BY SPACEFLIGHT NOW

Follow the countdown and flight of the Sea Launch Zenit 3SL rocket with the Koreasat 5 communications spacecraft. Reload this page for the latest on the mission.

TUESDAY, AUGUST 22, 2006

South Korea's first dual-use commercial and military communications satellite is now in space after a successful blastoff from a floating platform in the central Pacific Ocean. Read our full story.

0449 GMT (12:49 a.m. EDT)

Rob Peckham, the president Sea Launch, is offering his congratulations to the crowd of about 300 gathered at the company's Home Port in Long Beach. He says the orbit achieved in tonight's successful launch is right on target.

0439 GMT (12:39 a.m. EDT)

Ground crews have received the first signals from Koreasat 5, a few minutes earlier than anticipated. The Alcatel Alenia Space-built craft is alive in orbit.

0432 GMT (12:32 a.m. EDT)

Controllers expect to acquire the first signals from the newly-launched satellite in about 10 minutes via a ground tracking station in Fucino, Italy.

0431 GMT (12:31 a.m. EDT)

T+plus 64 minutes, 53 seconds. SPACECRAFT SEPARATION! The Koreasat 5 communications spacecraft has been released from the Block DM-SL upper stage to complete this 22nd Sea Launch flight.

0427 GMT (12:27 a.m. EDT)

T+plus 60 minutes. Deployment of the spacecraft from the upper stage is five minutes away. During this coast period between completion of the Block DM-SL stage's burn and spacecraft separation, the stage is providing the necessary control and orientation for payload release.

0421 GMT (12:21 a.m. EDT)

T+plus 54 minutes, 40 seconds. The Block DM-SL's 11D58M main engine has shut down, completing the powered phase of todays's launch. The stage will now coast for about 10 minutes before deploying the Koreasat 5 satellite.

0420 GMT (12:20 a.m. EDT)

T+plus 53 minutes, 55 seconds. The upper stage burn is confirmed to be in progress. This firing will send Koreasat 5 into geosynchronous transfer orbit.

0419 GMT (12:19 a.m. EDT)

T+plus 52 minutes. Standing by for confirmation of upper stage ignition.

0403 GMT (12:03 a.m. EDT)

T+plus 36 minutes. About 15 minutes remain in the coast. The vehicle is heading across the Atlantic at an altitude of more than 2,000 miles.

0352 GMT (11:52 p.m. EDT Mon.)

T+plus 25 minutes. The orbital coast phase is taking the rocket over South America now.

0345 GMT (11:45 p.m. EDT Mon.)

T+plus 18 minutes. The upper stage will coast in this orbit until the Block DM-SL reignites at T+plus 51 minutes for the firing to achieve geosynchronous transfer orbit. The burn should last about three minutes. Deployment of Koreasat 5 to complete today's launch is expected about 65 minutes after liftoff.

0344 GMT (11:44 p.m. EDT Mon.)

T+plus 17 minutes, 6 seconds. Engine cutoff. The Block DM-SL upper stage has completed its first burn, injecting the motor and attached Koreasat 5 spacecraft into a temporary parking orbit around Earth.

0343 GMT (11:43 p.m. EDT Mon.)

T+plus 16 minutes. The vehicle has reached orbital velocity. And the main engine pressures still reported normal.

0341 GMT (11:41 p.m. EDT Mon.)

T+plus 14 minutes. Three minutes remain in this planned upper stage burn to reach a parking orbit of 112 x 6,357 miles.

0339 GMT (11:39 p.m. EDT Mon.)

T+plus 12 minutes. The Block DM-SL is flying over 100 miles above the Pacific, firing its main engine with a mixture of highly refined kerosene propellant and supercold liquid oxygen.

0337 GMT (11:37 p.m. EDT Mon.)

T+plus 10 minutes. This burn of the upper stage will last eight-and-a-half minutes.

0335 GMT (11:35 p.m. EDT Mon.)

T+plus 8 minutes, 40 seconds. The Block DM-SL upper stage has ignited for today's first of two firings to propel the spacecraft from the current suborbital trajectory to geosynchronous transfer orbit.

0335 GMT (11:35 p.m. EDT Mon.)

T+plus 8 minutes, 30 seconds. The second stage vernier engines have shut down and jettisoning of the spent stage has occurred. It will impact the Pacific approximately 3,000 miles downrange from the launch platform.

0334 GMT (11:34 p.m. EDT Mon.)

T+plus 7 minutes, 10 seconds. The second stage RD-120 main engine has shut down. The vernier steering engines are still burning as designed.

0334 GMT (11:34 p.m. EDT Mon.)

T+plus 7 minutes. The second stage is throttling down in preparation for engine cutoff.

0333 GMT (11:33 p.m. EDT Mon.)

T+plus 6 minutes. Second stage engine performance is normal as the motor continues to fire.

0332 GMT (11:32 p.m. EDT Mon.)

T+plus 5 minutes. No problems have been reported with the rocket as it accelerates toward orbit.

0331 GMT (11:31 p.m. EDT Mon.)

T+plus 4 minutes, 30 seconds. NASA's Tracking and Data Relay Satellite System has acquired the vehicle's signal to receive telemetry for transmission to Sea Launch ground engineers. The second stage is still firing.

0331 GMT (11:31 p.m. EDT Mon.)

T+plus 4 minutes. The rocket's payload fairing, or nose cone, has been jettisoned. It protected the satellite cargo during atmospheric ascent. The nose cone will impact the Pacific about 600 miles downrange.

0330 GMT (11:30 p.m. EDT Mon.)

T+plus 3 minutes. Flight remains normal for the Sea Launch rocket following tonight's on-time liftoff. The second stage engine is up and burning.

0329 GMT (11:29 p.m. EDT Mon.)

T+plus 2 minutes, 45 seconds. The second stage engine has been ignited for its firing.

0329 GMT (11:29 p.m. EDT Mon.)

T+plus 2 minutes, 35 seconds. The first stage RD-171 engine has shut down and the spent stage was jettisoned. It will impact the Pacific Ocean approximately 500 miles downrange from the Odyssey launch platform.

0328 GMT (11:28 p.m. EDT Mon.)

T+plus 1 minute, 10 seconds. The vehicle has passed through the region of maximum dynamic pressure.

0327 GMT (11:27 p.m. EDT Mon.)

T+plus 45 seconds. The 20-story Zenit 3SL rocket is riding the thrust of the first stage main engine. The Russian-made engine has four nozzles and powers the rocket for the first two-and-a-half minutes of flight.

0327 GMT (11:27 p.m. EDT Mon.)

LIFTOFF! Liftoff of the Zenit rocket launching South Korea's first dual military and civil communications satellite.

0326 GMT (11:26 p.m. EDT Mon.)

T-minus 1 minute and counting. Final status checks are being taken as the automated launch sequence enters the final 60 seconds.

0324 GMT (11:24 p.m. EDT Mon.)

Now inside the last three minute of the count.

0321 GMT (11:21 p.m. EDT Mon.)

T-minus 6 minutes and counting. All systems appear "go" for liftoff from the Odyssey launch platform.

0315 GMT (11:15 p.m. EDT Mon.)

T-minus 12 minutes. Weather conditions are favorable and no technical problems are being reported in the countdown.

0311 GMT (11:11 p.m. EDT Mon.)

T-minus 16 minutes and counting. The transporter/erector arm is pulling away from the Sea Launch Zenit 3SL rocket right now. The arm was used to roll the rocket out of the environmentally-controlled hangar atop the Odyssey platform and lift the rocket upright.

The arm is being lowered to the platform deck where it will be returned to the hangar and the doors closed for launch.

Fueling operations have been completed aboard the Odyssey platform. Over the past couple of hours, the rocket was loaded with kerosene propellant and cryogenic liquid oxygen. The platform was cleared of all workers prior to this hazardous activity, with all personnel moved to the Sea Launch Commander ship safely positioned about three miles uprange.

MONDAY, AUGUST 21, 2006

A Sea Launch Zenit 3SL rocket will launch the Koreasat 5 dual commercial and military communications satellite tonight from a floating platform stationed in the equatorial waters of the Pacific Ocean.

Liftoff is scheduled for 0327 GMT (11:27 p.m. EDT). The available launch window extends an hour.

The Odyssey launch platform is positioned along the Equator at 154 degrees West longitude. The rocket will fly eastward, ultimately releasing its payload high above eastern Africa.

The Sea Launch fleet reached the launch site a few days ago after steaming for more than a week from the company's home port in Long Beach, California. The ocean-going launch pad known as Odyssey set sail first, followed later by the departure of the Sea Launch Commander vessel, which houses the management, official guests and launch control center.

Odyssey's ballast tanks were filled with seawater upon arrival, dropping the converted Norwegian oil-drilling platform to the launch depth of 65 feet. Control teams also commenced the standard 72-hour countdown. The Sea Launch Commander then pulled alongside Odyssey to allow workers to easily transfer between the two ships. The Zenit 3SL rocket was rolled out from its transport hangar aboard Odyssey and erected on the launch pedestal on Sunday.

The three-stage Zenit booster - making its 22nd flight in this configuration - will take just over an hour to complete its role to deliver the Koreasat 5 payload into a planned orbit with a low point of 1,816 miles and a high point of about 22,166 miles. The injection orbit's inclination will be zero degrees.

Over the next few weeks, Koreasat 5 will use its propulsion system to gradually raise its orbit to geostationary altitude, where its velocity will match that of Earth's rotation. The satellite will be positioned along the Equator at 113 degrees East longitude.

It will be South Korea's first dual military and civil communications satellite, with ownership shared between the Agency for Defense Development of Korea and KT Corporation.

Built by Alcatel Alenia Space, the 9,806-pound satellite is equipped with 24 Ku-band transponders for commercial broadcasting, plus four Ka-band transponders and eight super-high frequency (SHF) channels for military use. The Spacebus 4000 C1-model craft has a service life of 15 years.

Controllers will spend the last hours of today's launch countdown making final preparations to the rocket, payload and ground infrastructure. The Sea Launch Commander will pull away from the launch platform to a safe viewing distance about three miles away.

Fueling operations will get underway about two-and-a-half hours prior to the scheduled launch time. A mix of refined kerosene and liquid oxygen comprise the propellant used by all three stages of the launch vehicle.

After liftoff, the Zenit 3SL will fly downrange on a due east trajectory hugging the Equator. The first stage's Ukrainian four-chamber RD-171 engine ramps up to a maximum of 1.6 million pounds of thrust during its burn lasting two-and-a-half minutes. After first stage separation, the second stage's RD-120 powerplant will come to life. During the second stage firing, the payload fairing shielding the Koreasat 5 satellite during the flight through the denser lower atmosphere will be jettisoned.

Eight minutes, 31 seconds after blastoff is the point when the second stage will separate from the Block-DM upper stage and payload. Ten seconds later, the Block-DM will ignite for an eight-and-a-half minute burn to place itself in a temporary parking orbit with a low point of 112 miles and a high point of 6,357 miles. After an extended coast phase, the stage will ignite again at T+Plus 51 minutes, 13 seconds to inject Koreasat 5 into its targeted geostationary transfer orbit. Spacecraft separation is expected 65 minutes after liftoff.

Check this page during the launch for live updates on the mission's progress.