NANU Analysis for 2007 Through 2015

John W. Lavrakas

Abstract: This paper documents the behaviors of NANUs over a nine year time period, from 2007 through 2015 and the findings from this work, identifying issues in the way NANUs are implemented and highlighting progress made in minimizing errors. The GPS program uses Notice: Advisory to Navstar User (NANU) as one means to notify GPS users of current, impending, and past outages in GPS service. It has pro-vided NANUs for two and a half decades, and these are codified in memorandums of understanding between the US Department of Defense and Department of Transpor-tation as a means to report to GPS users status infor-mation regarding satellites and overall GPS system opera-tion. The most frequent use of NANUs is to report when satellites are removed from service, but NANUs are also used to report system tests, pending leap second adjust-ments, and PRN assignments. Today a robust standard for issuing NANUs is available in the form of ICD-GPS-240, which documents the format and protocols for issu-ing NANUs. By and large, NANUs are generated by the U.S. Air Force 2nd Space Operations Squadron (2 SOPS) any time day and night with dependability and accuracy. The statistics bear this out. Although much automation has been inserted into the process over the years to reduce the likelihood of errors, the process of generating NANUs is largely operator-driven and mistakes are occasionally made. Civil users and their missions depend on NANUs and their quality. In 2009 John Wilde from DW International gave a presenta-tion on “the Impact of NANUs on RAIM Prediction” at CGSIC [Ref 3], in which he identified problems with NANUs, the impact on their Receiver Autonomous Integ-rity Monitoring (RAIM) Prediction services, and recom-mended actions to take. Over the past six years, about three percent of NANUs were issued in error. The types of errors made ranges widely from issuing the wrong NANU types and times to issuing NANUs when not expected.
Published in: Proceedings of the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2016)
September 12 - 16, 2016
Oregon Convention Center
Portland, Oregon
Pages: 2878 - 2886
Cite this article: Lavrakas, John W., "NANU Analysis for 2007 Through 2015," Proceedings of the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2016), Portland, Oregon, September 2016, pp. 2878-2886.
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