Last Sunday, at 5:58pm, the USAF launched NRO LR-32, a secret US military spy satellite so massive that it required this Delta IV Heavy rocket to reach orbit. In fact, the mysterious spacecraft is the largest satellite in the world.
According to the National Reconnaissance Office's Director Bruce Carlson, NRO LR-32 is indeed "the largest satellite in the world." The NRO is dedicated to the design, manufacturing, and operation of all the United States reconnaissance satellites. No official information has been published, but it "is believed to be an eavesdropping satellite positioned high above the equator in geosynchronous orbit" with a antenna the size of a football field once it's extended in orbit.
Images by Ben Cooper, from Launch Photography