Astronomy 345 Instrumentation
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
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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.
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.
[atmospheric window and solar spectrum | antennas summary | antenna beam patterns ]
Types of antennas: dipoles and horns. Cassegrain feeds. Effects of surface irregularities. Simple antenna arrays (discrete and continuous). Fourier transform relationships.
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.
[ 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.
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.
[ MERLIN, VLA and VLBA | image reconstruction, ]
SETI: Design considerations and principles behind the search for extraterrestrial intelligence. Bandwidth and sensitivity constraints.
Cosmic rays: Synchrotron radiation. The connection between power-law radio spectra and cosmic rays.
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.