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Follow the countdown and launch of the Boeing Delta 2 rocket with NASA's Deep Impact comet spacecraft. Reload this page for the very latest on the mission.

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A daring scientific mission to smash a washing machine-sized bullet into the heart of Comet Tempel 1, excavating a stadium-sized crater to reveal primitive materials left from the solar system's creation for spacecraft and Earth-based telescopes to observe, is poised for blastoff Wednesday from Cape Canaveral, Florida.

NASA's Deep Impact probe will be fired into space atop a Boeing Delta 2 rocket. Liftoff must occur at precisely 1:47:08 p.m. EST (1847:08 GMT) to ensure the craft is dispatched on the correct trajectory for its six-month, 268-million-mile journey to the comet for rendezvous on July 4.

If problems stall the liftoff, engineers have two shots every afternoon through January 28 to launch the $330 million project.

The 126-foot tall rocket will dart off pad 17B on the thrust generated by the liquid-fueled main engine and six solid-fueled motors. A minute into flight, the solids will burn out and separate as three more fire to life.

Heading on an easterly trajectory from the Cape -- along an initial flight azimuth of 101 degrees -- the air-lit solids expend their fuel and jettison just over two minutes after liftoff, leaving the first stage engine to continue the push to space. Four-and-a-half minutes into the launch, the exhausted first stage will shut down its kerosene-fed engine and separate. The liquid-fueled second stage engine then ignites for the first of its two firings during ascent.

The rocket's nose cone that shielded Deep Impact during the climb through the atmosphere is ejected nearly five minutes after liftoff, exposing the craft for the first time.

Within nine-and-a-half minutes, the rocket will achieve a temporary circular orbit 90 miles high with an inclination of 29.7 degrees to the equator. The vehicle coasts in this orbit for about 15 minutes before the second stage engine is re-ignited to fire for a minute and 40 seconds, accelerating into an elliptical orbit with a high point of 2,250 miles, low point of 90 miles and inclination of 28.6 degrees.

Less than a minute after the second stage finishes the burn, tiny thrusters are fired to put the third stage motor and attached Deep Impact satellite into a rapid spin.

Spinning like a child's toy top, the duo is released from the second stage and the solid-propellant third stage ignites for a planned 87-second firing as Deep Impact escapes Earth's orbit for the trek to Tempel 1. Roughly 35 minutes after the launch began, Deep Impact is deployed from the rocket.

"We can only -- in this business we're in -- celebrate one step at a time. We have succeeded in building a terrific spacecraft. The Delta 2 team has made the launch of missions of this type look easy, but we all know that it is inherently very high risk. So we certainly pray for the best," said Orlando Figueroa, director of NASA's Solar System Exploration Division.

"And then we have six more months to get to our destination when the real Deep Impact mission takes place. So good luck to all of us, and go Deep Impact!"

"I remember the Launch Services Program began working this mission back in 1999," added Omar Baez, the NASA launch manager at the Cape. "It has been a long way to get here, a lot of hard work put into it to make sure we have a great integration of this spacecraft with this launch vehicle to make this mission a success tomorrow.

"It is just the start of the journey tomorrow and it has a long way to go. But I just wanted to recognize there is a lot of work that went behind the scenes to get to tomorrow and to get to July Fourth."

The weather outlook for Wednesday's split-second launch opportunity is promising.

"Despite the fact I think I saw a couple of umbrellas out in the audience, I do like our chances for having favorable weather for tomorrow's launch," launch weather officer Joel Tumbiolo told reporters at today's pre-launch news conference.

"Basically ever since the Christmas holiday, we've been under a very good weather pattern. High pressure has been dominating Florida, we've had above normal temperatures, sunny skies and very little rain. We're starting to get into a little bit more of a transition right now when we are getting into a Florida wintertime pattern.

"What I mean by that is we haven't had a cold front in the area in a couple of weeks. We are tracking a cold front right now, which is over the central part of the U.S. and it is slowly migrating to the east. As that happens, the high pressure that has been over Florida is being also pushed to the east. When that does happen, winds from the high pressure come off the ocean and create a few showers along the coast. That is what we had today. And we'll also be monitoring that over the next couple of days.

"Again, it's just the winds coming off the ocean produces some isolated showers and clouds along the coastline. That is basically the weather conditions we're expecting over the next couple of days. That cold front I mentioned is not expected to come through the state until Friday. Over the weekend our weather pattern is really going to shift from what we've been used to the last couple of weeks. But again that will not be till Friday/Saturday time frame."

The forecast for the Deep Impact liftoff time at 1:47:08 p.m. EST (1847:08 GMT) Wednesday calls for some low and high level clouds, breezy winds and a temperature in the mid- to high-70s F.

"Since we have an instantaneous window, chances are good we won't have a shower right over the launch pad at that second in time. Yes, we do need luck in this business!" Tumbiolo said.

"There is greater than 90 percent chance that we will have good weather tomorrow. So only less than 10 percent chance of one of these showers, like we had this morning, moving right over the launch pad right at the 1:47 p.m. time tomorrow."

1930 GMT (2:30 p.m. EST)

All systems are "go" for tomorrow's launch of Deep Impact aboard the Boeing Delta 2 rocket. There are no technical problems being addressed and the weather forecast is favorable.

Check back later this evening for a countdown preview. And watch this page for live play-by-play coverage beginning with mobile service tower rollback at pad 17B, which is expected shortly after 5 a.m. EST (1000 GMT).

1515 GMT (10:15 a.m. EST)

Weather forecasters have improved the odds of acceptable conditions for tomorrow's launch. The outlook had called for a 90 percent chance of meeting the launch weather rules. The forecast issued this morning shows a greater than 90 percent chance. See the full forecast here.

2000 GMT (3:00 p.m. EST)

The Delta 2 rocket's second stage is being filled with its supply of storable hypergolic fuels at launch pad 17B today. The stage uses a hydrazine propellant mixture and nitrogen tetroxide oxidizer to feed its main engine during two firings scheduled in the Deep Impact launch.

The first stage will be fueled during the final three hours of the countdown Wednesday. The third stage and strap-on boosters are loaded with a rubbery solid fuel.

Meanwhile, officials and engineers successfully conducted the Mission Dress Rehearsal today to practice launch day scripts and procedures.

The Launch Readiness Review will be held at the Cape Tuesday morning for senior management to discuss the progress of pre-flight work, any technical issues and the status of the rocket, payload and ground support systems. The meeting concludes with officials giving the formal approval to proceed with Wednesday's launch, assuming there are no outstanding problems.

Wednesday offers a split second in time for Deep Impact to blast off for its 268-million-mile trek to Comet Tempel 1. Launch is possible at 1:47:08 p.m. EST (1847:08 GMT). If the Delta 2 rocket doesn't lift off then, the launch must be postponed for 24 hours.

There will be two instantaneous launch opportunities on Thursday, separated by 40 minutes to give the launch team time to load updated guidance parameters into the Delta rocket. NASA says those times will be 12:59:32 and 1:39:11 p.m. EST (1759:32 and 18:39:11 GMT).

Wednesday originally had two launch shots but officials decided to skip the first attempt due to rocket performance reasons.

1530 GMT (10:30 a.m. EST)

The latest weather forecast continues to predict excellent conditions for Wednesday's planned launch of Deep Impact from Cape Canaveral, Florida. See the full forecast here.


The Air Force weather team is predicting favorable conditions for Wednesday's blastoff of the Boeing Delta 2 rocket carrying NASA's Deep Impact comet probe. See the full forecast here.


As ancient wanderers of the solar system laden with primordial material frozen in time, comets offer humanity clues to some of the most fundamental questions about conditions when the planets were forming more than four billion years ago. NASA will launch a space mission next week to blast a hole in the side of a comet and learn more about the make up of these icy bodies.

Read our mission preview story.


The Deep Impact spacecraft was transported to launch pad 17B and mounted atop the Delta 2 rocket this morning. Liftoff remains scheduled for January 12.


A manufacturing error discovered in a part of the Boeing Delta 2 rocket to launch NASA's Deep Impact comet striker will force on-pad repairs, further delaying liftoff that must occur during an unflexible one-month window. Read our full story.


Launch of NASA's Deep Impact spacecraft that will blast a small projectile into the heart of Comet Tempel 1 has been delayed from December 30 to give engineers more time to complete pre-flight work on mission software, the space agency announced Wednesday. Read our full story.


The Delta launch team at Cape Canaveral had little time to rest after Saturday's successful liftoff of NASA's Swift observatory as the crew begin erecting another rocket Monday that will dispatch an extraordinary mission to Comet Tempel 1 on December 30. Read our full story.


NASA's Deep Impact spacecraft has arrived in Florida to begin final preparations for a launch on December 30. The probe will fire a copper projectile into the surface of comet Tempel 1 next year to create a crater that could be as large as a football field. Read our full story.