And the upper stage's HM7B engine is now firing to inject the ABS 2 and Athena-Fidus satellites into orbit.
The residual hydrogen burn flares will fire beneath the Vulcain engine at Minus-6 seconds to burn away any free hydrogen gas. At Minus-3 seconds, onboard systems take over and the two inertial guidance systems go to flight mode. Vulcain main engine ignition occurs at Minus-0 seconds with checkout between Plus+4 and 7 seconds. If there are no problems found, the solid rocket boosters are ignited at Plus+7.0 seconds for liftoff at Plus+7.3 seconds.
The weather is now green for liftoff at 2130 GMT (4:30 p.m. EST).
At Minus-4 seconds, the rocket's onboard computer will take over control of main engine start, health checks of the powerplant and solid rocket booster ignition commanding for liftoff.
The satellites will use their on-board engines to raise their orbits and position themselves over the equator.
The 13,955-pound ABS 2 satellite, built by Space Systems/Loral of Palo Alto, Calif., will begin a 15-year operational mission beaming telecom services, direct-to-home television, multimedia programming and data link services across a wide swath of the Eastern Hemisphere.
The spacecraft's Ku-band, C-band and Ka-band transponders will reach from Europe to the Asia-Pacific.
The 6,790-pound Athena-Fidus spacecraft, manufactured by Thales Alenia Space, is a joint project between France and Italy to expand broadband communications services for defense and security authorities beyond the jam-resistant satellites already used by the nations' militaries.
It will take more than 32 minutes to inject the satellites into orbit and release them. The payloads have a combined mass of approximately 22,518 pounds. Get an overview of the launch sequence.
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Here are some statistics on today's launch:
The 17.7-foot-diameter first stage's Vulcain 2 engine burns 149.5 metric tons, or about 329,000 pounds, or liquid oxygen 25 metric tons, or about 55,000 pounds, of liquid hydrogen. The cryogenic upper stage's HM7B engine consumes about 14.7 metric tons, or more than 32,000 pounds, of oxygen and hydrogen.
The fluids are stored at super-cold temperatures and naturally boil off in the warm tropical atmosphere in French Guiana. More propellant is slowly pumped into the rocket for most of the countdown to replenish the cryogenic fuel.
The topping sequence ends in the final few minutes of the countdown as the fuel tanks are pressurized and the fueling system is secured.
Built by a consortium of European contractors led by Snecma of France, the Vulcain 2 engine generates up to 300,000 pounds of thrust during its 9-minute firing. It burns about 320 kilograms, or 705 pounds, of liquid oxygen and liquid hydrogen propellant per second.
The engine's nozzle has an exit diameter of 2.1 meters, or about 6.9 feet. It weighs more than 4,600 pounds and its liquid oxygen and liquid hydrogen turbopumps spin at 12,300 rpm and 35,800 rpm, respectively.
The Vulcain 2 replaced the Vulcain engine used on the initial version of the Ariane 5. The newer engine produces 20 percent more thrust.
The Ariane 5's upper stage is powered by an HM7B engine, a modified version of the HM7 engine used on the upper stage of the Ariane 4 rocket. The 364-pound HM7B engine is manufactured by Airbus Defence and Space in Ottobrunn, Germany.
The HM7B engine produces more than 14,500 pounds of thrust in vacuum.
The Ariane 5 configuration with a Vulcain 2 engine and HM7B-powered cryogenic upper stage is known as the Ariane 5 ECA.
The Ariane 5's twin solid rocket boosters are packed with propellant near the launch site in French Guiana before they are assembled and positioned on each side of the cryogenic core stage.
With the rocket now fully fueled for launch, the vehicle weighs 1.7 million pounds.
The four-legged lander, located at the north end of the old space shuttle runway, will fly to an altitude of 465 feet and forward 636 feet before descending to a soft touchdown on a landing pad inside a field with scattered boulders, makeshift craters and inclines designed to simulate the lunar surface.
Morpheus is testing next-generation lander technologies, including a methane-fueled main engine and terrain-mapping guidance sensors.
Countdown clocks began ticking at 0900 GMT (4 a.m. EST), followed by power-up of the rocket's computer and electronics for an electrical check beginning at 1300 GMT (8 a.m. EST).
Workers finished their hands-on tasks on the launch pad, including the closure of doors, removal of safety barriers and configuring fluid lines for fueling. The ground team then evacuating the ELA-3 launch pad before the start of fueling.
Read our full story.
And check out photos of the rocket's rollout to the launch pad.
The hour-long rollout was to be followed by connections of electrical, communications and fluid lines between the mobile launch platform and the launch pad. Filling of the Ariane 5 first stage's helium pressurization system was also to be completed this afternoon.
The 1.7-mile journey atop a mobile launch platform is set to begin around 10:20 a.m. local time (1320 GMT; 9:20 a.m. EST) from the Ariane 5's final assembly building. The rocket and launch platform are towed by a Titan tug powered by a 540-horsepower engine with dual transmission modes to control its movements with millimeter precision while running at full power.
But the forecast for rollout calls for inclement weather with possible lightning, which could prevent the Ariane 5 launcher from moving outside.
The rollout should take about one hour before the 166-foot-tall launcher arrives in the ELA-3 launch zone, carefully moving into place over the flame trench before technicians begin the job of connecting the mobile platform to the launch pad's electrical, telemetry and propellant loading systems.
Later Wednesday, workers will fill the rocket's first stage liquid helium sphere, which contains pressurant for the cryogenic propellant tanks to be loaded with liquid oxygen and liquid hydrogen during the final countdown Thursday.
Liftoff is set for 2030 GMT (3:30 p.m. EST; 5:30 p.m. French Guiana time) at the opening of a 2-hour, 5-minute launch window.
The ABS 2 and Athena-Fidus satellites will be deployed in orbit about a half-hour later.
The payloads were added to the two-stage hydrogen-fueled launcher inside the Ariane 5's final assembly building at the Guiana Space Center, a tropical spaceport hugging the equator on the northern coast of South America.
The launch set for Feb. 6 will be the first of up to eight Ariane 5 missions this year, a record pace never matched before in the workhorse booster's 18-year flight history.
The Feb. 6 launch window opens at 2030 GMT (3:30 p.m. EST) and extends for 2 hours, 5 minutes.
Technicians installed the flight's passengers on top of the Ariane 5 rocket Tuesday and Wednesday.
Fully loaded with maneuvering propellant, the satellites are enclosed inside the Ariane 5's 5.4-meter-diameter (17.7-foot-diameter) payload fairing.
The spacecraft are mounted in a dual-payload stack employed on all of the Ariane 5's telecom satellite launches.
The ABS 2 satellite, designed for a television broadcasting mission, occupies the upper position inside the fairing, mounted on top of the barrel-shaped Sylda dual-payload adapter.
The joint Franco-Italian Athena-Fidus military communications spacecraft will ride into orbit in the fairing's lower spot, enclosed inside the Sylda adapter's volume while attached directly to the Ariane 5's upper stage.
ABS 2 is scheduled to deploy first from the rocket at T+plus 27 minutes, 19 seconds. The Sylda adapter will jettison at T+plus 30 minutes, 15 seconds to expose the Athena-Fidus payload, which will separate at T+plus 32 minutes, 28 seconds.
The rocket is targeting an orbit with a low point of 153 miles, a high point of 22,330 miles and an inclination of 6 degrees.
Built by Space Systems/Loral of Palo Alto, Calif., the ABS 2 spacecraft has a liftoff weight of about 13,955 pounds. The Thales Alenia Space-built Athena-Fidus satellite tips the scales at 6,790 pounds.
The Ariane 5 is the only launcher on the commercial market capable of lifting two hefty payloads to such a high orbit.
The mission, codenamed VA217 under Arianespace's naming scheme, was delayed two weeks to replace the nozzle of the rocket's hydrogen-fueled HM7B upper stage engine after a tool fell and nicked the engine inside the assembly facility.
Evry, France-based Arianespace is flying its first two Ariane 5 flights of 2014 out of sequence. The VA216 mission, scheduled to loft the ASTRA 5B and Amazonas 4A spacecraft, is set for launch March 7 after a delay from December caused by concern with one of that flight's two communications satellite payloads.
The Ariane 5 launch team will gather Friday for a countdown rehearsal at the Guiana Space Center.
The schedule calls for final arming of the launcher Monday and Tuesday. A launch readiness review Tuesday will also give approval to roll the 166-foot-tall rocket from the final assembly building to the ELA-3 launch zone.
The 1.7-mile rail trip is set for Wednesday morning, followed by connections between the rocket and launch pad before the countdown begins for Thursday's liftoff.