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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.
Liftoff is set for 2204 GMT (6:04 p.m. EDT).
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 12,619-pound ASTRA 5B satellite, built by Airbus Defence and Space, will begin a 15-year operational mission beaming direct-to-home and direct-to-cable television services over Eastern Europe, Russia and neighboring markets. "It's basically there to allow new entrants into the DTH world the opportunity to develop their platforms and start developing their business," said Martin Halliwell, chief technical officer for SES of Luxembourg, ASTRA 5B's operator.
The satellite's Ka-band and Ku-band payload will also provide broadband services across the region.
The spacecraft, based on the Airbus Eurostar E3000 satellite bus, is flying with a hosted L-band navigation payload for the European Geostationary Navigation Overlay Service, which augments GPS navigation signals over Europe for specialty users such as the aviation and surveying industries.
The 6,477-pound Amazonas 4A spacecraft, manufactured by Orbital Sciences Corp., is owned by Madrid-based Hispasat and will cover South American with 24 Ku-band transponders.
Amazonas 4A will support customers with broadcast television, corporate mobile and fixed telephone networks, integrated communications solutions and remote training and telemedicine services. Voice, Internet and data transmission services will also be offered through Amazonas 4A, according to Hispasat.
It will take more than 34 minutes to inject the satellites into orbit and release them. The payloads have a combined mass of approximately 20,873 pounds, including the barrel-shaped Sylda dual-payload adapter.
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, of liquid oxygen and 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 weather outlook is favorable for tonight's 58-minute launch window. There is a low risk of lightning and surface winds are expected to be within limits.
Chilldown of liquid oxygen and liquid hydrogen propellant lines at the ELA-3 launch pad has begun. The chilldown procedure helps condition the ground plumbing before the cryogenic propellants are pumped inside the Ariane 5's first and second stages.
The countdown began as scheduled at 1034 GMT (6:34 a.m. EDT), followed by power-up of the rocket's computer and avionics systems for an electrical check beginning at 1434 GMT (10:34 a.m. EDT).
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 evacuated the ELA-3 launch pad before the start of fueling.
The launch window extends for 58 minutes.
A check of electrical systems is scheduled to occur around 1434 GMT (10:34 a.m. EDT).
Workers will also put finishing touches on the launch pad, including the closure of doors, removal of safety barriers and configuring fluid lines for fueling.
The launch team will begin the process to fuel the rocket with super-cold liquid hydrogen and liquid oxygen propellants at 1714 GMT (1:14 p.m. EDT). First, ground reservoirs will be pressurized, then the fuel lines will be chilled down to condition the plumbing for the flow of super-cold liquid hydrogen and liquid oxygen, which are stored at approximately minus 423 degrees Fahrenheit and minus 298 degrees Fahrenheit, respectively.
It will take approximately two hours to fill the Ariane 5 core stage tanks.
A similar procedure for the Ariane 5's cryogenic upper stage will commence at 1814 GMT (2:14 p.m. EDT).
Chilldown conditioning of the Vulcain 2 first stage engine will occur at 1914 GMT (3:14 p.m. EDT), and a communications check between the rocket and ground telemetry, tracking and command systems is scheduled for 2054 GMT (4:54 p.m. EDT).
The computer-controlled synchronized countdown sequence will begin seven minutes before launch to pressurize propellant tanks, switch to on-board power and take the rocket's guidance system to flight mode.
The Vulcain 2 engine will ignite as the countdown clock reaches zero, followed by a health check and ignition of the Ariane 5's solid rocket boosters seven seconds later to send the 1.7 million-pound launcher skyward.
Five seconds after blastoff, the rocket will begin pitching east from the ELA-3 launch pad, surpassing the speed of sound less than a minute into the mission. The Ariane 5's twin solid rocket boosters will jettison 2 minutes, 23 seconds after liftoff.
Once above the dense atmosphere, the launcher's payload fairing will fall away at an altitude of about 69 miles. The Ariane 5's first stage will shut down 8 minutes, 47 seconds after liftoff, followed moments later by stage separation and ignition of the hydrogen-fueled cryogenic HM7B upper stage engine.
The rocket's upper stage will fire for approximately 16 minutes, accelerating to a velocity of 20,971 mph, or more than 9.3 kilometers per second, to reach an orbit with a planned high point of 22,205 miles, a targeted low point of 155 miles and an inclination of 3 degrees.
The release of ABS 2 is scheduled for 26 minutes, 59 seconds. The rocket's barrel-shaped Sylda 5 dual-payload adapter will be jettisoned a few minutes later.
Athena-Fidus will separate from the lower portion of the payload stack at 34 minutes, 34 seconds.
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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 rollout was delayed from Thursday due to stronger-than-allowed surface winds. Officials elected to complete the transfer in the early morning Friday, when winds were predicted to be light.
Liftoff is set for 2204 GMT (6:04 p.m. EDT; 7:04 p.m. French Guiana time) Saturday.
Strong ground winds were gusting above the limit for safely rolling the Ariane 5 rocket to the launch pad.
The rocket was supposed to transfer from the final assembly building to the ELA-3 launch zone in French Guiana on Thursday morning.
Rollout has been rescheduled for Friday, with launch now set for Saturday at 2204 GMT (6:04 p.m. EDT) at the opening of a 58-minute launch window, according to Arianespace.
The heavy-lifting Ariane 5 ECA launcher, operated by French launch services firm Arianespace, is scheduled to take off at 2205 GMT (6:05 p.m. EDT; 7:05 p.m. local time) Friday from the Guiana Space Center, a European-run spaceport on the northeast coast of South America.
The launch window extends for 69 minutes Friday, and the flight will take about a half-hour to deliver the ASTRA 5B and Amazonas 4A spacecraft into their designated geostationary transfer orbit.
The 1.7-mile rollout is set to begin around 10:20 a.m. local time in French Guiana (1320 GMT; 9:20 a.m. EDT) Thursday 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.
The one-hour transfer of the 166-foot-tall launcher to the ELA-3 launch zone will be followed by careful positioning of the rocket's mobile launch platform over the flame trench, then the connection of the rocket with the launch pad's electrical, telemetry and propellant loading systems.
Later Thursday, 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 Friday.
Friday's launch will mark the second Ariane 5 mission of 2014 and will begin a busy period in Arianespace's manifest.
A launch of a Russian Soyuz rocket with the European Union's Sentinel 1A Earth observation satellite is scheduled for April 3, followed by the liftoff of the small-class Vega launcher around April 25 with a remote sensing satellite for the government of Kazakhstan.
Friday's mission was delayed from late 2013 to resolve an unspecified concern with the Amazonas 4A spacecraft, which was built by Orbital Sciences Corp. and is owned by Hispasat of Madrid.
Arianespace shuffled its manifest to accommodate the delay, launching another Ariane 5 mission in early February out of sequence while waiting for Amazonas 4A to be ready.
ASTRA 5B and Amazonas 4A are enclosed inside Ariane 5 rocket's 5.4-meter-diameter (17.7-foot) payload fairing. The satellites are stacked with a Sylda dual-payload adapter, with ASTRA 5B occupying the upper position within the fairing and the smaller Amazonas 4A payload mounted inside the barrel-shaped Sylda adapter in the lower berth.
After a boost from twin solid rocket boosters and a hydrogen-fueled main engine, the Ariane 5 rocket's upper stage will release ASTRA 5B at T+plus 27 minutes, 3 seconds.
ASTRA 5B, built by Airbus Defence and Space for SES of Luxembourg, weighs about 12,700 pounds (5,755 kilograms) at liftoff. Based on the Eurostar E3000 platform, ASTRA 5B carries 40 Ku-band and six Ka-band transponders to serve Eastern European markets with direct-to-home, direct-to-cable and contribution feeds to digital terrestrial television networks.
The satellite will cover Eastern Europe, Russia and neighboring markets, according to SES.
ASTRA 5B also hosts an L-band navigation payload for the European Geostationary Navigation Overlay Service, which augments GPS navigation signals over Europe.
Amazonas 4A's deployment from the Ariane 5 upper stage is expected at T+plus 34 minutes, 37 seconds.
The 6,600-pound (3,000-kilogram) satellite features 24 Ku-band transponders to provide voice, wireless backhaul, Internet and media applications to South America, according to a fact sheet produced by Orbital Sciences, the manufacturer of Amazonas 4A.
ASTRA 5B and Amazonas 4A will be delivered by the Ariane 5 to an orbit with a low point of 155 miles, a high point of 22,205 miles and an inclination of 3 degrees.
The satellites will raise their orbits using on-board thrusters to reach a circular geostationary orbit 22,300 miles over the equator. ASTRA 5B is destined to operate from a position at 31.5 degrees east longitude, and Amazonas 4A is heading for a location a 61 degrees west longitude.
Both spacecraft are designed for 15-year service lives.