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Japanese cargo ship snagged by space station robot arm

Posted: September 17, 2009

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In a precise orbital ballet more than 200 miles above the planet, a bus-sized Japanese cargo ship approached the International Space Station on Thursday and astronaut Nicole Stott plucked the satellite from space using the complex's robot arm.

Credit: NASA TV
The challenging procedure, called a free-flyer capture, has been used on countless space shuttle missions but never before aboard the space station.

Similar techniques will be critical for future commercial spacecraft that will take over supplying the U.S. segment after the space shuttle retires next year.

Stretching about 33 feet long and 14 feet wide, the H-2 Transfer Vehicle approached the station like clockwork, stopping and starting nearly exactly as planned as it pushed closer to the outpost.

The rendezvous briefly fell behind schedule as engineers studied rising temperatures inside some of the HTV's thrusters, but the ship quickly made up the time and reached the station a few minutes before planned.

The barrel-shaped spacecraft arrived and loitered at a point about 30 feet below the station, long enough for Stott to grapple the free-floating spaceship with the outpost's Canadian robot arm at 1947 GMT (3:47 p.m. EDT).

Stott snagged the HTV from space as the station was in a nighttime orbital pass over western Romania.

Applause rang out in the control center in Houston when engineers confirmed the arm had a firm grasp on the HTV a few minutes later.

"It's a real example of international cooperation with a Japanese vehicle captured by a Canadian arm with American and European astronauts and a safety guy from Canada and under the command of a Russian commander," said Frank De Winne, a European astronaut serving as flight engineer.

De Winne and Stott, assisted by Canadian astronaut Bob Thirsk, oversaw the rendezvous from the station's Destiny laboratory.

"We're all here and we all just want to say congratulations to the entire (team). We had an amazing time doing this. We are so, so happy to have this beautiful vehicle here with us now and we look very forward to going in tomorrow and finding all the surprises I'm sure you've stowed there for us," Stott said as she addressed Japanese flight controllers.

Thirsk took over control of the arm a few minutes after snaring the HTV and guided the captive ship to its new home on the Harmony module's Earth-facing berthing port.

A series of latches and bolts were driven to mate the HTV to the station, and NASA declared the ship was firmly attached at 2226 GMT (6:26 p.m. EDT).

The crew opened the Harmony port's hatch at 0130 GMT Friday (9:30 p.m. EDT Thursday) and hooked up power and data transmission cables before going to sleep.

Credit: NASA TV
Engineers on the ground will continue remotely activating the HTV overnight and preparing the craft for ingress on Friday.

Plans call for the station residents to open the final hatch and enter the HTV around 1820 GMT (2:20 p.m. EDT) Friday to begin unpacking some 7,366 pounds of gear.

About 5,475 pounds of that equipment are loaded into resupply bags and storage racks inside the HTV's forward pressurized section.

The internal supplies include 1,890 pounds of food, 1,249 pounds of payloads, 384 pounds of crew provisions, 215 pounds of computer equipment and an assortment of other items, according to NASA.

It will take 70 crew hours to unload all the equipment and stow it inside the station.

Unlike other unpiloted cargo ships, the HTV also carries external experiments mounted on an outdoor pallet. The payloads were provided by NASA and the Japan Aerospace Exploration Agency, or JAXA.

The 839-pound NASA payload, called HREP, holds 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 1,049-pound instrument will help determine the extent of human activity's affects on ozone.

HREP and SMILES are the station's first significant science payloads devoted to Earth science.

"It's good to be able to finally start having this kind of research on board the ISS," Suffredini said.

Thirsk will again use the station's robot arm on Wednesday to reach into the HTV and remove the external pallet containing HREP and SMILES.

The pallet will be handed off to the Japanese arm operated by De Winne, who will place the crate on the Kibo lab's exposed facility.

Next Thursday, the Japanese arm will grab each experiment and place them on powered mounts on Kibo's outside science deck. HREP will be moved first, followed a few hours later by the transfer of SMILES.

If all goes as planned, the empty pallet will be placed back into the HTV's unpressurized carrier on Friday.

"The pallet is removed and inserted a lot like a common dresser drawer. It's got wheels along the edges of the pallet and there are guide rails inside the HTV," said Dana Weigel, NASA's lead flight director for the HTV mission.

On future HTV missions, the pallet could also carry large spare components to replace aging or failed parts on the station.

"What's unique about HTV is it's capable of transferring unpressurized cargo. This capability is, at this point, unique to only the space shuttle and the HTV," said Hiro Uematsu, a senior engineer on the HTV spacecraft.

Once station residents unpack the supplies brought to space by the HTV, they will begin gathering trash to load inside the empty vessel for disposal.

The trash will be destroyed along with the HTV when it enters the atmosphere over the South Pacific at the end of its mission.

Officials have not made a final decision on the length of the ship's stay at the complex, although the HTV is designed for a maximum mission duration of 55 days, according to JAXA.

Current timelines show departure penciled in for early November, but that date could change over the next few weeks.