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The Allan variance (AVAR) is widely used to measure the stability of experimental time series. Specifically, AVAR is commonly used in space applications such as monitoring the clocks of the global navigation satellite systems (GNSSs). In these applications, the experimental data present some peculiar aspects which are not generally encountered when the measurements are carried out in a laboratory...
In Global Navigation Satellite Systems (GNSS) the role of atomic clocks is essential for the determination of the user position. Nowadays, several satellite navigation systems are operating and different clock technologies have been employed on board satellites, taking benefit of the improvements reached during the last tens of years. The analysis of GNSS clock performance is thus crucial for ensuring...
Atomic clocks are fundamental elements of a Global Navigation Satellite System (GNSS). Currently, several GNSSs are operational and the different clock technologies employed onboard their satellites benefit from the technological improvements achieved during the last decades. To ensure the timing capabilities needed for correct positioning, the analysis of GNSS clock performances is essential. We...
In Global Navigation Satellite Systems (GNSS) the role of atomic clocks is essential for the determination of the user position and due to their excellent stability they are fundamental to ensure the adequate performances required in the positioning service. Since a degradation of the clock stability would immediately impact the navigation performances, the on board clock behaviour has to be continuously...
GIOVE satellites broadcast currently a clock model in the navigation message which targets a maximum one day validity time. The associated accuracy is limited by the inadequacy of the model to the clock drift for the RAFS and to the presence of harmonics in the phase. The perform ance maybe increased by optimizing the fitting intervals and including an additional harmonic term in the clock model estimation...
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