David Schmerler, part of a team at the James Martin Center for Nonproliferation Studies, goes by the nickname “Geolocation Jesus” because of his skills at pinpointing North Korean locations using far-ranging clues, such as Kim Jong Un’s public schedule, the number of skylights in a photographed room, Google Earth, and his knowledge gleaned from watching every North Korean missile propaganda video ever released. Frank Pabian, who works closely on a Stanford University team led by former Los Alamos Laboratory Director Siegfried Hecker, is one of the world’s leading imagery analysts and a former American weapons inspector. Then there’s Jacob Bogle, a coin dealer by day and North Korean mapping hobbyist by night who has created one of the world’s most detailed maps of North Korea from his home in Murfreesboro, Tennessee. In my own research, I’ve found 17 major groups or players actively tracking illicit nuclear activities around the world.

Not all of the work generated by this wide-ranging ecosystem is accurate, but much of it is pathbreaking. And all of it is unclassified.

Read: The threat of threat assessments

For decades, the governments of great powers—and especially the United States—had cornered the satellite market, for good reason: Operating anything in space was technically demanding and inordinately expensive. The CORONA satellite, a project of the CIA and the U.S. Air Force, was the first to photograph large swaths of the planet in 1960, returning its film in a capsule that had to be parachuted down to Earth and captured in midair over the Pacific Ocean to be developed. The engineering challenge was so punishing that CORONA’s first 13 missions failed. But on the 14th attempt, it hit pay dirt, photographing more Soviet territory than all previous U-2 spy-plane flights combined. According to Albert Wheelon, the CIA’s first deputy director of science and technology, “It was as if an enormous floodlight had been turned on in a darkened warehouse.” The Soviets soon launched their own photoreconaissance satellite, Zenit-2, in 1962. It, too, was expensive and failed repeatedly before it finally returned usable imagery.

Since the early 2000s, however, commercial satellites have become common. According to the 2019 threat assessment issued by the Office of the Director of National Intelligence, the annual number of satellite launches has quadrupled in the past five years. In a single launch last year, the private firm SpaceX sent 64 small satellites from 17 countries, and a Florida middle school, into space. News reports note that in 2018 alone, 322 small satellites the size of a shoebox were hurled into orbit, and some analysts estimate that more than 8,000 small satellites will be launched in the next decade.

Spy satellites still offer better resolutions and capabilities. But today’s commercial satellites are narrowing the gap, offering image resolutions that are roughly 900 percent better than what they were just 15 years ago—sharp enough to distinguish different types of cars driving along a road and capture certain indicators of equipment used in nuclear-weapons programs. What’s more, constellations of small satellites can fly over the same location multiple times a day, identifying changes on the ground in near–real time. Already, a San Francisco start-up called Planet has more than 150 satellites in orbit. Seattle-based BlackSky, which launched in 2013, has 60 satellites and says it flies over major cities 40 to 70 times a day. Perhaps most important, the costs of acquiring satellite imagery have plummeted—just as computing and communication power has been radically democratized.