Since the late 19th century, human beings have been harnessing an invisible energy source capable of powering, sustaining, and protecting our society. It fuels our inventions and our economy, helps to detect and treat our most serious illnesses, and provides the ultimate guarantee of our way of life.
And yet, in public consciousness at least, nuclear science remains more feared than it is celebrated — its hazards much more readily imagined than its benefits. Balancing these risks and rewards is left to the few that understand it — their work largely cloaked by the veil of secrecy, or obscured by uneasy and often unintentional myth.
Among this community are the people of the National Nuclear Security Administration (NNSA), whose work is critical to enabling American society to reap the benefits of nuclear science, while remaining safe from its most destructive potential.
Part of that duty is responding to incidents involving nuclear or radioactive material, and this highly specialized role is the domain of the Nuclear Emergency Support Team (NEST), primarily made up of people who work elsewhere in government, but who bring their skills to bear to avoid a nuclear catastrophe, or respond to one should it happen.
While their existence isn’t a secret, their role is not well understood. Their small fleet of five aircraft — dubbed the Aerial Measuring System (AMS) — comprises three Beechcraft King Air 350 fixed-wing aircraft and two Leonardo AW139s.
Additionally, AMS offers a complementary capability with a fleet of U.S. Customs and Border Protection P-3 Orion fixed-wing aircraft and two Airbus BK117 rotary-wing aircraft, providing additional resources.
And while the AMS team are always on standby to respond to the kinds of disasters that the public most fear, the majority of their efforts to keep the public safe are routine patrols which take place year-round.
Super critical mission
“NEST is an umbrella term that captures a variety of nuclear emergency response assets that are part of the Department of Energy National Nuclear Security Administration’s portfolio for responding to any nuclear or radiological emergency,” explained Mark Norsworthy.
Norsworthy is the AMS program manager at the Remote Sensing Laboratory (RSL), facilities under the authority of the Nevada National Security Sites which develop the technical means to support NEST activities.
Having earned a bachelor’s degree in nuclear engineering, Norsworthy achieved his PhD in the same subject at the University of Michigan before applying for a job at the RSL at Nellis Air Force Base. He has been there for seven years.
“I realized that you could have a job where you can combine radiation science, emergency response, and service to the country,” he said. “That sounded perfect to me.”
As well as the RSL based at Nellis, there is another at Joint Base Andrews in Maryland, and it is from these bases that the AMS operates its aircraft.
The complementary capability of AMS combines subject matter experts from the Radiological Assistance Program Region 3 with their radiological detection equipment and aircraft from U.S. Customs and Border Protection and the DOE’s Savannah River Site. This capability is based at Cecil Airport in Florida and the Savannah River Site, respectively.
Born from the Aerial Radiological Measuring System, which supported atmospheric and underground testing of nuclear explosions by monitoring radiation levels, the AMS mission has evolved to provide real-time information to decision-makers during radiological incidents, such as the Three Mile Island accident in 1979.
In fact, their equipment and expertise were crucial to inform both U.S. and Japanese leadership in the aftermath of the Fukushima Daiichi nuclear accident in March 2011.
“Our five aircraft are divided between Nellis and Andrews, so we can cover the whole country as quickly as possible in the event of a release or an emergency,” Norsworthy said. “But AMS also provides support for what we call preventive radiological nuclear detection.”
Preventive detection involves AMS crews flying to search for anomalies that might indicate the presence of anything of a nuclear or radiological nature that might pose a hazard to the public. This could include lost radioactive material, or in the worst-case, evidence of an intended nuclear or radiological terrorist attack.
“Primarily what we’re looking for are gamma rays,” explained Norsworthy, referring to the hazardously energetic waves of electromagnetic radiation that are released from unstable atoms as they decay. “In the detectors are crystals. If a gamma ray deposits energy in the crystal, it makes a little flash of light and by counting the flashes and how bright they are, we can get some information about what the radioactivity was on the ground, what the radio isotopes were, and how strong and hot they are.”
But the data itself is only half of the equation. While the sensors on board the aircraft continuously collect it, RSL’s own in-house software converts it into products that give it context and meaning, both to the crew and others who might need to act based upon it.
“Mostly what we’re trying to do is identify, localize, and map the radiation that’s on the ground,” Norsworthy said. “The main challenge scientifically for AMS is that we also try to quantify it, so not just tell you where it is, but also how much is there. That last bit is what really helps decision-makers know what they should do about it.”
But just because AMS aircraft are flying, it doesn’t mean they are looking for something dangerous. In common with many other wide area security measures, a sound understanding of what normal looks like is essential if you are to spot anything that is out of place.
“Before very large events or very high-profile events, we will go and gather a baseline radiation map of the area before the event happens,” explained Mike Toland, a pilot and the aviation operations program manager for NEST AMS. “We’ll go make sure everything that’s there is supposed to be there before an event, and then if we measure something during the actual event that doesn’t match the baseline maps, there could be somebody trying to bring something nefarious in.”
While gamma and neutron sources are thankfully rare in household appliances, there are still a surprising number of everyday items that emit those types of radiation.
“Radioactive sources are much more common than most people are aware,” Norsworthy said. “Soil density gauges, concrete density gauges, medical sources, hospitals, and so we can measure all that and we rule those things out as not a threat.”
To gather that data, the AMS aircraft are equipped with a suite of sensitive instruments designed to detect specific types of radiation. They can pinpoint the exact source of the radiation, rather than “sniffing” the air for particles.
“We fly with gamma ray detectors and neutron detectors,” Norsworthy explained. “We’re not doing air sampling. We are measuring radiation that’s on the ground, and that requires us to fly low and slow, because if you’re too high, there’s too much shielding between you and the source.”
Precision navigation
Those low-level flight profiles demand a lot from both the aircraft and their crew, as AMS chief pilot Alex Brid explained.
“We have to fly very tight lines, so 300-foot [90-meter] line spacing, 150 ft. [45 m] above the ground. We’ve done missions as low as 50 ft. [15 m] before,” he said. “If we fly too high, we may not find what we’re looking for.”
With those tolerances, there is little margin for error — particularly since the crews often don’t know if there is anything untoward there to find. Given that they are often surveying built-up areas, the risk of collision with the ground or obstacles is ever-present. But the risk of incorrectly positioning the detectors, either vertically or horizontally, could potentially result in them missing something that poses a threat to the public. To avoid this, the pilots must maintain a precise lateral track, as well as a specific height above undulating terrain.
“We use an agricultural system that the crop sprayers use to fly the line,” Brid said. “And we try to stay within 25 ft. [eight meters] of center line, preferably 10, while maintaining a constant velocity above ground.”
While their fixed-wing fleet are capable of covering long distances relatively quickly to get to the search area, it is the AMS helicopter fleet that provide the highest levels of fidelity. This means that the King Airs would likely be the first airborne in the event of an emergency, but it’s the helicopters that are often preferred for precise data.
“If there were a [radiological] release somewhere, the King Air would probably respond first because it’ll get there quick,” Norsworthy said. “But it doesn’t carry as many detectors, and it flies a little bit higher. You can get good data, but not quite the same fidelity of data that you can get with the helicopter.”
Given the need to fly to such tight tolerances over long patrol periods, it might be tempting to assume that flight control automation was the reason that 2024 saw AMS replace its previous Bell 412 helicopters with a pair of Leonardo AW139s. In fact, the decision was driven by a much broader range of considerations, including the requirements of the scientific crew in the cabin.
“We wrote out the specifications that we wanted, and several companies bid,” Norsworthy said. “Ultimately, we selected the Leonardo AW139 because it’s faster and can fly for longer. And it has climate control, which is actually a big improvement for the human factors.”
In addition to cockpit comfort, another improvement that helicopter pilots will rarely turn down is more power. And while this might not seem like a high priority for most survey missions, the AMS task is again a little different.
“The longer we can dwell over something that we’re interested in, the better quality the data is going to be,” Toland explained. “In the 412, we would not hover out of ground effect in case you lost an engine, but in the 139, we can. We can also carry a lot more weight, which means we’ve added about 50 percent more detectors and that means better quality imaging.”
Having a helicopter capable of flying with the precision required for the NEST mission is one thing. Finding pilots that can do it over extended patrol durations is quite another.
“It’s like flying the final part of an instrument approach for hours on end,” Brid said. “And since this is a very fatiguing job, you have to be able to do your job from either seat.”
While the aircraft commander will always have primacy over mission decision-making, both pilots share the duties of pilot flying and pilot not flying.
Strong interaction
“One pilot will be concentrating on maintaining the centerline, and the other pilot will be monitoring the aircraft instruments — looking out for obstacles, at the map and navigating, and communicating with outside agencies,” Brid said. “One pilot will fly a few lines and then the other pilot will fly, so it shares the workload. Once the [pilot flying] transfers controls of the aircraft, the roles instantly get switched.”
Operating to such a high degree of accuracy and reliability, and in such a fluid crew regime, demands a particular set of skills and experience that require years to develop. At these heights, all crewmembers must operate with absolute trust in one another. They must also remain vigilant to deviations or error, either their own or by other crewmembers, and have the temperament to accept guidance whatever their experience level or position in the crew.
“CRM is integral to our operations,” Brid said. “Finding pilots is a tricky aspect for us.”
It isn’t only a unique combination of interpersonal competencies that the NNSA require from their pilots, but also the qualifications to fly any of their aircraft.
“We’re looking for pilots who are dual rated, who are commercial pilots of both fixed-wing and helicopters,” Brid explained. “So, we’re looking for pilots who aren’t there to build hours. All our pilots have senior levels of experience, and this is the job they want to be in for pretty much the rest of their careers.”
When NEST sets out to recruit new AMS pilots, they require at least 1,500 hours total, with a minimum of 500 hours each in airplanes and helicopters. From that pool, NEST selects those that fit in with what is a very select group.
“Each unit has about five to six pilots, so we have to have people who fit in very well with the group,” Brid said. “And since part of our job is to be on standby, you have to be within two hours of location, so I have to find guys who are willing to move to either Nellis or Andrews.”
Once they have been successfully selected, it can take pilots up to a year to qualify as commander on both aircraft types. In a process that Brid described as “crawl, walk, run,” nothing is assumed. Once qualified, they will be expected to lead their small teams during both the everyday, and potentially, their country’s worst day.
While the crews are explicit that the presence of their aircraft doesn’t herald a disaster, the specter of an invisible and lethal threat is a hard one to shake, despite the NNSA’s transparency.
“We’re making a large effort to spread the word about who we are, because people have a lot of misconceptions about what it is that we do,” Toland said. “We’re [trying to] make sure the public understands that this capability exists, and that we’re going to be the folks to go and help fix the problem.”
The misconceptions may prove difficult to overcome, given that the portrayal of nuclear science in pop culture is often relegated to the status of being a MacGuffin for an action movie, or a justification for the supernatural.
“When I started my pilot career, I had no idea I was going to be able to fly with such educated and knowledgeable emergency responders,” Toland said. “Before I applied for this job, I had no idea that this asset even existed, but it comforts me to know that this is something that our government thought was important enough to make.”