Igniting a surge of three Global Positioning System satellite launches in the next five months, a Delta 4 rocket blazed a trail of fire and light into the Florida sky Thursday night.

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"Congratulations to the entire mission team on tonight's successful launch of the GPS 2F-5 satellite," said Jim Sponnick, ULA vice president, Atlas and Delta Programs.

"GPS provides vital capabilities for the men and women protecting our freedoms around the world and also provides ever-expanding benefits in our daily lives. We are privileged to collaborate with our dedicated government and industry partners seamlessly working together to deliver these capabilities safely to orbit with a focus on mission success, one launch at a time."

SPACECRAFT SEPARATION! The GPS satellite has been deployed by the Delta 4 rocket, completing tonight's launch!

To recap, a United Launch Alliance Delta 4 rocket was launched at 8:59 p.m. EST carrying a new Global Positioning System spacecraft to advance the navigation network with every launch.

We will post confirmation of spacecraft separation and mission success when announced.

T+plus 27 minutes. The rocket has just entered a two-hour, 56-minute coast period before the final engine burn to deliver GPS 2F-5 into the desired circular orbit to join the navigation network.

T+plus 25 minutes, 40 seconds. SECO 2. The second of three firings by the upper stage during today's launch has been completed.

T+plus 24 minutes. This burn injects the rocket into a highly elliptical orbit stretching out to the GPS constellation at its furthest point.

T+plus 23 minutes, 30 seconds. About one minute left in this burn by the Delta 4 rocket's upper stage.

T+plus 23 minutes. Engine control looking good as proper thrust.

T+plus 22 minutes. This burn will last just over three minutes in duration.

T+plus 21 minutes, 27 seconds. Ignition! The RL10B-2 engine, fed by liquid hydrogen and liquid oxygen, has been reignited to propel GPS 2F-5 into an intermediate orbit.

T+plus 17 minutes, 30 seconds. Delta velocity is 25,429 fps.

T+plus 17 minutes, 20 seconds. The vehicle is now in a coast mode before the next firing of the upper stage engine. Ignition of the RL10 engine is now four minutes away.

T+plus 16 minutes. Delta has flown into a good parking orbit.

T+plus 12 minutes, 25 seconds. SECO 1. The upper stage engine has shut down after the first of three planned firings to inject the GPS spacecraft into navigation network today.

T+plus 11 minutes, 15 seconds. First stage flight events occurred very close to planned times.

T+plus 11 minutes. Delta is 172 miles in altitude, 1,437 miles east of the launch pad.

T+plus 10 minutes. The vehicle's steep climb has leveled off as it gains speed toward orbital velocity.

T+plus 9 minutes, 15 seconds. The RL10 engine is burning a mixture of liquid oxygen and liquid hydrogen cryogenic propellants.

T+plus 8 minutes, 35 seconds. Delta is 162 miles in altitude, 1,001 miles east of the launch pad.

T+plus 8 minutes. Rock steady controls on the upper stage engine.

T+plus 7 minutes. Still looking good as Delta arcs over the Atlantic.

T+plus 6 minutes. Good engine control.

T+plus 4 minutes, 47 seconds. The protective payload fairing enclosing the GPS satellite atop the rocket has separated.

T+plus 4 minutes, 45 seconds. The cryogenic RL10B-2 upper stage engine has ignited!

T+plus 4 minutes, 35 seconds. The Common Booster Core first stage and the attached interstage have been separated in one piece from the Delta 4's upper stage. The upper stage engine's extendible nozzle is dropping into position.

T+plus 4 minutes, 10 seconds. MECO! Main engine cutoff confirmed as the RS-68 powerplant shuts down.

T+plus 4 minutes, 5 seconds. The main engine is throttling down to its minimum power setting in preparation for shutdown.

T+plus 3 minutes, 5 seconds. Passing Mach 10.

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

T+plus 2 minutes, 35 seconds. Passing Mach 5.

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

T+plus 1 minute, 44 seconds. Solid motor separation! The spent boosters have been shed from the first stage. Delta 4 continues powering its way toward space on the thrust generated by the RS-68 main engine.

T+plus 1 minute, 35 seconds. The twin 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 as the vehicle accelerates through the lower atmosphere.

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

T+plus 30 seconds. The Delta 4 rocket is climbing away from Cape Canaveral with its main engine firing at full throttle and the two strap-on boosters giving a powerful extra kick.

LIFTOFF! Liftoff of the 25th Delta 4 rocket as it 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 30 seconds. Green board. All systems remain "go" for launch.

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

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

T-minus 1 minute and counting. The ignition conditions for the RS-68 main engine are "go." Ignition of the RS-68 powerplant will follow at T-minus 5 seconds. The engine powers up to the 102 percent level of 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 10 minutes past the hour by the Delta 4 rocket carrying the GPS 2F-5 spacecraft from pad 37B at Cape Canaveral Air Force Station.

Permission to launch has been granted by the ULA launch 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 8:59 p.m. EST.

Again, solar radiation is now reported GO.

NEW LAUNCH TIME is set for 8:59 pm. EST. Solar radiation is green.

Tonight's window extends for 19 minutes and closes as 8:59 p.m.

The launch team is remaining postured.

HOLD EXTENDED due to solar radiation.

A load relief file based on the upper level winds is being transmitted to the Delta 4 rocket's flight computer. This program informs the rocket on the wind conditions it can expect to see during ascent.

Standing by for the launch team readiness check for continuing the countdown.

Solar activity is verified GO for launch.

Now 15 minutes to launch! The launch team will be polled in the next few minutes to confirm all systems are "go" to press onward for 8:40 p.m. liftoff.

The GPS 2F-5 spacecraft atop the Delta 4 is switching from ground-fed power to its internal batteries for launch.

Weather is observed GO and forecast GO for launch.

Launch minus 30 minutes.

The countdown is entering the final 45 minutes until the Delta 4 rocket launch from Cape Canaveral at 8:40 p.m. EST. Here's a look at some stats about today's mission. This will be:

• The 365th Delta rocket launch since 1960
• The 25th Delta 4 rocket mission since 2002
• The 10th Medium+ 4,2 configuration to fly
• The 39th main engine from RS-68 family used
• The 37th-38th GEM-60 solid rocket motors flown
• The 444th production RL10 engine to be launched
• The 28th RL10B-2 engine launched
• The 20th Delta 4 rocket launch from Cape Canaveral
• The 21st use of Delta 4 by the Air Force
• The 67th Evolved Expendable Launch Vehicle flight
• The 79th United Launch Alliance mission since 2006
• The 18th Delta 4 under the ULA banner
• The second ULA launch this year
• The first launch of the Delta family in 2014
• The 65th GPS satellite to launch
• The 53rd GPS launch on a Delta rocket
• The fifth GPS Block 2F satellite
• The fourth Block 2F launch on Delta /UL>
  0051 GMT (7:51 p.m. EST)

  T-minus 4 minutes and holding. The countdown has entered the planned 45-minute hold leading toward the 8:40 p.m. EST 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. A series of management polls will be conducted during the hold to give approval to proceed with the launch.

The ULA launch team and management are guiding the countdown from the Delta Operations Center, located about 9,200 feet from the pad. The engineers overseeing the rocket and ground systems are located on the third floor and the Mission Directors Center room is on the fourth floor. Both rooms have a view of pad 37B and the Delta 4 rocket out their windows. Other rooms are also set up for engineering support.

The DOC was formerly built to support the Titan-Centaur program but was refurbished to support Delta 4.

The launch team has completed the steering checks for the RS-68 main engine and RL10 upper stage engine, plus commanding tests with the solid rocket motors.

L-minus 90 minutes.

L-minus 115 minutes. Radio frequency link checks between tracking facilities at the Cape and the launch vehicle are being completed.

Now entering into the final two hours of the countdown to launch of Delta 365 and the fifth Block 2F satellite for the GPS constellation.

The rocket stands fueled and ready for launch at 8:40 p.m. EST today. The launch team is not reporting any significant issues, weather conditions are green and the countdown remains on schedule.

First stage fuel and oxider conditioning for flight is complete.

Uper stage fuel and oxider conditioning for flight is complete.

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!

Post-filling tests on the hydrogen side of the first stage are complete. The tank will be entering topping mode.

Loading of the upper stage liquid oxygen tank has been accomplished as fueling nears conclusion this afternoon at Complex 37.

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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.

Complex 37 has two giant sphere-shaped fuel tanks to store the cryogenic liquid oxygen and liquid hydrogen. The LOX tank holds 250,000 gallons and LH2 sphere about 850,000 gallons.

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 middle swing arm that extends from the Fixed Umbilical Tower to the front-side of the rocket.

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

Meanwhile, loading of the upper stage liquid hydrogen tank has been accomplished as fueling proceeds this afternoon at Complex 37.

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 wrapping up. 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.

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After chilldown of the upper stage liquid hydrogen system, the was clear 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.

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.

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.

With today's countdown going very smoothly, 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-68 main engine along with liquid oxygen during the first four minutes of the launch.

And fueling operations have begun. The hydrogen system's cold gas chilldown conditioning is underway.

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 Delta 4 rocket's RIFCA flight computer is powered up for flight and alignment is stable. And interrogation checks are being performed on the C-band beacon used for tracking the vehicle during its flight downrange.

T-minus 5 hours, 15 minutes and counting! The countdown has commenced for this evening's scheduled launch of the Delta 4 rocket to deliver a new GPS navigation satellite into orbit for the United States military and civil users.

The count has a planned built-in hold at T-minus 4 minutes, leading to liftoff at 8:40 p.m. EST (0140 GMT).

Technicians have finished all hands-on work at the launch pad and Complex 37 has been cleared of personnel in advance of fueling the rocket's two stages this afternoon. Pad systems and equipment stand ready for fueling activities, which should kick off shortly.

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

T-minus 5 hours, 15 minutes and holding. The countdown has entered a 15-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 Countdown for today's launch operation will begin.

Weather forecasters continue to predict an 80 percent chance of favorable conditions. Liftoff winds and solar weather at the time worries

Check out photos of the Delta 4 rocket during rollback of the launch pad's mobile gantry this morning.

The 330-foot tall mobile service tower has been retracted from the Delta 4 rocket at Cape Canaveral's pad 37B for tonight's launch that will place the GPS 2F-5 satellite into Earth orbit.

The wheeled structure just moved along rail tracks to its launch position about the length of a football field away from the rocket. The 9-million pound tower shielded the Delta from the elements during the its stay on the pad, provided workers 360-degree access to the various areas on the vehicle and was used to attach the strap-on solid motors and the payload during the launch campaign. The tower is 90-feet wide and 40-feet deep.

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 Delta 4's Common Booster Core first stage and the second stage with supercold liquid oxygen and liquid hydrogen propellants.

Testing of communications links between the rocket and Air Force Eastern Range will occur after fueling is accomplished. Steering checks of the first stage RS-68 engine and second stage RL10 powerplant are on tap in the last hour of the count.

A build-in hold is slated for T-minus 4 minutes, during which time teams will go through final polling to grant clearance to launch. The Delta 4 will transition to internal power as the count resumes, ordnance will be armed and the propellant tanks pressurized as clocks target the main engine ignition time at T-minus 5 seconds.

Liftoff remains scheduled for 8:40 p.m. EST, the opening of a 19-minute window that extends to 8:59 p.m. EST (0140-0159 GMT).

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Tower rollback has begun!

The fifth new-generation satellite for the Global Positioning System and its Delta 4 rocket booster have been cleared for blastoff into the navigation network Thursday from Cape Canaveral.

The GPS 2F-5 spacecraft is targeting an 8:40 p.m. EST launch from Complex 37. A 19-minute window extending to 8:59 p.m. EST will be available if conditions prevent an on-time liftoff.

Managers gathered this morning for the Launch Readiness Review that culminated with the consensus to proceed with picking up the countdown.

"The launch of new capabilities is a critical part of the modernization plan to improve operations, sustainment and overall GPS service," said Col. Bill Cooley, director of the Space and Missile Systems Center's Global Positioning Systems Directorate.

"Thanks to the phenomenal job by a team of dedicated, committed and professional individuals, we are ready to launch the next GPS 2F satellite," he said.

We will have complete live coverage of the count and launch on this page.

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Forecasters are predicting an 80 percent chance of favorable weather, with the concerns being cumulus clouds and solar activity.

"The associated high pressure ridge will move over Central Florida keeping winds light. Warm temperatures will cause an afternoon sea breeze, but conditions are dry and weather will remain favorable today during pre-launch operations," Air Force meteorologists say.

"On launch day, an upper-level ridge will build in and the surface high pressure ridge will move to the north causing breezy southeasterly flow, but not strong enough to cause concern for launch operations. Some cumulus clouds may develop along convergent bands moving in from offshore, but only low-level moisture is expected; therefore, this is not a significant concern for launch.

"As for solar activity, a geomagnetic event is in progress and proton flux levels are elevated but are well below the proton flux constraint for launch. A complex sunspot could cause a solar flare, and an X-Class flare would cause a proton flux concern. There is a 5% chance of an X-Class flare during the next 48 hours."

The launch time outlook includes just a few clouds at 3,000 feet, good visbility, southeasterly winds of 14 to 20 knots and a temperature around 69 degrees F.

The forecast for Friday's backup launch opportunity looks more unfavorable with a cold front moving into Florida and a 60 percent chance of good conditions.

Boeing developed a dozen Block 2F satellites to sustain and further upgrade the Global Positioning System for the U.S. Air Force. The first was launched in May 2010, the second went up in July 2011, the third in October 2012 and the fourth in May 2013 to replace aging craft in the constellation.

They feature improved accuracy, enhanced internal atomic clocks, better anti-jam resistance, a civil signal for commercial aviation, a longer design life and reprogrammable onboard processors to evolve with future needs.

"Since the inception of GPS, the Air Force has constantly strived to work with industry and other countries to develop newer and better ways to use GPS signals," said Cooley.

About three-and-a-half hours after liftoff Thursday, the Delta 4 rocket will deliver the satellite directly to the GPS constellation's altitude 11,047 nautical miles high.

The GPS 2F-5 spacecraft takes over the Plane A, Slot 3 location of the network, which is divided into six orbital groupings with multiple satellites flying in each.

The craft replaces the long-lived GPS 2A-28 satellite launched by a Delta 2 rocket from Cape Canaveral in 1997.

Going for its 25th flight, the United Launch Alliance Delta 4 rocket family will launch a new Global Positioning System navigation satellite from Cape Canaveral Thursday night.

Read our preview story.

The preliminary launch weather forecast issued this morning for Thursday's Delta 4 rocket flight calls for an 80 percent chance of favorable conditions due to clouds and solar activity that can upset vehicles' guidance systems.

"A high pressure ridge will be to the north on launch day causing southeasterly flow, and only low-level moisture is expected," forecasters reported this morning.

"As for solar activity, several sunspots could cause solar flares this week, and an X-Class flare could cause a proton flux concern. There is a five percent chance of an X-Class flare for the next 48 hours, and solar activity will be monitored and updated as we approach launch day."

The launch time forecast calls for a few low clouds, good visibility, southeasterly winds of 12 to 16 knots and a temperature of 70 degrees.

"Weather remains favorable for a 24-hour delay, and degrades if there is a 48-hour delay due to a cold front expected in the area," forecasters say.

The final reviews are underway ahead of next week's Delta 4 rocket launch carrying a replacement satellite for the Global Positioning System.

Liftoff is planned for Thursday night at 8:40 p.m. EST.

Built by Boeing, the new satellite will become a modernized member of the orbiting GPS constellation. It features greater accuracy, better anti-jam characteristics and a new civilan signal for commercial aviation.

The satellite will replace one launched in 1997.

At launch complex 37 last week, the payload was attached to the rocket and the integrated checks were successfully completed. Earlier this week, the attitude control system hydrazine fuel was loaded aboard the second stage. Now, activities to close out the vehicle compartments for flight are in work.

The Flight Readiness Review has been completed. Upcoming next week are the System Certification Review in which engineers report out their systems for the mission and the Launch Readiness Review occurs to grant approval to enter the countdown.

The mobile service gantry will be retracted Thursday at 10:45 a.m. and the count picks up at 3 p.m. EST.

For more information about the launch, see our special Info Sheet.

Beginning a slate of three launches in five months to fortify the Global Positioning System, the first craft was mounted atop its Delta 4 booster rocket Wednesday for liftoff Feb. 20.

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The next launch of a Global Positioning System satellite is back on track after engineers gained fresh insight into the circumstances surrounding a previous GPS flight and its low-thrust condition on the upper stage.

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United Launch Alliance has postponed the next launch of a Delta 4 rocket from Oct. 23 to sort out the significance of fresh conclusions stemming from an investigation into an RL10 engine anomaly during another Delta 4 launch one year ago, the company said in a statement Friday.

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The launch of a new satellite to replenish the U.S. Air Force's GPS navigation network, previously scheduled to lift off Oct. 23 on a United Launch Alliance Delta 4 rocket, has been postponed, according to Air Force officials.

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