ASCA, a model of international collaboration

ISAS is the central research institute for space and astronautical science in Japan; more practical and/or commercial uses of space (weather and communication satellites, for example) are the domain of a separate space agency, NASDA. ISAS has been launching scientific satellites since 1970, at a rate of roughly one satellite per year. X-ray astronomy has become one of the major research areas for ISAS, with the successful launches of Hakucho (1979), Tenma (1983), and Ginga (1987).

Even with such a strong tradition and a large accumulation of expertise at ISAS and at several major Japanese universities, they felt they could benefit greatly from an international collaboration for their 4th X-ray astronomy satellite, in this case with the US. This was partly due to the sheer increase in complexity and sophistication of the satellite they hoped to build. Additionally, there were specific areas in which the US had a clear lead over Japan. By forging a collaboration between US and Japanese groups, they hoped to create new centers of expertise in several new areas.

From the US point of view, the collaboration with ISAS provided an opportunity to participate in a mission that would develop and utilized new technology in a timely manner. Although the launch capabilities of ISAS rockets are modest, they have been reliable; ISAS also has an unparalleled reputation for on-time completion of their projects. On the other hand, NASA had temporarily gotten away from regular launch opportunities for small and medium sized satellites, during the '80s and the early '90s.

NASA's contribution to ASCA has been in the conical foil X-ray mirrors, in the X-ray CCD cameras, and in software. In return, US scientists have enjoyed access to 40 % of observing time on ASCA; 15 % of the total observing time is reserved for the exclusive use of the US guest observers, and an additional 25 % of time is earmarked for collaborative US-Japanese observations. The latter block of time has successfully fostered many collaborations among scientists from the US and Japan.