THE EVOLUTION OF SYNCHRONIZATION IN THE WORLD-WIDE OMEGA NAVIGATION SYSTEM

V. Vannicola and H. McManus

Abstract:	If the accuracy of the Omega Navigation System were to be limited at all times solely by unpredictable propagation disturbances, the relative timing with which the signals are transmitted must be controlled to an accuracy of less than 0.5 micro seconds. Tests of VLF signal transmissions over long distances have established that the timing stability of such signals will exceed one microsecond for at least some period of time. Prior to 1972 the Naval Electronic Laboratory Center (NELC) now the Naval Ocean System Center (NOSC) was the synchronization control center for Omega and made the necessary calculations and adjustments using reciprocal path measurements. However, without external measurements the mean system "walked" from Coordinated Universal Time (UTC). After the U.S. Coast Guard and the Japanese Maritime Safety Agency (JMSA) became responsible for the synchronization of the Omega system a more sophisticated technique was developed. This method still relied on a reciprocal path technique, but also included a statistical Alter which tracked each cesium frequency standard at the transmitting stations and computed optimal phase adjustments based on internal path measurements. In 1977 with seven of the eight network stations on-line, external measurement source such as LORAN-C and portable clock measurements tied the Omega system to UTC time. In November 1985 Global Positioning System (GPS) data from Omega station Liberia was used for the first time as an external input to the existing Synchronization software package. By carly 1987 GPS monitor receivers were installed at all the Omega Transmitting Stations. In 1988 data from the transmitting stations in the southern hemisphere was used to remove a 2-3 microsecond bias which greatly improved the synchronization throughout the Worldwide Omega Navigation System.
Published in:	Proceedings of the 20th Annual Precise Time and Time Interval Systems and Applications Meeting November 29 - 1, 1988 Sheraton Premiere Hotel Vienna, Virginia
Pages:	133 - 144
Cite this article:	Vannicola, V., McManus, H., "THE EVOLUTION OF SYNCHRONIZATION IN THE WORLD-WIDE OMEGA NAVIGATION SYSTEM," Proceedings of the 20th Annual Precise Time and Time Interval Systems and Applications Meeting, Vienna, Virginia, November 1988, pp. 133-144.
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