Accuracy and Monitoring Improvements From the GPS Legacy Accuracy Improvement Initiative

T. Creel, A.J. Dorsey, P.J. Mendicki, J. Little, R.G. Mach, and B.A. Renfro

Abstract:	The implementation of the GPS Legacy Accuracy Improvement Initiative (L-AII) in Summer 2005 has doubled the amount of data available to the GPS Master Control Station (MCS) by adding data from the National Geospatial-Intelligence Agency (NGA) GPS MSN. The data collected by the two networks, the GPS Operational Control System (OCS) and MSN, are combined at Schriever Air Force Base (AFB) in Colorado Springs, Colorado where command and control of the GPS constellation is executed by the 2nd Space Operations Squadron (2SOPS). Currently, six of the 11 operational NGA monitoring stations are combined with the six OCS stations to double the amount of data used by the MCS Kalman filter. Additionally, in a future Legacy upgrade, the NGA data will be used in the L-band Monitor. Within a year, the remaining 5 NGA monitoring stations will be added, providing triple ground station visibility of every GPS satellite. The improvements for the MCS are threefold, improved accuracy of the Kalman filter state estimates, improved accuracy of the broadcast ephemeris and clock parameters, and improved ability to observe the performance of the GPS space vehicles. The benefits of these improvements apply to all users, military and civilian. This paper will describe the new tracking network configuration, quantify the improvement in monitoring capability, and provide test results on improvements in the accuracy of the filter solutions and the broadcast ephemeris.
Published in:	Proceedings of the 2006 National Technical Meeting of The Institute of Navigation January 18 - 20, 2006 Hyatt Regency Hotel Monterey, CA
Pages:	664 - 684
Cite this article:	Creel, T., Dorsey, A.J., Mendicki, P.J., Little, J., Mach, R.G., Renfro, B.A., "Accuracy and Monitoring Improvements From the GPS Legacy Accuracy Improvement Initiative," Proceedings of the 2006 National Technical Meeting of The Institute of Navigation, Monterey, CA, January 2006, pp. 664-684.
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