The image almost certainly came from a satellite known as USA 224, according to Marco Langbroek, a satellite-tracker based in the Netherlands. The satellite was launched by the National Reconnaissance Office in 2011. Almost everything about it remains highly classified, but Langbroek says that based on its size and orbit, most observers believe USA 224 is one of America's multibillion-dollar KH-11 reconnaissance satellites.
"It's basically a very large telescope, not unlike the Hubble Space Telescope," Langbroek says. "But instead of looking up to the stars, it looks down to the earth's surface and makes very detailed images."
A small community of amateur satellite trackers was far more interested in the picture than the words. These individuals use backyard telescopes to watch satellites whizzing across the sky, and they know where most of them are—even classified ones like USA 224. "They're super bright in the sky and are easy to find," says Michael Thompson, a graduate student in astrodynamics at Purdue University who spots satellites in his spare time. Once a satellite is seen, it's relatively easy to work out exactly where it will be at any point in future. "Using math to calculate an orbit is really easy," he says.
Langbroek went further still. He was able to reconstruct the picture taken by USA 224 by matching the obliqueness of the circular launch pad in the image tweeted by Trump. His calculation showed that the photo was taken from the vantage of USA 224. Langbroek and another online researcher, Christiaan Triebert, also used shadows cast by towers around the launch pad as sun dials—allowing them to verify the time at which the photo was taken.
Both techniques suggest the pictures were snapped by USA 224, which flew near the site at 2:14 PM local time. "The match was perfect, basically," Langbroek says.