Two-Way Satellite Time Transfer: Overview and Recent Developments

Gerrit de Jong

Abstract:	The experiment using small earth stations for transatlantic two-way satellite time transfer between the USA (USNO, Washington, DC) and Germany (DFVLR), Oberfaffenhofen) has had its 10th anniversary this year. Pseudo Random Noise coded time signals were phase modulated and demodulated at each stations using a modem developed by Professor Hartl and his staff. Recently, during the last two weeks of August 1993, six European time laboratories have used the INTELSAT 307E satellite for line-up tests and preliminary time transfer sessions using the same type of MITREX modem. This opportunity was given by INTELSAT, thanks to the help of Dr. Veenstra. The need for a uniform format for the exchange of data was felt heavily after these sessions. This problem was foreseen and addressed in international working parties. During April 1993 in Task Group 712 of the ITU Radiocommuncation Sector (formerly CCIR), a very intense discussion has taken place about what procedures should be recommended for TWSTFT and what items the header and data lines of the resulting data fields should contain. A difficulty is that two different methods of calibration of the earth station delays exist which results different sets of delay data to be exchanged. Further study and discussions are necessary. Also, a meeting of the CCDS Working Goup on TWSTFT addressed this in October 1993. The outcome of the discussions and the prospect for future developments will be presented.
Published in:	Proceedings of the 25th Annual Precise Time and Time Interval Systems and Applications Meeting November 29 - 2, 1993 Ritz-Carlton Hotel Marina Del Rey, California
Pages:	101 - 118
Cite this article:	de Jong, Gerrit, "Two-Way Satellite Time Transfer: Overview and Recent Developments," Proceedings of the 25th Annual Precise Time and Time Interval Systems and Applications Meeting, Marina Del Rey, California, November 1993, pp. 101-118.
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