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Quasi-Zenith Satellite System

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TheQuasi-Zenith Satellite System(QZSS), also known asMichibiki(みちびき),is a four-satelliteregional satellite navigation systemand asatellite-based augmentation systemdeveloped by theJapanese governmentto enhance the United States-operatedGlobal Positioning System(GPS) in theAsia-Oceaniaregions, 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]

Quasi-Zenith Satellite System

Country/ies of originJapan
Operator(s)Quasi-Zenith Satellite System Services Inc. /Cabinet Office
TypeCivilian
StatusOperational
CoverageRegional
AccuracyPNT<10 m (public)
SLAS<1 m (public)
CLAS<10 cm (public)
Constellation size
Nominalsatellites7
Current usablesatellites4
First launch11 September 2010
Last launch26 October 2021
Total launches5
Orbital characteristics
Regime(s)3xGSO
Other details
CostJPY170 billion
Websiteqzss.go.jp/en/
Quasi-Zenithsatellite orbit
QZSS animation, the "Quasi-Zenith/tundra orbit"plot is clearly visible.

History

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In 2002, the Japanese government authorized the development of QZSS, as a three-satellite regionaltime transfersystem and asatellite-based augmentation systemfor the United States operatedGlobal Positioning System(GPS) to be receivable within Japan. A contract was awarded to Advanced Space Business Corporation (ASBC), that began concept development work, andMitsubishi 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: theMinistry of Education, Culture, Sports, Science and Technology,theMinistry of Internal Affairs and Communications,theMinistry of Economy, Trade and Industry,and theMinistry 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]

As of 2024,an eleven-satellite configuration is under consideration, which would provide redundancy for single-satellite failure.[15]

Orbit

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QZSS uses onegeostationary satelliteand three satellites inTundra-type highly inclined, slightlyelliptical,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 nominalorbital elementsare:

QZSS satellite Keplerian elements (nominal)[16]
Epoch 26 December 2009, 12:00UTC
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.[17]

Satellites

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Name Launch date Launch Vehicle Status Notes
QZS-1 (Michibiki-1) 11 September 2010 H-IIA202 Replaced by QZS-1R Experimental. Lacks MADOCA and PTV signals. Acting as spare since March 2022.[18]Decommissioned on 15 September 2023.[19]
QZS-2 (Michibiki-2) 1 June 2017 H-IIA 202 Operational Improved solar panels and increased fuel
QZS-3 (Michibiki-3) 19 August 2017 H-IIA 204 Operational Heavier design with additional S-band antenna ongeostationary orbitat 127° E[17]
QZS-4 (Michibiki-4) 10 October 2017 H-IIA 202 Operational Improved solar panels and increased fuel
QZS-1R(Michibiki-1R) 26 October 2021 H-IIA 202 Operational Replacement for QZS-1.[20]
QZS-5 (Michibiki-5) JFY2024 H3-22S Planned [21]
QZS-6 (Michibiki-6) JFY2025 H3 Planned Geostationary at 90.5° E[17][21][22]
QZS-7 (Michibiki-7) JFY2025 H3 Planned Quasi-geostationary around 190° E[17][21][22]
Animation of QZSS
Around the Earth - Oblique view
Around the Earth - Polar view
Earth fixed frame- Equatorial view, front
Earth fixed frame- Equatorial view, side
Earth·QZS-1·QZS-2·QZS-3·QZS-4

QZSS and positioning augmentation

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The primary purpose of QZSS is to increase the availability of GPS in Japan's numerousurban canyons,where only satellites at very high elevation can be seen. A secondary function is performance enhancement, increasing the accuracy and reliability of GPS derived navigation solutions. The Quasi-Zenith Satellites transmit signals compatible with the GPS L1C/A signal, as well as the modernized GPS L1C, L2C signal and L5 signals. This minimizes changes to existing GPS receivers. Compared to standalone GPS, the combined system GPS plus QZSS delivers improved positioning performance via ranging correction data provided through the transmission of submeter-class performance enhancement signals L1-SAIF and LEX from QZSS. It also improves reliability by means of failure monitoring and system health data notifications. QZSS also provides other support data to users to improve GPS satellite acquisition. According to its original plan, QZSS was to carry two types of space-borneatomic clocks;a hydrogen maser and a rubidium (Rb) atomic clock. The development of a passive hydrogen maser for QZSS was abandoned in 2006. The positioning signal will be generated by a Rb clock and an architecture similar to the GPS timekeeping system will be employed. QZSS will also be able to use aTwo-Way Satellite Time and Frequency Transfer(TWSTFT) scheme, which will be employed to gain some fundamental knowledge of satellite atomic standard behavior in space as well as for other research purposes.

Signals and services

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The QZSS provides the following classes of public service:[23]

  • The PNT (Positioning, Navigation and Timing) service complements the signals used by the GPS system, essentially acting as extra satellites. The QZSS satellites sync their clocks with GPS satellites. The service broadcasts at frequency bands L1C/A, L1C, L2C, and L5C, the same as GPS.[24]
  • The SLAS (Sub-meter Level Augmentation) service provides a form ofGNSS augmentationfor GPS interoperable with other GPS-SBAS systems. The principle of operation is similar to that of, e.g.Wide Area Augmentation System.It transmits on L1.[24]
  • The CLAS (Centimeter Level Augmentation) service provides high-precision positioning compatible with the higher-precision E6 service ofGalileo.The band is referred to as L6 or LEX, for "experimental".[24]
  • The MADOCA-PPP (Multi-GNSS Advanced Orbit and Clock Augmentation –Precise Point Positioning) service is a L6 augmentation service independent from CLAS.
  • The DC Report (Satellite Report for Disaster and Crisis Management) service broadcasts on L1S and provides information on floods and earthquakes.

The other classes of service are not publicly available:

  • The PTV (Positioning Technology Verification) service broadcasts on L5S. The documentation only describes a "null" message type.
  • The Q-ANPI (QZSS Safety Confirmation Service) is an authorized short message service.

QZSS timekeeping and remote synchronization

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Although the first generation QZSS timekeeping system (TKS) will be based on the Rb clock, the first QZSS satellites will carry a basic prototype of an experimental crystal clock synchronization system. During the first half of the two year in-orbit test phase, preliminary tests will investigate the feasibility of the atomic clock-less technology which might be employed in the second generation QZSS.

The mentioned QZSS TKS technology is a novel satellite timekeeping system which does not require on-board atomic clocks as used by existing navigation satellite systems such asBeiDou,Galileo,Global Positioning System(GPS),GLONASSorNavICsystem. This concept is differentiated by the employment of a synchronization framework combined with lightweight steerable on-board clocks which act as transponders re-broadcasting the precise time remotely provided by the time synchronization network located on the ground. This allows the system to operate optimally when satellites are in direct contact with the ground station, making it suitable for a system like the Japanese QZSS. Low satellite mass and low satellite manufacturing and launch cost are significant advantages of this system. An outline of this concept as well as two possible implementations of the time synchronization network for QZSS were studied and published inRemote Synchronization Method for the Quasi-Zenith Satellite System[25]andRemote Synchronization Method for the Quasi-Zenith Satellite System: study of a novel satellite timekeeping system which does not require on-board atomic clocks.[26][non-primary source needed]

Comparison ofTundra orbit,QZSS orbit andMolniya orbit- equatorial view
Front view
Side view
Earth fixed frame,Front view
Earth fixed frame,Side view
Tundra orbit·QZSS orbit·Molniya orbit·Earth

See also

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References

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  1. ^"Quasi-Zenith Satellite Orbit (QZO)".Archivedfrom the original on 9 March 2018.Retrieved10 March2018.
  2. ^"[Movie] Quasi-Zenith Satellite System" QZSS "".Quasi-Zenith Satellite System(QZSS).Archivedfrom the original on 15 July 2017.Retrieved19 July2017.
  3. ^"Start of QZS-4 Trial Service".Quasi-Zenith Satellite System (QZSS).Archivedfrom the original on 10 August 2018.Retrieved2 May2018.
  4. ^ab"Japan's QZSS service now officially available".26 November 2018.Retrieved11 January2019.
  5. ^"Japan mulls seven-satellite QZSS system as a GPS backup".SpaceNews. 15 May 2017.Retrieved10 August2019.
  6. ^Kriening, Torsten (23 January 2019)."Japan Prepares for GPS Failure with Quasi-Zenith Satellites".SpaceWatch.Global.Retrieved10 August2019.
  7. ^Kawahara, Satoshi (8 May 2023)."Japan plans expansion of homegrown GPS network to 11 satellites".Nikkei Asia.
  8. ^"Service Status of QZSS"(PDF).12 December 2008. Archived fromthe original(PDF)on 25 July 2011.Retrieved7 May2009.
  9. ^"Launch Result of the First Quasi-Zenith Satellite 'MICHIBIKI' by H-IIA Launch Vehicle No. 18".JAXA. 11 September 2010.Archivedfrom the original on 20 March 2012.Retrieved12 December2011.
  10. ^"QZSS in 2010".Asian Surveying and Mapping. 7 May 2009.Retrieved7 May2009.[dead link‍]
  11. ^"GNSS All Over the World".GPS World Online. 1 November 2007. Archived fromthe originalon 23 August 2011.Retrieved12 December2011.
  12. ^http://www.spaceflightnow.com/news/n1304/04qzss/Japan to build fleet of navigation satellitesat theWayback Machine(archived 2013-04-11)
  13. ^"Launch Schedule".Archivedfrom the original on 9 August 2018.Retrieved20 August2017.
  14. ^"Launch Schedule".Spaceflight Now.Archivedfrom the original on 16 August 2018.Retrieved20 August2017.
  15. ^National Space Policy Secretariat (12 June 2024).Vệ tinh trắc vị に quan する thủ tổ phương châm 2024(PDF)(in Japanese). Cabinet Office, Government of Japan.
  16. ^Interface Specifications for QZSS,version 1.7, JAXA, 14 July 2016, pp. 7–8, archived fromthe originalon 6 April 2013
  17. ^abcdChuẩn thiên đỉnh vệ tinh の７ cơ thể chế に hướng けた khai phát について(PDF)(in Japanese). Cabinet Office, Government of Japan. 23 January 2019.Retrieved4 March2024.
  18. ^NAQU 2022059, accessible via"NAQU Message".Quasi-Zenith Satellite System (QZSS).
  19. ^"Suspension of QZS-1 all operations".Quasi-Zenith Satellite System.15 September 2023.Retrieved16 September2023.
  20. ^"Vũ trụ cơ bổn kế họa công trình biểu ( lệnh hòa 2 niên 6 nguyệt 29 nhật )"[Space Plan Schedule (2020 June 29)](PDF)(in Japanese). Cabinet Office (Japan). 29 June 2020. p. 54.Retrieved6 December2020.
  21. ^abcVũ trụ cơ bổn kế họa ⼯ trình biểu ( lệnh hòa ５ niên độ cải đính )(PDF)(in Japanese). Cabinet Office, Government of Japan. 22 December 2023.Retrieved4 March2024.
  22. ^abRyan, Dorothy (3 December 2020)."Lincoln Laboratory is designing a payload to integrate on Japanese satellites".MIT.Retrieved6 December2020.The laboratory is working with the Japanese National Space Policy Secretariat and Mitsubishi Electric Company to integrate state-of-the-art sensors on the newest satellites in the QZSS constellation, QZS-6 and QZS-7, which are scheduled for launch in 2023 and 2024, respectively.
  23. ^Quasi-Zenith Satellite System Performance Standard PS-QZSS-003 (Mar.17, 2022)
  24. ^abcJeffrey, Charles (2010).An introduction to GNSS: GPS, GLONASS, Galileo and other Global Navigation Satellite Systems(1st ed.). Calgary: NovAtel.ISBN978-0-9813754-0-3.OCLC1036065024.
  25. ^Fabrizio Tappero (April 2008)."Remote Synchronization Method for the Quasi-Zenith Satellite System"(PhD thesis). Archived fromthe originalon 7 March 2011.Retrieved10 August2013.
  26. ^Fabrizio Tappero (24 May 2009).Remote Synchronization Method for the Quasi-Zenith Satellite System: study of a novel satellite timekeeping system which does not require on-board atomic clocks.VDM Verlag.ISBN978-3-639-16004-8.
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