Astronomy 345 Instrumentation
IOR1: Radio Telescopes

Prof. G. Woan

Here we concentrate on the non-optical side of astronomical instrumentation.  In particular, we consider the methods and techniques used in radio astronomy, taking the student through many of the major topics in this broad field, from antenna theory to the search for extraterrestrial intelligence (SETI). 

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Course details

Introduction to radio astronomy:  Revision of fundamentals.  Flux density and sky 'brightness'.  Blackbody radiation and effective temperature.  The Rayleigh-Jeans Law.  Energy received from an extended source.  Examples of radio sources.
lecture notes:  1 2 3 4 5 6 7 8 9

[ Parkes | Lovell | Arecibo | GBT | Effelsberg | J-VLA | eMERLIN | LOFAR | SKA | ALMAPlanck  ]

[ Cygnus A | Herclues A | Cassiopeia A | eg 3C61.1 3C75 | galactic centre | radar | 408 MHz sky | Polarized emission from galactic dist  | CMBR  | spectropscopy  lines ]

Antennas and noise:   Antenna power patterns and beams. Effective area and aperture efficiency. Antennas as resistances and Nyquist's Theorem. Antenna temperature and its relationship to sky brightness temperature. Antenna directivity and gain.  The Reciprocity Theorem.

lecture notes:  1 2 3 4 5 6 6a 7 8 9 10

[atmospheric window and solar spectrum antennas summaryantenna beam patterns ]

Types of antennas: dipoles and horns.   Cassegrain feeds.  Effects of surface irregularities.  Simple antenna arrays (discrete and continuous).  Fourier transform relationships.
lecture notes:  1 2 3 4 5 6 7 89

Radio telescope receivers:   The design of a "total power" radio telescope.  Mixing, filtering and square-law detection.  Minimum detectable temperature and flux density.  System temperature.  The equation of radio astronomy.  Beam chopping.
lecture notes:  1 2 3 4 5 6 7 8 9 10 11 12

waveforms and spectra |  simulations | the radiometer equation]

Interferometry and coherence:  The need for resolution.  Coherence, complex fringe visibility and the van Cittert-Zernike Theorem.  Fourier transforms and the (u,v) plane.  Phase-switched interferometer and  digital correlation interferometer.  VLBI, GPS and the use of interferometers in geodesy.
lecture notes:  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

interferometry summary |  simulations | fourier transforms]

Aperture synthesis:  Imaging interferometers.  Path compensation and fringe stopping. Earth rotation aperture synthesis.  (u,v) plane coverage and the idea of image reconstruction. The VLA and MERLIN as examples.
lecture notes:  1 2 3 4 5 6 7 8 9 10

[ MERLIN, VLA and VLBAimage reconstruction, ]

SETI:  Design considerations and principles behind the search for extraterrestrial intelligence. Bandwidth and sensitivity constraints.
lecture notes:  1 2 3 4 5 6

Cosmic rays:  Synchrotron radiation. The connection between power-law radio spectra and cosmic rays.
lecture notes:  1 2 3 4 5 6

cosmic ray energy spectrum |galactic radio synchrotron spectrum
comparison of predicted and observed radio spectra

Question Sheets


The following books cover all or some of the course well, and you may find it useful to consult them in the library:

Further reading: A graduate-level summer school on radio astronomical imaging is held regularly at the VLA. The slides from a recent meeting can be found here, and earlier ones here.  Another nice course, which starts with the basics, is here.