The Delta 4 rocket's cryogenic upper stage persevered through a fuel leak and the resulting low-thrust condition by autonomously engaging techniques that kept the mission on track to successfully launch a Global Positioning System satellite in October.

Read our full story.

Generating less than its normal 25,000 pounds of thrust because of a still unknown problem, the upper stage engine on the Delta 4 rocket had to fire for longer periods of time Thursday morning before ultimately delivering the GPS payload into the right orbit, overcoming the adversity to achieve success.

Read our full story.

See the launch pad photo collection.

Upgrading the Global Positioning System one launch at a time, a modern bird soared to space Thursday to replace a long-surviving navigation satellite deployed 19 years ago, a durable craft of the past that doubled life's expectations and will give way to current advancements.

Read our full story.

And see our launch photo gallery.

"Congratulations to the entire team on today's successful launch of the GPS 2F-3 satellite," Jim Sponnick, ULA vice president, Mission Operations, said in the post-launch press release.

"ULA and our mission partners have a rich heritage with the GPS program and we are proud to have served alongside the government and contractor teams over the last two decades to provide important Global Positioning System capabilities for our national defense and for millions of civilian and commercial users around the world."

Officials report spacecraft separation of GPS 2F-3 from the Delta 4 rocket. Now awaiting the various post-launch releases from ULA, the Air Force and satellite-builder Boeing.

We are still waiting on official information to pass along about the ultimate outcome of the launch and health of the GPS 2F-3 satellite.

Now four minutes after the expected spacecraft deployment time. Still awaiting on word.

The third and final burn by the Delta 4 rocket's cryogenic upper stage should have just occurred. However, we have no word at this time on how the mission is progressing.

The rest of the flight will be occurring in the quiet. We will post confirmation of spacecraft deployment and any other information about the flight as details become available this morning.

Per the schedule, the upper stage will ignite again at 11:30 a.m. EDT for a 99-second circularization burn that puts GPS 2F-3 into am 11,047 nautical mile orbit inclined 55 degrees. Release of the satellite to complete the launch occurs at 11:43 a.m. EDT.

T+plus 2 hours. Unlike the previous generations that rode on smaller rocket Delta 2 rockets, the dozen next-generation GPS 2F craft will be delivered into orbit atop the Delta 4 and Atlas 5 fleets of boosters in the Air Force's Evolved Expendable Launch Vehicle program.

The Delta 2's, although highly reliable, weren't powerful enough to inject the GPS satellites directly into the orbiting constellation. The three-stage vehicles released the craft into a highly elliptical orbit stretching from 100 miles at its closest point with Earth to some 11,000 miles at its highest point, which is the altitude where the GPS network resides. The newly-launched satellites were themselves fitted with a solid-fuel kick motor that ignited a few days into flight and finished the job of propelling the craft into a circular orbit.

United Launch Alliance's powerful Delta 4 and Atlas 5 rockets will haul the GPS 2F satellites directly to their desired destinations, bypassing the circuitous route of the past. So instead of taking days to reach the GPS orbit, the new 2F-2 satellite will get there in three-and-a-half hours today.

T+plus 100 minutes. To recap, the Delta 4 rocket carrying the GPS 2F-3 navigation satellite launched from Cape Canaveral's Complex 37 at 8:10 a.m. EDT after a flawless countdown and cooperation by the weather.

The rocket is now coasting toward a point about 11,000 nautical miles above the planet where the third and final burn is planned at T+plus 3 hours and 20 minutes.

T+plus 75 minutes. Today's official liftoff time was 8:10:00.242 a.m. EDT.

T+plus 60 minutes. Delta is 10,000 miles downrange from the Cape, now passing an hour into the mission, To see the track the rocket is following this morning, click here.

T+plus 41 minutes. The rocket has started the planned thermal-controlling roll program. It will continue in this roll for about 75 minutes.

T+plus 30 minutes. The rocket has just entered a two-hour, 56-minute coast period before the final engine burn to deliver GPS 2F-2 into the desired circular orbit to join the navigation network.

T+plus 27 minutes. Delta has flown into the transfer orbit with an apogee of 11,001 nautical miles, perigee of 129 nautical miles and inclination of 43.3 degrees.

T+plus 25 minutes, 25 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, 20 seconds. Engine control looking good.

T+plus 22 minutes, 35 seconds. Delta is 129 miles in altitude, 4,071 miles downrange from the launch pad, traveling at 18,071 mph.

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

T+plus 21 minutes, 35 seconds. Ignition! The RL10B-2 engine, fed by liquid hydrogen and liquid oxygen, has been reignited to propel GPS 2F-3 into an intermediate orbit.

T+plus 20 minutes. Delta is 139 miles in altitude, 3,435 miles downrange from the launch pad.

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 15 minutes. Delta has flown into a parking orbit with an apogee of 213 nautical miles, perigee of 88 nautical miles and inclination of 41.6 degrees.

T+plus 12 minutes, 48 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 10 minutes, 50 seconds. The upper stage's the RL10 engine working well, still firing as planned to reach a low-altitude parking orbit.

T+plus 10 minutes, 30 seconds. Good pitch and yaw controls on the upper stage engine.

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

T+plus 9 minutes, 55 seconds. Delta is 169 miles in altitude, 1,200 miles east of the launch pad.

T+plus 9 minutes, 20 seconds. Delta is 164.7 miles in altitude, 1,049 miles downrange from the launch pad, traveling at 21,156 feet per second.

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, 25 seconds. Rock steady controls on the upper stage engine.

T+plus 8 minutes. Delta is 156 miles in altitude, 856 miles east of the launch pad.

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

T+plus 6 minutes. RL10 continues to burn well as it thrusts to reach orbit.

T+plus 5 minutes. Good engine control.

T+plus 4 minutes, 44 seconds. The protective payload fairing enclosing the GPS satellite atop the rocket has separated.

T+plus 4 minutes, 35 seconds. The cryogenic RL10B-2 upper stage engine has ignited!

T+plus 4 minutes, 15 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. The main engine is throttling down to its minimum power setting in preparation for shutdown.

T+plus 3 minutes, 55 seconds. Passing Mach 16.

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 2 minutes, 25 seconds. Delta is 28 miles in altitude, 36 miles downrange from the launch pad.

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 Global Positioning System 2F-3 spacecraft, advancing the navigation network with every launch. And the Delta 4 rocket 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 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." 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 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-3 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 GPS 2F-3 spacecraft atop the Delta 4 has switched from ground-fed power to its internal batteries for launch.

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 8:10 a.m. EDT.

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

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 8:10 a.m. liftoff.

Assuming all systems remain go, clocks will resume ticking at 8:06 a.m. local time. During those final four minutes, the rocket will switch to internal power, ordnance will be armed, all four propellant tanks will be secured and the Range will announce a clear-to-launch.

At T-minus 14 seconds, the sparkler-like radial outward firing ignitors -- or ROFIs -- are started beneath the main engine nozzle. The Terminal Countdown Sequencer will grab control at T-minus 8.5 seconds to manage events in the crucial last seconds and oversee the rocket's status. The ignition sequence for the RS-68 powerplant follows at T-minus 5.5 seconds as the main hydrogen fuel valve is opened. As fuel floods through the engines, spectacular flame erupts at the base of the rocket as free hydrogen reaches the ROFIs.

The oxygen valve in the engine is opened at T-minus 2 seconds as the RS-68 begins roaring to life. The engine must rev up to full throttle -- 102 percent thrust level -- and undergo a rapid computer-controlled health check to ensure all parameters are met.

If any problem is detected before T-minus 40 milliseconds, the engine will shut down and the rocket prevented from lifting off.

A successful engine startup leads to T-0 as the four hold-down bolts that have been restraining the rocket to Earth finally detonate. The 20-story vehicle blasts off at 8:10 a.m. (1210 GMT) on the GPS 2F-3 navigation satellite deployment mission.

T-minus 4 minutes and holding. The countdown has entered the planned 15-minute hold leading toward the 8:10 a.m. EDT 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 launch team continues to report no constraints in the countdown.

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.

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.

About three-and-a-half hours after launch, the Delta 4 rocket will deliver its satellite payload directly to the GPS constellation's altitude 11,000 nautical miles high.

Ground controllers expect to have the new bird checked out and ready for use by the end of the year, the Air Force says. The new GPS 2F-3 spacecraft will take over the Plane A, Slot 1 location of the network, replacing a satellite that just was deployed in the summer of 1993.

"As the GPS 2Fs become operational, they are ensuring that the Air Force can meet the current and future needs of both military and civilian users," said Col. Bernie Gruber, director of the U.S. Air Force Space and Missile Systems Center's Global Positioning Systems Directorate.

Boeing is building a dozen Block 2F satellites for the Air Force.

"Boeing has worked alongside the Air Force for many years to continuously sustain and improve the GPS constellation," said Craig Cooning, vice president and general manager of Boeing Space & Intelligence Systems. "This new fleet of 12 GPS 2Fs will form the core of the GPS constellation for the next decade."

The Air Force launch weather officer has given his final planned briefing to mission managers in the countdown. There are no constraints currently and the outlook appears good for 8:10 a.m. EDT. The odds of acceptable launch conditions have improved to 80 percent.

The latest tweaks to the launch weather forecast now calls for scattered clouds at 2,000 and 4,000 feet, showers in the vicinity, southeasterly winds of 5 to 10 knots and a temperature of 80 degrees F.

The odds of acceptable launch weather remain at 80 percent.

The flight slews and commanding tests for the vehicle steering systems are complete and satisfactory. 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.

T-minus 30 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 8:10 a.m., which is the opening of today's 19-minute launch window to reach the desired location within the GPS constellation for replacing an aging satellite.

It is a beautiful sunrise here on the Space Coast! Countdown operations have gone very well overnight.

The countdown is entering the final 60 minutes until the Delta 4 rocket launch from Cape Canaveral at 8:10 a.m. EDT. Here's a look at some stats about today's mission. This will be:

• The 361st Delta rocket launch since 1960
• The 21st Delta 4 rocket mission since 2002
• The 17th Delta 4 rocket launch from Cape Canaveral
• The 17th use of Delta 4 by the Air Force
• The 9th Medium+ 4,2 configuration to fly
• The 54th Evolved Expendable Launch Vehicle flight
• The 65th United Launch Alliance mission since 2006
• The 14th Delta 4 under the ULA banner
• The 9th ULA launch this year
• The fourth launch of the Delta family in 2012
• The 63rd GPS satellite to launch
• The 52nd GPS launch on a Delta rocket
• The third GPS Block 2F satellite

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

Check out this photo gallery showing the GPS 2F-3 satellite being encapsulated in the rocket's nose cone last month.

The launch team is entering the last 90 minutes of the countdown. With fueling of the Delta 4 rocket completed, this phase of the count is fairly quiet. Engineers are monitoring systems while the clocks tick down.

Everything continues to proceed on schedule at Cape Canaveral for liftoff at 8:10 a.m. EDT.

Radio frequency link checks between tracking facilities at the Cape and the launch vehicle are complete.

Check out the gantry rollback photo gallery taken by Justin Ray on Wednesday night.

The newly revised weather forecast for the 8:10 a.m. EDT launch time has deleted the mid-level deck of broken clouds at 15,000 feet.

Meteorologists now calling for scattered clouds at 2,000 and 4,000 feet, showers in the vicinity, good visibility, easterly winds of 5 to 10 knots and a temperature of 78 degrees F.

The odds of favorable weather remain at 70 percent.

The upper stage liquid oxygen tank has entered the topping phase after the post-fueling tests were accomplished. That puts all four cryogenic fuel tanks aboard the Delta 4 rocket in topping mode.

The Delta 4 rocket stands fueled and ready for launch at 8:10 a.m. EDT today. The launch team is tracking no issues, weather conditions are green and the countdown remains on schedule.

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

And the upper stage liquid oxygen filling has been completed, now heading into post-loading tests.

The first stage liquid oxygen system has been topped off and conditioned for flight.

Now entering into the final three hours of the countdown to launch of Delta 361.

And now putting the upper stage's liquid hydrogen system in topping mode.

The topping mode is starting for the first stage's liquid hydrogen tank.

Loading of the upper stage liquid oxygen tank -- the last of the four vehicle tanks to fill -- is underway.

Post-filling tests on the first stage liquid oxygen system are complete. The tank is now entering topping mode.

Fast-fill loading of the upper stage liquid hydrogen tank has been accomplished as fueling proceeds very smoothly this morning at Complex 37.

After chilldown of the upper stage liquid oxygen system, loading the rocket's tank with 4,500 gallons will be performed. This is the last of the rocket's four cryogenic supplies to be filled in today's countdown to launch.

Now four hours till 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.

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.

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

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

Fast-filling of the first stage liquid hydrogen reservoir is wrapping up. After post-filling checks and valve tests, the tank will be placed in topping mode.

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.

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.

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.

No issues are being reported in the countdown as activities continue toward today's 8:10 a.m. EDT liftoff of the Delta 4 rocket and GPS 2F-3.

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.

Check out the gantry rollback photo gallery taken by Justin Ray on Wednesday night.

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 actually filling the vehicle with propellant.

Interrogation checks are getting started on the C-band beacon used for tracking the vehicle during its flight downrange.

T-minus 6 hours, 15 minutes and counting! The Terminal Countdown begins now for today's flight of the United Launch Alliance Delta 4 rocket with the Global Positioning System 2F-3 satellite.

The count has a planned built-in hold at T-minus 4 minutes lasting some 15 minutes, leading to liftoff at 8:10 a.m. EDT (1210 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 morning. Pad systems and equipment stand ready for fueling activities, which should kick off shortly.

The launch team has been polled to verify all consoles are manned and ready to begin the Terminal Countdown when this hold ends at 1:40 a.m.

The call to "man stations" has gone out to the launch team in preparation for fueling operations and the Terminal Count.

Weather forecasters have improved the outlook for today's launch window, upping the odds of acceptable conditions to 70 percent. Clouds and showers are the main concerns.

Meteorologists are calling for scattered clouds at 3,000 and 8,000 feet, a broken deck at 15,000 feet, showers in the vicinity, good visibility, easterly winds of 5 to 10 knots and a temperature of 78 degrees F.

T-minus 6 hours, 15 minutes and holding. The countdown has entered a planned 60-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 at 1:40 a.m. EDT, the Terminal Countdown phase of today's launch operation will begin.

The 330-foot tall mobile service tower has been retracted from the Delta 4 rocket at Cape Canaveral's pad 37B for the morning's launch that will place the GPS 2F-3 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 vehicle later overnight.

The Terminal Countdown will begin ticking at 1:40 a.m. EDT, leading to the multi-hour process of loading 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 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 5.5 seconds.

Liftoff remains scheduled for 8:10 a.m. EDT, the opening of a 19-minute window that extends to 8:29 a.m. EDT (1210-1229 GMT).

If you will be away from your computer but would like to receive occasional updates, sign up for our Twitter feed to get text message updates sent to your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

And check out Spaceflight Now's Facebook page!

Tower rollback has begun!

All of the lightning advisories have been lifted and the tower should be moving shortly.

It is a rainy, stormy, lightning-filled night along the Space Coast where the Delta rocket team awaits to get the mobile tower rolled back later this evening to begin the countdown for Thursday morning's launch of GPS 2F-3.

The crew was cleared from Complex 37 as a precaution for lightning, but expects to get permission shortly to resume work and roll on the planned timeline.

Watch this page for updates when the gantry gets moving and the Terminal Countdown commences overnight.

The United Launch Alliance team is resting ahead of the overnight countdown operations for the Delta 4 rocket carrying the Global Positioning System 2F-3 satellite.

"All is good," said Tony Taliancich, director of ULA's customer program office.

Workers will be reporting for duty at pad 37B tonight to perform final preparations to retract the mobile service gantry away from the booster at 10 p.m. EDT. Clocks will enter into the one-hour hold point at 12:40 a.m. EDT prior to picking up Terminal Count. Fueling begins around 2 a.m. EDT.

The weather forecast remains 60 percent favorable for the 19-minute launch window that opens at 8:10 a.m. EDT. Concerns for violating the cumulus cloud, precipitation and cloud thickness rules will be the areas to watch due to coastal showers.

The outlook includes scattered and broken decks of clouds, showers in the vicinity, southeasterly winds of 8 to 12 knots and a temperature of 78 degrees F.

The third 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-3 spacecraft is targeting an 8:10 a.m. EDT launch from Complex 37. A 19-minute window extending to 8:29 a.m. EDT will be available if conditions prevent an on-time liftoff.

Managers gathered this morning for the Launch Readiness Review, which culminated with the consensus to proceed with picking up the countdown Wednesday evening.

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

And if you will be away from your computer but would like to receive occasional updates, sign up for our Twitter feed to get text message updates sent to your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)

Forecasters are predicting a 60 percent chance of favorable weather, with the concerns being thick clouds, rain and violations of the cumulus cloud rule.

"Overnight and early morning offshore cloud cover and showers will likely be located over the near coastal waters with movement towards or parallel to the coast. Main concerns will be associated with the proximity of any cloud cover and precipitation," Air Force meteorologists say.

The launch time outlook includes scattered clouds at 2,000 and 8,000 feet, a broken deck at 15,000, showers in the vicinity, easterly winds of 8 to 12 knots and a temperature around 78 degrees F.

The forecast for Friday's backup launch opportunity looks about the same.

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 and the second went up in July 2011 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.

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. Ground controllers expect to have the new bird checked out and ready for use in about a month.

The GPS 2F-3 spacecraft takes over the Plane A, Slot 1 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-21 satellite launched by a Delta 2 rocket from Cape Canaveral on June 26, 1993.

Clouds and showers along the Space Coast will be potential problems for Thursday morning's launch attempt of the Delta 4 rocket and GPS satellite. Forecasters issued their initial outlook today and predict a 60 percent chance of acceptable launch conditions, with cumulus clouds, precipitation and the thickness of cloud cover all areas for possibly violating the weather criteria.

The launch weather team's forecast: "Florida peninsula will be located between upper level low pressure over the Gulf of Mexico and upper level high pressure over the western Atlantic. This will result in south-southwesterly flow aloft and deep layered moisture across the state. At the surface a weak surface trough dissipates while a high pressure ridge axis builds north and west across central Florida. Surface winds will become onshore, especially south of the Cape. Overnight and early morning offshore cloud cover and showers will likely be located over the near coastal waters with movement towards or parallel to the coast. Main concerns will be associated with the proximity of any cloud cover and precipitation. Similar conditions expected the following days."

The specifics for launch time on Thursday include scattered and broken decks of clouds, showers in the vicinity, easterly winds of 8 peaking to 12 knots, humidity of 94 percent and a temperature of 78 degrees.

Shooting for a morning blastoff Thursday, a United Launch Alliance Delta 4 rocket and Global Positioning System satellite payload will undergo a final technical assessment today and their readiness review tomorrow before entering into countdown operations Wednesday night.

Read our preview story.

The latest Global Positioning System satellite has been loaded aboard its ride to space, arriving today at Cape Canaveral's Complex 37 for mounting atop the United Launch Alliance Delta 4 rocket.

A motorized trailer carried the 3,400-pound satellite up the road to Complex 37 overnight. It was positioned on the oceanside of the mobile service gantry and hoisted into the pad tower for bolting to the rocket's second stage.

This begins the final phase of the launch campaign, with the integrated systems test between payload and rocket coming up in a few days.

At Complex 37 today, the Delta 4 is being fueled with supercold liquid hydrogen and liquid oxygen rocket fuel for the Wet Dress Rehearsal, a full-up simulation of launch day activities.

The WDR is a standard test that occurs before each Delta 4 mission to run through the countdown to exercise both equipment and the team.

After getting through this milestone successfully, workers will turn their attention to transporting the GPS 2F-3 satellite to the pad and mounted atop the two-stage launcher.

Liftoff remains targeted for Oct. 4 at 8:10 a.m. EDT.

The Delta 4 rocket that will launch in October for the direct benefit of the world's population using the Global Positioning System was stacked on its Cape Canaveral pad last week.

The United Launch Alliance-made vehicle is targeting an Oct. 4 blastoff to deploy the GPS 2F-3 navigation satellite, replacing a 19-year-old craft in the orbiting constellation that serves billions of military and civilan users across the planet.

Liftoff will be possible during a morning launch window extending from 8:10 to 8:29 a.m. EDT (1210-1229 GMT).

Read our full story.