GPS Signal Quality Monitoring System

Jock R.I. Christie, Philip B. Bentley, John W. Ciboci, Christian A. Gellrich, J. Mark Gondek, Bruce K. Knoth, Matt B. Ressler and George N. Oetzel

Abstract:	During the past two decades, the Global Positioning System has grown from a nascent military system to the most widely used, accurate, and reliable navigational tool for terrestrial, marine, and aviation use in the world. The U.S. Air Force manages the GPS program and currently supports 29 active GPS satellites, including the 50th GPS satellite, launched on 23 June 2004. The USAF also maintains five GPS monitoring and control stations worldwide that provide operational control but do not include equipment for monitoring modernized signal quality. Since 1997, SRI International has been under contract to support the USAF GPS Joint Program Office by regularly monitoring the L-band transmissions of all newly launched and currently operational GPS satellites. The program goal is to verify that all deployed satellites are consistently and reliably performing according to specification. SRI measures signal power, code delay, frequency content, and bandwidth to verify the proper operation of the satellite constellation. Archived data enables the comparison of multiple data sets SRI is currently upgrading the RF and data-acquisition systems at a 47 m (150 ft) diameter steerable antenna that has been used to collect these measurements. SRI is now testing an automated 3 m (10 ft) antenna and coherent receiver Due to its faster slew rate and automated control, the new system will speed monitoring operations and reduce manpower requirements. SRI’s GPS Calibration and Monitoring System is designed to collect essential state-of-health information on the GPS constellation for the next decade. This information is for use by military personnel operating the system as well as by GPS users and manufacturers.
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:	2239 - 2245
Cite this article:	Christie, Jock R.I., Bentley, Philip B., Ciboci, John W., Gellrich, Christian A., Gondek, J. Mark, Knoth, Bruce K., Ressler, Matt B., Oetzel, George N., "GPS Signal Quality Monitoring System," 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. 2239-2245.
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