Soaring in fine fashion before daybreak, a United Launch Alliance Delta 4 rocket maneuvered a new spy satellite into a unique retrograde orbit this morning to join an expanding constellation of radar-imaging spacecraft.

Read our launch story.

“Congratulations to the ULA team and our U.S. Air Force and NRO partners on the launch of NROL-45,” said Laura Maginnis, ULA vice president of Custom Services.

“This is our second successful launch within five days for our U.S. government customer, a testament to our outstanding teamwork and focus on 100 percent mission success, one launch at a time. ULA is proud to be entrusted with safely and reliably delivering our nation’s most critical space assets to orbit.”

MISSION SUCCESS declared in today's ascent to deliver NROL-45 to orbit for National Reconnaissance Office aboard the United Launch Alliance Delta 4 rocket from Vandenberg Air Force Base in California.

The United Launch Alliance Delta 4 rocket has flown into a news blackout. The veil of secrecy surrounding the launch of this clandestine satellite 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, 30 seconds. Now above the discernible atmosphere, the protective nose cone enclosing the secret National Reconnaissance Office satellite payload atop the rocket has jettisoned.

T+plus 3 minutes. The main engine continues to burn, consuming its liquid hydrogen and liquid oxygen propellants.

T+plus 2 minutes, 30 seconds. The Aerojet Rocketdyne RS-68A is consuming nearly a ton of propellants per second as the powerplant pushes the Delta 4 rocket closer to space.

T+plus 2 minutes. The Delta 4 rocket now weighs only half of what it did at liftoff two minutes ago.

T+plus 1 minute, 45 seconds. Solid motor separation! The spent boosters have been shed from the first stage. Delta 4 continues powering its way on the thrust generated by the main engine.

T+plus 1 minute, 35 seconds. The pair of Orbital ATK solid rocket boosters have burned out of their propellant. Standing by for jettison.

T+plus 60 seconds. Now passing through the region of maximum aerodynamic pressure.

T+plus 50 seconds. The launcher has broken through the sound barrier.

T+plus 30 seconds. The Delta 4 rocket is thundering away from Vandenberg on the second mission in the Medium+ (5,2) configuration with a pair of solid boosters and five-meter-diameter payload shroud.

LIFTOFF! The National Reconnaissance Office's latest bird takes flight from Vandenberg as the Delta 4 rocket clears the tower!

T-minus 12 seconds. Residual hydrogen burnoff ignitors have been fired beneath the main engine.

T-minus 22 seconds. The steering system for the solid rocket motor nozzles has been activated.

T-minus 40 seconds. Upper stage liquid hydrogen tank is confirmed at flight level.

T-minus 55 seconds. The Air Force-controlled Western Range has given its "go" for launch.

T-minus 1 minute and counting. The ignition conditions for the RS-68A main engine are "go." Ignition of the powerplant will follow at T-minus 5 seconds. The engine powers up to full thrust for a computer-controlled checkout before liftoff.

T-minus 75 seconds. The liquid hydrogen fuel tank on the upper stage is being secured for launch.

T-minus 80 seconds. Upper stage liquid oxygen tank has been secured at flight level.

T-minus 1 minute, 50 seconds. The first stage liquid hydrogen tank has reached flight level and pressure.

T-minus 2 minutes. The rocket's upper stage liquid oxygen tank is being secured.

T-minus 2 minutes, 30 seconds. The liquid oxygen tank in the first stage is confirmed at the proper level and pressure for flight.

T-minus 3 minutes and counting. Ordnance devices aboard the vehicle are being armed.

T-minus 3 minutes, 25 seconds. The systems of the first and second stages of the Delta 4 rocket have switched from ground-fed power to internal batteries for launch.

T-minus 3 minutes, 30 seconds. Replenishment of liquid hydrogen and liquid oxygen to the Common Booster Core first stage is being secured in preparation to pressurize the tanks for launch.

T-minus 4 minutes and counting! Now into the final phase of the countdown for liftoff at 3:40:32 a.m. by the Delta 4 rocket carrying the NROL-45 payload from Space Launch Complex 6 at Vandenberg Air Force Base.

Standing by to resume the countdown in one minute.

Permission to launch has been granted by the ULA launch director and NRO mission director.

The final readiness polls of the launch team and mission managers have been completed. No technical problems are being worked and all rocket, spacecraft and ground systems are "go" for liftoff at 3:40:32 a.m.

Now 12 minutes to launch. The launch team will be polled in the next few minutes to confirm all systems are "go" to press onward for 3:40:32 a.m. liftoff.

The countdown is entering the final minutes until the Delta 4 rocket launch from Vandenberg at 3:40:32 a.m. Here's a look at some stats about today's mission. This will be:

• The 373rd Delta rocket launch since 1960
• The 31st Delta 4 rocket mission since 2002
• The 2nd Medium+ 5,2 configuration to fly
• The 47th main engine from RS-68 family used
• The 5th RS-68A main engine flown
• The 48th-49th GEM-60 solid rocket motors flown
• The 466th production RL10 engine to be launched
• The 33rd RL10B-2 engine launched
• The 6th Delta 4 rocket launch from Vandenberg
• The 9th classified Delta 4 for the NRO
• The 92nd Evolved Expendable Launch Vehicle flight
• The 105th United Launch Alliance mission since 2006
• The 24th Delta 4 under the ULA banner
• The 2nd ULA launch this year
• The 1st launch of the Delta family in 2015

This is the 31st Delta 4 rocket launch. It has flown 17 Defense Department flights, 8 for the National Reconnaissance Office and 5 commercial missions since 2002.

Upper stage fuel and oxidizer conditioning for flight is complete.

T-minus 4 minutes and holding. The countdown has entered the planned 31-minute, 27-second hold leading toward the 3:40:32 a.m. liftoff of the Delta 4 rocket.

This pause is designed to give the launch team the opportunity to catch up on any work running behind schedule and verify all is in readiness for the final moments of the count. Also, a series of polls will be conducted during the hold to give approval to proceed with the launch.

First stage liquid hydrogen conditioning for flight is complete.

Radio frequency link checks have been completed satisfactorily.

Launch minus 45 minutes!

One hour till launch! The rocket stands fueled and ready for launch at 3:40:32 a.m. today. The countdown remains on track.

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The first stage liquid oxygen tank is conditioned for flight.

The flight slews and commanding tests for the vehicle steering systems are being performed. The first stage Common Booster Core, the strap-on solid rocket motors and upper stage engine steering checks were run through a pre-launch test pattern.

Engineers are conducting the standard evaluation of the Delta 4 rocket's thermal insulation following the loading of supercold propellants into the vehicle.

The vehicle is fully fueled! Loading of the upper stage liquid hydrogen tank has been accomplished to give the Delta 4 its cryogenic commodities.

Now entering into the final 90 minutes of the countdown to launch of Delta 373 and the NROL-45 payload for the National Reconnaissance Office.

NEW LAUNCH TIME. Liftoff time has been adjusted slightly to 3:40:32 a.m. local (6:40:32 a.m. EST; 1140:32 GMT).

Loading of the upper stage liquid oxygen tank has been accomplished as fueling proceeds today at Space Launch Complex 6.

Two hours and counting.

The first stage liquid oxygen loading just finished. The tank has been loaded with its supercold oxidizer that is chilled to Minus-298 degrees F. Topping will be completed as the count rolls on.

Fast-filling of the first stage liquid hydrogen tank is complete. After post-filling checks and valve tests, the tank will be placed in topping mode. The launch team will confirm the propellant is conditioned for flight.

Chilldown of the upper stage liquid oxygen system is complete for loading the rocket's tank. This is the last of the rocket's four cryogenic supplies to be filled in today's countdown to launch.

The Delta 4 rocket's Common Booster Core first stage and upper stage are being loaded with supercold liquid oxygen and liquid hydrogen.

The cryogenics are fed from the storage tanks through pipelines to the pad. For the Common Booster Core, the propellants are routed up to the launch table upon which the rocket sits. Tail service masts, the large box-like structures at the base of the vehicle, feed the oxygen and hydrogen to the booster via separate umbilicals.

The upper stage receives its cryos from the swing arm that extends from the Fixed Umbilical Tower to the front-side of the rocket.

After chilldown of the upper stage liquid hydrogen system, the GO was given for loading the rocket's tank. The launch team is actively filling the upper stage's liquid hydrogen tank with propellant for the RL10 engine.

The "go" has been given for the upper stage liquid oxygen chilldown in advance of filling that tank.

First stage liquid oxygen tanking operation is switching from "slow-fill" to "fast-fill" mode. The rocket will be loaded with 40,000 gallons of supercold LOX.

Now three hours from liftoff at exactly 3:39:05 a.m.

The first stage liquid oxygen chilldown is complete. "Slow-fill" mode is beginning to load a small percentage of the tank. The process then speeds up to the "fast-fill" mode until the tank is nearly full.

The launch team is preparing to start fueling the Delta 4 rocket's upper stage. The "go" has been given to start the chilldown conditioning of the upper stage liquid hydrogen system.

First stage liquid hydrogen tanking operation is switching from "slow-fill" to "fast-fill" mode.

And now the chilldown of Delta's first stage liquid oxygen system is starting. This preps the tank and pumping to guard against shock when the supercold oxidizer begins flowing into the rocket a short time from now.

Liquid hydrogen flow to the first stage is confirmed. Some 110,000 gallons of LH2 will fill the rocket's tank.

The cold gas chilldown conditioning of the liquid hydrogen system has been accomplished. Liquid hydrogen propellant will begin to flow into the first stage in "slow-fill" mode. That is sped up to "fast-fill" after a small portion of the tank is loaded.

Chilled to Minus-423 degrees Fahrenheit, the liquid hydrogen will be consumed by the RS-68A main engine along with liquid oxygen during the first four minutes of the launch.

A "go" has been given to start the cold gas chilldown conditioning of the first stage liquid hydrogen system. This is the precursor to filling the vehicle with propellant.

The valve issue has been resolved and the workers are leaving the launch pad. Countdown activities will be resuming shortly.

Mission officials have directed a special team to return to the launch pad for the manual adjustment of an unresponsive valve. This will delay the start of fueling until the hazard area around Space Launch Complex 6 is clear again. There's currently no impact to the 3:39 a.m. launch time since the countdown has margin to deal with issues like this.

T-minus 4 hours, 15 minutes and counting. The team is ready for cryogenic fueling as the countdown is underway for today's opportunity to launch the Delta 4 rocket with the NROL-45 payload at 3:39 a.m. local.

The launch team is manning stations for the start of cryogenic fueling operations.

T-minus 4 hours, 15 minutes and holding. The countdown has entered a 30-minute built-in hold, a pre-planned pause designed to give the team time to catch up on any work that could be running behind schedule. Once the clocks resume ticking, the main countdown for today's launch operation will begin.

At the launch pad, clearing of personnel is underway before the start of fueling operations.

T-minus 5 hours, 30 minutes and counting. The clocks have resumed counting after a 30-minute built-in hold. Liftoff remains targeted for 3:39 a.m. local.

The powerup of the Delta 4 rocket's avionics is starting.

The 32-story-tall mobile service tower is being retracted from the Delta 4 rocket at Vandenberg's Space Launch Complex 6 pad for today's flight that will place a surveillance satellite into orbit for the U.S. National Reconnaissance Office.

The wheeled structure, a modified piece of hardware from the pad's history as a manned launch site, is moving along rail tracks to its retracted position east of the rocket.

The 13-million-pound gantry shielded the Delta from the elements during the stay on the pad since July, provided workers 360-degree access to the various areas on the vehicle and was instrumental in attaching the strap-on solid motors and the payload during the launch campaign.

Crews will spend the next couple of hours securing the complex for launch before leaving the danger area around the pad. All workers must be clear of the area for the start of hazardous operations in the countdown, which include fueling the vehicle later tonight.

Liftoff remains scheduled for 3:39 a.m. local. The actual length of the day's available launch window to get the rocket airborne today is not disclosed to the public.

Ready to support the national security needs of the country, a Delta 4 rocket is poised for liftoff early Wednesday from California to deliver a classified payload into space.

Liftoff from Vandenberg Air Force Base of the United Launch Alliance rocket is planned for 3:39 a.m. local (6:39 a.m. EST; 1139 GMT).

"Things are looking really great. I was down at the pad this morning, giving the rocket one last look. The weather looks great, we had a beautiful weekend, the weather is great today and the forecast for (Wednesday) is looking really well," Lt. Col. Eric Zarybnisky, 4th Space Launch Squadron commander, said in a telephone interview from Vandenberg on Monday.

"Our final closeout activities are going on today and tomorrow, kind of the normal flow as we pull some of those remove-before-flight pins and items. We've already moved the mobile assembly shelter out of the way. That was done late last week," he added.

This will be the 31st Delta 4 rocket launch since debuting in 2002 and the sixth to fly from Vandenberg.

"It's hard to say it is just another Delta. Every rocket is unique. There's a lot of intricacies built in. Each of the missions have their own unique flavor. And there's a lot of folks who come together to make the mission happen. It is hard to say it is just another rocket, because it is rocket science at the end of the day," Zarybnisky said.

The two-stage rocket was rolled from the Horizontal Integration Facility to the pad in July to be hydraulically raised into the vertical position atop the launch table.

A full countdown dress rehearsal and fueling exercise occurred in early November.

The payload, already encapsulated in the rocket's 5-meter nose cone, was lifted from the payload processing facility at Space Launch Complex 6 and transported the short distance to the rocket for mating in mid-January.

Countdown activities will get underway Tuesday evening with retraction of the mobile service gantry and the start of fueling operations that will continue into the early morning of Wednesday.

"This launch will deliver a vital capability to our warfighters and our nation," said Zarybnisky, who will serve as the Air Force launch director.

"There really is no day without space. Launch is the gateway to that high ground. We stress that to our folks every day that hey, this isn’t just another launch. Each one of them is drastically important."

PREVIEW: Beginning the National Reconnaissance Office's campaign of four launches in 2016 using boosters big and small to deploy a varied collection of new intelligence satellites, a Delta 4 rocket stands ready for liftoff before sun-up Wednesday from California.

Read our preview story.

PREVIEW: It was 1986 and the U.S. Air Force was on the cusp of something unprecedented in human spaceflight -- launching a space shuttle crew from California and paving the way for people to fly true polar missions.

Read our preview story.