Experts from the Japan Aerospace Exploration Agency will certify any commercial crew transportation vehicle put forward by U.S. companies as safe to fly. Only then will the Japanese agency accept them as substitutes for the space shuttle in the complex barter deals that govern International Space Station operations.

Under those arrangements, reached before the Columbia accident on Feb. 1, 2003, sounded the death knell for shuttle operations, NASA is responsible for delivering Japanese astronauts to the ISS, where U.S. scientists have access to some of the equipment and rack space on the Japanese Experiment Module (JEM).

With the retirement of the shuttle later this year, NASA will pay as much as $55.8 million a person for seats and training on Russia’s Soyuz crew capsules to accommodate its own astronauts and those from Europe and Canada as well as from Japan. The U.S. agency is working with several U.S. companies—notably Space Exploration Technologies (SpaceX) and Orbital Sciences Corp.—for space taxis, funded privately in part, that would offer alternate routes to the ISS for crews and cargo.

“If NASA proposes a U.S. commercial transportation system, we will carefully review the safety function of the vehicle and the environment of the astronauts,” says Kiyoshi Higuchi, vice president of JAXA. “Probably we will use that one, [but] we have enough experience to review how safe it is. Indeed, we learned a lot from the United States.”

Both SpaceX and Orbital hope to reach the station with cargo by the end of this year, and both companies are pushing development of human-rated vehicles, too. Once the shuttle retires, NASA will need commercial cargo delivery to maintain a six-person crew at the station, and it hopes to begin using commercial crew vehicles as soon as possible as a way to build a private space industry in the U.S.

Currently, Japan has two astronauts scheduled to fly on Soyuz vehicles to the ISS: Dr. Satoshi Furukawa, set to launch on Soyuz TMA-02M on May 30 to join Expedition 28, and Akihiko Hoshide, a member of Expedition 33. A third, Soichi Noguchi, flew to the station on Soyuz TMA-17 in December 2009 for a six-month stay with Expeditions 22 and 23.

In the long term, says Higuchi, Japan wants to have its own capability to send astronauts to orbit. But for now, it is playing an important supply role with unpiloted cargo vehicles.

Japan’s second H-II Transfer Vehicle (HTV-2), dubbed Kounotori, reached the station Jan. 27, and crews are using their Canadian and Japanese robotic arms to unpack spare parts from the vehicle’s unpressurized section while unloading pressurized cargo from its interior.

Overall, the HTV-2 carried 5.3 tons of cargo, including spare parts, food, water and scientific equipment. Japan plans to build five more HTVs to deliver supplies through 2015, and Higuchi says it will build more after that, now that the U.S. has agreed to fund the space station until at least 2020.

The exact number of HTVs remains to be worked out within the Japanese government and among the space station partnership, he says. Those ongoing discussions will be part of a larger adjustment in Japan to the new U.S. approach to space exploration.

Under the old U.S. space policy established under then-President George W. Bush following the Columbia accident, Japan took an active role in working with the space station partners and other spacefaring nations to plan an architecture for lunar exploration. That work is very advanced, Higuchi says, but will need to be redone to accommodate the new U.S. approach.

“We have agreed to extend the ISS five years, so that means we have a lot of time to discuss [next steps],” he says. “Unfortunately, we don’t have much money, so we will have to investigate [what we can do] in more detail.”

JAXA is still working under its March 2005 Vision 2025 plan, through which it aims to achieve world-class status in aeronautics and space science, security, infrastructure and industry, with a heavy emphasis on lunar exploration. A top-level space-policy planning panel is at work to accommodate Japan’s tight space budgets and the changing plans in the U.S., traditionally Japan’s top space partner.

A new Japanese space law adopted since the release of the 2025 Vision document also gives JAXA a bigger role in national-security space activities. But the legislation governing JAXA activities remains unchanged and focused on civil space for now, Higuchi says. That means more work on the ISS, both by Japanese scientists and engineers and through the Asia-Pacific Regional Space Agency Forum, which strives to make station resources available to researchers representing some 30 agencies across the region.

Higuchi was here last week to play host to an annual space community gathering at the Japanese ambassador’s residence and hold informal discussions with his NASA colleagues. No formal agreements were reached, he says, but work advanced on plans for Japan’s second lunar orbiter, Selene-2, which will include a Japanese lander and U.S. scientific instruments.

He also visited Goddard Space Flight Center, where he saw the Global Precipitation Measurement (GPM) spacecraft. In preparation at Goddard for an H-IIA launch in 2013, GPM is a joint JAXA/NASA mission to conduct worldwide study of rain, snow and ice precipitation.