Table Of ContentVery Long Baseline Interferometry
Techniques and Applications
NATO ASI Series
Advanced Science Institutes Series
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Series C: Mathematical and Physical Sciences -Vol. 283
Very Long Baseline Interferometry
Techniques and Applications
edited by
Marcello Felli
Arcetri Observatory,
Florence, Italy
and
Ralph E. Spencer
University of Manchester,
Jodrell Bank, U.K.
Kluwer Academic Publishers
Dordrecht / Boston / London
Published in cooperation with NATO Scientific Affairs Division
Proceedings of the NATO Advanced Study Institute on
The Techniques and Applications of Very Long Baseline Interferometry
Castel S. Pietro Terme, Bologna, Italy
September 12-23, 1988
Library of Congress Cataloging In Publication Data
NATO Advanced Study Institute on VLBI (1988 : Bologna, Italy)
Very long baseline interferoNetry techniques and applications
proceedings of the NATO Advanced Study Institute on VLBI, Castel S.
Pietro Terme, Bologna, Italy, 12-23 September, 1988 I edited by
Marcello Felli and Ralph E. Spencer.
p. CM. -- (NATO ASI series. Series C, MatheNatical and
physical sciences; no. 283)
'Published in cooperation with NATO Scientific Affairs Division."
Inc 1u des index.
1. Very long baseline lnterferometry--Congresses. I. Felli,
Marcello. II. Spencer, Ralph E. III. North Atlantic Treaty
Organization. Scientific Affairs Division. IV. Title. V. Series.
QB479.3.N37 1988
522' . 682--dc20 89-15317
ISBN-13: 978-94-010-7595-4 e-ISBN-13: 978-94-009-2428-4
001: 10.1007/978-94-009-2428-4
Published by Kluwer Academic Publishers,
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TABLE OF CONTENTS
Preface ix
List of Participants xi
PART 1
FUNDAMENTAL VLBI TECHNIQUES
1. Basic Radio Astronomy
Bryan Anderson 3
2. Fundamentals of Interferometry
Ralph E. Spencer 11
3. Introduction to VLBI
James M. Moran 27
4. The Effects of Propagation on VLBI Observations
James M. Moran 47
5. Signal Flow at VLBI Antennas
Bryan Anderson 61
6. An Introduction to Closure Phase and Self-Calibration
Peter N. Wilkinson 69
PART 2
VLBI TECHNIQUES IN PRACTICE
7. Scheduling, Correlating and Postprocessing of VLBI
Observations
Walter Aiel 97
8. Calibration Methods
R. Craig Walker 141
VI
9. Sensitivity
R. Craig Walker 163
10. An Introduction to Deconvolution in VLBI
Peter N. Wilkinson 183
11. Mapping in Practice
Lars B. Baath 199
12. Spectral Line VLBI
Philip Diamond 231
13. Introduction to Phase-Reference Mapping
Walter Ale! 261
14. Polarimetry
William Cotton 275
15. Geodesy VLBI Observables
Bernt Ronnang 289
PART 3
SOME RESULTS IN VLBI
16. Geodesy, Geodynamics and Astrometry using VLBI
Bernt Ronnang 305
17. Recent Results in Astronomy I: Extragalactic
Lucia Padrielli 319
18. Recent Results in Astronomy II: Pulsars and Stars
Bryan Anderson 339
19. Recent Results in Astronomy III: Interstellar Masers
Philip Diamond 345
vii
PART 4
THE PRESENT AND FUTURE OF VLBI
20. The European and U.S. VLBI Networks in 1988
Richard T. Schilizzi 357
21. Comparison with other Instruments
Carla Fanti 363
22. VLBI in the 1990's
Richard T. Schilizzi 397
PART 5
CONTRIBUTED PAPERS
List of Contributions 421
APPENDIX
Call for proposals 427
Current Data on Telescopes of the European Network 431
INDEX 435
Preface
The quest for high resolution has preoccupied radio astronomers ever since
radio waves were first detected from space fifty years ago. This venture was par
ticularly stimulated by the discovery of quasars, and led to the development of
interferometer techniques using baselines of transglobal dimensions. These meth
ods have become known as Very Long Baseline Interferometry (VLBI).
Arrays of radio telescopes situated all over the Earth (or even in space) are
regularly used for researches in radio astronomy, reaching resolutions as small as
a fraction of a milli arcsecond. The technique also allows the measurement of the
positions of the radio telescopes to a few millimeters and so VLBI has become a
major tool in geodesy and the study of the rotation of the Earth.
VLBI has now passed the pioneer stage and is becoming a standard facility
available to astronomers and geodesists, requiring the coordination of the operations
of indpendently owned radio telescopes around the world. In Europe observatories
from England, Federal Republic of Germany, France, Italy, Poland, Sweden and
The Netherlands are coordinated in their VLBI activity by the European VLBI
Network Consortium (EVN). The Programme Committee of the EVN allocates
time to scientific projects on a routine basis three times a year. The Unites States
has a similar arrangement of a network of independent radio observatories, and
joint experiments using 'Global Network' are often made.
Despite the enormous progress in the technique over recent years, there is still
a limited number of astronomers using VLBI. The members of the EVN Consortium
felt that a Summer School on VLBI Techniques would be the most appropiate way
to achieve the goal of a wider group of users.
The summer school, sponsored by NATO as an Advanced Study Institute, was
held in Castel S. Pietro Terme on 12-23 September 1988. Lectures were given on
topics ranging from an introduction to the basis of radio astronomy to the more
esoteric aspects of imaging and analysis for geodesy.
These proceedings reflect the fact that the Institute was primarily pedagogical,
its main goal being to provide the non experts with a detailed description of all the
aspects of VLBI, from the basic theory to the details of its application. For the
first time one can find in a single text all the information needed to start from
scratch a new VLBI scientific project. Furthermore, part of the material contained
here has not appeared elsewhere. The reader should note that the lectures were
self-contained and given by separate individuals. With this choice some degree of
repetition was inevitable. However, this was not felt to be educationally detrimental
as repetition with a different slant can improve understanding.
ix
x
In editing we have taken the liberty of rearranging the order in which the talks
were given to give a more structured appearence to the proceedings.
Part 1 contains introductory material, starting with an outline of the basic
priciples of radio astronomy and interferometry followed by a fuller decription of
VLBI. An impromptu talk on signal flow paths in VLBI receiver systems was re
quested by the students and so a written-up version is included here. The section
ends with an introduction to the properties which makes VLBI imaging possible,
that is 'closure'.
Part 2 contains the more detailed aspects of VLBI analysis including a useful
description of how to process VLBI data at the correlator, methods of calibration
and how to make maps. The last few lectures in the section are on the more
advanced analysis topics.
Part 3 summarizes recent results arising from the application of VLBI to
geodesy and extragalactic and galactic astronomy.
Part 4 contains talks on the VLBI networks and radio telescopes currently in
use around the world and ends with a discussion of future plans.
A list of contributed papers is given in Part 5, and finally the Appendix
contains technical information of use to the scientific proposal writer.
The neophyte in VLBI should perhaps read Part 3 first to see how VLBI can
help his/her astronomical researches, followed by Part 1 in order to get a basic
understanding of the technique. Part 4 will tell him/her how to obtain telescope
time, and if succesful the intrepid VLBl's should now tackle Part 2.
The Editors wish to thank the following: the members of the EVN Programme
Committee and the EVN Directors for their continued encouragment, the Local
Organizing Committee for their unstinting efforts before and during the Institute,
the Italian CNR for funds to help with travel for non-NATO partecipants, the
NATO Science Committe of the Advanced Study Institute programme for providing
the means by which the summer school and these proceedings have become possible,
the students for contributing so much to the discussion and last but by no means
least the lecturers for their hard work and dedication throughout the summer school.
Directing the summer school and editing its proceedings was a hard and time
consuming job. If this book will be able to assist newcomers in this field and enlarge
the number of VLBI users we have reached our goal.
Marcello Felli, Arcetri Observatory
~
Ralph E. Spencer, University of Manchester ~
l-J
March, 1989 ::0
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*
Participants
Directors of Institute
Marcello Felli Ralph E. Spencer
Osservatorio di Arcetri University of Manchester
Largo E. Fermi 5 Jodrell Bank
50125, Firenze Macclesfield SKll 9DL
Italy United Kingdom
Local Organizing Committee
Roberto Ambrosini Franco Mantovani
Istituto di Radioastronomia Istituto di Radioastronomia
Via Irnerio 46 Via Irnerio 46
40126 Bologna 40126 Bologna
Italy Italy
Luisa Baldeschi Lucia Padrielli
Istituto di Radioastronomia Istituto di Radioastronomia
Via Irnerio 46 Via Irnerio 46
40126 Bologna 40126 Bologna
Italy Italy
William Junor Paolo Tomasi
Istituto di Radioastronomia Istituto di Radioastronomia
Via Irnerio 46 Via Irnerio 46
40126 Bologna 40126 Bologna
Italy Italy
xi
