MPhys Physics

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Radio Astronomy

**Pre-requisite compulsory module- PHYS30392 Cosmology: If students have not completed Cosmology but are still interested in the module, please contact the unit coordinator for consideration.

**Pre-requisite - PHYS30141 Electromagnetic Radiation or PHYS30441 Electrodynamics (M): Students must take at least one of these two units.

1. To provide an overview of phenomena which can be studied with radio techniques including a range of non-astronomical applications.
2. To introduce the techniques of radio astronomy, from antennas to radio receivers, emphasising their strengths and limitations and the applicability of these techniques to a range of non-astronomical applications.

On completion successful students will be able to:

1. Relate radio-waveband observations of astrophysical objects to the mechanism that generated the emission.

2. Explain how radio waves are affected as they travel through the interstellar medium and the Earth’s atmosphere.

3. Calculate key performance indicators of a radio telescope such as its sensitivity and angular resolution.

4. Assess the optimum choice of receiver system for a desired radio astronomical measurement.

5. Describe the operation and advantages of radio interferometers in imaging applications.

1. Fundamentals
The radio universe: “hidden” objects (pulsars, double radio sources, OH/IR stars etc) and a new light on the familiar (e.g. HII regions, supernova remnants, spiral galaxies).
Brightness, flux density and brightness temperature, emission mechanisms, thermal and synchrotron continuum radiation, spectral lines, simple radiative transfer, antenna characteristics.

2.   Antenna concepts
The antenna as an aperture; Rayleigh distance; far-field Fourier transform relations and differences for the near field; effective area, aperture efficiency; beam solid angles and antenna gain; antenna temperature; Ruze formula; Wiener-Kinchine theorem, convolution and antenna smoothing; parabolic antennas and basics of quasi-optics.

3.   Receiver concepts
Johnson noise; Nyquist theorem and noise temperature, band-limited noise, minimum detectable signal, noise accounting in receivers; heterodyne systems and sidebands; polarization sensitive receivers; gain instabilities; Dicke-switched and correlation receivers.
Spectral line receiver concept: detectability of spectral lines, filter bank, autocorrelation and Fourier transform receiver principles.
Interferometric receiver concepts; spatial and temporal coherence; adding, phase switching and multiplying types; resolution; complex visibilities; aperture synthesis and imaging of various targets.

4.   Case Studies
Application of radio astronomy techniques to specific astrophysical targets e.g. discrete source surveys; the Cosmic Microwave Background; mm-wave imaging of Earth from space; mm-wave imaging of terrestrial targets for all-weather surveillance and security.

Feedback will be available on students' individual written solutions to examples sheets, and model answers will be issued for the weekly example sheets, as well as weekly

Recommended texts
Rohlfs, K. and Wilson, T.L. Tools of Radio Astronomy, 3rd ed (Springer-Verlag 2000)
Further texts
An Introduction to Radio Astronomy" Burke, Graham-Smith, Wilkinson, 4th ed (CUP 2019)
Kraus, J. Radio Astronomy, (McGraw-Hill 1986)