BY JUSTIN RAY

Follow the countdown and launch of the Boeing Delta 4 rocket with the GOES-N weather observatory. Reload this page for the very latest on the mission.

Additional coverage for subscribers:
VIDEO: DELTA 4 BLASTS OFF WITH GOES-N SHORT | LONGER
VIDEO: THE FULL LAUNCH EXPERIENCE PLAY
VIDEO: WIDE-SCREEN VIEW FROM NASA CAUSEWAY PLAY

VIDEO: TUESDAY'S PRE-LAUNCH NEWS BRIEFING DIAL-UP | BROADBAND
AUDIO: LISTEN TO THE NEWS CONFERENCE FOR IPOD
VIDEO: NARRATED ANIMATION OF GOES-N LAUNCH PLAY
VIDEO: GOES-N HOISTED ATOP DELTA 4 ROCKET PLAY
VIDEO: SPACECRAFT DRIVEN TO LAUNCH PAD 37B PLAY
VIDEO: ROCKET NOSE CONE PLACED AROUND GOES-N PLAY
VIDEO: GOES-N LIFTED TO ROCKET ADAPTER AT ASTROTECH PLAY
VIDEO: AUGUST 15 LAUNCH ATTEMPT SCRUBBED PLAY
VIDEO: AUGUST 16 LAUNCH ATTEMPT SCRUBBED PLAY
VIDEO: VIEWS OF DELTA 4 ON THE PAD PLAY
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THURSDAY, MAY 25, 2006

The first member of a revitalized series of spaceborne weather watchers was shepherded into orbit by a Delta 4 rocket in a marathon Wednesday evening launch, giving American meteorologists a sophisticated new tool to warn against dangerous severe storms. Read our full story.

0232 GMT (10:32 p.m. EDT Wed.)

T+plus 4 hours, 21 minutes, 35 seconds. SPACECRAFT SEPARATION! The Geostationary Operational Environmental Satellite-N (GOES-N) has been deployed from the Delta 4 rocket's upper stage.

This completes the 315th Delta rocket launch and the fifth for the next-generation Delta 4.

0231 GMT (10:31 p.m. EDT Wed.)

T+plus 4 hours, 20 minutes, 30 seconds. About one minute remains until payload deployment.

0229 GMT (10:29 p.m. EDT Wed.)

T+plus 4 hours, 18 minutes, 30 seconds. Spin-up is complete.

0229 GMT (10:29 p.m. EDT Wed.)

T+plus 4 hours, 18 minutes. The spin-up maneuver by the second stage has started in preparation for deployment of GOES. Small jets on the stage are giving the push to induce the spin.

0227 GMT (10:27 p.m. EDT Wed.)

T+plus 4 hours, 16 minutes. About five minutes until payload separation to complete this launch.

0223 GMT (10:23 p.m. EDT Wed.)

T+plus 4 hours, 12 minutes. The vehicle performs maneuvers in pitch, yaw and roll to re-orient itself into the attitude for release of GOES-N.

0222 GMT (10:22 p.m. EDT Wed.)

T+plus 4 hours, 11 minutes, 3 seconds. SECO 3. The engine has shut down, ending the powered phase of today's the Delta 4 mission.

0221 GMT (10:21 p.m. EDT Wed.)

T+plus 4 hours, 10 minutes, 8 seconds. Engine ignition! The RL10B-2 motor has fired back to life for the third of three burns to send the GOES-N spacecraft into the proper orbit.

0220 GMT (10:20 p.m. EDT Wed.)

T+plus 4 hours, 9 minutes. Restart of the upper stage is about a minute away. Liquid oyxgen system pre-start activities are starting.

0217 GMT (10:17 p.m. EDT Wed.)

T+plus 4 hours, 6 minutes. The rocket has reached the positioning for the burn.

0211 GMT (10:11 p.m. EDT Wed.)

T+plus 4 hours. Ten minutes till ignition.

0209 GMT (10:09 p.m. EDT Wed.)

T+plus 3 hours, 58 minutes. The second stage has started its turn to the engine burn orientation.

0141 GMT (9:41 p.m. EDT Wed.)

T+plus 3 hours, 30 minutes. Now 40 minutes away from engine re-start on the second stage. In preparation for that event, the rocket will complete the BBQ thermal roll at T+plus 3 hours, 58 minutes and begin maneuvering itself into the proper orientation for ignition. The burn position should be achieved by T+plus 4 hours, 6 minutes. Then, the stage will start a system chilldown before firing the engine with cryogenic fuel and use its tiny thrusters to settle the propellants in the tanks.

0111 GMT (9:11 p.m. EDT Wed.)

T+plus 3 hours. The rocket is heading away from Earth in this egg-shaped orbit that extends from about 109 nautical miles at its closest point to 18,461 miles at the furthest. The upcoming engine firing at 10:21 p.m. EDT will occur at an altitude of about 17,525 miles. The burn lasts just 55 seconds, but will raise the orbit's low point to 3,548 miles, increase the high point to 18,995 miles and reduce inclination closer to the equator. (Numbers based on pre-flight predictions listed in mission press kit).

Deployment of GOES-N from the second stage is expected at 10:32 p.m.

0105 GMT (9:05 p.m. EDT Wed.)

We have posted a long-length movie that captures the thrill of the Delta 4 launch carrying GOES-N. As the countdown resumes from the T-minus 5 minute hold, watch as the Boeing launch team readies the rocket for liftoff. The video takes you through the arrival in orbit when the second stage engine completes its initial firing more than 12 minutes into flight. The video is available to Spaceflight Now Plus users.

0029 GMT (8:29 p.m. EDT Wed.)

T+plus 2 hours, 18 minutes. We've passed the half-way mark in today's launch. The rocket is 11,992 nautical miles in altitude and traveling 10,885 feet per second.

0015 GMT (8:15 p.m. EDT Wed.)

T+plus 2 hours, 4 minutes. The second stage continues in the Passive Thermal Control phase of the orbital coast.

WEDNESDAY, MAY 24, 2006
2338 GMT (7:38 p.m. EDT)

Kennedy Space Center photographer Ken Thornsley shot these images of liftoff from the press site along the NASA Causeway. See the images here.

2312 GMT (7:12 p.m. EDT)

T+plus 61 minutes. The second stage remains in the quiet coast through space. It is in the "barbecue roll." This gentle rolling motion ensures heating on the vehicle is evenly distributed.

2248 GMT (6:48 p.m. EDT)

T+plus 38 minutes. Delta is now 847 miles in altitude as it comes within range of the Diego Garcia tracking station in the Indian Ocean.

2246 GMT (6:46 p.m. EDT)

T+plus 35 minutes. To see the track the rocket is following this evening, click here.

2239 GMT (6:39 p.m. EDT)

T+plus 28 minutes. The rocket has just entered a three-hour, 42-minute coast period before the final engine burn to deliver GOES into the desired orbit this evening.

2238 GMT (6:38 p.m. EDT)

T+plus 27 minutes, 14 seconds. SECO 2. The second of three firings by the upper stage during today's launch has been completed.

2237 GMT (6:37 p.m. EDT)

T+plus 26 minutes, 5 seconds. About one minute left in this burn by the Delta 4 rocket's upper stage.

2236 GMT (6:36 p.m. EDT)

T+plus 25 minutes, 30 seconds. This burn injects the rocket into a highly elliptical orbit stretching almost 19,000 nautical miles at its furthest point.

2235 GMT (6:35 p.m. EDT)

T+plus 24 minutes, 30 seconds. The engine firing continues. This burn will last just over four minutes in duration.

2234 GMT (6:34 p.m. EDT)

T+plus 23 minutes, 30 seconds. Good engine chamber pressure reported.

2234 GMT (6:34 p.m. EDT)

T+plus 23 minutes, 14 seconds. The RL10B-2 liquid hydrogen/liquid oxygen engine has been reignited to propel GOES-N into an intermediate orbit.

2233 GMT (6:33 p.m. EDT)

T+plus 22 minutes. Accra is picking up the rocket's signal. Standing by for ignition in about a minute.

2231 GMT (6:31 p.m. EDT)

T+plus 20 minutes. By this point in the flight, the upper stage should have maneuvered itself into the proper attitude for engine restart. However, the vehicle is out of range from any ground station and the maneuver can't be confirmed in real-time. Ignition of the RL10 engine is about three minutes away.

2225 GMT (6:25 p.m. EDT)

T+plus 16 minutes. The vehicle is now in a coast most for the next 8 minutes. It is passing out of range from the Antigua tracking station. A deployment station set up at Accra, Ghana should acquire the rocket's signal just before the next firing of the second stage engine.

2223 GMT (6:23 p.m. EDT)

T+plus 12 minutes, 44 seconds. SECO 1. Confirmation that the second stage engine has shut down after the first of three planned firings to inject the GOES spacecraft into geosynchronous transfer orbit.

2223 GMT (6:23 p.m. EDT)

T+plus 12 minutes. Engine pressures still reported normal.

2222 GMT (6:22 p.m. EDT)

T+plus 11 minutes, 15 seconds. The vehicle is 129.2 miles in altitude.

2221 GMT (6:21 p.m. EDT)

T+plus 10 minutes, 15 seconds. The second stage systems are operating properly as the RL10 engine fires to reach a low-altitude parking orbit this evening.

2220 GMT (6:20 p.m. EDT)

T+plus 9 minutes, 30 seconds. The RL10 engine is burning a mixture of liquid oxygen and liquid hydrogen cryogenic propellants.

2219 GMT (6:19 p.m. EDT)

T+plus 8 minutes, 40 seconds. About four minutes remain in this firing of the second stage.

2218 GMT (6:18 p.m. EDT)

T+plus 7 minutes, 10 seconds. Good chamber pressure data being reported from the RL10 engine as it thrusts to reach orbit.

2217 GMT (6:17 p.m. EDT)

T+plus 6 minutes. The second stage engine continues to fire. This burn will place the vehicle into an initial parking orbit around Earth.

2216 GMT (6:16 p.m. EDT)

T+plus 5 minutes, 5 seconds. The protective payload fairing enclosing the GOES satellite atop the rocket has separated.

2215 GMT (6:15 p.m. EDT)

T+plus 4 minutes, 52 seconds. The cryogenic RL10B-2 upper stage engine has ignited!

2215 GMT (6:15 p.m. EDT)

T+plus 4 minutes, 40 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.

2215 GMT (6:15 p.m. EDT)

T+plus 4 minutes, 27 seconds. MECO! Main engine cutoff confirmed as the RS-68 powerplant shuts down.

2214 GMT (6:14 p.m. EDT)

T+plus 4 minutes. 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.

2214 GMT (6:14 p.m. EDT)

T+plus 3 minutes, 35 seconds. The main engine is throttling down to 60 percent thrust for the rest of its firing in today's launch.

2214 GMT (6:14 p.m. EDT)

T+plus 3 minutes, 5 seconds. Altitude 43.9 miles.

2213 GMT (6:13 p.m. EDT)

T+plus 2 minutes. Everything looking good.

2212 GMT (6:12 p.m. EDT)

T+plus 1 minute, 45 seconds. Solid motor separation! The spent boosters have been shed from the first stage. Delta 4 continues powering its way toward space on the thrust generated by the RS-68 main engine.

2212 GMT (6:12 p.m. EDT)

T+plus 1 minute, 39 seconds. The twin solid rocket boosters have burned out of their propellant. Standing by for jettison.

2212 GMT (6:12 p.m. EDT)

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

2211 GMT (6:11 p.m. EDT)

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

2211 GMT (6:11 p.m. EDT)

T+plus 30 seconds. The Delta 4 rocket is manuevering on course for the eastward trek from the Florida coastline. The main engine is firing at full throttle and the two strap-on boosters are giving a powerful extra kick.

2211 GMT (6:11 p.m. EDT)

LIFTOFF! Liftoff of the Boeing Delta 4 rocket and the GOES-N spacecraft, launching a new era in weather observing for the Americas. And the vehicle has cleared the tower!

2210 GMT (6:10 p.m. EDT)

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

2210 GMT (6:10 p.m. EDT)

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

2210 GMT (6:10 p.m. EDT)

T-minus 30 seconds. Green board. All systems remain "go" for launch.

2210 GMT (6:10 p.m. EDT)

T-minus 35 seconds. Second stage liquid hydrogen tank is at flight level.

2210 GMT (6:10 p.m. EDT)

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.

2209 GMT (6:09 p.m. EDT)

T-minus 65 seconds. Second stage liquid oxygen tank has been secured at flight level.

2209 GMT (6:09 p.m. EDT)

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

2209 GMT (6:09 p.m. EDT)

T-minus 80 seconds. The liquid hydrogen fuel tank on the second stage is being secured for launch.

2209 GMT (6:09 p.m. EDT)

T-minus 2 minutes. Securing of the second stage liquid oxygen tank is starting.

2208 GMT (6:08 p.m. EDT)

T-minus 2 minutes, 25 seconds. First stage cryogenic tanks are reported at flight levels and pressures.

2208 GMT (6:08 p.m. EDT)

T-minus 3 minutes and counting. The first stage liquid hydrogen and liquid oxygen systems have been secured.

2207 GMT (6:07 p.m. EDT)

T-minus 4 minutes and counting. Vehicle ordnance is being armed.

2206 GMT (6:06 p.m. EDT)

T-minus 4 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.

2206 GMT (6:06 p.m. EDT)

T-minus 5 minutes and counting! The final phase of today's countdown has commenced for launch of Boeing's Delta 4 rocket carrying the GOES-N weather observatory. Liftoff is set to occur at 6:11 p.m. EDT (2211 GMT) from pad 37B at Cape Canaveral Air Force Station.

2205 GMT (6:05 p.m. EDT)

Approval has been given to resume the count as planned.

2204 GMT (6:04 p.m. EDT)

Boeing mission director Rich Murphy has performed his management poll. All is in concurrence to proceed with liftoff at 6:11 p.m.

2203 GMT (6:03 p.m. EDT)

The launch pad swing arm retraction system pins are being pulled. The three arms will be rotated away from the Delta 4 rocket at liftoff.

2202 GMT (6:02 p.m. EDT)

The pre-launch poll is complete. Everyone voiced a "go" for launch.

2200 GMT (6:00 p.m. EDT)

A readiness poll of the launch team is beginning.

2200 GMT (6:00 p.m. EDT)

Launch weather officer Joel Tumbiolo has confirmed to Boeing mission director Rich Murphy that weather conditions remain "go" for liftoff.

2157 GMT (5:57 p.m. EDT)

The payload team reports GOES-N is running on internal power.

2156 GMT (5:56 p.m. EDT)

Now 15 minutes from launch time. The GOES-N spacecraft atop the Delta 4 is switching from ground-fed power to its internal batteries for launch.

2151 GMT (5:51 p.m. EDT)

T-minus 5 minutes and holding. The countdown has entered a planned 15-minute hold. 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.

2149 GMT (5:49 p.m. EDT)

Just about to go into the final hold point. There are no technical constraints being assessed on the Delta 4 rocket or GOES-N spacecraft, Boeing says. Weather conditions remain favorable.

2146 GMT (5:46 p.m. EDT)

T-minus 10 minutes and counting. The countdown will enter a planned hold in five minutes.

The 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, which are covered with shatter-proof film. Other rooms are also set up for engineering support.

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

2141 GMT (5:41 p.m. EDT)

Now 30 minutes to go.

2133 GMT (5:33 p.m. EDT)

Launch weather officer Joel Tumbiolo says conditions are looking very good for liftoff today. The weather aircraft indicates there are two separate 1,000-foot thick cloud decks overhead. The limit on thickness is 4,500 feet, so that rule is not threatened. Also, the pad winds remain stable below the 15-knot limit.

2126 GMT (5:26 p.m. EDT)

T-minus 30 minutes and counting. The countdown is headed to the T-minus 5 minute point where a 15-minute hold is planned. Liftoff is targeted for 6:11 p.m., the opening of today's 60-minute launch window.

2123 GMT (5:23 p.m. EDT)

The first stage Common Booster Core slews and the commanding tests for the strap-on solid rocket motors have been finished, wrapping up this pre-launch program.

2116 GMT (5:16 p.m. EDT)

The second stage engine steering checks have been completed. The first stage tests are next.

2112 GMT (5:12 p.m. EDT)

Weather continues to look acceptable for launch. The weather team has upped the odds of meeting the launch rules to 80 percent. It had been 60 percent.

2110 GMT (5:10 p.m. EDT)

The engine slew tests have begun, starting with the second stage RL10 engine.

2109 GMT (5:09 p.m. EDT)

The team is now preparing to conduct the steering checks of the Delta 4 rocket's engines.

2106 GMT (5:06 p.m. EDT)

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

2100 GMT (5:00 p.m. EDT)

The Air Force-controlled Eastern Range has performed the inhibited command destruct receiver checks. This ensures safety personnel can destroy the Delta 4 rocket if it veers off course or experiences a major problem.

2058 GMT (4:58 p.m. EDT)

Using launch pad cameras, engineers have completed a check of the rocket's thermal insulation as planned with no problems reported.

2047 GMT (4:47 p.m. EDT)

Health checks of the command receiver decoder devices on the rocket are underway. These units would hear the command from Range Safety and trigger the Delta 4's destruct system if a problem occurred during launch.

2041 GMT (4:41 p.m. EDT)

And we're now entering the last 90 minutes of the countdown. With fueling of the Delta 4 rocket completed, this phase of the count is mostly quiet. The launch team is monitoring systems while the clocks tick down. In a little while, the rocket's safety system will be checked and a series of engine steering tests will occur. Everything continues to proceed at Cape Canaveral for liftoff at 6:11 p.m. EDT.

2034 GMT (4:34 p.m. EDT)

The RF link checks between the rocket and ground have been completed and verified satisfactory.

2032 GMT (4:32 p.m. EDT)

Telemetry RF link checks have started. The TEL-4 ground tracking station at the Cape will acquire the telemetry stream during this test to ensure good continuity for flight.

2030 GMT (4:30 p.m. EDT)

Reporters and photographers are now gathering along the NASA Causeway at Cape Canaveral to cover today's launch.

2029 GMT (4:29 p.m. EDT)

All four cryogenic fuel tanks aboard the Delta 4 rocket are in stable replenish mode to replace the propellants that boil off given their supercold nature.

2026 GMT (4:26 p.m. EDT)

Now passing Launch Minus-1 hour, 45 minutes and counting.

2018 GMT (4:18 p.m. EDT)

Winds are staying below the 15-knot limit. And there's actually some blue sky over Cape Canaveral.

2011 GMT (4:11 p.m. EDT)

Liftoff time is just two hours away now.

2010 GMT (4:10 p.m. EDT)

The topping mode has started for the second stage's liquid hydrogen tank.

2004 GMT (4:04 p.m. EDT)

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

2002 GMT (4:02 p.m. EDT)

Second stage liquid oxygen tank loading is complete.

1954 GMT (3:54 p.m. EDT)

The first stage liquid hydrogen tank is now entering the topping phase.

1944 GMT (3:44 p.m. EDT)

Fast-fill of the second stage liquid hydrogen tank has finished. Checks will performed before topping commences.

1937 GMT (3:37 p.m. EDT)

Loading of the first stage liquid hydrogen tank has been completed. Vent and relief checks are underway now.

The second stage liquid oxygen and liquid hydrogen tanks are still being loaded.

1935 GMT (3:35 p.m. EDT)

A current check of the weather shows all of the launch rules remain "go."

1911 GMT (3:11 p.m. EDT)

Now entering the last three hours of the countdown. Fueling of the Boeing Delta 4 rocket continues for today's 6:11 p.m. EDT launch of the GOES-N weather satellite from Cape Canaveral, Florida.

1908 GMT (3:08 p.m. EDT)

Launch weather officer Joel Tumbiolo just gave another update to mission managers. Some thunderstorms have developed to our north. However, they are not expected to be a threat. One cell was seen forming to our west near Tampa but it died out.

All weather rules are "go" for launch right now. But the team will continue to watch for thick clouds, anvil clouds from thunderstorms and winds violating the 15-knot limit in the last five minutes of the countdown. Winds have been steady in the 8-10 knot range this afternoon.

1902 GMT (3:02 p.m. EDT)

The second stage conditioning on the liquid hydrogen side has finished. Loading of the tank is starting. This is the last of the rocket's four cryogenic supplies to be filled in today's countdown to launch.

Meanwhile, the second stage's liquid oxygen tank is in fast-fill now. And the first stage liquid hydrogen tank is over 80 percent full now.

1853 GMT (2:53 p.m. EDT)

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

1846 GMT (2:46 p.m. EDT)

The first stage's liquid hydrogen tank continues in fast-fill and the liquid oxygen tank is in topping. The second stage tanks being conditioned for loading.

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 tanks' large supplies allow for several launch attempts before having to be replenished.

The cryogenics flow from the storage tanks, through pipes to the base of the pad. For the first stage, 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 stage in separate umbilicals. The second stage receives its cryos from the middle swing arm that extends from the Fixed Umbilical Tower to the front-side of the rocket.

1839 GMT (2:39 p.m. EDT)

Post-filling tests on the first stage liquid oxygen system are complete. The tank is now entering topping mode. And the "go" has been given for the second stage liquid oxygen chilldown in advance of fueling.

1829 GMT (2:29 p.m. EDT)

The launch team has been given approval to start chilldown conditioning of the second stage liquid hydrogen system.

1819 GMT (2:19 p.m. EDT)

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 a little later, after the launch team performs vent and relief checks.

1818 GMT (2:18 p.m. EDT)

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

1811 GMT (2:11 p.m. EDT)

Boeing photographer Carleton Bailie captured some great shots this morning as the mobile service tower was rolled back to reveal the Delta 4 rocket. A gallery of his images is available here.

1806 GMT (2:06 p.m. EDT)

The start of liquid hydrogen fueling of the first stage is now confirmed.

1802 GMT (2:02 p.m. EDT)

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, 25 seconds of the launch.

1752 GMT (1:52 p.m. EDT)

First stage liquid oxygen loading has transitioned to "fast-fill" mode. The liquid hydrogen system remains in the thermal chilldown process.

1735 GMT (1:35 p.m. EDT)

The hydrogen system's cold gas chilldown conditioning is now underway.

1726 GMT (1:26 p.m. EDT)

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

1720 GMT (1:20 p.m. EDT)

The first stage liquid oxygen chilldown is complete. Fueling will begin 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.

1711 GMT (1:11 p.m. EDT)

Now inside the final five hours of the GOES-N launch countdown.

1706 GMT (1:06 p.m. EDT)

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

1700 GMT (1:00 p.m. EDT)

Chilldown of the 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.

1641 GMT (12:41 p.m. EDT)

T-minus 5 hours, 15 minutes and counting! The Terminal Countdown begins now for today's launch of the Boeing Delta 4 rocket with the Geostationary Operational Environmental Satellite-N (GOES-N).

The countdown has one planned built-in hold at T-minus 5 minutes for 15 minutes, leading to liftoff at 6:11 p.m. EDT.

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.

1640 GMT (12:40 p.m. EDT)

The "go" has been given to resume the countdown as planned.

1629 GMT (12:29 p.m. EDT)

The Delta 4 rocket's avionics have been put through initial testing today.

1627 GMT (12:27 p.m. EDT)

The launch team has been polled to ensure all consoles are manned and ready to begin the Terminal Countdown when this hold ends at 12:41 p.m. A briefing on countdown procedures is now underway.

1621 GMT (12:21 p.m. EDT)

Man stations for Terminal Count, the launch team has just been instructed.

Read our earlier Mission Status Center coverage.