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

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Tory Bruno ✔@torybruno3:49 PM - Mar 26, 2020

Nice morning at the Cape. A little overcast, but ok. All systems are green. The count is proceeding  on track. #AEHF6

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Tory Bruno ✔@torybruno 3:54 PM - Mar 26, 2020

Today's Atlas launch of #AHEF6 will fly several #Vulcan systems: Common Avionics (again) and upgrades to the ground support systems.

[tnt22]

Mar 26 15:52

The Atlas-Centaur rocket has been powered up for its launch of AEHF-6.

The flight control operator in the Launch Control Center performed the power up. Soon, he will begin avionics testing while the rocket's Inertial Guidance and Control Assembly (INCA) flight computer is allowed to warm up. Later, the operator will conduct guidance system testing and steering checks of the engine nozzles prior to cryogenic fueling.

The countdown continues to track on schedule for liftoff at 2:57 p.m. EDT (1857 UTC). At T-minus 5 hours 34 minutes (L-6 hours, 4 minutes) and counting, this is Atlas Launch Control.

[tnt22]

Mar 26 16:14

The guidance system test is beginning, the next major milestone in today's countdown. This activity will take the next couple of hours to complete.

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Spaceflight Now @SpaceflightNow 3:13 PM - Mar 26, 2020

The countdown has begin for today's launch of an Atlas 5 rocket from Cape Canaveral.

The United Launch Alliance rocket is set for liftoff at 2:57pm EDT (1857 GMT) with the US military's AEHF 6 communications satellite.

LIVE COVERAGE: https://spaceflightnow.com/2020/03/25/atlas-5-aehf-6-mission-status-center/ ...

[tnt22]

Mar 26 16:34
Weather improves to 90% GO

This is Atlas Launch Control at T-minus 4 hours, 52 minutes (L-5 hours, 22 minutes) and counting. Launch Weather Officer Will Ulrich from the 45th Weather Squadron reports that conditions at Cape Canaveral are looking favorable for the flight of Atlas V and AEHF-6 this afternoon, forecasting a 90 percent chance of acceptable conditions at liftoff time.

All conditions are GO at the present time and the low stratus clouds overhead this morning should burn off by noon.

The outlook for launch time calls for some scattered low clouds, good visibility, easterly winds of 10 gusting to 15 knots and a temperature near 78 degrees F.

The main concern will be cumulus clouds from the onshore flow.

[tnt22]

Любителям статистики и просто истории

Mar 26 17:00

Space Launch Complex-41 is the East Coast home of the Atlas V rocket at Cape Canaveral Air Force Station in Florida. "Slick-41" was constructed by the U.S. Air Force in the 1960s for the Titan rocket program.



There were 27 launches of the Titan rocket family between 1965 and 1999, including NASA's two Viking missions in 1975 that landed on Mars and both Voyager probes to the outer solar system in 1977.

The site was rejuvenated in support of the Atlas V starting in 1999. It employs a "clean pad" concept of operations to ready launch vehicles and payloads for ascent into space.

The Atlas V rocket elements are assembled atop a Mobile Launch Platform inside the Vertical Integration Facility located adjacent to the launch pad. The platform and fully stacked Atlas V then travels by rail approximately 1,800 feet northward from the VIF to the pad for the final countdown, fueling and liftoff.

AEHF-6 will be the 68th Atlas V launch from this pad and the 95th overall since 1965.

[tnt22]

Mar 26 17:03

The flight control operational test is getting underway. This test will validate the control functions on the Atlas first stage main engine and the Centaur upper stage's engine by confirming that valves cycle properly and that the engine steering systems perform as commanded.

[tnt22]

Mar 26 17:32
Sunset Photos

See our Flickr album for photos from last night's sunset at the Atlas V pad.

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Mar 26 17:46

First stage propulsion and hydraulic preps have been completed. The propulsion preps configured the ground liquid oxygen transfer system and ground pneumatic supply systems for filling the Atlas first stage LOX tank and pressurizing the Atlas helium bottles for launch. The hydraulic preps configured the ground hydraulic pressure unit to provide for first stage main engine pre-launch hydraulic control.

[tnt22]

Mar 26 18:01

The main engine steering test is underway.

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Стучим по дереву...

Mar 26 18:15

We are working no issues in the countdown here in the Atlas Spaceflight Operations Center (ASOC) or at the Space Launch Complex-41 pad. Liftoff remains scheduled for 2:57 p.m. EDT (1857 UTC).

[tnt22]

Mar 26 18:37

Antenna checks are being performed to verify functionality of the GPS Metric Tracking system. GPS MT is the system that uses the orbiting Global Positioning System navigation satellite constellation to track the rocket's flight downrange with position, velocity and timing information.

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Mar 26 18:58

Internal battery checks are nearing completion and the GPS Metric Tracking antenna checks have been accomplished.

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Mar 26 19:05

The initiation of gaseous nitrogen flow to the launch vehicle has started. This changes the environmental control system (ECS) to supply nitrogen gas rather than conditioned air to the internal compartments of the Atlas V and the payload fairing in preparation for fueling and launch.

[tnt22]

Mar 26 19:11
Weather Remains 90% GO

In the pre-fueling weather briefing to mission management, Launch Weather Officer Will Ulrich reports that conditions remain favorable at Cape Canaveral for a rocket countdown. Skies are mostly clear, winds are within limits and there are no weather constraints against proceeding into Atlas V fueling operations as scheduled.

The launch time forecast remains 90 percent favorable, with the only concern being cumulus clouds.

The launch time outlook calls for scattered low clouds, easterly winds 10 to 15 knots and a temperature near 78 degrees F.

[tnt22]

Mar 26 19:14

The launch pad crew has completed its hands-on work to ready Space Launch Complex-41 for today's mission, and Launch Conductor Scott Barney has given the instruction for personnel to depart the site in advance of fueling operations.

[tnt22]

Mar 26 19:15

Hold-fire checks are being conducted at this time. This verifies the circuitry used to stop the countdown if a safety concern arises.

[tnt22]

Mar 26 19:16
No COLAs Today

Safety officials have confirmed that there are no Collision Avoidance (COLA) periods during today's 120-minute launch window. COLAs are brief moments in time when the launch is not allowed to occur because the trajectory would pass too close to another object already in space. This analysis is based on a screening of known active and debris objects in orbit that could cause a conjunction with the ascending Atlas V and AEHF-6.

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https://spaceflightnow.com/2020/03/26/atlas-5-launch-timeline-for-the-aehf-6-mission/

Atlas 5 launch timeline for the AEHF 6 mission
March 26, 2020 | Stephen Clark

A United Launch Atlas 5 rocket is set to launch the U.S. Air Force's 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.

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).

The AEHF 5 mission will be the 83rd flight of an Atlas 5 rocket, and the second Atlas 5 launch of 2020.

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's 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's capacity and resiliency.

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.

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.

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.

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 — like AEHF 5 last year — will need to consume less of its own finite propellant supply to circularize its orbit, leading to a longer operating lifetime for the mission.

According to an Atlas 5 user's guide published by ULA, the GSO kit includes additional battery power, a full load of hydrazine to control the upper stage's orientation in space, and additional shielding over sensitive components, including the Centaur' hydrogen and oxygen tanks.

An overview of the Atlas 5/AEHF 6 launch sequence and a ground track map illustrating the rocket's path after liftoff are are posted below.

https://www.youtube.com/embed/tPfJq3aBJ6Y

Credit: United Launch Alliance

T+0:00:01.1: Liftoff


After igniting its RD-180 main engine at T-minus 2.7 seconds, the Atlas 5 rocket fires its five solid rocket boosters and rises away from Complex 41 at Cape Canaveral Air Force Station, Florida, with approximately 2.6 million pounds of thrust.

T+0:00:34.4: Mach 1


The Atlas 5 rocket exceeds the speed of sound, flying east from Cape Canaveral Air Force Station.

T+0:00:46.2: Max-Q


The Atlas 5 rocket passes through the region of maximum dynamic pressure during ascent through the lower atmosphere.

T+0:01:46.7: Jettison SRBs


Having burned out of propellant approximately 15 seconds earlier, the five spent Aerojet Rocketdyne-built solid rocket boosters are jettisoned once dynamic pressure conditions are satisfied. The first pair of boosters will jettison, followed a second-and-a-half later by the remaining three.

T+0:03:24.9: Payload Fairing Jettison


The Atlas 5 rocket's payload fairing, made in Switzerland by RUAG Space, is jettisoned in a clamshell-like fashion once external heating levels drop below predetermined limits after climbing through the dense lower atmosphere. The Forward Load Reactor deck that connected the payload fairing's structure to the Centaur upper stage is released five seconds after the shroud's jettison.

T+0:04:26.3: Main Engine Cutoff


The RD-180 main engine completes its firing after consuming its kerosene and liquid oxygen fuel supply in the Atlas first stage.

T+0:04:32.3: Stage Separation


The Common Core Booster first stage of the Atlas 5 rocket separates from the Centaur upper stage. Over the next few seconds, the Centaur engine liquid hydrogen and liquid oxygen systems are readied for ignition.

T+0:04:42.3: Centaur Ignition 1


The Centaur RL10C-1 engine ignites for the first of three upper stage firings. This burn will inject the Centaur stage and the AEHF 6 satellite into an initial parking orbit.

T+0:11:46.9: Centaur Cutoff 1


The Centaur engine shuts down after arriving in a planned low-Earth parking orbit. The vehicle enters an 11-minute coast period before arriving at the required location in space for the second burn.

T+0:22:44.3: Centaur Ignition 2


Producing 22,900 pounds of thrust, the Centaur re-ignites to accelerate the AEHF 6 payload into a highly elliptical transfer orbit from the parking altitude achieved earlier in the launch sequence. This burn lasts more than six minutes.

T+0:28:52.7: Centaur Cutoff 2


The second Centaur firing places the AEHF 6 satellite into an elliptical transfer orbit stretching more than 20,000 miles above Earth, beginning a five-hour coast period for the mission's final orbital adjustment maneuver. A secondary U.S. Air Force smallsat payload named TDO 2 will separate from the Centaur upper stage's aft bulkhead around 30 seconds after the RL10 engine shuts down. The TDO 2 mission support space domain awareness through optical calibration and satellite laser ranging.

T+5:36:39.1: Centaur Ignition 3


After a five-hour coast, the Centaur's RL10 engine reignites for a roughly one-minute, 28-second firing to place the AEHF 6 satellite in the proper orbit for spacecraft separation.

T+5:38:07.8: Centaur Cutoff 3


The powered phase of flight is concluded as the Centaur reaches the planned elliptical geostationary transfer orbit with an expected perigee, or low point, of 6,758 miles (10,876 kilometers), an apogee, or high point, of 21,933 miles (35,298 kilometers), and an inclination of 13.9 degrees. The final RL10 engine burn will fire until depletion of the Centaur upper stage's propellant, giving the AEHF 6 satellite the most favorable orbit possible before spacecraft separation.

T+5:40:56.9: AEHF 6 Separation


The AEHF 6 spacecraft deploys from the Centaur upper stage.

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