The Interesting Navstar Satellite SVN-49

Karl Kovach and Thomas Powell

Abstract:	The Navstar satellite known as SVN-49 (also known as IIR-20 and currently broadcasting as PRN-01 in the GPS constellation) is affected by a problem that causes spurious transmissions in the L1 and L2 bands. The spurious transmissions are similar, but not identical, to multipath signals with amplitudes that vary as a function of the user viewing angle. This paper begins with an overview of the problem which caused SVN-49 to be affected by the spurious transmissions. The effect of the spurious transmissions is then compared and contrasted with the broadcast signalin- space (SIS) requirements defined in the governing Interface Specification (IS-GPS-200), the Precise Positioning Service Performance Standard (PPS PS) and the Standard Positioning Service Performance Standard (SPS PS). Although most SIS requirements are satisfied by SVN-49, it does fail to comply in one important specification. Since there is no way to eliminate the problem, SVN-49 will continue to present its affected L1 and L2 SIS to users for its entire operational lifetime. Several potential mitigation methods have been studied which can minimize the effect of the spurious transmissions on GPS users. The mitigation methods are described in this paper along with an assessment of the related pros and cons. The rationale behind the selected set of mitigation methods planned for implementation is examined and explained in terms of the good of the many outweighing the good of the few. The paper concludes with a possible, but as yet undecided, deployment schedule for the selected set of mitigation methods.
Published in:	Proceedings of the 2010 International Technical Meeting of The Institute of Navigation January 25 - 27, 2010 Catamaran Resort Hotel San Diego, CA
Pages:	952 - 962
Cite this article:	Kovach, Karl, Powell, Thomas, "The Interesting Navstar Satellite SVN-49," Proceedings of the 2010 International Technical Meeting of The Institute of Navigation, San Diego, CA, January 2010, pp. 952-962.
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