Hobbyists are making it difficult for the US to keep the orbits of their constellation of spy satellites secret:
The observers, who congregate on a Web site called Heavens-Above and a mailing list called SeeSat-L, have amassed an impressive collection of information and expertise. For two decades, they have played a high tech game of hide-and-seek with the US's National Reconnaissance Office, a secretive satellite agency. By coordinating their efforts, amateur observers in Europe, North America, and South Africa monitor satellites at different phases of their journeys and extrapolate the precise dimensions of their orbits. Astonishingly, despite the hobbyists' modest resources - most observe part-time from their balconies and backyards with equipment available at RadioShack - they are good enough to spot almost anything the NRO, with its estimated $7 billion budget, blasts into space.