Artist's concept of the HTV's re-entry.
Packed with garbage from the International Space Station, the first HTV cargo freighter met a fiery demise over the Pacific Ocean on Sunday, punctuating an historic chapter in the Japanese space program.
The 33-foot-long cylindrical spaceship barreled into the upper atmosphere around 2126 GMT (4:26 p.m. EST) over the Pacific Ocean just off the coast of New Zealand, according to the Japan Aerospace Exploration Agency.
The H-2 Transfer Vehicle fired its engines three times Sunday to slow its speed by 199 mph, just enough to drop its orbit into the atmosphere and fall from space.
The final engine firing lasted eight minutes and wrapped up at 2101 GMT (4:01 p.m. EST) as the spacecraft flew near the southern half of Japan.
Although Japanese officials expected the bulk of the freighter to burn up during re-entry, some chunks of the spacecraft could have hit the Pacific Ocean. The ship's propellant tanks were most likely to have survived.
"Most of the vehicle components are expected to be destroyed and burned out encountering the aerodynamic heating during the re-entry, but some of the debris is estimated to survive and fall into the South Pacific Ocean," JAXA said in a written statement.
Debris from the HTV would have likely fallen in a rectangular box stretching across the Pacific Ocean between New Zealand and South America, according to JAXA.
The HTV mission's ending Sunday closed out a 52-day inaugural mission that began in the wee hours of the morning Sept. 11, Japanese time, at the picturesque spaceport on Tanegashima Island off the southern coast of Japan.
Launching on an H-2B rocket specifically built for the logistics ship, the HTV spent a week undergoing orbital trials before it was cleared to approach the space station.
The craft closed within 30 feet of the complex Sept. 17, close enough for astronaut Nicole Stott to grapple the free-flying HTV using the station's robot arm.
The arm berthed the ship to the Earth-facing port of the outpost's Harmony module, where it stayed for 43 days.
The product of more than $1.1 billion in rocket and spacecraft development, the first HTV brought about 7,500 pounds of supplies and experiments to the space station.
Comprising about 2,000 pounds of that mass were two Earth science experiments mounted on an exposed platform on the HTV. Both payloads were attached to the outdoor science deck of the Kibo laboratory module.
The NASA HREP instrument carries two experiments to study the oceans and atmosphere. HREP's ocean sensor will focus on coastal features, and the atmospheric ultraviolet and visible instrument will look at the ionosphere and thermosphere.
JAXA's SMILES experiment will detect trace gases in the ozone layer using a submillimeter sounder. The 1,047-pound instrument will help determine the extent of human activity's affects on ozone.
About 5,475 pounds of supplies were hauled to the station inside the HTV's pressurized section.
This cargo included food, computers, experiments, crew provisions and other maintenance equipment.
After unloading the supplies, the station residents packed the ship with trash to free up storage space on the complex. The HTV was filled with 1,600 pounds of garbage when it left the station Friday.
Six more HTV flights are on the books, flying at a pace of about one per year through about 2016. The next Japanese cargo mission is slated for the end of next year.
HTV missions will be a key part of the resupply strategy for the space station after the space shuttle's retirement next year.
After the shuttle is removed from service, the HTV will be the only spacecraft capable of delivering large external hardware to the complex, such as science experiments and spare parts called Orbital Replacement Units, or ORUs.
The last few shuttle flights are filled with ORUs to stock the station with replacement equipment.
Europe's Automated Transfer Vehicle, which first flew last year, can't carry unpressurized equipment. The venerable Russian Progress logistics freighter is also restricted to pressurized cargo.
New spacecraft being developed by SpaceX and Orbital Sciences Corp. could accommodate larger payloads for the station's exterior, but both ships may not be operational until 2011.
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