An unmanned Delta 4 rocket lifted off at sunset from Cape Canaveral Air Force Station, following a delay because of concerns over winds. It hoisted a satellite for the National Reconnaissance Office.
The reconnaissance office is keeping mum about the purpose of the satellite.
It was the third rocket launch from Florida's Space Coast in just over two weeks.
Space shuttle Discovery blasted off on its final mission Feb. 24.
Then the Air Force sent a secretive, unmanned space plane into orbit on March 5. The X-37B, resembling a mini-shuttle, is supposed to land back on Earth, but authorities are not saying when. It's the second experimental vehicle of its type to fly in space.