INTERNATIONAL UNION UNION OF RADIO-SCIENTIFIQUE RADIO SCIENCE INTERNATIONALE ISSN 1024-4530 Bulletin No 322 September 2007 Radio Science Publié avec laide financière de lICSU URSI, c/o Ghent University (INTEC) St.-Pietersnieuwstraat 41, B-9000 Gent (Belgium) The Contents Editorial .......................................................................................................................3 URSI News................................................................................................................... 4 Radio-Frequency Interference Mitigation in Radio Astronomy ............................ 9 Propagation of Current Waves Along Quasi-Periodic Thin-Wire Structures: Taking Radiation Losses into Account................................................................ 19 Radio-Frequency Radiation Safety and Health ..................................................... 41 Exposure of Dairy Cattle to Fields Associated with 735 kV AC Transmission Lines Conferences ............................................................................................................... 44 News from the URSI Community ........................................................................... 59 Information for authors ........................................................................................... 61 Front cover: Radio-astronomy images of an area of the sky containing a few weak point sources. The image on the left is the raw, unfiltered data. It is so comtaminated by radio-frequency interference (RFI) that only the interference can be seen. The image on the right shows the point sources as concentric circles, visible after RFI-mitigation filtering techniques have been applied. A reduction by two orders of magnitude in the rms noise of the unfiltered data has been achieved. See the paper by M. Kesteven. EDITOR-IN-CHIEF EDITORIAL ADVISORY BOARD EDITOR URSI Secretary General François Lefeuvre W. Ross Stone Paul Lagasse (URSI President) 840 Armada Terrace Dept. of Information TechnologyW. Ross Stone San Diego, CA92106 Ghent University PRODUCTION EDITORS USA St. Pietersnieuwstraat 41 Inge Heleu Tel: +1 (619) 222-1915 B-9000 Gent Inge Lievens Fax: +1 (619) 222-1606 Belgium SENIOR ASSOCIATE EDITOR E-mail: [email protected] Tel.: (32) 9-264 33 20 J. Volakis Fax : (32) 9-264 42 88 P. Wilkinson (RRS) E-mail: [email protected] ASSOCIATE EDITOR FOR ABSTRACTS P. Watson ASSOCIATE EDITORS For information, please contact : P. Banerjee (Com. A) K.L. Langenberg (Com. B) The URSI Secretariat M. Chandra (Com. F) R.P. Norris (Com. J) c/o Ghent University (INTEC) C. Christopoulos (Com. E) T. Ohira (Com. C) Sint-Pietersnieuwstraat 41, B-9000 Gent, Belgium G. DInzeo (Com. K) Y. Omura (Com. H) Tel.: (32) 9-264 33 20, Fax: (32) 9-264 42 88 E-mail: [email protected] I. Glover (Com. F) M.T. Rietveld (Com. G) http://www.ursi.org F.X. Kaertner (Com. D) S. Tedjini (Com. D) The International Union of Radio Science (URSI) is a foundation Union (1919) of the International Council of Scientific Unions as direct and immediate successor of the Commission Internationale de Télégraphie Sans Fil which dates from 1913. Unless marked otherwise, all material in this issue is under copyright © 2007 by Radio Science Press, Belgium, acting as agent and trustee for the International Union of Radio Science (URSI). All rights reserved. Radio science researchers and instructors are permitted to copy, for non-commercial use without fee and with credit to the source, material covered by such (URSI) copyright. Permission to use author-copyrighted material must be obtained from the authors concerned. The articles published in the Radio Science Bulletin reflect the authors opinions and are published as presented. Their inclusion in this publication does not necessarily constitute endorsement by the publisher. Neither URSI, nor Radio Science Press, nor its contributors accept liability for errors or consequential damages. 2 The Radio Science Bulletin No 322 (September 2007) Editorial It is with great sadness that I report that Tkachenko, have included a fair amount of as this issue was going to press, we learned of review and tutorial information in this paper, the death on September 3, 2007, of Dr. A. P. in order to make it adequately self-contained Mitra. Dr. Mitra was an outstanding radio to be easily read. However, there are two scientist, and a true champion of radio science. elements that differentiate the results presented He spent much of his career fostering and in this paper. First, the structures considered enabling radio science in developing countries, are quasi-periodic: they are periodic structures and helping younger radio scientists. Of course, consisting of a finite number of identical he was a past President of URSI and an Honorary sections, rather than being infinite. Second, President of URSI. We will have a proper the treatment in this paper specifically includes remembrance of Dr. Mitras life and work in a the effects of losses, including those due to subsequent issue. radiation, ohmic losses, and dielectric losses. The approach used is to generalize the Full-Wave Our Papers Transmission-Line Theory (FWTL) to include losses. The authors are able to derive analytical expressions for the global parameters of the FWTL, and to thereby reduce the In his invited Review of Radio Science paper from equations to a second-order differential equation that is Commission J, Michael Kesteven reviews the status of similar to the Schrödinger equation. This both permits well- techniques for mitigating radio-frequency interference (RFI) established mathematical methods to be used to obtain for radio astronomy. There are two simple reasons why solutions, and also allows some interesting parallels to such mitigation is needed. First, radio-astronomy techniques quantum-mechanical systems to be drawn. The authors have become much more sensitive over time. Second, the then use this theory to analyze propagation along quasi- amount of RFI present in the environment has dramatically periodic wiring structures. This leads to a number of increased with time. The latter is due both to the tremendous interesting results, including an investigation of allowed increase in the number of devices using wireless and forbidden frequency zones associated with such communications, and to the amount and portions of the structures. A numerical example is presented to illustrate spectrum used by these devices. several of the effects. The paper first looks at the effects of RIF on radio In his Radio-Frequency Radiation Safety and Health astronomy, and points out that there are some self-mitigating column, Jim Lin looks at some interesting new results factors associated with the nature of the data and the data- related to the effects of electric, magnetic, and combined processing algorithms used in radio astronomy. The paper fields associated with high-voltage power-transmission lines then takes an in-depth look at proactive RIF mitigation on dairy cattle. There definitely appear to be effects. strategies. These include regulation, the establishment of However, it is unclear if these effects can be separately radio quiet zones, and controlling the observatory associated with electric fields or magnetic fields. It is environment. Reactive mitigation techniques are interesting that some of the effects appear to be beneficial. subsequently considered. These include an array of methods associated with recording and processing the radio- We Need Your Papers! astronomy data. The paper concludes with an examination of approaches that should be considered for next-generation radio telescopes. We continue to have good input of Reviews of Radio Science papers from many of the URSI Commissions, and The efforts of Ray Norris, the Associate Editor for we will be bringing you the papers associated with the Commission J, and Phil Wilkinson in bringing us this paper Tutorial and General Lectures from the General Assembly. are gratefully acknowledged. However, in the last few months we have seen a reduction in the number of submitted papers. Please consider Our second paper is an interesting examination of the submitting a paper to the Radio Science Bulletin. If you propagation of current along quasi-periodic thin-wire have a paper on a topic that is likely to be of interest to radio structures. Such structures play several important roles in scientists in general, this Bulletin is an excellent method of electromagnetics. They can be used to build antennas and reaching them. We are able to publish papers with no delay filters, and very-high-power short-pulse sources for other than the time required for peer review (and any applications such as high-power microwave devices. Such resulting revision), and we have no page charges. Our periodic transmission-line structures are also used to design papers are also abstracted and indexed in INSPEC, so your metamaterials. The authors, Jürgen Nitsch and Sergey paper should be found by anyone searching within the field. The Radio Science Bulletin No 322 (September 2007) 3 If you have a paper, please send it to me (submission as a http://www.ece.uic.edu/2008ursiga PDF for review purposes is fine). If you hear an interesting presentation at a conference that you think would make a All radio scientists are welcome to submit papers to the good contribution to the Bulletin, please urge the author to General Assembly. This is your once-every-three-year submit it to the Bulletin. chance to share your work with the preeminent radio scientists from all over the world. Also,