SpaceX launches top-secret spy satellite for US government

The unmanned Falcon 9 rocket lifted off from its NASA-leased pad at Kennedy Space Center in Florida.

It was SpaceX's first mission for the National Reconnaissance Office. No details were divulged about the newly launched NRO satellite. Instead, SpaceX focused its webcast on the successful touchdown of the first-stage booster.

The leftover booster — its job done — landed next door at Cape Canaveral Air Force Station several minutes after liftoff. Sonic booms rattled the area, serving as a Monday morning wake-up call. Across the country, cheers erupted at SpaceX Mission Control at company headquarters in Hawthorne, California.

SpaceX strives to return most of its boosters for reuse. The company's first recycled rocket flew last month.

This was the fourth SpaceX booster landing at Cape Canaveral; even more have landed on ocean platforms.

SpaceX founder and chief executive Elon Musk said via Twitter that both the launch and landing were good. But the upper-level wind at liftoff was "unusually high."

"Tough call, as high altitude wind shear was at 98.6 per cent of the theoretical load limit," he said in a tweet. Earlier in the morning, he noted about the wind, "Worrying, but not a showstopper."

Sunday's launch attempt was foiled at the last minute by a bad sensor.