An American space surveillance sensor rode Japan’s final navigation satellite into orbit, giving the US a new watch post over Chinese activity in a contested stretch of geosynchronous space.
Japan’s H3 rocket launched the QZS-7 satellite, also called Michibiki No. 7, on Aug. 10 from Tanegashima Space Center. The satellite completed Japan’s seven-orbiter Quasi-Zenith Satellite System, a network that frees the country from reliance on GPS signals.
Tucked alongside the positioning hardware was a US Space Force optical sensor. The Space Systems Command confirmed the launch Aug. 14, calling it a US sovereign space domain awareness payload that flew with Japan’s cooperation.
The payload is built around SACHI cameras developed at MIT Lincoln Laboratory that are designed to watch Chinese satellite activity in geosynchronous orbit above the Indo-Pacific region. The sensor draws on a partnership where the US and Japan share space domain awareness data to track threats to their satellites.
Japan’s navigation constellation uses highly inclined geosynchronous orbits that keep orbiters overhead for hours, a geometry that also offers useful dwell time for an optical sensor watching a specific patch of the geosynchronous belt. The launch was the ninth flight of the H3 rocket, which lost a navigation satellite in December 2025 to a manufacturing defect.
