Time scales comparison using the signals of global navigation satellite systems
Radio engineering. Electronics. Telecommunication systems
Central Research Institute of Machine Building, 4, Pionerskaya st., Korolev, Moscow region, 141070, Russia
The necessity for high precision comparison of time scales arises in various fields of science and technology: from the transmission and distribution of energy and telecommunications systems to the time and frequency national laboratories. A unified state system of time can serve as an example of the latest category and in the frame of which the secondary national standards of time and frequency recreate the national time scale.
The main limitation of the current in-house technology for comparisons with the help of GNSS signals, which are used by the International Bureau of Weights and Measures in the formation of Coordinated Universal Time UTC, is the resulting estimates drift of time scales difference which is associated with the change of systematic delays in the spacecraft, as well as in the navigation receiver. This limitation can be overcome by the use of only phase measurements to estimate the difference of time scales.
If you are working only on the phase measurements a so-called problem of ambiguity resolution arises. For its successful solution apart from the high accuracy of the used models we have to know the difference between zenith tropospheric propagation delays of navigation signals with high accuracy. In the case when the distance between stations is less than ~ 50 km the delay is almost the same and it can be ignored, but otherwise the difference between the zenith tropospheric delays must be estimated a priori or with the rest parameters.
The aim of this work is to create a system of comparison for time scales using the measurements of GNSS which is based on Common View technique with difference evaluation of zenith tropospheric propagation delays of navigation signals.
The first step is ambiguity solution to the so-called wide-lane combination of measurements that can simplify further ambiguousness resolution for ion-free combination.
At the second step, at the same time we estimate the difference between the time scales of receivers and zenith tropospheric propagation delays of navigation signals for all available space vehicles with weights depending on the angle of elevation.
The results of comparisons are consistent with other technologies with a precision of 75 ps. Thus, this approach can serve as a basis for the construction of high precision comparison systems.
Keywords:GNSS, Common View, time transfer, integer ambiguity resolution
- Delporte J., Mercier F., Laurichesse D., Galy O. GPS Carrier-Phase Time Transfer Using Single-Difference Integer Ambiguity Resolution, International Journal of Navigation and Observation, Hindawi Publishing Corporation, 2008, no. 273785, doi:101155/2008/12737857
- Skakun I.O. Kosmonavtika i raketostroenie, 2012, no. 4(69), pp.60-69.