Geo uplink subsystem (GUS) clock steering algorithms performances, validation, and test results

摘要

Raytheon systems company is currently designing the algorithms of the FAA's Area Augmetnation system (WAAS). This paper will discuss the GUS clock steering performance, validation, and test results. The clock steering algorithms reside in the GEO Uplink Subsystem processor. The WAAS Type 9 messages (GEO Navigation message), which are used as inputs to the GUS WAAS Message Processor, are provided by the Wide Area Master Station (WMS). The GUS calculates clock adjustments and tunes the local frequency standard to speed up or slow the GUS clock. The GUS cesium standard is controlled through very small frequency control signals so that the normal operation of the code and frequency control loops of the downlink signals will not be disturbed. Test results for the primary and backup GUS are discussed in the paper. The typical tracking error results are within +-250 ns (excluding the effects of GEO maneuvers and GUS or WMS switchovers) for the primary GUS using INMARSAT's Atlantic Ocean Region-West (AOR-W) GEO satellite. For the AOR-W backup GUS, the system settled to +-550 ns. The typical tracking error results for the primary GUS using INMARSAT's Pacific Ocean Region (POR) GeO satellite are within +-450 ns (excluding the effects of GEO maneuvers, and GUS or WMS switchovers). For POR's backup GUS, the system settled to +-550 ns.