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The Mission

Rocket: Atlas 5 (AV-007)
Payload: Mars Reconnaissance Orbiter
Date: August 12, 2005
Window: 7:43-9:43 a.m. EDT (1143-1343 GMT)
Site: Complex 41, Cape Canaveral, Florida

Mission Status Center

MRO instruments

Science objectives

Technology objectives

Atlas 5 rocket info

Cape's Complex 41

Atlas archive

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Launch of Atlas 5!
The fifth Lockheed Martin Atlas 5 rocket blasts off to deploy the Inmarsat 4-F1 mobile communications spacecraft into orbit. (2min 35sec file)
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Extended launch movie
An extended length clip follows the Atlas 5 launch from T-minus 1 minute through ignition of the Centaur upper stage and jettison of the nose cone. (6min 43sec file)
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Onboard camera
An onboard video camera mounted to the Atlas 5 rocket's first stage captures this view of the spent solid-fuel boosters separating.
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Press site view
This view of the Atlas 5 launch was recorded from the Kennedy Space Center Press Site. (1min 27sec file)
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Atlas 5 preview
Preview the launch of Lockheed Martin's Atlas 5 rocket carrying the Inmarsat 4-F1 communications spacecraft with this narrated animation package. (3min 47sec file)
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Inmarsat info
Andrew Sukawaty, CEO of Inmarsat, provides a detailed overview of the company and its newest satellite to be launched aboard Lockheed Martin's Atlas 5 rocket. (13min 53sec file)
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Stats on Inmarsat 4-F1
Michel LeMoine, satellite program director at Astrium, gives a technical oveview of the Inmarsat 4-F1 spacecraft and its mission during the pre-launch news conference. (8min 59sec file)
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Launch of Atlas 5
The Lockheed Martin Atlas 5 rocket launches at 7:07 a.m. EST from Cape Canaveral carrying the AMERICOM 16 communications spacecraft. (6min 22sec file)
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Press site view
The sunrise launch of Atlas 5 is shown in this view from the Kennedy Space Center press site at Complex 39. (QuickTime file)
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Rocket rollout
Riding on its mobile launching platform, the Atlas 5 rocket is rolled from its assembly building to the launch pad at Complex 41 just hours before the scheduled liftoff time carrying AMC 16. (4min 41sec file)
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Atlas 5 news briefing
Mission officials hold the pre-launch news conference in Cape Canaveral on Thursday, Dec. 16 to preview the flight of Atlas 5 with AMC 16. (40min 41sec file)
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AMC 16 launch preview
Preview the launch of Lockheed Martin's Atlas 5 rocket carrying the AMERICOM 16 communications spacecraft with this narrated animation package. (2min 52sec file)
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The AMC 16 spacecraft
This narrated movie provides an overview of the Lockheed Martin-built AMC 16 spacecraft for operator SES AMERICOM. (3min 30sec file)
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Last Atlas 2AS rocket
Lockheed Martin's last Atlas 2AS rocket blasts off from Cape Canaveral carrying a classified National Reconnaissance Office spacecraft on August 31. (3min 59sec file)
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Salute to pad 36A
The Atlas launch team in the Complex 36 Blockhouse celebrate the history of pad 36A in a post-launch toast. The Atlas 2AS rocket flight was the last to launch from the pad, which entered service in 1962. (2min 09sec file)
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Mission success
The classified NRO payload is deployed from the Centaur upper stage to successfully complete the launch. (1min 56sec file)
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Follow the countdown and launch of the Lockheed Martin Atlas 5 rocket with NASA's Mars Reconnaissance Orbiter. Reload this page for the very latest on the mission.

Rollout | Launch


A Lockheed Martin Atlas 5 rocket boosted NASA's Mars Reconnaissance Orbiter into space today, kicking off a $720 million mission to sniff out underground ice deposits, to map the red planet's geology with unprecedented clarity and to monitor its tenuous, dusty atmosphere in an ongoing scientific assault. Read our full story.

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1259 GMT (8:59 a.m. EDT)

NASA plans a post-launch press conference around 10:30 a.m. EDT to review the spacecraft's state of health. We'll pause our live coverage for now. Check back for a complete wrap-up story, pictures and lots of movie clips from this morning's beautiful launch.

1258 GMT (8:58 a.m. EDT)

T+plus 75 minutes. NASA's two-and-a-half ton Mars Reconnaissance Orbiter, an instrument-laden spacecraft designed to capture an unprecedented level of detail about the Red Planet and help guide future missions, has successfully departed Earth.

Liftoff of the Lockheed Martin Atlas 5 rocket occurred on time this morning 7:43 a.m. EDT (1143 GMT) from Complex 41 at Cape Canaveral Air Force Station, Florida.

MRO should arrive at Mars next March and start five months of aerobraking maneuvers to reach its science-collecting near-polar orbit stretching from 199 miles above the planet's surface at its furthest point to just 158 miles at the closest.

The $720 million mission's main science phase runs from November 2006 to December 2008, enabling the onboard cameras, spectrometer, climate sounder and subsurface radar to gather an unparalleled amount of data about Mars.

"We will keep pursuing a follow-the-water strategy with Mars Reconnaissance Orbiter," said Michael Meyer, Mars exploration chief scientist at NASA Headquarters. "Dramatic discoveries by Mars Global Surveyor, Mars Odyssey and the Mars Exploration Rovers about recent gullies, near-surface permafrost and ancient surface water have given us a new Mars in the past few years. Learning more about what has happened to the water will focus searches for possible Martian life, past or present."

The instruments on MRO will offer sharper focus than earlier spacecraft, giving scientists hope for revolutionary discoveries.

"Higher resolution is a major driver for this mission. Every time we look with increased resolution, Mars has said, 'Here's something you didn't expect. You don't understand me yet.' We're sure to find surprises," said Richard Zurek, the orbiter's project scientist from NASA's Jet Propulsion Laboratory.

Featuring the largest telescope to orbit another planet, MRO's high-resolution camera can spot rocks as small as three-feet across and surface layering that will be critical to Mars research as well as selecting safe but interesting sites for future landers.

"Mars Reconnaissance Orbiter is the next step in our ambitious exploration of Mars," said Douglas McCuistion, director of the Mars Exploration Program in NASA's Science Mission Directorate. "We expect to use this spacecraft's eyes in the sky in coming years as our primary tools to identify and evaluate the best places for future missions to land."

1257 GMT (8:57 a.m. EDT)

T+plus 74 minutes, 45 seconds. The solar array deployment sequence is now reported complete. Power-generating levels are good, NASA says.

1253 GMT (8:53 a.m. EDT)

T+plus 70 minutes, 30 seconds. The Mars Reconnaissance Orbiter is drawing power from the solar arrays.

1252 GMT (8:52 a.m. EDT)

T+plus 69 minutes. "What a difference a day makes," NASA launch manager Chuck Dovale says. There were no problems worked during today's countdown unlike the problems with weather and the scrub-forcing problem with ground software.

1248 GMT (8:48 a.m. EDT)

T+plus 65 minutes. The MRO team reports the spacecraft's separation from the Centaur was clean. MRO is operating normally on its control thrusters and good communications are being received through the tracking site.

1247 GMT (8:47 a.m. EDT)

T+plus 64 minutes. The spacecraft's two large solar panels being deployed cover 220 square feet, providing 2,000 watts of power when at the mission's farthest point from the sun. It will take 15-20 minutes for the array deployment sequence to be completed.

1244 GMT (8:44 a.m. EDT)

T+plus 61 minutes, 26 seconds. Contact has been established with Mars Reconnaissance Orbiter via a Japanese communications tracking site. The spacecraft is alive and operating.

1243 GMT (8:43 a.m. EDT)

T+plus 60 minutes. A Japanese space agency tracking station should acquire the craft's signal in a few minutes as an autonomous sequence of onboard events begin to unfurl the two power-generating solar arrays and deploy the 10-foot primary communications antenna.

1242 GMT (8:42 a.m. EDT)

T+plus 59 minutes. Orbital parameters indicate a spot-on launch of Mars Reconnaissance Orbiter by the Atlas-Centaur rocket this morning.

1240 GMT (8:40 a.m. EDT)

T+plus 57 minutes, 54 seconds. SPACECRAFT SEPARATION! The Mars Reconnaissance Orbiter has been released from the Centaur!

This completes the sixth flight of Lockheed Martin's next-generation Atlas 5 rocket, all of which have been successful. It also extends the string of successful missions by the Atlas family to 77 dating back to 1993.

1240 GMT (8:40 a.m. EDT)

T+plus 57 minutes, 5 seconds. The Centaur has begun its spin-up for payload deploy.

1238 GMT (8:38 a.m. EDT)

T+plus 55 minutes, 45 seconds. The Centaur is in its reorientation maneuver to prepare for casting free the Mars Reconnaissance Orbiter for its 310 million mile cruise through interplanetary space.

1238 GMT (8:38 a.m. EDT)

T+plus 55 minutes, 6 seconds. MECO 2! The Centaur's Pratt & Whitney RL10 engine has shut down as expected.

1237 GMT (8:37 a.m. EDT)

T+plus 54 minutes. No problems have been noted in this second Centaur firing.

1236 GMT (8:36 a.m. EDT)

T+plus 53 minutes. About two minutes left to go in powered flight.

1235 GMT (8:35 a.m. EDT)

T+plus 52 minutes, 30 seconds. The acceleration level is 1.2 g's.

1234 GMT (8:34 a.m. EDT)

T+plus 51 minutes, 30 seconds. The upper stage continues to fire.

1233 GMT (8:33 a.m. EDT)

T+plus 50 minutes, 50 seconds. Engine performance looks good.

1232 GMT (8:32 a.m. EDT)

T+plus 49 minutes, 37 seconds. Centaur is firing again! The single RL10 engine has reignited as planned for a five-and-a-half minute burn to accelerate Mars Reconnaissance Orbiter out of Earth orbit for the journey to the Red Planet.

1230 GMT (8:30 a.m. EDT)

T+plus 47 minutes, 40 seconds. Time to ignition is two minutes.

1229 GMT (8:29 a.m. EDT)

T+plus 46 minutes. The rocket stage is now oriented in the right attitude for ignition.

1227 GMT (8:27 a.m. EDT)

T+plus 44 minutes. Centaur is beginning to reorient itself to the position needed for the second burn, which is scheduled to begin in about five minutes.

1223 GMT (8:23 a.m. EDT)

T+plus 40 minutes. The upcoming engine firing will occur over the southern Indian Ocean.

1220 GMT (8:20 a.m. EDT)

T+plus 37 minutes. The vehicle is flying above the Cape of Good Hope along the southern tip of Africa. Centaur systems still look good.

1218 GMT (8:18 a.m. EDT)

T+plus 35 minutes. Initial pad inspections have begun by the inspection team.

1212 GMT (8:12 a.m. EDT)

T+plus 29 minutes. No problems are being reported with systems aboard the Centaur.

1206 GMT (8:06 a.m. EDT)

T+plus 23 minutes, 20 seconds. Centaur is flying 102 nautical miles above Earth some 4,095 miles downrange from the Cape.

1203 GMT (8:03 a.m. EDT)

T+plus 20 minutes.

1200 GMT (8:00 a.m. EDT)

T+plus 17 minutes. Tank pressures and battery voltages on the Centaur are reported normal as the coast mode continues.

1156 GMT (7:56 a.m. EDT)

T+plus 13 minutes, 50 seconds. MECO 1. Centaur's main engine has cut off following its first burn this morning. The rocket will coast in this preliminary orbit for 35 minutes or so before the RL10 is reignited to propel MRO out of Earth orbit.

1155 GMT (7:55 a.m. EDT)

T+plus 12 minutes, 30 seconds. Centaur is still operating normally. The stage will be reaching an initial parking orbit at the completion of this engine firing.

1155 GMT (7:55 a.m. EDT)

T+plus 12 minutes. NASA's Tracking and Data Relay Satellite System is receiving live telemetry from Centaur.

1153 GMT (7:53 a.m. EDT)

T+plus 10 minutes, 30 seconds. Just over three minutes remaining in this first of two burns by Centaur.

1152 GMT (7:52 a.m. EDT)

T+plus 9 minutes, 50 seconds. The Antigua Island tracking station has acquired the rocket's signal.

1152 GMT (7:52 a.m. EDT)

T+plus 9 minutes, 40 seconds. RL10 continues to fire normally.

1151 GMT (7:51 a.m. EDT)

T+plus 8 minutes, 55 seconds. The rocket is 123 nautical miles in altitude, 1,130 nautical miles downrange from the launch and traveling at 13,600 mph.

1151 GMT (7:51 a.m. EDT)

T+plus 8 minutes. The Pratt & Whitney RL10 engine is burning a mixture of liquid oxygen and liquid hydrogen fuel.

1150 GMT (7:50 a.m. EDT)

T+plus 7 minutes, 15 seconds. The rocket is 117 nautical miles in altitude, 797 nautical miles downrange from the launch and traveling at 12,600 mph.

1150 GMT (7:50 a.m. EDT)

T+plus 7 minutes. The vehicle is accelerating at 4.8 g's.

1149 GMT (7:49 a.m. EDT)

T+plus 6 minutes, 5 seconds. Centaur engine performance looks good.

1148 GMT (7:48 a.m. EDT)

T+plus 5 minutes, 30 seconds. The rocket is 358 miles east of the launch pad as Centaur begins its first firing of this launch.

1147 GMT (7:47 a.m. EDT)

T+plus 4 minutes, 45 seconds. The four-meter nose cone encapsulating the MRO spacecraft atop the Atlas 5 rocket has separated.

1147 GMT (7:47 a.m. EDT)

T+plus 4 minutes, 22 seconds. Centaur's RL10 main engine has ignited!

1147 GMT (7:47 a.m. EDT)

T+plus 4 minutes, 15 seconds. The first stage has been jettisoned!

1147 GMT (7:47 a.m. EDT)

T+plus 4 minutes, 5 seconds. Main engine cutoff confirmed.

1146 GMT (7:46 a.m. EDT)

T+plus 3 minutes, 35 seconds. The main engine is ramping its throttle setting to keep a constant acceleration level of 5 g's.

1146 GMT (7:46 a.m. EDT)

T+plus 3 minutes. The Atlas 5 is powering to space on the Russian-designed RD-180 first stage main engine.

1145 GMT (7:45 a.m. EDT)

T+plus 2 minutes. First stage continues to fire normally.

1144 GMT (7:44 a.m. EDT)

T+plus 60 seconds. A beautiful ascent into a clear Florida morning sky.

1143 GMT (7:43 a.m. EDT)

T+plus 35 seconds. Good engine performance.

1143 GMT (7:43 a.m. EDT)

T+plus 30 seconds. Atlas 5 has accomplished its roll and pitch maneuvers to achieve the proper profile for minimizing aerodynamic loads.

1143 GMT (7:43 a.m. EDT)

T+plus 15 seconds. The 19-story Lockheed Martin rocket has cleared the launch pad tower on the thrust of its RD-180 main engine roaring at full throttle.

1143 GMT (7:43 a.m. EDT)

LIFTOFF! Liftoff of the first interplanetary Atlas 5 rocket, launching NASA's Mars Reconnaissance Orbiter to take the next step in exploring our neighboring world.

1142 GMT (7:42 a.m. EDT)

T-minus 20 seconds. "Go Atlas," "Go Centaur" called by launch team, verifying all systems are ready.

1142 GMT (7:42 a.m. EDT)

T-minus 1 minute. Mars Reconnaissance Orbiter is ready to launch on its 310-million-mile, seven-month voyage to the Red Planet.

1141 GMT (7:41 a.m. EDT)

T-minus 90 seconds. Launch control system is enabled. The Flight Termination System has been armed.

1141 GMT (7:41 a.m. EDT)

T-minus 1 minute, 45 seconds. The automatic computer sequencer is in control of all the critical events through liftoff.

1141 GMT (7:41 a.m. EDT)

T-minus 2 minutes. The Atlas first stage and Centaur upper stage are now switching to internal power. Liquid oxygen and liquid hydrogen topping for Centaur will be stopped in 10 seconds.

1140 GMT (7:40 a.m. EDT)

T-minus 2 minutes, 45 seconds. The Flight Termination System has switched to internal power.

1140 GMT (7:40 a.m. EDT)

T-minus 3 minutes. The Atlas first stage liquid oxygen replenishment is being secured so the tank can be pressurized for flight. Also, the RP-1 tank is being pressurized to flight level.

1139 GMT (7:39 a.m. EDT)

T-minus 3 minutes, 30 seconds. The Mars Reconnaissance Orbiter spacecraft has completed its switch from ground-fed power to internal batteries for flight.

1139 GMT (7:39 a.m. EDT)

T-minus 3 minutes, 45 seconds. Ground pyrotechnics have been enabled.

1139 GMT (7:39 a.m. EDT)

T-minus 4 minutes and counting. The final phase of this morning's countdown has begun for the launch of Lockheed Martin Atlas 5 and the Mars Reconnaissance Orbiter!

1138 GMT (7:38 a.m. EDT)

The countdown will be coming out of this hold point in one minute.

1137 GMT (7:37 a.m. EDT)

Launch director Jerry Jamison has given his "go" to resume the countdown for blastoff at 7:43 a.m. EDT.

1136 GMT (7:36 a.m. EDT)

The launch team has being polled by launch conductor Ed Christiansen in the Atlas Spaceflight Operations Center. Everyone reported "go" status for continuing the countdown.

1133 GMT (7:33 a.m. EDT)

NASA launch manager Chuck Dovale has polled the agency oversight team. There are no problems being reported with the Atlas 5, MRO spacecraft or Range. "NASA team is ready," he announced.

1131 GMT (7:31 a.m. EDT)

In about 5 minutes, the launch team will be polled to verify readiness to resume the countdown for liftoff at 7:43 a.m. EDT.

1129 GMT (7:29 a.m. EDT)

T-minus 4 minutes and holding. The countdown has entered this final 10-minute hold.

1127 GMT (7:27 a.m. EDT)

The RD-180 main engine fuel-fill sequence is now complete. Also, the first stage liquid oxygen tank has reached flight level.

1124 GMT (7:24 a.m. EDT)

Launch weather officer Clay Flinn just briefed mission managers on the expected conditions for liftoff time. Winds are light, skies are mostly clear and temperatures are in the low 80s F. All weather conditions are "go" for launch.

1122 GMT (7:22 a.m. EDT)

The latest guidance and steering data have been loaded into the rocket's flight computer based on today's upper level wind conditions.

1117 GMT (7:17 a.m. EDT)

The fuel-fill sequence for the first stage main engine is commencing.

1112 GMT (7:12 a.m. EDT)

There are no significant problems being talked about by the launch team, weather remains beautiful and liftoff is still targeted for the opening of today's two-hour window at 7:43 a.m. EDT.

1107 GMT (7:07 a.m. EDT)

The Centaur liquid oxygen and liquid hydrogen tanks have been reported at flight level.

1103 GMT (7:03 a.m. EDT)

T-minus 30 minutes and counting. The countdown clocks are heading to the T-minus 4 minute mark where a planned 10-minute hold will occur. Launch remains set for 7:43 a.m. EDT.

1101 GMT (7:01 a.m. EDT)

The rocket's "pogo" suppressor has been charged for launch. This energy absorption device aboard is used to damp out oscillations.

1053 GMT (6:53 a.m. EDT)

Final checks of the flight termination system are starting. This system would be used to destroy the rocket if the vehicle experienced a major problem during ascent.

1052 GMT (6:52 a.m. EDT)

Fast-filling of the first stage liquid oxygen tank has been completed. Topping mode is now underway.

1049 GMT (6:49 a.m. EDT)

The liquid hydrogen tank in the Centaur upper stage has just reached 97 percent full. Topping is now beginning.

1043 GMT (6:43 a.m. EDT)

Launch is just 60 minutes away now. Everything is going very well in this morning's countdown. The first stage liquid oxygen tank is 80 percent full, Centaur liquid hydrogen tank is reached the 60 percent mark and the Centaur oxygen tank is already fully loaded.

1039 GMT (6:39 a.m. EDT)

The first stage liquid oxygen tank is now 70 percent full.

1038 GMT (6:38 a.m. EDT)

The flight control final preparations are starting.

1037 GMT (6:37 a.m. EDT)

The Centaur liquid hydrogen tank has reached the 20 percent level. The cryogenic propellant will be consumed with liquid oxygen by the stage's Pratt & Whitney-made RL10 engine that gives Mars Reconnaissance Orbiter the needed push to leave Earth orbit on the way to the Red Planet.

1033 GMT (6:33 a.m. EDT)

The Centaur engine chilldown has been initiated.

1030 GMT (6:30 a.m. EDT)

Chilldown of the liquid hydrogen system is now complete, allowing the super-cold fuel to begin filling the Centaur upper stage via computer control. Yesterday's software snag that prevented the fueling has been resolved.

1030 GMT (6:30 a.m. EDT)

First stage liquid oxygen tank is now half full. Chilled to Minus-298 degrees F, the liquid oxygen will be used with RP-1 kerosene by the RD-180 main engine on the first stage during the initial four minutes of flight today.

1025 GMT (6:25 a.m. EDT)

The first stage's bronze skin is icing over as the super-cold liquid oxygen continues to flow into the vehicle. The tank is 40 percent full.

1021 GMT (6:21 a.m. EDT)

The Centaur liquid oyxgen tank has reached flight level.

1014 GMT (6:14 a.m. EDT)

The first rays of sun are beginning to creep over the horizon as daybreak approaches. The Centaur liquid oxygen tank has now reached the 95 percent level. Topping is starting. Also, ten percent of the first stage liquid oxygen tank has been filled so far in that separate operation.

1008 GMT (6:08 a.m. EDT)

The chilldown conditioning of liquid hydrogen propellant lines at Complex 41 is now starting to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket.

During yesterday's countdown, a problem loading the liquid hydrogen in both the computer-controlled and manual modes forced the launch attempt to be scrubbed. Engineers traced the glitch to a hangup in the software that stemmed from an overnight test on the propellant loading sensors. The test, which was done following a lightning strike 0.6-of-a-mile the launch pad to ensure there were no problems from that event, simulated the sensors were wet and the tank was full. When the actual filling of the rocket was supposed to start, however, the software prevented the fueling operation because it thought the tank was already full. The software has since been reset and engineers don't expect any problems today.

1004 GMT (6:04 a.m. EDT)

The Centaur liquid oxygen tank is now 60 percent full.

1002 GMT (6:02 a.m. EDT)

The chilldown conditioning of the systems for the first stage liquid oxygen tank have been completed. And a "go" has been given to begin pumping super-cold liquid oxygen into the Atlas 5's first stage. The Atlas liquid oxygen tank is the largest tank to be filled today.

The propellant for the first stage -- the RP-1 kerosene -- was loaded aboard the rocket during an earlier practice countdown dress rehearsal.

0955 GMT (5:55 a.m. EDT)

The Centaur liquid oxygen tank is now 20 percent full.

0947 GMT (5:47 a.m. EDT)

Following the thermal conditioning of the transfer pipes, Centaur liquid oxygen tanking operations have begun at Cape Canaveral's Complex 41.

The liquid oxygen -- chilled to Minus-298 degrees F -- will be consumed during the launch by the Centaur's single RL10 engine along with liquid hydrogen to be pumped into the stage a little later in the countdown. The high-energy Centaur will perform two firings today to propel the MRO spacecraft on its way to Mars.

0943 GMT (5:43 a.m. EDT)

Liftoff is now two hours away. Weather is fine, there are no technical problems being reported and the countdown is running on time.

0941 GMT (5:41 a.m. EDT)

The Centaur liquid oxygen pad storage area has been prepped. The next step is conditioning the transfer lines, which is now beginning to prepare the plumbing for flowing the cryogenic oxidizer.

0933 GMT (5:33 a.m. EDT)

Chilldown thermal conditioning of the mobile launch platform upon which the rocket stands is beginning. This is meant to ease the shock on equipment when supercold cryogenic propellants start flowing into the rocket a short time from now.

0933 GMT (5:33 a.m. EDT)

T-minus 120 minutes and counting! This morning's countdown is proceeding smoothly and on schedule for liftoff of the Mars Reconnaissance Orbiter at 7:43 a.m. EDT. Clocks have one more built-in hold planned at T-minus 4 minutes. That pause will last 10 minutes, giving the launch team one last chance to catch up on work running late or deal with any problems.

0929 GMT (5:29 a.m. EDT)

All console operators in the Atlas Spaceflight Operations Center reported a "ready" status during the pre-fueling poll just completed by the launch conductor.

0926 GMT (5:26 a.m. EDT)

The Lockheed Martin launch conductor is briefing his Atlas launch team on countdown procedures before clocks enter into the busy final two hours.

0922 GMT (5:22 a.m. EDT)

Weather conditions are beautiful this morning at the Cape, which is a stark contrast to yesterday when heavy thunderstorms rumbling through the area and delayed the countdown. The Atlas 5 sits beneath a star-filled sky that is offering ideal viewing of today's Perseid meteor shower.

0916 GMT (5:16 a.m. EDT)

Coming up in about 10 minutes, the launch team will receive their pre-flight briefing. That will be followed by a readiness poll to verify all systems are ready to begin fueling the vehicle.

0908 GMT (5:08 a.m. EDT)

Today's launch window extends two hours from 7:43 to 9:43 a.m. EDT. However, there will be two brief periods in which liftoff cannot occur because the rocket's trajectory would take it too close another object already in space. Those Collision Avoidance blackout periods, or COLAs, are 7:57 to 8:02 a.m. and 9:33 to 9:38 a.m. EDT.

0903 GMT (5:03 a.m. EDT)

T-minus 120 minutes and holding. Countdown clocks have just gone into the planned half-hour built-in hold. Launch of the Atlas 5 rocket remains on target for 7:43 a.m. EDT this morning.

0900 GMT (5:00 a.m. EDT)

The launch pad area has been cleared off all workers. But a warning horn is being sounded in case there is anyone within the danger zone. The hazardous operation of fueling the rocket will be getting underway within the hour.

0848 GMT (4:48 a.m. EDT)

Range Safety is performing hold-fire checks. This ensures safety officers will have the capability of halting the countdown if a problem occurs.

0743 GMT (3:43 a.m. EDT)

This morning's countdown is now entering the final four hours.

0642 GMT (2:42 a.m. EDT)

Atlas first stage liquid oxygen system preps have been completed. And the "go" has been given for chilldown thermal conditioning of the Atlas liquid oxygen storage area. This is the early precursor to pumping the super-cold oxidizer into the vehicle a couple of hours from now.

0630 GMT (2:30 a.m. EDT)

This is a gallery of Lockheed Martin photos showing the Atlas 5 rocket's nighttime from the Vertical Integration Facility assembly building to the Complex 41 launch pad Wednesday night and daytime views of the vehicle during Thursday's post-scrub countdown recycle. See the images here.

0623 GMT (2:23 a.m. EDT)

Flight control preps have been completed and an operational test of the system is now beginning. A short time ago, the Centaur liquid oxygen system preps were finished in advance of re-fueling the vehicle later today.

0530 GMT (1:30 a.m. EDT)

The Lockheed Martin Atlas launch team is counting down this morning in hopes of dispatching Mars Reconnaissance Orbiter from Earth a little more than six hours from now. An official explanation of how yesterday's liquid hydrogen fueling system problem was fixed hasn't been announced. But clocks are ticking down and preparations are well underway at Complex 41 for liftoff of the Atlas 5 rocket at 7:43 a.m. EDT today.


Launch of the Mars Reconnaissance Orbiter has been officially reset for Friday morning. The launch team will start a fresh countdown this evening, leading to liftoff at 7:43 a.m. EDT (1143 GMT).

1630 GMT (12:30 p.m. EDT)

A detailed look at the launch weather forecast for tomorrow is available here.

1318 GMT (9:18 a.m. EDT)

The Atlas 5 launch team knew what happened but not the cause of this morning's liquid hydrogen fueling problem, prompting the countdown to be scrubbed to further investigate the trouble before trying to boost NASA's Mars Reconnaissance Orbiter on its way to the Red Planet.

"We had gotten liquid oxygen loaded into both (Atlas and Centaur) stages, and as we were getting into automatic loading of liquid hydrogen into the Centaur we had the propellant load system showing that the sensors were dry when some of the screens and the data that we were getting was showing wet. So we had a discrepancy there," explained NASA launch manager Chuck Dovale.

"We backed out of that and went into a troubleshooting mode. (It) wasn't really clear what the cause was. One option we were going to do was override the automatic software and load manually just to a percentage (of the tank level) to see if our troubleshooting steps were heading in the right direction. Subsequent to that, additional software then locked us out of that manual loading.

"So we got ourselves into a condition where we were not quite sure what the cause was and we felt that we didn't have enough time in the window to pursue it any further. So we are currently in a detanking mode and we'll continue troubleshooting and hopefully resolve that and be able to attempt tomorrow."

The rocket will remain on the launch pad as the team presses ahead with a 24-hour countdown recycle for liftoff at 7:43 a.m. EDT (1143 GMT), if the hydrogen system issue can be fixed in time.

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