"I could see something I recognized as a missile trailer and something seemed suspicious, so I asked the airman to zoom in," Duff recalled five decades later. "It was then that I saw clearly on one trailer a partially uncovered missile. I identified it and confirmed it as a Soviet MRBM [Medium Range Ballistic Missile]."
The photograph had been taken by a U-2 reconnaissance plane during a flight over Cuba less than 24 hours earlier. The Cold War and the Cuban Missile Crisis were building to a crescendo.
Duff's discovery of an actual missile on the ground within range of major U.S. cities like Miami, Atlanta, Dallas, New Orleans and even Washington, D.C., pushed the possibility of World War III to its closest point ever, then or since, according to many historians. The crisis is also widely recognized as bringing the planet to the brink of nuclear war.
'Never a more dangerous time' • When Robert King entered the Air Force photo intelligence school in 1971, the story of Duff's discovery was well-known.
"It was the biggest single event that ever happened in photo interpretation in the Air Force, or the entire federal infrastructure for that matter," said King, a Salt Lake City resident who was eventually assigned to the renamed 544th Aerospace Reconnaissance Technical Wing. "There was never a more dangerous time."
Spotting the nose cone of the Russian missile in October 1962 brought mixed emotions for Duff, who moved into a career as a fisheries biologist in the West and Utah after completing military duties and now splits his time between the remote towns of Callao in Juab County and Baker, Nev.
He was proud to have done his job as he was trained, but it wasn't until a few days later when he realized the magnitude of the discovery.
"I slapped the airman on the back and said, 'This is what we have been looking for. Good job, guys,' " Duff recalled.
"It was pretty exciting, but we immediately returned to our work of poring over photographs looking for more missiles and more launch sites. I didn't really have an idea of what the rest of the military was doing."
It wasn't until President John F. Kennedy's speech to the nation on Oct. 22 that the cold reality set in for Duff and his fellow airmen.
Kennedy did not mince his words and laid the facts out from the start of his speech.
"This government, as promised, has maintained the closest surveillance of the Soviet military buildup on the island of Cuba. Within the past week, unmistakable evidence has established the fact that a series of offensive missile sites is now in preparation on that imprisoned island. The purpose of these bases can be none other than to provide a nuclear strike capability against the Western Hemisphere," Kennedy said, according to the John F. Kennedy Presidential Library and Museum.
Media and Hollywood have given credit for that initial missile confirmation to the Central Intelligence Agency, but Duff said Air Force commanders alerted Kennedy to the discovery "before dawn" on Oct. 15; the CIA did not "confirm" its finding of the missile until 14 hours later.
"During my era, and I assume it was the same during the Cuban Missile Crisis, at least two agencies looked at the same film," King said. "There was a spirit of rivalry. It was a big deal to find something the other guys had missed. It was good. It kept everybody competitive and looking in the shadows for everything."
Less than a week after Kennedy's speech to the nation, the crisis was resolved with Russia publicly agreeing to remove the missiles from Cuba and the U.S. pledging to not invade Cuba. History would later reveal a separate, secret agreement by the U.S. to remove its nuclear missiles from Turkey.
A signature life • Prior to his enlistment into the Air Force, Duff, a native of Washington, D.C., worked as a seasonal employee for the U.S. Forest Service and attended the University of Minnesota for one year. He wasn't sure he was ready for a second year of college.
"I felt that I owed my country something, and I had relatives who had served, so I decided to do my duty and I enlisted in 1959," Duff said.
He originally wanted to serve as an air/sea rescue medic but instead decided to specialize in photo interpretation, which taught him identifying "signatures" of fuel dumps, missile launching sites, missile trailers and, of course, missiles.
"I thought it might be a chance to get up in the air, and I was interested in photography," he said.
After basic training and six months of school, Duff, along with many of those in his graduating class, was assigned to the 544th Reconnaissance Group at Offutt Air Force Base where he made his historic, middle-of-the-night discovery in 1962.
Later that year, he had fulfilled his duties to the Air Force and decided to head west.
By the fall of 1963 Duff found himself living in Logan, working on a degree in wildlife and fisheries management at Utah State University. He spent his summers as a Forest Service fire guard for the Stansbury, Onaqui and Sheeprock mountains in an area in western Utah known as the West Desert.
Graduating in 1966, Duff landed his first job with the U.S. Fish and Wildlife Service in Sacramento. He eventually returned to the Forest Service working as a fisheries and wildlife biologist first in New Mexico and then Montana.
Duff returned to Utah in the fall of 1972 when he took a job as one of the first fisheries biologists for the Bureau of Land Management.
It was then that the former airman used skills he developed as a photo interpreter during the Cold War to find fish populations previously believed to have been extinct.
"It was a little different, but I did employ the same thinking about how to identify signatures on the ground that could help me find potential fish populations," he said.
Duff even used some of his remaining top-secret military clearance to view U-2 flight imagery to identify riparian habitats along Utah waterways where remnant groups of native fish might be hiding.
His efforts paid off in the mid-1970s when Duff found a small population of genetically pure Bonneville cutthroat trout in a remote creek in the Deep Creek Mountains.
He was rewarded again, stumbling across an unexpected pure strain population of Lahontan cutthroat in the Pilot Mountains of northwestern Utah.
The significance of Duff's findings, while not outwardly comparable, does have some similarities, at least in the methods of their discoveries.
"The military training taught me to look for signatures and to come up with a plan of alternatives to find out the course of action to take and how to do it," he said. "It taught me to be thorough and persistent. The scientific community had written off those fish as extinct. I was determined to find them, in both cases, and I felt a great accomplishment when I did."
Fifty years later • Now, as the 50th anniversary of the Cuban Missile Crisis nears, Duff still clearly remembers his service with his fellow photo interpreters and their role in those tense, fateful days in October 1962.
While there were other memorable moments during his military career, he said, nothing equaled his discovery in that underground bunker.
"I kind of knew the cities of Russia [from aerial maps] like I now know the streets of Salt Lake City," Duff said.
"I felt like I was doing a good service to my country in trying to find out the nuclear capability of a threatening nation."