WASHINGTON — A United Launch Alliance Atlas 5 rocket lifted off on March 26 at 4:18 PM EST from Space Launch Complex-41 at Cape Canaveral Air Force Station, carrying a $1.4 billion Advanced Extremely High Frequency (AEHF-6) communications satellite for the U.S. Space Force.

This was the sixth and final satellite of the AEHF constellation that provides secure, jam-proof voice and data communications for U.S. national leadership, military forces and international partners Canada, the Netherlands, the United Kingdom and Australia. All six were manufactured by Lockheed Martin.

The Atlas 5 flew in the 551 configuration with five side-mounted solid rocket boosters.

The launch was set to go at 2:57 PM but there was an unplanned hold called at T-minus 46 seconds. ULA CEO Tory Bruno on Twitter explained the hold was due to a fault in the ground hydraulics accumulator.

“Bad amplifier card on a ground system hydraulic pump controller. Working on a solution,” Bruno tweeted.

ULA engineers were able to fix the problem and get the Atlas 5 off within the two-hour launch window.

Atlas 5 rockets launched the first five AEHF satellites in 2010, 2012, 2013, 2018 and 2019.

This was ULA’s 138th launch, the 83rd of the Atlas 5 rocket since 2002 and the 11th in the 551 configuration. The mission also marked the 500th flight of the Aerojet Rocketdyne RL10 engine that powers the Centaur upper stage. Aerojet also provided the five AJ-60A solid rocket boosters.

Lt. Gen. John Thompson, commander of the U.S. Space Force Space and Missile Systems Center, told SpaceNews in a March 25 interview that it was important for get AEHF-6 launched on schedule despite reduced staff and other challenges related to the coronavirus pandemic.

“The AEHF launch is one of those we consider absolutely mission essential,” said Thompson. “These satellites are hugely important to presidential and national leadership communications in a crisis. They are also essential to warfighters and allies.”

The deployment of the sixth satellite ensures that the AEHF constellation will stay in service beyond 2030, Thompson said.

On its way to AEHF’s final orbit, the upper stage of the Atlas 5 at 4:47 PM released a small rideshare payload named TDO-2. The 12U cubesat carried U.S. government experimental payloads that will test optical calibration and satellite laser-ranging technologies for space domain awareness.

The rideshare satellite, sponsored by the Air Force Research Laboratory, was developed by the Georgia Institute of Technology and integrated by Parsons Corp.

The satellite separated from the launch vehicle nearly six hours after liftoff and will undergo approximately120 days of orbit-raising operations, followed by approximately 30 days of on-orbit testing. After tests are completed, SMC will transfer AEHF-6 control authority to U.S. Space Operations Command.

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...