QZSS and Positioning Augmentation
QZSS can enhance GPS services in two ways: first, availability enhancement, whereby the availability of GPS signals is improved, second, performance enhancement whereby the accuracy and reliability of GPS derived navigation solutions is increased.
Because the GPS availability enhancement signals transmitted from Quasi-Zenith Satellites are compatible with modernized GPS signals, and hence interoperability is ensured, the QZSs will transmit the L1C/A signal, L1C signal, L2C signal and L5 signal. This minimizes changes to specifications and receiver designs.
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 QZS. 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-borne atomic clocks; a hydrogen maser and a 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 a Two-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.
Read more about this topic: Quasi-Zenith Satellite System
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