Live coverage of Delta 4 countdown and launch

Culminating years of construction and testing, a $1.2 billion satellite designed to spot and track enemy missiles threatening the United States homeland, its deployed military forces abroad or allied nations will ascend to a surveillance post in space Thursday.

For its 70th launch in 14 years, the Atlas 5 rocket carried the NROL-79 payload into space for the National Reconnaissance Office.

A United Launch Alliance Delta 4 rocket blasted off from Vandenberg Air Force Base in California at 3:40 a.m. local (6:40 a.m. EST; 1140 GMT) today to place a secret payload into space for the National Reconnaissance Office. Follow the mission in our live journal.