“It was a very clean launch,” said Brig. Gen. Douglas Schiess, commander of the 45th Space Wing

CAPE CANAVERAL AIR FORCE STATION, Fla. — A United Launch Alliance Atlas 5 rocket outfitted with five strap-on boosters blasted off Space Launch Complex 41 Wednesday at 12:15 a.m. EST.

“It was a beautiful launch, a very clean launch,” Brig. Gen. Douglas Schiess, commander of the 45th Space Wing and director of the Eastern Range, told SpaceNews shortly after liftoff.

The mission was to deliver an Air Force communications satellite, the $1.8 billion Advanced Extremely High Frequency AEHF-4 to a customized geostationary transfer orbit.

The satellite was scheduled to separate about three hours and 32 minutes after launch. At exactly 3 hours, 32 minutes, 54 seconds, AEHF-4 separated.

The 50th Space Wing at Schriever Air Force Base, Colorado, and the Air Force Space and Missile Systems Center in Los Angeles, will take over the satellite and “start bringing the satellite to life,” said Schiess.

The rocket was set to coast for more than three hours before a third engine firing and separation of the AEHF-4 satellite. At around 3 a.m., ULA reported that the vehicle remained stable as it coasted high above the Indian Ocean. After 3 hours and 28 minutes, the Centaur upper stage powered by the Aerojet Rocketdyne RL10C-1 engine was running again for its third firing, a burn lasting about 100 seconds.

After 3 hours, 30 minutes, the third main engine cutoff was confirmed, completing the powered phase of flight. Centaur performed its third burn that raised the orbit’s low point and reduced orbital inclination for the AEHF-4 payload, ULA reported. At 3:47 a.m., the company declared, “the Advanced Extremely High Frequency-4 communications satellite has been deployed into space.”

This was ULA’s eight launch this year, the 131st since the company was formed in 2006, and will be the 50th launch for the U.S. Air Force.

The Air Force chose the 551 version of the Atlas 5 — powered by five strap-on solid boosters — for this mission because of the enhanced GTO placement. A more powerful vehicle was needed to deliver the payload with a much higher perigee, or low point of the transfer orbit, significantly reducing inclination relative to the equator, said ULA. “Those actions by the launch vehicle will benefit the satellite and conserve its onboard fuel supply by getting AEHF-4 closer to its final orbit.”

This was the 79th Atlas 5 mission and the 9th in the 551 configuration.

The AEHF-4, made by Lockheed Martin, bristles with antennas and is part of a projected six-satellite constellation that provides secure, nuclear-survivable, anti-jam communications. AEHF was conceived more than a decade ago as a replacement for the aging Milstar satellites. The AEHF constellation also is used by Canada, the Netherlands and the United Kingdom. Australia, Japan and NATO are in talks with the U.S. to join the program.

Three AEHFs have been in operation for about five years. After the fourth satellite is on orbit, the constellation will form a ring around geostationary Earth orbit.