QZSS (Quasi-Zenith Satellite System), Japan

QZSS is a four-satellite system that provides regional communication services and positioning information for the mobile environment. The focus of this system is for the Japan region, but it will provide service to the Asia-Oceania region.

QZSS provides limited accuracy in standalone mode, so it is viewed as a GPS augmentation service. The QZSS satellites use the same frequencies as GPS and have clocks that are synchronised with GPS time. This allows the QZSS satellites to be used as if they were additional GPS satellites. QZSS satellites also broadcast a signal compatible with Satellite-Based Augmentation Systems (SBAS) and a high-precision signal at L6. See Chapter 5 to learn more about SBAS.

Three of the QZSS satellites are in a periodic Quasi-Zenith Orbit (QSO). These orbits will allow the satellites to “dwell” over Japan for more than 12 hours a day, at an elevation above 70° (meaning they appear almost overhead most of the time).

Japan intends to expand the QZSS system to a seven-satellite system by 2024.

Chapter 3: GNSS constellations