Top Secret: What Did That Delta IV Heavy Take into Space?

On Saturday, very little was known about the mammoth payload a Delta IV Heavy was carrying into space. Launching from Florida's Cape Canaveral Air Force Station, the 70 metre-high rocket blasted into the atmosphere with a mystery satellite known only as the NROL-26 mission. As the acronym suggests, the mission was carrying a National Reconnaissance Office satellite. However, a little after T+7 minutes 40 seconds, shortly after the second stage engines had fired, a media blackout prevented the world from knowing where the payload was going.
Four days on from this secretive rocket launch, what do we know about NROL-26?

Read the rest of Ian O'Neill's article on Universe Today