Discussions are under way between the US and Japan on the latter joining the Hypersonic and Ballistic Tracking Space Sensor (HBTSS). Japanese media on 25 July quoted confirmation of these talks from a Missile Defense Agency spokesperson.
HBTSS is a new space-based network of sensors in low earth orbit that can detect and track hypersonic weapons. Data collected will be fed to fire control systems for engagement.
Developed by the DoD in response to the growing threat posed by Chinese and Russian hypersonic weapons, HBTSS is set to receive an extra $120 million in funding under proposals from the US Senate.
Hypersonic glide weapons under development in China and Russia fly at speeds of up to Mach 5 at relatively low altitudes, making them difficult to find and interdict with existing missile defence systems. Japan itself has shown interest in developing an offensive hypersonic missile capability.