Asynchronous Laser Transponder Method for High-Precision Ranging and Clock Synchronization

Duplex laser communication system can achieve high-precision ranging and clock synchronization between terminals in spacecrafts with high data rate transmission. By measuring the transmission and arrival time of data frames during the detection of frame synchronization in laser communication, we resolved the range, time difference and frequency difference simultaneously. Furthermore, we designed a prototype of laser communication system with space and ground terminals separated by a free space to validate the ranging method for asynchronous transponders. For this duplex laser communication demonstration with data rate of 2.5 Gbps, we achieved very high precision with two-way ranging accuracy of 5.4 mm, frequency difference standard deviation of 3.4x10(-13), and time difference standard deviation of 2.9 ns. Such high-precision ranging accuracy would be valuable for orbit determination, and the precise measurement of time and frequency difference could be used for disciplining the satellite clock by the high-stability ground clock.