Japan launched a next-generation geostationary weather satellite Tuesday on the 25th flight of the country's H-2A rocket, deploying an upgraded meteorological observatory critical to the minute-by-minute tracking of tropical cyclones and other storm systems across the Asia-Pacific.

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Himawari 8 separation! Japan's newest weather satellite has been deployed in orbit following launch aboard an H-2A rocket.

The spacecraft will extend weather observations over the Asia-Pacific, supplying key data to forecasters from Japan, Australia, New Zealand, Southeast Asia and neighboring regions.

T+plus 27 minutes, 15 seconds. The second stage engine has switched off again, and the rocket is preparing to deploy the Himawari 8 satellite momentarily.

T+plus 24 minutes. The H-2A rocket's LE-5B second stage engine is firing again. The engine consumes liquid oxygen and liquid hydrogen propellants, generating a maximum thrust of about 31,000 pounds.

T+plus 20 minutes. Re-ignition of the second stage's LE-5B engine is less than 4 minutes away and will occur as the rocket crosses over the equator in the middle of the Pacific Ocean.

The burn will last about 3 minutes, 17 seconds, to place the Himawari 8 satellite into a geostationary transfer orbit with a high point of 35,976 kilometers (22,354 miles), a low point of 250 kilometers (155 miles) and an inclination of 22.4 degrees.

T+plus 12 minutes, 20 seconds. The second stage's LE-5B engine has cut off and the H-2A rocket has reached a parking orbit.

A second burn of the second stage engine is scheduled to begin at T+plus 23 minutes, 50 seconds.

T+plus 10 minutes. No problems have been reported thus far in the launch phase of the mission. The first cutoff of the second stage engine is scheduled for T+plus 12 minutes, 12 seconds.

Altitude is now 268 kilometers and velocity is about 6,100 m/s.

T+plus 7 minutes. First stage main engine cutoff, staging and second stage ignition have all occurred on time, according to JAXA. Velocity is now about 5,000 meters per second and altitude is about 230 kilometers.

Rocketing east across the Pacific Ocean, the second stage LE-5B engine will fire for more than five minutes during this first burn of the mission to place the vehicle into a parking orbit.

A second burn will come later to put Himawari 8 into a higher-altitude geostationary transfer orbit.

T+plus 4 minutes, 40 seconds. JAXA reports the four-meter-diameter payload fairing has been released from the rocket. The H-2A is now being powered by its LE-7A main engine at an altitude of 157 kilometers and a velocity of 2,800 meters per second.

T+plus 2 minutes. Burnout and separation of the twin solid rocket boosters that provided the bulk of thrust at liftoff. Altitude is now about 55 kilometers.

T+plus 60 seconds. The 17-story rocket has surpassed Mach 1 and is now experiencing the most extreme aerodynamic forces of its flight.

Liftoff of a Japanese H-2A rocket with Himawari 8, extending space-based weather observations over the Asia-Pacific!

T-minus 60 seconds and counting. Thousands of gallons of water are now being poured over the launch platform to cushion the structure from intense acoustic vibrations at launch. In the countdown's final minute, the rocket will be armed and the guidance system will start.

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

T-minus 90 seconds. The first and second stage propellant systems have been readied for launch.

T-minus 3 minutes. The H-2A rocket has switched to internal power.

T-minus 4 minutes, 30 seconds. The automatic countdown sequence has started and the H-2A rocket's propellant tanks will soon be pressurized for flight.

T-minus 5 minutes. The Himawari 8 payload is reported ready for launch.

T-minus 5 minutes, 30 seconds. The weather is acceptable for launch today, according to JAXA.

T-minus 7 minutes. The range safety system is reported ready for launch.

T-minus 10 minutes. The Himawari 8 spacecraft should soon be operating on internal battery power as the satellite and launcher are configured for liftoff at 0516 GMT (1:16 a.m. EDT).

T-minus 12 minutes. In the final minutes of the countdown, an automated sequencer will control the final crucial steps before launch.

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.

T-minus 20 minutes. Engineers are uploading the latest upper level wind data into the H-2A's flight computer. The rocket will use the information to compute a specific steering profile based on the real launch day weather conditions.

At liftoff, the H-2A will be propelled upward from the launch pad on the power of a single hydrogen-burning LE-7A main engine and two solid rocket motors. The total liftoff thrust of the rocket is approximately 1.6 million force pounds.

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 at about the two-minute point. The 13.1-foot diameter payload shroud will separate at T+plus 4 minutes, 5 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 five minutes before shutting down at T+plus 12 minutes, 12 seconds.

After a nearly 12-minute coast, the second stage will reignite for a 3-minute, 17-second burn.

Deployment of the Himawari 8 satellite is expected at T+plus 27 minutes, 57 seconds.

Some statistics on today's launch:

• 25th H-2A launch since 2001
• 36th H-2 family launch since 1994
• 14th launch of the H-2A (202) configuration
• 3rd launch from Tanegashima in 2014
• 61st space launch attempt worldwide in 2014

Now 60 minutes from the planned launch of the H-2A rocket.

Officials just gave the "go" to enter the terminal count, which began at 0416 GMT. The final hour of the countdown will prepare the rocket, the payloads, and ground systems for flight.

The H-2A rocket for today's launch is flying in the "202" configuration with two large 15-meter-long (49-foot) solid rocket boosters and without any of the smaller strap-on boosters sometimes used to augment the launcher's thrust.

It also features a standard four-meter (13.1-foot) diameter nose shroud, which encloses the Himawari 8 spacecraft for the first few minutes of flight through the lower atmosphere.

The lead contractor for the H-2A rocket is Mitsubishi Heavy Industries.

There are 75 minutes left in today's countdown before liftoff of the H-2A rocket with Himawari 8, a Japanese weather observatory to track tropical cyclones and storms across East Asia and the Western Pacific for the next eight years.

GPM weighs about 3.5 metric tons, or approximately 7,700 pounds, at the time of launch. It was built by Mitsubishi Electric Co. in Japan.

The spacecraft is fitted with the Advanced Himawari Imager, a camera that can scan the entire disk of Earth visible to Himawari 8 every 10 minutes, an improvement from every half-hour.

The instrument, which can see in 16 spectral bands, was manufactured in the United States by Exelis Geospatial Systems.

Himawari 8 is the eighth satellite in the Himawari -- which means sunflower -- series of spacecraft launched since 1977.

The satellite will raise its orbit to an altitude about 22,300 miles over the equator, where it will park itself at 140 degrees east longitude for an eight-year primary mission. The craft's components are designed to last up to 15 years.

It replaces the MTSAT 2 weather satellite launched in 2006.

See the launch timeline for details on the H-2A rocket's ascent into orbit with the Himawari 8.

We have also posted a cutaway diagram of the H-2A launch vehicle.

A second steering check of the rocket's engines has been accomplished, according to Mitsubishi Heavy Industries.

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

The Himawari 8 spacecraft is heading for a geostationary transfer orbit with an apogee of 35,976 kilometers, or 22,354 miles, a perigee of 250 kilometers, or 155 miles, and an inclination of 22.4 degrees.

Mitsubishi Heavy Industries, the H-2A rocket's contractor and commercial operator, reports the liquid hydrogen and liquid oxygen tanks aboard the launcher are now full of super-cold cryogenic propellant.

The next few hours of the countdown will be spent activating and checking out a variety of rocket systems, including radio frequency links with tracking stations. Another steering check of the rocket's main engine is also planned.

After testing is completed, officials will give the go-ahead for the terminal countdown scheduled to start at 0416 GMT. Liftoff remains set for 0516 GMT (1:16 a.m. EDT), or 2:16 p.m. local time at the Tanegashima Space Center in southern Japan.

Radio checks have been completed between the rocket and ground stations.

Slew checks of the H-2A rocket's first stage engine have been completed, verifying the powerplant will be able to steer the launcher during ascent.

Safety officials have established road blocks 400 meters from Launch Pad No. 1 of the Yoshinobu launch complex. The Yoshinobu launch complex was built for the H-2 rocket program that began operations in 1994 and has since been modified for use by the more powerful and H-2A rocket family.

The pads are positioned on a rocky outcrop on the southeastern flank of Tanegashima Island, which lies about 80 miles south of Kagoshima, Japan.

The complex features two pads for the H-2A and H-2B rockets. Launch Pad No. 2 has been used for four flights of the H-2B rocket with the H-2 Transfer Vehicle, an unmanned cargo ship for the International Space Station. In all, 35 rockets have departed Earth from the Yoshinobu complex since 1994. The most recent flight was an H-2A rocket launch in May 2014.

Launch officials report they are go for cryogenic fueling of the H-2A rocket. The launcher's two stages consume liquid hydrogen and liquid oxygen propellants. Two strap-on boosters attached to the first stage are already packed with solid fuel.

The LE-7A and LE-5B engines on each stage burn the super-cold propellants during the flight. Because the propellant is stored under cryogenic conditions, it must be gradually replenished throughout the countdown to ensure proper levels of fuel are inside the rocket at liftoff.

JAXA and Mitsubishi Heavy Industries, the H-2A rocket's prime contractor, report all systems are functioning well.

The orange, black and white rocket arrived at Launch Pad No. 1 at Tanegashima's Yoshinobu launch complex a few hours ago to begin preparations for fueling, including the connection of fuel lines and data and electrical cables between the ground complex and the rocket.

A space-based weather monitor, equipped with upgraded instruments for more detailed and timely data on tropical cyclones and thunderstorms, is scheduled for launch Tuesday on top of Japan's 25th H-2A rocket.

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