Method Of Common-view Time Transfer With Transfer Mode Based On Geostationary Communication Satellite

GPS Common-View (GPS CV) and Two-Way Satellite Time and Frequency Transfer(TWSTFT) are main methods of long base-line high precision time comparison. But theprecision of GPS pseudo-code common-view is low, the cost of TWSTFT is expensive, theirusing in common engineering which needs high precision time standard is limited.A method of common-view time transfer with transfer mode (TCV) via geostationary (GEO)telecommunication satellite was put forward. With this method we can transfer the standard timekept in a timing laboratory to users in a vast area covered by the GEO satellite’s signal. Timinglaboratory should be equipped with both transmitting and receiving devices; the users could onlybe equipped with the receiving device. Transmitting device in the laboratory generates andtransmits the pseudo-code ranging signal relative to its main clock to the GEO satellite. Then thesatellite will broadcast this signal to the earth. After receiving the signal, timing laboratory andusers measure the pseudo-range and calculate the relative clock bias between them. Thesignal-to-noise ratio and measurement precision were highly improved by using thewell-orientation paraboloidal antennas receiving the signal.The time standard of China, UTC (NTSC) is kept by National Time Service Center (NTSC),Chinese Academy of Science (CAS). C-band two way satellite time and frequency transfernetwork (TW(C)) of NTSC was used to proceed experiments. NTSC, Changchun Observatory(CHO) and Xinjiang Astronomical Observatory (XAO) were equipped with two TW(C) devices,the experiments were proceed two times with different devices. The pseudo-code ranging signalwas transmit by NTSC as the timing laboratory; the other stations only receive the signal as users.SATRE MODEM made by TimeTech Company in Germany is used in TW(C), the code rate is20MChips. ChinaSat-10was used in the experiment (110.5°E).The precise paraboloidal antenna coordinates of the timing laboratory and the user’s devicesand precise orbit of the GEO satellite should be known in advance in this method. The satelliteorbit is provided by Chinese Area Positioning System (CAPS), the accuracy of orbit is on thelevel of meter, it reaches the level of decimeter on the direction of satellite-station. The result ofTWSTFT was seen as the true value to validate the precision of TCV. Except Sagnac effect,ionospheric delay, tropospheric delay or other common error, Solid Earth tide was also taken outduring the data processing. The daily change of satellite-station distance is at the level ofdecimeter, considering it will reduce the standard deviation of the difference between the twomethods by0.11ns at most. The results of the comparison show that TCV is an efficacious long base-line high precision time comparison method; the difference between TCV and TW(C) wasbetter than0.5ns with3days’complete data, which significantly excels that of GPS pseudo-codecommon-view (3to5ns).