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Evaluation of Error Sources For Galileo Test Bed Satellites through Measurement Campaign

This thesis is motivated by the increasing interest on the performance of GALILEO, the future European Global Navigation Satellite System. The GALILEO program is being carried out in different phases: GALILEO System Test Bed (GSTB), In-Orbit Validation (IOV) and Full Operation Capability (FOC). Among the aims of GSTB phase, the testing of in-orbit payload technology for experimental satellites, i.e. GIOVE-A and GIOVE-B, is critical. In this thesis work, navigation signals have been processed with the scope to assess navigation antenna characteristics as function of elevation and azimuth angles. GIOVE-A and GIOVE-B signals have been collected by Thales Alenia Space-Italia Signal Monitoring Laboratory Facility (SMLF) during 4 months of planned Signal In Space (SIS) monitoring to satisfactorily characterize navigation antenna patterns with measurements.
In particular, satellite antenna characteristics have been evaluated considering the Phase Center Variations-related effects (PCVs), with an appropriate linear combination of observables, and C/N0 measurements. The phase center is the point with respect to which the geometrical distance between satellite antenna and receiving antenna is computed. PCVs represent a relevant error source in satellite-to-receiver distance computation when extremely high precision is required for the calculation of user position. PCVs are motivated by the fact that the equiphase wavefront of the transmitting antenna is not perfectly spherical, as it should be in theory, so the location of the center of the equiphase surface is different for each elevation and azimuth angles pair. Moreover, because the phase center for GALILEO navigation antennas, which use phased¬-array technology, are related to the geometry of the array and signals at different frequencies are not transmitted using the same radiating elements, PCVs are also dependent on the signal frequency.
The symmetry of PCVs and C/N0 parameters for GIOVE-A and GIOVE-B navigation antennas has been analyzed to assess which navigation antenna has a better behavior, with the purpose to understand which one should be used for GALILEO satellites that will be part of the IOV and FOC phases.

Mostra/Nascondi contenuto.
15 Introduction Robust and reliable navigation is a key factor for every GNSS related application, especially with respect to safety critical ones that rise stringent requirements on modernization of existing and future navigation systems. The modernization of existing satellites navigation systems like GPS and GLONASS, and the construction of new ones such as GALILEO are a result of this trend and need. The development and operation of a reliable GNSS system requires a detailed quality assessment and verification of any of its components on ground and also in space. This implies continuous analyses, verification and monitoring of the navigation system performance. The purpose of this thesis work is to analyze some performance of the experimental satellites of GALILEO navigation systems, i.e. GIOVE-A and GIOVE-B. In detail, effects depending on elevation and azimuth angles are evaluated. One reason for those elevation and azimuth dependent effects traces back to the satellite antenna which emits the navigation signals to Earth and the associated coupling networks which connect the antenna to the navigation payload. Therefore the characterization of the satellite in detail is crucial. Among these effects, Phase Center Variations (PCVs) have been considered with an appropriate linear combination of observables, and the power of broadcasted signals has been verified evaluating C/N 0 measurements. The phase center is the point with respect to which the geometrical distance between satellite antenna and receiving antenna is computed. PCV represents a relevant error source in satellite-to-receiver distance computation when extremely high precision is required for the calculation of user position, because it is in the order of magnitude of some centimeters. PCVs are motivated by the fact that the equiphase wavefront of the transmitting antenna is not perfectly spherical, as it should be in theory, so the location of the center of the equiphase surface is different for each elevation and azimuth angles pair. Moreover, because the phase center for GALILEO

Laurea liv.II (specialistica)

Facoltà: Ingegneria

Autore: Mattia Boccuni Contatta »

Composta da 224 pagine.

 

Questa tesi ha raggiunto 92 click dal 16/12/2011.

 

Consultata integralmente una volta.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.