Providing a Resilient Timing and UTC Service Using eLoran in the United States

Gerard Offermans, Steve Bartlett, Chuck Schue

Abstract:	Accurate timing and frequency is becoming increasingly important in many applications that influence our daily life. Fifteen out of sixteen sectors of the Critical Infrastructure and Key Resources (CIKR) identified by the Department of Homeland Security Department of Homeland Security (DHS) Science and Technology Directorate (S&T) use GPS for timing and for eleven it is deemed essential. More and more systems are becoming solely dependent on GPS or other Global Navigation Satellite System (GNSS) for their precise position, timing, and frequency information, especially as additional multi-constellation GNSS, i.e. Galileo, Compass, and GLONASS, and Regional Navigation Satellite Systems (RNSS) become fully operational and “fill the world’s skies.” Along with the explosive growth of systems and applications comes an increasing awareness of GNSS vulnerabilities. Interference, jamming and spoofing reduce availability and reliability of all GNSS. National Security Presidential Directive-39 (NSPD-39) of 2004 established implementation actions for the development of a back-up system to GPS for positioning and timing. In July 2015, a Congressional Hearing was held to discuss the Federal Radionavigation Plan. Chairman Duncan Hunter (R, CA) opened the hearing by saying that the government had been studying the issue of a backup for GPS for 11 years and that it was time for action. Congressman Garamendi (D, CA) added that there was “real time”, like what GPS and eLoran provide, and "federal time" which is the model of comparison Congress uses when trying to get a decision or something done. Both Congressmen made it clear, quoting Dr. Brad Parkinson, that there is a need for a back-up to GPS and that eLoran is the prime candidate to do so. In June 2015, Congressman LoBiondo (R, NJ) turned on the eLoran transmitter at the former US Coast Guard Loran Support Unit site in Wildwood, NJ, thereby initiating a Cooperative Research and Development Agreement (CRADA) between the DHS S&T, the Coast Guard, Exelis, and UrsaNav to demonstrate eLoran’s capability to provide accurate time and frequency over a wide area. eLoran is a high power, Low Frequency (LF), ground wave radio broadcast system, capable of providing 10-meter positioning accuracy, Stratum-1 frequency distribution, and Universal Time Coordinated (UTC) timing well within one microsecond (µs) across very large areas(1,000 miles). Application of differential corrections for timing further improve the accuracy to better than 100 nanoseconds (ns). eLoran is proven technology, well-established for providing services very similar to those delivered by GNSS, with characteristics and failure modes that are complementary to GNSS. This paper discusses the general concept of eLoran timing and UTC distribution, and the current prototype service. It further highlights plans to provide an initial four-station CONUS-wide timing service, which can gradually be expanded to provide increased coverage and redundancy and deeper penetration into buildings. Additional stations also enable positioning and navigation services.
Published in:	Proceedings of the 47th Annual Precise Time and Time Interval Systems and Applications Meeting January 25 - 28, 2016 Hyatt Regency Monterey Monterey, California
Pages:	121 - 131
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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