The Galileo Mission Segment (GMS) requires high quality pseudorange, carrier phase, signal quality, and status information to perform the tasks of orbit synchronization, integrity processing and precise time determination for the Galileo GNSS. The provision of these measurements for all signals, with the exception of the Public Regulated Service (PRS), is managed by the NonPRS Galileo Receiver Chain (GRCN). The GRCN development is currently being undertaken by an industrial consortium consisting of Thales Alenia Space Italia (TAS-I), NovAtel, Space Engineering (SPENG) and IAI/Accubeat. The GRCN is designed to fulfill very demanding reliability, safety, and performance specifications. Important considerations include performance in interference and ionospheric scintillation, and exploitation of the receiver's fixed position and high performance clock. A unique data interface has been defined given the permanent installation and "always on" nature of the receiver. Considerable attention has also been given to various time transfer modes, including setting time using Galileo measurements, time aiding from GPS during in-orbit validation, and time transfer within the Precise Timing Facility (PTF). The GRCN development is progressing through the critical design phase and integration of the first V1a prototypes hardware and software. This paper provides a summary of the GRCN current state of design, including the overall architecture and specific GRCN features. Reference is made to previously published papers on the GRCN project development at ION-GNSS 2006, ION-GNSS 2007 and ENC 2007.
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