A Soyuz rocket boosted two validation platforms from French Guiana into orbit Friday for Europe's Galileo navigation network, setting the stage for further launches every six months over the next few years to build a constellation of satellites beaming global positioning services to airplanes, automobiles and millions of users.

The identical 1,543-pound satellites blasted off at 1815 GMT (2:15 p.m. EDT) atop a 151-foot-tall Soyuz 2-1b launcher, climbing into a mostly clear sky over the Guiana Space Center, a European-run base on the French Guiana coast near the community of Sinnamary.

Read our full story.

Engineers at the Galileo control center in Toulouse, France, have received the first signals from the satellites.

Spacecraft separation! Both Galileo satellites have been released from the Fregat upper stage in orbit 14,400 miles above Earth.

T+plus 3 hours, 41 minutes. Arianespace confirms the successful ignition and cutoff of the second Fregat burn. This 5-minute, 17-second firing was designed to circularize its orbit at about 14,400 miles altitude.

Deployment of the two Galileo satellites is expected at 2159 GMT (5:59 p.m. EDT).

T+plus 3 hours, 30 minutes. The second ignition of the Fregat upper stage is five minutes away.

T+plus 28 minutes. The second ignition of the Fregat upper stage is expected at 2149 GMT (5:49 p.m. EDT) for about five minutes to place the Galileo satellites in a circular orbit about 14,400 miles above Earth.

"As you have just seen, the first part of the mission went smoothly," said Jean-Yves Le Gall, chairman and CEO of Arianespace. "The Soyuz tri-stage worked perfectly. "After this, we had separation of the upper part of the launcher, in other words, the Fregat stage and both Galileo satellites."

The Fregat stage fired for 13 minutes to reach an oval-shaped transfer orbit.

"In about three hours over the south of Australia, there will be a second ignition of Fregat, which will be shorter than the first, and then we'll have separation of the spacecraft."

T+plus 24 minutes, 35 seconds. Fregat shutdown confirmed as the rocket speeds through space at nearly 21,000 mph over Eastern Europe.

T+plus 10 minutes. The third stage engine has shut down and separated from the Fregat-MT upper stage, which will fire in a few seconds to reach orbit.

T+plus 7 minutes. Now being accelerated on the power of its third stage engine, the Soyuz rocket is flying at a speed of 11,100 mph over the Atlantic Ocean.

T+plus 5 minutes, 15 seconds. The second and third stages have separated and the third stage RD-0124 engine is now firing.

Altitude is now 160 kilometers and velocity is nearly 4 kilometers per second.

The 13.5-foot-diameter nose cone has been jettisoned now that the rocket is outside of the lower atmosphere.

T+plus 2 minutes. Separation of the Soyuz rocket's four liquid-fueled strap-on boosters at an altitude of nearly 35 miles.

Liftoff of the Soyuz rocket, adding two new satellites to Europe's growing Galileo navigation system.

T-minus 20 seconds. The upper umbilical has retracted and the ignition sequence has begun.

T-minus 2 minutes.

Five minutes until launch. The Fregat-MT upper stage is being transferred to internal power. Everything is go for launch at 1815 GMT (2:15 p.m. EDT).

The launch key has been installed inside the launch control center, beginning the Soyuz rocket's synchronized countdown sequence.

Ten minutes until liftoff.

Today's launch will use the Soyuz 2-1b version of the venerable Russian booster, featuring advanced digital avionics and an upgraded RD-0124 third stage engine. Thrust from 32 engine nozzles on the first stage will generate more than 900,000 pounds of thrust at liftoff.

The final weather report is expected 10 minutes before launch to check for lightning, but officials anticipate no problems.

Now 17 minutes left in the countdown. Under a brilliant blue sky, the Soyuz rocket shines bright white with frost. Its propellant tanks are full of cryogenic liquid oxygen stored at almost -300 degrees Fahrenheit.

All systems are reported green for liftoff at 1815 GMT (2:15 p.m. EDT).

Follow the 3-hour, 45-minute flight with this launch timeline.

There are 30 minutes left in the countdown, and all systems are reported to be in good shape for launch. The weather outlook looks favorable.

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, the launch pad is modeled after the Soyuz launch pad at the Baikonur Cosmodrome in Kazakhstan.

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 launch site is about six miles northwest of the Ariane launch facilities at the Guiana Space Center and lies closer to the town of Sinnamary than Kourou, which is more typically associated with the spaceport.

With less than one hour left in the countdown, the 170-foot-tall mobile gantry at the Soyuz launch pad has retracted away from the rocket.

Unlike Soyuz pads in Russia and Kazakhstan, the Soyuz launch site in French Guiana features a mobile service structure to protect the rocket from weather and permit the vertical attachment of payloads.

In Russia, the payloads are mated to the Soyuz horizontally, then the rocket rolls out on a train to be lifted upright. In French Guiana, the Soyuz core vehicle is integrated in an assembly building less than a half-mile from the pad, then it's moved to the launch mount and erected. The payload is lifted on top of the rocket about 12 hours later.

Earlier today, Russian control team filled the three-stage Soyuz rocket with kerosene and liquid oxygen propellants. The launcher is now fully-fueled for liftoff at 1815 GMT (2:15 p.m. EDT; 3:15 p.m. local time).

The rocket's Fregat upper stage, which will guide the Galileo satellites into their 14,429-mile-high orbit, consumes storable propellant already loaded inside its fuel tanks.

The Russian State Commission, which includes representatives from organizations involved in the mission, met this morning before fueling to authorize beginning the final countdown.

Check out this timeline of key countdown events.

Two satellites for Europe's Galileo navigation program are awaiting liftoff Friday on a Soyuz rocket, beginning a campaign to validate the system's accuracy and functionality before completing a 30-satellite constellation later this decade.

The in-orbit validation, or IOV, satellites will allow European officials to test Galileo's ability to provide precise positioning, navigation and timing services.

Friday's launch will round out a four-satellite fleet of validation vehicles circling 14,400 miles above Earth. Two nearly identical satellites were launched in October 2011 on another Soyuz rocket.

Read our full story.