» UMTB STATES APARTMENT Of NBS TECHNICAL NOTE 649 COMMERCE PUBLICATION THE STANDARDS OF TIME AND FREQUENCY NATIONAL BUREAU OF STANDARDS The National Bureau of Standards' was established by an act of Congress March 3. 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end. the Bureau conducts research and provides: (Da basis for the Nation's physical measurement system. (2) scientific and technological services for industry and government. (3 ) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Institute for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Meas- urement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heal — Optical Physics — Nuclear " " :: Sciences — Applied Radiation — Quantum Electronics — Electromagnetics ' — Time and Frequency" — Laboratory Astrophysics : — Cryogenics''. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government agencies; and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor Radiation — Physical Chemistry. THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute consists of a Center for Building Technology and the following divisions and offices: Engineering and Product Standards — Weights and Measures — Invention and Innova- tion — Product Evaluation Technology — Electronic Technology — Technical Analysis — Measurement Engineering — Structures, Materials, and Life Safety' — Building Environment ' — Technical Evaluation and Application ' — Fire Technology. THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effec- tiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Institute consists ol the following divisions: Computer Services — Systems and Software — Computer Systems Engineering — Informa- tion Technology. THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of the Federal Government: promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum accessibility to the scientific information of the world. The Office consists of the following organizational units: Office of Standard Reference Data — Office of Information Activities — Office of Technical Publications — Library — Office of International Relations. 1 Headquarters and Laboratories at Gaithershurg, Maryland, unless otherwise noted; mailing address Washington. D.C. 20234. ,J Part of the Center for Radiation Research. ' Located at Boulder. Colorado 80302. 4 Part of the Center for Building Technology. THE STANDARDS OF TIME AND FREQUENCY IN THE U.S.A. ++ James A. Barnes and G.M.R. Winkler "t" Time and Frequency Division Institute for Basic Standards National Bureau of Standards Boulder, Colorado 80302 T Time Service Division U.S. Naval Observatory Washington, D.C. 20390 IT This publication was also published as Chapter 11 of Time and Frequency: Theory and Fundamentals, NBS Monograph 140 „<.*< or 1* U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary NATIONAL BUREAU OF STANDARDS. Richard W Roberts Director Issued February 1974 National Bureau of Standards Technical Note 649 Nat. Bur. Stand. (1. S.). Tech. Note 649. 91 pages February 1974) CODEN: NBT1NAE For sale by the Superintendent ol Documents. U.S. Government Printing Office, Washington. D. C. 20402 (Order by SD Catalog No. C13.46:649) 81.00 . CONTENTS Page 1 INTRODUCTION 1 2 TIME SCALES - TERMS OF REFERENCE 1 2.1. Compromise Time Scales 3 3. TIME AND FREQUENCY (T&F) ACTIVITIES OF THE NATIONAL BUREAU OF STANDARDS AND THE U. S. NAVAL OBSERVATORY 4 3.1. The Formal Missions of the T&F Activities of the NBS and USNO 4 a. T&F Activites of NBS 4 b. The Position of the U. S. Naval Observatory in the Federal Government 6 3.2. T&F Activities of NEE and the USNO Compared 9 3.3. Coordination of T&F 9 4. INTERNATIONAL ORGANIZATIONS INVOLVED IN STANDARD TIME AND FREQUENCY 12 4.1. Organization of the Treaty of the Meter (Standards) 12 4.2. Scientific Organizations 15 4.3. International Radio Consultative Committee (CCIR) (Regulatory). 15 5. THE LEGAL DEFINITION OF "STANDARD TIME" 15 6. SUMMARY 18 7. REFERENCES 18 APPENDIX A. NBS Enabling Legislation 21 APPENDIX B. USNO Authorizing Documents 37 APPENDIX C. NBS Time and Frequency Responsibilities 45 APPENDIX D. USNO' Precise Time and Time Interval (PTTI) Responsibilities 46 APPENDIX E. NBS/USNO Time Coordination/Services 57 APPENDIX F. Treaty of the Meter 62 APPENDIX G. Legal Documents Concerning "Standard Time" 65 LIST OF FIGURES Page Figure 1. The Time and Frequency Division of the NBS 5 Figure 2. The USNO Time Service Division 8 Figure 3. NBS, USNO, and BIH Interactions 10 Figure 4. Time Scales in the United States of America 13 Figure 5. International Organizations Involved with Standard Frequency and Time 14 Figure 6 . Time Zones of the United States of America 17 LIST OF TABLES Table 1. Time and Frequency Responsibilities of NBS/USNO 11 Table 2. Abbreviations of International Organizations 16 ,. THE STANDARDS OF TIME AMD FREQUENCY IN THE U.S.A. J. A. Barnes and G.M.R. V?inkler This paper describes the national responsibilities for standards of time and frequency in the U.S.A. The National Bureau of Standards (NBS) and the U. S. Naval Observatory (USNO) are the two organizations chiefly involved in distributing accurate and precise time and frequency informa- tion within the U.S.A. The NBS is responsible for the "custody, mainte- nance, and development of the national standards" of frequency and time (interval) as well as their dissemination to the general public. The mission of the USNO includes the "provision of accurate time" for elec- tronic navigation systems, communication, and space technology. This is an integral part of its work concerned with the publication of ephemerides which are used in support of navigation and in the establishment of a fundamental reference system in space. Both agencies provide the U. S. contribution to the Bureau Inter- national de l'Heure (BIH) [International Time Bureau], which has the responsibility of publishing definitive values of Universal Time (UT) International Atomic Time (TAI), and Coordinated Universal Time (UTC) Key words: Astronomical time measurements; clock synchronization; clocks; Coordinated Universal Time (UTC); frequency; frequency standards; International Atomic Time (TAI) ; International Radio Consultative Com- mittee (CCIR) ; International Scientific Radio Union (URSI) ; International Time Bureau (BIH); international time organizations; leap seconds; national time/frequency standards; MBS time and frequency; Precise Time and Time Interval (PTTI) ; time; time coordination; time interval; time scales; Treaty of the Meter (standards); U.S.A. standard time zones; USNO time and frequency. 1 . INTRODUCTION The national responsibilities for the provision of standards of time and frequency (T&F) in the U.S.A. rests with two organizations of widely different background, profes- sional traditions, and outlook (NBS enabling legislation and USNO authorizing documents (app. A and B) ) . The measurement of T&F permeates all scientific observations. It- is fundamental to any system of measurement standards, and it is an indispensable element in -fundamental astronomy, geodesy, and navigation. It follows from this wide range of applications and interfaces with all disciplines of science and technology that requirements for standards of T&F can only be satisfied in some form of compromise. A short discussion of principles and terminology,