern Command (NORTHCOM), warned at the annual Space & Missile Defense (SMD) Symposium in August. This includes “cruise, hypersonic, and ballistic missiles, as well as fractional orbital bombardment systems, or FOBS, to threaten not only Alaska and Hawaii, but the entire continent of the United States.”
Chinese hypersonic and other developments, in particular, enable new modes of attack that “can approach North America from the south, rather than the traditional northerly vector for which our legacy early warning radars were designed,” Jarrard continued. “The Chinese have also been building a conventionally-armed ICBM [intercontinental ballistic missile] equipped with hypersonic glide vehicles that can range [sic] targets throughout Alaska, providing Chinese leaders strike options against our homeland below the nuclear threshold.”
“Russia’s advanced missiles, like the nuclear-armed Avangard hypersonic glide vehicle, are designed to circumvent the ground-based radars used by NORAD and NORTHCOM to detect and characterize an inbound threat, and challenge the ability to provide threat warning and attack assessment,” he added.
New OTH radars positioned in Alaska and elsewhere in the Pacific will not be able to address all of these threat developments alone. At the same time, the recent testing leveraging the HAARP site is another step toward meeting demands for sorely needed expanded long-range radar coverage in the Arctic.
Contact the author: joe@twz.com
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