For the past four decades a band of orbiting sentinels has watched the world and sounded the alarm when enemy missiles take flight. Now, a new generation of advanced satellites that began launching Saturday will continue standing guard while also giving the U.S. military better insights into global hotspots.

Read our launch story.

And here's a full launch photo gallery from various pad cameras.

Check out photo galleries from the beach and the press site of today's launch.

The next Atlas rocket launch is scheduled for August 5 from Cape Canaveral to dispatch NASA's Juno probe on its voyage to orbit Jupiter, the king of planets.

"We understand the importance of the SBIRS mission and are proud to partner with the U.S. Air Force on this critical program," said Jeff Smith, Lockheed Martin's vice president and SBIRS program director, said in a post-flight news release. "Throughout the development of this first-of-its-kind satellite, our SBIRS team has demonstrated an unwavering commitment to operational excellence. As a result, we are confident SBIRS GEO-1 will deliver unprecedented, global, persistent, taskable infrared surveillance capabilities to the warfighter, nation and our allies for years to come."

"Today's successful launch is a tribute to the hard work, dedication and unmatched expertise of the entire government and industry SBIRS team. I am proud of the women and men who have worked on this spacecraft, and am confident the nation will be proud of its performance on orbit," Brig. Gen. (s) Roger Teague, director of SMC's Infrared Space Systems Directorate, said in a post-flight news release. "SBIRS GEO-1 represents the dawn of a new era in overhead persistent infrared surveillance that will greatly improve our national security for years to come."

"The SBIRS team stands tall today," Brig. Gen. (s) Roger Teague, director of SMC's Infrared Space Systems Directorate, said in a post-flight news release. "This launch success represents years of dedication and hard work by a broad team of government and industry professionals. We look forward to GEO-1 soon joining our constellation of overhead persistent infrared satellites and providing critical national security space capabilities."

"This day is a proud moment for our team," Col. Scott Larrimore, SBIRS space systems division chief, said said in a post-flight news release. "Our mission is just beginning, and we look forward to developing new capabilities that will expand the overhead persistent infrared missions to meet global emerging threats."

"The successful launch of the SBIRS mission today was a significant accomplishment for our nation," Col. Ron Fortson, chief of Evolved Expendable Launch Vehicle generation and operations division, said in a post-flight news release. "I am extremely proud of the integrated government and contractor team for the hard work and dedication put forth in achieving this success."

Today marked the 50th flight for United Launch Alliance's combined Atlas and Delta rocket families since the company was formed in December 2006 by Lockheed Martin and Boeing.

"With this launch, ULA continues to demonstrate its commitment to 100 percent mission success," Michael Gass, ULA President and CEO, said in a post-flight news release. "This milestone is a testament to the dedicated employees that for every mission deliver excellence, best value and continuous improvement to our customers."

"This is a very important day for our customers and for our nation," Jim Sponnick, United Launch Alliance's vice president of mission operations, said in a post-flight news release. "The ULA team is extremely proud to have served with this strong government and industry team in successfully launching the SBIRS GEO-1 satellite on its critical mission."

T+plus 43 minutes, 25 seconds. SPACECRAFT SEPARATION! The Centaur upper stage has deployed the first Space Based Infrared System Geosynchronous satellite into orbit following today's launch from Cape Canaveral.

T+plus 43 minutes, 20 seconds. Centaur has begun a one-degree-per-second roll for spacecraft deploy.

T+plus 42 minutes, 25 seconds. The thermal roll has been nulled out.

T+plus 42 minutes, 20 seconds. One minute away from releasing the payload.

T+plus 41 minutes. Current velocity is 19,380 mph.

T+plus 40 minutes, 30 seconds. Centaur is operating well with good battery voltages.

T+plus 40 minutes. Deployment of the SBIRS GEO-1 spacecraft to complete today's launch sequence is expected at 2:53 p.m. EDT.

T+plus 37 minutes, 30 seconds. The vehicle has crossed Africa. It's now soaring above the Indian Ocean while climbing away from the planet. Currently 800 miles in altitude.

T+plus 35 minutes. The upper stage continues in another thermal conditioning roll while quietly coasting in orbit.

T+plus 34 minutes. The Centaur's orbit is right on target with an apogee of approximately 22,225 statute miles, perigee of 115 statute miles and inclination of 21.64 degrees.

T+plus 30 minutes. Although the Centaur has finished firing, the rocket won't immediately deploy the payload. That milestone moment will wait about 15 minutes as the rocket crosses Africa and Madagascar, eventually flying within communications range of the Diego Garcia tracking station on an island in the Indian Ocean for live telemetry coverage of the critical event.

Release of the payload from the rocket to complete the launch is expected at T+plus 43 minutes.

T+plus 29 minutes. Centaur is turning itself to the proper orientation for releasing the payload.

T+plus 28 minutes, 14 seconds. MECO 2. Main engine cutoff confirmed. Centaur has completed its second burn of the day.

T+plus 26 minutes, 55 seconds. Vehicle acceleration is smooth at 1.1 g's.

T+plus 26 minutes, 15 seconds. About two minutes are left in the burn to reach the planned geosynchronous transfer orbit.

T+plus 25 minutes, 30 seconds. The engine is burning well. This is a planned four-minute firing by the Centaur's single Pratt & Whitney Rocketdyne RL10 engine.

T+plus 25 minutes. Bus and battery voltages, tank pressures and other system measurements look good.

T+plus 24 minutes, 20 seconds. Ignition and full thrust! The Centaur's single RL10 engine has re-ignited to accelerate the SBIRS GEO-1 payload into the planned deployment orbit.

T+plus 23 minutes. Centaur is getting pressurized again in preparation for the next engine burn.

T+plus 21 minutes, 30 seconds. Centaur is de-spinning out of its thermal roll.

T+plus 20 minutes. The flight path is taking the vehicle over the equatorial Atlantic Ocean, just off the western coast of Africa.

T+plus 19 minutes, 45 seconds. Centaur's onboard systems are stable in this coast period continues.

T+plus 18 minutes, 45 seconds. Centaur is performing a one-degree roll during this coast for thermal conditioning.

T+plus 17 minutes, 30 seconds. That first burn by Centaur inserted the rocket into the correct orbit.

T+plus 16 minutes, 30 seconds. All vehicle parameters still reported normal.

T+plus 16 minutes. The rocket is performing its turn to the proper position for the next engine firing.

T+plus 15 minutes, 35 seconds. MECO 1. Centaur's main engine has shut down following its first burn today, achieving a preliminary orbit around Earth. The rocket will coast in this orbit for about 9 minutes before the RL10 engine re-ignites.

T+plus 15 minutes, 10 seconds. Orbital velocity has been achieved.

T+plus 15 minutes. Centaur systems continue to be in good shape as the rocket nears orbit.

T+plus 14 minutes, 35 seconds. Everything looking normal with one minute to go in this burn.

T+plus 13 minutes, 25 seconds. Centaur remains on course and looking good. The vehicle is 2,083 miles downrange and speeding along at 15,749 mph.

T+plus 12 minutes, 5 seconds. RL10 engine parameters still look good.

T+plus 11 minutes, 35 seconds. About four minutes are left in this burn of Centaur.

T+plus 11 minutes, 17 seconds. The rocket is 195 miles in altitude, some 1,583 miles downrange and traveling at 14,093 mph.

T+plus 10 minutes. All systems reported stable as the Centaur fires to reach an initial Earth orbit.

T+plus 9 minutes, 15 seconds. Centaur is 195 miles in altitude, 1,140 miles downrange from the launch pad, traveling at 12,758 mph.

T+plus 8 minutes, 45 seconds. Centaur is accelerating at 0.47 g's.

T+plus 7 minutes, 40 seconds. Now 154 miles in altitude, 829 miles downrange from the launch pad, traveling at 11,954 mph.

T+plus 7 minutes, 15 seconds. The RL10 continues to perform well, burning liquid hydrogen and liquid oxygen propellants.

T+plus 6 minutes, 35 seconds. The rocket is 155 miles in altitude, some 626 miles downrange and traveling at 11,536 mph.

T+plus 5 minutes, 45 seconds. The rocket is tracking right down the planned flight path.

T+plus 5 minutes, 20 seconds. The rocket is 117 miles in altitude, some 403 miles downrange and traveling over 11,150 mph already.

T+plus 5 minutes. Centaur engine readings look good as this burn gets underway.

T+plus 4 minutes, 25 seconds. Centaur has ignited! The RL10 engine is up and running at full thrust for its first of two planned firings today.

T+plus 4 minutes, 32 seconds. The two-halves of the Atlas 5 rocket nose cone encapsulating the spacecraft have separated.

T+plus 4 minutes, 14 seconds. The Atlas 5's Common Core Booster first stage has been jettisoned, and the Centaur upper stage's liquid hydrogen and liquid oxygen systems are being readied for engine start.

T+plus 4 minutes, 6 seconds. BECO. Booster Engine Cutoff is confirmed as the RD-180 powerplant on the first stage completes its burn. Standing by to fire the retro thrusters and separate the spent stage.

T+plus 3 minutes, 50 seconds. The vehicle is accelerating at 5 g's.

T+plus 3 minutes, 25 seconds. The rocket now weighs only a quarter of what it did at liftoff.

T+plus 3 minutes. RD-180 is performing well as the rocket climbs away from the planet.

T+plus 2 minutes, 45 seconds. Reaction control system has been activated.

T+plus 2 minutes. The rocket is tracking on course.

T+plus 1 minutes, 45 seconds. The RD-180 main engine continues to fire normally, burning a mixture of highly refined kerosene and liquid oxygen.

T+plus 95 seconds. Maximum dynamic pressure.

T+plus 84 seconds. Mach 1.

T+plus 60 seconds. One minute into the ascent. It will take 43 minutes for the two-stage rocket to deploy the Space Based Infrared System Geosynchronous-1 satellite into the desired orbit.

T+plus 40 seconds. The thunderous roar from the Atlas is reverberating across the Cape. Good engine performance is reported from the rocket.

T+plus 15 seconds. The vehicle has cleared the towers at Complex 41 on 860,000 pounds of thrust from the RD-180 main engine.

LIFTOFF! Liftoff of the Atlas 5 rocket and SBIRS GEO-1, beginning a new era for surveillance sentinels in space.

T-minus 20 seconds. "Go Atlas" and "Go Centaur" was just called by launch team during a final status check.

T-minus 40 seconds. Centaur's liquid oxygen and liquid hydrogen tanks are stable at flight pressures.

T-minus 1 minute. Now 60 seconds left in the countdown to United Launch Alliance's 50th mission.

T-minus 90 seconds. The safety system has been armed.

T-minus 1 minute, 45 seconds. Liquid oxygen and liquid hydrogen propellant topping to the Centaur upper stage is being secured.

T-minus 1 minute, 55 seconds. The launch sequencer has been commanded to start.

T-minus 2 minutes. The Atlas first stage and Centaur upper stage are now switching from ground power to internal batteries.

T-minus 2 minutes, 30 seconds. The first stage RP-1 kerosene fuel tank and the liquid oxygen have stepped up to proper flight pressure levels.

T-minus 3 minutes. The Atlas first stage liquid oxygen replenishment is being secured so the tank can be pressurized for launch.

T-minus 3 minutes, 50 seconds. The ground pyrotechnics have been enabled.

T-minus 4 minutes and counting. Clocks have resumed for the final minutes of today's countdown to launch the Atlas 5 rocket carrying the Space Based Infrared System Geosynchronous-1 spacecraft. Liftoff is set to occur at 2:10 p.m. EDT.

Countdown clocks will resume in one minute.

SBIRS GEO-1 is running on internal power and configured for launch.

The ULA launch director has given his "go" for today's on-time liftoff.

Polling of the team by Atlas launch conductor just occurred. All technical systems are reported "go" to continue with the countdown for liftoff at 2:10 p.m. EDT.

Standing by for the final readiness check to be conducted again. The launch team will be polled for a "go" or "no go" to proceed with the count.

Here's a look at some stats about today's mission. This will be:

• The 608th launch for Atlas program since 1957
• The 320th Atlas to occur from Cape Canaveral
• The 26th launch of an Atlas 5 since 2002
• The 22nd Atlas 5 to occur from the Cape
• The 18th Atlas 5 under United Launch Alliance
• The 11th Atlas 5 to fly in the 401 configuration
• The 13th Department of Defense launch of Atlas 5
• The 3rd Atlas launch of 2011
• And this is United Launch Alliance's 50th mission

The SBIRS GEO-1 satellite nestled inside the nose cone of the Atlas 5 rocket is switching to internal power for launch.

The first stage liquid oxygen tank and Centaur's liquid oxygen and liquid hydrogen tanks are reported at flight level.

T-minus 4 minutes and holding. The countdown has entered the planned 10-minute hold to give the launch team a chance to review all systems before pressing ahead with liftoff. But the clocks will remain stopped at this point until the weather improves.

T-minus 5 minutes. Standing by to go into the final built-in hold.

The official forecast for today's 40-minute launch window extending from 2:10 to 2:50 p.m. EDT continues to predict good weather with some haze, north-northeasterly winds of 12 to 16 knots and a temperature of 77 degrees. There's no weather constraints to worry about this afternoon.

Now just 20 minutes away from launch.

A reminder that if you will be away from your computer but would like to receive occasional countdown updates, sign up for our Twitter feed to get text message updates on your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

And check out Spaceflight Now's Facebook page!

Take a unique look around Cape Canaveral's Complex 41 launch pad with these panoramic images taken on Thursday afternoon. They show the Atlas 5 rocket standing poised for blastoff carrying SBIRS GEO-1, the Space Based Infrared System Geosynchronous-1 missile warning satellite.

Thirty minutes from liftoff. The countdown clocks are heading to the T-minus 4 minute mark where a planned 10-minute hold will occur. Launch of Atlas 5 remains scheduled for 2:10 p.m. EDT.

Pre-launch checks of the rocket's safety system have been completed.

Just 45 minutes until liftoff time of the SBIRS GEO-1 satellite that begins the next generation of geosynchronous spacecraft to continuously look for missile launches and alert the national leadership and battlefield commanders.

The SBIRS GEO-1 spacecraft, which weighs about 10,000 pounds at launch, was built by Lockheed Martin using the company's commercial A2100 satellite design. It features a pair of power-generating solar arrays, two communications antenna wings that unfold and a deployable light shade to shield its sensitive infrared instruments.

Unlike the previous generation of Defense Support Program missile warning satellites that have only scanning sensors, the SBIRS GEO spacecraft has both scanning and staring instruments to increase the amount of reconnaissance that can be collected.

"We have two taskible sensors on the satellite," said Jeff Smith, Lockheed Martin's vice president and SBIRS program director. "One is a scanner and one is a starer. The scanner is used for global surveillance and the starer is used to look in certain areas. We can put it where ever we want, basically, to see dimmer targets and see faster burning targets. So the ability is to task this system to do both global and theater missions and intelligence missions simultaneously is really the revolutionary part of this system."

The SBIRS system will augment and gradually replace the heritage Defense Support Program satellites.

"Once launched and fielded, GEO-1 will bring the dawn of a new era in persistant overhead surveillance," said Brig. Gen. (s) Roger Teague, director of the U.S. Air Force's Infrared Space Systems Directorate.

"GEO-1 will play a vital role in our national security space architecture, and we look forward to getting this satellite on-orbit. After GEO-1 is launched, and early orbit tests are complete, SBIRS will deliver unprecedented, global, persistent, infrared surveillance capabilities to our nation for decades to come."

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

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

The first stage liquid oxygen tank is 90 percent full now.

The weather remains excellent and posing no worries today.

Now 60 minutes from liftoff. Fueling of the Atlas rocket with cryogenic liquid oxygen and liquid hydrogen is proceeding as planned for a liftoff at 2:10 p.m. EDT.

If you are heading out to Titusville or the beach to watch the launch, sign up for our Twitter feed to get occasional countdown updates on your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

The first stage liquid oxygen has reached the 80 percent level.

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

Chilldown of the liquid hydrogen system has been accomplished. The launch team has received the "go" to begin filling the Centaur upper stage with the supercold fuel.

First stage liquid oxygen tank is 50 percent full thus far. 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-quarter minutes of flight today. The 25,000 gallons of RP-1 were loaded into the rocket earlier.

The Centaur engine chilldown sequence is being initiated.

Upper stage liquid oxygen has reached flight level.

Now just 90 minutes away from launch.

A reminder that if you will be away from your computer but would like to receive occasional countdown updates, sign up for our Twitter feed to get text message updates on your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

And check out Spaceflight Now's Facebook page!

The Centaur liquid oxygen tank reached the 95 percent level. The topping off process is starting now.

The first stage liquid oxygen loading is switching from slow-fill to fast-fill mode.

The chilldown conditioning of liquid hydrogen propellant lines at Complex 41 is starting to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket. The Centaur holds about 12,680 gallons of the cryogenic propellant.

Centaur liquid oxygen is three-quarters full.

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 supercold liquid oxygen into the Atlas 5's first stage.

The Common Core Booster stage's liquid oxygen tank is the largest tank to be filled today. It holds 48,860 gallons of cryogenic oxidizer for the RD-180 main engine.

The Centaur liquid oxygen tank has reached the 30 percent mark.

Filling of the Centaur upper stage with about 4,150 gallons of liquid oxygen has begun at Cape Canaveral's Complex 41 following the thermal conditioning of the transfer pipes.

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 Centaur will perform two firings to propel the payload into geosynchronous transfer orbit.

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.

T-minus 120 minutes and counting! The launch countdown is continuing on schedule for today's flight of the Atlas 5 rocket with the first Space Based Infrared System Geosynchronous (SBIRS GEO-1) satellite aboard.

Clocks have one more built-in hold planned at T-minus 4 minutes. That pause will last 10 minutes during which time the final "go" for launch will be given. All remains targeted for liftoff at 2:10 p.m. EDT from Cape Canaveral's Complex 41.

In the next couple of minutes, chilldown thermal conditioning of the mobile launch platform upon which the rocket stands will begin. This is meant to ease the shock on equipment when supercold cryogenic propellants start flowing into the rocket.

After briefing his team on procedures before entering into the final two hours of the countdown, the launch conductor at the Atlas Spaceflight Operations Center just held a pre-fueling readiness poll. All console operators reported a "ready" status.

The ULA launch director also voiced his approval for proceeding with the countdown.

Loading of cryogenic liquid oxygen and liquid hydrogen into the Atlas 5 rocket will be getting underway a short time from now.

The SBIRS GEO-1 spacecraft was shipped from Lockheed Martin's manufacturing factory in Sunnyvale, California, to the Cape Canaveral Air Force Station on March 3 aboard a C-5 transport aircraft.

The satellite spent the next several weeks at the DSCS Processing Facility undergoing launch base confidence testing after shipment, fueling with 5,000 pounds of maneuvering propellant and encapsulation in the rocket's nose cone before its move to the Atlas' vertical assembly facility on April 26 for mounting atop the booster.

See a collection of photographs showing the satellite's launch campaign.

The Cape facilities received an infrastructure upgrade in preparation for this new breed for SBIRS satellites, including electrical, communications and environmental control and even a new access road from runway to processing building.

T-minus 2 hours and holding. The countdown has just entered the first of two planned holds over the course of the day that will lead to the 2:10 p.m. EDT launch of the Atlas rocket. This initial pause lasts 30 minutes, giving the team some margin in the countdown timeline to deal with technical issues or any work that is running behind. The final hold is scheduled to occur at T-minus 4 minutes and will last for 10 minutes.

The Complex 41 pad and the danger area have been cleared of all workers for the remainder of the countdown.

The launch weather officer has amended the forecast to reduce visibility down to 5 miles. There's a fire up north that is blowing haze into the Cape Canaveral area. But that won't be a problem for launch. Current conditions are acceptable and expected to remain that way all day.

Activities in the launch countdown this morning are proceeding nicely. No issues are being reported as clocks target a 2:10 p.m. EDT liftoff of the Atlas 5 rocket. The guidance system testing just wrapped up and the pad crew is finishing its hands-on work at Complex 41 now.

The hazard area roadblocks around the launch site's safety perimeter are being established now. And the launch team has started configuring the pad's water deluge system. Also, inspections of the pad have been completed.

A reminder that if you will be away from your computer but would like to receive occasional countdown updates, sign up for our Twitter feed to get text message updates on your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

And check out Spaceflight Now's Facebook page!

As soon as the countdown started this morning, the launch team began powering up the rocket to commence standard pre-flight tests and preparations for the mission.

Coming up, a planned half-hour hold begins at 11:30 a.m. when the count reaches T-minus 120 minutes. Near the end of the hold, the team will be polled at 11:57 a.m. to verify all is in readiness to start fueling the rocket for launch.

Supercold liquid oxygen begins flowing into the Centaur upper stage around 12:17 p.m., followed by the first stage filling around 12:30 p.m. Liquid hydrogen fuel loading for Centaur will be completed a short time later.

A final hold is scheduled at the T-minus 4 minute mark starting at 1:56 p.m. That 10-minute pause will give everyone a chance to finish any late work and assess the status of the rocket, payload, Range and weather before proceeding into the last moments of the countdown.

Today's launch window extends from 2:10 to 2:50 p.m. EDT (1810-1850 GMT).

What a difference a day makes. After yesterday's cloudy conditions that prohibited launch, skies are clear and forecasters are optimistic that the weather will cooperate today.

The official weather outlook for this afternoon's 40-minute launch window from 2:10 to 2:50 p.m. EDT is 90 percent favorable. Air Force meteorologists are calling for just some scattered clouds, good visibility, north-northeasterly winds of 12 to 16 knots and a temperature of 77 degrees.

If the launch is delayed for some reason, the forecast for tomorrow has an 80 percent chance of good weather. The odds are 70 percent favorable on Monday.

The countdown sequence has begun for this second attempt to launch the SBIRS GEO-1 spacecraft aboard the Atlas 5 vehicle. The next seven hours of work will prepare the rocket, payload and ground systems for the upcoming afternoon blastoff at 2:10 p.m. EDT.

Launch of the Atlas 5 rocket has been rescheduled for tomorrow at 2:10 p.m. EDT (1810 GMT).

Draining of the cryogenic liquid oxygen and liquid hydrogen from the Atlas rocket is getting underway following the scrub.

If officials reschedule the launch for tomorrow, the window will extend from 2:10 to 2:50 p.m. EDT. Weather forecasters expect a 90 percent chance of acceptable conditions.

A Sunday launch opportunity would be available between 2:06 and 2:46 p.m. EDT and an 80 percent chance of good weather.

SCRUB. The local weather conditions at Cape Canaveral will keep the Atlas 5 rocket on the launch pad today, postponing this mission to deploy the SBIRS GEO-1 missile warning satellite.

The launch team is progressing through the standard safing procedures after the countdown was stopped. The clocks have been recycled to T-minus 4 minutes and holding.

Today's launch window expires at 2:54 p.m. EDT.

The hope for the cumulus cloud constraint to clear for liftoff at 2:45 p.m. EDT obviously didn't materialize and the countdown clocks were halted.

HOLD! Countdown has stopped at T-minus 60 seconds due to the weather remaining "no go" for launch.

T-minus 90 seconds. The safety system has been armed.

T-minus 1 minute, 50 seconds. Liquid oxygen and liquid hydrogen propellant topping to the Centaur upper stage is being secured.

T-minus 1 minute, 55 seconds. The launch sequencer has been commanded to start.

T-minus 2 minutes. The Atlas first stage and Centaur upper stage are now switching from ground power to internal batteries.

T-minus 2 minutes, 30 seconds. The first stage RP-1 kerosene fuel tank and the liquid oxygen have stepped up to proper flight pressure levels.

T-minus 3 minutes. The Atlas first stage liquid oxygen replenishment is being secured so the tank can be pressurized for launch.

T-minus 3 minutes, 50 seconds. The ground pyrotechnics have been enabled.

T-minus 4 minutes and counting. Clocks have resumed for the final minutes of today's countdown to launch the Atlas 5 rocket carrying the Space Based Infrared System Geosynchronous-1 spacecraft. Liftoff is set to occur at 2:45 p.m. EDT.

Atlas is trying to get through a very small hole in the weather. Clocks will resume for liftoff at 2:45 p.m., but the final "go" on the clouds won't come until T-minus 60 seconds.

Polling of the team by Atlas launch conductor just occurred. All technical systems are reported "go" to continue with the countdown for liftoff at 2:45 p.m. EDT. Weather remains "red" but the clocks will be picking up.

Standing by for the final readiness check to be conducted again. The launch team will be polled for a "go" or "no go" to proceed with the count.

SBIRS GEO-1 is running on internal power and configured for launch.

Here's a look at some stats about today's mission. This will be:

• The 608th launch for Atlas program since 1957
• The 320th Atlas to occur from Cape Canaveral
• The 26th launch of an Atlas 5 since 2002
• The 22nd Atlas 5 to occur from the Cape
• The 18th Atlas 5 under United Launch Alliance
• The 11th Atlas 5 to fly in the 401 configuration
• The 13th Department of Defense launch of Atlas 5
• The 3rd Atlas launch of 2011

NEW LAUNCH TIME. The team is switching the target liftoff time to 2:45 p.m. EDT. Meteorologists think the cumulus cloud rule could be "go" by then.

The hold has been extended five more minutes, pushing launch time to 2:39 p.m.

Now half-way through today's 40-minute window.

The weather officer thinks there could be a narrow opportunity around 2:45 p.m. when cumulus clouds go "green" for a brief time in between these two weather cells.

Launch has been pushed back an additional five minutes to 2:34 p.m.

The field mill rule for electrical potential in the air has gone "green" for launch. The cumulus cloud rule violation remains in effect.

The target launch time has been delayed to 2:29 p.m. EDT. But that depends on the weather, obviously.

Another distinct weather cell has formed behind the one that's currently moving across the Cape.

The launch window has opened for today's shot for putting the SBIRS GEO-1 spacecraft into orbit.

Today's available launch window for the Atlas 5 rocket to blast off with the SBIRS GEO-1 satellite extends until 2:54 p.m. EDT (1854 GMT).

The team is keeping postured to pick up the countdown as soon as the weather will allow.

HOLD EXTENDED. The weather won't permit an on-time launch today. Clocks will remain holding at T-minus 4 minutes while waiting for conditions to improve.

The launch team is being polled for the pre-flight readiness check to continuing with the countdown. All systems are "go" except for the weather. The cumulus cloud and field mill rules are "red" for launch.

Joining the cumulus cloud rule as being "red" right now, the field mill criteria is "no go" now. That's the rule that governs the electrical potential in the air.

The SBIRS GEO-1 satellite nestled inside the nose cone of the Atlas 5 rocket is switching to internal power for launch.

The first stage liquid oxygen tank and Centaur's liquid oxygen and liquid hydrogen tanks are reported at flight level.

T-minus 4 minutes and holding. The countdown has entered the planned 10-minute hold to give the launch team a chance to review all systems before pressing ahead with liftoff. But the clocks will remain stopped at this point until the weather improves.

T-minus 5 minutes. Standing by to go into the final built-in hold.

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

The official forecast for today's 40-minute launch window extending from 2:14 to 2:54 p.m. EDT continues to predict rain showers and isolated thunderstorms, scattered low clouds at 2,500 feet, a broken deck of mid-level clouds at 10,000 feet and overcast skies at 25,000 feet, good visibility, southeasterly winds of 16 to 22 knots and a temperature of 77 degrees.

Weather is "red" now for cumulus clouds for the next 30 minutes at least, the launch meteorologist says. The seabreeze is responsible for developing that weather cell about 18 miles west of the pad.

Thirty minutes from liftoff. The countdown clocks are heading to the T-minus 4 minute mark where a planned 10-minute hold will occur. Launch of Atlas 5 remains scheduled for 2:14 p.m. EDT.

For the moment, the weather just went "green" across the board. The anvil cloud isn't being violated any longer. However, forecasters expect the cumulus cloud rule will be "red" starting at about 1:45 p.m.

Pre-launch checks of the rocket's safety system have been completed.

There is a weather cell that's popped up due west of the launch site that meteorologists are keeping a close eye on for potentially needing to issue a lightning advisory.

Just 45 minutes from launch time.

"SBIRS GEO-1 is a testament to strong government-industry partnerships, hard work and dedication of the entire SBIRS team. We remain focused on achieving mission success for this critical program," said Brig. Gen. (s) Roger Teague, director of the U.S. Air Force's Infrared Space Systems Directorate. "GEO-1 will play a vital role in our national security space architecture, and we look forward to getting this satellite on-orbit. After GEO-1 is launched, and early orbit tests are complete, SBIRS will deliver unprecedented, global, persistent, infrared surveillance capabilities to our nation for decades to come."

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

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

The latest weather briefing shows forecasters are keeping the odds at only 30 percent for acceptable conditions during the launch window. The attached anvil cloud rule remains "red" at this time.

Now 60 minutes from liftoff. Fueling of the Atlas rocket with cryogenic liquid oxygen and liquid hydrogen is proceeding as planned for a liftoff at 2:14 p.m. EDT.

If you are heading out to Titusville or the beach to watch the launch, sign up for our Twitter feed to get occasional countdown updates on your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

The first stage liquid oxygen has reached the 80 percent level.

Centaur's liquid hydrogen tank is 30 percent full. The cryogenic propellant will be consumed with liquid oxygen by the stage's Pratt & Whitney Rocketdyne-made RL10 engine.

Chilldown of the liquid hydrogen system has been accomplished. The launch team has received the "go" to begin filling the Centaur upper stage with the supercold fuel.

Half of the Atlas liquid oxygen tank has been filled so far.

First stage liquid oxygen tank is 40 percent full thus far. 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-quarter minutes of flight today. The 25,000 gallons of RP-1 were loaded into the rocket earlier.

The Centaur engine chilldown sequence is being initiated.

Upper stage liquid oxygen has reached flight level.

Now just 90 minutes away from launch, weather permitting. The Atlas 5 stands under cloudy skies at Complex 41, being fueled up for liftoff. There are no reports of any technical issues and the countdown is going very smoothly today.

The Centaur liquid oxygen tank reached the 95 percent level. The topping off process is starting now.

The first stage liquid oxygen loading is switching from slow-fill to fast-fill mode.

The chilldown conditioning of liquid hydrogen propellant lines at Complex 41 is starting to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket. The Centaur holds about 12,680 gallons of the cryogenic propellant.

Centaur liquid oxygen is three-quarters full.

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 supercold liquid oxygen into the Atlas 5's first stage.

The Common Core Booster stage's liquid oxygen tank is the largest tank to be filled today. It holds 48,860 gallons of cryogenic oxidizer for the RD-180 main engine.

For those of you keeping track of the shuttle Endeavour, we've just posted a new story on the repairs and potential target launch date.

The Centaur liquid oxygen tank has reached the 20 percent mark.

Filling of the Centaur upper stage with about 4,150 gallons of liquid oxygen has begun at Cape Canaveral's Complex 41 following the thermal conditioning of the transfer pipes.

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 Centaur will perform two firings to propel the payload into geosynchronous transfer orbit.

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.

T-minus 120 minutes and counting! The launch countdown is continuing on schedule for today's flight of the Atlas 5 rocket with the first Space Based Infrared System Geosynchronous (SBIRS GEO-1) satellite aboard.

Clocks have one more built-in hold planned at T-minus 4 minutes. That pause will last 10 minutes during which time the final "go" for launch will be given. All remains targeted for liftoff at 2:14 p.m. EDT from Cape Canaveral's Complex 41.

In the next couple of minutes, chilldown thermal conditioning of the mobile launch platform upon which the rocket stands will begin. This is meant to ease the shock on equipment when supercold cryogenic propellants start flowing into the rocket.

After briefing his team on procedures before entering into the final two hours of the countdown, the launch conductor at the Atlas Spaceflight Operations Center just held a pre-fueling readiness poll. All console operators reported a "ready" status.

The ULA launch director also voiced his approval for proceeding with the countdown.

Loading of cryogenic liquid oxygen and liquid hydrogen into the Atlas 5 rocket will be getting underway a short time from now.

A reminder that if you will be away from your computer but would like to receive occasional countdown updates, sign up for our Twitter feed to get text message updates on your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

And check out Spaceflight Now's Facebook page!

T-minus 2 hours and holding. The countdown has just entered the first of two planned holds over the course of the day that will lead to the 2:14 p.m. EDT launch of the Atlas rocket. This initial pause lasts 30 minutes, giving the team some margin in the countdown timeline to deal with technical issues or any work that is running behind. The final hold is scheduled to occur at T-minus 4 minutes and will last for 10 minutes.

The Complex 41 pad and the danger area have been cleared of all workers for the remainder of the countdown.

The launch weather officer is expecting violations of the "attached anvil cloud rule" off and on throughout the afternoon from the weather system moving through Central Florida. And he has dropped the odds of acceptable conditions for launching the Atlas rocket today down to just 30 percent.

The latest outlook for the launch window is calling for rain showers and isolated thunderstorms, scattered low clouds at 2,500 feet, a broken deck of mid-level clouds at 10,000 feet and overcast skies at 25,000 feet, good visibility, southeasterly winds of 16 to 22 knots and a temperature of 77 degrees.

The current weather is "no go" for launch due to violation of the rules governing anvil clouds. The weather team keeps managers updated when rules switch from "green" to "red" during the countdown.

The guidance system testing has been reported complete.

The hazard area roadblocks around the launch site's safety perimeter are being established now. And the launch team has started configuring the pad's water deluge system. Also, testing is being conducted of the C-band system used to track the rocket as it flies downrange and the S-band system for telemetry relay from vehicle.

Good day from the Kennedy Space Center where we are watching the final four hours in the countdown for today's launch of the Atlas 5 rocket and the Space Based Infrared System Geosynchronous-1 satellite. Activities are proceeding on schedule for a liftoff at 2:14 p.m. EDT from the Florida spaceport.

The weather is looking okay right now. However, meteorologists are expecting conditions to get iffy as the day goes along starting with a violation of the anvil cloud rule perhaps around 11 a.m. But we'll just have to see how the weather develops between now and launch time.

"The SBIRS team is nearly 9,700 members strong across 23 different states," said Brig. Gen. (s) Roger Teague, director of the U.S. Air Force's Infrared Space Systems Directorate.

"The SBIRS payload is built in Azusa, CA with the satellite integrated in Sunnyvale, CA," explains Teague. "SBIRS satellites are launched from Cape Canaveral Air Force Station, Florida, and the satellites will be operated by Air Force crews in Colorado. All across these locations are thousands of people at work daily, designing, building and integrating key systems and assemblies for the Space Based Infrared System. Internationally, the SBIRS program employs hundreds of people specializing in payload component production and sustainment of our crucial Relay Ground Stations. Just as our domestic suppliers and their employees, our international partners continue to proudly represent critical assets to the SBIRS program."

The weather outlook for this afternoon's 40-minute launch window has been downgraded to 40 percent favorable. Air Force meteorologists are calling for rain showers and isolated thunderstorms, scattered low clouds at 2,500 feet, a broken deck of mid-level clouds at 10,000 feet and overcast skies at 25,000 feet, good visibility, southeasterly winds of 14 to 18 knots and a temperature of 77 degrees.

Cumulus clouds and lightning are potential threats to violating the launch weather rules today.

But the forecast for tomorrow, if the launch is delayed for some reason, predicts a 90 percent chance of good weather. The odds are 80 percent favorable on Sunday.

The countdown clocks are starting to tick for today's launch of the SBIRS GEO-1 spacecraft aboard the Atlas 5 vehicle. The next seven hours of work will prepare the rocket, payload and ground systems for the upcoming afternoon blastoff.

Soon the launch team will begin powering up the rocket to commence standard pre-flight tests. Over the subsequent few hours, final preps for the Centaur's liquid oxygen and liquid hydrogen systems will be performed, along with a test of the rocket's guidance system and the first stage propulsion and hydraulic preps, internal battery checks and testing of the C-band system used to track the rocket as it flies downrange, plus a test of the S-band telemetry relay system. The Complex 41 site will be cleared of all personnel at 11:19 a.m.

A planned half-hour hold begins at 11:34 a.m. when the count reaches T-minus 120 minutes. Near the end of the hold, the team will be polled at 12:01 p.m. to verify all is in readiness to start fueling the rocket for launch.

Supercold liquid oxygen begins flowing into the Centaur upper stage around 12:21 p.m., followed by the first stage filling around 12:34 p.m. Liquid hydrogen fuel loading for Centaur will be completed a short time later.

A final hold is scheduled at the T-minus 4 minute mark starting at 2:00 p.m. That 10-minute pause will give everyone a chance to finish any late work and assess the status of the rocket, payload, Range and weather before proceeding into the last moments of the countdown.

Today's launch window extends from 2:14 to 2:54 p.m. EDT (1814-1854 GMT).

Take a unique look around Cape Canaveral's Complex 41 launch pad with these panoramic images as the Atlas 5 rocket stands poised for blastoff carrying SBIRS GEO-1, the Space Based Infrared System Geosynchronous-1 missile warning satellite.

Check out today's gallery of photos showing the Atlas 5 rocket poised on the launch pad here.

Trekking to its Cape Canaveral launch pad today, an Atlas 5 rocket is getting ready for Friday afternoon's planned blastoff carrying the inaugural spacecraft in the U.S. military's modernized approach to missile warning.

Rumbling away from the planet on nearly a million pounds of thrust, the Atlas 5 will be flying in its most basic, two-stage configuration without any added strap-on motors.

The RD-180 first stage main engine will ignite at T-minus 2.7 seconds, shooting a giant cloud of steam from the pad's main exhaust duct while undergoing a check to ensure its vital signs are healthy, leading to liftoff at T+plus 1.1 seconds.

Ten previous missions have relied on this version of the launcher, each displaying a slow and majestic ascent trailing only a flickering golden flame from its Russian-designed main engine.

Once above its launch pad, the rocket sets sail for the journey downrange over the Atlantic Ocean, constantly gaining speed as its double-nozzle engine gulps 25,000 gallons of kerosene fuel and 50,000 gallons of superchilled liquid oxygen in just four minutes.

The bronze first stage, its propellants depleted and job now completed, then jettisons with the help of tiny thrusters. Some 106.5 feet long and 12.5 feet around, the stage is discarded to fall back into the open sea.

The cryogenic Centaur upper stage ignites moments after shedding the lower booster, lighting its tried-and-true RL10 engine for 22,300 pounds of thrust to continue clawing toward orbit.

Covered with insulating foam and adorned with mission logos, this stage stretching 41.5 feet in length and 10 feet in diameter must perform two burns during the launch.

Shortly after the upper stage begins firing, the two-piece aluminum nose cone that shrouded the Space Based Infrared System Geosynchronous-1 satellite during flight through the atmosphere becomes no longer necessary and separates to expose the payload to space for the first time.

Centaur will fire for more than 11 minutes to reach a temporary parking orbit around Earth. Once it has achieved the intended perch, the RL10 engine shuts down and the rocket begins a quiet 9-minute coast over the central Atlantic.

The Pratt & Whitney Rocketdyne RL10 cryogenic engine then restarts just north of the equator for a four-minute firing to propel the spacecraft into the targeted geosynchronous transfer orbit stretching from 115 statute miles at its lowest point to 22,236 statute miles at its highest and inclined 21.64 degrees.

Although the Centaur finishes firing by T+plus 28 minutes, 10 seconds, the rocket won't immediately deploy the payload. That milestone moment will wait about 15 minutes as the rocket crosses Africa and Madagascar, eventually flying within communications range of the Diego Garcia tracking station on an island in the Indian Ocean. The separation event happens while inside the telemetry coverage zone from that Air Force ground site.

Release of the payload from the rocket to complete the launch occurs at T+plus 43 minutes, 20 seconds.

"We anticipate our Atlas 5 performing exceptionally well, allowing SBIRS GEO-1 to enhance greater military utility against evolving threats and to address critical warfighter needs," said Jim Sponnick, United Launch Alliance vice president for mission operations.

Built by Lockheed Martin with help from Northrop Grumman, the SBIRS GEO-1 satellite begins the next generation of geosynchronous spacecraft that continuously watch the world to spot missile launches and alert the national leadership and battlefield commanders.

The system will augment and gradually replace the heritage Defense Support Program satellites.

"SBIRS GEO-1 will usher in a new era of critical missile warning capabilities vital to our national security, and we are focused on delivering mission success for the warfighter," said Jeff Smith, Lockheed Martin's vice president and SBIRS program director. "The dedication, talent and integrity of the entire SBIRS team has been remarkable, and this launch will be a testament to every individual who has supported this vitally important program."

The satellite has six firings of its liquid apogee engine planned to circularize the orbit and reach geosynchronous altitude about 9 days after liftoff. The Air Force expects the check to be thoroughly checked out and accepted into the missile warning network as a trusted guard by next summer.

On the pad! The Atlas 5 rocket has arrived at the Complex 41 pad for tomorrow's ascent with the SBIRS GEO-1 spacecraft.

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 rollout and 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 for tomorrow's fueling of the booster with cryogenic propellants.

Later this afternoon, the undercarriages used to move the mobile platform will be disconnected and the "trackmobiles" pulled free.

Ground crews will secure the rocket for a quiet evening leading into Friday's launch opportunity. Countdown clocks will start ticking at about seven hours before liftoff time.

The day's 40-minute launch window opens at 2:14 p.m. and closes at 2:54 p.m. EDT.

If the flight is scrubbed for some reason, a backup launch opportunity is available on Saturday between 2:10 and 2:50 p.m. EDT.

And a reminder that if you will be away from your computer but would like to receive occasional countdown updates, sign up for our Twitter feed to get text message updates on your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

The rocket is passing through the pad entrance gate.

The weather forecast for tomorrow's launch now calls for a 60 percent chance of acceptable conditions during the afternoon's 40-minute launch window. Air Force meteorologists are calling for a chance of isolated showers and thunderstorms, scattered low clouds and a broken deck of high clouds, good visibility, southeasterly winds of 14 to 18 knots and a temperature of 77 degrees.

The outlook for Saturday is 80 percent favorable.

The Atlas 5 rocket is emerging from its vehicle assembly building for the journey to the launch pad.

Riding atop a mobile launching platform, the 189-foot-tall space booster is moving to Cape Canaveral's Complex 41 for this critical flight to deploy the first Space Based Infrared System Geosynchronous spacecraft.

The rocket's rollout to the pad has begun!

The Vertical Integration Facility's sliding doors are open and the Atlas rocket can be seen standing tall on its mobile launching platform. Rollout is scheduled to get underway at around 10 a.m. EDT.

With the final readiness readiness reviews now complete, officials have concurred that the Atlas 5 rocket and its SBIRS GEO-1 satellite payload are ready for Thursday morning's rollout to the launch pad.

The slow half-hour drive from the 30-story Vertical Integration Facility to Cape Canaveral's Complex 41 pad uses a pair of specially-made "trackmobiles" to carry the rocket's 1.4-million pound mobile launching platform along rail tracks for the 1,800-foot trip.

The two-stage rocket was put together inside the assembly building and the Space Based Infrared System Geosynchronous-1 spacecraft was mounted atop the vehicle last week.

The Atlas 5 is designed to spend minimal time at the launch pad, which does not include a service gantry like other rockets.

Blastoff remains on schedule for Friday afternoon during the 2:14 to 2:54 p.m. EDT launch window.

Weather forecasters now predict a 70 percent chance of favorable conditions for the space shot. The outlook includes scattered low- and high-level clouds, the potential for isolated showers, good visibility, east-southeasterly winds of 14 to 18 knots and a temperature around 77 degrees F.

"On launch day, high pressure persists over Central Florida with an increase of return moisture from the south resulting in a slight increase in the shower threat during the count with a greater threat late afternoon. Winds expected from the east to east-southeast with gusts in the mid to upper teens through the count and window. The primary concern for launch is cumulus clouds," meteorologists say.

Watch this page for complete live countdown and launch coverage!

Check out this collection of photographs shows the SBIRS GEO-1 satellite inside its Cape Canaveral processing building being encapsulated within the two-piece rocket nose cone, then being delivered to the Vertical Integration Facility for mounting atop the Atlas 5 booster.

The early weather forecast for Friday's scheduled launch of the Atlas 5 rocket from Cape Canaveral carrying a missile warning satellite is predicting good conditions for the blastoff.

Air Force meteorologists have set the odds at 80 percent favorable for liftoff during the afternoon launch window running from 2:14 to 2:54 p.m. (1814-1854 GMT). The only slight concern is violating the cumulus cloud rule.

"High pressure and fair weather over Central Florida through Tuesday in advance of next cold front on Wednesday. The cold front transits the peninsula through the day on Wednesday with isolated showers and a small lightning threat. The front is expected to be South of Central Florida Thursday morning and stalling in South Florida on launch day," forecasters say.

"On launch day, high pressure continues to build into Central Florida with winds becoming easterly with gusts in the mid to upper teens through the count and window. The primary concern for launch is a small threat of cumulus clouds.

The launch time conditions are predicted to include scattered clouds at 3,000 and 24,000 feet, possibly some isolated showers, good visibility, easterly winds of 12 to 16 knots and a temperature of 77 degrees F.

"In the event of a 24-hour delay, similar conditions prevail," forecasters say.

With just 10 days to go until launch, a critical surveillance satellite that begins a new generation for missile early-warning detection has been mounted atop its Atlas 5 rocket at Cape Canaveral.

The first Space Based Infrared System Geosynchronous spacecraft, or SBIRS GEO-1, was hauled from up the road from the processing hangar to the launcher's assembly hangar at Complex 41 before dawn Tuesday. Technicians then went to work with the delicate hoisting operations.

Already packed within the rocket's pointy nose cone, the satellite slowly rose up and entered the Vertical Integration Facility where the Atlas 5 stood atop a mobile launching platform, just waiting to receive its cargo for flight.

"When the transporter arrives at the base of the VIF, the Vertical Integration Facility, we then connect our overhead crane to it and lift that encapsulated assembly -- both the payload fairing and the spacecraft -- vertically and then translate it over to center it over the upper stage of the launch vehicle and then very carefully lower it in place, then mate both the spacecraft to its structural adapter and we also mate the outer ring of the payload fairing to its corresponding structure on the launch vehicle," said Jim Sponnick, United Launch Alliance vice president for mission operations.

Getting the payload aboard the rocket was the last major milestone before the 19-story vehicle is wheeled to the launch pad the day before liftoff. Teams will spend the next week conducting final checks and assessments to ensure all elements are ready to go.

"Between now and launch day we have our final major integrated system test, or IST, where we test all of the interfaces between the launch vehicle and the spacecraft thoroughly before day-of-launch. Other than that, we have our final closeout processes for all the compartments on the launch vehicle in preparation for the roll of the launch vehicle, the spacecraft and the mobile launch platform out to the launch pad next Thursday," Sponnick said.

"We do have a final set of reviews also between now and then. We have what we call the System Certification Review next Tuesday, which is our final opportunity for our major subcontractors and for all our certified responsible engineers -- these are the engineers responsible for each of the major components and systems on the launch vehicle -- providing their final technical assessment of the readiness of the their systems for launch. Then we have a series of final Launch Readiness Reviews next Wednesday, both a ULA launch readiness review early in the morning and then a launch readiness review with Gen. Wilson and the 45th Space Wing later in the day."

Launch is scheduled for Friday, May 6 during a window extending from 2:14 to 2:54 p.m. EDT (1814-1854 GMT).

"It's been a highly dedicated team working extremely hard to get us to this point. We delivered the booster here and then erected it on March 24. We're now to the point where we have the satellite mated to the launch vehicle. All of the processing to date has been nominal," said Col. Myron Fortson, mission director for the SBIRS GEO-1 launch. "We're looking forward to delivering this important payload into orbit so our nation can take full advantage of it."

The Air Force is planning to launch four SBIRS GEO satellites in the coming years to augment and eventually replace the heritage Defense Support Program spacecraft. The DSP era dates back to 1970 for spotting enemy missile launches and nuclear explosions.

"GEO-1 will provide our nation with significantly improved missile warning capabilities and support a number of other critical missions simultaneously, including missile defense, technical intelligence and battlespace awareness," said Brig. Gen. (s) Roger Teague, director of the U.S. Air Force's Infrared Space Systems Directorate.

Watch this page for continuing coverage of the Atlas flight with SBIRS GEO-1.

A reminder that if you will be away from your computer but would like to receive countdown updates, sign up for our Twitter feed to get text messages on your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

And check out Spaceflight Now's Facebook page!