Enhancing the Performance of the Egyptian Time Scale (UTC(NIS))

Abstract

Improving the frequency stability of the Atomic Time Scale (TA(K)), and hence that of the national time scale (UTC(K)), is a main target for all timekeepers. Coordinated Universal Time (UTC) is the international reference time, and K is the abbreviation given by the Bureau International des Poids et Measures (BIPM) to the timekeeping laboratory. TA(NIS) is the atomic Time Scale (TS) of the National Institute of Standards (NIS), and UTC(NIS) is the national TS of Egypt. The stability of TA(K) can be improved by either increasing the number of atomic clocks in the ensemble or by adding clocks of higher stability. In both cases, a large financial budget is needed which may be unaffordable by some developing economics.

In this thesis, firstly we propose a new method for improving the stability of atomic TS by a factor approaching 50 % with zero expenses by replacing the real clocks in the ensemble by Virtual Clocks (VCs). The VCs are obtained by Downscaling (DS) the frequency offset of the real clocks. The DS process improves the frequency stability of the clocks and hence that of the resultant average TS. Since the down-scaled clocks are correlated to the original ones, then they replace the real clocks and not added to the ensemble. The performance of the proposed method is verified by applying it on the daily clocks comparison data of the Observatory of Paris (OP) published on the time department server of the BIPM. The performance of the proposed method is compared with that of the Kalman filter (KF) noise reduction method presented in the literature. It is found that the proposed method is simpler and acting as a wider bandwidth de-noising filter than the KF noise reduction method for achieving the same performance.