Description

This book presents a novel satellite timekeeping system which does not require on-board atomic clocks as used by existing navigation satellite systems such as GPS, GLONASS or the GALILEO system. 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 Quasi-Zenith Satellite System, QZSS. Low satellite mass and low satellite manufacturing and launch cost are significant advantages of this novel system. Two possible implementations of the time synchronization network for QZSS are presented. Additionally, the problem of satellite communication interruption is analysed and a solution is presented. Finally a positioning and timing quality analysis, aimed to provide understanding of the actual timing quality requirements for QZSS, is presented.