The Quasi-Zenith Satellite System (QZSS) is a regional satellite three- time transfer system in development and the satellite-based augmentation system for the Global Positioning System That Would Be receivable Within Japan . The first satellite “Michibiki” was lancé is 11 September 2010.  Full operational status Was expected by 2013.   In March 2013, Japan’s Cabinet Office annoncé the expansion of the Quasi-Zenith Satellite System from three satellites To four. The $ 526 million contract with Mitsubishi Electric for the construction of three satellites is slated for launch before the end of 2017.
( QSSS ), or Juntencho ( 準 天 頂 ) in Japanese , initiated by the Advanced Space Business Corporation (ASBC), including Mitsubishi Electric , Hitachi , And GNSS Technologies Inc. However, ASBC collapsed in 2007. The work was taken over by the Satellite Positioning Research and Application Center. SPAC is owned by four departments of the Japanese government: 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 . 
QZSS is targeted to provide highly accurate and stable positioning services in the Asia-Oceania regions, while maintaining compatibility with GPS. 
QZSS uses three satellites, each 120 ° apart, in highly inclined, slightly elliptical , geosynchronous orbits . 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||2009-12-26 12:00 UTC|
|Semimajor axis ( a )||42,164 km|
|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 ( M 0 )||305 ° (initial)|
|Central longitude of ground trace||135 ° E ± 5 °|
QZSS and positioning augmentation
The primary purpose of QZSS is to increase the availability of GPS in Japan’s urban 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 L1C GPS, 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 GPS satellite acquisition.
According to its original plan, QZSS was to carry two types of space-borne atomic 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. Aussi QZSS will be ble to use a Two-Way Satellite Time and Frequency Transfer (TWSTFT) scheme, qui will be employed to gain Some Fundamental knowledge of satellite atomic standard behavior in space as well as for other research practical purposes.
QZSS timekeeping and remote synchronization
QZSS satellites will carry a basic prototype of an experimental crystal clock synchronization system. During the fi rst half-year of the second 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 satellite navigation systems such as GPS, GLONASS or Galileo system. This concept is differentiated by the use of a synchronization framework with the lightweight on-board clocks, which act as transponders re-broadcasting the precise time on the ground. The QZSS is the only one in the world. Low satellite mass and low satellite manufacturing and launch costs are significant advantages of this system. This paper describes the quasi-Zenith Satellite System for the Quasi-Zenith Satellite System  and the Remote Synchronization Method for the Quasi-Zenith Satellite System. A novel satellite timekeeping system which does not require on-board atomic clocks . 
- Global Navigation Satellite System (GNSS)
- Multi-functional Satellite Augmentation System (MSAS)
- Jump up^ “Launch Result of the First Quasi-Zenith Satellite ‘MICHIBIKI’ by H-IIA Launch Vehicle No. 18” . 2010-09-11 . Retrieved 2011-12-12 .
- Jump up^ “QZSS in 2010” . Article Magazine . Asian Surveying and Mapping. 2009-05-07 . Retrieved 2009-05-07 . [ Dead link ]
- Jump up^ “GNSS All Over the World” . The System . GPS World Online. 2007-11-01. Archived from the original on August 23, 2011 . Retrieved 2011-12-12 .
- Jump up^ http://www.spaceflightnow.com/news/n1304/04qzss/Japan to build fleet of satellite navigation 2013-04-04 Retrieved 2013-04-05
- Jump up^ “Service Overview – What is the QZSS?” . Cabinet Office, Government of Japan . Retrieved 2016-01-20 .
- Jump up^ “Service Status of QZSS” (PDF) . 2008-12-12. Archived from the original (PDF) on July 25, 2011 . Retrieved 2009-05-07 .
- Jump up^ “[Movie] Quasi-Zenith Satellite System” QZSS “” . Quasi-Zenith Satellite System (QZSS) . Retrieved 19 July 2017 .
- Jump up^ Japan Aerospace Exploration Agency (2016-07-14), Interface Specifications for QZSS , version 1.7, pp. 7-8
- Jump up^ Fabrizio Tappero (April 2008), Remote Synchronization Method for the Quasi-Zenith Satellite System (PhD thesis) , retrieved 2013-08-10 [ dead link ]
- Jump up^ Fabrizio Tappero (2009-05-24). Remote Synchronization Method for the Quasi-Zenith Satellite System . VDM Verlag. ISBN 978-3-639-16004-8 .