Prototype Test Results of L1/L5 Signals of Future GEO Satellites

Po-Hsin Hsu, Laura Cheung and Mohinder Grewal

Abstract:	The Wide-area Augmentation System (WAAS) uses Geostationary Earth Orbit (GEO) satellites to relay correction and integrity information to users. A secondary use of the GEO signal is to provide users with a GPS-like ranging source. The ranging signal is generated on the ground and provided via C-Band uplink to the GEO, where the navigation payload translates the uplinked signal to an L1 downlink frequency. The GEO incorporates an additional C-Band downlink to provide ionospheric delay observations to the GEO uplink ground station. The GEO Communication and Control Segment (GCCS) will add new L1/L5 GEOs and ground stations to WAAS. A key feature of GCCS is the addition of a second independently generated and controlled uplink signal. In contrast to WAAS, which uplinks and controls a single CBand signal, GCCS uplinks two independent C-Band signals, which are translated to L1 and L5 downlink signals. Closed loop control of the GEO’s L1 and L5 broadcast signals-in-space is necessary to ensure that the algorithms compensate for the code carrier divergence of the uplink signal due to the ionospheric effect, uplink Doppler, and divergence due to carrier frequency translation errors induced by the GEO’s transponder. Use of two independent broadcast signals creates unique challenges in estimating biases and maintaining coherency between the two signals. This paper presents laboratory test results which show that simulated uplink effects were compensated by the L1 and L5 control loop algorithms.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	1359 - 1366
Cite this article:	Hsu, Po-Hsin, Cheung, Laura, Grewal, Mohinder, "Prototype Test Results of L1/L5 Signals of Future GEO Satellites," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 1359-1366.
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