Quasi-Zenith Satellite System
Navigation satellites
 | |
| Country/ies of origin | Japan |
|---|---|
| Operator(s) | Quasi-Zenith Satellite System Services Inc. / Cabinet Office |
| Type | Civilian |
| Status | Operational |
| Coverage | Regional |
| Accuracy | PNT <10 m (public) SLAS <1 m (public) CLAS <10 cm (public) |
| Constellation size | |
| Nominal satellites | 7 |
| Current usable satellites | 4 |
| First launch | 11 September 2010 |
| Last launch | 26 October 2021 |
| Total launches | 5 |
| Orbital characteristics | |
| Regime(s) | 3x GSO |
| Other details | |
| Cost | JPY 170 billion |
| Website | qzss |
The Quasi-Zenith Satellite System (QZSS), also known as Michibiki (みちびき), is a four-satellite regional satellite navigation system and a satellite-based augmentation system developed by the Japanese government to enhance the United States-operated Global Positioning System (GPS) in the Asia-Oceania regions, with a focus on Japan.[1] The goal of QZSS is to provide highly precise and stable positioning services in the Asia-Oceania region, compatible with GPS.[2] Four-satellite QZSS services were available on a trial basis as of 12 January 2018,[3] and officially started on 1 November 2018.[4] A satellite navigation system independent of GPS is planned for 2023 with seven satellites.[5][6] In May 2023 it was announced that the system would expand to eleven satellites.[7]
History
In 2002, the Japanese government authorized the development of QZSS, as a three-satellite regional time transfer system and a satellite-based augmentation system for the United States operated Global Positioning System (GPS) to be receivable within Japan. A contract was awarded to Advanced Space Business Corporation (ASBC), that began concept development work, and Mitsubishi Electric, Hitachi, and GNSS Technologies Inc. However, ASBC collapsed in 2007, and the work was taken over by the Satellite Positioning Research and Application Center (SPAC), which is owned by four Japanese government departments: the Ministry of Education, Culture, Sports, Science and Technology, the Ministry of Internal Affairs and Communications, the Ministry of Economy, Trade and Industry, and the Ministry of Land, Infrastructure, Transport and Tourism.[8]
The first satellite "Michibiki" was launched on 11 September 2010.[9] Full operational status was expected by 2013.[10][11] In March 2013, Japan's Cabinet Office announced the expansion of QZSS from three satellites to four. The US$526 million contract with Mitsubishi Electric for the construction of three satellites was scheduled for launch before the end of 2017.[12] The third satellite was launched into orbit on 19 August 2017,[13] and the fourth was launched on 10 October 2017.[14] The basic four-satellite system was announced as operational on 1 November 2018.[4]
Orbit
QZSS uses one geostationary satellite and three satellites in Tundra-type highly inclined, slightly elliptical, geosynchronous orbits. Each orbit is 120° apart from the other two. Because of this inclination, they are not geostationary; they do not remain in the same place in the sky. Instead, their ground traces are asymmetrical figure-8 patterns (analemmas), designed to ensure that one is almost directly overhead (elevation 60° or more) over Japan at all times.
The nominal orbital elements are:
| Epoch | 26 December 2009, 12:00 UTC |
| Semimajor axis (a) | 42,164 km (26,199 mi) |
| Eccentricity (e) | 0.075 ± 0.015 |
| Inclination (i) | 43° ± 4° |
| Right ascension of the ascending node (Ω) | 195° (initial) |
| Argument of perigee (ω) | 270° ± 2° |
| Mean anomaly (M0) | 305° (initial) |
| Central longitude of ground trace | 135° E ± 5° |
Planned seven satellites constellation consists of four Quasi-Zenith Orbit (QZO) satellites, two geostationary (GEO) satellites, and one quasi-geostationary (slight incline and eccentricity) orbit satellite.[16]
Satellites
| Name | Launch date | Status | Notes |
|---|---|---|---|
| QZS-1 (Michibiki-1) | 11 September 2010 | Replaced by QZS-1R | Experimental. Lacks MADOCA and PTV signals. Acting as spare since March 2022.[17] Decommissioned on 15 September 2023.[18] |
| QZS-2 (Michibiki-2) | 1 June 2017 | Operational | Improved solar panels and increased fuel |
| QZS-3 (Michibiki-3) | 19 August 2017 | Operational | Heavier design with additional S-band antenna on geostationary orbit at 127° E[16] |
| QZS-4 (Michibiki-4) | 10 October 2017 | Operational | Improved solar panels and increased fuel |
| QZS-1R (Michibiki-1R) | 26 October 2021 | Operational | Replacement for QZS-1.[19] |
| QZS-5 | JFY2024 | Planned | [20] |
| QZS-6 | JFY2025 | Planned | Geostationary at 90.5° E[16][20][21] |
| QZS-7 | JFY2025 | Planned | Quasi-geostationary around 190° E[16][20][21] |
