1930 GMT (2:30 p.m. EST)
The IXV space plane is now safely aboard the Nos Aries recovery ship nearly 3,000 miles west of Colombia in the equatorial Pacific Ocean.

The 16-foot-long spacecraft was hoisted onto the Italian ship's deck by a crane after divers aboard Zodiac boats deployed to ready the IXV for recovery following splashdown around 1520 GMT (10:20 a.m. EST).

The divers ensured no toxic fumes were coming from the spacecraft.

The ship will begin a trek back to Genoa, Italy, where it will return the IXV to Europe for inspections and analysis.

1530 GMT (10:30 a.m. EST)
The recovery team in the Pacific Ocean, led by IXV contractor Thales Alenia Space, will lift the automobile-sized spacecraft on the deck of the Nos Aries recovery ship. Technicians will decontaminate the space plane of toxic fuels, extract data cards from on-board recorders, then begin the trip back to Europe.

The ship will drop off most of the team in Panama, then transit the Panama Canal and head for port in Genoa, Italy, where it will arrive about 40 days from now.

The IXV will be trucked to ESA's ESTEC facility in the Netherlands for post-flight analysis.

1519 GMT (10:19 a.m. EST)
Splashdown confirmed! The IXV is back on Earth after a 32,400 km flight around the world, demonstrating new technologies for use on a future space plane and reusable launchers.
1515 GMT (10:15 a.m. EST)
Two Zodiac boats have deployed from the Nos Aries ship speeding toward the predicted IXV splashdown point.
1513 GMT (10:13 a.m. EST)
The IXV is descending at 7 meters per second (15 mph), close to its expected speed. The propulsion system has begun a purge of its toxic propellant.
1510 GMT (10:10 a.m. EST)
After deploying a U.S.-made supersonic parachute at Mach 1.5, then a drogue stabilizing chute, the IXV's 30-meter diameter main parachute has opened to slow down its descent for splashdown.
1502 GMT (10:02 a.m. EST)
Acquisition of signal! The IXV is on a nominal trajectory after the most stressful part of re-entry. The space plane will transmit data to the Nos Aries recovery ship from more than 300 sensors mounted aboard the craft recording loads, pressures, strain, and temperatures.
1459 GMT (9:59 a.m. EST)
The IXV should be past the period of peak heating, where temperatures on its nose and flaps reached about 1,700 degrees Celsius (3,092 degrees Fahrenheit). Ceramic matrix and ablative materials cover the IXV to protect its internal structure during re-entry.
1444 GMT (9:44 a.m. EST)
The space plane should now be encountering the upper fringes of Earth's atmosphere at an altitude of 120 kilometers (74 miles).

The target re-entry speed is 7.5 kilometers per second (16,777 mph) to fly a trajectory representative of a return to Earth from low Earth orbit.

The IXV will execute a series of S-turn banking maneuvers, using four hydrazine-fueled thrusters and two electromagnetically-actuated flaps mounted on its aft end to steer toward a landing zone in the equatorial Pacific Ocean west of Colombia.

Once it exits a communications blackout caused by the build-up of plasma around the craft, the IXV will transmit recorded data to engineers via a 2-meter antenna on the Nos Aries recovery ship. This is expected around 1502 GMT (10:02 a.m. EST).

The parachute deployment sequence occurs around 1509 GMT (10:09 a.m. EST). The IXV's main parachute was provided by Zodiac Aerospace, the U.S. company that built parachutes for NASA's Curiosity Mars rover's landing system and the space shuttle drag chute.

Splashdown is expected 102 minutes after launch -- around 1522 GMT (10:22 a.m. EST) -- at a relatively gentle velocity of 6 meters per second (13 mph).

Four airbags will deploy to help the spacecraft float until recovery teams reach it.

1423 GMT (9:23 a.m. EST)
The IXV has passed out of range of ground stations in Gabon and Kenya. The next time engineers hear from the spacecraft will be after a re-entry communications blackout around 1502 GMT (10:02 a.m. EST), when the space plane will begin transmitting to an antenna on the Nos Aires recovery ship in the Pacific Ocean.
1414 GMT (9:14 a.m. EST)
Officials are hailing the Vega rocket's fourth success in four missions since it debuted in 2012, but attention is turning to the progress of ESA's IXV space plane. "That's the end of the Vega mission, and now the IXV mission has just begun," said ESA director general Jean-Jacques Dordain.
1411 GMT (9:11 a.m. EST)
The IXV space plane is passing through the maximum altitude -- about 412 kilometers (256 miles) -- on this test flight. It will pick up speed on descent, reaching about 7.5 kilometers per second -- 16,800 mph -- when it hits the atmosphere at 1444 GMT (9:44 a.m. EST).
1401 GMT (9:01 a.m. EST)
IXV program manager Giorgio Tumino confirms acquisition of signal from IXV via the ground station in Libreville, Gabon. Priming of the space plane's four maneuvering thrusters should begin shortly.
1358 GMT (8:58 a.m. EST)
Separation of IXV confirmed!
1354 GMT (8:54 a.m. EST)
T+plus 14 minutes. The RD-869 engine, provided by Yuzhnoye of Ukraine, has switched off following a successful first burn.

Separation of the IXV space plane is expected at T+plus 17 minutes, 49 seconds.

Two more AVUM firings will occur after IXV separation, boosting the stage away from the space plane and toward its own destructive re-entry.

1352 GMT (8:52 a.m. EST)
T+plus 12 minutes. The AVUM stage's RD-869 engine provided by Ukraine continues firing at an altitude of 280 km over the Atlantic Ocean. Shutdown is set for T+plus 13 minutes, 49 seconds.
1348 GMT (8:48 a.m. EST)
The AVUM fourth stage's Ukrainian engine is now firing to inject the Vega and its payload into a target orbit with a high point of 416 km, a low point of 76 km, and an inclination of 5.4 degrees.

The low point of this orbit is within Earth's atmosphere, and will cause the IXV to re-enter in less than one orbit, aiming for a splashdown in the Pacific Ocean.

1346 GMT (8:46 a.m. EST)
T+plus 6 minutes, 40 seconds. Burnout and separation of the Zefiro 9 third stage motor. The Ukrainian-made fourth stage engine will ignite at T+plus 8 minutes.
1345 GMT (8:45 a.m. EST)
T+plus 5 minutes, 15 seconds. The third stage Zefiro 9 motor will burn out in about a minute.
1344 GMT (8:44 a.m. EST)
T+plus 4 minutes, 10 seconds. The clamshell-like 8.5-foot-diameter Swiss-built payload fairing has been jettisoned.
1343 GMT (8:43 a.m. EST)
T+plus 3 minutes, 55 seconds. The Zefiro 23 seconds stage has burned out and separated, giving way to the third stage Zefiro 9A motor, which is now firing at a downrange distance of 470 kilometers. Velocity is now 3.83 kilometers per second.
1342 GMT (8:42 a.m. EST)
T+plus 2 minutes. First stage shutdown and separation confirmed after consuming 194,000 pounds of solid propellant, and Vega's Zefiro 23 second stage has ignited.
1341 GMT (8:41 a.m. EST)
T+plus 1 minute. Now approaching 50,000 feet high, Vega has surpassed the region of maximum aerodynamic pressure. The first stage P80FW motor, the largest single-segment solid rocket ever built, continues firing as expected.
1340 GMT (8:40 a.m. EST)
T+plus 40 seconds. The 98-foot-tall Vega rocket is racing into the morning sky over the Guiana Space Center, already surpassing the speed of sound.
1340 GMT (8:40 a.m. EST)
LIFTOFF! The Vega rocket has launched on its fourth mission with Europe's Intermediate Experimental Vehicle, a re-entry demonstrator that could pave the way for future European reusable launchers and space planes.
1339 GMT (8:39 a.m. EST)
T-minus 60 seconds and counting.
1338 GMT (8:38 a.m. EST)
T-minus 90 seconds and counting. The four-stage launcher is being transitioned to internal battery power and disconnected from its ground power source.
1338 GMT (8:38 a.m. EST)
T-minus 2 minutes and counting. The target launch time of 1340 GMT is being loaded into the Vega's on-board computer.
1337 GMT (8:37 a.m. EST)
T-minus 3 minutes and counting. The IXV payload should be on internal power at this time.
1336 GMT (8:36 a.m. EST)
T-minus 4 minutes and counting. The synchronized launch sequence has begun for the Vega's final countdown. This computer-controlled sequence monitors thousands of parameters in the countdown's last moments, ensuring all systems are ready for flight.
1328 GMT (8:28 a.m. EST)
NEW LAUNCH TIME. The Vega rocket is targeted for launch at 1340 GMT (8:40 a.m. EST) with Europe's experimental IXV space plane. The countdown will resume from T-minus 4 minutes and begin the final synchronized sequence.
1315 GMT (8:15 a.m. EST)
There is a problem with a telemetry link between the vehicle and the ground. Engineers are evaluating the issue.
1258 GMT (7:58 a.m. EST)
The problem that caused the hold in the Vega countdown appears to be a ground system issue.

Today's launch window extends to 1443 GMT (9:43 a.m. EST), so there is some time to resolve the problem.

1256 GMT (7:56 a.m. EST)
HOLD. The Vega countdown has stopped at T-minus 4 minutes, 25 seconds. The stoppage occurred just before the countdown was to enter the final computer-controlled synchronized sequence.
1253 GMT (7:53 a.m. EST)
T-minus 7 minutes and counting. The countdown's synchronized sequence begins at T-minus 4 minutes.
1250 GMT (7:50 a.m. EST)
The final weather check shows all conditions are green for launch tonight.
1244 GMT (7:44 a.m. EST)
The Vega rocket, IXV re-entry vehicle, weather conditions and high-altitude winds are GO for launch at 1300 GMT (8 a.m. EST).
1235 GMT (7:35 a.m. EST)
Live streaming video from the Guiana Space Center is due to begin in about 5 minutes.

The synchronized launch sequence takes over the countdown about four minutes prior to liftoff. The computer-controlled final sequence checks thousands of parameters in the final steps of the countdown.

After liftoff, Vega will clear the pad's four lightning towers and pitch east from the Guiana Space Center, heading over the Atlantic Ocean and surpassing the speed of sound in about 30 seconds.

The Vega's solid-fueled P80FW first stage, producing a maximum of 683,000 pounds of thrust, burns out 112 seconds after liftoff, giving way to the launcher's Zefiro 23 second stage at an altitude of about 33 miles.

After a 102-second burn, the second stage consumes its propellant 3 minutes, 35 seconds after launch and separates. The Vega's third stage, the Zefiro 9A motor, ignites about 3 minutes, 51 seconds into the mission.

A few seconds later, Vega's 8.5-foot-diameter payload fairing will jettison.

Vega's third stage fires for more than two minutes, turning off and separating 6 minutes, 37 seconds after liftoff.

The fourth stage, known as AVUM, ignites its liquid-fueled Ukrainian engine eight minutes into the mission, burning nearly six minutes to reach the proper suborbital trajectory for the IXV mission.

Separation of the IXV payload is expected 17 minutes, 49 seconds into the flight.

The AVUM fourth stage will fire two more times as the IXV flies its mission to separate itself from the space plane, targeting its own destructive re-entry on a path safely away from the IXV.

For more details, check out the launch timeline.

1230 GMT (7:30 a.m. EST)
T-minus 30 minutes and counting. The downrange tracking stations report they are ready for launch, and the rocket is now being configured to enter the synchronized countdown sequence.

The Vega rocket will fly on an initial launch azimuth of 82 degrees, just south of due east. The IXV mission will cover about 32,400 kilometers (20,132 miles) on its 102-minute flight.

1215 GMT (7:15 a.m. EST)
T-minus 45 minutes. Some statistics on today's flight:
1200 GMT (7:00 a.m. EST)
T-minus 60 minutes and counting. There continue to be no problems reported in the countdown for launch of Vega this morning. Liftoff is set for 1300 GMT (8 a.m. EST; 10 a.m. local time) from French Guiana.
1151 GMT (6:51 a.m. EST)
At this point in the countdown, the Vega rocket's telemetry transmitters have been activated and are being tested to ensure good links with ground control centers in Kourou.
1050 GMT (5:50 a.m. EST)
All systems are reported to be "go" for launch today in a launch window opening at 1300 GMT (8 a.m. EST) and extending an hour and 43 minutes.

So far in the countdown, Vega's systems have been powered on and launch controllers have checked communications, tracking and command links between the rocket and ground facilities at the Guiana Space Center.

Officials confirm the launch pad's 16-story mobile gantry is now in its launch position about 260 feet from the rocket.

The IXV payload mounted on top of the Vega rocket is being checked out by a control team based in Turin, Italy, at the Thales Alenia Space facility where the spacecraft was manufactured.

The 270-square-mile space center, run by the French space agency, CNES, and the European Space Agency, is located on the jungle coastline of French Guiana, situated on the northeast corner of South America.

The Vega launch pad, known by its French acronym SLV, is about 1 kilometer southwest of the Ariane 5 launch complex. It was built on the former site of ELA-1, the home of Ariane 1, Ariane 2 and Ariane 3 launchers from 1979 until 1989.

Construction of the Vega launch pad began in 2004, including the building of a new 16-story mobile gantry weighing some 1000 metric tons. A fixed umbilical mast standing 105 feet tall provides air conditioning to the Vega's payload.

Workers also added four lightning towers at the pad to protect the Vega rocket from thunderstorms.

Unlike the Ariane 5 rocket, the Vega's stages are stacked on the pad inside the mobile gantry, which provides protection of the launcher from weather at the spaceport.

Vega's countdown is managed from Guiana Space Center's prime control center less than a mile from the launch pad, the same building where Ariane 5's countdown is controlled.

0650 GMT (1:50 a.m. EST)
Weather is expected to be favorable in Kourou this morning, with little chance of lightning that could prevent liftoff of the Vega rocket. The launch window opens at 1300 GMT (8 a.m. EST) and extends for an hour and 43 minutes, allowing plenty of time for any inclement weather to clear.

A first look at high-altitude winds show conditions aloft to be acceptable for the launch. Weather balloons will be sent skyward over the next few hours, with the final upper level wind data expected at T-minus 20 minutes.

0545 GMT (12:45 a.m. EST)
Launch preparations are beginning in French Guiana and at ground sites around the world ahead of the 1300 GMT (8 a.m. EST) launch of Europe's Intermediate Experimental Vehicle.

Ground teams at tracking stations in Libreville, Gabon, and Malindi, Kenya, are establishing communications links with the IXV's control center, named ALTEC, at Thales Alenia Space in Turin, Italy.

Over the next few hours, the 98-foot-tall Vega launcher's avionics systems, computer and transmitters will be activated for testing.

European engineers are eager to test an experimental re-entry demonstrator Wednesday to validate technologies for future robotic exploration probes, winged space planes, and reusable rocket boosters.

The European Space Agency's Intermediate Experimental Vehicle -- about the size of a family car -- will take off at 8 a.m. EST (1300 GMT) Wednesday aboard a Vega rocket from the Guiana Space Center on the northern coast of South America.

The launch window extends for an hour and 43 minutes for the 98-foot-tall Vega rocket to blast off and propel the IXV spaceship on a suborbital trajectory around the world, aiming for a precision parachute-assisted splashdown in the Pacific Ocean about 102 minutes later.

The mission passed a launch readiness review Monday, clearing the Vega launch team for final preparations for liftoff Wednesday.

"We have done the preparations for the IXV," said Giorgio Tumino, EXA's IXV program manager, in a phone interview from the launch site in Kourou, French Guiana. "Everything went smooth, and we are ready for the launch on the 11th. All our ground segment works perfectly, and our spacecraft is also ready. We do not expect any delay, apart from meteorological issues."

Built by Thales Alenia Space of Italy, the European mini-shuttle weighs nearly 2 metric tons -- about 4,000 pounds -- and measures 5 meters long, or more than 16 feet. The IXV's aerodynamic lifting body shape will help the craft steer its way to a landing point in the equatorial Pacific Ocean nearly 3,000 miles west of Colombia.

Tumino says the mission will help Europe close the loop on space systems from launch, to in-space operations, then returning to Earth.

"Europe has leadership in going to orbit," Tumino said. "We have the long history of the Ariane family up to the Ariane 5, and we have also the success of the new Vega launcher. We believe the European know-how in getting to orbit is quite good. We also believe that European competencies in operating advanced systems in space is among the best worldwide, with the ATV (space station supply ship) and the Rosetta mission (to comet 67P/Churyumov-Gerasimenko).

"We believe the return capability is running behind," Tumino said. "We never closed the loop on the capability to go to orbit, operate in orbit and come back from orbit. The first objective of the IXV mission is we need to gain experience on these type of missions -- the capability to return from orbit."

A recovery team on the Italian Nos Aries vessel will pluck the IXV from the Pacific Ocean and return it to Europe for analysis.