AEHF-6 – Atlas V 551 (AV-086) – Canaveral SLC-41 – 26.03.2020 20:18 UTC

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Mar 26 21:02

Today's launch availability lasts from 2:57 p.m. EDT (1857 UTC) to 4:57 p.m. EDT (2057 UTC). Liftoff is possible at the top of every minute within that two-hour period, for a total of 121 opportunities to launch today.

The window timing and duration are dictated by the orbital requirements of the AEHF-6 spacecraft and the Atlas V rocket's robust ability to meet those parameters.

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Mar 26 21:07
AEHF-6 Logo

The AEHF-6 patch is emblazoned on the Atlas V rocket's payload fairing.



The artwork depicts the AEHF-6 satellite deployed in space, joining the five previous AEHF spacecraft launched since 2010, as well as the flags of the countries involved in the AEHF program -- the U.S., United Kingdom, Canada, Australia and the Netherlands.

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03/26/2020 21:17 Stephen Clark

40 minutes until launch. Here are some statistics on this morning's mission:

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• 665th launch for Atlas program since 1957
  
• 367th Atlas launch from Cape Canaveral
  
• 254th mission of a Centaur upper stage
  
• 231st use of Centaur by an Atlas rocket
  
• 500th production RL10 engine to be launched
  
• 31st RL10C-1 engine launched
  
• 89th flight of an RD-180 main engine
  
• 119th-123rd AJ-60 solid rocket boosters flown
  
• 83rd launch of an Atlas 5 since 2002
  
• 31st U.S. Air Force/Space Force use of an Atlas 5
  
• 68th launch of an Atlas 5 from Cape Canaveral
  
• 2nd Atlas 5 launch of 2020
  
• 123rd Evolved Expendable Launch Vehicle flight
  
• 138th United Launch Alliance flight overall
  
• 75th Atlas 5 under United Launch Alliance
  
• 98th United Launch Alliance flight from Cape Canaveral
  
• 53rd ULA launch for U.S. Air Force/Space Force
  
• 28th 500-series flight of the Atlas 5
  
• 11th Atlas 5 to fly in the 551 configuration
  
• 95th launch from Complex 41
  
• 68th Atlas 5 to use Complex 41
  
• 7th orbital launch overall from Cape Canaveral in 2020
  

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Mar 26 21:22

Initial telemetry coverage of today's flight of the Atlas V rocket will be relayed via the TEL-4 tracking station here at the Cape. The Jonathan Dickinson Missile Tracking Annex (JDMTA) in South Florida will acquire the vehicle shortly after liftoff. A handoff from the ground sites to NASA's orbiting Tracking and Data Relay Satellites in geosynchronous orbit occurs during the initial burn of the Centaur and TDRS satellites continue for the rest of the mission.

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Mar 26 21:25

Anomaly Chief David McFarland is convening the problem-resolution team to discuss the loss of an RL10 temperature sensor.

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Mar 26 21:26

The fuel fill sequence is beginning. This procedure releases RP-1 kerosene fuel into the RD-180 main engine in preparation for ignition.

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03/26/2020 21:27 Stephen Clark

T-minus 15 minutes and counting. The Atlas 5 countdown is ticking toward a 15-minute planned hold at T-minus 4 minutes.

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03/26/2020 21:28 Stephen Clark

Less than 30 minutes until liftoff. The Atlas 5 team reports flight control final preps are completed at this time.

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Mar 26 21:29

Weather is observed and forecast GO for liftoff a half-hour from now, according to the countdown's final planned briefing by weather officer Will Ulrich.

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Mar 26 21:30

The problem-resolution team reports that the failed temperature sensor is no constraint to launch.

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Mar 26 21:32

Video cameras aboard the Atlas V rocket will be used to record key portions of today's mission. An aft-facing camera on the first stage will provide views of the vehicle climbing away from the Earth, solid rocket motor jettison and all the way nearly to staging. Just prior to booster engine cutoff, the view will switch to the aft-facing camera on the Centaur stage to show the first stage separating and ignition of the RL10C-1 engine. That same view will be available for the end of the first burn and then the ignition and shutdown of the engine on the second and third burns of the day. In addition, a forward-facing camera on Centaur will capture payload fairing jettison and AEHF-6 separation.

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Mar 26 21:33

The Automatic Determination and Dissemination of Just Updated Steering Terms, better known as the ADDJUST file, is being loaded into the Atlas V rocket's Inertial Navigation and Control Assembly (INCA) flight computer by the flight control operator here at the Launch Control Center. This is the planned steering parameters for the INCA to use based on today's upper level wind conditions.

A series of weather balloons has been launched throughout the countdown from the Range weather station at Cape Canaveral to collect measurements of wind speeds and directions to determine if conditions aloft violate the controllability or structural loads on the rocket during ascent. The balloon data was transmitted to ULA engineers in Denver to select a steering profile that minimizes launch vehicle responses.

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Mar 26 21:36

The AEHF-6 spacecraft atop the Atlas V rocket is transitioning to internal battery power for launch. This is the final configuring of the payload for liftoff.

The protected communications satellite, built by Lockheed Martin for the U.S. Air Force Space and Missile Systems Center, is destined to operate in geosynchronous orbit 22,300 miles above Earth.

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Mar 26 21:40

United Launch Alliance is using the Atlas V 551 rocket, with a five-meter-diameter payload fairing and a full complement of five strap-on solid rocket rockets, to launch the sixth Advanced Extremely High Frequency (AEHF-6) communications spacecraft into an optimized geosynchronous transfer orbit.

Leaving the pad on 2.6 million pounds of thrust from the combined power of the kerosene-fueled first stage main engine and all five solid boosters, the Atlas V will perform pitch, yaw and roll maneuvers to align with a due east heading along a flight azimuth of 93 degrees.

The vehicle will hit Mach 1, the speed of sound, in 35 seconds and pass through Max Q, the region of maximum dynamic pressure, at 46 seconds.

The solid boosters will burn out and separate in less than two minutes. The payload fairing that protected the satellite during atmospheric ascent will be jettisoned at the edge of space three-and-a-half minutes into flight.

Cutoff of the main engine and staging occurs four-and-a-half minutes after launch, allowing the cryogenic Centaur upper stage to ignite for a 7-minute initial burn to reach a preliminary parking orbit. A brief 11-minute coast through space sets up the Centaur to perform another 6-minute burn that accelerates the payload into a highly elliptical intermediate orbit.

The TDO-2 rideshare payload will be deployed at T+plus 29 minutes, 24 seconds.

Centaur then goes into its long-duration coast mode for more than five hours to reach the high point of the orbit. A third firing of the RL10 engine, lasting more than a minute-and-a-half, will raise the orbit's low point and reduce inclination relative to the equator.

Spacecraft separation is expected at T+plus 5 hours and 41 minutes in an optimized high-perigee, low inclination geosynchronous transfer orbit. ULA and the AEHF program produced this ascent profile to maximize mission flexibility over the satellite's lifetime.

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