Dec 16 00:05The missionUnited Launch Alliance today will launch the next grouping of operational satellites for Amazon Leo, formerly known as Project Kuiper.Amazon Leo is built around an initial constellation of more than 3,000 advanced low Earth orbit satellites. Its mission is to provide fast, reliable internet to customers and communities around the world, including those unserved or underserved by traditional connectivity technologies. The system has the capacity, performance, and flexibility to serve a wide range of customers, from individual households to schools, hospitals, businesses, government agencies and other organizations operating in places without reliable connectivity.Amazon Leo's satellite payloads are the heaviest Atlas V has ever flown. The payload is supported through attachment and reinforcement elements for the ride to orbit.ULA made several modifications and design changes to accommodate the mass and size of the missions. That included enhancements to the ground handling equipment needed to transport the encapsulated payload during the move from Amazon's satellite processing facility to ULA's Vertical Integration Facility and the hardware used to hoist the payload atop the Atlas V for connection.
Dec 16 00:08The launch team is controlling the countdown from the ASOC. The Cape also has assistance from design teams at ULA's Denver Operations Support Center, or DOSC. Once all of the satellites have separated from the rocket in space later today, the Amazon Leo team will take over constellation management from the 24/7 mission operations center in Redmond, Washington.
Dec 16 00:15The call to stations for cryogenic tanking has been announced to all console operators.The ground chilldown of the Atlas first stage liquid oxygen system is now underway and the pad's liquid oxygen tank for Centaur is being pressurized to chilldown levels.We are coming up on the readiness polls of the launch team to verify all systems are GO for fueling operations and at this time we are not working any technical issues that would preclude the start of tanking today.
Dec 16 00:20Weather remains 90% GOIn the pre-fueling weather briefing to mission management, the launch weather officer reports weather currently looks good for a rocket countdown. The radar is dry, winds are light and there are no weather constraints against proceeding into Atlas V fueling operations as scheduled.The launch time forecast remains unchanged with a 90 percent chance of acceptable conditions.The launch outlook continues to call for a few clouds, good visibility, northeasterly winds of 8-10 knots gusting to 15 knots and a temperature near 58 degrees F.
Dec 16 00:23This is Atlas Launch Control at T-minus 2 hours and holding, with five minutes remaining in the built-in hold. Launch Conductor Scott Barney is briefing console operators on procedures going forward in today's countdown and the proper method for reporting any issues. This operation is classified hazardous -- cryogenics will be loaded, ordnance items are installed and high-pressure and inert gases are in use.
Dec 16 00:25ULA Launch Director Don Malin is receiving status inputs on technical readiness from the ULA director of engineering and Amazon's spacecraft mission director, the results of which will feed into the readiness poll to authorize fueling to begin.
Dec 16 00:26Go for fuelingA readiness poll of the launch team by Launch Conductor Scott Barney, with concurrence of ULA Launch Director Don Malin, has approved cryogenic tanking operations to begin at the earliest opportunity once the countdown resumes.
Dec 16 00:28Countdown resumesThis is Atlas Launch Control at T-minus 2 hours (L-3 hours) and counting. The next phase of today's launch countdown has started on schedule as we continue to target 3:28 a.m. EST (0828 UTC) for liftoff of Amazon Leo 4 for the broadband constellation.Preparatory steps for fueling are being kicked off, including chilldown of the transfer lines to the Centaur upper stage liquid oxygen system.
Dec 16 00:33Let's take a look at the process of preparing the Atlas V rocket to reach this point in today's countdown to Amazon Leo 4. The high-performance variant of the legendary rocket family will deliver the 17-ton payload into orbit, helping to connect the world one launch at a time.
Dec 16 00:42Centaur LO2 loading beginsCentaur propulsion console operators here at the Launch Control Center have begun procedures to load the cryogenic propellants into Atlas V for today's Amazon Leo Atlas-4 mission.This first step is fueling will see about 4,150 gallons of liquid oxygen filling the Centaur upper stage for today's launch.
Dec 16 00:47While today's Atlas V launch has plenty of similarities to the previous Amazon flights, it is no less significant. The Leo Atlas 4 (LA-4) mission will mark another step to deploy an advanced broadband constellation in low Earth orbit (LEO).Like the successful Atlas V Kuiper 1 mission on April 28, Kuiper 2 on June 23 and Kuiper 3 on Sept. 25, which delivered Amazon's first operational spacecraft into LEO, the upcoming LA-4 mission will launch another batch of 27 satellites into space.The same Atlas V rocket configuration will be used as the inaugural missions -- with five side-mounted GEM 63 solid rocket boosters, a 17.7-foot-diameter (5.4m) composite payload fairing and single upper stage engine.And we will be flying the same flight profile to reach the targeted a 51.9-degree, 280-mile-high (450 km) low Earth orbit.
Dec 16 00:52Atlas LO2 loading beginsFilling of the Atlas V rocket's largest tank has begun. About 48,800 gallons of super-cold oxidizer for the main engine is flowing into the liquid oxygen tank on common core booster first stage.
Dec 16 00:53Now 30 percent of the Centaur LOX tank has been filled. The liquid oxygen -- chilled to Minus-298 degrees F -- will be consumed during the launch by the Centaur's single RL10C-1-1 engine along with liquid hydrogen to be pumped into the stage a little later in the countdown.
Dec 16 01:01The Centaur upper stage's liquid oxygen tank has reached the 75 percent level as filling continues.The chilldown conditioning of liquid hydrogen propellant lines at Space Launch Complex-41 is starting to prepare the plumbing for transferring the Minus-423-degree F fuel into the rocket.
Dec 16 01:04First stage liquid oxygen tank loading is transitioning from slow-fill to fast-fill mode.
Dec 16 01:08The Centaur liquid oxygen tank is topping to flight level.
Dec 16 01:11The first stage liquid oxygen tank has reached the 20 percent mark already.
Mission ProfileA delicate balance of brute force and precision is needed when launching a 17-ton payload into orbit Amazon's broadband constellation. That is what the Atlas V 551 rocket will deliver when it performs the Amazon Leo Atlas 4 (LA-4) mission.
Dec 16 01:21First stage liquid oxygen tank is 50 percent full thus far. The LOX will be consumed along with RP-1, a highly refined kerosene, by the RD-180 main engine on the first stage during the initial four minutes of flight. The 25,000 gallons of RP-1 were loaded into the rocket after rollout on Saturday.
Dec 16 01:28We are passing Launch Minus-2 hours in the countdown. Tanking operations are proceeding nominally after beginning at the earliest opportunity in our timeline today. All activities remain on schedule for a liftoff at 3:28 a.m. EST (0828 UTC).
