A United Launch Atlas 5 rocket is set to launch the U.S. Air Force\u2019s sixth and final Advanced Extremely High Frequency communications satellite from Cape Canaveral. This timeline shows the major mission events planned over a nearly six-hour flight to an optimized geostationary transfer orbit.<\/p>\n
The 197-foot-tall (60-meter) rocket, propelled by an RD-180 main engine and five solid rocket boosters, is set for liftoff during a two-hour launch window Thursday, March 26, that opens at 2:57 p.m. EDT (1857 GMT).<\/p>\n
The AEHF 5 mission will be the 83rd flight of an Atlas 5 rocket, and the second Atlas 5 launch of 2020.<\/p>\n
Built by Lockheed Martin, the AEHF 6 satellite joins five previous satellites in the AEHF constellation launched by Atlas 5 rockets in 2010, 2012, 2013, 2018 and 2019. The first four AEHF satellites in orbit allowed the Air Force\u2019s new generation of secure, nuclear-hardened voice, video and data relay spacecraft to span the globe, and the addition of two more AEHF geostationary relay satellite will grow the network\u2019s capacity and resiliency.<\/p>\n
The Atlas 5 launch sequence will last 5 hours, 40 minutes, from liftoff until deployment of the AEHF 6 spacecraft. On this mission, ULA added extra hardware and maneuvering fuel to the Centaur upper stage, enabling the launcher to deliver the AEHF 6 satellite closer to its final orbit more than 22,000 miles (nearly 36,000 kilometers) above the equator.<\/p>\n
The GSO kit was added to the Atlas 5 rocket on the fifth AEHF launch last August, after the first four AEHF missions did not employ the additional capability.<\/p>\n
The extra performance provided by the GSO kit will allow the Centaur upper stage to coast an additional two hours before its third firing. Spacecraft separation is scheduled for T+plus 5 hours, 40 minutes.<\/p>\n
Thanks to the mission profile change, the AEHF 6 satellite will separate in an orbit with a perigee, or low point, several thousand miles higher than would be possible without the GSO kit. That means AEHF 6 \u2014 like AEHF 5 last year \u2014 will need to consume less of its own finite propellant supply to circularize its orbit, leading to a longer operating lifetime for the mission.<\/p>\n
According to an Atlas 5 user\u2019s guide published by ULA, the GSO kit includes additional battery power, a full load of hydrazine to control the upper stage\u2019s orientation in space, and additional shielding over sensitive components, including the Centaur\u2019 hydrogen and oxygen tanks.<\/p>\n
An overview of the Atlas 5\/AEHF 6 launch sequence and a ground track map illustrating the rocket\u2019s path after liftoff are are posted below.<\/p>\n