"the first bilateral" US‑Japan cooperative space effort "focused on national security," the US Space Systems Command wrote in an Aug. 14 statement describing a pair of sensors now operating on Japanese satellites.
Quasi‑Zenith Satellite‑7 (QZS‑7): a Japanese GEO platform hosting U.S. sensors
Japan successfully launched Quasi‑Zenith Satellite‑7 (QZS‑7) on an H‑3 launch vehicle from Tanegashima Space Center (TNSC) on Aug. 10, according to the Space Systems Command release. Built by Mitsubishi Electric Corporation, QZS‑7 is the seventh and last satellite in the Quasi‑Zenith Satellite System (QZSS) constellation stationed in geosynchronous Earth orbit (GEO). The constellation is operated by the Japanese space agency JAXA and provides position, navigation and timing coordinates for both civilian and military uses.
Two U.S. Space Force sensors designed by MIT Lincoln Laboratory
The payloads riding on QZS‑6 and QZS‑7 are orbital neighborhood‑watch sensors designed and built by the Massachusetts Institute of Technology’s Lincoln Laboratory, the SSC statement said. The two sensors are intended to keep watch on the heavens above the Indo‑Pacific region and were planned as a bilateral effort between the United States and Japan.
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Get a security leadHow the sensors connect to the US Space Surveillance Network (SSN)
The sensors on the two QZSS satellites will feed space monitoring data to the US Space Surveillance Network (SSN), SSC said. The SSN is made up of ground‑based radar and telescopes on Earth and in space, and is operated by the 18th Space Defense Squadron, headquartered at Vandenberg Space Force Base in California.
Program origins: Pentagon agreement, funding timeline, and launch history
The Pentagon initiated the bilateral effort to host US sensors as payloads on QZS‑6 and QZS‑7 in 2019 as part of a package of agreements to improve cooperation with Japan on space situational awareness. The US Space Force first provided funding for the program in fiscal 2021, with the expectation that QZS‑6 would fly in calendar 2023 and QZS‑7 the following year. The first of the two sensors, SSC noted, was launched in February 2025; the QZS‑7 launch on Aug. 10 completed the pair.
What this means for the 18th Space Defense Squadron, JAXA, and Mitsubishi Electric Corporation
- 18th Space Defense Squadron: The squadron will receive additional space‑monitoring data streamed into the SSN, supplementing the network of ground radar and telescopes the unit operates.
- JAXA: As operator of the QZSS constellation, JAXA now hosts two U.S. military sensors across QZS‑6 and QZS‑7, extending the constellation’s role beyond civil positioning and timing to include bilateral national‑security monitoring functions.
- Mitsubishi Electric Corporation: The company supplied QZS‑7, the seventh GEO platform in the QZSS constellation, and provided the spacecraft that now carries the second of the two U.S. sensors.
The two Space Force sensors—designed by MIT Lincoln Laboratory, launched aboard QZS‑6 and QZS‑7, and now feeding the US Space Surveillance Network—represent a concrete, bilateral integration of U.S. national‑security payloads into Japan’s operational satellite constellation. The arrangement stems from a Pentagon initiative begun in 2019 and US funding that began in fiscal 2021, and it culminated with the Feb. 2025 deployment of the first sensor and the Aug. 10 launch of QZS‑7.
