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Japan's HTV-4 cargo ship berths with ISS

Paul Sutherland, Feature writer
Aug 10, 2013, 7:00 UTC

Sen—Astronauts aboard the International Space Station have welcomed a new visitor with the arrival of Japan’s fourth cargo ship at the orbiting outpost.

The unmanned HTV-4 craft, called Kounotori, or White Stork, was loaded with 3.6 tons of cargo including provisions for the crew, scientific equipment, computers, spare parts - and a humanoid robot called Kirobo.

It made a laser-guided approach towards the ISS before NASA astronauts Karen Nyberg and Chris Cassidy used a Canadian-built robotic arm to grab it and bring it in for berthing.

The HTV-4 (H-II Transfer Vehicle-4) launched on Saturday, 3 August, from Japan’s Tanegashima space centre. But unlike recent Soyuz craft which have taken the fast track to the ISS, the HTV-4 made a six-day journey to get there.

Over that time, a series of engine burns gradually lifted the freighter to an altitude of about 410km to match the height of the ISS ready for rendezvous.

The spacecraft reached a point 5km behind the ISS early Friday before pausing to allow mission controllers at NASA and the Japanese space agency JAXA to check its readiness to proceed further.

At 8.05 Universal Time, JAXA commanded the HTV to continue its approach until it reached another hold point 250 metres from the ISS at 9.30 UT. It then performed a 180° rotation to align with the robotic arm but also put it in a suitable position if it needed to abort its approach.

By this time, the craft was using laser navigation by firing beams at reflectors mounted beneath the space station to provide precise positional information.

Video showing the moment the HTV-4 was captured with the robotic arm. Credit: NASA TV

Half an hour later, the HTV resumed its slow approach until it reached another hold point just 30 metres below the Kibo laboratory module on the ISS where it remained for about 20 minutes.

It then began its final approach towards the ISS while Nyberg and Cassidy watched from the space station’s viewing gallery, the seven-paned cupola module. The third astronaut on board, ESA’s Luca Parmitano, stood ready to issue an abort or retreat command in case the HTV drifted from its approach track.

At 11.12 UT the space freighter reached its capture point, 10 metres from the ISS, and NASA mission controllers gave the go-ahead for capture. Nyberg steered the 18-metre long robotic arm until it grappled the craft.

It took longer than expected to align the HTV precisely as it was drawn in towards the ISS’s Harmony module for berthing. But finally, at 15.38 UT, the two craft were mated.

The ISS crew are due to open the hatches Saturday and begin the process of removing the supplies from Kounotori’s pressurized logistics carrier.

Three HTVs have already flown to the ISS – they were HTV-1 in September, 2009, HTV-2 in January, 2011, and HTV-3 in July, 2012.

Video of the successful berthing of the HTV-4 with the Harmony module. Credit: NASA TV