Abstract
The importance of having high levels of reliability in Global Navigation Satellite Systems (GNSS) signals has increased gradually in recent years. Among other factors, evaluating the available power and its spatial characteristics at the user location is a key task as part of signal quality verification processes. Due to a diversity of factors, the transmitting antennas of GNSS satellites may exhibit a non-nominal on-orbit performance. As a result, the effective isotropically radiated power of navigation signals may be affected, e.g., due to azimuthal asymmetries in the antenna gain pattern. If not analyzed and handled properly, such irregularities may lead to the use of weak signals from a given satellite, possibly resulting in non-admissible positioning errors. The present contribution aims at the analysis of the on-orbit performance of GNSS satellite antennas, using data from the Galileo system as a case study. Employing reconstructed gain patterns, a set of metrics is defined, which intend being used as performance evaluation values. In addition, the concept of antenna performance stability is explored by analyzing changes over time of reconstructed gain patterns. Results using data from the operational Galileo satellites (up to the beginning of 2019) have been obtained. From the computed example reconstructed patterns, gain variations below 0.5 dB and azimuthal asymmetries at the 0.6 dB level (95%) were found for most of the analyzed satellites. Likewise, the obtained results suggest the occurrence of an event that altered the nominal performance of the antenna of Galileo satellite 0102 during the first years of operation. The presented tools and results may be of particular interest for applications requiring navigation signal power monitoring tasks, such as GNSS reflectometry or safety–critical systems.
Published Version
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