NASA's newest communications relay satellite, launched from Cape Canaveral last Wednesday, has begun maneuvering itself towards geosynchronous orbit over the Pacific Ocean.

The Boeing Co. designed and built the Tracking and Data Relay Satellite K for NASA and is controlling the spacecraft during its early days in orbit.

A United Launch Alliance Atlas 5 rocket carried TDRS K into a geosynchronous transfer orbit, an elliptical type of orbit that is the customary drop off point for spacecraft bound for a parking spot about 22,300 miles above Earth. The launcher released the payload into the preliminary orbit with a high point of 22,245 statute miles, low point of 2,680 statute miles and inclination of 25.6 degrees.

From there, Boeing satellite controllers will reduce the inclination and raise the low point to circularize it into a geosynchronous orbit where TDRS K can match Earth's rotation and appear parked at 150 degrees West longitude, the planned location of in-space testing and checkout.

The first of five firings of the satellite's onboard engine was successfully accomplished on Sunday, said John Leuer, the TDRS K program director at Boeing Space and Intelligence Systems.

"TDRS K is performing well on-orbit," he said.

The satellite stood 26 feet tall and weighed over 7,600 pounds at launch, including 3,700 pounds of maneuvering fuel loaded inside the craft. Once fully deployed in space, TDRS K's solar wings will stretch 69 feet tip-to-tip to generate 3,220 watts of power and charge internal nickel-hydrogen batteries.

The primary physical feature of the satellite is two 15-foot-diameter flexible graphite mesh antenna dishes that were folded like taco shells for launch, then successfully sprung into shape once released in orbit.

"The 15 ft diameter Single Access antenna reflectors are now unfurled," Leuer said.

The antennas offer gimbal tracking of targeted spacecraft flying beneath the satellite, providing high-gain communications to the station, Hubble and other craft for vital contacts and data dumps.

After finishing the orbit-raising activities later this week, the spacecraft's full appendages will be deployed, starting with one solar array, then the booms holding the Single Access antennas fold out, the other solar wing extends, the forward Omni swings into place and the space-to-ground antenna is positioned.

Once the satellite undergoes three months of testing at 150 degrees West, NASA will "take the keys" from Boeing and drift the craft to its operational location at 171 degrees West for the start of a 15-year service life later this spring.

"With this launch, NASA has begun the replenishment of our aging space network," said Jeffrey Gramling, NASA's TDRS project manager. "This addition to our current fleet of seven will provide even greater capabilities to a network that has become key to enabling many of NASA's scientific discoveries."

Advancing from the days of ground stations providing sporadic coverage of man's early exploits in space to the creation of an orbiting satellite network for constant communications, the third generation of NASA's tracking stations in the sky roared off the launch pad Wednesday night.

Read our full story.

And see the launch photo gallery.

"ULA and our mission partners are honored to work with the outstanding NASA team and we are proud of the vitally important data relay capabilities that were safely delivered today," said Jim Sponnick, ULA vice president for mission operations.

NASA launch director Tim Dunn has declared today's ascent of the Atlas 5 rocket as a success, deploying the TDRS K spacecraft into its proper orbit around the Earth.

"What a great way to kick off the New Year, with another successful launch from the Easter Range," said Brig. Gen. Anthony Cotton, commander of the 45th Space Wing at Cape Canaveral. "Our manifest is full and strong for the coming year."

T+plus 106 minutes, 17 seconds. SPACECRAFT SEPARATION! The Tracking and Data Relay Satellite K has been released from the Centaur upper stage, completing this evening's launch to replenish NASA's communications network in space!

T+plus 105 minutes, 30 seconds. The vehicle is 10,200 miles above Earth.

T+plus 105 minutes. Spin up to 30 degrees per second is being achieved by the rocket stage.

T+plus 104 minutes. Centaur achieved the proper orbit during its second burn.

T+plus 103 minutes. The vehicle has a reached a geosynchronous transfer orbit, a highly elliptical orbit with one end of the orbit at geosynchronous altitude. This is the typical drop-off point for communications satellites. TDRS K will be left to maneuver itself into a circular perch 22,300 miles above the Pacific.

T+plus 102 minutes. Centaur is turning itself to the proper orientation for releasing the first payload.

T+plus 101 minutes, 30 seconds. MECO 2. Main engine cutoff confirmed. Centaur has completed its second burn of the night!

T+plus 101 minutes, 5 seconds. Centaur's RL10 engine continues a good firing.

T+plus 100 minutes, 50 seconds. The engine is burning well. This is a planned one-minute firing by the Centaur's single Pratt & Whitney Rocketdyne RL10 engine.

T+plus 100 minutes, 32 seconds. Ignition and full thrust! The Centaur's single RL10 engine has re-ignited to accelerate the TDRS payload into the planned deployment orbit.

T+plus 99 minutes. Centaur is getting pressurized again in preparation to re-ignite.

T+plus 98 minutes. The rocket stage is in the proper orientation for the burn.

T+plus 96 minutes. Centaur has despun from its coast configuration.

T+plus 94 minutes. The vehicle is reorienting for the engine firing.

T+plus 93 minutes. Centaur is more than 9,000 miles in altitude as it coasts away from Earth above the Indian Ocean.

T+plus 75 minutes. See our Facebook page for quick images of this evening's launch!

One hour since launch and still 46 minutes left to go in the ascent sequnce. The Atlas 5 rocket will inject the TDRS K communications satellite into a highly elliptical geosynchronous transfer orbit.

T+plus 45 minutes. The flight path took the vehicle over the equatorial Atlantic Ocean before crossing Africa. Here's the planned track map.

T+plus 30 minutes. Check out Spaceflight Now's Facebook page for images from tonight's liftoff.

T+plus 21 minutes. That first burn by Centaur inserted the rocket into an orbit with a high point of 15,445 statute miles, a low point of 114 statute miles and inclination of 26.5 degrees. Those values are right on the mark.

T+plus 19 minutes. The rocket is performing its turn to the proper position for the parking orbit coast.

T+plus 18 minutes, 24 second. MECO 1. Centaur's main engine has shut down following its first burn today, achieving a preliminary orbit around Earth. The rocket will coast in this orbit for about 80 minutes before the RL10 engine re-ignites.

T+plus 17 minutes, 50 seconds. Everything is normal on Centaur and RL10 engine with a half-minute to go in this burn.

T+plus 17 minutes. RL10 engine parameters still look good.

T+plus 16 minutes, 25 seconds. Centaur remains on course and looking good.

T+plus 15 minutes, 55 seconds. The rocket's speed has increased to 18,951 mph.

T+plus 15 minutes, 20 seconds. About three minutes are left in this burn of Centaur.

T+plus 14 minutes, 35 seconds. Centaur has achieved orbital velocity.

T+plus 13 minutes, 50 seconds. RL10 engine performance still reported to be looking good.

T+plus 13 minutes, 40 seconds. Now 116029 miles in altitude, 2,161 miles downrange from the launch pad, traveling at 16,466 mph.

T+plus 12 minutes, 45 seconds. Centaur is 171 miles in altitude, 1,955 miles downrange from the launch pad, traveling at 15,700 mph.

T+plus 11 minutes. The RL10 continues to perform well, burning liquid hydrogen and liquid oxygen propellants.

T+plus 10 minutes, 30 seconds. Now 190 miles in altitude, 1,442 miles downrange from the launch pad, traveling at 13,945 mph.

T+plus 9 minutes, 25 seconds. All systems reported stable as the Centaur fires to reach an initial Earth orbit.

T+plus 8 minutes, 30 seconds. Now 161 miles in altitude, 1,012 miles downrange from the launch pad, traveling at 12,644 mph.

T+plus 7 minutes, 20 seconds. Now 148 miles in altitude, 784 miles downrange from the launch pad, traveling at 12,041 mph.

T+plus 6 minutes, 30 seconds. The first stage delivered the expected performance.

T+plus 6 minutes, 15 seconds. The vehicle tracking right on the proper trajectory.

T+plus 5 minutes, 30 seconds. Now 108 miles in altitude, 445 miles downrange from the launch pad, traveling at 11,354 mph.

T+plus 5 minutes. Centaur engine readings look good as this burn gets underway.

T+plus 4 minutes, 45 seconds. Now 96 miles in altitude, 299 miles downrange from the launch pad, traveling at 11,142 mph.

T+plus 4 minutes, 32 seconds. The two halves of the four-meter-diameter Atlas 5 rocket nose cone encapsulating the spacecraft have separated.

T+plus 4 minutes, 24 seconds. Centaur has ignited! The RL10 engine is up and running at full thrust to power the vehicle into orbit.

T+plus 4 minutes, 13 seconds. The Atlas 5's Common Core Booster has been jettisoned, completing the first stage of flight, and the Centaur upper stage's liquid hydrogen and liquid oxygen systems are being readied for engine start.

T+plus 4 minutes, 5 seconds. BECO. Booster Engine Cutoff is confirmed as the RD-180 powerplant on the first stage completes its burn. Standing by to fire the retro thrusters and separate the spent stage.

T+plus 3 minutes, 45 seconds. Atlas now weighs just a quarter of what it did at liftoff.

T+plus 3 minutes, 20 seconds. The main engine is performing well as the rocket climbs away from the planet.

T+plus 2 minutes, 45 seconds. Reaction control system has been activated.

T+plus 2 minutes, 35 seconds. Atlas continues tracking on course.

T+plus 2 minutes, 20 seconds. Atlas now weighs half of what it did at liftoff.

T+plus 2 minutes, 15 seconds. Vehicle systems looking good.

T+plus 1 minutes, 45 seconds. The RD-180 main engine continues to fire normally, burning a mixture of highly refined kerosene and liquid oxygen.

T+plus 100 seconds. Now passing through the region of maximum aerodynamic pressure on the vehicle as its accelerates through the dense lower atmosphere.

T+plus 85 seconds. All looks good aboard Atlas as it passes Mach 1.

T+plus 60 seconds. One minute into the ascent of NASA's latest communications satellite atop the 19-story-tall Atlas 5 rocket, bound for a geosynchronous transfer orbit tonight.

T+plus 40 seconds. The Atlas 5 is lighting up the night with its thunderous departure on an easterly trajectory from Cape Canaveral.

T+plus 15 seconds. The Atlas 5 rocket has cleared the tower on 860,000 pounds of thrust from the RD-180 main engine. Pitch, yaw and roll maneuvers are underway to put the rocket on the proper heading.

LIFTOFF! Liftoff of Atlas 5 and TDRS K, launching the third generation of NASA's tracking stations in the sky!

T-minus 20 seconds. "Go Atlas" and "Go Centaur" was just called by launch team during a final status check.

T-minus 40 seconds. Centaur's liquid oxygen and liquid hydrogen tanks are stable at flight pressures.

T-minus 55 seconds. Range is green.

T-minus 1 minute. Now 60 seconds away from the latest NASA science-relay satellite taking flight.

T-minus 90 seconds. The rocket's safety system has been armed.

T-minus 1 minute, 45 seconds. Liquid oxygen and liquid hydrogen propellant topping to the Centaur upper stage is being secured.

T-minus 1 minute, 55 seconds. The launch sequencer has been commanded to start.

T-minus 2 minutes. The Atlas first stage and Centaur upper stage are now switching from ground power to internal batteries.

T-minus 2 minutes, 30 seconds. The first stage RP-1 kerosene fuel tank and the liquid oxygen have stepped up to proper flight pressure levels.

T-minus 3 minutes. The Atlas first stage liquid oxygen replenishment is being secured so the tank can be pressurized for launch.

T-minus 3 minutes, 50 seconds. The ground pyrotechnics are enabled.

T-minus 4 minutes and counting. Clocks have resumed for the final minutes of today's countdown to launch the Atlas 5 rocket with NASA's Tracking and Data Relay Satellite.

Standing by to pick up the count.

The TDRS spacecraft is running on internal power for launch.

ULA launch director Lou Mangieri has given his "go" to resume the countdown as scheduled.

Polling of the team by Atlas launch conductor just occurred. All systems are "go" for a liftoff today at 8:48 p.m. EST.

NASA launch director Timm Dunn has polled the agency team. There are NO problems being reported.

Standing by for the final readiness check to be conducted. The launch team will be polled for a "go" or "no go" to proceed with the count.

The TDRS K satellite is switching to internal power for launch.

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The countdown remains on target for liftoff at 8:48 p.m. EST (0148 GMT) when today's 40-minute launch opportunity opens.

The kerosene-fueled first stage will be burn for the first four minutes of flight before separating to allow the cryogenic Centaur upper stage to ignite for a 14-minute initial burn to reach a preliminary parking orbit looping from 114 statute miles to about 15,425 statute miles. The nose cone is jettisoned four-and-a-half minutes after launch.

The rocket settles into a coast across the equatorial Atlantic, Africa, the Indian Ocean before restarting the RL10 upper stage engine 100 minutes into flight for a one-minute burn that accelerates TDRS K to the intended highly elliptical orbit.

The upper satellite is deployed 106 minutes after liftoff into an orbit with an apogee of 22,238 statute miles, perigee of 2,680 statute miles and inclination of 25.9 degrees.

The spacecraft will be operated by Boeing's mission control for maneuvering into a circular geosynchronous orbit in its first 10 days in space, then undergoing deployments of its antennas and solar arrays, a lengthy test period before going into service later in the spring over the Pacific Ocean at 171 degrees West.

Twenty minutes from liftoff. Weather is GO for launch.

Here's a look at some stats about today's mission. This will be:

• The 617th launch for Atlas program since 1957
• The 328th Atlas to occur from Cape Canaveral
• The 206th mission for the Centaur upper stage
• The 183rd use of Centaur by an Atlas rocket
• The 35th launch of an Atlas 5 since 2002
• The 56th Evolved Expendable Launch Vehicle flight
• The 30th Atlas 5 to occur from the Cape
• The 6th nighttime Atlas 5 from the Cape
• The 27th Atlas 5 under United Launch Alliance
• The 23rd 400-series flight of the Atlas 5
• The 15th Atlas 5 to fly in the 401 configuration
• The 8th NASA launch on Atlas 5
• The 11th Tracking and Data Relay Satellite launch
• The 4th TDRS built by Boeing
• The 4th TDRS launched on an Atlas vehicle
• The first Atlas 5 launch for TDRS
• The first Atlas launch of 2013

The first stage liquid oxygen tank and Centaur's liquid oxygen and liquid hydrogen tanks are topped at flight level.

The forecast has improved to 90 percent favorable for the launch window. All conditions are GO at the current time.

T-minus 4 minutes and holding. The countdown has entered the planned 25-minute hold to give the launch team a chance to review all systems before pressing ahead with liftoff.

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

Atlas 5 represents the culmination of evolution stretching back several decades to America's first intercontinental ballistic missile. At the dawn of the space age, boosters named Atlas launched men into orbit during Project Mercury and became a frequent vehicle of choice to haul civil, military and commercial spacecraft to orbit.

Topped with the high-energy Centaur upper stage, Atlas rockets have been used since the 1960s to dispatch ground-breaking missions for NASA, including the Surveyors to the Moon, Mariner flights to Mars, Venus and Mercury, and the Pioneers that were the first to visit Jupiter and beyond.

In its newest era, the Atlas 5 rocket sent the Mars Reconnaissance Orbiter to the red planet in 2005, propelled the New Horizons probe toward Pluto and the solar system's outer fringes in 2006, doubled up with the dual Lunar Reconnaissance Orbiter and LCROSS impactor to the Moon in 2009, hurled Juno to Jupiter in August 2011, dispatched the car-sized Curiosity rover on the Mars Science Lab mission in November 2011, and deployed a pair of harden probes in the heart of Earth's radiation belts last August.

Today marks the 35th flight for Atlas 5, born of the Air Force's competition to develop next-generation Evolved Expendable Launch Vehicles. In its previous 34 missions since debuting in August 2002, the tally shows 11 flights dedicated to the Defense Department, 9 commercial missions with communications spacecraft, seven with spy satellites for the National Reconnaissance Office and seven for NASA.

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

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

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Passing the 90 percent mark on the first stage liquid oxygen tank.

Pre-launch checks of the rocket's safety system have been completed.

Weather odds just jumped up to 80 percent favorable for this evening's launch window.

Now 60 minutes from liftoff. Fueling of the Atlas rocket with cryogenic liquid oxygen and liquid hydrogen is nearly complete as the countdown continues as planned for a liftoff at 8:48 p.m. EST. Weather remains GO and no technical problems are being reported.

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First stage liquid oxygen tank is 60 percent full thus far. 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. The 25,000 gallons of RP-1 were loaded into the rocket after rollout yesterday.

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

Centaur's liquid hydrogen tank is 60 percent full. The cryogenic propellant will be consumed with liquid oxygen by the stage's Pratt & Whitney Rocketdyne-made RL10 engine.

Now 75 minutes till launch of the Tracking and Data Relay Satellite K to keep the International Space Station, Hubble Space Telescope and NASA science spacecraft in constant communications with the ground. There are no technical problems being reported in the countdown and the current weather conditions are green.

The first stage liquid oxygen tank has reached the 30 percent mark.

Chilldown of the liquid hydrogen system has been accomplished. The launch team has received the "go" to begin filling the Centaur upper stage with the supercold fuel.

The first stage liquid oxygen loading is transitioning from slow-fill to fast-fill mode.

After the slight wait to assess that fill-and-drain sensor problem, first stage liquid oxygen loading is underway.

The Centaur engine chilldown sequence is being initiated.

The anomaly team recommends to proceed with the fueling and the countdown tonight. There is a workaround in place to avoid reliance on a pair of sensors that did not give valve open indications as expected. But other data shows the valves themselves did open, it was just a sensor issue.

Centaur liquid oxygen is now at flight level.

The launch team is awaiting recommendations from the anomaly team on the first stage fill-and-drain valve issue.

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

The chilldown conditioning of liquid hydrogen propellant lines at Complex 41 is starting to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket. The Centaur holds about 12,325 gallons of the cryogenic propellant.

Now at 75 percent on Centaur liquid oxygen.

The anomaly team is being brought together to discuss a problem seen with the first stage fill-and-drain valve indications.

Centaur liquid oxygen is 50 percent loaded.

The conditioning of the systems for the first stage liquid oxygen tank have been completed. And a "go" has been given to begin pumping supercold liquid oxygen into the Atlas 5's first stage.

The Common Core Booster stage's liquid oxygen tank is the largest tank to be filled today. It holds 48,745 gallons of cryogenic oxidizer for the RD-180 main engine.

Passing the 20 percent level on the Centaur upper stage's liquid oxygen tank.

NASA says the Tracking and Data Relay Satellite K spacecraft atop the Atlas 5 rocket has been successfully put into its launch configuration. The spacecraft goes to internal power closer to liftoff time.

Filling of the Centaur upper stage with about 4,075 gallons of liquid oxygen has begun at Cape Canaveral's Complex 41 following the thermal conditioning of the transfer pipes.

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 two firings to propel the TDRS K satellite into its intended orbit tonight.

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.

All console operators have reported GO status during the pre-fueling readiness poll. The ULA launch director Lou Mangieri also voiced his approval for moving forward with the countdown as scheduled today.

Loading of cryogenic liquid oxygen and liquid hydrogen into the Atlas 5 rocket will be getting underway a short time from now.

T-minus 120 minutes and counting! The launch countdown has resumed for today's flight of the Atlas 5 rocket on the NASA mission to deploy the Tracking and Data Relay Satellite.

Clocks have one more built-in hold planned at T-minus 4 minutes. That pause will last 25 minutes during which time the final "go" for launch will be given. All remains targeted for liftoff at 8:48 p.m. EST from Cape Canaveral's Complex 41.

In the next couple of minutes, chilldown thermal conditioning of the mobile launch platform upon which the rocket stands will begin. This is meant to ease the shock on equipment when supercold cryogenic propellants start flowing into the rocket.

The ULA launch conductor at the Atlas Spaceflight Operations Center is briefing his team on procedures before entering into the final two hours of the countdown.

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T-minus 2 hours and holding. The countdown has just entered the first of two planned holds over the course of the morning that will lead to the 8:48 p.m. EST launch of the Atlas 5 rocket.

This initial pause was designed to give the team some margin in the countdown timeline to deal with technical issues or any work that could fall behind schedule before fueling starts.

The final hold is scheduled to occur at T-minus 4 minutes.

The final hands-on work has wrapped up at the launch pad and technicians have departed the complex. Safety officials just confirmed that the surrounding danger area has been cleared of all workers for the remainder of the countdown.

The weather status board shows all launch criteria still green and GO. The forecast for the 8:48 to 9:28 p.m. EST window continues to reflect a 70 percent chance of favorable conditions.

The outlook for the launch window now predicts scattered clouds at 2,000 and 12,000 feet, a broken deck at 26,000 feet, isolated showers in the area, good visibility, southerly winds of 20 gusting to 24 knots, a temperature of 73 degrees F and humidity level of 80 percent.

The Tracking and Data Relay Satellite K, or TDRS K for short, will ride the two-stage Atlas-Centaur booster into a geosynchronous transfer orbit tonight, blasting off at 8:48 p.m. EST (0148 GMT).

This will be the first time NASA has launched one of its communications satellites since 2002, and this deployment begins the third-generation of TDRS spacecraft.

ted in 1973 and launching its first satellite in 1983, the system was conceived to provide constant communications with astronauts and science spacecraft circling the planet in low-Earth orbit. The TDRS design uses a constellation of geosynchronous satellites parked 22,300 miles above Earth to provide global coverage.

Looking down from that vantage point, the TDRS network receives signals from vehicles like the space station flying at a mere 250 miles and routes the telemetry, voice, video and science information to a dedicated ground terminal for delivery to Houston.

Read our preview story.

Now entering the final five hours to the United Launch Alliance Atlas 5 rocket flight with the TDRS K payload for NASA. This will be the civilan space agency's eighth use of Atlas 5 over the past eight years.

"NASA has a terrific record flying on Atlas 5. We've successfully launched seven missions on this rocket -- missions to Pluto, Jupiter, the moon, the sun, the radiation belts and two spacecraft to Mars," said Tim Dunn, the NASA launch director for TDRS K.

The first NASA mission sent the Mars Reconnaissance Orbiter to the red planet on Aug. 12, 2005. The New Horizons probe on a three-billion-mile voyage to fly by Pluto and explore the frigid edge of the solar system followed on Jan. 19, 2006. Then came the dual launch of the Lunar Reconnaissance Orbiter and the LCROSS impactor to the Moon's South Pole on June 18, 2009. The Solar Dynamics Observatory was placed into orbit on Feb. 11, 2010. The Juno spacecraft to study the planet Jupiter was launched on Aug. 5, 2011. The Mars Science Laboratory with the Curiosity rover left Earth on Nov. 26, 2011. And most recently the twin Radiation Belt Storm Probes were sent aloft on Aug. 30, 2012.

Now comes TDRS K at 8:48 p.m. EST.

In today's first weather briefing to mission managers, all current conditions are observed GO for launch of the Atlas 5 rocket and odds for the 8:48 p.m. EST liftoff time are 70 percent favorable.

The outlook for the launch window now predicts scattered clouds at 2,000 and 12,000 feet, a broken deck at 26,000 feet, isolated showers in the area, good visibility, south-southwesterly winds of 24 gusting to 28 knots, a temperature of 73 degrees F and humidity level of 80 percent.

The countdown begins now for this evening's launch of the Atlas 5 rocket to deploy NASA's latest Tracking and Data Relay Satellite. The spacecraft is headed to geosynchronous orbit to replenish the constellation needed for constant communications to the space station and other satellites in low-Earth-orbit.

NASA officials report that nothing is amiss and activities are progressing as planned for flight.

Clocks are picking up the seven-hour, 15-minute sequence of work that will prepare the booser, payload and ground systems for blastoff at 8:48 p.m. EST (0148 GMT).

Soon the launch team will begin powering up the rocket to commence standard pre-flight tests. Over the subsequent few hours, final preps for the Centaur's liquid oxygen and liquid hydrogen systems will be performed, along with a test of the rocket's guidance system and the first stage propulsion and hydraulic preps, internal battery checks and testing of the C-band system used to track the rocket as it flies downrange, plus a test of the S-band telemetry relay system. The Complex 41 site will be cleared of all personnel at 5:38 p.m.

A planned half-hour hold begins at 5:53 p.m. when the count reaches T-minus 120 minutes. Near the end of the hold, the team will be polled at 6:20 p.m. to verify all is in readiness to start fueling the rocket for launch.

Supercold liquid oxygen begins flowing into the Centaur upper stage around 6:40 p.m., followed by the first stage filling around 6:53 p.m. Liquid hydrogen fuel loading for Centaur will be completed a short time later.

A final hold is scheduled at the T-minus 4 minute mark starting at 8:19 p.m. That 25-minute pause will give everyone a chance to finish any late work and assess the status of the rocket, payload, Range and weather before proceeding into the last moments of the countdown.

The launch window extends from 8:48 to 9:28 p.m. EST (0148-0228 GMT).

With the approaching cold front now predicted to impact Central Florida after tonight's launch opportunity is over, meteorologists have improved the odds of acceptable weather to 70 percent for liftoff of the Atlas 5 rocket.

"The primary concerns for launch are cumulus clouds, disturbed weather associated with isolated rainshowers and ground winds," forecasters reported this morning.

The launch time outlook calls for three levels of scattered clouds at 3,000 12,000 feet and 28,000 feet, "very isolated" showers, good visibility, southwesterly winds of 24 gusting to 28 knots and a temperature around 74 degrees F.

If the launch slips to Thursday for some reason, there is a 60 percent chance of acceptable conditions for the backup opportunity.

"In the event of a 24-hour delay, the front looks to be well south of Central Florida with gradually improving weather, however gusty northerly winds will linger. The primary concerns for a 24-hour delay are ground winds and any remnant thick clouds behind the front," meteorologists said today.

Launch day is here for the Atlas 5 rocket and TDRS K communications satellite, and the skies are clear so far. That cold front is coming but the weather looks pretty good this morning.

Here is a corrected timeline of countdown for this afternoon and evening:

 HR:MM..Eastern...Event
T-6:20...1:33pm...Countdown begins with rocket power up
T-5:30...2:23pm...Weather briefing
T-4:55...2:58pm...Start clearing assembly building area
T-4:20...3:33pm...C-band tracking beacon testing
T-3:40...4:13pm...S-band telemetry link checks
T-2:55...4:58pm...Establish blast danger area roadblocks
T-2:20...5:33pm...Weather briefing
T-2:15...5:38pm...Clear the pad
T-2:00...5:53pm...T-120 minutes and holding (for 30min)
T-2:00...6:18pm...Launch conductor briefing to team
T-2:00...6:20pm...Readiness poll for fueling
T-2:00...6:23pm...Resume countdown
T-1:50...6:33pm...Centaur LOX transfer line chilldown
T-1:43...6:40pm...Begin Centaur liquid oxygen loading
T-1:30...6:53pm...Begin Atlas first stage LOX loading
T-1:25...6:58pm...Centaur LH2 transfer line chilldown
T-1:10...7:13pm...Centaur RL10 engine chilldown
T-1:02...7:21pm...Begin Centaur liquid hydrogen loading
T-0:40...7:43pm...FLight termination system final test
T-0:16...8:07pm...RD-180 engine fuel fill sequence
T-0:10...8:13pm...Weather briefing
T-0:04...8:19pm...T-4 minutes and holding (for 25min)
T-0:04...8:41pm...Readiness poll for launch
T-0:04...8:44pm...Resume countdown
T-0:00...8:48pm...LAUNCH

Rolling to the launch pad this morning, an Atlas 5 rocket now stands perched atop Cape Canaveral's Complex 41 to deploy a data-relay satellite to support the International Space Station, iconic Hubble Space Telescope and NASA's varied science satellites.

Read our full story.

And don't miss the spectacular rollout our photo gallery.

Here's our photo gallery showing the Atlas 5's trip to the pad on Tuesday morning.

The weather forecast remains 60 percent favorable for launch from Cape Canaveral at 8:48 p.m. EST on Wednesday.

Cumulus clouds, disturbed weather and gusty winds from an approaching cold front are the concerns.

The outlook calls for scattered clouds at 3,000 and 12,000 feet, a broken deck at 28,000 feet, isolated showers in the area, good visibility, south-southwesterly winds of 24 gusting to 28 knots and a temperature of 73 degrees F.

On the pad! Completing the first third-of-a-mile on the trek to orbit, the Atlas 5 rocket has arrived at the Complex 41 pad for Wednesday evening's ascent to deploy a NASA communications spacecraft.

The Tracking and Data Relay Satellite K (TDRS K) is bound for geosynchronous orbit to replenish the existing space network to transmit information between low-Earth-orbit craft and mission controllers. Users depending on the system include the space station, Hubble and NASA's fleet of scientific missions.

The Atlas 5 rocket will inject the Boeing-built satellite into a highly elliptical transfer orbit, and the spacecraft will spend about 10 days maneuvering itself into a circular orbit 22,300 miles above the Pacific for testing and checkout.

Its operational location is targeted to be 171 degrees West longitude.

The two mobile trailers connected to the launching platform, which were part of the convoy during this morning's rollout, soon will be hooked up to power and communications systems at the pad. These trailers provide conditioned air to the payload and communications with the rocket during the rollout and the countdown. They are protected from the blast of launch by a concrete structure on the north-side of the platform.

Within the next hour, the auto couplers between the pad and platform will be engaged to route umbilical connections from the ground to the rocket for tomorrow's fueling of the booster with cryogenic propellants.

Later today, the undercarriages used to move the mobile platform will be disconnected and the "trackmobiles" pulled free.

And the first stage will be loaded with its supply of highly refined kerosene fuel, called RP-1.

Ground crews will secure the rocket for a quiet evening leading into the launch opportunity tomorrow. Countdown clocks will start ticking about seven hours before liftoff time.

Wednesday's 40-minute launch window opens at 8:48 p.m. and closes at 9:28 p.m. EST.

Here's a timeline of the countdown's key events:

 HR:MM..Eastern...Event
T-6:20...1:48pm...Countdown begins with rocket power up
T-5:30...2:38pm...Weather briefing
T-4:55...3:13pm...Start clearing assembly building area
T-4:20...3:48pm...C-band tracking beacon testing
T-3:40...4:28pm...S-band telemetry link checks
T-2:55...5:13pm...Establish blast danger area roadblocks
T-2:20...5:48pm...Weather briefing
T-2:15...5:53pm...Clear the pad
T-2:00...6:08pm...T-120 minutes and holding (for 30min)
T-2:00...6:15pm...LIVE NASA Television coverage begins
T-2:00...6:33pm...Launch conductor briefing to team
T-2:00...6:35pm...Readiness poll for fueling
T-2:00...6:38pm...Resume countdown
T-1:50...6:48pm...Centaur LOX transfer line chilldown
T-1:43...6:55pm...Begin Centaur liquid oxygen loading
T-1:30...7:08pm...Begin Atlas first stage LOX loading
T-1:25...7:13pm...Centaur LH2 transfer line chilldown
T-1:10...7:28pm...Centaur RL10 engine chilldown
T-1:02...7:36pm...Begin Centaur liquid hydrogen loading
T-0:40...7:58pm...FLight termination system final test
T-0:16...8:22pm...RD-180 engine fuel fill sequence
T-0:10...8:28pm...Weather briefing
T-0:04...8:34pm...T-4 minutes and holding (for 10min)
T-0:04...8:41pm...Readiness poll for launch
T-0:04...8:44pm...Resume countdown
T-0:00...8:48pm...LAUNCH

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The United Launch Alliance Atlas 5 rocket has emerged from its vehicle assembly building for the journey to the pad, a milestone move for the program about to make its 35th trip to space.

Riding atop a mobile launching platform, the 191-foot-tall satellite booster is moving to Cape Canaveral's Complex 41 for launch of NASA's Tracking and Data Relay Satellite.

"ULA is proud to serve a critical role in delivering NASA payloads to orbit," said Vern Thorp, ULA's program manager for NASA missions.

This will be the 8th NASA launch using the Atlas 5 rocket.

The rocket's rollout to the pad has begun!

This slow half-hour drive from the 30-story Vertical Integration Facility to Cape Canaveral's Complex 41 pad uses a pair of specially-made "trackmobiles" to carry the rocket's 1.4-million pound mobile launching platform along rail tracks for the 1,800-foot trip.

The two-stage rocket and the TDRS K spacecraft were put together inside the assembly building in preparation for this rollout event. The Atlas 5 is designed to spend minimal time at the launch pad, which does not include a service gantry like other sites.

The Atlas 5 rocket will be hauled out to the launch pad this morning, riding the rails from its assembly building to Complex 41 for the final day-and-a-half of preparations to fly the NASA TDRS K communications satellite into orbit tomorrow night.

First motion for the rollout is targeted for 10 a.m. EST (1500 GMT). Watch this page for updates and photos!

The Launch Readiness Review has adjourned with the consensus to press ahead with Tuesday morning's rollout of the Atlas 5 rocket and Wednesday night's flight to deploy NASA's Tracking and Data Relay Satellite K.

Weather forecasters continue to predict a 60 percent chance of acceptable conditions for Wednesday night's launch opportunity opening at 8:48 p.m. EST (0148 GMT).

The launch time outlook now calls for scattered low clouds at 3,000 feet, a broken deck at 26,000 feet, isolated showers, good visibility, southerly winds of 24 gusting to 28 knots and a temperature around 71 degrees F.

If the launch slips to Thursday evening for some reason, the latest odds are 40 percent favorable due to gusty ground winds and thick clouds.

The week begins this morning with the Launch Readiness Review of senior mission managers that culminates with approval for rollout of the Atlas 5 rocket tomorrow to Cape Canaveral's Complex 41 pad.

Also upcoming this afternoon is the pre-launch news conference at 1 p.m. EST (1800 GMT). We will have live streaming video of the briefing from launch, spacecraft and weather officials previewing Wednesday night's scheduled liftoff of the Tracking and Data Relay Satellite K.

Assembled for flight quicker than ever before, a United Launch Alliance Atlas 5 rocket is ready for blastoff this week to deploy NASA's newest geosynchronous communications satellite to relay data from low-Earth-orbit spacecraft.

Read our full story.

Concerns about the cold front expected to push through the spaceport area on Wednesday have dropped the forecast to a 60 percent chance of acceptable conditions for launch, meteorologists reported this morning.

"The front is a little faster than indicated yesterday with pre-frontal showers and possible thunderstorms in the Central Florida vicinity late Wednesday afternoon and through the evening and overnight hours. The front is expected to be south of Central Florida by late Thursday morning. The pressure gradient in advance of the front (Wednesday) tightens with strengthening winds on Wednesday and Thursday," forecasters say.

"On launch day, moisture increases through the day as the aforementioned cold front advances into North Central Florida by the launch window. There is a low threat of an isolated thunderstorm by early afternoon with an increasing threat late afternoon/early evening. Winds expected to strengthen from the south-southwest with gusts in the mid to upper 20s through the count and during the window. The primary concerns for launch are cumulus clouds, disturbed weather associated with isolated rainshowers, thick cloud and strengthening ground winds."

The launch time outlook calls for scattered low clouds at 3,000 feet, more scattered clouds at 8,000 feet, a broken deck at 24,000 feet, isolated showers, good visibility, southwesterly winds of 24 gusting to 28 knots and a temperature around 71 degrees F.

If the launch slips to Thursday evening for some reason, the odds are 60 percent favorable for good weather as well. The concerns will be ground winds and thick clouds.

"In the event of a 24-hour delay, current timing indicates the front south of Central Florida by late morning with gradually improving weather. However, the pressure gradient behind the front remains tight with gusty north-northwest winds," meteorologists project.

Air Force meteorologists are giving favorable odds of acceptable weather to launch the Atlas 5 rocket and a NASA communications satellite Wednesday night from Cape Canaveral, but forecasters will be watching the progress of a cold front sliding through the area around the same time.

"Fair weather through the weekend with a weak cold front pushing through Central Florida on Sunday with a small coastal shower threat as winds become on-shore. On Monday and Tuesday, high pressure dominates Central Florida with fair weather and a small coastal shower threat with the persistent on- shore winds. The next significant cold front pushes into the Florida Big Bend area Wednesday evening," meteorologists reported this morning.

This early forecast gives a 70 percent chance of acceptable conditions during the 40-minute launch window opening at 8:48 p.m. EST, but the actual timing and proximity of the front to Central Florida will have a significant effect on the weather during the count, forecasters cautioned.

"At present, the timing of the cold front in Central Florida is expected late Wednesday evening and through the overnight/morning hours pushing south of Central Florida by late Thursday morning/early afternoon. The pressure gradient in advance of the front (Wednesday) tightens with strengthening winds on Wednesday and Thursday," the weather team says.

"On launch day, moisture gradually increases through the day as the aforementioned cold front advances into the Big Bend area by the launch window. There is a low threat of an isolated thunderstorm by mid-afternoon with a slight increase early evening. Winds expected to strengthen from the south with gusts in the mid to upper 20s through the count and during the window. The primary concerns for launch are cumulus clouds, disturbed weather associated with isolated rainshowers and strengthening ground winds," the forecast says.

The launch time outlook calls for scattered low clouds at 3,000 feet, a broken deck at 26,000 feet, isolated showers, good visibility, easterly winds of 24 gusting to 28 knots and a temperature around 73 degrees F.

If the launch slips to Thursday evening for some reason, the odds are 60 percent favorable for good weather. The concerns will be ground winds and thick clouds.

"In the event of a 24-hour delay, current timing indicates the front south of Central Florida by late morning/early afternoon with gradually improving weather. However, the pressure gradient behind the front remains tight with gusty northwest winds," forecasters said.

A replacement ordnance controller unit, shipped in yesterday from the United Launch Alliance factory in Decatur, Alabama, has been installed on the Atlas 5 rocket at the Vertical Integration Facility.

During the integrated systems test of the rocket and mated payload on Tuesday, the original unit experienced a fault likely the result of an internal short.

The replacement work and repeating the testing necessitated the launch be pushed back by a day.

Meanwhile, the Flight Readiness Review for the Atlas and TDRS K was held this morning and gave concurrence to continue with next Wednesday's launch date. Mangers will meet again on Monday morning for the Launch Readiness Review that gives approval for rollout of the rocket to the pad.

Next week's Atlas 5 rocket launch has been bumped back a day to give technicians time to replace an ordnance device on the booster, moving liftoff to Wednesday at 8:48 p.m. EST.

NASA's Tracking and Data Relay Satellite K will be deployed in the mission from the Cape Canaveral Air Force Station in Florida. The evening's available launch window extends 40 minutes.

"The one-day postponement allows technicians additional time to replace an Ordnance Remote Control Assembly (ORCA) that gave an anomalous signal indication prior to planned ordnance connections," NASA said in a statement today.

The ORCA is a pyrotechnic initiation subsystem that provides multiple electronic outputs throughout the launch vehicle, according to its manufacturer.

Under the revised plan, the Launch Readiness Review will be held on Monday, followed by the pre-launch news conference.

Rollout of the Atlas 5 from its assembly building to the launch pad occurs on Tuesday at 10 a.m.

Cape Canaveral's 2013 launch season began taking shape today as technicians NASA's next-generation communications satellite was mounted atop the Atlas 5 rocket Sunday, kicking off the final week of preparations to send the science-relay spacecraft into orbit.

Read our full story.

The unfavorable forecast of high winds at Complex 41 has prompted a one-day delay in transporting the TDRS K spacecraft to the Atlas 5 rocket's vehicle assembly building.

Originally planned for Saturday morning, the trip from the Astrotech processing facility in Titusville to the launch site at Cape Canaveral Air Force Station has been bumped back to Sunday. Meteorologists predict better conditions for the hoisting operations then.

NASA says the schedule change won't impact the planned Jan. 29 launch date.

We have posted a photo gallery of yesterday's encapsulation of TDRS K.

Moving ever closer to its launch in less than two weeks, NASA's TDRS K communications spacecraft was encapsulated in the two-piece nose cone of the Atlas 5 rocket today.

The halves of the aluminum fairing were pushed together to shroud the satellite at the Astrotech processing facility in Titusville. It is the "extended payload fairing" version in the tailored Atlas options, standing 14 feet in diameter and 42 feet fall.

The fairing protects the delicate spacecraft during ascent through the atmosphere, then gets jettisoned four-and-a-half minutes into flight after the first stage drops away and the Centaur upper stage lights.

The cocooned cargo will be set aboard a transport trailer and readied for the drive to Cape Canaveral's Complex 41 on Saturday morning. Once at the Vertical Integration Facility, payload will be hoisted atop the Centaur and mated to the rocket for launch.

Liftoff remains scheduled for Jan. 29 at 8:52 p.m. EST.

The first spacecraft in NASA's third generation of Tracking and Data Relay Satellites has been tested and fueled in preparation for its trek to orbit Jan. 29. Reporters and photographers got to see the craft Friday in the cleanroom facilities at the Astrotech complex in Titusville, Florida.

See our photo gallery.

Meanwhile, the pre-flight schedule has been updated, with encapsulation now planned for next Wednesday and Thursday and mating the spacecraft to the Atlas 5 rocket now planned for next Saturday, Jan. 19.

United Launch Alliance over the weekend completed building up the Atlas 5 rocket that will carry NASA's Tracking and Data Relay Satellite K into orbit later this month.

The first stage was erected on the mobile launch platform Thursday at the Vertical Integration Facility. Unfavorable weather, however, delayed the interstage adapter installation and the subsequent Centaur upper stage hoisting.

The work successfully wrapped up during the weekend, completing the initial stacking operations for the 35th Atlas 5 rocket.

Testing will be underway for the next couple of weeks until the TDRS K payload arrives for its attachment to the rocket on Jan. 17.

For its part, the TDRS K's battery has been charged and the loading of propellant into the satellite began Sunday. Encapsulation of the spacecraft within the rocket's nose cone at the Astrotech processing facility is scheduled for Jan. 15.

Liftoff remains scheduled for Jan. 29 at 8:52 p.m. EST.

Cape Canaveral's 2013 launch season began taking shape today as technicians started assembling the Atlas 5 rocket for the year's first Space Coast mission -- delivery of a NASA communications satellite into orbit on Jan. 29.

Read our full story.

The next addition to NASA's constellation of Tracking and Data Relay Satellites has arrived at the Kennedy Space Center, landing this morning aboard a military transport aircraft after a cross-country ride inside a shipping container from Boeing's factory in Los Angeles.

Dubbed TDRS K, this latest spacecraft for the agency's global communications infrastructure is scheduled for launch atop an Atlas 5 rocket from Cape Canaveral's Complex 41 on Jan. 29.

Read our full story.