Two surveillance sensors designed and built at MIT Lincoln Laboratory in Lexington are now circling the planet, giving the U.S. Space Force its first dedicated eyes on satellites and debris 22,000 miles above the Indo-Pacific.

The second sensor launched Aug. 10 aboard Japan's Quasi-Zenith Satellite 7 on an H-3 rocket from Tanegashima Space Center in southern Japan, the U.S. Space Systems Command confirmed in an announcement. The first sensor rode Japan's QZS-6 satellite into orbit on Feb. 2, 2025. Together they form a two-satellite network watching geosynchronous orbit, the crowded belt where communications and military satellites park.

The program, called the Quasi-Zenith Satellite System-Hosted Payload, is the first bilateral U.S.-Japan space effort focused on national security, according to the Space Force. It grew out of a December 2020 agreement between the Space Force and Japan's National Space Policy Secretariat.

Lincoln Laboratory engineers and Space Force teams worked alongside Japan's Mitsubishi Electric Corporation and the National Space Policy Secretariat for two years to integrate and test the sensors with the Japanese host spacecraft at facilities in Kamakura, Japan, according to the Space Force. The QZS-7 spacecraft weighs roughly 4.9 metric tons, SatNews reported.

The sensors are passive optical systems, meaning they watch without emitting radio signals, according to SOFX. That makes them harder for adversaries to detect. The QZS satellites follow high-inclination orbits that keep them persistently above the Indo-Pacific rather than fixed over the equator, giving sustained coverage of the orbital arc most relevant to U.S. military operations in the region.

Data from the Lexington-built sensors will feed into the U.S. Space Surveillance Network in near-real time. Mission Delta 2, headquartered at Peterson Space Force Base in Colorado, will operate the payloads once on-orbit checkout is complete.

"QZSS-HP is a key contributor to help us meet the threat of peer adversaries in space and build towards resilient capabilities to detect, understand, and maintain custody of objects in deep space," Col. Gina Peterson, deputy commander of Mission Delta 2, said in the announcement.

The timing matters. China has operated inspection satellites in geosynchronous orbit since 2018, maneuvering them close to other nations' spacecraft, and Russia deployed a suspected inspector satellite into the same belt by May 2026, according to SOFX.

MIT Lincoln Laboratory posted its own announcement confirming the lab's direct role in the program. The federally funded research center, situated off Wood Street in Lexington, has worked on space surveillance technology for decades.

No individual Lincoln Laboratory engineers were named in any of the public announcements. The payload is in its checkout phase, with no date given for when it will reach full operational status.

MIT Lincoln Laboratory has not announced any public event related to the program. Lexington's Patriots' Day commemoration returns in April 2027.