TacSat 4's orbit-raising burn is complete and successful, wrapping up the final major event in today's launch and early operations phase of the mission.

In a few minutes, thrusters aboard the TacSat 4 satellite will ignite for several minutes to raise the low point of its orbit by about 300 miles. The burn will ensure the spacecraft doesn't burn up in the atmosphere soon.

The firing occurs as TacSat 4 reaches its first apogee more than 7,000 miles above Earth.

Mike Hurley, head of spacecraft development at the Naval Research Laboratory, reports the satellite has deployed its solar panels, is pointing toward the sun and has assumed attitude control with reaction wheels.

Check out photos of this morning's colorful sunrise launch.

The REEF tracking station in the Indian Ocean has acquired the first signal from TacSat 4, confirming it's alive following launch.

The first chance for ground controllers to gain insight into the health of the TacSat 4 payload will be about 59 minutes after launch when it passes over a ground site on the island of Diego Garcia in the Indian Ocean.

TacSat 4 will fire its thrusters for a checkout burn about an hour and 45 minutes into the mission, then again later today to raise the low point of its orbit from about 100 miles to more than 400 miles in altitude.

SPACECRAFT SEPARATION CONFIRMED. The rocket's telemetry being radioed through a ground station in Chile confirms the payload separated. The vehicle's orbital parameters are as expected.

T+plus 35 minutes. The launch team is awaiting confirmation of a successful flight.

T+plus 28 minutes. The TacSat 4 payload should have deployed by now. Officials hope to confirm this news as the rocket passes over Santiago in a few minutes.

T+plus 25 minutes. The Minotaur's Star 48 upper stage should now have fired and the TacSat 4 satellite should now be in orbit, but there is no way to verify that at this time.

The next pass over a ground station is expected at about 8:25 a.m. Alaska time (1625 GMT; 12:25 p.m. EDT) when the rocket passes over Santiago, Chile.

T+plus 23 minutes. The rocket just passed out of range of the Vandenberg tracking station as expected. The fourth stage should now be firing, but without a communications link, there is no way to confirm the mission's progress.

T+plus 22 minutes. One minute until staging.

T+plus 20 minutes. The rocket is now flying 3,585 miles south of Kodiak and traveling 12,750 mph.

T+plus 17 minutes. Third stage separation and fourth stage ignition are expected at about the 23-minute point of the flight, or about six minutes from now.

T+plus 15 minutes. No problems reported so far in this fifth launch of a Minotaur 4 rocket.

T+plus 12 minutes. The rocket has flown over the horizon here at Kodiak Launch Complex, but there is still a strong radio signal from the vehicle through a tracking station in California.

T+plus 9 minutes. The launch vehicle is now in the correct orientation for fourth stage ignition.

T+plus 8 minutes. All systems look good so far in this launch as the rocket continues this ballistic coast phase before jettisoning its spent third stage motor and firing the Star 48 fourth stage. Ignition expected in less than 15 minutes.

T+plus 7 minutes. Velocity now more than 13,000 mph as the rocket soars over the Pacific Ocean.

T+plus 6 minutes. The downrange tracking station at Vandenberg Air Force Base in California has acquired the signal from the Minotaur rocket.

T+plus 4 minutes, 45 seconds. Downrange distance is now 574 miles and altitude is 231 miles.

T+plus 3 minutes, 20 seconds. The third stage has expended its solid propellant and the rocket is now coasting through the upper reaches of the atmosphere to reach an altitude of 400 miles. This ballistic coast phase will last almost 20 minutes.

T+plus 2 minutes, 30 seconds. The rocket has shed the payload fairing now that the vehicle is out of the dense lower atmosphere.

T+plus 2 minutes, 10 seconds. Telemetry engineers report a good separation of the second and third stages. The SR120 motor will fire for 72 seconds. Coming up on jettison of the Minotaur 4's nose cone.

T+plus 1 minute. The first stage motor has burned out and separated from the second stage.

T+plus 30 seconds. The Minotaur 4 rocket is passing Max-Q, the phase of maximum aerodynamic pressure.

LIFTOFF. Liftoff of the Minotaur 4 rocket on a mission to give warfighters a safer and more efficient communications link.

T-minus 1 minute and counting.

T-minus 2 minutes and counting. The countdown automatic sequence has started and final limit checks are go.

The safe-and-arm devices are being rotated to the arm position.

T-minus 4 minutes and counting. The rocket's guidance system has been switched to navigation mode and the flight computer is armed for flight.

T-minus 5 minutes and counting. The rocket is being switched to internal power.

T-minus 6 minutes, 30 seconds. The launch decision authority has given final permission for launch.

T-minus 8 minutes and counting. The destruct system has been armed for liftoff.

T-minus 9 minutes, 30 seconds. The launch vehicle's flight termination system has been switched to internal power and the external power source has been turned off.

T-minus 12 minutes and counting. The exact launch time is being programmed into the Minotaur 4 flight computer.

T-minus 14 minutes and counting. The launch hazard area and impact limit lines are clear of personnel.

T-minus 15 minutes and counting. All stations report they are go for launch at 7:49 a.m. local time (1549 GMT; 11:49 a.m. EDT).

T-minus 17 minutes and counting. Coming up on the final readiness check of the launch team.

T-minus 22 minutes and counting. Today's flight is the second Minotaur 4 rocket mission from Kodiak Launch Complex. The state-owned facility has hosted two previous orbital launches.

The Minotaur 4 is based on retired Peacekeeper missile motors. A smaller Minotaur 1 rocket uses Minuteman stages.

Although engineers finished constructing TacSat 4 in December 2009, it had to wait until now for a ride into space. The Minotaur launch manifest was shuffled several times as the military prioritized other payloads and resolved issues with the launch vehicle.

"The spacecraft has been done for some time," said Peter Wegner, director of the Operationally Responsive Space office. "Really the issue has been two things, getting the rocket complete and ready to launch. And then getting the priority, not just on the range, but priority in the whole national space launch architecture to get in line to do it. I think it's slipped seven times."

T-minus 26 minutes and counting. The rocket's safety system is being turned on and tested.

T-minus 28 minutes and counting. The Minotaur 4's telemetry transmitters are being powered on.

T-minus 36 minutes and counting. There are no planned built-in holds during today's countdown.

It will take 27 minutes, 48 seconds to release the TacSat 4 satellite in the planned highly elliptical orbit ranging in altitude from 115 miles to 7,487 miles.

T-minus 41 minutes and counting. There is now a zero percent chance of weather prohibiting launch this morning, according to forecasters.

T-minus 45 minutes and counting. Engineers report the booster's navigation system is properly aligned for flight.

T-minus 48 minutes and counting. The Minotaur's inertial navigation system is being aligned for launch.

T-minus 50 minutes and counting. All systems are reported go for launch right now. There are no issues with the rocket, payloads or the Kodiak range.

T-minus 57 minutes. The launch team is powering up the Minotaur 4 rocket's S-band communications system for launch.

T-minus 1 hour and counting. The countdown is entering the final phase and engineers are conducting final checks to ready the Minotaur rocket for liftoff at 1549 GMT (11:49 a.m. EDT; 7:49 a.m. Alaska time).

Standing by to enter the final launch checklist at T-minus 60 minutes.

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Today's launch is dedicated to the 30 Americans who perished in the downing of a Chinook helicopter in Afghanistan's Wardak province on Aug. 6. The TacSat 4 team added a special emblem to the Minotaur rocket's nose cone in remembrance of the loss in the Aug. 6 tragedy.

The names of lost family members of the Minotaur rocket's industry and military teams are also emblazoned on the payload fairing.

Today's launch is dedicated to the 30 Americans who perished in the downing of a Chinook helicopter in Afghanistan's Wardak province on Aug. 6. The TacSat 4 team added a special emblem to the Minotaur rocket's nose cone in remembrance of the loss in the Aug. 6 tragedy.

The names of lost family members of the Minotaur rocket's industry and military teams are also emblazoned on the payload fairing.

T-minus 90 minutes. Check out photos of the Minotaur 4 rocket on the launch pad earlier this morning.

T-minus 2 hours. This is a relatively quiet phase of the countdown until the final prelaunch checklist begins at T-minus 60 minutes.

The payload for today's mission is the 992-pound TacSat 4 satellite, a spacecraft to better serve deployed U.S. military forces in war theaters like Afghanistan and Iraq.

TacSat 4 is heading for an oddball oval-shaped orbit stretching from a low point of 115 miles to a high point of 7,487 miles. A few hours after launch, TacSat 4 will raise the low point of its orbit to approximately 435 miles.

From that orbit, the satellite's 10 UHF communications channels will provide nine times the signal strength compared to legacy satellites in geosynchronous orbit 22,000 miles over the equator. TacSat 4's orbit is tailored for coverage in war zones in the Middle East and Southwest Asia.

Instead of using bulky directional antennas to communicate with other units or headquarters, troops will use handheld radios to talk through TacSat 4, at least when the satellite is overhead.

"You're using basically a glorified walkie-talkie to talk anywhere inside of the satellite's field of view, and that's just a huge game-changer," said Peter Wegner, director of the military's Operationally Responsive Space office.

The U.S. Navy has plans drawn up for three or four more satellites TacSat 4 to provide complete regional coverage of battlefields, but those ideas depend on funding and programmatic decisions.

We have posted a time lapse video of the launch service structure retracting away from the Minotaur rocket this morning.

Follow along with today's launch by checking out this timeline of key events during the Minotaur's ascent into space.

And view a ground track map of the Minotaur's flight path on the way to orbit this morning.

T-minus 2 hours, 30 minutes. The latest weather briefing indicates all criteria are now green and expected to remain that way for the rest of the countdown.

Meteorologists now expect partly cloudy skies with a widely scattered deck of clouds at 5,000 feet, winds from the west between 5 mph and 15 mph, and a 10 percent chance an elevated proton flux from solar activity could violate launch rules.

Otherwise, forecasters don't believe there will be any weather that could threaten launch today.

T-minus 3 hours and counting. The weather forecast has improved to a 30 percent chance of unfavorable conditions at launch time, mainly due to solar radiation that could interfere with the Minotaur's flight computer and guidance system.

The final arming of the Minotaur vehicle is complete and the final workers are evacuating the launch pad.

Situated on the southern shore of Kodiak Island, the Minotaur launch pad is just a few hundred feet from the Pacific Ocean.

Owned by Alaska Aerospace Corp., the Kodiak Launch Complex is situated on Narrow Cape. Locals refer to the site as "the other Cape" in reference fo the more famous launch range in Cape Canaveral, Fla.

AAC modified the launch pad to support Minotaur 4 rockets. Originally built to specifications for the Athena launch vehicle, the pad configuration was changed by cutting a larger door to support the installation of the longer Minotaur first stage.

This morning's mission will be the third space launch from Kodiak, coming after an Athena flight in 2001 and a Minotaur launch in 2010.

Under a starry sky with temperatures hovering in the lower 40s Fahrenheit, the Minotaur 4 rocket stands brightly illuminated for liftoff in less than three-and-a-half hours.

With the launch pad now clear of non-essential personnel, the pad crew is now proceeding with final vehicle closeouts and arming.

T-minus 3 hours, 30 minutes. After completing the pre-flight vehicle test checklist, Minotaur and ground support equipment have been powered down.

Minotaur's system testing is continuing. A pre-flight alignment of the rocket's inertial navigation system just occurred. Checks of the vehicle's safety system were completed a little earlier. A steering sequence test for the Star 48 upper stage motor is next.

T-minus 4 hours and counting. The team just conducted a series of signal strength checks for the rocket's S-band system used for receiving telemetry from Minotaur during its flight downrange.

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Launch pad technicians confirm that service structure rollback was completed at 3:30 a.m. local time.

And now the pad enclosure is rotating away from Minotaur to uncover the rocket for today's launch.

This building on rails provided workers access to the various parts of the rocket and gave the vehicle shelter from the weather during the pre-launch mission campaign.

No problems are being reported in this morning's countdown and launch remains on schedule for 1549 GMT.

The pad's front door has swung open.

The "go" has been given for retracting the launch pad service structures to reveal the Minotaur rocket.

On a crisp, clear morning in Alaska, the launch team has arrived at the control center two miles northwest of Launch Pad No. 1 at Kodiak Launch Complex. Voice and status checks are now underway.

Nearly 50 senior managers and engineers from the Air Force, the Navy, Orbital Sciences and Alaska Aerospace occupy the control room during countdown operations.

The countdown formally begins at 2:49 a.m. local time (1049 GMT; 6:49 a.m. EDT).

The launch pad crew is also completing final inspections of the Minotaur 4 rocket before the clamshell-like service structure retracts. The rotating launch service structure should move beginning around 3:19 a.m. local time (1119 GMT; 7:19 a.m. EDT).

The four-stage rocket is made of three rocket motors from the Peacekeeper missile program. A Star 48 fourth stage will place the mission's TacSat 4 payload into a 7,487-mile by 115-mile orbit inclined 63.4 degrees to the equator.

The first stage is a Peacekeeper SR118 motor manufactured by ATK. The second stage SR119 motor was originally built by Aerojet, and ATK was the contractor for the Peacekeeper's SR120 third stage.

ATK is also the builder of the Star 48 fourth stage, which is being used in place of the standard Orion 38 fourth stage motor to give TacSat 4 an extra boost into a higher orbit. This particular configuration is known as the Minotaur 4+ rocket.

The weather forecast continues to indicate a 40 percent chance of bad weather prohibiting launch Tuesday. The outlook calls for the same chance of violation Wednesday.

The primary concern is the proton flux from a solar flare unleashed a few days ago. Although the flare originated from a sunspot not directly aimed at Earth, radiation will deliver a glancing blow to the planet.

Officials are concerned charged particles will play havoc with the Minotaur's guidance system and computers during launch, so if proton levels rise above a certain threshold, launch will not go forward.

Plans call for the five-hour countdown to get underway at 2:49 a.m. local time (1049 GMT; 6:49 a.m. EDT) Tuesday.

Workers are making final ordnance connections to pyrotechnic devices aboard the Minotaur 4 rocket today, one of the final steps before launch on Tuesday morning.

The launch forecast has slightly improved to a 40 percent chance of unacceptable conditions for liftoff. The most significant threat continues to be the chance of clouds, rain and solar radiation interfering with the rocket's flight computer.

The launch readiness review at Kodiak Launch Complex this morning concluded with a "go" to continue preparations for liftoff Tuesday morning at 7:49 a.m. Alaska time (1549 GMT; 11:49 a.m. EDT).

The Air Force and Kodiak Launch Complex are ready to support the launch of the Navy's TacSat 4 communications satellite, according to military officials.

The weather forecast for Tuesday has worsened to a 50 percent chance of acceptable conditions for liftoff. The primary threat is from charged particles streaming toward Earth from solar flares this week, generating a proton flux that could disrupt the performance of computers and electronics in the Minotaur 4 rocket.

There is also a chance rain, clouds and lightning could prohibit launch Tuesday, according to meteorologists.

After accomplishing a mission dress rehearsal yesterday, attention today turns to a launch readiness review to give formal approval for final launch preparations and the countdown, which is due to begin in the predawn hours Tuesday.

At the launch pad this morning, workers plan to complete end-to-end testing of the Minotaur's flight termination system, a destruct package that would be commanded to blow up the launcher if problems developed in flight.

The testing includes communications checks between the rocket and a ground station near the launch site.

This afternoon, technicians will load cold gas into the rocket's upper stage attitude control system. The system is responsible for manipulating the launcher's orientation in the latter phase of the 28-minute mission.

The attitude control system tanks will also be pressurized for launch today.

SIMULATED ABORT. Now officials are backing out of countdown procedures and safing the 78-foot-tall Minotaur rocket.

Five minutes away from the mock launch time of 1:50 p.m. local time (2150 GMT; 5:50 p.m. EDT). The launch team plans to issue a simulated abort in the final seconds and then safe the Minotaur 4 rocket.

Meanwhile, the simulation will continue as teams go through the events of the Minotaur's 28-minute flight to orbit with the TacSat 4 spacecraft.

The clamshell-like launch service structure has been retracted away from the Minotaur rocket as the countdown continues for today's dress rehearsal. The countdown clocks are ticking down toward a simulated launch time of 1:49 p.m. local time (2149 GMT; 5:49 p.m. EDT).

The launch team has gathered on the Alaska coastline today for a mission dress rehearsal, a practice countdown in which technicians will go through procedures to prepare the Minotaur 4 rocket and TacSat 4 payload for liftoff.

This dress rehearsal is an opportunity to work out issues and sharpen skills before the real launch day. Liftoff is set for 1549 GMT (11:49 a.m. EDT; 7:49 a.m. Alaska time) on Tuesday.

The weather forecast is generally favorable for launch Tuesday. There is a 30 percent chance the Minotaur rocket's launch weather rules will be violated, with the primary concerns being rain showers, low cloud ceilings and the chance of lightning in the area.

The dress rehearsal countdown begins at 1649 GMT (12:49 p.m. EDT; 8:49 a.m. Alaska time) this morning. Workers will retract the launch service structure about a half-hour later, revealing the 78-foot-tall Minotaur 4 rocket.

Technicians attached a 1,000-pound U.S. Navy communications satellite to its launch vehicle this week as preparations continue for liftoff Sept. 27 from the southern coast of Alaska.

The TacSat 4 satellite was moved from its processing facility to Kodiak Launch Complex's primary launch pad Thursday, then workers lifted the fully-fueled spacecraft in place on top of the fourth stage of the Minotaur 4 rocket.

The spacecraft was enclosed inside the rocket's 92-inch payload fairing earlier this month, then the entire nose apparatus was transported to the pad in one piece.

It was the last stop for the U.S. military payload before launching into orbit at approximately 1545 GMT (11:45 a.m. EDT; 7:45 a.m. Alaska time) on Sept. 27.

With the 78-foot-tall launcher now fully assembled, the attention of the launch team will now turn to testing and a series of readiness reviews leading toward the Sept. 27 blastoff from Kodiak Island, Alaska.

TacSat 4 is the third in a series of experimental tactical satellites developed under the military's Operationally Responsive Space initiative, which aims to field more focused, less expensive spacecraft to answer the needs of commanders in combat zones.

Developed by the Naval Research Laboratory, the craft features a 12-foot-wide antenna and 10 UHF communications channels to help reach mobile military units deployed in combat theaters.

The Minotaur 4 rocket will propel the satellite into an orbit stretching from an altitude of 435 miles to almost 7,500 miles above Earth.

The spacecraft will rapidly sweep near Earth on the low side of its orbit, then slowly rise high in the sky as it reaches its peak altitude, dwelling above battle zones for hours.

Its orbit will place TacSat 4's communications payload in range of polar regions for much of its orbit. Existing communications satellites stationed over the equator have trouble reaching those locations.

The launch of TacSat 4 will be the third orbital space mission to originate from the remote Alaska spaceport. Owned and operated by the state of Alaska, Kodiak Launch Complex hosted satellite launchings in 2001 and 2010 with Athena and Minotaur rockets.

Preparations to launch a U.S. Navy communications satellite have kicked off in Alaska three weeks before a souped-up Minotaur rocket will pilot the spacecraft to an orbit 7,500 miles above Earth.

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