Japan kind-of completes its sovereign satnav constellation

Japan has successfully launched the final satellite for its current generation of sovereign satellite navigation system. The satellite, named "Michibiki No. 7" or QZS-7, reached orbit on Tuesday morning aboard a H3 rocket. The H3 is Japan Aerospace Exploration Agency's (JAXA) latest medium-range launcher, which has flown nine missions, two of which ended in failure.

Japan aims to develop its own satellite positioning system because GPS signals may not always reach certain parts of the country, particularly mountainous regions and densely populated areas. To ensure universal coverage and improved accuracy, Japan created the Quasi-Zenith Satellite System (QZSS). The QZSS complements GPS by keeping a positioning satellite almost always above Japan, providing excellent local service.

The QZSS satellites utilize an inclined geostationary orbit, forming a figure-eight pattern. This orbit allows the satellites to move more slowly when above the Northern Hemisphere, spending around 13 hours above the equator and remaining visible from Japan for extended periods. The first QZSS satellite was launched in 2010, and four production models were deployed between 2017 and 2021.

Japan later decided to expand the system to seven orbiters, with QZS-6 launched in February 2025 following the unsuccessful launch of QZS-5 in December 2025.

Although Japan now has almost all the satellite navigation coverage it desires, plans call for three more satellites to be launched in the 2030s. However, there are no plans for a replacement for QZS-5 at this time. For now, Japan has achieved most of its satnav coverage goals and gained increased confidence in the H3 rocket's reliability as a space transportation system.