The U.S. Defense Department's Space Surveillance Network (SSN) is the most elaborate ground- and space-based system for tracking what's going on in orbit. U.S. Strategic Command says the Space Situational Awareness Sharing Program now distributes SSN-derived data on around 1,500 functioning satellites to 285 different organizations. Only 40 of these are U.S. government-owned. Credit: U.S. Strategic Command

PARIS — The seven large geostationary-orbit satellites that were incorrectly disposed of in 2015 include two satellites whose failures forced their owners to abandon them on the geostationary highway, according to documents based . . .

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