Satellite orbit determination and time transfer based on TWSTFT

Abstract

Two-way satellite time and frequency transfer (TWSTFT) is one of the most precise and accurate long-distance time transfer techniques nowadays. A C band multi-station satellite tracking system is developed based on TWSTFT in China. This system can not only measure the distance between a satellite with transponders and earth stations, but also realize the time synchronization between all earth stations. The satellite orbit can be determined by the distances. Five earth stations have been constructed in China. The master station is placed at the National Time Service Center (NTSC) in Lintong. There are a very small antenna terminal (VSAT) of 3.7 meters, up/down converters, a modem and an atomic clock in each station. The up and down link frequencies are 6GHz and 4GHz. The spread spectrum signal generated by the modem is 20MHz chip rate. The transmitter power is less than 1 W. The results show that the accuracy of ranging, orbit determination and time synchronization between all earth stations is about 1cm, 10cm and 0.1ns respectively.