Research On Common-view Time Service With Transfer Mode Via GEO Satellite

A new method of Common-view time transfer with transfer mode(TCV forabbreviation) via GEO telecommunication satellite is put forward, with which wecan transfer the standard time kept in a time keeping laboratory, such as UTC(NTSC), to many users in the local area covered by the GEO satellite’s signal. Thetime keeping laboratory is equipped with transmitting device and receiving device,and their external reference is from the main clock of the lab. The pseudo-coderanging signal is generated by the transmitting device in the lab, and is transmitted tothe GEO satellite via a paraboloidal antenna, and then is broadcasted to the earth bythe satellite. The pseudo-range from transmitter to GEO satellite and to the receivingdevice is measured in the lab. And at the same time the pseudo-range fromtransmitter to GEO satellite and to the user time receiver is also measured. Byprocessing the pseudo-range measured by the user time receiver and that measuredin the lab with paraboloidal antenna in common-view method, we can get the timedifference between the user receiver clock and the main clock in the lab, carrying outthe common-view time transfer with transfer mode (TCV). The precise coordinatesof paraboloidal antenna in NTSC and the user time receiver, as well as precise orbitof the GEO satellite should be known in advance in this method.Chinese national standard time, UTC (NTSC) is kept in National Time ServiceCenter (NTSC), Chinese Academy of Science. Based on the device of Two-WaySatellite Time and Frequency Transfer with C-band (TW(C) for abbreviation) inNTSC and Xinjiang Astronomical Observatory (XAO), we did TCV experiment.Both the transmitting and receiving units of the TW(C) device in NTSC are used,and only the receiving unit of the TW(C) device in XAO is used as a user timereceiver. The main clock of UTC (NTSC) is a HP5071A Cs atomic clock, and anOSA5585PRS Cs atomic clock is equipped in XAO. SATRE MODEM made byTimetech Company in Germany is used in our TW(C) devices, and the code rate is20MChips. The GEO satellite used in the experiment is Sinosat-1telecommunicationsatellite (110.5°E).For the data processing in TCV method, the precise coordinates of thetransmitting station and the receiving station are known in advance, satellite orbit isprovided by Chinese Area Positioning System (CAPS) of Chinese Academy of Sciences, orbit precision is on the level of meter. And the system errors includingSagnac effect, ionosphere delay, troposphere delay etc, are taken out during the dataprocessing, but the device delay is not deducted. We compare the results of TCV andTW(C), and it shows that ignoring the device delay (almost constant), the RMS ofthe difference between TCV and TW(C) is about1ns in5days, and such result isvery better than that in GPS Common-view time transfer with code.