Dr David Buscher, Astrophysics Group

Room 918, Rutherford Building, x37302

E-mail: dfb@mrao.cam.ac.uk

Meet to discuss 2:15pm on Tuesday October 22nd in rm 918

1. A laser beacon wavefront sensor for large telescopes (T/C)

Wavefront sensors are a key component of the adaptive optics systems which
are used in large telescopes to correct the image distortions introduced
by the Earth's atmosphere. This project is aimed at testing a new idea in
wavefront sensing (see
http://www.mrao.cam.ac.uk/~dfb/teaching/pt3/pppp.pdf), in which the
intensity of a laser beam propagating upwards from a telescope is used to
derive the distortions experienced by downward-propagating light from
the astronomical object. The principles involved have been analysed using
simple models, but more rigourous analysis is required to prove the
usefulness of the new technique.  The project involves simulating the
propagation of light through multiple atmospheric layers to test the
predictions of the simple theory and to determine the best choice of
experimental parameters. A good understanding of Fresnel and Fraunhofer
diffraction is essential, as are computing skills in Fortran, C or Python.

2. The Part II waveguide experiment enters the 21st century (E)

The waveguide experiment currently offered to Cambridge undergraduates is
based on 1960s equipment which is increasingly hard to maintain. It is
proposed to offer a new experiment in which the microwave waveguides are
replaced with their modern equivalent, single-mode optical fibres. The aim
of the project is to participate in the design of the new experiment and
to carefully test its suitability for part II undergraduates. This project
would suit someone with good experimental skills and an interest in
physics education.

3. Image deconvolution techniques for speckle polarimetry (T/C)

Determining the polarisation of the light emitted from astronomical
sources can yield detailed information about scattering processes in a
wide range of astronomical sources. However, the angular scales on which
objects are most highly polarised can in many cases be far less than the
intrinsic angular resolution limit set by the "blurring" due to the
Earth's atmosphere. Speckle imaging is a long-established technique for
circumventing this blurring, but its application to polarimetry has been
limited. The aim of this project is to test a new method of applying
speckle techniques to polarimetric imaging. The project will involve
numerically simulating the atmospheric blurring process and using
deconvolution techniques to "deblur" the images. If time permits, the
techniques developed in simulation will be used to analyse images of the
dust envelopes surrounding the carbon star IRC+10216. The student
undertaking this project should have a good understanding of Fourier
transforms and be reasonably able in programming in C, Fortran or Python.