LAAS Ground Facility Design Improvements to Meet Proposed Requirements for Category II/III Operations

Sam Pullen, Ming Luo, Gang Xie, Jiyun Lee, R. Eric Phelts, Dennis Akos and Per Enge

Abstract:	Stanford University has developed a Local Area Augmentation System (LAAS) ground facility prototype known as the Integrity Monitor Testbed (IMT) to demonstrate the feasibility of LAAS precision approaches under Category I conditions. While the Category I IMT is essentially complete, research on IMT algorithms continues to improve its performance so that it can eventually meet Category II/III approach requirements. To the extent possible, it is desirable to satisfy Category II/III requirements with modifications to the existing single-frequency (L1) LAAS architecture in order to provide Category II/III initial operational capability (IOC) before the second civil frequency (L5) is present on a sufficient number of GPS satellites. This will also provide a backup operational mode in a future dual- frequency LAAS if either L1 or L5 is interfered with. This paper addresses IMT improvements to detection of satellite signal deformation, code-carrier divergence monitoring of both potential satellite failures and ionosphere spatial anomalies, and position-error monitoring at a “remote” monitor receiver that is some distance away from the existing reference receiver antennas. With these relatively-limited modifications to the existing Category I LGF architecture, significant performance improvements are demonstrated. While the degree to which these improvements are sufficient depends on changes now being considered to the Category II/III requirements, we believe that, with further refinement, they will be sufficient to provide acceptable IOC and dual-frequency backup availability.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	1934 - 1947
Cite this article:	Pullen, Sam, Luo, Ming, Xie, Gang, Lee, Jiyun, Phelts, R. Eric, Akos, Dennis, Enge, Per, "LAAS Ground Facility Design Improvements to Meet Proposed Requirements for Category II/III Operations," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 1934-1947.
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