1、QUESTION ITU-R 250/7 Application and improvement of two-way satellite time and frequency transfer (TWSTFT) (2009) The ITU Radiocommunication Assembly, considering a) that the two-way exchange of timing signals through radiocommunication satellites has proven to yield excellent results in terms of ac
2、curacy and stability; b) that the experimental results on the short-term time stability are consistent with theoretical results; c) that long-term time stability studies are now being made; d) that systematic variations in the delays of the transmitting and receiving elements for this technique need
3、 to be better understood and documented; e) that telecommunication and timing authorities are using TWSTFT in operational systems to synchronize various elements of their services, decides that the following Questions should be studied 1 What is the dependence of the performance levels that can be a
4、chieved using TWSTFT with respect to: the time transfer accuracy; and the frequency transfer accuracy; the operational parameters: IF modulation characteristics; RF carrier frequency; available frequency bandwidth on the transponder? 2 What are the causes and cures for systematic delay variations th
5、at may be perturbing this technique? 3 What are the optimum methods to monitor and calibrate the propagation delays? 4 What are the best ways to ensure efficient use of available satellite transponder capacity? 5 How can the optimum data evaluation and reporting strategy be provided? further decides 1 that the results of the above studies should be used to update the existing Recommendation ITU-R TF.1153 and to be included in one or more new Recommendations; 2 that the above studies should be completed by 2012. Category: S2
