A new Air Force satellite headed for service over the Middle East to route essential communications to U.S. military forces and improve data links to unmanned aerial drones was successfully launched from Cape Canaveral last night.

Read our full story.

A dazzling gallery of launch photos is posted here.

Some not-so-great images from our other launch pad camera whose lens was covered in dew.

The Wideband Global SATCOM 4 spacecraft is alive and well following its launch into space. Controllers confirmed initial contact with the spacecraft at 8:36 p.m. EST via a ground station in Dongara, Australia.

"WGS 4 continues Boeing's commitment of supporting the Air Force's mission of delivering critical communications to warfighters," said Craig Cooning, vice president and general manager of Boeing Space & Intelligence Systems. "The company will remain focused, committed and dedicated to this mission as we continue to build the WGS series of satellites."

Spaceflight Now's camera at the Complex 37 pond captured these blastoff shots.

The next Delta 4 rocket launch is targeted for March 29 from Vandenberg Air Force Base in California on the classified NROL-25 satellite-deployment mission for the National Reconnaissance Office. That's the government agency responsible for operating the country's fleet for spy satellites.

The next one from the Cape will be a Heavy vehicle with NROL-15 in June.

Here's a post-flight statement from Jim Sponnick, United Launch Alliance vice president of mission operations:

"We are honored to have worked closely with our Air Force and mission partners to enable today's successful launch of the WGS 4 satellite. WGS 4 will provide important capabilities to the soldiers, sailors, airmen and marines protecting our freedoms around the world," he said. "This mission begins the most aggressive launch campaign in the history of the EELV program, with nine national security and two NASA launches scheduled this year."

T+plus 40 minutes, 50 seconds. SPACECRAFT SEPARATION! The Air Force's Wideband Global SATCOM 4 military communications satellite has been deployed into orbit from the Delta 4 rocket's upper stage, completing tonight's launch.

The spacecraft will spend the next few weeks being maneuvered into geostationary orbit by controllers at Boeing's satellite facility in El Segundo, California. The orbit raising activities will use both the conventional propellant engines as well as ion propulsion thrusters.

Boeing will oversee the craft's solar array and antenna deployments, plus complete an initial round of testing before WGS 4 is handed over to the Air Force by the end of April. The military plans to conduct its own set of checks and verifications, then position the craft at its orbital slot over the Indian Ocean to enter service this summer.

T+plus 39 minutes, 15 seconds. Separation will occur while soaring away from the planet over Madagascar and the Indian Ocean. The vehicle is passing over that giant island now.

T+plus 38 minutes, 45 seconds. About two minutes from separation.

T+plus 37 minutes. Delta 920 miles in altitude, traveling at 30,878 feet per second, some 7,364 miles downrange from the launch pad.

T+plus 36 minutes, 15 seconds. The rocket is coasting in orbit and will soon deploy the next Wideband Global SATCOM, continuing the modernization effort for the U.S. military's satellite communications network in space.

T+plus 35 minutes, 45 seconds. Release of the payload about 5 minutes away.

T+plus 34 minutes. The Delta 4 rocket has successfully reached its targeted supersynchronous transfer orbit with a perigee of 237 nautical miles and apogee of 36,200 nautical miles with an inclination of 24.00 degrees.

T+plus 32 minutes, 45 seconds. The vehicle has re-positioning itself to the proper orientation for spacecraft separation,

T+plus 31 minutes, 39 seconds. SECO 2. The second of two firings by the upper stage during today's launch has been completed, ending the powered phase of flight.

T+plus 31 minutes. The vehicle has crossed the coastline of Africa.

T+plus 30 minutes, 30 seconds. This burn injects the rocket into a highly elliptical orbit stretching about 36,000 nautical miles in altitude at its furthest point from Earth.

T+plus 30 minutes into the flight. Altitude 350 miles as the engine performs well.

T+plus 29 minutes, 30 seconds. Pitch and yaw control are normal.

T+plus 29 minutes, 20 seconds. This burn will last just over three minutes in duration.

T+plus 28 minutes, 40 seconds. Good engine chamber pressure reported.

T+plus 28 minutes, 33 seconds. The RL10B-2 engine, fed by liquid hydrogen and liquid oxygen, has been ignited once again! This firing will propel WGS 4 to its targeted orbit.

T+plus 26 minutes, 50 seconds. Passing an altitude of 200 miles as the rocket begins to climb upwards again on its trajectory.

T+plus 25 minutes, 45 seconds. The vehicle is now in a coast mode before the next firing of the upper stage engine. Re-ignition of the RL10 engine is three minutes away.

T+plus 24 minutes. To see the track the rocket is following this evening, click here.

T+plus 23 minutes. The upper stage is reorienting to the proper position for the next burn.

T+plus 22 minutes. The Delta 4 rocket has successfully reached its targeted orbit with a perigee of 100 nautical miles and apogee of 3,715 nautical miles with an inclination of 25.59 degrees.

T+plus 20 minutes, 44 seconds. SECO 1. Confirmation that the second stage engine has shut down after the first of two planned firings to inject the WGS 4 spacecraft into a supersynchronous transfer orbit.

T+plus 19 minutes, 57 seconds. Delta is 3,058 miles down range.

T+plus 19 minutes, 30 seconds. Normal chamber pressures and good pitch and yaw steering reported.

T+plus 19 minutes, 10 seconds. Delta is traveling at 27,406 feet per second over the central Atlantic Ocean.

T+plus 18 minutes. The upper stage's the RL10 engine working well, still firing as planned to reach the parking orbit this evening.

T+plus 17 minutes, 45 seconds. Delta is traveling at 25,508 feet per second, 2,503 miles downrange from the launch pad.

T+plus 17 minutes, 30 seconds. This burn will place the vehicle into an initial parking orbit around Earth. The rocket is headed for an elliptical orbit of approximately 100 by about 3,700 nautical miles with an inclination of 25.6 degrees.

T+plus 17 minutes. The upper stage is stable and giving WGS 4 a good ride.

T+plus 16 minutes, 40 seconds. About four minutes remain in this firing of the second stage.

T+plus 15 minutes, 40 seconds. The telemtry relay duties are being from ground stations to NASA's Tracking and Data Relay Satellite System.

T+plus 14 minutes, 50 seconds. Delta speed now 22,325 feet per second, more than 1,896 miles downrange from the launch pad.

T+plus 14 minutes, 30 seconds. The RL10 engine is burning a mixture of liquid oxygen and liquid hydrogen cryogenic propellants. Chamber pressures still look good.

T+plus 13 minutes, 55 seconds. Delta is 199 miles in altitude, 1,723 miles east of the launch pad.

T+plus 13 minutes. Delta is 210 miles in altitude, speeding along at 20,697 feet per second, more than 1,560 miles downrange from the launch pad.

T+plus 12 minutes. Delta is speeding along at 19,724 feet per second, more than 1,300 miles downrange from the launch pad.

T+plus 11 minutes, 30 seconds. The vehicle's steep climb leveled off as it gains speed toward orbital velocity.

T+plus 10 minutes, 50 seconds. Good controls by the upper stage. Delta is 226 miles in altitude, speed in excess of 18,000 feet per second, 1,150 miles downrange from the launch pad.

T+plus 9 minutes, 50 seconds. The second stage engine continues to fire well with good chamber pressure. All is looking good.

T+plus 9 minutes. The upper stage is the larger five-meter version that has flown previously on the Delta 4-Heavy vehicle and the earlier WGS 3 mission. It is an element that distinguishes this Medium+ (5,4) rocket configuration from other variants use four-meter upper stages for lower-weight payloads.

Today's stage has a wider liquid hydrogen tank and a lengthened liquid oxygen tank to carry additional propellants, enabling the RL10 engine to fire longer and carry heftier cargos.

T+plus 8 minutes, 25 seconds. Mission event times are occurring at the expected time.

T+plus 7 minutes, 50 seconds. Now above 200 miles.

T+plus 7 minutes, 20 seconds. Delta is 193 miles in altitude, 17,000 feet per second in velocity, 635 miles east of the launch pad.

T+plus 6 minutes, 20 seconds. Good chamber pressure data being reported from the RL10 engine as it thrusts to reach orbit.

T+plus 6 minutes. Delta is 161 miles in altitude, 462 miles east of the launch pad.

T+plus 5 minutes, 15 seconds. Delta is 134 miles in altitude, traveling at 16,483 feet per second, 350 miles east of the launch pad.

T+plus 4 minutes, 31 seconds. The cryogenic RL10B-2 upper stage engine has been lit!

T+plus 4 minutes, 18 seconds. The Common Booster Core first stage and the attached interstage have been separated in one piece. The upper stage engine's extendible nozzle is dropping into position to prepare for ignition.

T+plus 4 minutes, 10 seconds. MECO! Main engine cutoff confirmed as the RS-68 shuts down, completing its 28th successful use in powering the Delta 4 program.

T+plus 3 minutes, 57 seconds. The main engine is throttling down to 57 percent thrust for the rest of its firing in today's launch.

T+plus 3 minutes, 31 seconds. Now above the discernible atmosphere, the protective nose cone enclosing the WGS 4 satellite atop the rocket has jettisoned.

T+plus 3 minutes. Delta is 61 miles in altitude.

T+plus 2 minutes, 50 seconds. Delta is 46 miles in altitude, 75 miles downrange from the launch pad.

T+plus 2 minutes, 30 seconds. The main engine continues to burn, consuming its liquid hydrogen and liquid oxygen propellants.

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

T+plus 1 minute, 55 seconds. Now weighs half of what it at liftoff.

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 on the thrust generated by the RS-68 main engine.

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

T+plus 60 seconds. Rocket is over 7 miles in altitude already.

T+plus 50 seconds. Now passing through the region of maximum aerodynamic pressure.

T+plus 36 seconds. The launcher has broken through the sound barrier.

T+plus 20 seconds. The Delta 4 rocket is thundering away from the spaceport with its main engine firing at full throttle and the four strap-on motors giving an impressive boost in speed.

LIFTOFF! Liftoff of Delta 4 with WGS 4, enhancing military communications for the warfighter. And the vehicle has cleared 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 1 minute and counting. The ignition conditions for the RS-68 main engine are "go." The terminal countdown sequencer will take control at T-minus 8.5 seconds. Ignition of the RS-68 powerplant will follow at T-minus 5.5 seconds. The engine powers up to the 102 percent level of thrust for a computer-controlled checkout before liftoff.

T-minus 70 seconds. The Air Force-controlled Eastern Range has given its "go" for launch.

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, 27 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 38 minutes past the hour by the Delta 4 rocket carrying the Wideband Global SATCOM 4 spacecraft from pad 37B at Cape Canaveral Air Force Station.

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

The final readiness polls have been completed and all team members voiced "ready" status for continuing the countdown for launch at 7:38 p.m. EST.

Ten minutes to launch!

The launch team will be polled in the next few minutes to confirm all systems are "go" to press onward for 7:38 p.m. EST liftoff.

All continues to look good for an on-time launch. No problems are being reported from ULA.

Unlike all the previous Delta 4 missions that employed a hold at T-minus 5 minutes, tonight's mission actually stopped the clock at T-minus 4 minutes.

T-minus 4 minutes and holding. The countdown has entered the planned 15-minute hold leading toward the 7:38 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 final guidance update on upper level winds is being loaded into the rocket.

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

Thirty minutes!

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The ULA launch team and the mission management group 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.

A final full-up briefing from the launch weather officer to mission managers just occurred. Skies remain crystal clear with good visibility, winds have decreased to 5 knots but have remained northerly and didn't switched around to the more-easterly direction as had been expected. But the weather is green across the board.

T-minus 25 minutes and counting. The countdown is headed to the T-minus 4 minute point where a 15-minute hold is planned. Liftoff is targeted for 7:38 p.m., the opening of today's 93-minute launch window.

The engine slew checks have been performed successfully. The test sequence started with the upper stage RL10 engine, followed by the first stage RS-68 engine gimbaling and then some commanding checks for the strap-on solid rocket motors.

Now moving into the final 45 minutes of the countdown.

This launch will deliver to orbit the fourth satellite in the Wideband Global SATCOM series and begins the new Block 2 series with improved bandwidth for relaying communications with unmanned aerial drones. The Boeing Company builds the craft for the U.S. Air Force.

"This launch will be another important step in advancing communications capabilities for U.S. warfighters and allies around the world," said Craig Cooning, vice president and general manager of Boeing Space & Intelligence Systems. "When it enters service, WGS 4 will join three other WGS satellites that deliver critical communications to help warfighters execute missions with greater safety and efficiency."

Boeing shipped the WGS 3 satellite from its factory in El Segundo to Cape Canaveral on Nov. 15. Over the past two months, the craft underwent final testing, fueling and encapsulation in the shroud that will cover it during launch.

On Jan. 4, the spacecraft was transported from the Astrotech processing facility in Titusville to Complex 37 where it was hoisted atop the Delta 4 rocket.

The company has five additional WGS satellites in production for more launches starting next January through 2017.

"WGS is the DOD's highest capacity communications satellite system. These satellites provide tremendous operational flexibility to deliver the needed capacity, coverage and connectivity in support of demanding operational scenarios," said Mark Spiwak, the WGS program director at Boeing.

The propellant topping has been completed on all four cryogenic tanks. The Delta 4 rocket is fueled up and ready for today's launch window to open.

The external inspections of the Delta 4 rocket's thermal insulation following fueling have been completed without any problems seen.

Proper flight conditioning of the upper stage liquid hydrogen supply has been achieved.

The rocket team is not tracking any technical issues of note, the weather is fine and upper level wind conditions are acceptable.

Weather remains 100 percent acceptable during the launch window tonight. The revised forecast now includes clear skies, visibility of 10 miles, due-north winds of 5 peaking to 8 knots and a temperature around 60 degrees F.

The countdown is entering the final 60 minutes until the Delta 4 rocket launch from Cape Canaveral at 7:38 p.m. EST. Here's a look at some stats about today's mission. This will be:

• The 358th Delta rocket launch since 1960
• The 18th Delta 4 rocket mission since 2002
• The 15th Delta 4 rocket launch from Cape Canaveral
• The 14th use of Delta 4 by the Air Force
• The second Medium+ 5,4 configuration to fly
• The first launch of the Delta family in 2012
• The 57th United Launch Alliance mission since 2006
• The 11st Delta 4 under the ULA banner
• The 4th Wideband Global SATCOM satellite
• The first Block 2 WGS satellite
• The second WGS on Delta 4

The link checks were verified satisfactory. Flight slews of the engines is next in the countdown.

The RS-68 first stage main engine spin start pressurization operation is about to start.

With the safety system testing conducted satisfactorily, the radio frequency link checks between the rocket and ground now are beginning as the next portion of countdown operations progresses.

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

Proper flight conditioning of the first stage liquid hydrogen supply has been achieved.

Pre-launch checks of the Delta 4 rocket's safety system are being performed at this point in the countdown.

Upper stage liquid oxygen topping has commenced. That puts all four cryogenic fuel tanks aboard the Delta 4 rocket in topping mode.

The launch team is entering the last 90 minutes of the countdown. With fueling of the Delta 4 rocket completed, team members are monitoring systems while the clocks tick down.

In the immediate future, the rocket's safety system will be checked and a series of engine steering tests will occur.

Everything continues to proceed on schedule at Cape Canaveral for liftoff at 7:38 p.m. EST.

Nine national security spacecraft ranging from spy platforms to navigation birds, communications satellites and weather observatories have been entrusted to Atlas 5 and Delta 4 rockets in a $1.5 billion booster purchase through the Air Force's Evolved Expendable Launch Vehicle program, the Defense Department announced last week.

Read our full story on the big purchase and the missions the boosters will fly.

The upper stage liquid oxygen tank has been filled up, now making the Delta 4 a fully fueled rocket for launch at 7:38 p.m. EST (0038 GMT) tonight.

The upper stage liquid hydrogen post-filling checks have been conducted, allowing the tank to be placed into topping mode.

Proper flight conditioning of the first stage liquid oxygen supply has been achieved.

The pre-flight check for Collision Avoidance cutouts of the launch window, known as COLAs, to ensure the rocket is not sent on a path at a certain liftoff time that would take the vehicle too close to another object already in space shows a couple of blackout zones in the launch window tonight. The first is just a one-minute COLA at 7:59 p.m. EST. The other is a much longer cutout from 8:18 to 8:51 p.m.

Tonight's overall launch window runs from 7:38 to 9:11 p.m. EST.

Now entering the last two hours of the countdown. Fueling of the Delta 4 rocket continues nears completion for the 7:38 p.m. EST launch of the Defense Department's WGS 4 military communications satellite from Cape Canaveral, Florida.

With about two hours until launch time, HH-60G Pave Hawk helicopter crews from the 920th Rescue Wing will take off from Patrick Air Force Base to sweep the hazard area for tonight's liftoff.

They will clear mariners from a 60-mile stretch of the Air Force-controlled Eastern Range over the Atlantic Ocean to keep them out of harm's way beneath the rocket launch path.

As a combat-search-and-rescue unit, the Airmen are trained to provide search and rescue services in humanitarian and combat environments. Supporting launches is part of their mission.

Post-fueling venting and valve checks have been completed on the first stage liquid hydrogen tank and its topping phase is being set up for the remainder of the countdown.

The weather forecast has improved to a 100 percent chance of acceptable conditions tonight. The updated outlook for launch time now includes clear skies, visibility of 10 miles, east-northeasterly winds of 5 peaking to 8 knots and a temperature around 60 degrees F.

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.)

A status check of the fueling activities shows the fast-fill loading to the upper stage liquid hydrogen tank just ended. The launch team continues to load the liquid oxygen supply to the stage.

Post-filling tests on the first stage liquid oxygen system are complete and the tank is being put into a stable topping mode.

The upper stage conditioning on the liquid oxygen side has finished, so loading of the tank with 4,500 gallons is starting. This is the last of the rocket's four cryogenic supplies to be filled in today's countdown to launch.

The launch team is actively loading the upper stage's liquid hydrogen tank with 10,000 gallons of propellant for the RL10 engine.

Three hours and counting!

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

The loading of liquid oxygen into the Common Booster Core first stage has been completed. The launch team will conduct vent and valve checks before putting the tank into topping mode for the rest of the countdown.

The chilldown of the upper stage stage liquid hydrogen system is reported complete, clearing the way for loading the rocket's tank.

Fast-fill just finished for the first stage liquid hydrogen tank and technicians are establishing topping mode for the supercold propellant.

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. 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 will be filled in a little while. It receives the cryos from the middle swing arm that extends from the Fixed Umbilical Tower to the front-side of the rocket.

Now four hours from launch.

First stage liquid oxygen loading continues in progress. The rocket's tank will be loaded with 40,000 gallons of the supercold oxidizer that's chilled to Minus-298 degrees F.

The launch team has gotten the approval to start chilldown conditioning of the upper stage liquid hydrogen system.

Check out these beautiful photos taken this morning as the mobile service gantry was rolled away from the Delta 4 rocket.

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

First stage liquid hydrogen tanking operation is switching from "slow-fill" to "fast-fill" mode. Some 110,000 gallons of LH2 will load up the rocket's tank.

Confirmation has been made by the launch team that the LOX chilldown operations for the first stage have begun.

"Go" for chilldown of the first stage liquid oxygen system. This preps the tank and pumping to guard against shock when the supercold oxidizer begins flowing into the rocket a short time from now.

The first stage liquid hydrogen loading in "slow-fill" mode has commenced.

The cold gas chilldown conditioning of the liquid hydrogen system has been accomplished. Liquid hydrogen propellant will start 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.

Now entering the final five hours until liftoff time. No significant technical issues are being tracked and the launch team is active with the thermal conditioning of the first stage for fueling.

And chilldown has begun.

A "go" has been given to start the cold gas chilldown conditioning of the first stage liquid hydrogen system.

The launch director has given approval for the start of fueling operations.

Purging preps before fueling are complete on the first stage and now beginning on the second stage.

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

The countdown has one planned built-in hold at T-minus 5 minutes lasting some 15 minutes, leading to liftoff at 7:38 p.m. EST (0038 GMT).

The launch pad has been verified evacuated of all 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.

No technical problems are being reported in the countdown. The launch pad has been buttoned up and the area cleared for the rest of the day.

The team recently completed activation of the rocket's avionics and performed checks of the C-band tracking beacon.

The launch team has been polled to verify all consoles are manned and ready to begin the Terminal Countdown when this hold ends at 2:08 p.m. A briefing on countdown procedures also occurred as the team gets set to press ahead on schedule today.

Florida is a "cloud-free state" today as the weather looks just fine for launch, Air Force meteorologists have reported during a briefing mission managers in advance of giving approval to start fueling the Delta 4.

The revised forecast for this evening's window calls for clear skies, visibility of 10 miles, east-northeasterly winds of 8 peaking to 12 knots and a temperature around 60 degrees F.

The call to "man stations" just went out to the launch team in preparation for Terminal Count and cryogenic fueling operations.

Meanwhile, checks of the C-band beacon are beginning. This system is used in tracking the rocket during the flight downrange.

T-minus 5 hours, 15 minutes and holding. The countdown has just entered a planned 60-minute built-in hold, giving the team a block of time to catch up on any work that could be running behind schedule. Once the clocks resume ticking at 2:08 p.m. EST, the Terminal Countdown phase of today's launch operation will begin.

Our gallery of photographs taken at the Complex 37 launch pad this morning when the mobile service gantry was retracted to unveil the Delta 4 rocket is posted here.

The skies are clear and crisp as the weather looks perfect for launching the Delta 4 rocket tonight. The outlook for the liftoff time still predicts a 95 percent chance of acceptable conditions.

"Cold front moved through late yesterday. Surface high pressure will build in and settle across central Florida providing favorable conditions today. Winds this morning will be northwest at the 10-15 knots and will gradually decrease during the countdown while shifting to the east-northeast by this afternoon and evening," the Air Force weather team says.

"Ground winds will continue to be the only area of slight concern during the countdown and launch window. A few marine stratocumulus clouds could move onshore during the day but will not be a concern. Winds aloft will generally be westerly with maximum speeds approaching 100 knots with no areas of significant shear anticipated."

During this evening's window, the forecast calls for a few low clouds, east-northeasterly winds of 8 peaking to 12 knots and a temperature around 60 degrees F.

In the event of a 24-hour delay to Friday, the odds of good weather are 90 percent favorable, then 80 percent "go" on Saturday.

The 330-foot tall mobile service tower has been retracted from the Delta 4 rocket at Cape Canaveral's pad 37B for today's launch that will place the fourth Wideband Global SATCOM military satellite into Earth orbit.

The wheeled structure was 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 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 vehicle later this afternoon.

Liftoff remains scheduled for 7:38 p.m. EST, the opening of a 93-minute window that runs through 9:11 p.m. EST (0038-0211 GMT) to get the rocket airborne tonight.

Tower rollback is underway to reveal the 217-foot-tall Delta 4 rocket for flight.

Good morning from the Cape Canaveral Air Force Station where launch day has dawned for the year's first rocket flight. And it's a big one for the Defense Department -- a Delta 4 rocket carrying a vital communications-relay satellite for deployed forces in the Middle East.

Out at Complex 37, ground technicians are making final preps to retract the dual-purpose assembly gantry and mobile shelter away from the United Launch Alliance-made rocket for today's countdown to blastoff.

Photographers are gathering right now to enter the launch pad and set up their sound-activated cameras to capture tonight's liftoff. We'll also grab some pre-launch shots while we're out there to post a little later this morning

We'll be out of communication once we head into the complex. So we'll resume with updates and confirmation of tower rollback as soon as possible.

And also watch our Facebook page for mobile photos!

On the eve of flight, the Delta 4 rocket and the Wideband Global SATCOM 4 military communications satellite passed their Launch Readiness Review and received clearance for blastoff Thursday night from Cape Canaveral's Complex 37.

"There's hundreds of people on the satellite and launch teams that have been hard at work to ensure a successful launch and mission," said Col. Ron Fortson, the Air Force's mission director for the launch. "A tremendous amount of work has been accomplished."

Now comes the culmination of all that labor and effort. Thursday's 93-minute launch opportunity extends from 7:38 to 9:11 p.m. EST (0038-0211 GMT).

Launch day activities will begin with final preparations for retracting the 330-foot mobile service tower away from the Delta 4 vehicle early in the morning. The gantry, which should be finished rolling back by 10 a.m. EST, was used to install the strap-on solid-fuel motors and the satellite payload during pre-flight work, plus served as a protective structure to shield the booster from adverse weather conditions during its stay at the pad.

A key weather briefing occurs a little after 1:30 p.m. EST as the launch team decides whether to commit to the fueling process. The weather officer will give managers the latest information about the kind of conditions that the rocket could face during the afternoon hours while it sits exposed during the propellant loading.

Assuming the weather is deemed favorable to proceed, the Terminal Countdown will begin ticking at 2:08 p.m. EST, leading to the multi-hour process of filling 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 15-minute build-in hold is slated for T-minus 5 minutes, during which teams will go through final polling to grant the official authority 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 5.5 seconds.

The launch weather officer now projects a 95 percent chance that conditions will be acceptable for a Thursday evening liftoff. Ground winds pose only a tiny concern.

"Cold front and scattered showers will move into east central late this afternoon and evening. Afterwards high pressure will build in and settle across central Florida and provide favorable conditions on Thursday," Air Force meteorologists report.

"Latest guidance now does not indicate windy conditions after the front passes as winds will be in the 10-15 knot range while decreasing during the countdown. Ground winds will continue to be the only area of slight concern during the countdown and launch window. A few marine stratocumulus clouds will move onshore during the day but will not be a concern. Winds aloft will generally be west-northwesterly with maximum speeds around 70-80 kt with no areas of significant shear anticipated."

The specifics at launch time include a few clouds at 3,000 feet, easterly winds of 8 peaking to 12 knots and a temperature of 60 degrees F.

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After nearly five years of construction and testing, the U.S. military's next satellite with voluminous throughput to pump vital communications to battlefield forces awaits blastoff Thursday night from Cape Canaveral. The $464 million Wideband Global SATCOM 4 spacecraft will ride a Delta 4 rocket off the pad at 7:38 p.m. EST (0038 GMT).

Read our full story.

Meteorologists' outlook for the Thursday night weather is unchanged in predicting a 90 percent chance of launching, says the latest forecast issued this morning.

They have slightly decreased the wind speeds, however, in calling for just a few clouds at 3,000 feet, northeasterly winds of 8 peaking to 12 knots and a temperature of 58 degrees F.

Out at Complex 37, technicians have begun retracting the swinging access platforms on the mobile service tower and gotten the flame deflector moved into position in front of the pad's launch table. The Launch Readiness Review is planned for Wednesday.

Thursday evening is looking like a pretty nice night to launch a rocket from Florida's spaceport, according the early weather outlook issued by Air Force meteorologists this morning.

Liftoff of the Delta 4 rocket carrying a U.S. military communications satellite from Complex 37 will be possible during a 93-minute window extending from 7:38 to 9:11 p.m. EST (0038-0211 GMT).

The launch weather team predicts a 90 percent chance that conditions will permit the rocket to soar on its nighttime climb to orbit as planned, with only a slight chance for ground winds calling a hold in the countdown.

"The main weather feature over the next few days will be a cold front that will pass through the area Wednesday afternoon and evening. This front will bring a chance for showers on Wednesday. Afterwards high pressure will build in and provide favorable conditions on Thursday," forecasters report.

"Post-frontal north-northeast winds on Thursday morning will still be breezy but are expected to gradually decrease and become more east-northeast throughout the day and not be a major concern during the countdown and launch window. A few marine stratocumulus clouds will move onshore during the day but will not be a concern. Winds aloft will generally be west-northwest with maximum speeds around 70-80 knots and no areas of significant shear anticipated."

The launch window outlook includes a few low-level clouds, northeasterly winds of 10 peaking to 15 knots and a temperature of 58 degrees F.

The odds for favorable weather on Friday evening, should the launch be delayed 24 hours, are 80 percent due to only cumulus cloud and ground wind worries. Similar conditions and odds are predicted on Saturday evening, too.

When the rocket does fly, it will deliver into a supersynchronous transfer orbit the Air Force's fourth Wideband Global SATCOM spacecraft, a powerful communications satellite that will be parked over the Indian Ocean to cover the Middle East and Southwest Asia.

Check back tomorrow for a mission preview and watch this page for live coverage throughout the countdown and launch!

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 combined Delta 4 rocket and its Wideband Global SATCOM 4 spacecraft payload have successfully completed a thorough electrical test that simulated the countdown and booster's trek into a supersynchronous orbit in preparation for the real blastoff next week.

The craft was delivered to Cape Canaveral's pad 37B and mounted atop the United Launch Alliance-made rocket last Tuesday. The Integrated Systems Test then followed to verify the booster and cargo were in proper sync for flight.

"We completed our Integrated Systems Test this past weekend, which is an end-to-end simulation of the rocket as if it was in flight, and exercised the whole system as well as some of the interfaces with the satellite. That was a major activity we just completed (and) that was the most significant task remaining," said Col. Ron Fortson, the Air Force's mission director for the launch.

Now, technicians are moving into the last round of preps needed to ready the Delta and launch pad facility infrastructure for liftoff next Thursday, Jan. 19.

"All in all, it's a very typical set of final-week-before-launch connections, closeouts and subsystem testing," said Jim Sponnick, United Launch Alliance vice president of mission operations.

Loading of propellant into the vehicle's attitude control system was underway Tuesday, and upcoming activities include final ordnance connections, closing out the compartments up and down the rocket and a handful of subsystem tests planned for early next week.

Built by The Boeing Co. in California, WGS 4 was delivered to the Florida spaceport aboard an Air Force transport aircraft on Nov. 15. It spent about six weeks at the Astrotech payload processing facility in Titusville getting loaded with nearly 4,700 pounds of fuel and oxidizer maneuvering propellant, a hazardous operation completed on Dec. 5, then being encapsulated into the two-piece rocket nose cone on Dec. 15.

"We have gone through our prelaunch operations, all have occurred nominally," said Dave Madden, director of the Military Satellite Communications Systems Directorate at the Air Force's Space and Missile Systems Center.

Transport to the launch pad took place on Jan. 4 to join the spacecraft with its ride to space.

"It is sitting there, ready for launch," Madden told reporters in a pre-flight media briefing Tuesday.

The satellite should become operational over the Indian Ocean this summer, providing enhanced communications services to deployed military forces in the Middle East and surrounding areas.

Heaving the craft aloft will look much the same as the previous WGS 3 mission in December 2009 that also used a Delta 4 rocket.

"It is the same configuration vehicle and essentially flying the same sort of mission profile as well," Sponnick said.

"We are ready to launch WGS 4."

Watch this page for continuing updates on the launch and join us for play-by-play reports throughout the countdown and live streaming video of the flight on Jan. 19.

Moving from the cleanroom to the Cape Canaveral launching pad, the next update to the U.S. military's space-based communications network was hoisted aboard its booster rocket today.

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In the pitch black darkness on this bitterly cold morning in Central Florida, the payload-delivery convoy has made its way from the Astrotech satellite processing facility in Titusville over to Cape Canaveral Air Force Station's Complex 37. The WGS 4 spacecraft just arrived at pad 37B for today's hoisting atop the Delta 4 rocket in preparation for blastoff just 15 days from now.

Check back later today for a full story.

A spacecraft that will improve communications with the U.S. military's aerial drones currently employed in some of the world's hotspots has arrived at Cape Canaveral to prepare for blastoff in January.

The Air Force says it plans to put this WGS 4 spacecraft into operation over the Middle East and Southeast Asia for U.S. Central Command and U.S. Pacific Command when it becomes operational early next year.

Read our full story.

The United Launch Alliance Delta 4 rocket that will deploy a vital communications satellite for U.S. military forces overseas was placed atop its Cape Canaveral pad this week.

Liftoff is targeted for January 19 to deliver the Air Force's fourth Wideband Global SATCOM spacecraft into orbit and continue ongoing efforts to upgrade the military's main communications infrastructure.

Read our full story.

And check out our rollout photo collection.