Claycomb James R. - Radio astronomy

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Original title and copyright: Basic Techniques of Radio Astronomy. Copyright 2012 by Overseas Press India Pvt Ltd. All rights reserved.

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S. Joardar and J. R. Claycomb. Radio Astronomy.
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PREFACE

PREFACE TO THIS EDITION

This edition of Basic Techniques of Radio Astronomy has been supplemented with context-connection boxes, including NASAs Deep Space Network (DSN), the South Pole Telescope (SPT), the Low-Frequency Array (LOFAR), Space Very Long Baseline Interferometry (VLBI), pulsar dispersion and distance, and plane waves in conducting and dielectric media. Three appendices have been added on radiation potential formalism, the physics of radio spectral lines, and a table of world radio observatories. Several problems have been added to emphasize the physical aspects of radio astronomy. Supplementary materials and all textbook figures are included on the companion disc.

James R. Claycomb
Houston, TX
MARCH, 2014

PREFACE TO THE ORIGINAL EDITION

This book is based on my lectures on the subject of radio astronomy and techniques delivered at various places including the GMRT. It is designed from the point of view of a large audience consisting of persons who are associated with radio astronomy. They include (i) students, (ii) astronomers, (iii) engineers, and (iv) academicians. The book begins with the foundation of radio astronomy and then goes on to explain the fundamentals, polarization, designing radio telescopes, understanding radio arrays, interferometers, receiving systems, mapping techniques, image processing, and propagation effects, all in relation to radio astronomy. A special chapter at the end presents the GMRT radio array as an example of these techniques. For the benefit of students, two additional chapters have been added as appendices. They describe the coordinate systems used in radio astronomy and the essential aspects of antenna theory. It is advisable to go through the first two appendices together with the first chapter. The review questions at the end of each chapter contain direct hints for easy solutions. For constructing radio images from interferometer data, readers are advised to freely download the relevant software from the NRAO website. Although AIPS is popularly used, I encourage students to use CASAPY, which is based on python scripts. Tutorials for software operation are also available for free download. In either case, the system requirement is Linux, preferably Fedora Core, Ubuntu, or Debian. The bibliography at the end lists only published materials. Materials that are available free on the Internet have also been cited. I am thankful to the entire radio astronomical community, whose direct or indirect contributions have helped in the completion of this work. I express my special thanks towards them. Finally, I give my best wishes to the audience. If anyone benefits from this work, I shall consider my efforts as both successful and rewarded. The inspiration behind this work came from my Gurudev Ananta Sri Baba, and I dedicate this work to Him.

S. Joardar
Pune, India
March, 2012

CHAPTER 1

FOUNDATIONS OF RADIO ASTRONOMY

Radio astronomy studies the Universe at radio frequencies. It analyzes the radio signals received from distant objects in the Universe.

The radio astronomical signals may be categorized regionally as follows:

(i) Our solar system consists of the Sun, planets and their satellites, comets, asteroids, and the interplanetary medium. Strong transient radio signals reach us from the Sun and Jupiter. Relatively weak continuum radio signals from the Sun as a black body also reach us. The distance from the Sun to Earth is 150,000,000 km, which is 1 AU (astronomical unit). The solar system is a part of the galaxy in which we live, known as the