A senior government official here said cancell a tion of the international space station’s Japanese-built centrifuge module, an option under consideration at NASA, could severely undermine the public’s confidence in Japan’s space program and make it more difficult to pursue cooperative projects with the United States.

“If the centrifuge is not launched, politicians and people will question the role that Japan has played in the international space station,” Masanori Shinano, director of Space Utilization and Promotion with Japan’s Ministry of Education, Culture, Sports, Science and Technology, said March 25. The ministry oversees most Japanese space programs.

The centrifuge is designed to provide partial gravity aboard the space station for biomedical experiments and other scientific research. It is being supplied by the Japan Aerospace Exploration Agency (JAXA) under a barter agreement that calls for NASA to launch the Japanese Experiments Module to the space station aboard the space shuttle.

But the centrifuge project has been plagued by technical and budgetary woes that have steadily pushed back its launch date and eroded its capabilities. Now NASA is looking for ways to reduce the number of shuttle missions necessary to complete the space station so the orbiter fleet can be retired in 2010 as called for in U.S. President George W. Bush’s plan to return astronauts to the Moon.

NASA last year launched an internal review aimed at identifying those elements of the space station that contribute directly to the space agency’s new exploration mandate. Those that don’t contribute to sending astronauts to the Moon by 2020 or to Mars sometime thereafter could be scrapped.

NASA intends to complete its review by May and insists that no decisions have been made.

NASA spokeswoman Debra Rahn said March 30 that while the U.S. space agency “will likely redirect some elements” of its space station research program in order to “address critical medical and technical risks associated with space exploration,” it is “still too early to tell if there will be any impact to specific station facilities.”

But there is growing consensus among NASA watchers and experts that the centrifuge will be sacrificed in the name of NASA’s longer-term goal.

NASA first informed the Japanese that it was re-evaluating its space station research agenda in January at a space station head of agencies meeting in Montreal, said Emi Takizawa, a spokeswoman for JAXA. NASA “may propose some redirection of elements based on these priorities” but has yet to inform JAXA of its plans, Takizawa said via e-mail March 25.

A Japanese government official familiar with the discussions between NASA and JAXA, who asked not to be named, said JAXA has informally expressed concern about the possible cancellation of the centrifuge a number of times.

Rahn said NASA has k ept all of its partners up to date on its ongoing assessment and would “continue to coordinate closely with any partners that could be affected by NASA’s decisions on its research efforts using the station.”

The lead contractor on the centrifuge is Mitsubishi Heavy Industries of Tokyo. Yoshiharu Kurihara, deputy general manager of the company’s Space Systems Department, said via e-mail that all is going well with centrifuge development but declined to comment further.

The centrifuge program consists of three main elements: the Centrifuge Accomodation Module , the Centrifuge Rotor and the Life Sciences Glovebox.

NASA’s Ames Research Center is responsible for building an Advanced Animal Habitats facility that would house the centrifuge’s research subjects .

NASA spokeswoman Tracy Young said the Centrifuge Accommodation Module and rotor are slated for delivery to the Kennedy Space Center in Florida in May 2006. The Life Sciences Glovebox is scheduled to arrive in July 2007, she said.

Shinano acknowledged the centrifuge belongs to NASA and that Japanese researchers have no plans to use the hardware. But he said canceling the project could leave Japan with nothing to show for its $700 million investment in the project. The public criticism that likely would follow would make it difficult to secure funds for big-ticket space projects in the future and could make Japan wary of cooperating with NASA, he said.

But one former senior Japanese government official said cancellation of the centrifuge might be welcomed in some circles because it would free-up scarce resources for other space programs. “I guess [Mitsubishi] might be angry,” the source said in a March 29 telephone interview. “However, in reality, JAXA has no choice but to accept NASA’s decisions on the station, but also they are in the same position because of the lack of money. JAXA is planning many new programs, so for the long-term planning, it could be a relief.”

Staff Writer Brian Berger contributed to this article from Washington.