BY JUSTIN RAY

Follow the countdown and launch of the Lockheed Martin Atlas 5 rocket with NASA's New Horizons spacecraft bound for Pluto and beyond. Reload this page for the latest on the mission.

1554 GMT (10:54 a.m. EST)

All console operators in the Atlas Spaceflight Operations Center reported a "ready" status during the pre-fueling poll just completed by the launch conductor. Launch director Jerry Jamison gave his 'go' as well.

1552 GMT (10:52 a.m. EST)

The Lockheed Martin launch conductor Ed Christiansen is briefing his Atlas launch team on countdown procedures before entering into the final two hours.

1550 GMT (10:50 a.m. EST)

NASA Launch Manager Omar Baez has completed a poll of the space agency management team. "NASA team is ready for cryo tanking," Baez said at the end. There are no concerns with the Atlas 5 or New Horizons. Weather is 'go' right now. The range is working two issues but neither are constraints to launch.

1536 GMT (10:36 a.m. EST)

Countdown work has been going well this morning. There are no significant problems being addressed at this time and the weather is reported acceptable right now. The next event for the launch team will be a briefing on procedures followed immediately by a readiness poll for fueling operations. That'll be coming up in about 15 minutes.

1528 GMT (10:28 a.m. EST)

T-minus 2 hours and holding. A planned 30-minute built-in hold for the countdown has just started. This scheduled pause is designed to provide some margin in the countdown timeline to deal with technical issues or recover from work running behind. The count will resume at 10:58 a.m. Another hold is planned at the T-minus 4 minute point. Launch is still set for 1:08 p.m. EST.

1523 GMT (10:23 a.m. EST)

A pre-fueling weather briefing has just been conducted. Forecasters are still predicting an 80 percent chance of acceptable conditions today. Clouds are the chief concern. The launch time outlook calls for scattered to broken clouds at 3,500 and 25,000 feet, 7 miles of visibility, winds from the east at 14 gusting to 20, a temperature of 64 to 66 degrees F and relative humidity of 70 percent. The cloud ceiling cannot be below 6,000 feet.

Should the launch be delayed 24 hours for some reason, a similar forecast was given for Friday. There is a 70 percent chance of meeting the launch weather rules tomorrow.

1518 GMT (10:18 a.m. EST)

The final members of the launch pad crew are preparing to leave Complex 41 now.

1514 GMT (10:14 a.m. EST)

Range Safety is performing its hold-fire checks. This ensures safety officers will have the capability of halting the countdown if a problem occurs.

1508 GMT (10:08 a.m. EST)

Launch of New Horizons is now three hours away.

1500 GMT (10:00 a.m. EST)

We have posted a new gallery featuring beautiful photographs of the Atlas 5 rocket's rollout to the launch pad earlier this week, plus predawn, sunrise and daytime pictures of the 20-story vehicle standing atop Complex 41 for launch of the New Horizons spacecraft. See all of the pictures here.

1410 GMT (9:10 a.m. EST)

Early preparations for fueling the Atlas 5 rocket, along with guidance system and range tracking tests have been underway this morning. The countdown is continuing as planned. Skies are mostly overcast as clouds roll inland from the Atlantic, covering the Cape.

1220 GMT (7:20 a.m. EST)

It is not exactly like the movie Groundhog Day depicted when the same day kept repeating. No two launch attempts are completely identical. But for the third consecutive morning the Lockheed Martin Atlas launch team is stepping through procedures to ready its largest rocket ever. Liftoff carrying NASA's New Horizons spacecraft remains targeted for 1:08 p.m. EST today.

WEDNESDAY, JANUARY 18, 2006

New Horizons will make try number 3 at launch on Thursday.

Today's launch opportunity was passed up because of the Pluto-bound spacecraft's mission operations control center in Maryland lost electrical power in a storm. Managers did not want to go forward with the launch while relying solely on backup generator power.

Power has since been restored to the Johns Hopkins University Applied Physics Laboratory campus where the control center is located. The center has both primary and backup power, NASA said late today, and is ready to support launch.

2254 GMT (5:54 p.m. EST)

Launch of New Horizons has been rescheduled for Thursday at 1:08 p.m. EST (1808 GMT). Officials held a meeting late this afternoon that gave approval to proceed with another countdown in the morning.

2030 GMT (3:30 p.m. EST)

Already running a day behind because of high winds in Florida, NASA's New Horizons Pluto mission was grounded today by storms in Maryland that knocked out power to the spacecraft control center at the Johns Hopkins University Applied Physics Laboratory near Washington. Read our full story.

1648 GMT (11:48 a.m. EST)

The weather forecast for Thursday's launch attempt calls for an 80 percent chance of acceptable conditions. You can read the full forecast here.

1630 GMT (11:30 a.m. EST)

The New Horizons team says the power outage at the mission control center was indeed weather related.

"Severe storms in the Baltimore-Washington area had knocked out power in several locations, including the campus of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., where the Horizons spacecraft will be operated in flight," a post-scrub statement says.

"With primary power out the New Horizons mission operations center was on backup power, but New Horizons mission managers wanted to have sufficient backup to those systems in place before conducting critical launch and early flight operations."

The decision will be made later today whether launch can be attempted tomorrow.

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

A management meeting is planned for 4 p.m. EST this afternoon to determine if the New Horizons control center in Maryland will be ready for a launch attempt tomorrow or whether more time is needed. The Atlas launch team is moving forward with a 24-hour scrub turnaround timeline to preserve the option of flying tomorrow.

1459 GMT (9:59 a.m. EST)

SCRUB! Today's launch attempt has been called off. The New Horizons mission control center at the Johns Hopkins University Applied Physics Laboratory suffered a power outage this morning. The backup system using generators is not sufficient to proceed with the launch. So the first mission to Pluto will remain on Earth for another day.

Tomorrow's launch window extends from 1:08 to 3:07 p.m. EST.

1442 GMT (9:42 a.m. EST)

All of the launch weather rules are "go" at this time. Meanwhile, the roadblocks for the blast danger area surround Complex 41 are being put up now. And preparations to ready the launch pad's water deluge system are underway by ground crews.

1416 GMT (9:16 a.m. EST)

The countdown for launch of New Horizons is now entering the final four hours for liftoff at 1:16 p.m. EST this afternoon from Cape Canaveral aboard a Lockheed Martin Atlas 5 rocket. A cold front is sliding through Central Florida, bringing overcast skies, rain and cool temperatures. Gusty winds continue, though they have shifted from the southerly direction experienced yesterday to a northerly direction today.

Despite the wind shift, the limit for launch time remains at 33 knots. The other issue meteorologists will be watching is the cloud ceiling, which cannot be below 6,000 feet.

Looking to the west and north right now, the skies are clearing. And the rain has stopped at the space center.

1155 GMT (6:55 a.m. EST)

Countdown no. 2 has started for New Horizons' launch aboard the Atlas 5. After being secured following yesterday's scrub, the rocket was powered up again about an hour ago. Then the guidance test began. Flight control preps are underway now.

TUESDAY, JANUARY 17, 2006

The weather forecast for Wednesday's launch attempt calls for a 70 percent chance of acceptable conditions. You can read the full forecast here.

2100 GMT (4:00 p.m. EST)

Draining of the cryogenic propellants from the Atlas 5 rocket is underway as part of normal post-scrub activities.

2024 GMT (3:24 p.m. EST)

The constraint that violated a red line limit was indeed the ground winds. There was a gust that broke the 33-knot limit as the countdown was proceeding to a last-ditch attempt for launch at the very close of today's available window.

2023 GMT (3:23 p.m. EST)

Tomorrow's launch window extends from 1:16 to 3:15 p.m. EST.

2022 GMT (3:22 p.m. EST)

The rocket is being safed following the unplanned hold.

2020 GMT (3:20 p.m. EST)

SCRUB. The countdown has been halted at T-minus 2 minutes, 34 seconds due to a red limit monitor fault. This scrubs today's launch attempt of the New Horizons spacecraft since the window is closing at 3:23 p.m. There isn't enough time to recycle the clock, fix the issue and try again.

2020 GMT (3:20 p.m. EST)

HOLD!

2019 GMT (3:19 p.m. EST)

T-minus 3 minutes, 5 seconds. New Horizons has been declared "go" for launch

2019 GMT (3:19 p.m. EST)

T-minus 3 minutes, 45 seconds. Ground pyrotechnics have been enabled.

2019 GMT (3:19 p.m. EST)

T-minus 4 minutes and counting. The final phase of today's countdown has begun for the launch of Lockheed Martin Atlas 5 and the New Horizons spacecraft bound for Pluto!

2018 GMT (3:18 p.m. EST)

Now five minutes form launch.

2017 GMT (3:17 p.m. EST)

Count will resume in two minutes. An abort will be called if winds go out of limits. Launch is set for 3:23 p.m. EST.

2016 GMT (3:16 p.m. EST)

Veteran launch conductor Ed Christiansen, seated in the Atlas Spaceflight Operations Center four miles from the pad, has polled the various console operators to ensure all systems are ready to proceed with the countdown. The 'go' status was passed to launch director Jerry Jamison located above and behind the launch team in the management room.

2014 GMT (3:14 p.m. EST)

A new plan developed is to resume the countdown and call a hold if the winds exceed the 33-knot limit.

2009 GMT (3:09 p.m. EST)

The new timeline calls for the launch team readiness poll at 3:16 p.m., resumption of the countdown at 3:19 p.m. and liftoff at 3:23 p.m. EST (2023 GMT).

2007 GMT (3:07 p.m. EST)

The ground winds at the Complex 41 launch pad are right around the 33-knot limit. Managers have a rule that winds cannot hit that limit within eight minutes of the launch time and still proceed with liftoff at that targeted tme, a NASA spokesman says.

1959 GMT (2:59 p.m. EST)

Just as the upper level winds and a flight profile were determined acceptable for launch, NASA said more time was needed to watch the ground level winds that have been gusting at the 33-knot limit for liftoff of the Atlas 5 rocket.

1957 GMT (2:57 p.m. EST)

NEW LAUNCH TIME! The launch time is being retargeted for the very end of today's window at 3:23 p.m. EST due to the ground level winds.

1956 GMT (2:56 p.m. EST)

Upper level winds have been declared 'go' for launch!

1955 GMT (2:55 p.m. EST)

The new timeline calls for the launch team readiness poll at 2:58 p.m., resumption of the countdown at 3:01 p.m. and liftoff at 3:05 p.m. EST (2005 GMT).

1951 GMT (2:51 p.m. EST)

Lockheed Martin says the upper levels are the only problem. Countdown remains holding at T-minus 4 minutes in hopes of liftoff at 3:05 p.m. EST.

1942 GMT (2:42 p.m. EST)

NEW LAUNCH TIME! Launch has been postponed to 3:05 p.m. EST.

1939 GMT (2:39 p.m. EST)

The Cape launch team has received the latest flight profile for loading into the rocket. Officials are awaiting confirmation that the profile can withstand the current upper level winds.

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

A poll of the New Horizons spacecraft and ground network team was just conducted. The were no problems reported, NASA says.

1927 GMT (2:27 p.m. EST)

The latest flight profile failed against the current upper level wind conditions, Lockheed Martin says. The team is re-working the profile based on the next weather balloon data set.

Meanwhile, the Antigua tracking station problem has been repaired, the Air Force reports. There are no Range constraints at this time.

And a NASA spokesman says the Deep Space Network is ready to support now.

1924 GMT (2:24 p.m. EST)

NEW LAUNCH TIME. Clocks are being reset for liftoff at 2:50 p.m. EST. Today's available launch window extends to 3:23 p.m. EST.

1923 GMT (2:23 p.m. EST)

NASA says its Deep Space Network could not support the target launch time.

1922 GMT (2:22 p.m. EST)

FURTHER DELAY. Liftoff will not occur at 2:30 p.m. EST, the launch team has just been told. A new liftoff time has not been set.

1920 GMT (2:20 p.m. EST)

Ten minutes from the current target launch time. However, Antigua has not been reported back in operation yet.

1915 GMT (2:15 p.m. EST)

The Antigua problem involves a command transmitter at the downrange tracking site.

1914 GMT (2:14 p.m. EST)

The launch team is preparing to upload the new flight profile to the rocket's guidance computer based on the latest weather balloon information.

1907 GMT (2:07 p.m. EST)

The Atlas team is getting data from the latest weather balloon. The wind information is sent to Lockheed Martin's facilities in Denver for analysis and creation of a new flight profile.

1905 GMT (2:05 p.m. EST)

A problem is now being reported with the Antigua downrange tracking station. That site must be operating for range safety and tracking for the Atlas 5 rocket to be cleared for launch. The Range expects the station to be ready again around 2:20 p.m.

1900 GMT (2:00 p.m. EST)

The upper level winds remain "no go" at this time. The latest flight profile did not find acceptable conditions. Also of concern, the pad winds remain right at the constraint red line limit.

There are no other technical problems being addressed. Countdown clocks continue to hold at T-minus 4 minutes, targeting a possible liftoff time of 2:30 p.m. EST.

1855 GMT (1:55 p.m. EST)

NEW LAUNCH TIME. Liftoff has been pushed back to 2:30 p.m. EST.

1852 GMT (1:52 p.m. EST)

A Lockheed Martin spokesman says the upper level wind issue is actually at an altitude of 800 feet. Attempts to develop a flight profile to withstand the current wind conditions failed the past two tries, he said.

1842 GMT (1:42 p.m. EST)

While the upper level wind situation is dealt with, launch managers are still keeping a close eye on the gusty ground winds at the pad. Winds have been flirting with the 33-knot limit for the past couple of hours, and sometimes going above the constraint.

1842 GMT (1:42 p.m. EST)

A new flight profile load is being created from the upper level wind speed and direction information gathered by weather balloons sent up from the Cape through the countdown.

1838 GMT (1:38 p.m. EST)

NEW LAUNCH TIME! Liftoff has been postponed again. The new target is 2:10 p.m. EST. The further delay allows the team to assess the high-altitude winds and generate a flight profile based on those conditions.

1835 GMT (1:35 p.m. EST)

NASA launch manager Omar Baez has polled the agency oversight team. There are no problems being reported with the Atlas 5, New Horizons spacecraft or Range.

1834 GMT (1:34 p.m. EST)

The engineering team and the NASA advisory board have been polled for launch readiness. Everyone is "go" for launch pending acceptable winds. The fill and drain valve concern has been resolved. Weather is the only worry at this time.

1830 GMT (1:30 p.m. EST)

Now 15 minutes from the new launch time.

1824 GMT (1:24 p.m. EST)

A new flight profile based on the upper level winds needs to be performed for the delayed launch time. Ground winds are still a concern, and the first stage liquid oxygen fill and drain valve problem has not been put to rest yet.

1818 GMT (1:18 p.m. EST)

The Eastern Range has confirmed the new launch time of 1:45 p.m.

1815 GMT (1:15 p.m. EST)

The new timeline calls for the launch team readiness poll at 1:38 p.m., resumption of the countdown at 1:41 p.m. and liftoff at 1:45 p.m. EST (1845 GMT).

1813 GMT (1:13 p.m. EST)

NEW LAUNCH TIME! Liftoff has been delayed to 1:45 p.m. EST due to gusty ground winds. Also, the valve issue needs to be wrapped up.

1812 GMT (1:12 p.m. EST)

Engineers have determined the first stage liquid oxygen fill and drain valve issue is not a constraint. The issue is understood.

1810 GMT (1:10 p.m. EST)

The third stage safe and arm device being switched to the enable position.

1810 GMT (1:10 p.m. EST)

T-minus 4 minutes and holding. The countdown has entered this final hold, which planned to last 10 minutes. Launch is still targeted for 1:24 p.m. EST, pending resolution of the valve issue and acceptable weather.

1809 GMT (1:09 p.m. EST)

All three cryogenic fuel tanks aboard the rocket are now reported at flight level.

1808 GMT (1:08 p.m. EST)

The RD-180 main engine fuel-fill sequence is now complete.

1808 GMT (1:08 p.m. EST)

T-minus 6 minutes. Standing by to go into the built-in hold.

1805 GMT (1:05 p.m. EST)

A cycle test of the first stage liquid oxygen fill and drain valve test is going to be re-performed. An earlier test indicated a possible problem.

1804 GMT (1:04 p.m. EST)

Twenty minutes to go.

1803 GMT (1:03 p.m. EST)

The latest guidance and steering data have been loaded into the rocket's flight computer based on today's upper level wind conditions.

1800 GMT (1:00 p.m. EST)

Mission managers continue to monitor the winds at the launch pad, which have been gusting upwards and sometimes greater than the 33-knot limit allowed at liftoff time. Also, a possible problem with the first stage liquid oxygen fill and drain valve is under discussion.

1758 GMT (12:58 p.m. EST)

The fuel-fill sequence for the first stage main engine is commencing.

1754 GMT (12:54 p.m. EST)

Now 30 minutes from launch. Flight control final preps and the flight termination system testing have been reported complete.

1752 GMT (12:52 p.m. EST)

The Centaur liquid oxygen and liquid hydrogen tanks have been reported at flight level.

1751 GMT (12:51 p.m. EST)

The rocket's "pogo" suppressor has been charged for launch. This energy absorption device aboard the rocket is used to damp out oscillations during flight.

1750 GMT (12:50 p.m. EST)

The launch team is looking at the Atlas first stage liquid oxygen fill and drain valve after some unexpected results from a recent test.

1744 GMT (12:44 p.m. EST)

T-minus 30 minutes and counting. The countdown clocks are heading to the T-minus 4 minute mark where a planned 10-minute hold will occur. Launch remains set for 1:24 p.m. EST. Wind is the only worry at this point for an on-time launch.

1734 GMT (12:34 p.m. EST)

Fast-filling of the first stage liquid oxygen tank has been completed. Topping mode is now underway.

1734 GMT (12:34 p.m. EST)

Final checks of the flight termination system are starting. This system would be used to destroy the rocket if the vehicle experienced a major problem during ascent.

1730 GMT (12:30 p.m. EST)

The liquid hydrogen tank in the Centaur upper stage has just reached 97 percent full. Topping is now beginning.

1725 GMT (12:25 p.m. EST)

The first stage liquid oxygen tank is 80 percent full, Centaur liquid hydrogen tank is reached the 60 percent mark and the Centaur oxygen tank is already fully loaded.

1724 GMT (12:24 p.m. EST)

Launch is now just 60 minutes away.

1720 GMT (12:20 p.m. EST)

The first stage liquid oxygen tank is now 70 percent full.

1719 GMT (12:19 p.m. EST)

The Centaur liquid hydrogen tank has reached the 20 percent level. The cryogenic propellant will be consumed with liquid oxygen by the stage's Pratt & Whitney-made RL10 engine.

1719 GMT (12:19 p.m. EST)

The flight control final preparations are starting.

1715 GMT (12:15 p.m. EST)

Winds at Complex 41 are steady at about 25 knots. Gusts have been reaching 35 knots. The launch time limit is 33 knots.

1714 GMT (12:14 p.m. EST)

The Centaur engine chilldown is being initiated.

1712 GMT (12:12 p.m. EST)

Chilldown of the liquid hydrogen system is now complete, allowing the super-cold fuel to begin filling the Centaur upper stage.

1711 GMT (12:11 p.m. EST)

First stage liquid oxygen tank is now half full. Chilled to Minus-298 degrees F, the liquid oxygen will be used with RP-1 kerosene by the RD-180 main engine on the first stage during the initial four-and-a-half minutes of flight today.

1702 GMT (12:02 p.m. EST)

The Centaur liquid oyxgen tank has reached flight level.

1702 GMT (12:02 p.m. EST)

The first stage liquid oxygen tank is 30 percent full.

1659 GMT (11:59 a.m. EST)

The first stage's bronze skin is icing over as the super-cold liquid oxygen continues to flow into the vehicle.

1655 GMT (11:55 a.m. EST)

The Centaur liquid oxygen tank has now reached the 95 percent level. The topping off process is starting. Also, ten percent of the first stage liquid oxygen tank has been filled so far in that portion of fueling this morning.

1653 GMT (11:53 a.m. EST)

The Atlas first stage liquid oxygen loading is transitioning from the slow-fill to the fast-fill mode.

1650 GMT (11:50 a.m. EST)

The chilldown conditioning of liquid hydrogen propellant lines at Complex 41 is now starting to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket. The Centaur holds about 13,000 gallons of the cryogenic propellant.

1649 GMT (11:49 a.m. EST)

The Centaur liquid oxygen tank is now 70 percent full.

1643 GMT (11:43 a.m. EST)

The chilldown conditioning of the systems for the first stage liquid oxygen tank have been completed. And a "go" has been given to begin pumping super-cold liquid oxygen into the Atlas 5's first stage. The Atlas liquid oxygen tank is the largest tank to be filled today. It holds about 50,000 gallons of cryogenic oxidizer for the RD-180 main engine.

1641 GMT (11:41 a.m. EST)

About 40 percent of the Centaur liquid oxygen tank has been filled so far.

1634 GMT (11:34 a.m. EST)

The Centaur liquid oxygen tank is now 10 percent full.

1628 GMT (11:28 a.m. EST)

Following the thermal conditioning of the transfer pipes, filling of the Centaur upper stage with 4,300 gallons of liquid oxygen has begun at Cape Canaveral's Complex 41.

The liquid oxygen -- chilled to Minus-298 degrees F -- will be consumed during the launch by the Centaur's single RL10 engine along with liquid hydrogen to be pumped into the stage a little later in the countdown. The high-energy Centaur will perform two firings today to propel the New Horizons spacecraft out of Earth orbit.

1624 GMT (11:24 a.m. EST)

Liftoff is now two hours away. Pressure checks of the Atlas 5 rocket's first stage fuel tank have been completed. That tank was loaded with about 25,000 gallons of kerosene propellant yesterday afternoon.

1621 GMT (11:21 a.m. EST)

The Centaur liquid oxygen pad storage area has been prepped. The next step is conditioning the transfer lines, which is now beginning to prepare the plumbing for flowing the cryogenic oxidizer.

1614 GMT (11:14 a.m. EST)

Chilldown thermal conditioning of the mobile launch platform upon which the rocket stands is beginning. This is meant to ease the shock on equipment when supercold cryogenic propellants start flowing into the rocket a short time from now.

1614 GMT (11:14 a.m. EST)

T-minus 120 minutes and counting! Today's countdown is marching forward for launch of the Atlas 5 rocket and New Horizons headed for Pluto. Clocks have one more built-in hold planned at T-minus 4 minutes. That pause will last 10 minutes, giving the launch team one last chance to catch up on work running late or deal with any problems.

1612 GMT (11:12 a.m. EST)

Countdown clocks will resume in two minutes.

1610 GMT (11:10 a.m. EST)

All console operators in the Atlas Spaceflight Operations Center reported a "ready" status during the pre-fueling poll just completed by the launch conductor. Launch director Jerry Jamison gave his "go" as well.

1607 GMT (11:07 a.m. EST)

The Lockheed Martin launch conductor Ed Christiansen is briefing his Atlas launch team on countdown procedures before clocks enter into the hectic final two hours.

1607 GMT (11:07 a.m. EST)

NASA Launch Manager Omar Baez has completed a poll of the space agency management team. "NASA team is ready for cryo tanking," Baez concluded.

Winds at the pad have gusted up to 29 knots. The limit is 33 knots at launch time.

1602 GMT (11:02 a.m. EST)

Coming up in about five minutes, the launch team will receive their pre-flight briefing. That will be followed by a readiness poll to verify all systems are ready to begin fueling the vehicle with cryogenic propellants.

The countdown has been going well this morning. No technical problems are being worked and the weather looks great.

1554 GMT (10:54 a.m. EST)

Now 10 minutes into this scheduled hold point. The blast danger area is now verified clear of all personnel.

1544 GMT (10:44 a.m. EST)

T-minus 120 minutes and holding. Countdown clocks have just gone into the planned half-hour built-in hold. Launch of the Atlas 5 rocket remains on target for 1:24 p.m. EST today.

1540 GMT (10:40 a.m. EST)

Range Safety has completed the hold-fire checks. This ensures safety officers will have the capability of halting the countdown if a problem occurs.

1537 GMT (10:37 a.m. EST)

The launch pad area is being cleared of all remaining workers. The hazardous operation of fueling the rocket will be getting underway within the hour.

1524 GMT (10:24 a.m. EST)

New Horizons is now just three hours from liftoff time.

1500 GMT (10:00 a.m. EST)

Atlas propulsion and hydraulic preps are now reported complete.

1453 GMT (9:53 a.m. EST)

A C-band test with the Range has been completed. This system allows the Air Force-controlled Eastern Range to track the Atlas 5 rocket during launch.

1450 GMT (9:50 a.m. EST)

Roadblocks around the blast danger area of the launch pad are being established.

1445 GMT (9:45 a.m. EST)

NASA is not reporting any technical issues as the countdown continues.

1354 GMT (8:54 a.m. EST)

Launch is now about four-and-a-half hours away. It is a beautiful morning along Florida's east-central coast. At Complex 41, the flight control operational test has been completed and final preps are underway on the liquid oxygen and liquid hydrogen systems.

1150 GMT (6:50 a.m. EST)

Launch day has arrived for New Horizons to embark on its trek across the solar system. The Atlas 5 rocket was powered up about 90 minutes ago. The flight control final preps now are beginning and countdown clocks tick toward the planned 1:24 p.m. EST (1824 GMT) liftoff this afternoon.

MONDAY, JANUARY 16, 2006

A Lockheed Martin Atlas 5 rocket carrying NASA's New Horizons spacecraft was hauled to the launch pad today for final preparations before blastoff Tuesday on a nine-year voyage to icy Pluto, gateway to the unexplored hinterlands of the solar system. Read our full story.

Additional coverage for subscribers:
VIDEO: ATLAS 5 ROCKET ROLLS TO PAD WITH NEW HORIZONS PLAY
VIDEO: TIME-LAPSE VIDEO OF THE ROLLOUT PLAY
SUBSCRIBE NOW

2125 GMT (4:25 p.m. EST)

The initial portion of Atlas 5 rocket fueling operations is nearing completion for tomorrow's launch of the New Horizons spacecraft. Lockheed Martin technicians are close to finishing the pumping of about 25,000 gallons of kerosene fuel into the rocket's first stage. That propellant will be consumed with liquid oxygen to power the vehicle's Russian-designed RD-180 main engine during the first four-and-a-half minutes of launch.

The first stage liquid oxygen supply, along with the super-cold liquid oxygen and liquid hydrogen for the Centaur upper stage, will be loaded into the rocket during the final two hours of tomorrow's countdown.

The launch team will be wrapping up today's planned activities and securing the rocket for the evening. Countdown work resumes before dawn tomorrow when the Atlas 5 is powered up at about 5:24 a.m. EST. Routine pre-flight tests of vehicle systems and preparations for cryogenic fueling are among the chores during the morning.

At 10:44 a.m., the count will enter a planned 30-minute built-in hold at the T-minus 120 minute mark. This pause gives the launch team the opportunity to catch up on any work running behind the timeline or deal with technical glitches. A poll of team members occurs five minutes before the end of the hold to verify everyone is ready for liquid oxygen and liquid hydrogen fueling.

Chilling of propellant lines and tanks is performed to thermally condition the equipment in preparation for flowing the super-cold fuels. Centaur liquid oxygen loading should begin at about 11:31 a.m., followed by Atlas first stage liquid oxygen and finally Centaur hydrogen fueling.

A final hold is planned at T-minus 4 minutes. This will be a 10-minute hold starting at 1:10 p.m. EST to conduct readiness polls of senior management, the launch team members, Range and weather. If all elements are deemed "go" for launch, the clock will resume ticking at 1:20 p.m.

The launch window extends from 1:24 to 3:23 p.m. EST.

Watch this page for play-by-play reports on the countdown throughout the day!

2115 GMT (4:15 p.m. EST)

Some additional rollout pictures have been posted here.

2014 GMT (3:14 p.m. EST)

The first stage fuel tank is now about half full. The highly refined kerosene propellant, called RP-1, is being pumped from a launch pad storage tank into the base of the Atlas 5 rocket.

1943 GMT (2:43 p.m. EST)

The "go" has been given to the launch team for fueling the Atlas rocket's first stage.

1900 GMT (2:00 p.m. EST)

We have posted a collection of photos taken during this morning's rollout of the Atlas 5 rocket. Check out the gallery here.

1855 GMT (1:55 p.m. EST)

The Atlas first stage and Centaur upper stage are being powered up as post-rollout operations continue at Complex 41 under brilliant blue skies.

1830 GMT (1:30 p.m. EST)

Weather forecasters are still predicting an 80 percent chance of favorable conditions for tomorrow's launch. See the latest forecast here.

1818 GMT (1:18 p.m. EST)

The two undercarriages used to move the mobile launch platform to the pad this morning have been disconnected and pulled out from beneath the Atlas 5 rocket. Crews plan to begin pumped kerosene fuel into the first stage this afternoon.

Additional coverage for subscribers:
VIDEO: SUNDAY'S PRE-LAUNCH NEWS BRIEFING DIAL-UP | BROADBAND
VIDEO: ANIMATED ATLAS 5 LAUNCH PREVIEW WITH NARRATION PLAY
VIDEO: NEW HORIZONS SCIENCE BRIEFING DIAL-UP | BROADBAND
VIDEO: SCIENCE INSTRUMENTS BRIEFING-PART 1 DIAL-UP | BROADBAND
VIDEO: SCIENCE INSTRUMENTS BRIEFING-PART 2 DIAL-UP | BROADBAND

VIDEO: NEW HORIZONS MOUNTED ATOP THE ATLAS 5 PLAY
VIDEO: SPACECRAFT TRAVELS TO ROCKET ASSEMBLY BUILDING PLAY
VIDEO: MISSION LOGO APPLIED TO THE ATLAS 5'S FAIRING PLAY
VIDEO: SPACECRAFT ENCAPSULED WITHIN ROCKET NOSE CONE PLAY
VIDEO: PLUTO NEW HORIZONS MOUNTED ATOP THIRD STAGE PLAY
VIDEO: BOEING DELIVERS THIRD STAGE DESPITE STRIKE PLAY
VIDEO: FINAL SRB ATTACHED TO THE ATLAS 5 ROCKET PLAY
VIDEO: SPACECRAFT UNDERGOES SPIN BALANCE TESTING PLAY
SUBSCRIBE NOW

1610 GMT (11:10 a.m. EST)

ON THE PAD! The Atlas 5 rocket has arrived at the Complex 41 launch pad for tomorrow's liftoff carrying the New Horizons spacecraft destined for Pluto and the outer solar system.

The two mobile trailers connected to the launching platform, which were part of the convoy during today's rollout, soon will be hooked up to power and communications systems at the pad. These trailers provide conditioned air to the payload and communications with the rocket during the roll and throughout the countdown. They are protected from the blast of launch by a concrete structure on the north-side of the platform.

Liftoff remains scheduled for 1:24 p.m. EST (1824 GMT) at the opening of a one-hour, 59-minute launch window.

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

ROLLOUT BEGINS! New Horizons is moving ever closer to departing Earth on a 3 billion mile voyage to Pluto.

The spacecraft, bolted atop the Lockheed Martin Atlas 5 rocket, has begun a slow drive from the 30-story Vertical Integration Facility at Cape Canaveral's Complex 41 to the launch pad. A pair of specially-made "trackmobiles" are pushing the Atlas 5 rocket's 1.4-million pound mobile launching platform along rail tracks for this 1,800-foot trip.

To learn more about the "clean pad" concept used by Lockheed Martin for the Atlas 5 program, see our complete story.

1430 GMT (9:30 a.m. EST)

Activities are on schedule for this morning's rollout of the Atlas 5 rocket, Lockheed Martin reports. It is a sunny but cool morning here in Central Florida. The roll is expected to begin in about an hour.

SUNDAY, JANUARY 15, 2006

A grand adventure to explore the outer frontier of the solar system moves to the launch pad Monday for the final day of preparations leading to blastoff.

NASA's New Horizons spacecraft stands on the verge of launch to perform the initial reconnaissance of distant Pluto, and then travel further into the realm of the Kuiper Belt that is filled with tiny worlds dubbed by scientists as "icy dwarfs."

"One of the most compelling reasons of why Americans are going to Pluto is to discover what we don't know," said Colleen Hartman, deputy associate administrator for NASA's Science Mission Directorate. "What we know about Pluto today could fit on the back of a postage stamp... The textbooks will be re-written after this mission is completed."

"This is a very exciting time. We are poised to begin the exploration of a new world," added Dale Cruikshank, New Horizons science team co-investigator from NASA's Ames Research Center.

New Horizons will rendezvous with Pluto on July 14, 2015, passing within 6,200 miles of the planet while the craft's suite of cameras and instruments make detailed observations. Encounters with one or two small Kuiper Belt Objects could occur over the following five years.

The launch readiness review was completed Sunday, giving ground crews authorization to enter into the last phases of New Horizons' pre-flight activities, including Monday morning's rollout of the Lockheed Martin Atlas 5 rocket from its assembly building to the pad at Cape Canaveral's Complex 41.

Liftoff remains targeted for 1:24 p.m. EST (1824 GMT) Tuesday when the day's one-hour, 59-minute launch window swings open. The launch team will have 24 opportunities, separated by five-minute intervals that are needed to reset downrange tracking assets required for the third stage motor firing, to get the Atlas 5 airborne during the window, NASA Launch Manager Omar Baez said.

Weather forecasters are predicting an 80 percent chance of acceptable conditions for launch. Winds blowing in excess of 20 knots will be watched closely. The Atlas 5's wind limit at launch is 33 knots. Thick clouds and coastal rainshowers generated by an approaching cold front are slight concerns as well.

Meteorologists don't expect any weather problems for Monday's transfer of the Atlas 5 rocket to the launch pad. That move begins at 10:30 a.m. EST when the mobile launching platform begins wheeling the vehicle out of the 30-story Vertical Integration Facility. It should take less than an hour for the rocket to travel along 1,800 feet of rail tracks connecting its hangar and the pad.

Monday afternoon will be spent securing the mobile platform to the pad and loading the Atlas 5's first stage with its highly refined kerosene propellant.

Watch this page for live updated on the rollout!

1440 GMT (9:40 a.m. EST)

The latest launch weather forecast is available here.

SATURDAY, JANUARY 14, 2006

Following yesterday's installation of the RTG nuclear power device on New Horizons, today focused on final electrical testing of the spacecraft.

"New Horizons is now operating, as it will in flight, off its flight RTG power supply. In an operational sense, we are now very much in a flight mode. From now until the end of the mission, perhaps as long as 20+ years from now, our spacecraft is powered," Alan Stern, the New Horizons principal investigator, wrote in a mission update today.

"Yesterday the last spacecraft preps, red tag removals, etc., were completed at Launch Complex 41 here at the Kennedy Space Center. And back at the Mission Operations Center (MOC) at the Applied Physics Laboratory, just a few hundred meters from where New Horizons was built, the flight control team completed final countdown rehearsal activities today in conjunction with the Deep Space Network (DSN). The flight control team, under the direction of Mission Ops Manager Alice Bowman, also completed a series of software table loads and load verifications to make sure New Horizons has the right initialization values for its clocks, its guidance system, and other subsystem configuration items."

The launch readiness review remains scheduled for Sunday morning to give the OK to proceed with the final countdown to liftoff.

"So hold on to your hats, sports fans, New Horizons is about to be lofted toward the Kuiper Belt, roughly 3 billion miles from Mother Earth. Paid for by Americans, she is headed to the very frontier -- for science, for exploration, for all mankind," Stern said.

1545 GMT (10:45 a.m. EST)

The updated launch weather forecast issued this morning is available here.

0501 GMT (12:01 a.m. EST)

The first robotic explorer to visit Pluto and probe the Kuiper Belt in our solar system's outer frontier awaits launch from Cape Canaveral at 1:24 p.m. EST on Tuesday. Check out this highly-detailed five-part preview story examining NASA's New Horizons mission here.

FRIDAY, JANUARY 13, 2006

Air Force weather forecasters are predicting a chance of thick clouds and rainshowers around Cape Canaveral on Tuesday courtesy of an approaching cold front. But there is an 80 percent of having acceptable weather for a liftoff attempt during the day's two-hour launch window.

The weather for Monday's rollout of the Atlas 5 rocket from its assembly building to the launch pad looks good.

See the full forecast here.

THURSDAY, JANUARY 12, 2006

The New Horizons spacecraft passed its flight readiness review Thursday, affirming plans to launch the Pluto-bound probe next Tuesday from Cape Canaveral.

Final preps on the satellite are wrapping up at the Atlas 5 rocket's assembly building. Spacecraft electrical tests are scheduled for Saturday, followed by closing the access doors on launcher's nose cone.

The launch readiness review is planned for Sunday. That will give the approval to roll the Atlas 5 to the launch pad Monday morning and enter into the countdown.

Tuesday's weather forecast calls for an 80 percent chance of favorable conditions. The day's launch window extends from 1:24 to 3:23 p.m. EST.

Watch this page for comprehensive live countdown and launch coverage!

SUNDAY, JANUARY 8, 2006

It is astronomers' insatiable quest to examine the conditions billions of years ago when the planet of our solar system were forming that pushes NASA's first robotic mission to Pluto. But political bickering has stonewalled the program for years, postponing an attempt to reconnoiter the frigid worlds never reached by humanity. Read our mission overview.

FRIDAY, JANUARY 6, 2006

Inspections performed on the Atlas rocket's first stage fuel tank this week did not reveal any cracks or defects, NASA announced today. Further analysis is still being conducted before the space agency gives final approval for liftoff.

WEDNESDAY, DECEMBER 21, 2005

Officials have updated the information initially released about to the launch delay. The first stage tank design has not been changed. The pressure testing in question was being done as part of the qualification for the Atlas 5 to fly with five strap-on solid rocket boosters. Earlier launches have used no more than three SRBs. Also, the rocket's first stage propellant tank was drained of its kerosene fuel after the countdown dress rehearsal.

SATURDAY, DECEMBER 17, 2005
1700 GMT (12:00 p.m. EST)

The Pluto New Horizons spacecraft was delivered to the Atlas 5 rocket's assembly building this morning. The NASA probe began the ride to Complex 41 from its processing facility around 1:45 a.m. aboard a special transporter.

The spacecraft had spent the past three months at Kennedy Space Center's Payload Hazardous Servicing Facility undergoing functional testing, final closeouts, filling of its hydrazine fuel, mating with the third stage kick motor and spin-balance checks.

After reaching Lockheed Martin's Vertical Integration Facility following the early morning drive across the Cape, a crane lifted the pointy-package -- consisting of the spacecraft and attached third stage already tucked inside part of the rocket's nose cone -- into the building for mounting atop the awaiting Atlas 5 vehicle.

The payload will be firmly attached to the Centaur upper stage, completing assembly of the launch vehicle. Engineers plan to conduct the Integrated Systems Test between the combined rocket and payload stack on Wednesday to verify good connections.

Things will be quiet during the holidays, a Lockheed Martin spokesperson says. Teams will resume launch preps on January 3. The internal inspections of the first stage fuel tank, which have delayed the launch, are expected to be conducted after the year-end break.

The Atlas 5 is now scheduled for rollout from the Vertical Integration Facility to the launch pad on January 16. Liftoff is planned for 1:24 p.m. EST (1824 GMT) on January 17.

"We are now on the heels of launch," Alan Stern, the New Horizons principal investigator, wrote earlier this week in his monthly mission update. "And like any flight mission, we're dealing with a few final demons. For New Horizons, these include some increased testing of our "autonomy" subsystem ‹ a software package designed to handle fault detection and correction when we're far from Earth, some delays in closing out the thousands of checks, reports and verifications necessary to prove we're ready to be certified for flight, and some concerns about rare but real commands that are "dropped" (or unprocessed) by the spacecraft's Power Distribution Unit (PDU)."

Stern added: "Ahead of us lies another launch countdown practice drill, some remaining testing of the autonomy system under more wide-ranging conditions that the original test plan allowed for, a lot of paperwork to close out, and a series of NASA pre-flight spacecraft and mission assurance reviews to ensure they are ready to authorize us to count down and launch.

"All that said, our little speed demon spacecraft is buttoned up for flight and its launch vehicle is assembled. There isn't much more good we can do for our baby here on Earth. Like a child leaving for college, it's time for the parents to let go and see how she does on her own. Graduation day is coming. And if all goes well, the Pluto encounter will begin just 3,300 days later..."

FRIDAY, DECEMBER 16, 2005
2250 GMT (5:50 p.m. EST)

Launch of the Pluto-bound New Horizons spacecraft is being delayed so engineers can perform precautionary boroscope inspections of the Atlas 5 rocket's first stage fuel tank.

Liftoff had been scheduled for January 11 from Cape Canaveral. But the extra work will slip the launch to no earlier than January 17, eating up the first six days in the year's 35-day window to dispatch the probe from Earth.

The NASA-ordered inspections stem from a problem experienced in September during factory testing of an updated Atlas 5 tank design. Lockheed Martin says a test tank failed just under the "ultimate pressure" threshold it should withstand. That led to workers reinspecting all of the tanks that had been produced in the factory.

The Atlas 5 rocket to launch New Horizons passed its check successfully. But now NASA wants to inspect the propellant tank's interior one more time to be safe.

The tank already contains the flight load of RP-1 fuel to feed the rocket's RD-180 main engine during liftoff. The highly refined kerosene was pumped aboard the vehicle during a countdown dress rehearsal earlier this month. That fuel will have to be drained and the tank purged before the inspections can start.

Launch on January 17 will be possible during a two-hour window opening at 1:24 p.m. EST (1824 GMT). Despite the delay, New Horizons can still achieve the desired trajectory that swings past Jupiter for a sling-shot boost and reaches Pluto in 2015. The window for that scenario runs through January 28.

Liftoff between January 29 and February 2 would still include a Jupiter flyby but the arrival at Pluto would slip to 2016 or 2017 depending on the day of launch. More days are available for launch through February 14, but that would set up a direct route from Earth to Pluto that adds years to the trip because Jupiter will have moved out of alignment.

After mid-February the launch would have to wait a year before the next planetary opportunity lines up.

Meanwhile, the New Horizons craft remains set to travel tonight from its Kennedy Space Center processing facility to the Atlas 5 vehicle assembly building at Complex 41. The spacecraft will be mated atop the rocket on Saturday.

TUESDAY, DECEMBER 6, 2005

Lockheed Martin's Atlas 5 rocket returned to its processing hangar from the launch pad Tuesday, ending a successful three-day countdown dress rehearsal and marking the start of the next phase in this time-sensitive pre-launch campaign for NASA's New Horizons mission to Pluto.

Liftoff remains on schedule for January 11 from Complex 41 at Cape Canaveral, Florida.

The so-called Wet Dress Rehearsal began Sunday when the rocket was rolled from its assembly building to the pad atop a mobile launch platform. Monday featured a complete launch day simulation in which the team ran through procedures and the Atlas 5 was fueled with propellants. The countdown went well and the target launch time was hit during the rehearsal.

With the Atlas 5 now back in the assembly building, crews will be readying the rocket to receive the New Horizons spacecraft on December 16. The probe is undergoing the final days of preps at its checkout building at nearby Kennedy Space Center.

About 170 pounds of hydrazine fuel were pumped into the spacecraft Sunday. The propellant will be used for maneuvering the spacecraft and steering its course during the epic trip to Pluto and the Kuiper Belt.

Balance testing, which is performed by spinning the craft, was underway Tuesday and scheduled to continue on Wednesday.

The Boeing-provided third stage, a modified version of the kick motor flown on Delta 2 rockets, was delivered to the Pluto team last week. New Horizons will be mounted atop the stage on Friday. The two halves of the Atlas 5 nose cone will be slid around the spacecraft next Monday in a process called encapsulation.

The combined spacecraft, third stage and shroud then travel from Kennedy Space Center's Payload Hazardous Servicing Facility to the Atlas 5 assembly building on December 16. A lifting crane will hoist the cargo into position atop the Atlas 5's Centaur stage.

Occurring in the background of the New Horizons launch preparations is a tense labor union strike at Boeing. Five workers that were supposed to be readying the third stage hit the picket lines a month ago, prompting Boeing to replace them with experienced managers and supervisors to ensure the motor was finished on schedule.

New Horizons must launch within an 18-day period opening January 11 to achieve the right trajectory between the planets to receive a gravity-assist sling shot from Jupiter and reach Pluto in 2015. Liftoff between January 29 and February 2 would still include a Jupiter flyby but the arrival at Pluto would slip to 2016 or 2017 depending on the day of launch.

More days are available for launch through February 14, but Jupiter will have moved out of alignment by then, forcing a direct route from Earth to Pluto that would add years to the trip. That's something scientists fear because Pluto's tenuous atmosphere is predicted to soon freeze away as its orbit loops farther from the sun.

"As Pluto moves away from the sun it cools and its atmosphere literally snows, or collapses, onto the surface," Alan Stern, the New Horizons mission principal investigator, said in a recent press briefing. "In fact, in 20 years time we expect there will be no atmosphere left to study. So we are racing against that clock to make sure we can study Pluto's temporary atmosphere."

This week, the union issued a press release calling on NASA to ground New Horizons because of the strike. But the Boeing involvement is largely complete, the space agency says, with only mechanical and electrical connectors between the spacecraft and third stage left to be hooked up on Friday. The spacecraft team's own members running the mission for the Johns Hopkins University Applied Physics Lab will be operating the crane to place New Horizons atop the motor.

Union spokespeople have pointed to the nuclear power source for New Horizons as reason against using replacement workers during the pre-launch campaign. However, the Radioisotope Thermoelectric Generator, or RTG, is not installed until much closer to launch, after the spacecraft is mated atop the Atlas 5 in the Complex 41 assembly building.

Additional coverage for subscribers:
VIDEO: ATLAS 5 FIRST STAGE ERECTED PLAY | Preview
VIDEO: CENTAUR UPPER STAGE ADDED PLAY | Preview
VIDEO: STRAP-ON SOLID ROCKET BOOSTERS PLAY | Preview
VIDEO: THE PROBE'S NUCLEAR POWER SOURCE PLAY | Preview
VIDEO: THE SPACECRAFT ARRIVES AT THE LAUNCH SITE PLAY
VIDEO: PLUTO NEW HORIZONS IN CAPE CLEANROOM PLAY
SUBSCRIBE NOW

MONDAY, DECEMBER 5, 2005

The Lockheed Martin Atlas 5 rocket and its launch team successfully accomplished the countdown dress rehearsal today, hitting the simulated target liftoff time of 1 p.m. EST.

The vehicle will be drained of its fuel this afternoon and placed into a safe configuration. Rollback of the Atlas 5 to the assembly building from the launch pad is scheduled for tomorrow morning.

In other news, the New Horizons spacecraft undergoing its pre-launch campaign in a processing facility at Kennedy Space Center was successfully filled with 170 pounds (77 kg) of hydrazine fuel yesterday. The propellant will be used for maneuvering the spacecraft and steering its course during the epic trip to Pluto and the Kuiper Belt.

Launch of this first robotic expedition to the outer reaches of the solar system remains scheduled for January 11. Liftoff is targeted for around 2:11 p.m. EST, a few minutes into the day's two-hour launch window that runs from 2:07 to 4:07 p.m. EST.

1735 GMT (12:35 p.m. EST)

The countdown continues to head for the mock liftoff time of 1 p.m. EST. The rocket has been fueled up with its cryogenic propellants just like it will be on launch day That has produced the usual coating of ice over the Atlas 5 first stage's bronze exterior and streamers of white vapors billowing from vent ports.

1625 GMT (11:25 a.m. EST)

Fueling of the Atlas 5 rocket with liquid oxygen and liquid hydrogen propellants is underway at Complex 41. The practice countdown, called the Wet Dress Rehearsal, is proceeding as planned today.

The countdown is being orchestrated from the Atlas 5 Spaceflight Operations Center, located about four miles south of the launch pad. The ASOC houses the launch team, mission managers and vehicle engineering specialists. It also serves as the hub for entertaining customers and VIPs on launch day.

SUNDAY, DECEMBER 4, 2005

The Lockheed Martin Atlas 5 rocket that will launch NASA's New Horizons spacecraft to Pluto next month was on the move this morning, traveling from its vehicle assembly building to the pad at Cape Canaveral's Complex 41 for a practice countdown.

A mobile launch platform hauled the rocket, minus the Pluto probe and nose cone, along 1,800 feet of rail tracks to the pad to begin a three-day dress rehearsal. The 35-minute trip began just before 10:30 a.m. EST.

Automatic couplers that route fuel lines and other vital commodities between the ground systems and the rocket's platform were slated to engage shortly after arriving at the pad.

Plans for later this afternoon are focused on fueling the Atlas 5's first stage with its supply of highly refined kerosene propellant. Then the vehicle will be secured for the night.

Monday will be a complete launch day simulation, giving teams the opportunity to rehearse countdown procedures and scripts, plus exercising the rocket and pad hardware. Atlas 5 will be powered up around 6 a.m., followed by tests of the flight control, C-band tracking and S-band telemetry systems. Activities will plot along a real countdown timeline.

The pad should be cleared of all workers shortly after 10 a.m., and clocks will enter a planned half-hour hold at the T-minus 120 minute mark at 10:20 a.m. EST. The launch team will be polled for readiness to begin pumping super cold rocket fuel into the Atlas 5 about five minutes before the count resumes from the built-in hold period.

Filling of the Centaur upper stage with cryogenic liquid oxygen is step one in launch day fueling operations, followed by loading first stage liquid oxygen and then Centaur liquid hydrogen.

Clocks will continue to tick until T-minus 4 minutes when another built-in hold is scheduled. This 10-minute pause starts at 12:46 p.m. Status checks and polls will be performed to ensure everything is ready to enter into the final phase of the countdown.

The pretend target launch time for the dress rehearsal is 1 p.m. EST (1800 GMT).

After the simulation is completed, the Atlas 5 will be safed, the liquid oxygen and liquid hydrogen supplies drained from the vehicle and the pad reopened to workers by late afternoon.

Tuesday morning will be spent getting the mobile launch platform disconnected from the pad and moving the rocket back to the assembly building.

Once the rocket is inside the hangar again, crews will be making final preparations to receive the New Horizons spacecraft later this month for mounting atop Atlas 5.

The fully assembled Atlas 5 ventures out to the pad on January 10, one day before liftoff of the $675 million mission to Pluto.

The Atlas 5 program at the Cape differs from other American rockets that are assembled stage by stage on the launch pad within an enclosed gantry. Lockheed Martin designed its next-generation booster to be put together inside a building and then transferred to the pad within a day of launch.

THURSDAY, DECEMBER 1, 2005

Boeing workers delivered a modified Delta 2 rocket third stage to the New Horizons processing facility at Kennedy Space Center as scheduled today despite a strike by some workers. The solid-fuel motor will give the spacecraft the needed push for its voyage across the solar system.

New Horizons is inside the Payload Hazardous Servicing Facility where final pre-flight testing and preps are wrapping up. Hydrazine fuel for the craft's maneuvering thrusters will be loaded aboard on Sunday. A spin balance test is scheduled for Tuesday and Wednesday. Mating of New Horizons atop the third stage is planned for December 9.

WEDNESDAY, NOVEMBER 30, 2005

Preparations continue for January's launch of the New Horizons spacecraft from the Cape. The replacement solid rocket booster was attached to the Atlas 5 this week, and Lockheed Martin is gearing up for the countdown dress rehearsal that begins Sunday.

The spacecraft is undergoing additional testing of the autonomy software system to confirm that it would take the proper safing actions if a problem occurred aboard the New Horizons during the mission, NASA officials said yesterday.

"The scope of this testing has expanded, requiring additional days for ground processing to ensure a successful mission. As a result, encapsulation is six days behind schedule, but the January 11 launch date has not been disturbed," a mission status report said.

Enclosing New Horizons into the Atlas 5's nose cone is now slated for December 12, followed by transportation to Complex 41 for mating to the rocket on December 16.

WEDNESDAY, NOVEMBER 2, 2005

Lockheed Martin technicians are replacing one of the solid-fuel boosters attached to the Atlas 5 rocket that will launch NASA's New Horizons spacecraft to Pluto because of damage the motor sustained during Hurricane Wilma.

The Atlas 5 is being assembled inside the 30-story Vertical Integration Facility at Cape Canaveral's Complex 41 in advance of the targeted January 11 liftoff that will send the five-ton New Horizons probe on its decade-long cosmic cruise to encounter the unexplored planet Pluto.

Although the center of Wilma remained well south of the Cape, the large storm delivered heavy rain and hurricane-force winds to the Space Coast on October 24 as it sliced across Florida.

A third of the 41-by-275-foot reinforced fabric "MegaDoor" on the assembly building's opening that faces the launch pad tore in the storm, causing some debris to fall inside the facility.

The Atlas 5's bronze first stage and Centaur upper stage were erected atop a mobile launch platform, and the first of five strap-on solid rocket boosters was attached to the first stage when Wilma blew through. Atlas 5 rockets are put together within the VIF, then moved to the pad in the final 12 hours of the countdown.

Post-storm inspections revealed a ding on the solid motor casing, prompting officials to order the booster's removal and replacement. The motor could have been safe to fly, engineers believed, but officials ruled that exchanging it would be quicker than the time required to analyze the damage and re-certify the booster.

Read our full story.