BY JUSTIN RAY

Follow the countdown and launch of the ULA Atlas 5 rocket with the Air Force's Space Test Program 1 mission featuring six experimental satellites. Reload this page for the latest on the launch.

Additional coverage for subscribers:
VIDEO: WIDESCREEN LAUNCH MOVIE FROM PRESS SITE PLAY
VIDEO: THE ATLAS 5 ROCKET BLASTS OFF WITH STP 1 PLAY
VIDEO: NEWS BRIEFING ON THE STP 1 MISSION PAYLOADS PLAY
VIDEO: WATCH THE PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: ATLAS 5 ROCKET ROLLED TO LAUNCH PAD PLAY
VIDEO: TIME-LAPSE MOVIE FROM WEDNESDAY'S ROLLOUT PLAY
VIDEO: FOOTAGE FROM PRE-FLIGHT PREPARATIONS PLAY
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0440 GMT (11:40 p.m. EST Thurs.)

Some images of tonight's launch from the Kennedy Space Center press site are available here.

0430 GMT (11:30 p.m. EST Thurs.)

"This was our ninth successful Atlas 5 launch and first ULA Atlas launch, but more importantly, it was the first EELV Atlas launch for the Air Force," said Michael Gass, ULA president and chief executive officer. "This is a proud moment in our company's history and a significant step forward in providing our nation assured access to space using the most cost-effective means possible."

"STP 1 required an extraordinary level of coordination and innovation to achieve the mission requirements," said Jim Sponnick, ULA vice president of Atlas programs. "One of those innovations was the mission design to achieve the two mission orbits, which was enabled by the development of a very flexible new guidance design. The fact that the Atlas system performed so well tonight in delivering the six satellites to their prescribed orbits is a tribute to the teamwork between our Air Force customer, the Space Development & Test Wing, and men and women of the ULA team, including our suppliers from around the world."

0416 GMT (11:16 p.m. EST Thurs.)

T+plus 66 minutes, 5 seconds. FALCONSAT 3 RELEASED! The U.S. Air Force Academy's FalconSat 3 spacecraft has been released into orbit, completing tonight's launch of the Atlas 5 rocket.

This is the 80th consecutive successful launch for the Atlas rocket family dating back to 1993.

FalconSat 3 was developed to give Academy's cadets hands-on experience in designing and building a real satellite. The 119-pound craft carries five military scientific experiments, including the Flat Plasma Spectrometer to characterize the effects of charged particles on the formation, propagation and decay of ionospheric plasma bubbles; the Plasma Local Anomalous Noise Element to identify spacecraft-induced plasma turbulence and the Micropropulsion Attitude Control System featuring a low-thrust, electric-pulsed plasma system with a thrust of 150 micro-Newtons. Technical pieces of the satellite -- a shock ring to test vibration suppression and a gravity gradient boom -- round out the experiments.

0414 GMT (11:14 p.m. EST Thurs.)

T+plus 64 minutes. Deploy of the final payload is about two minutes away.

0411 GMT (11:11 p.m. EST Thurs.)

T+plus 61 minutes, 43 seconds. CFESAT RELEASED! The Cibola Flight Experiment Satellite has separated from the payload ring.

This Los Alamos National Laboratory-led demonstration mission will put eight technologies to the test, such as a new power system, inflatable antennas, deployable booms and a high-density Li-Ion battery pack comprised of AA batteries. The 350-pound craft has a supercomputer onboard to process data for refined answers rather than downlinking all raw data to Earth. And the flight computer can be reprogrammed in space.

"What's really exciting is that after Cibola validates the hardware for spaceflight, we can change the processing after the satellite is in orbit. The future systems will evolve to meet changing requirements, rather than our having to send up an entirely new satellite for each changing mission," said Diane Roussel-Dupre, the CFE project leader.

The science objectives focus on the ionosphere and the effects on communications.

0410 GMT (11:10 p.m. EST Thurs.)

T+plus 60 minutes. Centaur is rolling into position for CFESat deploy.

0408 GMT (11:08 p.m. EST Thurs.)

T+plus 58 minutes. About four minutes until the next release.

0406 GMT (11:06 p.m. EST Thurs.)

T+plus 56 minutes, 41 seconds. STPSAT 1 SEPARATION! Confirmation has been received of STPSat 1 release from the launch vehicle.

This 345-pound Space Test Program satellite carries two complex experiments -- the Spatial Heterodyne Imager for Mesospheric Radicals (SHIMMER) high-resolution ultraviolet spectrometer that will image the Earth's atmosphere and the Computerized Ionospheric Tomography Receiver in Space (CITRIS) for atmospheric electron counting and radio frequency effects.

0401 GMT (11:01 p.m. EST Thurs.)

T+plus 51 minutes. Now five minutes from release of the next payload from the Evolved Expendable Launch Vehicle Secondary Payload Adapter, or ESPA ring.

0358 GMT (10:58 p.m. EST Thurs.)

T+plus 48 minutes, 21 seconds. MECO 3. The Centaur's Pratt & Whitney RL10 engine has shut down as expected to complete the powered phase of tonight's launch.

0357 GMT (10:57 p.m. EST Thurs.)

T+plus 47 minutes. Good chamber pressure. This burn will put the rocket in a circular orbit 348 miles high with an inclination of 35.4 degrees.

0356 GMT (10:56 p.m. EST Thurs.)

T+plus 46 minutes, 27 seconds. Centaur ignition! The upper stage is beginning its third firing of the night, the most ever for an Atlas 5 mission.

0356 GMT (10:56 p.m. EST Thurs.)

T+plus 46 minutes, 17 seconds. Fuel and oxidizer systems have begun the the pre-ignition preps.

0349 GMT (10:49 p.m. EST Thurs.)

T+plus 39 minutes. The vehicle is coasting over the Indian Ocean. The reorientation to the proper position for the upcoming burn is underway.

0346 GMT (10:46 p.m. EST Thurs.)

T+plus 36 minutes. Centaur is coasting in this orbit. The next burn is 10 minutes away.

0344 GMT (10:44 p.m. EST Thurs.)

T+plus 34 minutes, 30 seconds. MECO 2. The second cutoff of the Centaur engine is confirmed. The rocket has entered a so-called "fast transfer orbit" sequence to travel from the initial satellite deployment orbit to the orbit for release of the second batch of payloads. This intermediate orbit is designed to have a low point of 247 miles, a high point of 2,135 miles and inclination of 44 degrees.

0343 GMT (10:43 p.m. EST Thurs.)

T+plus 33 minutes, 35 seconds. Good performance reported.

0343 GMT (10:43 p.m. EST Thurs.)

T+plus 33 minutes, 7 seconds. The RL10 engine is up and burning again.

0341 GMT (10:41 p.m. EST Thurs.)

T+plus 31 minutes. Now two minutes from ignition. A map showing the ground track is available here.

0335 GMT (10:35 p.m. EST Thurs.)

T+plus 25 minutes. Coming up in about eight minutes, the Centaur engine will be restarted for a two-step process to reach an entirely different orbit for deploying the other three satellite payloads.

0332 GMT (10:32 p.m. EST Thurs.)

T+plus 22 minutes, 14 seconds. MIDSTAR 1 RELEASED! The U.S. Naval Academy's Midshipman Space Technology Applications Research Satellite 1 is separated from the payload adapter ring on the rocket.

The 265-pound MidSTAR 1 houses four experiments -- the military's Internet Communications Satellite (ICSat) and Configurable Fault Tolerant Processor (CFTP) space-based computer tests, a payload called Eclipse to test electrochromic membranes in space and the Microdosimeter Instrument for the USNA Department of Aerospace Engineering under the sponsorship of the National Space Biomedical Research Institute.

"We intend for MidSTAR 1 to be the first of a continuing line of satellites designed and built with significant Midshipman involvement," said Prof. Billy Smith, MidSTAR 1 project manager and director of the USNA Small Satellite Program in the Department of Aerospace Engineering. "Reliably delivering inexpensive satellites for DoD payloads, at the same time giving our future Navy and Marine Corps officers' direct professional-level space experience, makes us one of the best bargains in the military space community."

0328 GMT (10:28 p.m. EST Thurs.)

T+plus 18 minutes, 25 seconds. Centaur is now rolling to the orientation for releasing the next payload.

0328 GMT (10:28 p.m. EST Thurs.)

T+plus 18 minutes. ORBITAL EXPRESS DEPLOYED! Orbital Express in-space refueling demonstration mission consisting of the Autonomous Space Transfer and Robotic Orbiter, or ASTRO, prototype servicing satellite and the NextSat serviceable spacecraft has been released from the Centaur upper stage. The two craft, weighing 2,900 pounds, were joined together for launch.

The Defense Advanced Research Projects Agency (DARPA) mission will test the ability of robotic refueling and servicing satellites in space. Such a capability could extend the lives of government and commercial spacecraft.

0325 GMT (10:25 p.m. EST Thurs.)

T+plus 15 minutes. Centaur is reorienting itself following the first burn to the payload release position.

0324 GMT (10:24 p.m. EST Thurs.)

T+plus 14 minutes, 18 seconds. MECO 1. Centaur's main engine has shut down following its first burn tonight. Deployment of the first payload is about four minutes away.

0322 GMT (10:22 p.m. EST Thurs.)

T+plus 12 minutes, 55 seconds. No problems reported with the RL10 engine or Centaur systems. The rocket is headed for a 306-mile circular orbit inclined 46 degrees to the equator.

0321 GMT (10:21 p.m. EST Thurs.)

T+plus 11 minutes, 45 seconds. The rocket is 263 miles above Earth, 1,700 miles northeast of the launch pad.

0320 GMT (10:20 p.m. EST Thurs.)

T+plus 10 minutes, 45 seconds. The vehicle is flying right on the planned track.

0320 GMT (10:20 p.m. EST Thurs.)

T+plus 10 minutes, 30 seconds. About four minutes left in this Centaur burn.

0319 GMT (10:19 p.m. EST Thurs.)

T+plus 9 minutes, 30 seconds. The rocket is 235 miles in altitude, 1,100 miles northeast of the launch pad and traveling at 12,500 mph.

0317 GMT (10:17 p.m. EST Thurs.)

T+plus 7 minutes, 50 seconds. The rocket is 205 miles in altitude and traveling at 11,870 mph.

0316 GMT (10:16 p.m. EST Thurs.)

T+plus 6 minutes, 50 seconds. Centaur engine pressures are stable as the motor continues to burn well.

0315 GMT (10:15 p.m. EST Thurs.)

T+plus 5 minutes, 30 seconds. Vehicle performance reported normal.

0314 GMT (10:14 p.m. EST Thurs.)

T+plus 4 minutes, 35 seconds. The two-halves of the Atlas 5 rocket nose cone encapsulating the spacecraft have separated.

0314 GMT (10:14 p.m. EST Thurs.)

T+plus 4 minutes, 25 seconds. Centaur's RL10 main engine has ignited! Full thrust reported on the RL10 powerplant.

0314 GMT (10:14 p.m. EST Thurs.)

T+plus 4 minutes, 15 seconds. Main engine cutoff confirmed. And the first stage has been jettisoned!

0312 GMT (10:12 p.m. EST Thurs.)

T+plus 2 minutes, 45 seconds. The RD-180 main engine continues to fire. The rocket is 23 miles in altitude, 36 miles dowrange from the launch pad and traveling at 4,188 mph.

0312 GMT (10:12 p.m. EST Thurs.)

T+plus 2 minutes, 15 seconds. First stage continues to fire normally. No problems reported.

0311 GMT (10:11 p.m. EST Thurs.)

T+plus 87 seconds. The vehicle has broken the sound barrier.

0311 GMT (10:11 p.m. EST Thurs.)

T+plus 60 seconds.

0310 GMT (10:10 p.m. EST Thurs.)

T+plus 30 seconds. The 19-story rocket is roaring into the night on the thrust of its RD-180 main engine. Good engine performance reported.

0310 GMT (10:10 p.m. EST Thurs.)

LIFTOFF! Liftoff of the Atlas 5 rocket on its first mission for the United States Air Force, launching six technology demonstration satellites to blaze a trail for future missions in space.

0309 GMT (10:09 p.m. EST Thurs.)

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

0309 GMT (10:09 p.m. EST Thurs.)

T-minus 1 minute and counting.

0308 GMT (10:08 p.m. EST Thurs.)

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

0308 GMT (10:08 p.m. EST Thurs.)

T-minus 1 minute, 50 seconds. The automatic computer sequencer is in control of all the critical events through liftoff.

0308 GMT (10:08 p.m. EST Thurs.)

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 about 10 seconds.

0307 GMT (10:07 p.m. EST Thurs.)

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.

0306 GMT (10:06 p.m. EST Thurs.)

T-minus 3 minutes, 50 seconds. Ground pyrotechnics have been enabled.

0306 GMT (10:06 p.m. EST Thurs.)

T-minus 4 minutes and counting. The final phase of today's countdown has begun for liftoff of the United Launch Alliance Atlas 5 rocket and the Space Test Program 1 mission!

0305 GMT (10:05 p.m. EST Thurs.)

Countdown clocks will resume in one minute. We are now five minutes from launch.

0304 GMT (10:04 p.m. EST Thurs.)

The Range is now "go" for launch. And the Atlas launch director Jerry Jamison has voiced his "go" for liftoff at 10:10 p.m. EST.

0303 GMT (10:03 p.m. EST Thurs.)

The launch team is being re-polled for a "go" to pick up the countdown.

0258 GMT (9:58 p.m. EST Thurs.)

Although the radio frequency interference is no longer being detected, the Range has not yet cleared this issue to allow the launch to proceed.

0257 GMT (9:57 p.m. EST Thurs.)

NEW LAUNCH TIME. Liftoff time has been officially targeted for 10:10 p.m.

0254 GMT (9:54 p.m. EST Thurs.)

HOLD EXTENDED. Liftoff is being retargeted for 10:05 p.m., pending the final OK from the Range.

0254 GMT (9:54 p.m. EST Thurs.)

The Atlas launch director Jerry Jamison reports the Range is still "no go" for liftoff.

0254 GMT (9:54 p.m. EST Thurs.)

The Atlas launch conductor, seated in the Atlas Spaceflight Operations Center four miles from the pad, is being polled the various console operators to ensure all systems are ready to proceed with the countdown.

0252 GMT (9:52 p.m. EST Thurs.)

NEW LAUNCH TIME. Liftoff time has been officially targeted for 10:00 p.m.

0247 GMT (9:47 p.m. EST Thurs.)

The vent valve has proven to be working properly. The first stage has been topped off at flight level.

0245 GMT (9:45 p.m. EST Thurs.)

The radio frequency interference issue gone away, the Range says. The surveillance choppers remain in flight to ensure the restricted area is clear.

0243 GMT (9:43 p.m. EST Thurs.)

The launch team is continuing to do some tests on Atlas liquid oxygen vent valve.

0238 GMT (9:38 p.m. EST Thurs.)

The Range needs to do another sweep of the restricted waters off the coast. That is expected to prevent liftoff before 10 p.m.

0236 GMT (9:36 p.m. EST Thurs.)

Launch has been pushed back another 5 minutes to 9:47 p.m. Work on the Atlas liquid oxygen vent valve appears to have cleared that issue. The Range continues to examine a radio frequency interference issue that could affect the rocket's flight termination system.

0228 GMT (9:28 p.m. EST Thurs.)

NEW LAUNCH TIME. This hold point in the countdown will be extended five additional minutes. So liftoff will slip to no earlier than 9:42 p.m.

In addition to the Range issue under discussion, the launch team wants some time to examine a Atlas first stage liquid oxygen valve.

0225 GMT (9:25 p.m. EST Thurs.)

Range is reporting a no-go status due to a problem. There is no immediate estimate on how long it will take to clear the issue.

0223 GMT (9:23 p.m. EST Thurs.)

T-minus 4 minutes and holding. The countdown has entered the planned 10-minute hold to give the launch team a chance to review all systems before pressing ahead with liftoff.

0222 GMT (9:22 p.m. EST Thurs.)

T-minus 5 minutes. Standing by to go into the final built-in hold.

0221 GMT (9:21 p.m. EST Thurs.)

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

0218 GMT (9:18 p.m. EST Thurs.)

The final planned briefing from the launch weather officer indicates all conditions are acceptable for liftoff.

0217 GMT (9:17 p.m. EST Thurs.)

Twenty minutes to go. All remains "go" for an on-time launch tonight.

0211 GMT (9:11 p.m. EST Thurs.)

The fuel-fill sequence is starting to ready the Russian-designed RD-180 first stage main engine.

0207 GMT (9:07 p.m. EST Thurs.)

Now 30 minutes to launch.

0206 GMT (9:06 p.m. EST Thurs.)

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

0157 GMT (8:57 p.m. EST Thurs.)

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. Liftoff of Atlas 5 with the STP 1 mission remains set for 9:37 p.m. EST.

0152 GMT (8:52 p.m. EST Thurs.)

The rocket is fueled and ready for launch. All three cryogenic tanks are in topping mode.

0147 GMT (8:47 p.m. EST Thurs.)

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

0144 GMT (8:44 p.m. EST Thurs.)

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

0140 GMT (8:40 p.m. EST Thurs.)

Eighty percent of the Centaur liquid hydrogen tank has been filled so far.

0137 GMT (8:37 p.m. EST Thurs.)

Launch is now just 60 minutes away. The countdown is being controlled from the Atlas Spaceflight Operations Center, or ASOC, located about four miles south of the Complex 41 pad. There are no technical problems being reported by the launch team and weather conditions are favorable for liftoff this evening.

0135 GMT (8:35 p.m. EST Thurs.)

The Centaur engine chilldown is being initiated. And the flight control final preparations are starting.

0134 GMT (8:34 p.m. EST Thurs.)

The Centaur liquid hydrogen tank is now above the 40 percent level. The cryogenic propellant will be consumed with liquid oxygen by the stage's Pratt & Whitney-made RL10 engine.

0128 GMT (8:28 p.m. EST Thurs.)

First stage liquid oxygen tank is now 60 percent 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 tonight. The 25,000 gallons of RP-1 were loaded into the rocket yesterday afternoon.

0124 GMT (8:24 p.m. EST Thurs.)

The chilldown conditioning of liquid hydrogen propellant lines at Complex 41 has been accomplished to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket. Loading of the Centaur with about 13,000 gallons of the cryogenic propellant is starting now.

0115 GMT (8:15 p.m. EST Thurs.)

The Centaur liquid oyxgen tank has reached flight level. The first stage liquid oxygen tank is approaching one-third percent full.

0112 GMT (8:12 p.m. EST Thurs.)

Twenty percent of the first stage liquid oxygen tank has been filled so far. The stage's bronze skin is icing over as the supercold liquid oxygen flows into the vehicle.

Meanwhile, the Centaur liquid oxygen tank reached the 95 percent level. The topping off process is starting.

0107 GMT (8:07 p.m. EST Thurs.)

Now 90 minutes to launch.

0057 GMT (7:57 p.m. EST Thurs.)

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 tonight. It holds about 50,000 gallons of cryogenic oxidizer for the RD-180 main engine.

0056 GMT (7:56 p.m. EST Thurs.)

The Centaur liquid oxygen tank is now 50 percent full.

0049 GMT (7:49 p.m. EST Thurs.)

Twenty percent of the Centaur liquid oxygen tank has been filled so far.

0041 GMT (7:41 p.m. EST Thurs.)

Following the thermal conditioning of the transfer pipes, filling of the Centaur upper stage with more than 4,000 gallons of liquid oxygen has 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 Centaur will perform three firings tonight to deliver the STP 1 spacecraft into their desired low-Earth orbits.

0033 GMT (7:33 p.m. EST Thurs.)

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.

0028 GMT (7:28 p.m. EST Thurs.)

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.

0027 GMT (7:27 p.m. EST Thurs.)

T-minus 120 minutes and counting! Countdown clocks are running again for launch of the Atlas 5 rocket and the Space Test Program 1 mission. 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.

0022 GMT (7:22 p.m. EST Thurs.)

All console operators in the Atlas Spaceflight Operations Center reported a "ready" status during the pre-fueling poll just completed by the ULA launch conductor. The launch director then gave his 'go' to proceed as well.

0012 GMT (7:12 p.m. EST Thurs.)

Now half way through this scheduled 30-minute hold. Launch team readiness polls in advance of fueling the rocket are coming up in about 10 minutes.

0005 GMT (7:05 p.m. EST Thurs.)

There is one Collision Avoidance, or COLA, periods during today's launch window. A COLA is a block of time in which liftoff cannot occur because the rocket's trajectory would take it too close another object already in space.

The COLA is 10:59:26 to 11:13:38 p.m. EST.

Today's overall window is 9:37 to 11:42 p.m. EST.

2357 GMT (6:57 p.m. EST)

T-minus 2 hours and holding. A planned 30-minute built-in hold for the countdown has just started. This scheduled pause is designed to provide some margin in the countdown timeline to deal with technical issues or recover from work running behind. The count will resume at 7:27 p.m. EST.

Another hold is planned at the T-minus 4 minute point. Launch is still set for 9:37 p.m. EST.

2353 GMT (6:53 p.m. EST)

The word has been given to the launch pad crew to leave Complex 41. The pad must be cleared of all personnel for the start of fueling operations coming up in the next hour.

2350 GMT (6:50 p.m. EST)

A briefing by the launch weather officer reports conditions remain just fine for liftoff. The only issue that will be watched is the ground winds. The limit is 22 knots. A latest check at Complex 41 shows winds of 15 knots.

2345 GMT (6:45 p.m. EST)

Night has fallen along the Space Coast. Countdown activities are marching forward. Range Safety just performed the hold-fire checks. This ensures safety officers will have the capability of halting the countdown if a problem occurs.

2320 GMT (6:20 p.m. EST)

Good evening from the Kennedy Space Center press site as the countdown enters the final three hours to launch. We are located about four miles northwest of the Atlas 5 rocket's Complex 41 launch pad. Skies remain clear, winds are within limits and the countdown is progressing on schedule for a liftoff at 9:37 p.m. EST tonight.

1730 GMT (12:30 p.m. EST)

It is launch day for the Atlas 5 rocket. Weather conditions are beautiful and ground crews are getting ready to start the countdown for tonight's planned 9:37 p.m. EST blastoff.

Clocks start ticking at 2:37 p.m. as the Atlas first stage and Centaur upper stage are scheduled to be powered up to begin standard pre-flight testing and preparations.

At 6:57 p.m., the count will enter a planned 30-minute built-in hold at the T-minus 120 minute mark. This pause gives the launch team the opportunity to catch up on any work running behind the timeline or deal with technical glitches. A poll of team members occurs five minutes before the end of the hold to verify everyone is ready for liquid oxygen and liquid hydrogen fueling.

Chilling of propellant lines and tanks is performed to thermally condition the equipment in preparation for flowing the super-cold fuels. Centaur liquid oxygen loading should begin at about 7:44 p.m., followed by Atlas first stage liquid oxygen and finally Centaur hydrogen fueling.

A final hold is planned at T-minus 4 minutes. This will be a 10-minute hold starting at 9:23 p.m. to conduct readiness polls of senior management, the launch team members, Range and weather. If all elements are deemed "go" for launch, the clock will resume ticking at 9:33 p.m.

Watch this page for play-by-play reports on the countdown throughout the evening!

WEDNESDAY, MARCH 7, 2007

All remains on schedule for Thursday night's launch of the Space Test Program 1 mission aboard an Atlas 5 rocket from Cape Canaveral.

Earlier today, the rocket arrived on the launch pad at Complex 41 and received its load of kerosene fuel for the first stage. A collection of images from the rollout is available here.

At the pre-launch press conference this afternoon, officials expressed their confidence that the unique rocket flight to deploy research payloads in two distinctly separate orbits will work as planned.

"We fully expect that our Atlas 5 system will do an excellent job in delivering the six STP 1 satellites to their two different low-Earth orbits," said Jim Sponnick, United Launch Alliance's vice president for Atlas programs.

Launch day activities will get underway in earnest by mid-afternoon when the countdown clocks start ticking at 2:37 p.m. EST. The subsequent seven hours will be spent testing rocket systems and filling the remaining three propellant tanks on the vehicle with cryogenic fuel.

Liftoff is scheduled for 9:37 p.m. EST, which is the opening of a two-hour, five-minute launch window. If problems prevent an on-time launch, officials have until 11:42 p.m. to get the rocket airborne.

"As always, mission success is our No. 1 priority. The launch team will verify that all systems and mission plans meet our rigorous standards for flight readiness. Only when everything is 100 percent ready will we launch," said Lt. Col. Walter Lauderdale, the Air Force's Atlas program director.

Meteorologists continue to predict an 80 percent chance of good weather for the liftoff.

"Overall, weather conditions look quite favorable for a Thursday night launch," said Lt. Kaleb Nordgren of the Cape's weather squadron.

The weather outlook worsens a bit for the backup launch opportunity on Friday. The launch window that night would run from 9:35 to 11:41 p.m.

1537 GMT (10:37 a.m. EST)

ON THE PAD! The Atlas 5 rocket has arrived at the Complex 41 launch pad for tomorrow night's liftoff.

The next few hours will be spent connecting the mobile launch platform with umbilicals from the pad and performing leak checks on the fuel lines. The "trackmobiles" used in the rollout will disengage from the platform and depart the pad. Loading of the first stage with kerosene fuel is scheduled for 1:35 p.m. this afternoon.

A pre-launch news conference occurs at 4 p.m. today. We'll post an update later this evening.

1507 GMT (10:07 a.m. EST)

ROLLOUT BEGINS! The United Launch Alliance Atlas 5 rocket has started its drive from the 30-story Vertical Integration Facility to the pad at Cape Canaveral's Complex 41. A pair of specially-made "trackmobiles" are pushing the rocket's 1.4-million pound mobile launching platform along rail tracks for this trip.

The two-stage rocket was assembled inside the VIF in preparation for the mission. The Space Test Program 1 payloads were joined together at a nearby processing facility before being delivered to the VIF for mounting atop the Atlas.

The mobile launching platform is what the Atlas 5 sits upon from the time it is stacked in the VIF until the main engine is fired at liftoff. Umbilicals feeding fuel, power and all other lines from the ground to the rocket run through the platform.

The platform is 45 feet wide, 55 feet long and 185 feet tall to the top of the mast, which features a wind damper that holds the rocket steady while exposed to the weather on the pad and routes propellant lines to the Centaur and conditioned air to the payload inside the nose cone.

Two "trackmobiles" transport the rocket the 1,800 feet to the launch pad. Mobile vans are attached to the platform, providing ground communications and equipment for the rocket, command and control and the air purge to the payloads.

The rollout typically takes about a half-hour, reaching a top speed about two miles per hour.

TUESDAY, MARCH 6, 2007

The Atlas 5 rocket's first flight for the U.S. Air Force, set for blastoff Thursday night from Florida, will be an unusually complex ascent to deploy a flock of military research satellites.

Liftoff is scheduled for 9:37 p.m. EST (0237 GMT) from Cape Canaveral's Complex 41. The available launch window extends to 11:42 p.m. EST (0442 GMT), a duration of two hours and five minutes.

The weather forecast calls for scattered low- and high-level clouds, good visibility, temperatures in the mid-60s F, northeasterly winds 12 gusting to 18 knots and the chance of isolated showers. Meteorologists say there is a 20 percent chance that cloud cover or showers could violate the launch rules.

The 19-story rocket will be wheeled out to the launch pad Wednesday morning to undergo final testing and fueling for the mission. The booster currently stands assembled atop a mobile launching platform inside the Vertical Integration Facility. The rollout is scheduled to begin around 10 a.m. and the third-of-a-mile trek should take about a half-hour to complete.

Once in position at the pad, the mobile platform will be locked down, the transporter carriages pulled away and propellant lines hooked up. The key event in the afternoon, starting around 1:30 p.m., will be fueling of the Atlas first stage with its supply of kerosene propellant.

Thursday's countdown begins at 2:37 p.m. when the Atlas 5 is powered up. The process to load the rocket with supercold liquid oxygen and liquid hydrogen starts at 7:44 p.m.

A 10-minute planned built-in hold is scheduled at T-minus 4 minutes to give the launch team a chance to evaluate all systems before going into the final phase of the countdown.

The RD-180 main engine ignites at T-minus 2.7 seconds, roaring to life while computers check to ensure the powerplant's vital signs are healthy prior to releasing the vehicle for flight on the military's Space Test Program 1 mission.

This will be the 9th Atlas 5 launch and the fourth using the 401 configuration, the basic version of the two-stage rocket with no strap-on solid motors.

The first stage fires for four minutes before shutting down and separating. That leaves the hydrogen-fueled Centaur upper stage to ignite for the first of three burns. Shortly after the ignition the no-longer-needed nose cone shrouding the payloads is jettisoned.

The first Centaur burn lasts 10 minutes, achieving a 306-mile circular orbit inclined 46 degrees to the equator. That is the where the Orbital Express payload, which consists of the ASTRO and NextSat spacecraft joined together, and the Naval Academy's MidSTAR 1 satellite are released from the rocket.

Those deployments will be completed about 22 minutes into the flight, allowing Centaur to proceed with an orbital mechanics dance. The RL10 engine re-ignites at T+plus 33 minutes to enter a so-called "fast transfer orbit" sequence that will take the rocket from the initial satellite deployment orbit to an entirely different orbit for release of the second batch of payloads. This second burn by Centaur results in an intermediate orbit with a low point of 247 miles, a high point of 2,135 miles and inclination of 44 degrees.

After coasting in the highly elliptical transfer orbit for about 12 minutes, Centaur completes its third firing -- the most ever for an Atlas 5 mission -- to enter a circular orbit 348 miles high with an inclination of 35.4 degrees to separate the remaining three satellites.

The Space Test Program's STPSat 1 spacecraft, Los Alamos National Laboratory's CFESat and the U.S. Air Force Academy's FalconSat 3 will be released individually over the course of several minutes. The launch should be complete by T+plus 67 minutes.

A successful launch will mark the first time an Atlas 5 has delivered payloads into two completely separate orbits. In the broader picture for the Atlas family of rockets, it would be the 80th consecutive successful mission extending back to 1993.

"I am extremely proud of the hard work and dedication that has gone into the planning and preparation for this mission," said Lt. Col. Carol Welsch, director of the Department of Defense Space Test Program.

"With the support of the entire launch team this mission will prove out many exciting new space technologies and help usher in the responsive space capabilities of the Air Force Space Development & Test Wing."

Watch this page for live updates on Wednesday's rollout to the pad and throughout Thursday night's launch.

MONDAY, MARCH 5, 2007

The early weather forecast for Thursday's ULA Atlas 5 rocket launch from Cape Canaveral is calling for a 70 percent chance of acceptable conditions. Meteorologists will be watching thick clouds and isolated rain showers. See the full forecast here.

Thursday's launch window extends from 9:37 to 11:42 p.m. EST.

The United Launch Alliance rocket will carry six satellites during a complex launch of the Air Force's Space Test Program 1 mission. The payload list is led by the Orbital Express in-space refueling demonstration mission consisting of the Autonomous Space Transfer and Robotic Orbiter, or ASTRO, prototype servicing satellite and the NextSat serviceable spacecraft. Atlas will deploy four auxiliary satellites from the Evolved Expendable Launch Vehicle Secondary Payload Adapter, or ESPA ring, including MidSTAR 1, FalconSat 3, STPSat 1 and CFESat.

The rocket will fly in the 401 vehicle configuration with a four-meter fairing, no solid rocket boosters and a single-engine Centaur upper stage.

MONDAY, FEBRUARY 12, 2007

The next launch of the Atlas 5 rocket is being delayed from February 22 to March 8 in the wake of the recent Sea Launch Zenit 3SL booster failure. The Atlas RD-180 main engine is derived from the Zenit's powerplant. Officials want more time to see if anything uncovered in the Zenit investigation would impact the Atlas engine.

THURSDAY, JANUARY 11, 2007

After a quiet 2006 that saw just two launches and a whole lot of waiting for payloads, the United Launch Alliance Atlas 5 rocket program is preparing for a flurry of flights over the next several months.

Last year began with the successful January dispatch of NASA's New Horizons space probe destined to explore Pluto and the outer reaches of the solar system. A commercial launch of the European ASTRA 1KR television broadcasting satellite followed in April. The Atlas fleet then fell into a lull caused by delays in readying satellites for subsequent flights.

History books will show 2006 as one of the slowest times for Atlas in years.

But 2007 promises to get the new-generation launcher back in action, buoyed by the first wave of missions for the U.S. Air Force.

Read our full story.