THURSDAY, OCTOBER 8, 2015
Churning out the launches at a rapid pace, the Atlas 5 program sent another rocket soaring like clockwork today for deployment of a national security satellite duo from California.

Read our launch story.

8:15 a.m. local (1515 GMT)
“Congratulations on today’s successful launch of NROL-55! ULA is honored to have collaborated with the NRO Office of Space Launch and the Air Force on the integration and launch of the NROL-55 spacecraft to orbit with our Atlas 5 vehicle,” said Jim Sponnick, ULA vice president, Atlas and Delta Programs. “Launches like this only happen with exceptional teamwork by an extremely talented team and a one-launch-at-a-time focus on mission success.”
7:25 a.m. local (1425 GMT)
Today's Atlas 5 rocket launch has been declared a success, deploying its National Reconnaissance Office payload into space. This was 129th successful Atlas launch in a row and 58th straight for Atlas 5. And it is the 101st successful flight by United Launch Alliance.
7:10 a.m. local (1410 GMT)
"This launch was a great achievement for Team Vandenberg, ULA, NRO and our launch partners," said Col. J. Christopher Moss, 30th Space Wing commander and the launch decision authority. "Their outstanding professionalism and team work ensured a fantastic launch and I am proud to work with this team of experts in support of national defense."
5:55 a.m. local (1255 GMT)
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.
5:54 a.m. local (1254 GMT)
T+plus 4 minutes, 31 seconds. The two halves of the four-meter-diameter Atlas 5 rocket nose cone encapsulating the spacecraft have separated.
5:53 a.m. local (1253 GMT)
T+plus 4 minutes, 22 seconds. Centaur has ignited! The RL10 engine is up and running at full thrust to power the vehicle into orbit.
5:53 a.m. local (1253 GMT)
T+plus 4 minutes, 12 seconds. The Atlas 5's Common Core Booster has been jettisoned, completing the first stage of flight, and the Centaur upper stage's liquid hydrogen and liquid oxygen systems are being readied for engine start.
5:53 a.m. local (1253 GMT)
T+plus 4 minutes, 4 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.
5:53 a.m. local (1253 GMT)
T+plus 3 minutes, 45 seconds. Atlas now weighs just a quarter of what it did at liftoff.
5:52 a.m. local (1252 GMT)
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.
5:52 a.m. local (1252 GMT)
T+plus 2 minutes, 50 seconds. Reaction control system has been activated.
5:52 a.m. local (1252 GMT)
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.
5:51 a.m. local (1251 GMT)
T+plus 2 minutes, 20 seconds. Atlas now weighs half of what it did at liftoff.
5:51 a.m. local (1251 GMT)
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.
5:51 a.m. local (1251 GMT)
T+plus 95 seconds. Now passing through the region of maximum aerodynamic pressure on the vehicle as its accelerates through the dense lower atmosphere.
5:50 a.m. local (1250 GMT)
T+plus 85 seconds. Mach 1. All looks good aboard the 19-story-tall rocket.
5:50 a.m. local (1250 GMT)
T+plus 60 seconds into the mission.
5:50 a.m. local (1250 GMT)
T+plus 45 seconds. An early sunrise for California's Central Coast.
5:49 a.m. local (1249 GMT)
T+plus 30 seconds. Pitch, yaw and roll maneuvers are complete, putting the Atlas 5 thunders away from the Central Coast with its RD-180 engine burning.
5:49 a.m. local (1249 GMT)
T+plus 15 seconds. The vehicle has cleared the tower at Space Launch Complex 3-East at Vandenberg.
5:49:30 a.m. local (1249:30 GMT)
LIFTOFF! Liftoff of the Atlas 5 rocket and NROL-55 payload, a new mission ensuring vigilance from above.
5:49:10 a.m. local (1249:10 GMT)
T-minus 20 seconds. "Go Atlas", "Go Centaur" "GO L-55" was just called by launch team during a final status check.
5:48:50 a.m. local (1248:50 GMT)
T-minus 40 seconds. Centaur's liquid oxygen and liquid hydrogen tanks are stable at flight pressures.
5:48:30 a.m. local (1248:30 GMT)
T-minus 1 minute until the launch. Range is GREEN.
5:48 a.m. local (1248 GMT)
T-minus 90 seconds. The safety system has been armed.
5:47 a.m. local (1247 GMT)
T-minus 1 minute, 50 seconds. Liquid oxygen and liquid hydrogen propellant topping to the Centaur upper stage is being secured.
5:47 a.m. local (1247 GMT)
T-minus 1 minute, 55 seconds. The launch sequencer has been commanded to start.
5:47 a.m. local (1247 GMT)
T-minus 2 minutes. The Atlas first stage and Centaur upper stage are now switching from ground power to internal batteries.
5:47 a.m. local (1247 GMT)
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.
5:46 a.m. local (1246 GMT)
T-minus 3 minutes. The Atlas first stage liquid oxygen replenishment is being secured so the tank can be pressurized for launch.
5:45 a.m. local (1245 GMT)
T-minus 3 minutes, 50 seconds. The ground pyrotechnics have been enabled.
5:45:30 a.m. local (1245:30 GMT)
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 NROL-55 satellite payload.
5:44:30 a.m. local (1244:30 GMT)
Countdown clocks will resume in one minute.
5:43 a.m. local (1243 GMT)
The ULA launch director and the NRO mission director have given their approval to press onward with the countdown.
5:43 a.m. local (1243 GMT)
All systems are reported "go" to continue with the countdown for liftoff at 5:49:30 a.m. The clocks will resume from this hold at 5:45 a.m.
5:41 a.m. local (1241 GMT)
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.
5:39 a.m. local (1239 GMT)
Now 10 minutes from launch.
5:30 a.m. local (1230 GMT)
Here's a look at some stats about today's mission. This will be:
5:20 a.m. local (1220 GMT)
Weather is observed GO and forecast GO for launch.
5:19 a.m. local (1219 GMT)
Liquid oxygen and liquid hydrogen tanks are at flight level.
5:15 a.m. local (1215 GMT)
T-minus 4 minutes and holding. The countdown has entered the planned hold to give the launch team a chance to review all systems before pressing ahead with liftoff.
5:14 a.m. local (1214 GMT)
T-minus 5 minutes and counting. Standing by to go into the final built-in hold that will last for 30 minutes.
5:09 a.m. local (1209 GMT)
The workhorse Centaur upper stage has flown in various configurations for decades. For this launch, the stage will use one Aerojet Rocketdyne-built RL10C-1 liquid oxygen/liquid hydrogen engine that develops a thrust of about 22,890 pounds.

The stage is 41.5 feet in length and 10 feet it diameter. It also houses the navigation unit that serves as the rocket's guidance brain.

5:03 a.m. local (1203 GMT)
The fuel-fill sequence for the first stage main engine is underway.
4:59 a.m. local (1159 GMT)
The Atlas 5 rocket's rigid body first stage is known as the Common Core Booster. The CCB replaced the "balloon" pressure-stabilized stage used by previous Atlas vehicles.

It is equipped with the RD-180 liquid-fueled main engine. This liquid oxygen/kerosene powerplant is a two-thrust chamber, two-nozzle engine.

As the CCB's name suggests, the stage is common and is used in all the various configurations of the Atlas 5 family. The booster stage is 106.6 feet long and 12.5 feet diameter.

4:49 a.m. local (1149 GMT)
Now 60 minutes from launch. All activities are proceeding smoothly toward a liftoff at 5:49:30 a.m. Pacific Time.

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4:37 a.m. local (1137 GMT)
The liquid hydrogen tank in the Centaur upper stage just reached the 96 percent level. Topping is now beginning.
4:34 a.m. local (1134 GMT)
Fast-filling of the first stage liquid oxygen has been completed. Topping mode is now underway.
4:30 a.m. local (1130 GMT)
The Centaur liquid hydrogen tank is 50 percent loaded so far. The cryogenic propellant will be consumed with liquid oxygen by the stage's Aerojet Rocketdyne-made RL10 engine.
4:25 a.m. local (1125 GMT)
Now beyond the three-quarters level of liquid oxygen on the first stage.
4:19 a.m. local (1119 GMT)
Now 90 minutes from liftoff. There are no reports of technical troubles from the launch team. Fueling operations remain in work for the launch time of exactly 5:49:30 a.m. local.
4:15 a.m. local (1115 GMT)
First stage liquid oxygen tank is passing the half-full mark. 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 minutes of flight today. The 25,000 gallons of RP-1 were loaded into the rocket earlier.
3:57 a.m. local (1057 GMT)
Centaur liquid oxygen is topping to flight level.
3:52 a.m. local (1052 GMT)
The Centaur liquid oxygen tank is 75 percent full now.

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

3:46 a.m. local (1046 GMT)
Half of the Centaur liquid oxygen tank has been filled so far.
3:42 a.m. local (1042 GMT)
The Centaur liquid oxygen tank is nearing 30 percent full already.
3:35 a.m. local (1035 GMT)
The conditioning of the systems for the first stage liquid oxygen tank have been completed. And a "go" has been given to begin flowing 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 about 50,000 gallons of cryogenic oxidizer for the RD-180 main engine.

3:30 a.m. local (1030 GMT)
Filling of the Centaur upper stage with about 4,300 gallons of liquid oxygen is beginning at Vandenberg's Space Launch Complex 3 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 loaded into the stage a little later in the countdown.

3:24 a.m. local (1024 GMT)
The Centaur liquid oxygen system's 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.
3:19 a.m. local (1019 GMT)
T-minus 2 hours and counting! The launch countdown has resumed for today's flight of the Atlas 5 rocket following the planned half-hour built-in hold.

Clocks have one more hold scheduled at T-minus 4 minutes. That pause will last 30 minutes during which time the final "go" for launch will be given.

All remains targeted for liftoff at 5:49 a.m. local time (1249 GMT) from Vandenberg Air Force Base in California.

3:17 a.m. local (1017 GMT)
The launch team and all systems are "ready" to proceed with the countdown and begin fueling the Atlas 5 rocket as planned.

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

3:14 a.m. local (1014 GMT)
The Atlas launch conductor is briefing his team on procedures before entering into the final two hours of the countdown. A readiness check of the team members is next.
2:49 a.m. local (0949 GMT)
T-minus 2 hours and holding. The countdown just entered the first of the planned holds over the course of the day that will lead to the 5:49 a.m.local launch of the Atlas-Centaur 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.

Workers have left the pad area in advance of today's propellant loading and launch of the Atlas 5 rocket.

2:30 a.m. local (0930 GMT)
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1:30 a.m. local (0830 GMT)
The 8-million-pound mobile service tower has been retracted from around the Atlas 5 rocket, revealing the 19-story-tall vehicle for liftoff at 5:49 a.m. local time today.

The ground crews are getting the gantry's doors closed, plus finishing the final buttoning up of pad equipment over before all workers clear the pad for the remainder of the countdown.

1:00 a.m. local (0800 GMT)
Rollback of the launch pad's service gantry is underway. This is a major milestone in today's countdown, getting the mobile tower retracted to uncover the Atlas 5 rocket.

The structure's internal crane was instrumental in bringing the rocket stages and payload together. And now the fully assembled Atlas 5 has been unveiled for its 51st launch, the 10th to originate from Vandenberg.

12:46 a.m. local (0746 GMT)
A readiness poll of the team has verified all systems are GO for retraction of the gantry.
12:00 a.m. local (0700 GMT)
Officials just received an updated weather forecast. There are no constraints to proceeding with mobile service tower rollback. Weather remains 70 percent GO for launch time.
10:55 p.m. local (0555 GMT)
Atlas and Centaur have been powered up. Guidance system testing is next.
9:59 p.m. local (0459 GMT)
Clocks begin ticking now for today's flight by the Atlas 5 rocket from America's western spaceport to deploy the NROL-55 payload into space.

As the countdown gets started, the launch team will power up the rocket to conduct standard pre-flight tests and ready the vehicle.

Rollback of the mobile service tower from around the rocket is expected in about three hours. Once the gantry is removed, crews at the pad will make preparations to systems and equipment before the site is cleared of all personnel for fueling.

Supercold liquid oxygen begins flowing into the Centaur upper stage, followed by the Atlas first stage. Liquid hydrogen fuel loading for Centaur will be completed a short time later.

A final hold is scheduled when clocks hit the T-minus 4 minute mark. That will give the team 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.

Liftoff remains targeted for 5:49 a.m. local time (8:49 a.m. EDT; 1249 GMT).

TUESDAY, OCTOBER 6, 2015
An Atlas 5 rocket has been cleared to launch early Thursday morning from Vandenberg Air Force Base in California to deploy a classified national security payload.

Officials held the Launch Readiness Review on Tuesday and gave approval to enter into the countdown on Wednesday night.

Thursday's liftoff is targeted for 5:49 a.m. local time (8:49 a.m. EDT; 1249 GMT) at the opening of a secret launch window.

A live launch webcast can be watched on this page beginning 20 minutes before launch.

Meteorologists give 70 percent odds that the weather will allow the launch to occur. Visibility is the only concern.

High pressure will begin building into the area on Wednesday. Winds will be out of the southeast from 5-10 knots and max upper wind levels will be northwesterly at 50 knots. Temperatures will be 58-63 degrees F.

"We are excited and ready to take on our first Atlas launch of 2015," said Col. J. Christopher Moss, 30th Space Wing commander. "Our team and mission partners have put a lot of hard work into preparing for this important mission for our nation."

The launch countdown starts around 10 p.m. local time Wednesday for the start of an eight-hour sequence to prepare the launch pad and rocket for flight.

This will be United Launch Alliance's 101st flight and the company's 20th in support of the National Reconnaissance Office.

"A launch like this takes teamwork and dedication," said Lt. Col. Eric Zarybnisky, 4th 4th Space Launch Squadron commander. "Our mission assurance technicians and engineers have worked hand-in-hand with United Launch Alliance going over critical procedures and tasks to ensure this launch is a safe and successful one."

MONDAY, OCTOBER 5, 2015
PREVIEW: Poised for its one and only satellite launch of the year, the National Reconnaissance Office will conduct a hush-hush flight Thursday, Oct. 8 using a United Launch Alliance Atlas 5 rocket from California.

Read our full story.