Amateurs identify U.S. spy satellite behind Trump's Iran tweet

But 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 the future. “Using math to calculate an orbit is really easy,” he says.

Thompson was one of the first to use an amateur-curated database of known satellites to point the finger at USA 224. He showed that it flew over the Iranian space center shortly after the accident.

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.