BY JUSTIN RAY

Follow the preparations and launch of the Lockheed Martin Atlas 5 rocket carrying the Hellas Sat communications satellite. Reload this page for the very latest on the mission.

1947 GMT (3:47 p.m. EDT)

T-minus 120 minutes and counting. The countdown has resumed as scheduled following the planned 30-minute hold. There are no significant issues being reported and the weather is beautiful for today's Atlas 5 rocket launch at 5:57 p.m. EDT today. One more planned hold is slated for T-minus 4 minutes.

As the count picks up, the launch team will begin pressurizing the RP-1 first stage fuel tank and liquid oxygen chilldown procedures.

1938 GMT (3:38 p.m. EDT)

Launch Conductor Mike Jacobs has polled his launch team for a readiness to press ahead with cryogenic fueling operations this afternoon. No problems were reported. Launch Director Adrian Laffitte then announced his "ready" status.

1932 GMT (3:32 p.m. EDT)

Now half-way through this 30-minute built-in hold. A "ready report" poll of the launch team to ensure everyone is "go" to start cryogenic tanking is scheduled to occur in five minutes.

1917 GMT (3:17 p.m. EDT)

T-minus 120 minutes and holding. The countdown has entered the scheduled half-hour pause. Clocks are slated to resume at 3:47 p.m. EDT. Efforts to clear the pad of all workers before the hazardous operations of loading the cryogenic fuels into the rocket is nearing completion.

1910 GMT (3:10 p.m. EDT)

Good day from Cape Canaveral where the countdown is continuing for today's launch at 5:57 p.m. EDT. We are positioned just a couple miles away from the Atlas 5 rocket. The skies are clear, there is a comfortable wind blowing on this warm afternoon. Everything is looking good for liftoff in about three hours, Lockheed Martin officials say.

1730 GMT (1:30 p.m. EDT)

Clocks continue to tick down to today's planned 5:57 p.m. EDT (2157 GMT) liftoff time for the Atlas 5 rocket -- tail number AV-002 -- and the Hellas Sat communications spacecraft payload. No problems are being reported by Lockheed Martin as the countdown enters the final four-and-a-half hours. In fact, launch managers say activities are running about 30 minutes ahead of the timeline.

Our next update will be posted on this page at approximately 3 p.m. EDT from Cape Canaveral as we begin our live play-by-play coverage of the countdown and launch.

1515 GMT (11:15 a.m. EDT)

Launch Weather Officer Jim Sardonia remains optimistic that conditions will be acceptable for liftoff of the Atlas 5 rocket later today. He has issued his launch day weather forecast, which you can see here.

1440 GMT (10:40 a.m. EDT)

The mobile launching platform has been lowered and secured on the mounts at the pad. With the platform "harddown" at Complex 41, the two "trackmobiles" that were used to transport the MLP from the Vertical Integration Facility to the pad have been unhooked and driven away as pre-launch preparations continue in today's countdown.

Also disengaged from the platform were the two Environmental Control System trailers, which were needed during the rollout. But with the control system switched to pad equipment, the trailers are no longer required.

Two other trailers that were part of the rollout convoy will remain connected to the platform throughout the launch operation. The PVAN and GVAN -- the payload and rocket ground system vans -- on the leading side of the platform were rolled straight into Pad Equipment Building on the north side of the rocket today. The Pad Equipment Building will be sealed, protecting the vans from the blast of launch.

1255 GMT (8:55 a.m. EDT)

An engineering meeting was held this morning to formally review the replacement of a faulty component on the rocket and verify readiness for today's countdown.

Following its trouble during yesterday's countdown that forced officials to scrub the first launch attempt, the Remote Data Unit on the Centaur upper stage was removed and replaced in the Vertical Integration Facility last night.

Since the unit is considered an instrumentation-only system during the countdown and not a flight-critical avonics box, the swapout was a relatively minor task, Lockheed Martin said.

1241 GMT (8:41 a.m. EDT)

The Lockheed Martin Atlas 5 rocket with the Greek Hellas Sat communications satellite nestled inside its nose cone has returned to the launch pad for another countdown.

After a technical glitch interrupted yesterday's countdown, the rocket was rolled back to its assembly building for repairs. Last night, officials cleared the way for a second launch attempt to be made today.

Today's launch window extends from 5:57 to 6:31 p.m. EDT (2157-2231 GMT).

Here is a look at the activities that will be occurring over the next few hours:

The two mobile trailers connected to the launching platform, which were part of the convoy during this morning'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.

Within the next hour, the auto couplers between the pad and platform will be engaged to route umbilical connections from the ground to the rocket.

At around 11 a.m. EDT (1500 GMT), the Atlas first stage and Centaur upper stage are scheduled to be powered up. During the next hour, testing of the rocket's guidance system will start, followed by flight control system preps and a closed-loop check of the flight termination safety system.

At about 12:20 p.m. EDT (1620 GMT), efforts to clear the Vertical Integration Facility area of personnel begins.

A variety of other standard countdown operations will continue into the early afternoon hours.

A weather briefing is planned at 3:12 p.m. EDT (1920 GMT), just five minutes before the countdown enters a planned half-hour hold at the T-minus 2 hour point. Once the clocks resume counting, fueling activities will begin.

Our live play-by-play coverage of the countdown and flight of the Atlas 5 will begin at approximately 3 p.m. from Cape Canaveral.

1226 GMT (8:26 a.m. EDT)

The Atlas 5 rocket is on the move this morning. Sitting on the mobile launch platform, the rocket has emerged from the Vertical Integration Facility for rollout to the pad. Launch remains scheduled for 5:57 p.m. EDT.

0126 GMT (9:26 p.m. EDT Mon.)

Launch of the Atlas 5 rocket has been officially rescheduled for Tuesday.

Technicians working in the Vertical Integration Facility Monday night successfully replaced the faulty part on the Atlas 5 rocket's Centaur upper stage that forced the initial launch attempt to be scrubbed. The component is described by Lockheed Martin as a data monitoring unit.

Managers meeting in a teleconference a short time ago approved plans to reset the launch for 5:57 p.m. EDT (2157 GMT) Tuesday.

"We are ready to go," a company spokesperson said.

The rocket will be rolled back to the launch pad Tuesday morning.

The weather forecast calls for nearly ideal conditions during the 34-minute launch window. See the full forecast here.

MONDAY, MAY 12, 2003
2050 GMT (4:50 p.m. EDT)

With the Atlas 5 back in the Vertical Integration Facility, workers will be able to examine the rocket to determine how to fix the vehicle instrumentation anomaly experienced today. Replacement of the suspect hardware is an option, a launch spokesperson said.

Senior officials plan to hold a 9 p.m. EDT teleconference tonight to determine if the launch can be attempted on Tuesday. If the efforts to resolve the problem precludes a Tuesday launch shot, another opportunity is possible on Wednesday.

We will update this page as news becomes available.

1953 GMT (3:53 p.m. EDT)

The Lockheed Martin Atlas 5 rocket has been returned to its assembly building at Cape Canaveral's Complex 41 so workers can troubleshoot the instrumentation glitch that occurred during today's countdown. Specific details about the problem have not been released.

Officials say that if the problem can be corrected quickly, the rocket could be rolled back to the pad Tuesday morning. Liftoff would be targeted for 5:57 p.m. EDT (2157 GMT) -- the opening of a 34-minute window.

A backup launch opportunity on the Eastern Range is available Wednesday at 5:58 p.m. EDT.

This second Atlas 5 mission will loft the Greek Hellas Sat communications spacecraft. Operating from a parking slot at 39 degrees East longitude in geostationary orbit, Hellas Sat will relay television, Internet and multimedia services to users across Greece, Cyprus, Europe, parts of Africa and the Middle East.

1922 GMT (3:22 p.m. EDT)

The Atlas 5 rocket is currently en route from the launch pad to the Vertical Integration Facility following the postponement of today's liftoff.

1750 GMT (1:50 p.m. EDT)

The launch weather team has issued a new weather forecast that includes the conditions expected this afternoon for rollback of the Atlas 5 rocket from the launch pad to the Vertical Integration Facility and conditions for a launch opportunity tomorrow. See the full forecast here.

1740 GMT (1:40 p.m. EDT)

Mission officials are meeting to discuss the technical problem, which is now being described as a vehicle instrumentation issue, and the course of action to resolve the situation. We will post further information as it is confirmed.

1645 GMT (12:45 p.m. EDT)

SCRUB! Today's launch attempt for Atlas 5 has been scrubbed. Lockheed Martin officials say a glitch has been uncovered with the Centaur upper stage avionics. A new launch date has not been announced. More details to follow!

1600 GMT (12:00 p.m. EDT)

Launch of the Atlas 5 rocket to put the Greek Hellas Sat communications satellite into orbit is just under six hours away. Liftoff remains scheduled for 5:57 p.m. EDT.

"Everything is going excellently with our countdown right now. We are right on our timelines," Atlas launch director Adrian Laffitte told reporters at a morning news conference. "We are working no major issues."

Air Force Launch Weather Officer Jim Sardonia has improved the odds of acceptable conditions during today's 34-minute window. His latest forecast now calls for just a 20 percent chance that cumulus and anvil clouds will present a problem. See the full forecast here.

1407 GMT (10:07 a.m. EDT)

The weather forecast for today's Atlas 5 launch has improved to show an 80 percent chance of acceptable conditions.

1328 GMT (9:28 a.m. EDT)

Atlas 5 is on the pad! The second Atlas 5 rocket has arrived at the Complex 41 launch pad for today's 5:57 p.m. EDT (2157 GMT) liftoff with the Greek Hellas Sat communications satellite.

The two mobile trailers connected to the launching platform, which were part of the convoy during this morning'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.

Within the next hour, the auto couplers between the pad and platform will be engaged to route umbilical connections from the ground to the rocket.

At around 11 a.m. EDT (1500 GMT), the Atlas first stage and Centaur upper stage are scheduled to be powered up. During the next hour, testing of the rocket's guidance system will start, followed by flight control system preps and a closed-loop check of the flight termination safety system.

At approximately 12:20 p.m. EDT (1620 GMT), the "MEGA Door" on the Vertical Integration Facility will be closed and efforts to clear the area of personnel begins.

A variety of other standard countdown operations will continue into the early afternoon hours.

A weather briefing is planned at 3:12 p.m. EDT (1920 GMT), just five minutes before the countdown enters a planned half-hour hold at the T-minus 2 hour point. Once the clocks resume counting, fueling activities will begin.

The pre-launch news conference is coming up at 10 a.m. Our next update on this page will be following the briefing.

1242 GMT (8:42 a.m. EDT)

Rollout underway! Riding on the 1.4-million pound mobile launching platform, the 191-foot tall Atlas 5 rocket is slowly inching its way out of Lockheed Martin's Vertical Integration Facility at Cape Canaveral Air Force Station's Complex 41. Driving along rail tracks, the platform should arrive at the pad in about a half-hour.

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

1237 GMT (8:37 a.m. EDT)

Countdown begins! Clocks at Cape Canaveral's Complex 41 have started ticking down to today's launch of the Atlas 5 rocket carrying a Greek communications satellite. This 9-hour, 20-minute countdown includes 40 minutes of built-in hold time. The planned holds will occur at T-minus 2 hours, before fueling operations begin, and at T-minus 4 minutes for final checks. Liftoff is slated to occur at 5:57 p.m. EDT (2157 GMT).

1145 GMT (7:45 a.m. EDT)

It is launch day for Atlas 5 and the Hellas Sat communications satellite for Greece and Cyprus. Liftoff from Complex 41 at Cape Canaveral remains scheduled for 5:57 p.m. EDT (2157 GMT). The available launch window extends to 6:31 p.m. EDT (2231 GMT).

If needed, the launch window on Tuesday is exactly the same; the window on Wednesday is 5:58 to 6:32 p.m. U.S. Air Force meteorologists continue to forecast a 70 percent chance of acceptable weather for today's launch.

In the Vertical Integration Facility, workers are preparing for this morning's transport of the Atlas 5 rocket to the launch pad. The move is targeted to begin at 8:47 a.m. EDT. Spaceflight Now is on the scene and we will post updates on the rollout when it occurs.

0130 GMT (9:30 p.m. EDT Sun.)

The jam-packed day of activities to launch Lockheed Martin's second Atlas 5 rocket begins at 5 a.m. EDT (0900 GMT) Monday when countdown preparations commence at Cape Canaveral Air Force Station, Florida. Liftoff is targeted to occur at 5:57 p.m. EDT (2157 GMT).

Unlikely the inaugural Atlas 5 mission that saw the rocket rolled from its assembly building to the pad the day prior to liftoff, 33 hours before launch time, the timeline for Monday's flight has been significantly compressed. Rollout is scheduled to occur just 9 hours before the rocket is supposed to blast away from the pad at Complex 41.

A weather briefing by Launch Weather Officer Jim Sardonia is slated for 8 a.m. (1200 GMT), providing Lockheed Martin managers with the forecast for the hours the rocket will be exposed to the elements on the launch pad from rollout through liftoff.

The countdown clocks will light up at T-minus 8 hours, 40 minutes at 8:37 a.m. EDT (1237 GMT). Planned holds in the count will lead to the opening of the day's 34-minute launch window at 5:57 p.m.

A readiness poll of team members will be conducted at 8:39 a.m. (1239 GMT) for a final "go" to roll. With no technical problems reported and acceptable weather, the mobile launcher platform should begin the 1,800-foot journey from the Vertical Integration Facility to the pad at 8:47 a.m. EDT (1247 GMT).

The rollout is expected to take about a half-hour. By 9:52 a.m. EDT (1352 GMT), the mobile platform should be firmly secured in place, allowing the automatic umbilical connectors between the ground and platform to engage and begin leak checks.

The rest of the morning will be spent powering up the rocket and running routine tests. The loading of super-cold cryogenic propellants into the vehicle will start approximately two hours before launch.

Watch this page for live updates Monday morning during the rollout of Atlas 5! And we will provide comprehensive live reports right here throughout the countdown and launch.

SUNDAY, MAY 11, 2003

The weather forecast has degraded a bit for Monday's opportunity to launch the Atlas 5 rocket at 5:57 p.m. EDT carrying the Greek Hellas Sat communications satellite. Launch Weather Officer Jim Sardonia is now predicting a 70 percent chance of acceptable conditions. See the full forecast here.

SATURDAY, MAY 10, 2003

Mission officials held the Launch Readiness Review at Cape Canaveral today to discuss final pre-flight preparations with the Atlas 5 rocket and Hellas Sat spacecraft cargo. With no significant problems being addressed, the meeting concluded with approval to press ahead with Monday's planned 5:57 p.m. EDT liftoff, a Lockheed Martin spokesperson said.

The weather forecast continues to predict an 80 percent chance of acceptable conditions. See the full forecast here.

FRIDAY, MAY 9, 2003

Air Force weather forecasters are now calling for an 80 percent chance of meeting the launch rules. See the full forecast here.

THURSDAY, MAY 8, 2003

Looking to make it two successes in a row, Lockheed Martin's next-generation Atlas 5 rocket will take its second flight Monday, blasting off from Florida's east coast carrying a commercial telecommunications satellite. Read our launch preview story.

Meanwhile, the early weather forecast calls for a 90 percent chance of good conditions. See the full forecast here.

And be sure to watch this page for live play-by-play updates throughout the day on Monday.

WEDNESDAY, FEBRUARY 26, 2003

The second flight of Lockheed Martin's Atlas 5 rocket has been postponed to replace the Centaur upper stage after a manufacturing concern was raised, managers announced Wednesday.

Launch was scheduled for March 14 from Cape Canaveral to deliver the Greek Hellas Sat communications satellite into Earth orbit. An official new date is pending.

A Lockheed Martin spokeswoman said a problem was uncovered with a welding station in the Centaur production factory. After the fault was found, technicians inspected the various Centaurs already built to determine if any had welds that were suspect.

Recent checks on the Centaur slated to fly on the upcoming Atlas 5, which had underwent a countdown dress rehearsal on the launch pad last week, revealed an issue with the stage's aft bulkhead.

That Centaur is being removed from atop the Atlas 5 for return to the factory. Another Centaur that is currently undergoing final assembly will be shipped to the Cape as the replacement.

"We are doing everything we can to ensure mission success for our Hellas Sat customer and are working diligently to recover the schedule impact to support the Hellas Sat mission," said John Karas, Lockheed Martin's vice president of Atlas and Advanced Space Transportation.

Officials have cleared the Centaur slated for the April 10 launch aboard an Atlas 3 rocket from the Cape. The AsiaSat 4 communications spacecraft is the payload for that mission -- the first Atlas of 2003.

WEDNESDAY, FEBRUARY 19, 2003

The Atlas 5 rocket was rolled back to the Vertical Integration Facility at Complex 41 this morning, successfully completing the countdown dress rehearsal. Lockheed Martin says the three-day event went smoothly and without any issues turning up. The rocket will now undergo final preparations for launch on March 14.

TUESDAY, FEBRUARY 18, 2003

The Lockheed Martin launch team today successfully fueled the Atlas 5 rocket and counted down to the simulated T-0 second mark at 12 noon EST. The countdown dress rehearsal paves the way for the March 14 launch of this second Atlas 5 and the Greek Hellas Sat communications spacecraft.

The rocket will be returned to the Vertical Integration Facility on Wednesday. Check back then for a full wrap-up story on this rehearsal and a look ahead to the rest of the launch campaign.

MONDAY, FEBRUARY 17, 2003

In advance of next month's launch of a Greek communications satellite, Lockheed Martin's second Atlas 5 rocket was transported to the pad Monday for a three-day countdown dress rehearsal.

Sitting atop its mobile launch platform, the rocket was rolled from the Complex 41 vehicle assembly building to the open-air pad at Cape Canaveral Air Force Station, Florida.

Unlike previous launch pad tests, the rocket isn't sporting a nose cone this time. After this rehearsal is completed, the Atlas 5 will be returned to the hangar so its cargo -- the Hellas Sat spacecraft -- can be attached for a planned March 14 blastoff.

Following Monday's morning rollout, a few hours were spent connecting the various propellant, electrical and other umbilicals. By early afternoon, the rocket's first stage had been loaded with its highly refined kerosene fuel. Workers completed the day's activities a few hours ahead of schedule, officials said.

Tuesday will see a complete launch day simulation with the rocket pumped full of super-cold cryogenic propellants as clocks count down to a mock liftoff time.

The countdown begins at 3:10 a.m. EST as the two-stage launcher is powered up. Over the course of the morning, routine checks and preps will be made on systems as technicians follow a timeline that mirrors an actual launch countdown.

During a planned half-hour hold in the count at T-minus 140 minutes, the launch team will be polled to ensure all is in readiness for fueling operations. Tanking-related activities commence once the clocks resume ticking.

By late morning, the Atlas first stage should be loaded with its liquid oxygen and the Centaur upper stage will be filled with liquid hydrogen and liquid oxygen.

Another hold is planned at T-minus 4 minutes for a duration of 10 minutes. The countdown is targeted to reach T-minus 0 seconds at 12 noon EST.

The cryogenics will be off-loaded from the rocket in the afternoon.

The rocket is scheduled to be rolled back to its vertical hangar on Wednesday, arriving around 11 a.m.

In the coming weeks, the Hellas Sat spacecraft cargo will be mounted atop the Atlas 5. The satellite is currently undergoing final pre-flight processing at the Astrotech facility near Titusville.

The rocket will be returned to the pad on March 13 -- the day prior to liftoff.