Abstract
The remote synchronization system for the onboard crystal oscillator (RESSOX) is a remote control method that permits synchronization between a ground station atomic clock and Japanese quasi-zenith satellite system (QZSS) crystal oscillators. To realize the RESSOX of the QZSS, the utilization of navigation signals of QZSS for feedback control is an important issue. Since QZSS transmits seven navigation signals (L1C/A, L1CP, L1CD, L2CM, L2CL, L5Q, and L5I), all combinations of these signals should be evaluated. First, the RESSOX algorithm will be introduced. Next, experimental performance will be demonstrated. If only a single signal is available, ionospheric delay should be input from external measurements. If multiple frequency signals are available, any combination, except for L2 and L5, gives good performance with synchronization error being within two nanoseconds that of RESSOX. The combination of L1CD and L5Q gives the best synchronization performance (synchronization error within 1.14 ns). Finally, in the discussion, comparisons of long-duration performance, computer simulation, and sampling number used in feedback control are considered. Although experimental results do not correspond to the simulation results, the tendencies are similar. For the overlapping Allan deviation of long duration, the stability of 1.23×10−14 at 100,160 s is obtained.
Highlights
The Japanese Quasi-Zenith Satellite System (QZSS) is a three-satellite navigation/positioning system conceived to improve the positioning performance of the presently available global positioning system (GPS) for civilians in urban areas where high-rise buildings exist and where mountains reduce the number of visible GPS satellites in Japan [1]
The proposed Japanese QZSS has the following properties regarding its timekeeping system (TKS): (1) it is possible to control the system over a 24-hour period as long as a good ground site is available, such as Okinawa, Japan, (2) a high-stability crystal oscillator is superior to an atomic clock in terms of short-term frequency stability [2], (3) ground stations are continuously operational, and (4) QZSS employs a maximum of three satellites, which is not too many to monitor from the ground
Three (L1/L2/L5-band navigation signals) delay files include the times at which the L1/L2/L5-band navigation signals are received at the ground station, and the model delays of the L1/L2/L5-band navigation signals
Summary
The Japanese Quasi-Zenith Satellite System (QZSS) is a three-satellite navigation/positioning system conceived to improve the positioning performance (satellite availability and position accuracy) of the presently available global positioning system (GPS) for civilians in urban areas where high-rise buildings exist and where mountains reduce the number of visible GPS satellites in Japan [1]. The proposed Japanese QZSS has the following properties regarding its timekeeping system (TKS): (1) it is possible to control the system over a 24-hour period as long as a good ground site is available, such as Okinawa, Japan, (2) a high-stability crystal oscillator is superior to an atomic clock in terms of short-term frequency stability [2], (3) ground stations are continuously operational, and (4) QZSS employs a maximum of three satellites, which is not too many to monitor from the ground. The remote synchronization system for an onboard crystal oscillator (RESSOX) has been planned by the National Institute of Advanced Industrial Science and Technology (AIST) since 2003 [3]. RESSOX is a remote control method that permits synchronization between a ground station
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