Setting sail at mid-day on a marathon trip to orbit, an Atlas 5 rocket launched a classified spacecraft for the National Reconnaissance Office on Thursday.

Read our launch story.

MISSION SUCCESS. The Atlas 5 rocket has successfully delivered its clandestine payload into orbit today.

"We are honored to deliver this national security asset to orbit together with our customers the NRO Office of Space Launch and the Air Force," said Jim Sponnick, ULA vice president, Atlas and Delta Programs.

"Successfully launching two missions from two different coasts in just seven days is a testament to the team's one-launch-at-a-time focus and ULA's commitment to mission success and schedule reliability."

The United Launch Alliance Atlas 5 rocket has flown into a pre-arranged news blackout following jettison of the rocket's payload shroud. The veil of secrecy surrounding the launch of this clandestine satellite cargo means no further information about the progress of the ascent, upper stage engine firings or release of the payload will be announced in real-time.

T+plus 3 minutes, 20 seconds. The two-halves of the Atlas 5 rocket nose cone encapsulating the spacecraft have separated, exposed the satellite to space. Also jettisoned was the Forward Load Reactor, a two-piece deck that rings the Centaur stage to support the bulbous fairing during launch.

T+plus 3 minutes, 10 seconds. The RD-180 main engine continues to fire normally, burning a mixture of highly refined kerosene and liquid oxygen.

T+plus 2 minutes, 50 seconds. Reaction control system has been activated.

T+plus 2 minutes, 30 seconds. Everything still looking good on the first stage as the rocket powers downrange on the thrust being produced by the main engine.

T+plus 2 minutes, 10 seconds. Vehicle is right on course.

T+plus 1 minute, 55 seconds. All four of the Aerojet Rocketdyne-made solid rocket motors have successfully separated from the Atlas 5, having completed their job of adding a powerful kick at liftoff.

T+plus 93 seconds. Solid rocket booster burnout has occurred. But the spent motors will remain attached to the first stage for a few seconds, until the Atlas 5 reaches a point where the airborne dynamic pressure reduces to an allowable level for a safe jettison.

T+plus 60 seconds into this complex mission.

T+plus 50 seconds. A period of maximum dynamic pressure is being experienced by the rocket.

T+plus 45 seconds. Mach 1.

T+plus 40 seconds. The main engine is throttling down to ease the stresses on the vehicle in the lower atmosphere.

T+plus 15 seconds. Pitch, yaw and roll maneuvers are underway as the Atlas 5 thunders away from Cape Canaveral with its RD-180 engine and four solid rocket boosters burning.

LIFTOFF! Liftoff of the Atlas 5 rocket on a classified satellite deployment flight. And the vehicle has cleared the tower!

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

T-minus 55 seconds. Range is green.

T-minus 1 minute. Now 60 seconds away from launching the second Mobile User Objective System communications satellite to continue orbital construction of a five-spacecraft network to span the globe.

T-minus 90 seconds. The rocket's 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 are enabled.

T-minus 4 minutes and counting. Clocks have resumed for the final minutes of today's countdown to launch the Atlas 5 rocket with a new spacecraft for the NRO from Cape Canaveral, Florida.

Standing by to pick up the count.

ULA launch director has given his respective final approvals to resume the countdown.

Polling of the team by Atlas launch conductor just occurred. All systems are "go" for a liftoff today at 2:48 p.m. EDT.

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

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.

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

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

The final planned weather briefing to launch officials just occurred and the current observed conditions are GO.

Just 30 minutes until liftoff time.

Today marks the 45th flight for Atlas 5, born of the Air Force's competition to develop next-generation Evolved Expendable Launch Vehicles. In its previous 44 missions since debuting in August 2002, the tally shows 16 flights dedicated to the Defense Department, 11 for NASA, 9 commercial missions with communications spacecraft and 8 with spy satellites for the National Reconnaissance Office.

Now 45 minutes from liftoff.

The liquid hydrogen tank in the Centaur upper stage just reached the 96 percent level. Topping is now beginning.

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

The official launch weather forecast has improved to greater than 90 percent chance of acceptable conditions for liftoff.

Centaur's liquid hydrogen tank is 40 percent full. The cryogenic propellant will be consumed with liquid oxygen by the stage's Aerojet Rocketdyne-made RL10 engine.

Now 60 minutes from liftoff. Fueling of the Atlas rocket with cryogenic liquid oxygen and liquid hydrogen is progressing smoothly as the countdown continues on schedule for a liftoff at 1:45 p.m. EDT. Weather remains GO.

If you are heading out to the beach or Port Canaveral 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.)

And if you are need tips on picking a good viewing spot, check out this authoritative guide on where to go.

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 minutes of flight today. The 25,000 gallons of RP-1 were loaded into the rocket prior to today.

The first stage liquid oxygen tank has reached the 20 percent mark.

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

The first stage liquid oxygen loading is transitioning 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 12,300 gallons of the cryogenic propellant.

Centaur liquid oxygen is 75 percent loaded.

The 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 48,750 gallons of cryogenic oxidizer for the RD-180 main engine.

Passing the 40 percent level on the Centaur upper stage's liquid oxygen tank.

Filling of the Centaur upper stage with about 4,100 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 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 has resumed for today's flight of the Atlas 5 rocket on the NROL-67 mission.

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 1:45 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.

All console operators have reported GO status during the pre-fueling readiness poll. The ULA launch director also voiced his approval for moving forward with the countdown as scheduled today.

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

The ULA launch conductor at the Atlas Spaceflight Operations Center is briefing his team on procedures before entering into the final two hours of the countdown.

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 1:45 p.m. EDT launch of the Atlas 5 rocket.

This initial pause was designed to give the team some margin in the countdown timeline to deal with technical issues or any work that could fall behind schedule before fueling starts. But all is going smoothly today, with officials not reporting any troubles in the count.

The final hold will occur at T-minus 4 minutes.

The final hands-on work has wrapped up at the launch pad and technicians have departed the complex. Safety officials just confirmed that the surrounding danger area has been cleared of all workers for the remainder of the countdown.

Guidance system testing has been accomplished as the countdown goes smoothly today at Cape Canaveral.

Atlas first stage propulsion, pneumatic and hydraulic preps have been accomplished. And launch pad cameras have been verified configured for monitoring fueling operations.

The hazard area roadblocks around the launch site's safety perimeter have been established. Also, the launch team is configuring the pad's water deluge system.

Internal battery checks are getting started as the counts the final four hours to launch.

The C-band and S-band systems are being tested at this point in the countdown. They are used for vehicle tracking and telemetry relay, respectively.The countdown continues on schedule for the 1:45 p.m. EDT launch.

In today's first weather briefing to mission managers, all current conditions are observed GO for launch of the Atlas 5 rocket and odds for the 1:45 p.m. EDT liftoff time stand at 90 percent favorable. The main concern that meteorologists will be watching is the thickness of clouds that the rocket would fly through.

The outlook for the launch window now predicts a few clouds at 4,000 and 32,000 feet, good visibility, easterly winds of 12 gusting to 15 knots and a temperature of 72 degrees F.

If the launch should slip to Friday for some reason, there is a 90 percent chance of acceptable weather with a similar forecast.

The Atlas-Centaur rocket has been powered up at Complex 41 and guidance system testing is getting started for today's launch, as the countdown progresses as planned.

The countdown begins now for the mid-day launch of the Atlas 5 rocket to deploy the National Reconnaissance Office's NROL-67 satellite for intelligence-gathering.

Clocks are picking up the seven-hour sequence of work that will prepare the booster, payload and ground systems for blastoff at 1:45 p.m. EDT (1745 GMT).

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 10:50 a.m.

A planned half-hour hold begins at 11:05 a.m. when the count reaches T-minus 120 minutes. Near the end of the hold, the team will be polled at 11:32 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 11:52 a.m., followed by the first stage filling around 12:05 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 1:31 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.

The launch window opens at 1:45 p.m. EDT (1745 GMT).

A powerful Atlas 5 rocket is being readied for launch Thursday afternoon to place a clandestine payload into space, possibly headed for geosynchronous orbit 22,300 miles above the Earth.

The United Launch Alliance-operated vehicle is capable of delivering 7,800 pounds directly into this type of orbit used by eavesdropping signals intelligence spacecraft.

The Launch Readiness Review was completed yesterday, and the rocket was rolled from its assembly building to the launch pad this morning.

Liftoff from Complex 41 at Cape Canaveral is planned for 1:45 p.m. EDT on Thursday afternoon.

There is a 90 percent chance of acceptable weather.

Here's a look at the countdown:

 HR:MM..Eastern...Event 
T-6:20...6:45am...Countdown begins with rocket power up 
T-5:30...7:35am...Weather briefing 
T-4:55...8:10am...Start clearing assembly building area 
T-4:20...8:45am...C-band tracking beacon testing 
T-3:40...9:55am...S-band telemetry link checks 
T-2:55..10:10am...Establish blast danger area roadblocks 
T-2:20..10:45am...Weather briefing 
T-2:15..10:50am...Clear the pad 
T-2:00..11:05am...T-120 minutes and holding (for 30min) 
T-2:00..11:30am...Launch conductor briefing to team 
T-2:00..11:33am...Readiness poll for fueling 
T-2:00..11:35am...Resume countdown 
T-1:50..11:45am...Centaur LOX transfer line chilldown 
T-1:43..11:52am...Begin Centaur liquid oxygen loading 
T-1:30..12:05pm...Begin Atlas first stage LOX loading 
T-1:25..12:10pm...Centaur LH2 transfer line chilldown 
T-1:10..12:25pm...Centaur RL10 engine chilldown 
T-1:02..12:35pm...Begin Centaur liquid hydrogen loading 
T-0:40..12:55pm...FLight termination system final test 
T-0:16...1:19pm...RD-180 engine fuel fill sequence 
T-0:10...1:25pm...Weather briefing 
T-0:04...1:31pm...T-4 minutes and holding (for 10min) 
T-0:04...1:38pm...Readiness poll for launch 
T-0:04...1:41pm...Resume countdown 
T-0:00...1:45pm...LAUNCH

The mission was delayed a couple of weeks by a Range radar failure. The outage prevented the Range from safely supporting the launch. Now, a new radar has been activated as a replacement.

The launch is known simply as NROL-67, a classified satellite-delivery flight for the U.S. National Reconnaissance Office. The NRO is the secretive government agency that controls the country's spy satellites.

The specific version of the Atlas 5 being used on this launch has been flown once before to lob NASA's Curiosity rover to Mars.

It is the 45th Atlas launch and the 9th for the NRO. It will be ULA's 81st launch overall and fourth of 15 this year.

The NRO has launched six times in the past two years using both Atlas and Delta rocket families.

The weather outlook for Thursday's Atlas 5 rocket launch at Cape Canaveral appears excellent with a 90 percent chance of acceptable conditions.

"Thursday, high pressure moves eastward into the Southeastern U.S. resulting in mostly sunny skies, dry conditions and easterly winds over the Cape. With easterly wind flow at the surface, expect isolated low-level clouds to move on-shore through the count," forecasters reported today.

The launch time forecast calls for few clouds at 3,000 and scattered clouds at 32,000 feet, good visibility, easterly winds of 12 peaking to 16 knots and a temperature of 70 degrees F.

If the launch is delayed to Friday for some reason, there's an 80 percent chance of good conditions.

Thick clouds are the main concern for both days.

After a two-week delay to wait for the U.S. Air Force to restore a critical radar tracker, United Launch Alliance and SpaceX have rescheduled their next rocket missions from Cape Canaveral for April 10 and April 14.

Read our full story.

Rocket launches from Cape Canaveral are grounded until at least mid-April after an electrical short damaged an Air Force radar at the Kennedy Space Center, officials said Friday.

Read our full story.

Marking only the seventh delay-and-rollback scenario in 37 flights from Cape Canaveral, the Atlas 5 rocket is being returned today to the assembly hangar ride out the Range outage and scheduling delays.

The Atlas originally moved from the nearby Vertical Integration Facility to the Complex 41 pad Monday morning. After experiencing back-to-back delays awaiting repairs to a damaged Range radar, the decision was made to stand down, rollback and allow a previously-planned West Coast Atlas mission fly next week.

Launch of this mission is tentatively retargeted for next April 10.

The Atlas 5 program at the Florida spaceport uses a "clean-pad" concept with minimal infrastructure. Instead, stacking of the rocket stages and pre-flight work is accomplished inside the user-friendly confines of the VIF building. The mobile launch platform transports the Atlas between the hangar and the pad, a distance of just 1,800 feet.

Four times in the history of the Atlas 5 program has a rocket been forced to roll back for technical reasons. Those instances were driven by circumstances that required hardware removal-and-replacement jobs be performed in the 30-story-tall VIF.

The previous rollbacks occurred on the Hellas Sat mission in 2003 to replace data instrumentation unit, the WGS 2 flight in 2009 to replace a leaky liquid oxygen valve, Intelsat 14 also in 2009 to replace an ordnance control assembly and most recently in June on NROL-38 to remove a faulty ground support equipment duct in the environmental control system.

One other rollback occurred in February 2012 due to an extended wait for Range availability after weather thwarted initial launch opportunities on the MUOS 1 flight.

Most recently, an Atlas 5 was rolled back to ride out Hurricane Isaac in August 2012.

ROLLBACK. The Atlas 5 rocket will be rolled back from the launch pad to its assembly hangar to wait out the Range troubles that have scuttled the planned flight this week with the classified NROL-67 payload for the National Reconnaissance Office.

A fire in a downrange radar tracking system is to blame, creating a gap in coverage of following the vehicle as it flies east.

A new target launch date is pending.

Meanwhile, the Vandenberg launch of a different Atlas remains set for next week carrying a military weather satellite.

DELAY. Liftoff has been pushed back an additional 24 hours to no earlier than Thursday afternoon. The 45th Space Wing experienced an outage Monday with a mandatory assess needed to support the launch. Teams continue to assess a path forward to resolve the issue.

It's too soon to know what impact, if any, these delays will have on the planned April 3 launch of an Atlas 5 from Vandenberg Air Force Base in California. ULA typically needs a week between flights to perform the necessary data reviews.

No decisions have been made about launching as early as Wednesday at 2:44 p.m. EDT as work continues to repair a Range outage. But here is a look at the countdown.

HR:MM..Eastern...Event 
T-6:20...7:44am...Countdown begins with rocket power up 
T-5:30...8:34am...Weather briefing 
T-4:55...9:09am...Start clearing assembly building area 
T-4:20...9:44am...C-band tracking beacon testing 
T-3:40..10:54am...S-band telemetry link checks 
T-2:55..11:09am...Establish blast danger area roadblocks 
T-2:20..11:44am...Weather briefing 
T-2:15..11:49am...Clear the pad 
T-2:00..12:04pm...T-120 minutes and holding (for 30min) 
T-2:00..12:29pm...Launch conductor briefing to team 
T-2:00..12:32pm...Readiness poll for fueling 
T-2:00..12:34pm...Resume countdown 
T-1:50..12:44pm...Centaur LOX transfer line chilldown 
T-1:43..12:51pm...Begin Centaur liquid oxygen loading 
T-1:30...1:04pm...Begin Atlas first stage LOX loading 
T-1:25...1:09pm...Centaur LH2 transfer line chilldown 
T-1:10...1:24pm...Centaur RL10 engine chilldown 
T-1:02...1:34pm...Begin Centaur liquid hydrogen loading 
T-0:40...1:54pm...FLight termination system final test 
T-0:16...2:18pm...RD-180 engine fuel fill sequence 
T-0:10...2:24pm...Weather briefing 
T-0:04...2:30pm...T-4 minutes and holding (for 10min) 
T-0:04...2:37pm...Readiness poll for launch 
T-0:04...2:40pm...Resume countdown 
T-0:00...2:44pm...LAUNCH

The weather forecast is 80 percent favorable for a possible launch on Wednesday. The outlook calls for scattered clouds, good visibility, breezy northwest winds of 16 peaking at 24 knots and a temperature of 57 degrees.

DELAY. A Range instrumentation problem has postponed tomorrow's launch of the Atlas 5 rocket at least 24 hours.

"45th Space Wing personnel are currently assessing the situation and working to identify the extent of repairs needed," officials said.

A photo gallery of today's rollout is posted here.

The Atlas 5 rocket stands atop its launch pad at Cape Canaveral for blastoff Tuesday afternoon to deploy a classified satellite for the U.S. National Reconnaissance Office.

The United Launch Alliance booster was rolled out to the Complex 41 pad shortly after 10 a.m. EDT today aboard a mobile platform, emerging from the assembly building where the rocket's two stages, four strap-on boosters and the payload were integrated starting Feb. 7.

Countdown clocks begin ticking Tuesday at 7:48 a.m. EDT, leading to activation of the rocket, final testing and system preps. Fueling operations start at 12:55 p.m.

The day's available launch opportunity begins at 2:48 p.m. EDT.

Here is a countdown timeline:

HR:MM..Eastern...Event 
T-6:20...7:48am...Countdown begins with rocket power up 
T-5:30...8:38am...Weather briefing 
T-4:55...9:13am...Start clearing assembly building area 
T-4:20...9:48am...C-band tracking beacon testing 
T-3:40..10:58am...S-band telemetry link checks 
T-2:55..11:13am...Establish blast danger area roadblocks 
T-2:20..11:48am...Weather briefing 
T-2:15..11:53am...Clear the pad 
T-2:00..12:08pm...T-120 minutes and holding (for 30min) 
T-2:00..12:33pm...Launch conductor briefing to team 
T-2:00..12:36pm...Readiness poll for fueling 
T-2:00..12:38pm...Resume countdown 
T-1:50..12:48pm...Centaur LOX transfer line chilldown 
T-1:43..12:55pm...Begin Centaur liquid oxygen loading 
T-1:30...1:08pm...Begin Atlas first stage LOX loading 
T-1:25...1:13pm...Centaur LH2 transfer line chilldown 
T-1:10...1:28pm...Centaur RL10 engine chilldown 
T-1:02...1:36pm...Begin Centaur liquid hydrogen loading 
T-0:40...1:58pm...FLight termination system final test 
T-0:16...2:22pm...RD-180 engine fuel fill sequence 
T-0:10...2:28pm...Weather briefing 
T-0:04...2:34pm...T-4 minutes and holding (for 10min) 
T-0:04...2:41pm...Readiness poll for launch 
T-0:04...2:44pm...Resume countdown 
T-0:00...2:48pm...LAUNCH

Weather forecasters will be keeping a close eye on cumulus clouds and cloud thickness that could violate rules and delay the liftoff. There's an overall 40 percent chance of acceptable weather for the 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 United Launch Alliance Atlas 5 rocket's rollout to the pad is underway!

This 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 20-story-tall satellite booster is moving to Cape Canaveral's Complex 41 for launch of NROL-67 mission.

The two-stage rocket, its four strap-on boosters and the payload were put together inside the assembly building over the past month-and-a-half in preparation for this rollout event. The Atlas 5 is designed to spend minimal time at the launch pad, which does not include a service gantry like other sites.

A powerful Atlas 5 rocket is being readied for launch Tuesday afternoon to place a clandestine payload into space, possibly headed for geosynchronous orbit 22,300 miles above the Earth.

Read our launch preview story.

The Launch Readiness Review was held Friday and reported all systems are GO for liftoff of the Atlas 5 rocket on Tuesday.

The rocket will be rolled from its assembly building to the launch pad at Cape Canaveral's Complex 41 on Monday morning.

The mission is known as NROL-67, a classified deployment flight for the National Reconnaissance Office.

A map released to the public shows the restricted area extends eastward from the Cape. Liftoff is planned for 2:48 p.m. EDT.

The weather forecast calls for a 40 percent chance of acceptable conditions, with a frontal system moving through the area. The main issues to watch will be cumulus clouds, anvil clouds, cloud thickness and lightning.

The launch time conditions are predicted to include scattered, broken and overcast cloud decks and rain showers, westerly winds 18 peaking to 30 knots and a temperature 73 degrees.

The outlook for Wednesday's backup attempt is only 30 percent favorable due to gusty ground winds.

The build up of the next United Launch Alliance Atlas 5 rocket to fly is being completed at Cape Canaveral today, as the payload is being mated to the Centaur upper stage.

Assembly began Feb 7 with first stage erection at the Vertical Integration Facility. That was followed over the next two weeks by attachment of the solid rocket boosters and Centaur.

The towering vehicle features two stages and four strap-on boosters to launch a classified payload for the National Reconnaissance Office. The mission is known simply as NROL-67.

Liftoff remains targeted for March 25 some time between 2:05 and 3:35 p.m. EDT.

It will be the second Atlas 5 of the year and ULA's 80th launch overall.

Assembly of a Atlas 5 rocket kicked off Friday morning at Cape Canaveral to stack a powerful version of the vehicle launching next month.

Read our full story.