2024 DIRECTIONS BY Motohisa KISHIMOTO, SENIOR COORDINATOR, QZSS STRATEGY OFFICE, NATIONAL SPACE POLICY SECRETARIAT, CABINET OFFICE, GOVERNMENT OF JAPAN The Status of QZSS Space Policy and QZSS Plan Japan’s Cabinet Office (CAO) is currently developing the Quasi-Zenith Satellite System (QZSS) seven-satellite constellation (7SV-const.) Japan’s cabinet revised our new basic space policy plan on June 13, 2023. It states that the number of QZSS satellites should be increased from seven to 11 to improve stability and reliability as one of the social infrastructures by securing backup function for coming full-scale use and to reduce the dilution of precision (DOP). On June 12, 2024, the National Space Policy Secretariat revised the action plan for the satellite positioning system for the first time in three years. According to this plan, the completion of the QZSS 11-satellite vehicle constellation is anticipated by the late 2030s. Brief History of QZSS Since 2006, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Aerospace Exploration Agency (JAXA), the Ministry of Internal Affairs and Communications (MIC), the Ministry of Economy, Trade and Industry (METI) and the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) have collaborated to develop the world’s first centimeter-level positioning satellite. The first QZS satellite was launched in September 2010, for what was then envisioned as a four-satellite regional satellite navigation system, also known as MICHIBIKI. In September 2011, the Cabinet approved a plan to build the four-satellite constellation (4SV-const.) in the late 2010s, with the goal of building a 7SV-const. in the future. The budget was approved in JFY2012 to promote this as a national project. In 2017, QZS-2, 3 and 4 were successfully launched and a 4SV-const. was established. On Nov. 1, 2018, QZSS officially began service. On Oct. 26, 2021, the successor to the first MICHIBIKI was launched. Development is underway to launch three additional satellites for the 7SV-const. sequentially from JFY2023 to JFY2024, depending on the development status of the H3 launch vehicle. To improve resilience for more stable positioning and improved DOP, CAO has started a study to transition from a 7SV-const. to an 11SV-const. ( See Figures 1 and 2 ) Service Overview The 4SV-const. provides GPS Complementary Service (PNT service); GNSS Augmentation Service, i.e. Sub-meter Level Augmentation Service (SLAS), Centimeter Level Augmentation Service (CLAS), MADOCA-PPP and satellite-based augmentation service (SBAS), as well as a messaging service. The QZSS constellation consists of a geostationary orbit (GEO) satellite, QZS-3 and three QZO satellites. QZSS’s performance of the positioning, navigation and timing (PNT) service and signal-in-space user range error (SIS-URE) was much better than specified. Evaluation results are shown in Table 1 . All figures provided by the author FIGURE 1 System expansion of QZSS. 36 GPS WORLD WWW.GPSWORLD.COM | DECEMBER 2024
GPS World December 2024: Page 36
