Analysis of information sources in references of the Wikipedia article "Systems Tool Kit" in English language version.
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.
Since the trajectories of classified satellites are not published by the Department of Defense, Langbroek had to rely on orbit data collected by a global network of amateur spy-satellite hunters. This community obsessively documents the movements of classified objects in space, often using little more than binoculars, a stopwatch, and a basic knowledge of orbital mechanics. But despite the low-tech observation techniques, their predictions of satellite movements are often accurate to within a few seconds. ... This is the first time in three and a half decades that an image has become public that reveals the sophistication of US spy satellites in orbit.
