HANDBOOK SATELLITE TIME AND FREQUENCY TRANSFER AND DISSEMINATION SATELLITE TIME AND FREQUENCY TRANSFER AND DISSEMINATION SATELLITE OOK ANDB H Printed in Switzerland Geneva, 2010 Edition 2010 Photo credits : www.itu.int Radiocommunication Bureau HANDBOOK SATELLITE TIME AND FREQUENCY TRANSFER AND DISSEMINATION Edition 2010 Radiocommunication Bureau THE RADIOCOMMUNICATION SECTOR OF ITU The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Inquiries about radiocommunication matters Please contact: ITU Radiocommunication Bureau Place des Nations CH -1211 Geneva 20 Switzerland Telephone: +41 22 730 5800 Fax: +41 22 730 5785 E-mail: [email protected] Web: www.itu.int/itu-r Placing orders for ITU publications Please note that orders cannot be taken over the telephone. They should be sent by fax or e-mail. ITU Sales and Marketing Division Place des Nations CH -1211 Geneva 20 Switzerland Fax: +41 22 730 5194 E-mail: [email protected] The Electronic Bookshop of ITU: www.itu.int/publications ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Satellite Time and Frequency Transfer and Dissemination iii PREFACE Technological development in general, and that of information-communication technologies and applications in particular, requires the increasingly precise timing and synchronization of different electronic devices. The International Telecommunication Union carries out studies and establishes international standards on the relevant timing scales and their use by telecommunication and computer networks, electronic navigation systems, and so forth. In 1974, the International Radio Consultative Committee (CCIR – Comité Consultatif International des Radiocommunications), in cooperation with the General Conference of Weights and Measures and the Bureau International de l’Heure, developed Coordinated Universal Time (UTC). In 1978, CCIR approved the use of UTC “to designate the time in all international telecommunication activities and in all official documents of the International Telecommunication Union”. CCIR also stated that UTC should be employed “as the ultimate reference for standard-frequency emissions”. The ITU World Administrative Radio Conference 1979 (WARC-79) included UTC in the international treaty status Radio Regulations, and since then UTC has been used as the main time-scale for telecommunication networks (wired and wireless) and for other time-related applications. Modern satellite systems providing time and frequency signal dissemination through a clear, un-obstructed path with an easily modelled delay are the main source of precise time and frequency so essential to maritime and aviation services, navigation and positioning systems and for the proper functioning of telecommunication and computer networks. This is the first ITU Handbook to provide detailed information on the applied methods, technologies, algorithms, data structure and practical use of frequency and timing signals provided by satellite systems. Special attention is focused on the Global Navigation Satellite Systems (GNSSs) belonging to the radionavigation-satellite service. GNSS are providing time-frequency signals to any place on the Earth and currently represent the de-facto primary source of precise timing signals for governmental, commercial, transportation and scientific applications. Dr. Valery TIMOFEEV Director Radiocommunication Bureau Satellite Time and Frequency Transfer and Dissemination v TABLE OF CONTENTS Page PREFACE ............................................................................................................................................ iii FOREWORD ........................................................................................................................................ vii ACKNOWLEDGEMENTS ................................................................................................................. ix INTRODUCTION ................................................................................................................................ xi CHAPTER 1 – SATELLITES AND TIME AND FREQUENCY TRANSFER AND DISSEMINATION .................................................................................................................. 1 CHAPTER 2 – GLOBAL POSITIONING SYSTEM .......................................................................... 7 CHAPTER 3 – SATELLITE BASED AUGMENTATION SYSTEM TO GPS ................................. 21 CHAPTER 4 – GPS SYSTEM TIME .................................................................................................. 45 CHAPTER 5 – GLONASS NAVIGATION SATELLITE SYSTEM ................................................. 51 CHAPTER 6 – COMMUNICATION SATELLITE SYSTEMS ......................................................... 67 CHAPTER 7 – TIME SCALES ........................................................................................................... 73 CHAPTER 8 – NATIONAL TIMING CENTRES .............................................................................. 89 CHAPTER 9 – RELATIVISTIC EFFECTS IN SATELLITE TIME AND FREQUENCY TRANSFER AND DISSEMINATION ................................................................................... 95 CHAPTER 10 – EARTH ORIENTATION AND GEODETIC SYSTEM .......................................... 121 CHAPTER 11 – PROPAGATION AND ENVIRONMENTAL FACTORS ....................................... 131 CHAPTER 12 – GLOBAL NAVIGATIONAL SATELLITE SYSTEMS – AS A PRIMARY TOOL FOR TIME TRANSFER .............................................................................................. 141 CHAPTER 13 – GEODETIC TECHNIQUES USING GPS PHASE AND CODE MEASUREMENTS ................................................................................................................. 157 CHAPTER 14 – TWO WAY SATELLITE TIME AND FREQUENCY TRANSFER (TWSTFT) ... 185 CHAPTER 15 – SUMMARY TIME AND FREQUENCY DISSEMINATION ................................. 197 Satellite Time and Frequency Transfer and Dissemination vii FOREWORD The Radiocommunication Study Group 7 for the Science Services (SG 7) was created through a structural reorganization in 1990 at the Düsseldorf CCIR Plenary Assembly. At that time, the Space Research and Radio Astronomy Study Group (SG 2) was consolidated with the Time and Frequency Standards SG 7 to form the new SG 7 on Science Services. Many of the activities in the Science Services Study Group are associated with advancing the state of the art in the use of the radio spectrum to achieve scientific objectives. In this regard, the time and frequency standards community has long been associated with the International Telecommunication Union (ITU) with the express purpose of developing Recommendations for the use of the radio spectrum to facilitate the dissemination of precise time references and for standardizing the methods for this dissemination. An essential corollary is the specification of precise frequency standards and the techniques for their implementation. The Radiocommunications Sector SG 7 (Science Services) comprises 4 Radiocommunication Working Parties (WPs) that addresses technical issues related to specific disciplines under the umbrella of science services. Working Party 7A, (Time Signals and Frequency Standards Emissions) is concerned with the generation and dissemination of Time and Frequency Signals by terrestrial and space radiocommunication services. In the past 15 to 20 years the precise time and frequency services provided by satellite systems, predominately navigation satellites, have become the primary means of dissemination and the capabilities of those services has increased dramatically. The resulting increase in capability and development of these satellite systems has made it difficult to keep pace with their development, their impact on the Time and Frequency Community and the Radio and Telecommunication communities in general. This Handbook provides comprehensive technical and operational information on current satellite systems employed for dissemination of precise time and frequency signals. As Chairman of SG 7, it is my great pleasure to present this Handbook to the above-mentioned communities of users, who will, I am sure, find it an important reference tool in their own work. This Handbook is the result of several years of preparation and work to attempt to capture the development in satellite technologies and the growing capability they have produced. The Handbook could not have been completed without the contributions from many administrations participating in SG 7 and its WP 7A. Special thanks should be given to the Chairmen of WP 7A Mr. Ronald BEARD, for his leadership of this project. Our special gratitude is also due to Mr. A. VASSILIEV of the Radiocommunication Bureau who has played an important role in the preparation, editing and publication of the Handbook. Satellite Time and Frequency Transfer and Dissemination ix ACKNOWLEDGEMENTS The work of the Rapporteurs for the various sections of the Handbook was outstanding and we would like to express