Spysats can’t hide from determined amateur spacecraft trackers: Backyard Detectives Out-Spy the Spies Orbiting Above – WIRED
Even spy satellites can’t hide from a civilian with a pair of binoculars and a lot of free time. “It’s hard to hide something that you can see in the sky,” says John Magliacane, an amateur radio operator and satellite tracker in New Jersey. Just like the moon, satellites reflect sunlight back to Earth. Magliacane is a satellite tracker, but not one of the smaller sub-group that tracks spy satellites. However, he did end up doing some similar stuff during the era of space shuttle launches, upon which the military would occasionally piggyback payloads. “Some people would try to figure out the orbital parameters based on the time of launch and information from previous missions,” he says.
The orbital characteristics tell you more than just where a satellite is: It can tell you what it does. For most satellites, this data is public, and published (among other places) on a website called CelesTrak. The goods for each probe is a set of numbers called the two-line element. These are coordinates and time codes noting important things like the satellite’s apogee, perigee, time it passed certain latitudes and longitude, how many times it orbits Earth in a day, and so on and so forth.
More about satellite observations in the HobbySpace Satellite Watching section.