Space-Based Missile Warning: An Opportunity to Deepen U.S.-Japan Security Cooperation

In recent years, Japan has taken steps toward developing its own missile-warning satellites. Developing a space-based missile-warning system is a challenging feat, one that is complex and expensive, evidenced by the fact that only a few countries operate such systems. Given that the U.S. already shares some missile-warning information with Japan, Tokyo’s pursuit of its own satellites reflects, at least in part, the country’s push toward achieving a more independent capability. However, this push should not be construed as sudden or a shift away from its longtime ally. Rather, it represents (1) a continuation of latent historical efforts to acquire missile-warning satellites, and (2) a response to technological developments that have made potential adversarial missile systems more threatening and developing missile-warning satellites more feasible. Japan’s pursuit of missile-warning satellites fits within Japan’s broader acceleration as a defense power and contributor to the U.S.-Japan security relationship. It also presents a compelling opportunity for more extensive collaboration between the two allies.