Lockheed Martin Wide Area Differential GNSS Testbed Results

Henry Beisner, Art Gower, Tim Parker and Jack Rudd

Abstract:	Lockheed Martin Federal Systems (LMFS), known as Loral Federal Systems prior to being purchased by Lockheed Martin in 1996, and known as IBM Federal Systems prior to being purchased by the Loral Corp. in 1994, has been the prime GPS Operational Control Segment (OCS) contractor since 1980. LMFS was responsible for the procurement ‘and integration of the GPS Monitor Stations and Ground Antennas. LMFS designed and implemented the majority of software in the GPS Master Control Station, including the Kalman filter that is utilized to estimate and predict the GPS satellite clocks and orbits. LMFS designed and implemented the soflware necessary to format these predictions into the GPS navigation message. LMFS has recently completed upgrades to the OCS in support of the new Block IIR satellites. As a part of the GPS OCS support contract LMFS will evolve the entire control segment from a centralized host-based system to an open workstation-based distributed architecture. This wealth of knowledge and experience with the estimation and prediction of satellite orbits and clocks, as well as the design and development of the GPS OCS, has provided a solid foundation for developing a wide area differential correction GPS navigation system. It is this core of knowledge and experience that has fueled the Independent Research and Development (IRAD) program for the LMFS Wide Area Differential Global Navigation Satellite System (GNSS) testbed. The GNSS IRAD program has three goals: 1) validate the design and accuracy of our algorithms, 2) ensure that the corrections may be continuously determined in real time, and 3) demonstrate that the accuracy achieved, when applying these corrections, exceeds the requirements for Category I Precision Approach (CAT-I). All three of these goals have been achieved and repeatedly demonstrated in our Wide Area Differential GNSS Testbed. This paper will describe the results obtained using the testbed from two perspectives. First, an analysis of the Service Volume is presented for locating the testbed monitoring sites. This analysis uses the LMFS Service Volume Model (SVM), a high fidelity covariance-based analysis tool used to determine user obtainable navigation accuracy and service availability. As a second perspective, this paper presents actual results obtained when using the Wide Area Differential GNSS Testbed. The testbed consists of 5 GPS monitoring sites including a central processing capability all located in the Eastern portion of the United States. The results represent both temporal and spatial tests and comparisons are made to the results predicted by the SVM.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	799 - 811
Cite this article:	Beisner, Henry, Gower, Art, Parker, Tim, Rudd, Jack, "Lockheed Martin Wide Area Differential GNSS Testbed Results," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 799-811.
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