Accession Number : ADP009098

Title :   Loran-C Time Management,

Corporate Author : COAST GUARD WASHINGTON DC RADIONAVIGATION DIV

Personal Author(s) : Justice, Charles ; Mason, Norm ; Taggart, Doug

Report Date : 02 DEC 1993

Pagination or Media Count : 13

Abstract : As of October 1, 1993, the U.S. Coast Guard (USCG) supports and operates fifteen Loran-C chains. With the introduction of the Global Positioning System (GPS) and the termination of the Department of Defense (DOD) overseas need for Loran-C, the USCG will cease operating the three remaining overseas chains by December 31, 1994. Following this date, the USCG Loran-C system will consist of twelve chains. Since 1971, management of time synchronization of the Loran-C system has been conducted under a Memorandum of Agreement between the U.S. Naval Observatory (USNO) and the USCG. The requirement to maintain synchronization with Coordinated Universal Time (UTC) was initially specified as + or - 25 microseconds. This tolerance was rapidly lowered to + or - 2.5 microseconds in 1974. To manage this synchronization requirement, the USCG incorporated administrative practices which kept the USNO appraised of all aspects of the master timing path. This included procedures for responding to timing path failures, timing adjustments and time steps. Conducting these aspects of time synchronization depended on message traffic between the various master stations and the USNO. To determine clock adjustment, the USCG relied upon the USNO's Series 4 and 100 updates so that the characteristics of the master clock could be plotted and controls appropriately applied. In 1987, Public Law 100-223, under the Airport and Airway Improvement Act Amendment, reduced the synchronization tolerance to approximately 100 nanoseconds (ns) for chains serving the National Airspace System (NAS). This action caused changes in the previous administrative procedures and techniques. This paper presents the actions taken by the USCG to meet the requirements of this law.

Descriptors :   *GLOBAL POSITIONING SYSTEM, *LORAN, *TECHNOLOGY FORECASTING, *COMPARISON, CONTROL, OBSERVATORIES, OVERSEAS, REQUIREMENTS, STATIONS, TIME, COAST GUARD OPERATIONS, SYSTEMS MANAGEMENT.

Subject Categories : Navigation and Guidance

Distribution Statement : APPROVED FOR PUBLIC RELEASE