Reconstructing antenna gain patterns of Galileo satellites for signal power monitoring

Monitoring the quality of global navigation satellite system (GNSS) signals is of primary importance for a variety of applications requiring high levels of robustness, reliability and integrity. A key element in the signal quality verification is the evaluation of the available power at the user location, including its spatial characteristics. As such, the expected performance of the GNSS satellite antenna is, for most applications, assumed as nominal. However, due to a variety of reasons such as degradation due to heavy strains during launch as well as space environment factors, it is possible that the GNSS satellite antennas exhibit non-nominal performance in the transmitted power. An analysis and evaluation of the navigation signal quality require the investigation of such cases. To this end, this study describes a methodology for the estimation and reconstruction of non-absolute GNSS satellite antenna gain patterns, focusing on satellites of the Galileo navigation system. A key feature of the presented strategy is the employed setup of reduced complexity, which includes a low-gain antenna that allows monitoring signals from several navigation satellites at the same time. The results obtained pave the way for future multi-satellite, multi-constellation analyses of transmitted signal power, which may significantly support safety-critical applications. Additionally, the presented methodology may serve as the basis for the reconstruction of absolute antenna gain patterns, which are of particular interest for GNSS reflectometry applications.