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Delta 4 Heavy launch
United Launch Alliance’s Delta 4 Heavy rocket lifts off from California’s Vandenberg Air Force Base, sending the NROL-71 classified payload into space. (ULA Photo)

The National Reconnaissance Office’s latest classified spy satellite, NROL-71, was launched today by a United Launch Alliance Delta 4 Heavy rocket into California’s sunny skies.

Today’s trouble-free countdown at Vandenberg Air Force Base came in contrast to the string of technical glitches that held up liftoff by more than a month.

The original launch date had been set for Dec. 7, but the technical issues — including concerns about a hydrogen leak on one of the engine sections — forced repeated delays. One memorable delay came just as a fireball was sighted over the region, sparking a momentary mystery.

Plenty of mystery still surrounds the NROL-71 mission: Outside experts suspect that the payload could be the first of what’s known as the Block 5 KH-11 spy satellites — next-generation cousins of the Hubble Space Telescope that are tasked with watching Earth rather than the heavens.

Neither United Launch Alliance nor the NRO is saying anything on that score.

To preserve operational security, ULA cut off updates about the mission’s progress a little more than six minutes after the 11:10 a.m. PT liftoff. But in a post-launch statement, ULA indicated that it got NROL-71 off to a successful start.

“Congratulations to our team and mission partners for successfully delivering this critical asset to support national security missions,” said Gary Wentz, ULA vice president of government and commercial programs. “Thank you to the entire team for their perseverance, ongoing dedication and focus on 100 percent mission success.”

In a series of tweets, the NRO also confirmed launch success:

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