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"Following the announcement made by Arianespace on the anomalies of the orbit injection of the Galileo satellites, the teams of industries and agencies involved in the early operations of the satellites are investigating the potential implications on the mission," ESA said in a statement.
"Both satellites have been acquired and are safely controlled and operated from ESOC, ESA's Operations Centre in Darmstadt, Germany," the statement said.
"Further information on the status of the satellites will be made available after the preliminary analysis of the situation."
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The second Fregat burn will begin at T+plus 3 hours, 39 minutes to place the Galileo satellites into a circular orbit at an altitude of 23,522 kilometers (14,619 miles) at an inclination of 55.04 degrees.
It is currently 9:17 a.m. in French Guiana.
The two 730-kilogram (1,609-pound) Galileo satellite are being configured for launch.
The Soyuz countdown sequence begins 6 minutes, 10 seconds prior to liftoff, then the Fregat upper stage will transition to internal power five minutes before launch.
The umbilical arm servicing the upper stage and payloads will pull away at T-minus 2 minutes, 25 seconds. The Soyuz rocket is operating on internal power at T-minus 40 seconds, and the final servicing mast retracts from the rocket 20 seconds later.
The ignition sequence of the Soyuz rocket's kerosene-fueled core stage and four strap-on boosters begins 17 seconds before liftoff, and all engines should be at full thrust three seconds before launch.
See our countdown timeline for more details.
The 1,609-pound satellites mounted side-by-side on top of the Soyuz rocket were manufactured by OHB System of Bremen, Germany. They carry L-band navigation payloads supplied by Surrey Satellite Technology Ltd.
Once deployed from the launcher's Fregat-MT upper stage, the satellites will extend their solar arrays and begin a week-long phase of initial activations and tests, according to Javier Benedicto, the European Space Agency's Galileo project manager.
"We will then start the drift maneuvers from the injection point to their final orbital slots," Benedicto said. "This will take a couple of weeks. While we do that, we activate the platform and we start the platform and later the payload in-orbit test activities."
"We have about 73 days of test activities all together. By mid-november, it will be about that point in time when we will declare the spacecraft operational from a user point-of-view and we will broadcast the navigation messages," Benedicto said.
The satellites join four other Galileo satellites launched in 2011 and 2012 to validate the network's design -- in space and on the ground. One of the Galileo in-orbit validation, or IOV, satellites is currently offline as engineers investigate a problem that caused "permanent degradation" on two of its three navigation bands, according to Benedicto.
But officials cleared the satellites on Friday's launch of any faults that may have caused the problem on the validation spacecraft.
Twenty more Galileo satellites are being built and tested to launch on Soyuz and Ariane 5 rockets through 2017 to populate the constellation, which will consist of 30 satellites in orbit at a given time, including spares.
"We will be in a position to have 26 spacecraft in orbit, which is the 4 IOV and the 22 spacecraft under production, in the year 2017," Benedicto said.
The European-funded, Russian-built pad is located about eight miles northwest of the Ariane 5 and Vega launch pads at the Guiana Space Center. Engineers selected the Soyuz launch site based on terrain, geology and a location away from Ariane facilities to ensure they did not interfere with each other.
It took three years and cost European governments $800 million to build the Soyuz launch facility, which is known by its French acronym ELS. Other than the 17-story mobile servicing tower and four lightning masts, the launch pad is modeled after the Soyuz launch pad at the Baikonur Cosmodrome in Kazakhstan.
This morning's launch is the ninth Soyuz to fly from ELS.
The Soyuz pad includes blue and yellow umbilical arms and hold-down petals at the base of the rocket. On the back side of the pad is a deep flame trench dug out of granite bedrock. The facility also houses living quarters for Russian workers and a launch control center.
The Soyuz site lies closer to the town of Sinnamary than Kourou, which is more typically associated with the spaceport.
The next milestone in the countdown will be retraction of the Soyuz rocket's mobile gantry. Engineers are currently configuring the servicing tower to move to a point about 260 feet from the Soyuz rocket.
The Soyuz rocket with Galileo satellites on-board is a modernized version of the venerable Russian launcher with an automated digital control system and an upgraded RD-0124 third stage engine. It also has a flight termination system that can receive commands from safety officials on the ground in the event of a mishap, a key difference between the Soyuz rockets flying from French Guiana and Russian launch sites.
The Soyuz launching this evening is known as the Soyuz ST-B or Soyuz 2-1b configuration.
Other upgrades for Soyuz launchers based in French Guiana include an S-band telemetry system, modifications to cope the the humid tropical climate, and valves in the rocket's fuel tanks to allow empty stages to sink in the Atlantic Ocean. Soyuz launches from Kazakhstan or Russia drop their stages on land.
After liftoff, the rocket will go through pitch and roll programs to align with a northeasterly trajectory from the launch pad near Sinnamary, French Guiana. After a nearly 10-minute flight powered by the Soyuz rocket's three core stages, a Fregat-MT upper stage will take over for two burns before releasing the pair of Galileo satellites into a circular orbit 14,615 miles (23,522 kilometers) above Earth at an inclination of 55.04 degrees.
See our launch timeline for more details.
Some statistics on today's flight:
The launch team has completed electrical checks after turning on the Soyuz rocket's avionics systems, and the process to fill the three-stage launcher with liquid oxygen and kerosene has begun.
Fueling should be complete about two hours before liftoff.
Liftoff from the Soyuz launch pad in the northwest sector of the Guiana Space Center on the northern coast of South America is set for 1227:11 GMT (8:27:11 a.m. EDT).
The first two fully operational satellites for Europe's Galileo navigation system are inside the Soyuz rocket's nose fairing, ready to begin a nearly three-month commissioning and checkout in orbit before going active in November. They will join four other Galileo satellites launched in 2011 and 2012 to validate the network.
The Galileo program is Europe's counterpart to the U.S. Air Force's Global Positioning System, which provides positioning data to military planes, smart bombs, civilian phones and auto navigation systems.
The Soyuz rocket will fly in the Soyuz 2-1b version - also known as the Soyuz ST-B configuration, with a modernized digital control system, an upgraded RD-0124 third stage engine and an ST-type payload fairing with a diameter of 13.4 feet.
Following a state commission meeting of mission managers, the Soyuz rocket will be filled with liquid oxygen and kerosene propellants beginning about four hours before liftoff, according to information released by Arianespace, the commercial operator for Soyuz rocket missions in French Guiana.
The launch pad's 174-foot-tall mobile gantry will be retracted about an hour before launch, moving into position about 260 feet from the Soyuz rocket.
After a computerized sequence, the 151-foot-tall launcher will ignite its main engines and blast off, turning northeast from the French Guiana spaceport and shedding strap-on boosters less than two minutes into the mission.
The Soyuz rocket's second and third stages will accelerate a Fregat upper stage and the two Galileo satellites on a suborbital trajectory before giving way to the Fregat engine for two burns to put the spacecraft in the proper orbit. If launch occurs Friday, separation of the Galileo satellites is scheduled for 1615 GMT (12:15 p.m. EDT), according to Arianespace.
The launch is targeting an orbit with an altitude of about 14,615 miles and an inclination of 55.04 degrees.
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The launch site has been under the influence of a tropical wave for most of the week, bringing strong winds to the area. But the disturbance is moving into the West Indies and improved conditions are expected at the Guiana Space Center tomorrow.
The Soyuz rocket and its two Galileo satellite payloads remain in good shape for launch.
Launch time for Friday is set for 1227 GMT (8:27 a.m. EDT; 9:27 a.m. French Guiana time).
The three-stage launcher completed the 700-meter (2,300-foot) transfer from a horizontal integration hangar to the launch pad Monday morning, then was hydraulically hoisted vertical over the pad's concrete flame bucket.
The Soyuz rocket is set for liftoff Thursday at 1231:14 GMT (8:31:14 a.m. EDT; 9:31:14 a.m. French Guiana time) from a purpose-built launch facility at the European-run Guiana Space Center.
Its mission is to release a pair of navigation satellites into orbit 14,615 miles above Earth.
The Soyuz booster was pieced together inside its integration building, known as the MIK, over the last few weeks. After the rocket's arrival at the launch pad, workers planned to move the facility's mobile gantry in place around the launcher to prepare for the arrival of the mission's payloads.
The rocket's Fregat-MT upper stage and two satellite passengers -- encapsulated inside an aerodynamic shroud -- were supposed to be delivered to the launch pad Monday evening for lifting and attachment to the Soyuz third stage overnight.
The Soyuz rocket will fly in the Soyuz 2-1b version -- also known as the Soyuz ST-B configuration -- with a modernized digital control system, an upgraded RD-0124 third stage engine and an ST-type payload fairing with a diameter of 13.4 feet.
The two Galileo payloads set for launch Thursday will join four craft launched in 2011 and 2012, continuing the deployment of 30 satellites to build out Europe's counterpart to the U.S. Air Force's Global Positioning System.
The Galileo navigation system is a joint project between ESA and the European Commission, the executive body of the European Union.
The satellites launching Thursday were built by OHB System of Germany. Their navigation payloads come from Surrey Satellite Technology Ltd. of the United Kingdom.
The satellites are the first to launch in the Galileo program's Full Operational Capability, or FOC, phase. The four satellites launched in 2011 and 2012 validated the Galileo concept -- in space and on the ground.
Officials say positioning fixes and timing data from the satellites met expectations, with further improvements expected with the launch of additional satellites.
Each spacecraft launching Thursday weighs about 730 kilograms, or 1,609 pounds, with a full load of propellant.
After launching from French Guiana, the Soyuz rocket's three core stages will boost the satellites and the Fregat-MT upper stage on a suborbital trajectory in the first 9 minutes of the mission.
The Fregat upper stage will ignite its main engine twice, first to reach a preliminary elliptical parking orbit. After coasting through space more than 3 hours, the Fregat's engine will fire again to circularize its orbit at an altitude of approximately 23,500 kilometers (14,600 miles) with an inclination of 55 degrees.
Separation of the satellites is scheduled for 1619 GMT (12:19 p.m. EDT; 1:19 p.m. French Guiana time).