Accession Number : ADP009100

Title :   Two-Way Satellite Time Transfer: Overview and Recent Developments,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GREENBELT MD GODDARD SPACE FLIG HT CENTER

Personal Author(s) : De Jong, Gerrit

Report Date : 02 DEC 1993

Pagination or Media Count : 17

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 Radiocommunication Sector (formerly CCIR), a very intense discussion has taken place about what procedures should be recommended for TWS TFT 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 Group on TWSTFT addressed this in October 1993. The outcome of the discussions and the prospect for future developments will be presented.

Descriptors :   *RADIO LINKS, *TIME STANDARDS, CALIBRATION, DELAY, FORMATS, GERMANY, INTERNATIONAL, MODEMS, TEST AND EVALUATION, TIME, TIME SIGNALS, PSEUDO NOISE SYSTEMS, COMMUNICATION SATELLITES, INFORMATION EXCHANGE, GROUND STATIONS, NETHERLANDS.

Subject Categories : Test Facilities, Equipment and Methods
      Radio Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE