Timing Calibration of the Northeast U.S.A. LORAN-C Chain(9960)

The U.S. Naval Observatory (USNO), from the very first day of its establishment in 1830 as a chronometer rating office, to the present, has been deeply involved in the specialized field of Precise Time and Time Interval (PTTI). During this period of one and one half centuries, the accuracy specification that defines Precise Time and Time Interval, or (PTTI), has monotonically increased from seconds to nanoseconds! The 1- second-PTTI era began in the early 1860's, when Western Union adopted USNO's 1 sec PTTI, which event led to the defacto use of Standard Time in most parts of the world in 1904, Naval Radio Station NAA in Arlington, Virginia, began the first radio time transmissions of USNO's PTTI; and this event introduced the era of 0.001 sec PTTI. In May 1961, upon the delivery of LORAN-C timing receivers built to specification for the purpose, USNO began providing steering and control of the East Coast LORAN-C; and this event began the era of dissemination of 1 microsecond PTTI (Currently, USNO's involvement with the Global Positioning System (GPS) is introducing the era of 1 nanosecond PTTI. Although dissemination of 1 nanosecond PTTI is clearly dependent on the implementation of OPS, USNO still continues to publish 1 microsecond PTTI values UTC(USNO MC) - LORAN-C (Ref 1). This year is the twenty-fifth year of the US involvement in the use of LORAN-C to disseminate 1 microsecond PTTI. The published values disseminated, however, are based upon a variety of instruments, receivers, PTTI substations, as well as various direct and indirect measurement techniques. Over a period of several years, it is possible that, unless field check are made, changes in instrumentation, receiver delays, re-configurations of LOPAN-C chains, etc., Pub. in the Proceedings of the Eighteenth Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting Held 2-4 Dec 1986 in Washington, DC.