These notes are derived from a school on low frequency radio astronomy that was held at NCRA, Pune from June 21 to July 17 1999. The school was funded by SERC, DST. Speakers at the school had been asked to provide a set of lecture notes prior to their lectures, and, somewhat to our own surprise, many of them actually did. Our plan had been to compile these notes and, at the end of the school, to issue them in book form.
For various reasons, this didn't happen. The main problem was that while about half of the notes were nicely LaTeXed up with embedded figures, the other half varied enormously in quality. There was everything from half written plain text notes with cut-paste graphics to stapled bundles of xeroxes of the slides used during the lecture. Our editorial burden was hence considerable, and so we are especially glad to find that it is finally over, and that we need no longer feign temporary deafness when the topic of SERC school notes comes up.
But to place the blame where it should rightly be placed, it must be admitted that this all started with our insistence on each speaker preparing a set of notes. There are several excellent books on radio astronomy and interferometry, and the US based NRAO regularly puts out a definitive set of ``Synthesis Imaging'' notes. Why then bother with producing something else? Well we had two major reasons. The first was that excellent though these books and notes may be, many Indian students do not have access to them. On the other hand there was a very clear need for us to have available some pedagogical material that we could freely distribute. The other was that we felt it would be nice to have lecture notes that were specifically focused on what we at the GMRT felt was important to us.
This second fixation of ours has influenced these notes in two ways. The first, more subtle effect, is that we have tried, (where possible), to stress issues that are of concern in low frequency radio astronomy, but which may be less important, or even irrelevant at higher frequencies. The other is that there is an entire section of these notes that is devoted exclusively to describing the GMRT. This section has been written for the more general reader, i.e. one who does not want to wade through arcane technical notes and reports (assuming that s/he is fortunate enough to need information on a topic for which some documentation exists!) to get an overview of the GMRT.
We hope that these notes go someway towards meeting these two aims, and that students of radio astronomy as well as GMRT users and new technical staff will find them useful.
All that remains now is to thank all those who have contributed to this enterprise:- the speakers from the school for writing the notes to start with, the legions of NCRA friends and colleagues who cheerfully proof read various versions, B. Premkumar who made some of the figures and arranged for them to be printed, Annabhat Joshi who designed the cover and helped with getting the final master copy ready for the printer, SERC for funding the school, NCRA for providing financial and other support, and finally, all the project students from the last few years who bugged us for copies of the notes.
We have done our best to eliminate typographical and other errors, but none the less we are sure that several remain, for which we do, of course, admit complete culpability. We would be grateful if readers who notice such errors could bring them to our notice.
Jayaram N Chengalur
K. S. Dwarakanath