What is QZSS?
The Quasi-Zenith Satellite System (QZSS) is a GPS augmentation system that aims to greatly improve GNSS accuracy over Japan and the rest of East Asia. The first satellite in the system, dubbed Michibiki, was successfully launched from the Tanegashima space centre on 11th September and reached its quasi-zenith orbit on 27th September 2010.
QZSS aims to enhance GPS services both by improving the availability of GPS signals and by performance enhancement to increase the accuracy and reliability of GPS navigation. The enhancement signals transmitted from Quasi-Zenith Satellites will be compatible with both existing and modernised GPS signals, minimising the need for changes to specifications and receiver designs.
The combined GPS/QZSS solution will deliver improved positioning performance using ranging correction data transmitted as dual sub-metre-class performance enhancement signals. It will also improve reliability using failure monitoring and system health data notifications. QZSS will also provide other support data that will improve GPS satellite acquisition.
Interestingly, the QZSS satellites do not carry their own high-accuracy atomic clocks. Rather they feature a synchronisation framework combined with lightweight steerable onboard clocks that act as transponders rebroadcasting the precise time from a synchronisation network located on the ground.
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