The Air Force Technical Applications Center (AFTAC) is the intelligence entity that looks for nuclear explosions, although if you are a regular reader you probably know that already.  You probably also know that, even by the standards of the US intelligence community, AFTAC keeps a pretty low profile.

So, imagine my surprise to see the Department of Defense release a pair of long articles based on what appears to be an interview with David O’Brien, AFTAC’s Chief Scientist. (Sensor Network Detects Nuclear Blasts Worldwide and Defense Nuclear Monitoring System Helps in Disasters).

There is a sum total of on book on AFTAC, Charles A. Ziegler and David Jacobson’s Spying Without Spies: Origins of America’s Secret Nuclear Surveillance System (1995).  Writing in the The International History Review, Bill Burr called Spying without Spies outstanding — which is high praise — especially given that AFTAC “zealously guards its internal histories.” To give you a sense of how zealous, AFTAC early efforts to sniff out the first Soviet nuclear test helped give rise to all those silly Roswell conspiracies.  (The National Security archive has a nice collection of historical documents on AFTAC.)

Beyond Spying without Spies, William B. Scott wrote a series of articles in Aviation Leak in 1997 as part of a successful campaign to save at least one Constant Phoenix aircraft.  (The Clinton Administration decided to retire the capability just as it was seeking Senate ratification of the Comprehensive Nuclear Test Ban Treaty or CTBT.  Don’t ask.)  Oh, and there was a nice a article in the Smithsonian’s Air & Space Magazine.  That’s about it, really.  Otherwise, references to AFTAC are usually made only in passing.

O’Brien didn’t cross any lines, but it is still sort of stunning to see it all in one place.  For example, here is a rundown of AFTAC’s assets:

To monitor the atmosphere and space, he said, the U.S. Atomic Energy Detection System, called USAEDS, has sensors aboard more than 20 satellites that make up the Global Positioning System and the infrared-sensing satellites that make up the Defense Support Program.

“The latter,” O’Brien said, “are what the United States uses to detect launches of intercontinental ballistic missiles.”

Multiple sensors on all those satellites “look for phenomenology from a nuclear explosion that occurs in space or in the atmosphere,” he added, “whether it’s nuclear radiation or the flash from the fireball.”

The network’s five hydroacoustic stations detect undersea nuclear explosions.

“Those are just underwater microphones, and they listen for the explosion that goes off underwater,” the scientist said. “By detecting the explosions on more than one underwater microphone, we can triangulate where it occurred.”

But the workhorse since the treaties came into effect to ban atmospheric nuclear testing, O’Brien said, has been the underground nuclear monitoring capability.

“Those sensors are seismic, and the reason they’re seismic is that when a large explosion occurs underground, it creates a signature that looks just like an earthquake,” he said.

Infrasound sensors measure changes in the atmosphere generated by very-low-frequency acoustic waves that can come from above-ground nuclear explosions.

USAEDS still supplements some of its 40 seismic stations with infrasound, the scientist said, and in the 1960s used infrasound as the main way to detect nuclear explosions in the atmosphere.

“But once we were able to get sensors on satellites,” he said, “that gave us a much better capability.”

O’Brien also touched on the relatively capabilities between the Comprehensive Test Ban Treaty Organization (CTBTO) International Monitoring System (IMS) and the classified Atomic Explosion Detection System:

“We participate in all their international meetings, and we have since [the system’s] inception. They occasionally come here and visit,” O’Brien said. “I think both the IMS and ourselves are right at the state of the art of any technology that is practical for use in detecting nuclear explosions.”

It is not surprising the systems are roughly comparable. After all, seismology is an honest-to-goodness science. The only part that might be secret is the location of a station.  And there have been hints that the IMS and USAEDS were not so far apart.  In the early 1990s, the USAEDS monitoring threshold at Lop Nor was about 100 tons in explosive yield.  (This number was not redacted in a CIA report that stated “tests with yields on the order of 100 tons would not be detected seismically [at Lop Nor], even if there were no attempt at evasion [such as decoupling].”) By 2002, though, the National Academies were observing that the IMS could do much better than that, detecting down to tests of about 60 tons at Lop Nor.  That tended to suggest, at least on the issue of seismic detection, that the IMS and the AEDS were roughly comparable, with the latter perhaps having at trick or two up its sleeve.

Anyway, it is good to see more information about AFTAC.  It is a really important national capability that, as the kerfuffle with the Constant Phoenix would suggest, doesn’t get nearly the attention its deserves.

The trio of articles by William B. Scott are: “USAF Nuclear Detectives Assume New Roles,” Aviation Week & Space Technology, November 3, 1997, pp. 50-53; “Sampling Missions Unveiled Nuclear Weapon Secrets,” Aviation Week & Space Technology, November 3, 1997, pp. 54-57; and “Debris Collection Reverts to Ground Sites,” Aviation Week & Space Technology, November 3, 1997, pp. 57-59.

I know, you are thinking: Why isn’t there an AFLAC joke?  Well, what with AFTAC, AFLAC, Gilbert Gottfriend, seismology, earthquakes in Japan and inappropriate jokes, the whole thing is a minefield.  I am not going there.