A secret U.S. spy satellite rocketed to orbit before dawn Sunday atop an Atlas V flying United Launch Alliance’s final mission of the year from Cape Canaveral.

On the mission’s fifth launch attempt, the nearly 20-story rocket shot from Launch Complex 41 with 1.5 million pound of thrust, punching through low clouds lit up by a blazing main engine and two solid rocket boosters.

The flight for the National Reconnaissance Office flight appeared off to a good start as it angled southeast over the Atlantic Ocean through darkness, dropping the two solid boosters and first stage.

ULA cut off its launch broadcast less than five minutes after the 3:28 a.m. liftoff to help preserve the mission's secrecy. Less than two hours later, a press release confirmed the launch was a success.

Labeled NROL-52, the mission was speculated to be sending the second in a new generation of communications relay satellites on its way to an orbit near the equator more than 20,000 miles up.

That’s the analysis of hobbyists who are skilled spacecraft trackers and have studied NRO missions for years, working with publicly available information including the rocket’s performance and trajectory.

If correct, the satellite would be joining the Space Data System, or SDS, relaying intelligence collected by imaging craft orbiting lower over the Earth.

Sunday’s launch was a virtual copy of one flown in July of last year, which was thought to be first of the new relay spacecraft.

The NRO may be fielding the new relay spacecraft before beginning to launch upgraded imaging satellites, expected next year.

ULA’s second launch for the NRO in three weeks came just over a week after intelligence officials stressed space’s importance to their efforts, in testimony to a reconstituted National Space Council led by Vice President Mike Pence.

“The Intelligence community understands that our dominance in space relative to the intelligence that we need to keep America safe and informed — whether it’s our fighters or whether it’s our national assets – is of critical importance,” Director of National Intelligence Dan Coats said during the Oct. 5 meeting.

The artwork for Sunday’s NRO mission featured a bald eagle’s beak and talons bursting through a Captain America shield, and the Latin phrase “defensor libertatis,” meaning “defender of freedom.”

The mission was the ULA’s seventh of 2017, and the fifth of those flown from the Cape.

It wasn’t easy. Weather scrubbed launch attempts on Oct. 5, 6 and 14, while a faulty telemetry transmitter cut short an Oct. 7 countdown and forced the rocket off its pad for repairs.

“After recovering from Hurricane Irma that came through the area last month, and the last week’s weather challenges, the team found the right opportunity today to deliver this critical national asset to orbit,” said Laura Maginnis, ULA vice president of Government Satellite Launch.

ULA, a Boeing-Lockheed Martin joint venture formed in 2006, has two more launches scheduled this year from California on Delta rockets, including another for the NRO.

Sunday's launch came a few days after SpaceX launched a commercial satellite from nearby Kennedy Space Center, the company’s 15th mission so far this year. This year is the first SpaceX will have flown more than its top U.S. rival.

ULA is expected to resume Cape missions with a January launch of a U.S. missile warning satellite.