Timing Experiments with Global Navigation Satellite System Clocks

The science of timekeeping is crucial in many dierent applications around the world. One of the most signicative applications in which time and frequency metrology has an essential role are Global Navigation Satellite Systems (GNSS). Any satellite navigation system indeed, is based on the transmission of signals from a constellation of satellites: processing these signals it is possible to estimate the position of a user, provided that the time of transmission is indicated with extremely high accuracy. In fact, being the distance measured from a time, any error in the measure of time will be directly mapped into an error in the user position, which has to be kept below its specied limits. The positioning accuracy is widely determined by the clocks quality. It is why all the satellites need to y very accurate atomic clocks: fundamental for their excellent stability. An agreement between the European Community and the European Space Agency (ESA) gave rise to a new European satellite system: Galileo. The Istituto Nazionale di Ricerca Metrologica (INRiM) is deeply involved in the Galileo project, mainly concerning the activities related to the experimental phases, such as the generation of an experimental reference time scale for the system and the metrological characterization of atomic clocks employed onboard satellites. This thesis will describe the timing experiments carried out in these years of doctorate with GNSS clocks, both with space and ground clocks, within the experimental phases of the Galileo projec