Page last updated at 22:41 GMT, Thursday, 17 September 2009 23:41 UK

Station grabs Japanese freighter

By Jonathan Amos
Science reporter, BBC News


Japan space freighter docks

Japan's new unmanned space freighter has been safely berthed to the International Space Station (ISS).

The H-II Transfer Vehicle (HTV) moved itself to within 10m of the ISS to allow itself to be grabbed by the platform's robotic arm.

The arm, operated from inside the station by astronauts Nicole Stott and Bob Thirsk, then moved the freighter to a docking port to lock it in place.

The HTV is carrying about 4.5 tonnes of supplies for the station.

These stores include food, water, clothing, laptops and other equipment.

The new vessel is one of Japan's major contributions to the orbiting project and is part of the barter agreement it has with the other station partners to pay its way.

The HTVs that follow in the coming years will play a critical role in servicing the ISS after the US space shuttles are retired.

This initial freighter was launched from the Tanegashima base in the south of Japan last week.

It is the first spacecraft to visit the ISS which does not drive itself all the way to berthing. Rather, it simply parks up under the bow of the station to allow the platform's Canadarm2 to manage the final stage of attachment.

The HTV was grabbed by the robotic lever at 1947 GMT, and was docked to the Earth-facing port of the ISS Harmony node just over two-and-a-half-hours later at 2226 GMT.

HTV impression (Jaxa)
Length: 9.8m; Diameter: 4.4m; Vehicle Mass: 10.5t; Max cargo: 6t
Pressurised cargo: Food, clothing, water, laptops, science equipment, etc
External cargo: Equipment to study Earth's oceans and the atmosphere
First unmanned vehicle to deliver both pressurised and unpressurised cargo

In addition to the cargo (3.6t) carried in the HTV's pressurised compartment (accessed from inside the ISS), the ship has important cargo (900kg) mounted on a pallet in an unpressurised compartment.

These exterior supplies include two new Earth-observation experiments for the exposed "terrace" of instruments that sits outside Japan's Kibo science module.

In the next few days, astronauts will again use the station arm to remove the pallet before handing it across to the Kibo arm, which will then position the new experiments.

As the astronauts deplete the HTV's pressurised supplies, they will fill the empty storage racks with rubbish. In six weeks' time, the freighter will be detached from the ISS before taking itself and the waste into a controlled burn-up over the Pacific Ocean.

When the US shuttles retire at the end of next year or the beginning of 2011, the ISS project will become dependent on five robotic freighters for its logistics:

• The Russian Progress and European ATV have already demonstrated their flight capability. Four more ATVs have been booked to fly to the station, one a year starting in 2010.

• After the first HTV mission, Japan plans a further six flights through to 2015.

• Two commercial US suppliers, SpaceX and Orbital Sciences, are in the process of developing their Dragon and Cygnus supply ships. The first of these is scheduled to deliver supplies to the ISS no earlier than the end of 2010.

HTV and Dragon are particularly important because of their ability to deliver larger items in their unpressurised compartments that would not normally fit through the docking port of a pressurised compartment.

How the HTV docks at the station (JAXA)

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