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Edition of 2013 HANDBOOK ON RADIO ASTRONOMY International Telecommunication Union Sales and Marketing Division Place des Nations *38650* CH-1211 Geneva 20 Switzerland Fax: +41 22 730 5194 Printed in Switzerland Tel.: +41 22 730 6141 Geneva, 2013 E-mail: [email protected] ISBN: 978-92-61-14481-4 Edition of 2013 Web: www.itu.int/publications Photo credit: ATCA David Smyth HANDBOOK ON RADIO ASTRONOMY Radiocommunication Bureau Handbook on Radio Astronomy Third Edition EDITION OF 2013 RADIOCOMMUNICATION BUREAU Cover photo: Six identical 22-m antennas make up CSIRO's Australia Telescope Compact Array, an earth-rotation synthesis telescope located at the Paul Wild Observatory. Credit: David Smyth. ITU 2013 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. - iii - Introduction to the third edition by the Chairman of ITU-R Working Party 7D (Radio Astronomy) It is an honour and privilege to present the third edition of the Handbook – Radio Astronomy, and I do so with great pleasure. The Handbook is not intended as a source book on radio astronomy, but is concerned principally with those aspects of radio astronomy that are relevant to frequency coordination, that is, the management of radio spectrum usage in order to minimize interference between radiocommunication services. Radio astronomy does not involve the transmission of radiowaves in the frequency bands allocated for its operation, and cannot cause harmful interference to other services. On the other hand, the received cosmic signals are usually extremely weak, and transmissions of other services can interfere with such signals. In twelve chapters and five Appendices, the Handbook introduces the reader to radio astronomy viewed as a radiocommunication service for the purpose of frequency coordination. It starts with a preamble on radio astronomy and society, outlining the role and benefits of radio astronomy to society, often extending beyond astronomy. The Handbook then covers areas such as the characteristics of radio astronomy, preferred frequency bands for observations, special radio astronomy applications, vulnerability to radio frequency interference (RFI) from other services, and issues associated with sharing the radio spectrum with other services. Additional chapters have been included in this third edition of the Handbook on techniques for mitigating the effects of RFI, on the establishment and characteristics of Radio Quiet Zones (RQZ), on the searches for extraterrestrial intelligence (SETI) and on ground-based radar astronomy. New Appendices have been added to explain the use of units and the dB scale in radio astronomy, and an extensive list of acronyms. Almost ten years have passed since the second edition of the Handbook – Radio Astronomy was published. In the meantime ITU has held three World Radiocommunication Conferences (WRC-2003, WRC-2007 and WRC-2012). In this period, there has been a virtual explosion in the development of communication services, and wireless services are now all pervasive in our multi-connected society. In parallel, technological developments in radio astronomy have enabled observations over very wide frequency bands, often not covered by the ITU allocations. Such developments present a challenge for the protection of radio astronomy and new methods had to be explored. New techniques on RFI mitigation are under continuous development, and RQZ have been defined to provide unique places on the planet where radio astronomy can proceed with minimal interference. Such developments have been covered within ITU with new and extensive ITU-R Reports. Radio astronomy is now also operating in bands above 275 GHz, with the ALMA observatory in South America, which commenced operations in 2013. These bands are not covered by the formal ITU allocations, but WRC-2012 clarified the usage of such bands by the passive services without precluding the development of active services. Studies have shown that sharing between services would be relatively easy at such high frequencies. Just before WRC-2012, ITU-R Working Party 7D (WP 7D) started to revise the Handbook, and this work continued over two years. WP 7D is the section within ITU-R Study Group 7 (Science services) that is responsible for radio astronomy, SETI, and radar astronomy. In parallel with the necessary revision and expansion of the Handbook, WP 7D had to revise relevant ITU-R Recommendations and Reports to protect the radio astronomy service. The third edition of the Handbook successfully incorporates the results of these efforts by the Working Party members. Radio Astronomy Introduction - iv - I wish to acknowledge the considerable effort of a small group of people without whose involvement the Handbook could not have materialized. I am particularly indebted to the following WP 7D members (in alphabetical order): – Dr. W. Baan (Netherlands), Dr. S. H. Chung (Korea), Dr. A. Clegg (United States of America), – Dr. M. Davis (United States of America), Dr. T. Gergely (United States of America), Dr. A. Jessner (Germany), – Dr. G. Langston (United States of America), Dr. B. Lewis (United States of America), Dr. H. Liszt (United States of America), – Dr. M. Ohishi (Japan), Dr. P. Thomasson (United Kingdom), Dr. W. van Driel (France). Other contributors were: Dr. J. Romney from USA, who extensively re-wrote the sections on very long baseline interferometry (VLBI), Dr. J. Lovell from Australia for the section on geodetic VLBI, and Dr. K. Tapping (Canada) for revising the section on solar astronomy. The ITU-R Secretariat provided considerable help and in particular the Study Group 7 Counsellor Mr. Vadim Nozdrin and the Secretariat led by Mrs. Elizabeth Mostyn-Jones. Finally I would like to express my sincere appreciation to the Chairman of Study Group 7, Dr. Vincent Meens and the vice-Chair responsible for the Handbooks Dr. John Zuzek, for their continuing encouragement and support during this work. I thank all contributors and wish the ITU-R Handbook – Radio Astronomy every success. Anastasios Tzioumis Chairman, ITU-R Working Party 7D Introduction Radio Astronomy - v - PREFACE The Handbook on Radio Astronomy has been developed by experts of Working Party 7D of ITU-R Study Group 7 (Science services), under the chairmanship of Dr. A. Tzioumis (Australia), Chairman, Working Party 7D. Radio astronomy plays a key role in the study of problems in fundamental physics and cosmology. Many of the phenomena studied cannot be studied in other parts of the electromagnetic spectrum. To cite but a few examples: the emission line of neutral atomic hydrogen; cosmic microwave background radiation and its angular structure, which is of immense significance in cosmology; the huge regions of synchrotron radiation associated with radio galaxies; and regions of star formation that are hidden by dust in optical frequencies. Using radio frequencies, it is possible to achieve the highest angular resolution and the most precise measurement of angular positions and of spectral lines and their Doppler shifts. For this reason, radio astronomy, far from being a mere adjunct to traditional optical methods, plays a leading role in research carried out in many areas of astronomy and astrophysics. Apart from this, radio astronomy, like any fundamental science, stimulates development in other branches. It is to radio astronomy that we owe the development of low-noise receivers and antennas that enable us to use a single antenna to capture signals of differing polarisations. Methods developed in radio astronomy to combat radio echo are now being used successfully in WiFi-type mobile communication systems. The foundations of radionavigation theory that are used today in a range of systems were developed and confirmed in radio astronomy. The need to process huge quantities of data in radio astronomy has resulted in major improvements in automated data processing, including the development of methods for parallel data processing and new programming languages. In the medical sphere, radio astronomy has led to the introduction of X-ray diagnostics and computerized tomography. All the above indicate the importance of the international recognition and protection of spectrum used by radioastronomy. This Handbook gives the reader a very useful source of information relevant to the management of radio spectrum usage in order to minimize the interference caused to this valuable service. François Rancy Director Radiocommunication Bureau Radio Astronomy Preface - vii - TABLE OF CONTENTS Page Introduction to the third edition by the Chairman of ITU-R Working Party 7D (Radio Astronomy) ..... iii PREFACE ......................................................................................................................................... v PREAMBLE Radio Astronomy and Society ......................................................................................... 1 0.1 Introduction to astronomy ..................................................................................................... 1 0.2 The role of radio astronomy .................................................................................................. 1 0.3 Economic and societal value ................................................................................................. 4 0.3.1 Introduction ................................................................................................................ 4 0.3.2 Economic and societal value of radio astronomy research ........................................
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