This 'sniffer plane' is how the U.S. monitors North Korea's nuclear tests

North Korea conducted yet another nuclear test on Sept. 8, and it was seemingly the country's most powerful yet.

Registering some 10 kilotons, according to reports from South Korea, the blast was apparently twice as powerful as the last test in January. Both are significant increases in explosive power from the first North Korean test in October 2006, which U.S. intelligence officials estimated to be around 1 kiloton.

The numbers are hard to verify, but the test -- which registered as a 5.3 magnitude earthquake in the northeast of the country - angered the international community, particularly South Korea, Japan and the U.S., which view the North as a significant threat.

When it comes to finding out exactly what happened, and how far North Korea has progressed in pursuing its unpopular goal, the U.S. has an invaluable asset: the WC-135 aircraft.

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The WC-135 "Constant Phoenix," is a special "sniffer plane" that can detect radiation after a nuclear event. Its use in North Korea was confirmed earlier this year by an anonymous Pentagon official and its deployment following the recent blast was confirmed to Mashable over email on Friday.

"Following the seismic activity and announcement by North Korea of a fifth nuclear test on 9 September local, a WC-135 Constant Phoenix atmospheric collection aircraft is being deployed to the region," said Lori R. Hodge, deputy director of public affairs for the U.S. Pacific Air Forces.

The WC-135 -- which the U.S. Air Force describes as an "atmospheric collection aircraft" -- collects particulate and gaseous effluents and debris from accessible regions of the atmosphere. In other words, it has flown near North Korea, not over it, in order to collect evidence related to the test.

A specially adapted plane based originally on the Boeing 707 commercial jetliner, which has lived on through military aircraft like the EC-135C, it's been modified to allow its crew to detect radioactive clouds in real time.

"This aircraft is designed to collect accurate information on levels of radiation in the atmosphere in order to monitor compliance with international treaties governing nuclear testing, and to provide better understanding of the after-effects of a nuclear incident," Hodge added.

"The aircraft gathers scientific data in international airspace over international waters. For operational security reasons, we do not discuss the specific employment of this aircraft."

The aircraft was deployed in the wake of the Fukushima nuclear disaster in 2011, which occurred as a result of a deadly earthquake and tsunami in Japan.

According to Offutt Air Force Base spokesperson Susan Romano earlier this year, the plane has protection from radioactivity built into it, so that the crew members don't need to wear hazardous material suits.

The plane is operated by crews from the 45th Reconnaissance Squadron at Offutt Air Force Base in Nebraska.

The Constant Phoenix monitoring program dates back to 1947, when General Dwight D. Eisenhower called on the Army Air Force to detect atomic explosions worldwide.

A WB-29 flying between Alaska and Japan detected nuclear debris from Russia's first atomic test, the Air Force says. The WC-135s replaced the WB-29a in the mid-1960s, and the planes have since sampled air over several seas and oceans from pole to pole.

Despite dating back to the Cold War-era, in an uncertain 2016, they continue to be as vital as ever.