The 174-foot-tall rocket lit its hydrogen-fueled main engine and two 49-foot-long solid rocket boosters, which delivered 1.6 million pounds of thrust to push the launcher off the pad at the Tanegashima Space Center.

Liftoff occurred at 2158:22 GMT (5:58:22 p.m. EDT), the precise instant when Earth's rotation aligned the Tanegashima launch pad with the trajectory toward Venus.

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Another NASA station in Australia will next communicate with the spacecraft, before Akatsuki passes in view of a JAXA site in Uchinoura, Japan early Friday.

If Akatsuki is required to do a post-launch trajectory correction burn, it will occur in range of the Uchinoura station.

JAXA has also issued a post-launch press release:

"Mitsubishi Heavy Industries, Ltd. and the Japan Aerospace Exploration Agency (JAXA) launched the Venus Climate Orbiter "AKATSUKI" (PLANET-C) aboard H-IIA Launch Vehicle No. 17 (H-IIA F17) at 6:58:22 a.m. on May 21, 2010 (Japan Standard Time, JST) from the Tanegashima Space Center."

"The launch vehicle flew smoothly, and, at about 27 minutes and 29 seconds after liftoff, the separation of the AKATSUKI was confirmed."

"We would like to express our profound appreciation for the cooperation and support of all related personnel and organizations that helped contribute to the successful launch of the H-IIA F17."

"At the time of the launch, the weather was light cloudiness, a wind speed was 2.4 meters/second from the north-north-east, and the temperature was 21.2 degrees Celsius."

The vehicle has now amassed 16 successful launches in 17 tries since its debut mission in 2001. The next H-2A launch is scheduled for this summer with the Quasi-Zenith Satellite to augment Global Positioning System signals over Japanese territory.

One more payload, the UNITEC-1 university-built test satellite, should be released in a few minutes to complete the launch.

Plans call for the spacecraft's two solar panels to deploy in about five minutes, but the first acquisition of signal from the new orbiter will not occur until around 0100 GMT (9 p.m. EDT) as it passes over a NASA tracking station in Goldstone, Calif.

The second stage LE-5B engine will fire for nearly 5 minutes during this first burn of the mission to place the vehicle into low Earth orbit.

The ignition sequence of the first stage engine begins 5.2 seconds before liftoff. Solid rocket booster ignitions occurs at T-zero.

The ignition sequence of the first stage engine begins 5.2 seconds before liftoff. Solid rocket booster ignitions occurs at T-zero.

The current conditions are a temperature of 67 degrees Fahrenheit and northeast winds of about 7 mph.

The automatic sequence will begin at T-minus 4 minutes, 30 seconds and computers will pressurize the H-2A's propellant tanks for flight at about T-minus 4 minutes, 20 seconds.

At about T-minus 3 minutes, the launcher will transition to internal battery power and remove external power.

Water will be released onto the launch pad deck beginning at T-minus 73 seconds to help suppress sound and acoustics during the ignition and liftoff. The vehicle's pyrotechnic and ordnance systems will be armed at T-minus 30 seconds and the rocket's guidance system initializes at T-minus 18 seconds. Batteries controlling solid rocket booster ignition are activated at T-minus 15 seconds.

Sparklers underneath the rocket's main engine ignite at T-minus 11.7 seconds to burn off residual hydrogen that could be an explosive hazard at main engine start.

The rocket will pitch east from Tanegashima, racing through the speed of sound in less than a minute and reaching an altitude of more than 30 miles in the first two minutes of flight.

After consuming their pre-packed solid propellant, the two strap-on boosters will jettison in two pairs just after the two-minute point. The 13.1-foot diameter payload shroud will separate at T+plus 4 minutes, 19 seconds after the H-2A rocket ascends above the discernable traces of Earth's atmosphere.

First stage main engine cutoff, stage separation and ignition of the second stage's LE-5B engine will occur nearly seven minutes into the mission. The second stage will burn for more than eight minutes before shutting down at T+plus 11 minutes, 29 seconds.

After deploying three small CubeSat secondary payloads, the second stage will ignite again for four minutes before deploying the Akatsuki Venus orbiter at T+plus 27 minutes, 27 seconds.

Officials just gave the "go" to enter the terminal count, which began at 2058 GMT. The final hour of the countdown will prepare the rocket, the Akatsuki spacecraft, and ground systems for flight.

Today's launch is timed for precisely 2158:22 GMT (5:58:22 p.m. EDT; 6:58:22 a.m. JST), when the Earth's rotation will bring Tanegashima in perfect alignment with the desired interplanetary trajectory toward Venus. The rocket must launch at the appointed time because there is no launch window available.

Mitsubishi Heavy Industries, the H-2A rocket's prime contractor, reports radio frequency checks between the vehicle and ground stations has been completed as planned. A second steering check of the rocket's engines has also been accomplished.

Another "go/no go" decision point is coming up soon, before the countdown enters the terminal phase at T-minus 60 minutes.

Also check out a new photo gallery showing the H-2A rocket's second rollout.

The first stage LE-7A engine consumes hydrogen during its six-and-a-half minute firing. The second stage's LE-5B powerplant will ignite twice to place the Akatsuki orbiter on track for Venus.

The H-2A's two solid rocket boosters burn solid propellant, which has already been packed inside the motors.

After moving to the launch pad overnight, the 174-foot-tall rocket was hooked up to the launch pad through fueling, electrical and communications lines. The countdown began at 1200 GMT (8 a.m. EDT).

Since then, the launch team has set up road blocks at the perimeter of a 3,000-meter keep-out zone.

Liquid hydrogen and liquid oxygen propellants are also flowing into the rocket's first and second stages. Once the tanks are full, more fuel will slowly be added throughout the countdown to replace the cryogenic propellant that naturally boils off.

And the rocket just finished the first of two engine steering checks planned for the countdown.

Liftoff will be at 6:58 a.m. Japanese time.

Japanese launch controllers called off the first try to launch the 17-story rocket Monday as thick clouds moved over the Tanegashima Space Center, causing an elevated risk of lightning.

Workers moved the 17-story rocket back to the Vehicle Assembly Building Tuesday. The launcher was transported back to the pad about an hour ago.

The weather forecast for Thursday calls for mostly clear skies, light winds, a temperature of 66 degrees Fahrenheit, and a 10 percent chance of rain showers.

The three-day launch delay will push back the arrival of the Akatsuki orbiter at Venus by one day to Dec. 7, according to a Japan Aerospace Exploration Agency spokesperson.

The delay also slightly changes the timeline of the H-2A rocket launch. You can view the updated sequence of launch events here.

The H-2A rocket was also moved back inside the Vehicle Assembly Building for turnaround processing to support the new launch attempt, which is scheduled for 2158:22 GMT (5:58:22 p.m. EDT), or 6:58 a.m. Japanese time.

The $275 million mission has until June 3 to launch when the planets are properly positioned in the solar system to make a voyage from Earth to Venus.

The forecast for Thursday calls for mostly cloudy skies and a slight chance of rain.

The automatic sequence will begin at T-minus 4 minutes, 30 seconds and computers will pressurize the H-2A's propellant tanks for flight at about T-minus 4 minutes, 20 seconds.

At about T-minus 3 minutes, the launcher will transition to internal battery power and remove external power.

Water will be released onto the launch pad deck beginning at T-minus 73 seconds to help suppress sound and acoustics during the ignition and liftoff. The vehicle's pyrotechnic and ordnance systems will be armed at T-minus 30 seconds and the rocket's guidance system initializes at T-minus 18 seconds. Batteries controlling solid rocket booster ignition are activated at T-minus 15 seconds.

Sparklers underneath the rocket's main engine ignite at T-minus 11.7 seconds to burn off residual hydrogen that could be an explosive hazard at main engine start.

The rocket will pitch east from Tanegashima, racing through the speed of sound in less than a minute and reaching an altitude of more than 30 miles in the first two minutes of flight.

After consuming their pre-packed solid propellant, the two strap-on boosters will jettison in two pairs just after the two-minute point. The 13.1-foot diameter payload shroud will separate at T+plus 4 minutes, 19 seconds after the H-2A rocket ascends above the discernable traces of Earth's atmosphere.

First stage main engine cutoff, stage separation and ignition of the second stage's LE-5B engine will occur nearly seven minutes into the mission. The second stage will burn for more than eight minutes before shutting down at T+plus 11 minutes, 29 seconds.

After deploying three small CubeSat secondary payloads, the second stage will ignite again for four minutes before deploying the Akatsuki Venus orbiter at T+plus 27 minutes, 50 seconds.

Officials just gave the "go" to enter the terminal count, which began at 2044 GMT. The final hour of the countdown will prepare the rocket, the Akatsuki spacecraft, and ground systems for flight.

Today's launch is timed for precisely 2144:14 GMT (5:44:14 p.m. EDT; 6:44:14 a.m. JST), when the Earth's rotation will bring Tanegashima in perfect alignment with the desired interplanetary trajectory toward Venus. The rocket must launch at the appointed time because there is no launch window available.

Earlier this hour, the rocket also completed a control check to ensure it can steer itself during the launch.

The weather forecast for liftoff calls for mostly cloudy skies, a temperature of 68 degrees Fahrenheit, and a 20 percent chance of rain showers.

Be sure to check out the launch timeline for today's H-2A rocket flight.

Radio frequency checks between the rocket communications system and tracking radars at Tanegashima are now underway. These tests confirm the ground stations can receive signals from the rocket during the launch.

The weather forecast also looks good for an on-time liftoff this evening.