BY SPACEFLIGHT NOW

Follow the preparations and launch of the Arianespace Ariane 5 rocket carrying the European Space Agency's Rosetta comet explorer. Reload this page for the very latest on the mission.

TUESDAY, MARCH 2, 2004
1015 GMT (5:15 a.m. EST)

Embarking on its epic voyage to gain new insights into comets and the history of our solar system, the Rosetta spacecraft was successfully launched today to rendezvous with a cosmic snowball and deploy a tiny lander onto its icy heart. Read our full launch story.

0939 GMT (4:39 a.m. EST)

European Space Agency Director General Jean-Jacques Dordain reports that controllers are establishing contact with Rosetta.

Rosetta is in a looping solar orbit that will see it intercept Earth a year from now for a pivotal sling-shot fly-by, receiving a gravity assist on its trajectory to ultimately reach the comet. The craft will later fly past Mars and Earth in 2007 and Earth once again in 2009.

0936 GMT (4:36 a.m. EST)

"Bravo Ariane!" says Arianespace Chief Executive Officer Jean-Yves Le Gall from the mission control center as officials declare today's launch a success.

0932 GMT (4:32 a.m. EST)

Plus+2 hours, 15 minutes. SPACECRAFT SEPARATION! The European Space Agency's Rosetta spacecraft has been released from the Ariane 5 rocket following today's launch on a decade-long mission to explore comet Churyumov-Gerasimenko.

0931 GMT (4:31 a.m. EST)

Plus+2 hours, 13 minutes, 42 seconds. Burn complete! The Ariane 5 rocket's Storable Propellant Stage has finished firing its Aestus engine, concluding the powered phase of this morning's launch. The stage is now reorienting to prepare for deployment of Rosetta.

0929 GMT (4:29 a.m. EST)

Plus+2 hours, 12 minutes. The rocket and Rosetta have zoomed past their close approach to Earth. They are now powering away from the planet. Altitude is 773 km, velocity is 10.2 km/sec.

0922 GMT (4:22 a.m. EST)

Plus+2 hours, 5 minutes. This burn will conclude once the rocket's onboard computer system determines that the "aimed orbit" has been reached for Rosetta. Achieving an Earth-escape, Rosetta will be deployed on its 10-year, looping voyage to comet Churyumov-Gerasimenko.

0915 GMT (4:15 a.m. EST)

Plus+1 hour, 58 minutes. The 17-minute firing of the upper stage remains underway. Altitude is 540 km, velocity is 7.8 km/sec.

0914 GMT (4:14 a.m. EST)

Plus+1 hour, 56 minutes, 45 seconds. Ignition! The upper stage of Ariane 5 -- called the Storable Propellant Stage -- has fired to life for its burn to boost Rosetta on its trek to the comet.

0910 GMT (4:10 a.m. EST)

Plus+1 hour, 53 minutes. Altitude is 1,000 km, velocity is 7.2 km/sec. The arcing ballistic trajectory is bring the launcher and attached payload back toward Earth in advance of engine ignition.

0857 GMT (3:57 a.m. EST)

Plus+1 hour, 40 minutes. The upper stage with Rosetta continues in the ballistic coast. Ignition of the rocket stage is coming up in approximately 15 minutes.

0827:44 GMT (3:27:44 a.m. EST)

Plus+70 minutes. Today's flight of Ariane 5 is the first to use the A5G+ configuration distinguished by the new composite structure for the cylindrical vehicle equipment bay housing the rockets's guidance system and avionics and additional propellant in the upper stage.

The new bay structure decreases the mass by 100 kg but decreases the level of shock experienced during the in-flight separation between the rocket's main cryogenic stage and the upper stage. The bay is a cylinder that wraps around the upper stage.

The particular upper stage being used today is different from previous ones flown on earlier Ariane 5 mission. The hydrazine fuel tanks of the Storable Propellant Stage are larger, allowing 250 kg additional propellant to be carried. Also for this mission, the complete upper stage including all systems such as engine, tanks and feeder systems underwent specific testing and re-qualification.

0729 GMT (2:29 a.m. EST)

Plus+12 minutes. The upper stage and attached Rosetta spacecraft are presently on an arcing ballistic trajectory that will last over 90 minutes. They will travel about 3,800 km away from the planet before heading back toward Earth. Ignition of the upper stage occurs roughly 650 km in altitude. As the motor accelerates Rosetta, the duo will pass within 225 km of Earth before soaring away from our home planet.

0728 GMT (2:28 a.m. EST)

Plus+10 minutes, 30 seconds. Engine cutoff and stage separation! The Ariane 5 rocket's Main Cryogenic Stage's Vulcain engine shut down following its firing and the spent stage has been separated from the upper stage with Rosetta.

The Main Cryogenic Stage is suborbital, meaning it will naturally fall back to Earth before even completing a single orbit. It will burn up over the Pacific Ocean, breaking up at an altitude of between 80 and 60 km under the loads due to atmospheric re-entry.

0727 GMT (2:27 a.m. EST)

Plus+9 minutes, 30 seconds. Coming up on main stage shutdown. The rocket is beginning to gain altitude again. Altitude is 158 km, velocity is 7.5 km/sec.

0724 GMT (2:24 a.m. EST)

Plus+8 minutes, 15 seconds. Altitude is 150 km, velocity is 5.9 km/sec.

0722 GMT (2:22 a.m. EST)

Plus+6 minutes, 15 seconds. The rocket is no longer climbing in altitude in order to gain speed. Altitude is 158 km, velocity is 3.4 km/sec.

0720 GMT (2:20 a.m. EST)

Plus+4 minutes. Altitude is 131 km, velocity is 2.6 km/sec.

0720 GMT (2:20 a.m. EST)

Plus+3 minutes, 15 seconds. The bullet-shaped protective nose cone enclosing Rosetta has separated from the Ariane 5. Two pyrotechnic devices -- one horizontal and the other vertical -- is used to separate the fairing's two halves. The vertical device imparts enough impulse to the separated fairings to clear them away laterally.

Altitude is 108 km, velocity is 2.3 km/sec.

0719 GMT (2:19 a.m. EST)

Plus+2 minutes, 30 seconds. The solid rocket boosters have been jettisoned from the Ariane 5 rocket's core stage. The liquid-fueled Vulcain 1 main engine continues to fire to propel the vehicle and Rosetta to space.

0719 GMT (2:19 a.m. EST)

Plus+1 minute, 30 seconds. About one minute left in the burn by the solid rocket boosters. The boosters are providing 90 percent of the liftoff thrust.

0718 GMT (2:18 a.m. EST)

Plus+1 minute. The twin solid rocket boosters and liquid-fueled main stage engine continue to fire as the Ariane 5 rocket blasts into the predawn darkness.

0718 GMT (2:18 a.m. EST)

Plus+35 seconds. The launch vehicle has performed its pitch and roll maneuvers for the flight downrange, heading eastward from the South American coast.

0717 GMT (2:17 a.m. EST)

LIFTOFF! The Rosetta spacecraft begins its journey to comet Churyumov-Gerasimenko aboard the Arianespace Ariane 5 rocket!

0717:04 GMT (2:17:04 a.m. EST)

Minus-40 seconds. The vehicle is now switching to internal power.

0716:44 GMT (2:16:44 a.m. EST)

Minus-1 minute. A fast-paced series of events leading to launch will begin at Minus-37 seconds when the automated ignition sequence is started. The water suppression system at the launch pad will start at Minus-30 seconds. At Minus-22 seconds, overall control will be given to the onboard computer. The Vulcain main engine will be readied for ignition with hydrogen chilldown starting at Minus-18 seconds. 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.

0715:44 GMT (2:15:44 a.m. EST)

Minus-2 minutes. The Vulcain 1 main engine supply valves are being opened. Also, the ground valves for engine chilldown are being closed.

0714:44 GMT (2:14:44 a.m. EST)

Minus-3 minutes. The scheduled launch time has been loaded into the rocket's main computer system. The main stage tank pressures should now be at flight level.

0713:44 GMT (2:13:44 a.m. EST)

Minus-4 minutes. Pressurization is now underway for the main cryogenic stage's liquid oxygen and hydrogen tanks. Also, final pyrotechnic arming is starting.

0711:44 GMT (2:11:44 a.m. EST)

Minus-6 minutes and counting. Liquid hydrogen and liquid oxygen supplies of the main cryogenic stage are being verified at flight level. Also, the pyrotechnic line safety barriers are being armed.

0711 GMT (2:11 a.m. EST)

Minus-6 minutes, 30 seconds and counting. The Synchronized Sequence has started. Computers are now in control of this final segment of the launch countdown to prepare the rocket and ground systems for liftoff. There are two computers running the countdown -- one aboard the Ariane 5 and a redundant one at the ELA-3 launch complex.

0707:44 GMT (2:07:44 a.m. EST)

Minus-10 minutes and counting. The status panel in the Jupiter Control Center at Kourou remains green, indicating all remains in readiness for liftoff. The Ariane 5 is fueled, weather conditions are favorable and there are no troubles with the rocket, payload or ground support equipment.

0658 GMT (1:58 a.m. EST)

The final minutes of the countdown are ticking at the Guiana Space Center for today's launch of the Rosetta spacecraft aboard the Ariane 5 rocket. Liftoff is scheduled for 0717:44 GMT.

The European Space Agency's Rosetta mission represents several historic firsts:

• Rosetta will be the first spacecraft to orbit a comets nucleus.
• It will be the first spacecraft to fly alongside a comet as it heads towards the inner Solar System.
• Rosetta will the first spacecraft to examine from close proximity how a frozen comet is transformed by the warmth of the Sun.
• Shortly after its arrival at Comet Churyumov-Gerasimenko, the Rosetta orbiter will despatch a robotic lander for the first controlled touchdown on a comet nucleus
• The Rosetta landers instruments will obtain the first images from a comets surface and make the first in-situ analysis to find out what it is made of.
• On its way to Comet Churyumov-Gerasimenko, Rosetta will pass through the main asteroid belt, with the option of a first close encounter with one or more of these primitive objects
• Rosetta will be the first spacecraft ever to fly close to Jupiter's orbit using solar cells as its main power source.

MONDAY, MARCH 1, 2004
1655 GMT (11:55 a.m. EST)

Delayed several days to replace a patch of foam insulation on the Ariane 5 rocket, launch of the Rosetta comet probe has been rescheduled for early Tuesday. Read our full story.

FRIDAY, FEBRUARY 27, 2004
0700 GMT (2:00 a.m. EST)

Launch of Europe's ambitious Rosetta mission to orbit a comet and deliver a tiny lander onto the icy surface has been postponed yet again -- this time by insulating foam that detached from the Ariane 5 rocket's main stage. Read our full story.

0620 GMT (1:20 a.m. EST)

Today's launch attempt was called off because a piece of insulating foam became detached from the Ariane 5 rocket's main stage.

The liftoff is tentatively rescheduled for early next week, the European Space Agency said.

0610 GMT (1:10 a.m. EST)

SCRUB! The Rosetta spacecraft won't be launching today. A technical issue with the Ariane 5 rocket has cropped up, delaying the mission further. Details about the problem and a new launch date have not been announced by Arianespace.

THURSDAY, FEBRUARY 26, 2004

A second countdown is underway at the Guiana Space Center for the launch of Rosetta atop the Ariane 5 rocket. Liftoff is scheduled for 0736:50 GMT (2:36:50 a.m. EST) Friday -- the day's single instant in which launch could occur.

Arianespace says the winds aloft are expected to be more favorable this evening. Conditions were unacceptable for a launch Thursday morning.

The rocket's main stage had been fueled with liquid hydrogen and liquid oxygen during Wednesday night's countdown. The super-cold cryogenics were offloaded following the scrub. Now, the first stage will be refilled for this next launch attempt.

0720 GMT (2:20 a.m. EST)

SCRUB! Today's launch of the Ariane 5 rocket carrying the Rosetta spacecraft has been postponed due to unfavorable high-altitude winds. Liftoff has been rescheduled for early Friday morning.

"We have a weather no-go because of the winds at altitude. As we only have an instant launch window for this evening, it is not possible to go ahead with the launch and it is not possible to do anything other than come back tomorrow, same place, same time for the second attempt," Jean-Yves Le Gall, the chief executive officer of Arianespace said in announcing the scrub.

WEDNESDAY, FEBRUARY 25, 2004

Europe's vaunted $1 billion Rosetta comet explorer is poised to set off on its decade-long journey early Thursday morning from the same South American launch site that hosted the start of the continent's first deep space mission 19 years ago.

In the last major event before the final countdown begins, the Ariane 5 rocket rolled out of its assembly building to the launch pad Tuesday.

A year later than first planned, Rosetta is due to begin its lengthy voyage Thursday at 0736:49 GMT (2:36:49 a.m. EST) from the ELA-3 launch pad in Kourou, French Guiana.

Overall, officials have until March 17 to get Rosetta off the ground or else await another launch opportunity.

It will take more than two hours for Rosetta to be delivered into a solar orbit that will see it intercept Earth again next March for a pivotal gravity assist fly-by.

Rosetta will be setting off toward comet Churyumov-Gerasimenko, an icy space rock the size of a small town that was selected for investigation last spring after the first opportunity to send Rosetta to another comet was passed up due to concerns with the reliability of its Ariane 5 rocket.

Before arriving in orbit around the comet in the summer of 2014, the Rosetta probe will swing by Earth three times and Mars once to put it on course to intercept Churyuomov-Gerasimenko when it dips back into the inner solar system in the next decade.

Rosetta will also be put in a hibernation period from July 2011 to January 2014 when all systems except the main computer will be switched off.

Once in orbit, Rosetta will drop a small 200-pound lander onto the surface to carry out its own experiments. The orbiter will continue observations of the primordial space rock for several months until late 2015 when the comet makes its closest approach to the Sun.

After the 6,743-pound Rosetta was attached to the Ariane 5 upper stage February 16, the two halves of the Ariane's payload fairing were placed around the probe on February 18.

The storable propellant upper stage was filled with its load of hydrazine fuel and nitrogen tetroxide oxidizer last Thursday, February 19, followed the next day by a final countdown and launch rehearsal for the team.

Senior officials gathered on Monday to confirm the readiness of the vehicle for flight. Having issued formal permission to proceed with preparations, additional work was done to ready the rocket to roll to the launch pad Tuesday.

The final countdown will get underway Wednesday at 2007 GMT (3:07 p.m. EST). A check of electrical systems is scheduled to occur at 0007 GMT Thursday (7:07 p.m. EST Wednesday). At 0247 GMT (9:47 p.m. EST), super-cold liquid hydrogen and liquid oxygen propellants will begin flowing into the Ariane 5's massive cryogenic first stage to fuel its single Vulcain powerplant. A chilldown of the Vulcain engine will take place at about 0417 GMT (11:17 p.m. EST). A final check of connections between the launcher and telemetry, tracking, and command systems is slated for around 0627 GMT (1:27 a.m. EST).

If all systems are deemed ready for launch, controllers will allow the countdown to enter a computer-controlled phase known as the synchronized launch sequence seven minutes prior to liftoff. Following this critical milestone is a series of fast-paced events culminating with ignition of the Vulcain main engine when the count reaches zero. The twin solid rocket boosters will fire to life seven seconds later, followed immediately by liftoff.

Flight 158 will follow a unique launch profile on its mission to place Rosetta on an Earth escape trajectory and into solar orbit. The solid-fueled boosters will burn for two minutes, 20 seconds before jettisoning. The nose cone shielding Rosetta from the elements is let go about a minute later. The first stage's Vulcain main engine will continue to fire until about ten minutes into flight, when it will shut down having consumed all its fuel.

In a departure from the vast majority of Ariane 5 launches, the upper stage will enter a long coast phase before finally igniting over the Pacific Ocean nearly two hours after liftoff. Burning for 17 minutes, it will inject Rosetta onto the initial course that will ultimately see it arrive in the vicinity of comet Churyumov-Gerasimenko in about 123 months. Separation of the spacecraft from the upper stage is expected about two hours and 15 minutes into the flight.

Flight 158 will mark the 162nd Ariane launch overall since 1979, and the first for the rocket in 2004. It also will be the 18th use of the Ariane 5 rocket since being originally introduced in 1996.

Stay with Spaceflight Now for live play-by-play updates during the launch of the Ariane 5 rocket with Rosetta.

MONDAY, FEBRUARY 16, 2004

The Rosetta comet probe that will embark on its long-awaited journey next week was attached to its Ariane 5 launcher Monday inside a cavernous assembly building at the South American launch site.

Fully fueled with over 3,600 pounds of toxic maneuvering propellant, Rosetta was lowered atop the Ariane 5's upper stage inside the final assembly building at the Guiana Space Center in Kourou, located along South America's northeast Atlantic coast.

The milestone was one met with great anticipation by project officials, with just ten days remaining until Rosetta is placed into solar orbit to begin a voyage to comet Churyumov-Gerasimenko that will span over a decade.

Sitting in a Kourou high bay for the past year after officials elected to opt out of a launch opportunity in 2003 due to rocket concerns, Rosetta began the run-up to a second launch campaign last fall with the testing of key equipment.

Assembly operations for the Ariane 5G+ rocket began January 19, and the vehicle's upper stage was attached January 21. Fueling of the spacecraft with its volatile load of fuel and oxidizer propellant took place over January 27 and 28.

With its twin solid rocket boosters now bolted on, the Ariane 5 rolled out of its launcher integration building February 10 for the half-hour ride on dual rail tracks to the final assembly building where it would soon receive its payload.

With Rosetta now firmly in place atop the Ariane 5 stack, the payload fairing will be attached to enclose the probe for protection during the few minutes of ascent through the atmosphere.

The completed rocket will roll out to the launch pad February 24, in advance of the anticipated liftoff February 26 at 0716 GMT (2:16 a.m. EST) from the ELA-3 pad in Kourou.

Stay with Spaceflight Now for continued updates and extensive coverage of the launch of Rosetta next week.

THURSDAY, JANUARY 15, 2004

Europe's long-awaited Rosetta space probe is being readied for a second time to begin its ambitious mission that will see it embark on a decade-long journey through the solar system before reaching its mysterious icy objective. Read our full story.